Physical and chemical evolution of dissolved organic matter across the ablation season on a glacier in the central Tibet Plateau

NASA Astrophysics Data System (ADS)

Feng, L.; An, Y.; Xu, J.; Kang, S.; Xiaofei, L.

2017-12-01

The physical evolution (metamorphism) of snow is known to affect the chemical composition of dissolved organic matter (DOM) within it. Here we present a comprehensive study on the Dongkemadi glacier in the central Tibetan Plateau by collecting surface snow/ice samples from May to October 2015. The samples were grouped into four categories based on their physical descriptions, representing the different stages of the snowmelt (i.e., fresh snow, fine firn, coarse firn, and glacier ice). The concentrations of dissolved organic carbon (DOC) decreased from fresh snow (26.8 μmol L-1) to fine firn (15.0 μmol L-1) and enriched from fine firn to coarse firn (26.1 μmol L-1) and glacier ice (34.4 μmol L-1). This reflected the dynamic variation of DOC during the snowmelt. Excitation emission matrix fluorescence with parallel factor analysis (EEM-PARAFAC) identified three protein-like components (C1, C2 and C4) and one microbial humic-like component (C3), which indicated a significant microbially derived DOM in the surface snow/ice. Molecular level composition of DOM identified by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) also shown newly produced molecular during the snowmelt. These results suggest that the snowmelt could not only induce a loss of DOM but also intensified the in situ microbial activities that enriched and modified it. These findings are important in understanding the evolution of the physical and chemical characteristics of the DOM during the ablation season and shed some light on the nature of the biogeochemical cycles in cryospheric regions.

[Effect of Charge-Transfer Complex on Ultraviolet-Visible (UV-Vis) Absorption Property of Chromophoric Dissolved Organic Matter (CDOM) in Waters of Typical Water-Level Fluctuation Zones of the Three Gorges Reservoir Areas].

PubMed

Jiang, Tao; Liang, Jian; Zhang, Mu-xue; Wang, Ding-yong; Wei, Shi-qiang; Lu, Song

2016-02-15

As an important fraction of dissolved organic matter (DOM), chromophoric dissolved organic matter (CDOM) plays a key role in decision of the optical properties and photogeochemistry of DOM, and further affects pollutant fate and global carbon cycle. These optical properties are ascribed to two chromophoric systems including superposition of individual chromophores and charge-transfer (CT) complexation between electron donor (e.g., phenols and indoles) and acceptor (e.g., quinones and other oxidized aromatics) in DOM structures. Thus in this study, based on the "double-chromophoric system" model, DOM samples from four typical water-level fluctuation zones of Three Gorges Reservoir (TGR) areas were selected, to investigate the effect and contribution of charge-transfer complex to ultraviolet-visible (UV-Vis) absorption property of CDOM. Using NaBH, reduction method, original featureless absorption curve was classified into two independent curves caused by individual chromophoric group, which were derived from a simple superposition of independent chromophore and charge-transfer complex, respectively. Also, the changes in curve properties and specific parameters before and after NaBH4 reduction were compared. The results showed that in all DOM samples from the four sites of TGR, more than 35% of absorption was attributed from CT complex. Shibaozhai of Zhongxian and Zhenxi of Fuling showed the highest proportion ( > 50%). It suggested that the role of CT complex in CDOM property could not be neglected. After removal of CT complex, absorption curve showed blue-shift and CDOM concentration [a (355)] decreased significantly. Meanwhile, because of deforming of bonds by reduction, DOM structures became more dispersive and the molecular size was decreased, resulting in the lower spectral slope (S) observed, which evidentially supported that the supermolecular association structure of DOM was self-assembled through CT complex. Meanwhile, deceasing hydrophobic components led to decreased apparent aromaticity (lower SUVA values), whereas specific parameters including SUVA, CDOM and SR still were applicable for comparison among different DOM samples instead of the same sample without consideration of "double-cbromopboric system" model involving tbe role of CT complex. Comparatively, S(275-295) was dynamic due to tbe impact of CT effect. Furtbermore, establisbing DOC estimation model by short-wavelength range of CDOM was recommended because of its stability despite of CT complex.

Thermal history of type 3 chondrites from the Antarctic meteorite collection determined by Raman spectroscopy of their polyaromatic carbonaceous matter

NASA Astrophysics Data System (ADS)

Bonal, Lydie; Quirico, Eric; Flandinet, Laurène; Montagnac, Gilles

2016-09-01

This paper is focused on the characterization of the thermal history of 151 CV, CO and unequilibrated ordinary chondrites (UOCs) from the NASA Antarctic meteorite collection, using an approach based on the structure of the included polyaromatic carbonaceous matter determined by Raman spectroscopy. 114 out of these 151 chondrites provided Raman spectra of carbonaceous matter and allowing to assign a petrologic type, which mostly reflects the peak temperature experienced by the rock on the parent body. A thorough review of literature shows however that it is not possible to deduce a peak temperature because accurate calibration is not available. Twenty-three new weakly metamorphosed chondrites have been identified: MIL 07671 (CV3.1); DOM 08006 (CO3.0); DOM 03238, MIL 05024, MIL 05104, MIL 07193 (CO3.1); TIL 82408, LAR 06279 (LL3.05-3.1); EET 90628 (L3.0); GRO 06054, QUE 97008 (L3.05), ALHA 77176, EET 90066, LAR 04380, MET 96515, MIL 05050 (L3.1); ALHA 78133, EET 87735, EET 90909, LEW 87208, PRE 95401 (L3.05-3.1); MCY 05218 (H3.05-3.1) and MET 00506 (H3.1). This study confirms that the width of the D band (FWHMD) and the ratio of the peak intensity of the D and G bands (ID/IG) are the most adapted tracers of the extent of thermal metamorphism in type 3 chondrites. It also unambiguously shows, thanks to the large number of samples, that the width of the G band (FWHMG) does not correlate with the maturity of polyaromatic carbonaceous matter. This parameter is nevertheless very valuable because it shows that Raman spectra of CV chondrites preserve memory of either the metamorphic conditions (possibly oxidation controlled by aqueous alteration) or the nature of the organic precursor. Oxidation memory is our preferred interpretation, however an extensive petrologic characterization of this CV series is required to get firm conclusions. Pre-graphitic carbonaceous matter is reported in seven chondrites and is even the only carbonaceous material detected in the chondrites ALHA 78119 and DAV 92302. This pre-graphitic carbonaceous matter cannot be formed through radiogenic thermal metamorphism without metal catalysis. Shock metamorphism is another possible process for accounting its formation, but it appears less plausible.

Deciphering igneous and metamorphic events in high-grade rocks of the Wilmington complex, Delaware: Morphology, cathodoluminescence and backscattered electron zoning, and SHRIMP U-Pb geochronology of zircon and monazite

USGS Publications Warehouse

Aleinikoff, J.N.; Schenck, W.S.; Plank, M.O.; Srogi, L.A.; Fanning, C.M.; Kamo, S.L.; Bosbyshell, H.

2006-01-01

High-grade rocks of the Wilmington Complex, northern Delaware and adjacent Maryland and Pennsylvania, contain morphologically complex zircons that formed through both igneous and metamorphic processes during the development of an island-arc complex and suturing of the arc to Laurentia. The arc complex has been divided into several members, the protoliths of which include both intrusive and extrusive rocks. Metasedimentary rocks are interlayered with the complex and are believed to be the infrastructure upon which the arc was built. In the Wilmingto n Complex rocks, both igneous and metamorphic zircons occur as elongate and equant forms. Chemical zoning, shown by cathodoluminescence (CL), includes both concentric, oscillatory patterns, indicative of igneous origin, and patchwork and sector patterns, suggestive of metamorphic growth. Metamorphic monazites are chemically homogeneous, or show oscillatory or spotted chemical zoning in backscattered electron images. U-Pb geochronology by sensitive high resolution ion microprobe (SHRIMP) was used to date complexly zoned zircon and monazite. All but one member of the Wilmington Complex crystallized in the Ordovician between ca. 475 and 485 Ma; these rocks were intruded by a suite of gabbro-to-granite plutonic rocks at 434 ?? Ma. Detrital zircons in metavolcanic and metasedimentary units were derived predominantly from 0.9 to 1.4 Ga (Grenvillian) basement, presumably of Laurentian origin. Amphibolite to granulite facies metamorphism of the Wilmington Complex, recorded by ages of metamorphic zircon (428 ?? 4 and 432 ?? 6 Ma) and monazite (429 ?? 2 and 426 ?? 3 Ma), occurred contemporaneously with emplacement of the younger plutonic rocks. On the basis of varying CL zoning patterns and external morphologies, metamorphic zircons formed by different processes (presumably controlled by rock chemistry) at slightly different times and temperatures during prograde metamorphism. In addition, at least three other thermal episodes are recorded by monazite growth at 447 ?? 4, 411 ?? 3, and 398 ?? 3 Ma. ?? 2006 Geological Society of America.

Association between arsenic and different-sized dissolved organic matter in the groundwater of black-foot disease area, Taiwan.

PubMed

Chen, Ting-Chien; Hseu, Zeng-Yei; Jean, Jiin-Shuh; Chou, Mon-Lin

2016-09-01

The formation of an arsenic (As)-dissolved organic matter (DOM) complex is important in driving the release of arsenic in groundwater. This study collected groundwater samples from a 20 m deep well throughout 2014 and separated each into three subsamples by ultrafiltration: high molecular weight-DOM (HDOM, 0.45 μm-10 kDa), medium molecular weight-DOM (MDOM, 10-1 kDa), and low molecular weight-DOM (LDOM, <1 kDa) solutions. The fractional DOM was measured with a three-dimensional excitation-emission matrix (EEM) via fluorescence spectroscopy. A fluorescence quenching method was used to calculate the apparent stability constant (Ks) between arsenic and the fractional DOM. Based on the EEM records, three fluorescence indicators were further calculated to characterize the DOM sources, including the fluorescence index (FI), the biological index (BI), and the humification index (HI). The experimental results indicated that arsenic in the groundwater was mainly partitioned into the MDOM and LDOM fractions. All fractional DOMs contained humic acid-like substances and were considered as microbial sources. LDOM had the highest humification degree and aromaticity, followed by MDOM and HDOM. The As and DOM association could be formed by a Fe-bridge, which was demonstrated by the Ks values and fourier transform infrared (FTIR) spectra of the DOM. The formation of AsFe-DOM complex was only significant in the MDOM and LDOM. Copyright © 2016 Elsevier Ltd. All rights reserved.

Thermobarometric constraints on mid-Cretaceous to late Cretaceous metamorphic events in the western metamorphic belt of the Coast Mountains complex near Petersburg, southeastern Alaska

USGS Publications Warehouse

Himmelberg, Glen R.; Brew, David A.

2005-01-01

The western metamorphic belt is part of the Coast Mountains Complex of southeastern Alaska and western Canada. This complex formed as a result of mid-Cretaceous through middle Eocene crustal shortening between the previously amalgamated Wrangellia and Alexander terranes (Insular superterrane) and previously accreted terranes of the North American continental margin (Intermontane superterrane). The western metamorphic belt, which ranges from a few kilometers to several tens of kilometers in width, records a complex sequence of contact-metamorphic and regional metamorphic events, the most significant of which are designated M1R, M2C-R, and M3R. The M1R regional metamorphic event ranged in grade from subgreenschist to greenschist facies and was overprinted by the M2C-R and M3R metamorphic events. The M2C-R metamorphic event is recorded in discrete contact-metamorphic aureoles and regional metamorphic-mineral assemblages related to tonalite-granodiorite plutons of the Admiralty-Revillagigedo plutonic belt. The M3R metamorphic belt, which is adjacent to the M2C-R belt, is characterized by regional Barrovian isograds of garnet, staurolite, kyanite, and sillimanite. Using the THERMOCALC program, pressure-temperature (P-T) conditions for the M2C-R metamorphic event are estimated to be in the ranges 5.3-7.5 kbars and 525-640 deg.C and for the M3R metamorphic event in the ranges 9.4-12.6 kbars and 730-895 deg.C. The M2C-R metamorphic event occurred at approximately 90 Ma, but the timing of the M3R metamorphic event is poorly documented and uncertain. On the basis of an 40Ar/39Ar age on actinolitic amphibole and a Sm-Nd age on garnet core, the timing of metamorphism might be constrained between 90+/-1 and 80+/-9 Ma, although the Sm-Nd age of 80+/-9 m.y. possibly reflects postpeak growth. Thermobarometric data suggest that the two events occurred at different crustal levels and followed different P-T paths. No evidence exists that M2C-R metamorphic-mineral assemblages were overprinted by the M3R metamorphic event, as proposed by some workers. Juxtaposition of the two belts of rocks probably occurred along the Coast shear zone during uplift and exhumation of the Coast Mountains.

Metal complexation properties of freshwater dissolved organic matter are explained by its aromaticity and by anthropogenic ligands.

PubMed

Baken, Stijn; Degryse, Fien; Verheyen, Liesbeth; Merckx, Roel; Smolders, Erik

2011-04-01

Dissolved organic matter (DOM) in surface waters affects the fate and environmental effects of trace metals. We measured variability in the Cd, Cu, Ni, and Zn affinity of 23 DOM samples isolated by reverse osmosis from freshwaters in natural, agricultural, and urban areas. Affinities at uniform pH and ionic composition were assayed at low, environmentally relevant free Cd, Cu, Ni, and Zn activities. The C-normalized metal binding of DOM varied 4-fold (Cu) or about 10-fold (Cd, Ni, Zn) among samples. The dissolved organic carbon concentration ranged only 9-fold in the waters, illustrating that DOM quality is an equally important parameter for metal complexation as DOM quantity. The UV-absorbance of DOM explained metal affinity only for waters receiving few urban inputs, indicating that in those waters, aromatic humic substances are the dominant metal chelators. Larger metal affinities were found for DOM from waters with urban inputs. Aminopolycarboxylate ligands (mainly EDTA) were detected at concentrations up to 0.14 μM and partly explained the larger metal affinity. Nickel concentrations in these surface waters are strongly related to EDTA concentrations (R2=0.96) and this is underpinned by speciation calculations. It is concluded that metal complexation in waters with anthropogenic discharges is larger than that estimated with models that only take into account binding on humic substances.

Structural stability of coprecipitated natural organic matter and ferric iron under reducing conditions

USGS Publications Warehouse

Henneberry, Yumiko K.; Kraus, Tamara E.C.; Nico, Peter S.; Horwath, William R.

2012-01-01

The objective was to assess the interaction of Fe coprecipitated with dissolved organic matter (DOM) and its effect on Fe (hydr)oxide crystallinity and DOM retention under abiotic reducing conditions. A Fe-based coagulant was reacted with DOM from an agricultural drain and the resulting precipitate (floc) was exposed to S(-II) and Fe(II). Solution concentrations of Fe(II/III) and DOM were monitored, floc crystallinity was determined using X-ray diffraction, and the composition and distribution of functional groups were assessed using scanning transmission X-ray microscopy (STXM) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. Results indicate coprecipitation of Fe(III) with DOM forms a non-crystalline floc that withstands crystallization regardless of change in pH, Fe:DOM ratio and type of reductant added. There was no evidence that exposure to reducing conditions led to release of DOM from the floc, indicating that coprecipitation with complex natural DOM in aquatic environments may stabilize Fe (hydr)oxides against crystallization upon reaction with reduced species and lead to long term sequestration of the DOM. STXM analysis identified spatially distinct regions with remarkable functional group purity, contrary to the model of DOM as a relatively uniform complex polymer lacking identifiable organic compounds. Polysaccharide-like OM was strongly and directly correlated with the presence of Fe but showed different Fe binding strength depending on the presence of carboxylic acid functional groups, whereas amide and aromatic functional groups were inversely correlated with Fe content.

Evaluating oxidation-reduction properties of dissolved organic matter from Chinese milk vetch (Astragalus sinicus L.): a comprehensive multi-parametric study.

PubMed

Liu, Yong; Lou, Jun; Li, Fang-Bai; Xu, Jian-Ming; Yu, Xiong-Sheng; Zhu, Li-An; Wang, Feng

2014-08-01

Green manuring is a common practice in replenishment of soil organic matter and nutrients in rice paddy field. Owing to the complex interplay of multiple factors, the oxidation--reduction (redox) properties of dissolved organic matter (DOM) from green manure crops are presently not fully understood. In this study, a variety of surrogate parameters were used to evaluate the redox capacity and redox state of DOM derived from Chinese milk vetch (CMV, Astragalus sinicus L.) via microbial decomposition under continuously flooded (CF) and non-flooded (NF) conditions. Additionally, the correlation between the surrogate parameters of CMV-DOM and the kinetic parameters of relevant redox reactions was evaluated in a soil-water system containing CMV-DOM. Results showed that the redox properties of CMV-DOM were substantially different between the fresh and decomposed CMV-DOM treatments. Determination of the surrogate parameters via ultraviolet-visible/Fourier transform infrared absorption spectroscopy and gel permeation chromatography generally provided high-quality data for predicting the redox capacity of CMV-DOM, while the surrogate parameters determined by elemental analysis were suitable for predicting the redox state of CMV-DOM. Depending on the redox capacity and redox state of various moieties/components, NF-decomposed CMV-DOM could easily accelerate soil reduction by shuttling electrons to iron oxides, because it contained more reversible redox-active functional groups (e.g. quinone and hydroquinone pairs) than CF-decomposed CMV-DOM. This work demonstrates that a single index cannot interpret complex changes in multiple factors that jointly determine the redox reactivity of CMV-DOM. Thus, a multi-parametric study is needed for providing comprehensive information on the redox properties of green manure DOM.

Evaluating the distribution of terrestrial dissolved organic matter in a complex coastal ecosystem using fluorescence spectroscopy

NASA Astrophysics Data System (ADS)

Yamashita, Youhei; Boyer, Joseph N.; Jaffé, Rudolf

2013-09-01

The coastal zone of the Florida Keys features the only living coral reef in the continental United States and as such represents a unique regional environmental resource. Anthropogenic pressures combined with climate disturbances such as hurricanes can affect the biogeochemistry of the region and threaten the health of this unique ecosystem. As such, water quality monitoring has historically been implemented in the Florida Keys, and six spatially distinct zones have been identified. In these studies however, dissolved organic matter (DOM) has only been studied as a quantitative parameter, and DOM composition can be a valuable biogeochemical parameter in assessing environmental change in coastal regions. Here we report the first data of its kind on the application of optical properties of DOM, in particular excitation emission matrix fluorescence with parallel factor analysis (EEM-PARAFAC), throughout these six Florida Keys regions in an attempt to assess spatial differences in DOM sources. Our data suggests that while DOM in the Florida Keys can be influenced by distant terrestrial environments such as the Everglades, spatial differences in DOM distribution were also controlled in part by local surface runoff/fringe mangroves, contributions from seasgrass communities, as well as the reefs and waters from the Florida Current. Application of principal component analysis (PCA) of the relative abundance of EEM-PARAFAC components allowed for a clear distinction between the sources of DOM (allochthonous vs. autochthonous), between different autochthonous sources and/or the diagenetic status of DOM, and further clarified contribution of terrestrial DOM in zones where levels of DOM were low in abundance. The combination between EEM-PARAFAC and PCA proved to be ideally suited to discern DOM composition and source differences in coastal zones with complex hydrology and multiple DOM sources.

Metamorphic P-T-t path retrieved from metapelites in the southeastern Taihua metamorphic complex, and the Paleoproterozoic tectonic evolution of the southern North China Craton

NASA Astrophysics Data System (ADS)

Lu, Jun-Sheng; Zhai, Ming-Guo; Lu, Lin-Sheng; Wang, Hao Y. C.; Chen, Hong-Xu; Peng, Tao; Wu, Chun-Ming; Zhao, Tai-Ping

2017-02-01

The Taihua metamorphic complex in the southern part of the North China Craton is composed of tonalite-trondhjemite-granodiorite (TTG) gneisses, amphibolites, metapelitic gneisses, marbles, quartzites, and banded iron formations (BIFs). The protoliths of the complex have ages ranging from ∼2.1 to ∼2.9 Ga and was metamorphosed under the upper amphibolite to granulite facies conditions with NWW-SEE-striking gneissosity. Metapelitites from the Wugang area have three stages of metamorphic mineral assemblages. The prograde metamorphic mineral assemblage (M1) includes biotite + plagioclase + quartz + ilmenite preserved as inclusions in garnet porphyroblasts. The peak mineral assemblage (M2) consists of garnet porphyroblasts and matrix minerals of sillimanite + biotite + plagioclase + quartz + K-feldspar + ilmenite + rutile + pyrite. The retrograde mineral assemblage (M3), biotite + plagioclase + quartz, occurs as symplectic assemblages surrounding embayed garnet porphyroblasts. Garnet porphyroblasts are chemically zoned. Pseudosection calculated in the NCKFMASHTO model system suggests that mantles of garnet porphyroblasts define high-pressure granulites facies P-T conditions of 12.2 kbar and 830 °C, whereas garnet rims record P-T conditions of 10.2 kbar and 840 °C. Integrating the prograde mineral assemblages, zoning of garnet porphyroblasts with symplectic assemblages, a clockwise metamorphic P-T path can be retrieved. High resolution SIMS U-Pb dating and LA-ICP-MS trace element measurements of the metamorphic zircons demonstrate that metapelites in Wugang possibly record the peak or near peak metamorphic ages of ∼1.92 Ga. Furthermore, 40Ar/39Ar dating of biotite in metapelites suggests that the cooling of the Taihua complex may have lasted until ∼1.83 Ga. Therefore, a long-lived Palaeoproterozoic metamorphic event may define a slow exhumation process. Field relationship and new metamorphic data for the Taihua metamorphic complex does not support the previous model in which the Tran-North China Craton (TNCO) was formed through the collision between the East and West blocks.

Fluorescence fingerprints and Cu2+-complexing ability of individual molecular size fractions in soil- and waste-borne DOM.

PubMed

Knoth de Zarruk, K; Scholer, G; Dudal, Y

2007-09-01

Land spreading of organic materials introduces large amounts of dissolved organic matter (DOM) into the soil. DOM has the ability to form stable complexes with heavy metals and can facilitate their transport towards the groundwater. The effects on soil processes are difficult to assess, because different DOM components might react differently towards metal ions. The objective of this study was to investigate the fluorescence signature and the Cu2+-binding capacity of individual molecular size fractions of DOM from various sources. DOM extracted from leaf compost, chicken manure, sugar cane vinasse and a fulvic hypercalcaric cambisol was fractionated by the means of dialysis into four molecular size classes: MW<500, 50012000-14000 Da. Vinasse and leaf compost contained around 80% and 70%, respectively, of the total organic carbon in the fractions with low molecular weight (MW<3500 Da); in chicken manure and soil these fractions accounted for 40% and 50% only. Fluorescence was highest in the fraction MW>12000 Da for leaf compost, chicken manure and soil. The opposite result was obtained for vinasse, where the fractions with low molecular weight showed highest fluorescence intensities, distinguishing it from all other samples. Vinasse showed the greatest ability to bind Cu2+ with a resulting complex concentration of 6.31mgl(-1) while in contact with an excess of Cu2+. Leaf compost, soil and chicken manure followed with 2.69, 1.12, and 0.85mgl(-1), respectively. Within vinasse, the fraction MW<500 Da was able to form the most DOM-Cu complexes, indicating the importance of low molecular weight fractions in metal binding.

Effect of dissolved organic matter (DOM) of contrasting origins on Cu and Pb speciation and toxicity to Paracentrotus lividus larvae.

PubMed

Sánchez-Marín, Paula; Santos-Echeandía, Juan; Nieto-Cid, Mar; Alvarez-Salgado, Xosé Antón; Beiras, Ricardo

2010-01-31

Water samples of contrasting origin, including natural seawater, two sediment elutriates and sewage-influenced seawater, were collected and obtained to examine the effect of the dissolved organic matter (DOM) present on metal bioavailability. The carbon content (DOC) and the optical properties (absorbance and fluorescence) of the coloured DOM fraction (CDOM) of these materials were determined. Cu and Pb complexation properties were measured by anodic stripping voltammetry (ASV) and the effect of DOM on Cu and Pb bioavailability was studied by means of the Paracentrotus lividus embryo-larval bioassay. Sediment elutriates and sewage-influenced water (1) were enriched 1.4-1.7 times in DOC; (2) absorbed and reemitted more light; and (3) presented higher Cu complexation capacities (L(Cu)) than the natural seawater used for their preparation. L(Cu) varied from 0.08 microM in natural seawater to 0.3 and 0.5 microM in sediment elutriates and sewage-influenced water, respectively. Differences in DOC, CDOM and Cu complexation capacities were reflected in Cu toxicity. DOM enriched samples presented a Cu EC(50) of 0.64 microM, significantly higher than the Cu EC(50) of natural and artificial seawater, which was 0.38 microM. The protecting effect of DOM on Cu toxicity greatly disappeared when the samples were irradiated with high intensity UV-light. Cu toxicity could be successfully predicted considering ASV-labile Cu concentrations in the samples. Pb complexation by DOM was only detected in the DOM-enriched samples and caused little effect on Pb EC(50). This effect was contrary for both elutriates: one elutriate reduced Pb toxicity in comparison with the control artificial seawater, while the other increased it. UV irradiation of the samples caused a marked increase in Pb toxicity, which correlated with the remaining DOC concentration. DOM parameters were related to Cu speciation and toxicity: good correlations were found between DOC and Cu EC(50), while L(Cu) correlated better with the fluorescence of marine humic substances. The present results stress the importance of characterizing not only the amount but also the quality of seawater DOM to better predict ecological effects from total metal concentration data. Copyright (c) 2009 Elsevier B.V. All rights reserved.

CONSTANTS FOR MERCURY BINDING BY DISSOLVED ORGANIC MATTER ISOLATES FROM THE FLORIDA EVERGLADES. (R827653)

EPA Science Inventory

Dissolved organic matter (DOM) has been implicated as an important complexing agent for Hg that can affect its mobility and bioavailability in aquatic ecosystems. However, binding constants for natural Hg-DOM complexes are not well known. We employed a competitive ligand appro...

Relevant role of dissolved humic matter in phosphorus bioavailability in natural and agronomical ecosystems through the formation of Humic-(Metal)-Phosphate complexes

NASA Astrophysics Data System (ADS)

Baigorri, Roberto; Urrutia, Óscar; Erro, Javier; Pazos-Pérez, Nicolás; María García-Mina, José

2016-04-01

Natural Organic Matter (NOM) and the NOM fraction present in soil solution (dissolved organic matter: DOM) are currently considered as fundamental actors in soil fertility and crop mineral nutrition. Indeed, decreases in crop yields as well as soil erosion are closely related to low values of NOM and, in fact, the use of organic amendments as both soil improvers and plant growth enhancers is very usual in countries with soils poor in NOM. This role of NOM (and DOM) seems to be associated with the presence of bio-transformed organic molecules (humic substances) with high cation chelating-complexing ability. In fact, bioavailable micronutrients with metallic character in soil solutions of alkaline and calcareous soils are forming stable complexes with DOM. This beneficial action of DOM also concerns other plant nutrients such as inorganic phosphate (Pi). Among the different mechanisms involved in the beneficial action of DOM on P bioavailability, the possible formation of poly-nuclear complexes including stable chemical bonds between negative binding sites in humic substances and Pi through metal bridges in soil solution might be relevant, especially in acidic soils. In fact, several studies have proven that these complexes can be obtained in the laboratory and are very efficient in prevent Pi soil fixation and improve Pi root uptake. However, clear experimental evidence about their presence in soil solutions of natural and agronomical soil ecosystems has not published yet. We present here experimental results supporting the real presence of stable Pi-metal-Humic (PMH) complexes in the soil solution of several acidic soils. The study is based on the physico-chemical characterization (31P-NMR, FTIR, TEM-EDAX, ICP-OES) of the DOM fraction isolated by ultrafiltration from the soil solution of several representative acidic soils. In average, more than 60 % of Pi was found in the soil solution humic fraction forming stable humic-metal (Fe, Al) complexes.

Insights into the interaction between carbamazepine and natural dissolved organic matter in the Yangtze Estuary using fluorescence excitation-emission matrix spectra coupled with parallel factor analysis.

PubMed

Wang, Ying; Zhang, Manman; Fu, Jun; Li, Tingting; Wang, Jinggang; Fu, Yingyu

2016-10-01

The interaction between carbamazepine (CBZ) and dissolved organic matter (DOM) from three zones (the nearshore, the river channel, and the coastal areas) in the Yangtze Estuary was investigated using fluorescence quenching titration combined with excitation emission matrix spectra and parallel factor analysis (PARAFAC). The complexation between CBZ and DOM was demonstrated by the increase in hydrogen bonding and the disappearance of the C=O stretch obtained from the Fourier transform infrared spectroscopy analysis. The results indicated that two protein-like substances (component 2 and component3) and two humic-like substances (component 1 and 4) were identified in the DOM from the Yangtze Estuary. The fluorescence quenching curves of each component with the addition of CBZ and the Ryan and Weber model calculation results both demonstrated that the different components exhibited different complexation activities with CBZ. The protein-like components had a stronger affinity with CBZ than did the humic-like substances. On the other hand, the autochthonous tyrosine-like C2 played an important role in the complexation with DOM from the river channel and coastal areas, while C3 influenced by anthropogenic activities showed an obvious effect in the nearshore area. DOMs from the river channel have the highest binding capacity for CBZ, which may ascribe to the relatively high phenol content group in the DOM.

Sr-isotopic composition of marbles from the Puerto Galera area (Mindoro, Philippines): additional evidence for a Paleozoic age of a metamorphic complex in the Philippine island arc

DOE Office of Scientific and Technical Information (OSTI.GOV)

Knittel, U.; Daniels, U.

1987-02-01

The Sr-isotopic composition of marbles from the Puerto Galera area (Mindoro, Philippines) is compatible with either a Tertiary or a Paleozoic age. The former is considered as unlikely because nonmetamorphic sediments of that age overlie the metamorphic complex. This implies that the metamorphic complex does not represent the basement of the Philippine arc but is an accreted terrane.

Dissolved Organic Matter Quality in a Shallow Aquifer of Bangladesh: Implications for Arsenic Mobility.

PubMed

Mladenov, Natalie; Zheng, Yan; Simone, Bailey; Bilinski, Theresa M; McKnight, Diane M; Nemergut, Diana; Radloff, Kathleen A; Rahman, M Moshiur; Ahmed, Kazi Matin

2015-09-15

In some high arsenic (As) groundwater systems, correlations are observed between dissolved organic matter (DOM) and As concentrations, but in other systems, such relationships are absent. The role of labile DOM as the main driver of microbial reductive dissolution is not sufficient to explain the variation in DOM-As relationships. Other processes that may also influence As mobility include complexation of As by dissolved humic substances, and competitive sorption and electron shuttling reactions mediated by humics. To evaluate such humic DOM influences, we characterized the optical properties of filtered surface water (n = 10) and groundwater (n = 24) samples spanning an age gradient in Araihazar, Bangladesh. Further, we analyzed large volume fulvic acid (FA) isolates (n = 6) for optical properties, C and N content, and (13)C NMR spectroscopic distribution. Old groundwater (>30 years old) contained primarily sediment-derived DOM and had significantly higher (p < 0.001) dissolved As concentration than groundwater that was younger than 5 years old. Younger groundwater had DOM spectroscopic signatures similar to surface water DOM and characteristic of a sewage pollution influence. Associations between dissolved As, iron (Fe), and FA concentration and fluorescence properties of isolated FA in this field study suggest that aromatic, terrestrially derived FAs promote As-Fe-FA complexation reactions that may enhance As mobility.

Molecular-level dynamics of refractory dissolved organic matter

NASA Astrophysics Data System (ADS)

Niggemann, J.; Gerdts, G.; Dittmar, T.

2012-04-01

Refractory dissolved organic matter (DOM) accounts for most of the global oceanic organic carbon inventory. Processes leading to its formation and factors determining its stability are still largely unknown. We hypothesize that refractory DOM carries a universal molecular signature. Characterizing spatial and temporal variability in this universal signature is a key to understanding dynamics of refractory DOM. We present results from a long-term study of the DOM geo-metabolome in the open North Sea. Geo-metabolomics considers the entity of DOM as a population of compounds, each characterized by a specific function and reactivity in the cycling of energy and elements. Ten-thousands of molecular formulae were identified in DOM by ultrahigh resolution mass spectrometry analysis (FT-ICR-MS, Fourier-Transform Ion Cyclotron Resonance Mass Spectrometry). The DOM pool in the North Sea was influenced by a complex interplay of processes that produced, transformed and degraded dissolved molecules. We identified a stable fraction in North Sea DOM with a molecular composition similar to deep ocean DOM. Molecular-level changes in this stable fraction provide novel information on dynamics and interactions of refractory DOM.

High abundances of presolar grains and 15N-rich organic matter in CO3.0 chondrite Dominion Range 08006

NASA Astrophysics Data System (ADS)

Nittler, Larry R.; Alexander, Conel M. O'D.; Davidson, Jemma; Riebe, My E. I.; Stroud, Rhonda M.; Wang, Jianhua

2018-04-01

NanoSIMS C-, N-, and O-isotopic mapping of matrix in CO3.0 chondrite Dominion Range (DOM) 08006 revealed it to have in its matrix the highest abundance of presolar O-rich grains (257 +76/-96 ppm, 2σ) of any meteorite. It also has a matrix abundance of presolar SiC of 35 (+25/-17, 2σ) ppm, similar to that seen across primitive chondrite classes. This provides additional support to bulk isotopic and petrologic evidence that DOM 08006 is the most primitive known CO meteorite. Transmission electron microscopy of five presolar silicate grains revealed one to have a composite mineralogy similar to larger amoeboid olivine aggregates and consistent with equilibrium condensation, two non-stoichiometric amorphous grains, and two olivine grains, though one is identified as such solely based on its composition. We also found insoluble organic matter (IOM) to be present primarily as sub-micron inclusions with ranges of C- and N-isotopic anomalies similar to those seen in primitive CR chondrites and interplanetary dust particles. In contrast to other primitive extraterrestrial materials, H isotopic imaging showed normal and homogeneous D/H. Most likely, DOM 08006 and other CO chondrites accreted a similar complement of primitive and isotopically anomalous organic matter to that found in other chondrite classes and IDPs, but the very limited amount of thermal metamorphism experienced by DOM 08006 has caused loss of D-rich organic moieties, while not substantially affecting either the molecular carriers of C and N anomalies or most inorganic phases in the meteorite. One C-rich grain that was highly depleted in 13C and 15N was identified; we propose it originated in the Sun's parental molecular cloud.

A targeted genetic modifier screen links the SWI2/SNF2 protein domino to growth and autophagy genes in Drosophila melanogaster.

PubMed

Kwon, Matt Hyoung; Callaway, Heather; Zhong, Jim; Yedvobnick, Barry

2013-05-20

Targeted genetic studies can facilitate phenotypic analyses and provide important insights into development and other complex processes. The SWI2/SNF2 DNA-dependent ATPase Domino (Dom) of Drosophila melanogaster, a component of the Tip60 acetyltransferase complex, has been associated with a wide spectrum of cellular processes at multiple developmental stages. These include hematopoiesis, cell proliferation, homeotic gene regulation, histone exchange during DNA repair, and Notch signaling. To explore the wider gene network associated with Dom action, we used RNAi directed against domino (dom) to mediate loss-of-function at the wing margin, a tissue that is readily scored for phenotypic changes. Dom RNAi driven through GAL4-UAS elicited dominant wing nicking that responded phenotypically to the dose of dom and other loci known to function with dom. We screened for phenotypic modifiers of this wing phenotype among 2500 transpositions of the EP P element and found both enhancers and suppressors. Several classes of modifier were obtained, including those encoding transcription factors, RNA regulatory proteins, and factors that regulate cell growth, proliferation and autophagy, a lysosomal degradation pathway that affects cell growth under conditions of starvation and stress. Our analysis is consistent with prior studies, suggesting that Dom acts pleiotropically as a positive effector of Notch signaling and a repressor of proliferation. This genetic system should facilitate screens for additional loci associated with Dom function, and complement biochemical approaches to their regulatory activity.

Late Carboniferous high-pressure metamorphism of the Kassan Metamorphic Complex (Kyrgyz Tianshan) and assembly of the SW Central Asian Orogenic Belt

NASA Astrophysics Data System (ADS)

Mühlberg, M.; Hegner, E.; Klemd, R.; Pfänder, J. A.; Kaliwoda, M.; Biske, Y. S.

2016-11-01

High-pressure (HP) metamorphism of the Kassan Metamorphic Complex (KMC) in the western Kyrgyz Tianshan has been related to either late Ordovician or late Carboniferous-Permian subduction processes. We report Sm-Nd ages for retrogressed eclogite samples and 40Ar/39Ar cooling ages for enclosing garnet-muscovite samples from the KMC as new age constraints on HP metamorphism and rock exhumation. These data will be used for an upgraded paleogeographic model for late Paleozoic crustal consolidation in the southwestern Central Asian Orogenic Belt. The retrogressed eclogite samples have transitional alkaline to tholeiitic affinity and trace-element patterns consistent with protoliths derived from garnet-bearing mantle sources at rifting plate margins. Geothermobarometric data for a retrogressed eclogite sample indicate peak-metamorphic conditions of 540 ± 30 °C at 1.6 ± 0.1 GPa. Samples from different lithotectonic units of the KMC provide coherent Sm-Nd garnet-whole rock ages of 317 ± 4 Ma and 316 ± 3 Ma (2σ). The prograde major-element zoning in the mm-sized garnets in combination with the moderate peak-metamorphic temperature, support our interpretation of the Sm-Nd garnet ages as unambiguous evidence for late Carboniferous HP metamorphism. The Sm-Nd garnet growth ages overlap within-error with the 40Ar/39Ar mica cooling ages of 314 ± 2 Ma and 313 ± 2 Ma (2σ) indicating rapid uplift of the subduction complex after peak metamorphism. The ca. 317-313 Ma HP-exhumation event of the KMC is contemporaneous with those of the Atbashi and Akeyazi (ca. 500 km east in NW China) HP complexes and implies similar collision histories at the South Tianshan Suture to the east and west of the Talas-Fergana Fault (TFF). The exhumation of the KMC and Atbashi HP complexes overlaps with the initiation of the TFF (Rolland et al., 2013) suggesting incipient separation of the Chatkal and Atbashi complexes during rock exhumation and early plate collision.

Why dissolved organic matter (DOM) enhances photodegradation of methylmercury

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qian, Yun; Yin, Xiangping Lisa; Brooks, Scott C

2014-01-01

Methylmercury (MeHg) is known to degrade photochemically, but it remains unclear what roles naturally dissolved organic matter (DOM) and complexing organic ligands play in MeHg photodegradation. Here we investigate the rates and mechanisms of MeHg photodegradation using DOM samples with varying oxidation states and origins as well as organic ligands with known molecular structures. All DOM and organic ligands increased MeHg photodegradation under solar irradiation, but the first-order rate constants varied depending on the oxidation state of DOM and the type and concentration of the ligands. Compounds containing both thiols and aromatics (e.g., thiosalicylate and reduced DOM) increased MeHg degradationmore » rates far greater than those containing only aromatic or thiol functional groups (e.g., salicylate or glutathione). Our results suggest that, among other factors, the synergistic effects of thiolate and aromatic moieties in DOM greatly enhance MeHg photodegradation.« less

Metamorphism within the Chugach accretionary complex on southern Baranof Island, southeastern Alaska

USGS Publications Warehouse

Zumsteg, Cathy L.; Himmelberg, Glen R.; Karl, Susan M.; Haeussler, Peter J.

2003-01-01

On Baranof Island, southeastern Alaska, we identify four metamorphic events that affect rocks associated with the Chugach accretionary complex. This study focuses on the M1 and M4 metamorphic events. Mesozoic schists, gneisses, and migmatitic gneisses exposed near the Kasnyku pluton on central Baranof Island represent the M1 metamorphic rocks. These rocks underwent amphibolite facies metamorphism. Calculated temperatures and pressures range from about 620 to 780 ºC and 5.5 to 6.6 kbar and are compatible with the observed metamorphic mineral assemblages.The M4 metamorphism affected rocks of the Sitka Graywacke on southern Baranof Island, producing extensive biotite and garnet zones as well as andalusite and sillimanite zones at the contacts of the Crawfish Inlet and Redfish Bay plutons. Calculated M4 temperatures and pressures from the andalusite and sillimanite zones range from 575 to 755 ºC and 3.4 to 6.9 kbar. These results fall within the sillimanite stability field, at pressures higher than andalusite stability. These results may indicate the M4 metamorphic event occurred along a P-T path along which the equilibration of aluminosilicate-garnet-plagioclase-quartz did not occur or was not maintained. This interpretation is supported by the occurrence of andalusite and sillimanite within the same sample. We propose the data reflect a clockwise P-T path with peak M4 metamorphism of the sillimanite-bearing samples adjacent to the intrusions at an approximate depth of 15 to 20 km, followed by rapid uplift without reequilibration of garnet-plagioclase-aluminosilicate-quartz.The large extent of the biotite zone, and possibly the garnet zone, suggests that an additional heat source must have existed to regionally metamorphose these rocks during the M4 event. We suggest the M4 regional thermal metamorphism and intrusion of the Crawfish Inlet and Redfish Bay plutons were synchronous and the result of heat flux from a slab window beneath the accretionary complex at that time. If our conclusions regarding the effect of the slab window are correct, the style of metamorphism is different from the Chugach metamorphic complex, which is clearly linked to a slab window. Therefore, our findings would suggest that there is no distinct metamorphic signature for slab window effects.

Intermediate P/T-type regional metamorphism of the Isua Supracrustal Belt, southern west Greenland: The oldest Pacific-type orogenic belt?

NASA Astrophysics Data System (ADS)

Arai, Tatsuyuki; Omori, Soichi; Komiya, Tsuyoshi; Maruyama, Shigenori

2015-11-01

The 3.7-3.8 Ga Isua Supracrustal Belt (ISB), southwest Greenland, might be the oldest accretionary complex on Earth. Regional metamorphism of the ISB has a potential to constrain the tectonothermal history of the Earth during the Eoarchean. Chemical and modal analyses of metabasite in the study area (i.e., the northeast part of the ISB) show that the metamorphic grade increases from greenschist facies in the northern part of the study area to amphibolite facies in the southern part. To determine the precise metamorphic P-T ranges, isochemical phase diagrams of minerals of metabasite were made using Perple_X. A synthesis of the estimated metamorphic P-T ranges of the ISB indicates that both the metamorphic pressure and temperature increase systematically to the south in the study area from 3 kbar and 380 °C to 6 kbar and 560 °C. The monotonous metamorphic P-T change suggests that the northeast part of the ISB preserves regional metamorphism resulting from the subduction of an accretionary complex although the ISB experienced metamorphic overprints during the Neoarchean. Both the presence of the regional metamorphism and an accretionary complex having originating at subduction zone suggest that the ISB may be the oldest Pacific-type orogenic belt. The progressive metamorphism can be considered as a record of intermediate-P/T type geothermal gradient at the subduction zone in the Eoarchean. Intermediate-P/T type geothermal gradient is typical at the current zones of subducting young oceanic crust, such as in the case of the Philippine Sea Plate in the southwest part of Japan. Considering the fact that almost all metamorphisms in the Archean are greenschist-amphibolite facies, the intermediate-P/T type geothermal gradient at the ISB might have been worldwide in the Archean. This would indicate that the subduction of young micro-plates was common because of the vigorous convection of hot mantle in the Archean.

Nematode feeding strategies and the fate of dissolved organic matter carbon in different deep-sea sedimentary environments

NASA Astrophysics Data System (ADS)

Pape, Ellen; van Oevelen, Dick; Moodley, Leon; Soetaert, Karline; Vanreusel, Ann

2013-10-01

Sediments sampled from the Galicia Bank seamount and the adjacent slope (northeast Atlantic), and from a western Mediterranean slope site, were injected onboard with 13C-enriched dissolved organic matter (DOM) to evaluate nematode feeding strategies and the fate of DOM carbon in different benthic environments. We hypothesized that nematode 13C label assimilation resulted from either direct DOM uptake or feeding on 13C labeled bacteria. Slope sediments were injected with glucose ("simple" DOM) or "complex" diatom-derived DOM to investigate the influence of DOM composition on carbon assimilation. The time-series (1, 7 and 14 days) experiment at the seamount site was the first study to reveal a higher 13C enrichment of nematodes than bacteria and sediments after 7 days. Although isotope dynamics indicated that both DOM and bacteria were plausible candidate food sources, the contribution to nematode secondary production and metabolic requirements (estimated from biomass-dependent respiration rates) was higher for bacteria than for DOM at all sites. The seamount nematode community showed higher carbon assimilation rates than the slope assemblages, which may reflect an adaptation to the food-poor environment. Our results suggested that the trophic importance of bacteria did not depend on the amount of labile sedimentary organic matter. Furthermore, there was a discrepancy between carbon assimilation rates observed in the experiments and the feeding type classification, based on buccal morphology. Sites with a similar feeding type composition (i.e. the northeast Atlantic sites) showed large differences in uptake, whilst the nematode assemblages at the two slope sites, which had a differing trophic structure, took up similar amounts of the DOM associated carbon. Our results did not indicate substantial differences in carbon processing related to the complexity of the DOM substrate. The quantity of processed carbon (5-42% of added DOM) was determined by the bacteria, and was primarily respired. The bulk of the added 13C-DOM was not ingested by the benthic biota under study, and a considerable fraction was possibly adsorbed onto the sediment grains.

Biodegradation kinetics of dissolved organic matter chromatographic fractions in an intermittent river

NASA Astrophysics Data System (ADS)

Catalán, N.; Casas-Ruiz, J. P.; von Schiller, D.; Proia, L.; Obrador, B.; Zwirnmann, E.; Marcé, R.

2017-01-01

Controls on the degradation of dissolved organic matter (DOM) are complex but key to understand the role of freshwaters in the carbon cycle. Both the origin and previous degradation history have been suggested to determine DOM reactivity, but it is still a major challenge to understand the links between DOM composition and biodegradation kinetics. An appropriate context to study these links are intermittent rivers, as summer drought naturally diversifies DOM sources and sinks. Here we investigated the biodegradation kinetics of DOM in the main aquatic environments present in a temporary river. During dark incubations we traced the dynamics of bulk DOM and its main chromatographic fractions defined using LC-OCD: high molecular weight substances (HMWS), low molecular weight substances (LMWS), and humic substances and building blocks. Bulk DOM decay patterns were successfully fitted to the reactivity continuum (RC) biodegradation model. The RC parameters depicted running waters as the sites presenting a more reactive DOM, and temporary pools, enriched in leaf litter, as the ones with slowest DOM decay. The decay patterns of each DOM fraction were consistent throughout sites. LMWS and HMWS decayed in all cases and could be modeled using the RC model. Notably, the dynamics of LMWS controlled the bulk DOM kinetics. We discuss the mechanistic basis for the chromatographic fractions' kinetics during biodegradation and the implications that preconditioning and summer drought can have for DOM biodegradation in intermittent rivers.

Copper toxicity and organic matter: Resiliency of watersheds in the Duluth Complex, Minnesota, USA

USGS Publications Warehouse

Piatak, Nadine; Seal, Robert; Jones, Perry M.; Woodruff, Laurel G.

2015-01-01

We estimated copper (Cu) toxicity in surface water with high dissolved organic matter (DOM) for unmined mineralized watersheds of the Duluth Complex using the Biotic Ligand Model (BLM), which evaluates the effect of DOM, cation competition for biologic binding sites, and metal speciation. A sediment-based BLM was used to estimate stream-sediment toxicity; this approach factors in the cumulative effects of multiple metals, incorporation of metals into less bioavailable sulfides, and complexation of metals with organic carbon. For surface water, the formation of Cu-DOM complexes significantly reduces the amount of Cu available to aquatic organisms. The protective effects of cations, such as calcium (Ca) and magnesium (Mg), competing with Cu to complex with the biotic ligand is likely not as important as DOM in water with high DOM and low hardness. Standard hardness-based water quality criteria (WQC) are probably inadequate for describing Cu toxicity in such waters and a BLM approach may yield more accurate results. Nevertheless, assumptions about relative proportions of humic acid (HA) and fulvic acid (FA) in DOM significantly influence BLM results; the higher the HA fraction, the higher calculated resiliency of the water to Cu toxicity. Another important factor is seasonal variation in water chemistry, with greater resiliency to Cu toxicity during low flow compared to high flow.Based on generally low total organic carbon and sulfur content, and equivalent metal ratios from total and weak partial extractions, much of the total metal concentration in clastic streambedsediments may be in bioavailable forms, sorbed on clays or hydroxide phases. However, organicrich fine-grained sediment in the numerous wetlands may sequester significant amount of metals, limiting their bioavailability. A high proportion of organic matter in waters and some sediments will play a key role in the resiliency of these watersheds to potential additional metal loads associated with future mining operations.

Interactions between copper(II) and DOM in the urban stormwater runoff: modeling and characterizations.

PubMed

Zhao, Chen; Wang, Chong-Chen; Li, Jun-Qi; Wang, Peng; Ou, Jia-Qi; Cui, Jing-Rui

2018-01-01

Dissolved organic matter (DOM) can strongly interact with both organic and inorganic contaminants to influence their transportation, transformation, bioavailability, toxicity and even their ultimate fate. Within this work, DOM was extracted from urban stormwater runoff samples collected from a regular sampling site of a typical residential area in Beijing, China. Copper(II) ions were selected as model to investigate the interactions between DOM and typical heavy metals. Both ultraviolet (UV) absorbance and fluorescence titration methods were introduced to determine the complex capacities (C L ) and conditional stability constants (log K M ) of bonding between DOM and copper (II) ions, which revealed that the values of C L were 85.62 and 87.23 μmol mg -1 and the log K M values were 5.37 and 5.48, respectively. The results suggested the successful complexation between DOM and copper(II) ions. Furthermore, morphology of the DOM binding to copper(II) ions was confirmed by both energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS), which can facilitate to clarify the corresponding mechanism. The Cu 2p 3/2 peak at 933.7 eV and the characteristic shake-up peaks of Cu-O were found in the XPS spectra, implying that copper(II) ions might coordinate with hydroxyl (aliphatic or phenolic) or carboxyl groups. With these profitable results, it can be concluded that DOM in urban stormwater runoff has a strong binding affinity with copper(II) ions, which may further lead to potentially significant influence on their migration and transformation.

Major structural components in freshwater dissolved organic matter.

PubMed

Lam, Buuan; Baer, Andrew; Alaee, Mehran; Lefebvre, Brent; Moser, Arvin; Williams, Antony; Simpson, André J

2007-12-15

Dissolved organic matter (DOM) contains a complex array of chemical components that are intimately linked to many environmental processes, including the global carbon cycle, and the fate and transport of chemical pollutants. Despite its importance, fundamental aspects, such as the structural components in DOM remain elusive, due in part to the molecular complexity of the material. Here, we utilize multidimensional nuclear magnetic resonance spectroscopy to demonstrate the major structural components in Lake Ontario DOM. These include carboxyl-rich alicyclic molecules (CRAM), heteropolysaccharides, and aromatic compounds, which are consistent with components recently identified in marine dissolved organic matter. In addition, long-range proton-carbon correlations are obtained for DOM, which support the existence of material derived from linear terpenoids (MDLT). It is tentatively suggested that the bulk of freshwater dissolved organic matter is aliphatic in nature, with CRAM derived from cyclic terpenoids, and MDLT derived from linear terpenoids. This is in agreement with previous reports which indicate terpenoids as major precursors of DOM. At this time it is not clear in Lake Ontario whether these precursors are of terrestrial or aquatic origin or whether transformations proceed via biological and/ or photochemical processes.

Can the Metamorphic Basement of Northwestern Guatemala be Correlated with the Chuacús Complex?

NASA Astrophysics Data System (ADS)

Cacao, N.; Martens, U.

2007-05-01

The Chuacús complex constitutes a northward concave metamorphic belt that stretches ca. 150 km south of the Cuilco-Chixoy-Polochic (CCP) fault system in central and central-eastern Guatemala. It represents the basement of the southern edge of the Maya block, being well exposed in the sierra de Chuacús and the sierra de Las Minas. It is composed of high-Al metapelites, amphibolites, quartzofeldspathic gneisses, and migmatites. In central Guatemala the Chuacús complex contains ubiquitous epidote-amphibolite mineral associations, and local relics of eclogite reveal a previous high-pressure metamorphic event. North of the CCP, in the Sierra de Los Cuchumatanes area of western Guatemala, metamorphic rocks have been considered the equivalent of the Chuacús complex and hence been given the name Western Chuacús group, These rocks, which were intruded by granitic rocks and later mylonitized, include chloritic schist and gneiss, biotite-garnet schist, migmatites, and amphibolites. No eclogitic relics have been found within metamorphic rocks in northwestern Guatemala. Petrographic analyses of garnet-biotite schist reveal abundant retrogression and the formation of abundant zeolite-bearing veins associated with intrusion. Although metamorphic conditions in the greenschist and amphibolite facies are similar to those in the sierra de Chuacús, the association with deformed intrusive granites is unique for western Guatemala. Hence a correlation with metasediments intruded by the Rabinal granite in the San Gabriel area of Baja Verapaz seems more feasible than a correlation with the Chuacús complex. This idea is supported by reintegration of the Cenozoic left-lateral displacement along the CCP, which would place the metamorphic basement of western Guatemala north of Baja Verapaz, adjacent to metasediments intruded by granites in the San Gabriel-Rabinal area.

Origin and geodynamic significance of the early Mesozoic Weiya LP and HT granulites from the Chinese Eastern Tianshan

NASA Astrophysics Data System (ADS)

Mao, Ling-Juan; He, Zhen-Yu; Zhang, Ze-Ming; Klemd, Reiner; Xiang, Hua; Tian, Zuo-Lin; Zong, Ke-Qing

2015-12-01

The Chinese Tianshan in the southwestern part of the Central Asian Orogenic Belt (CAOB) is characterized by a variety of high-grade metamorphic rocks, which provide critical constraints for understanding the geodynamic evolution of the CAOB. In this paper, we present detailed petrological and zircon U-Pb geochronological studies of the Weiya low-pressure and high-temperature (LP-HT) granulites of the Chinese Eastern Tianshan. These granulites were previously considered to be a product of a regional metamorphic orogenic event. Due to different bulk-rock chemistries the Weiya granulites, which occur as lenses within the contact metamorphic aureole of the Weiya granitic ring complex, have a variety of felsic-pelitic and mafic granulites with different textural equilibrium mineral assemblages including garnet-cordierite-sillimanite-bearing granulites, cordierite-sillimanite-bearing granulites, cordierite-orthopyroxene-bearing granulites, and orthopyroxene-clinopyroxene-bearing granulites. Average P-T thermobarometric calculations and conventional geothermobarometry indicates that the Weiya granulites underwent early prograde metamorphism under conditions of 600-650 °C at 3.2-4.2 kbar and peak metamorphism of 750-840 °C at 2.9-6.3 kbar, indicating a rather high geothermal gradient of ca. 60 °C/km. Zircon U-Pb LA-ICP-MS dating revealed metamorphic ages between 244 ± 1 to 237 ± 3 Ma, which are in accordance with the crystallization age of the Weiya granitic ring complex. We suggest that the formation of the Weiya granulites was related to contemporaneous granitic magmatism instead of a regional metamorphic orogenic event. In addition, a Late Devonian metamorphic age of ca. 380 Ma was recorded in zircon mantle domains from two pelitic samples which is consistent with the metamorphic age of the Xingxingxia metamorphic complex in the Chinese Eastern Tianshan. This suggests that the mantle domains of the zircon grains of the Weiya granulites probably formed during the Late Devonian regional metamorphism and were overprinted by the Early Triassic contact metamorphism. Therefore, Early Triassic geodynamic models for the southwestern part of the CAOB, which are based on a previously suggested regional metamorphic orogenic event of the Weiya granulites, need to be viewed with caution.

Pre-treatments, characteristics, and biogeochemical dynamics of dissolved organic matter in sediments: A review.

PubMed

Chen, Meilian; Hur, Jin

2015-08-01

Dissolved organic matter (DOM) in sediments, termed here sediment DOM, plays a variety of important roles in global biogeochemical cycling of carbon and nutrients as well as in the fate and transport of xenobiotics. Here we reviewed sediment DOM, including pore waters and water extractable organic matter from inland and coastal sediments, based on recent literature (from 1996 to 2014). Sampling, pre-treatment, and characterization methods for sediment DOM were summarized. The characteristics of sediment DOM have been compared along an inland to coastal ecosystems gradient and also with the overlying DOM in water column to distinguish the unique nature of it. Dissolved organic carbon (DOC) from inland sediment DOM was generally higher than coastal areas, while no notable differences were found for their aromaticity and apparent molecular weight. Fluorescence index (FI) revealed that mixed sources are dominant for inland sediment DOM, but marine end-member prevails for coastal sediment DOM. Many reports showed that sediments operate as a net source of DOC and chromophoric DOM (CDOM) to the water column. Sediment DOM has shown more enrichment of nitrogen- and sulfur-containing compounds in the elemental signature than the overlying DOM. Fluorescent fingerprint investigated by excitation-emission matrix coupled with parallel factor analysis (EEM-PARAFAC) further demonstrated the characteristics of sediment DOM lacking in the photo-oxidized and the intermediate components, which are typically present in the overlying surface water. In addition, the biogeochemical changes in sediment DOM and the subsequent environmental implications were discussed with the focus on the binding and the complexation properties with pollutants. Copyright © 2015 Elsevier Ltd. All rights reserved.

Evaluation of passive samplers for the collection of dissolved organic matter in streams.

PubMed

Warner, Daniel L; Oviedo-Vargas, Diana; Royer, Todd V

2015-01-01

Traditional sampling methods for dissolved organic matter (DOM) in streams limit opportunities for long-term studies due to time and cost constraints. Passive DOM samplers were constructed following a design proposed previously which utilizes diethylaminoethyl (DEAE) cellulose as a sampling medium, and they were deployed throughout a temperate stream network in Indiana. Two deployments of the passive samplers were conducted, during which grab samples were frequently collected for comparison. Differences in DOM quality between sites and sampling methods were assessed using several common optical analyses. The analyses revealed significant differences in optical properties between sampling methods, with the passive samplers preferentially collecting terrestrial, humic-like DOM. We assert that the differences in DOM composition from each sampling method were caused by preferential binding of complex humic compounds to the DEAE cellulose in the passive samplers. Nonetheless, the passive samplers may provide a cost-effective, integrated sample of DOM in situations where the bulk DOM pool is composed mainly of terrestrial, humic-like compounds.

Roxarsone binding to soil-derived dissolved organic matter: Insights from multi-spectroscopic techniques.

PubMed

Fu, Qing-Long; He, Jian-Zhou; Blaney, Lee; Zhou, Dong-Mei

2016-07-01

The fate and transport of roxarsone (ROX), a widely used organoarsenic feed additive, in soil is significantly influenced by the ubiquitous presence of soil-derived dissolved organic matter (DOM). In this study, fluorescence quenching titration and two-dimensional correlation spectroscopy (2D-COS) were employed to study ROX binding to DOM. Binding mechanisms were revealed by fluorescence lifetime measurement and Fourier transform infrared spectroscopy (FTIR). Humic- and protein-like fluorophores were identified in the excitation-emission matrix and synchronous fluorescence spectra of DOM. The conditional stability constant (log KC) for ROX binding to DOM was found to be 5.06, indicating that ROX was strongly bound to DOM. The binding order of ROX to DOM fluorophores revealed by 2D-COS followed the sequence of protein-like fluorophore ≈ the longer wavelength excited humic-like (L-humic-like) fluorophore > the shorter wavelength excited humic-like (S-humic-like) fluorophore. 2D-COS resolved issues with peak overlapping and allowed further exploration of the interaction between ROX and DOM. Results of fluorescence lifetime and FTIR spectra demonstrated that ROX interacted with DOM through the hydroxyl, amide II, carboxyl, aliphatic CH, and NO2 groups, yielding stable DOM-ROX complexes. The strong interaction between ROX and DOM implies that DOM plays an important role in the environmental fate of ROX in soil. Copyright © 2016 Elsevier Ltd. All rights reserved.

Mesozoic to Eocene ductile deformation of western Central Iran: From Cimmerian collisional orogeny to Eocene exhumation

NASA Astrophysics Data System (ADS)

Kargaranbafghi, Fariba; Neubauer, Franz; Genser, Johann; Faghih, Ali; Kusky, Timothy

2012-09-01

To advance our understanding of the Mesozoic to Eocene tectonics and kinematics of basement units exposed in the south-western Central Iran plateau, this paper presents new structural and thermochronological data from the Chapedony metamorphic core complex and hangingwall units, particularly from the Posht-e-Badam complex. The overall Paleogene structural characteristics of the area are related to an oblique convergent zone. The Saghand area represents part of a deformation zone between the Arabian and Eurasian plates, and can be interpreted to result from the Central Iran intracontinental deformation acting as a weak zone during Mesozoic to Paleogene times. Field and microstructural evidence reveal that the metamorphic and igneous rocks suffered a ductile shear deformation including mylonitization at the hangingwall boundary of the Eocene Chapedony metamorphic core complex. Comparison of deformation features in the mylonites and other structural features within the footwall unit leads to the conclusion that the mylonites were formed in a subhorizontal shear zone by NE-SW stretching during Middle to Late Eocene extensional tectonics. The Chapedony metamorphic core complex is characterized by amphibolite-facies metamorphism and development of S and S-L tectonic fabrics. The Posht-e-Badam complex was deformed by two stages during Cimmerian tectonic processes forming the Paleo-Tethyan suture.

The problem of the age and structural position of the Blyb metamorphic complex (Fore Range zone, Great Caucasus) granitoids.

NASA Astrophysics Data System (ADS)

Kamzolkin, Vladimir; Latyshev, Anton; Ivanov, Stanislav

2016-04-01

The Blyb metamorphic complex (BMC) of the Fore Range zone is one of the most high-grade metamorphosed element of the Great Caucasus fold belt. Determination of the timing and the mechanism of formation of the Fore Range fold-thrust structures are not possible without investigation of the BMC located at the basement of its section. At the same time, the conceptions about its structure and age are outdated and need revision. Somin (2011) determined the age of the protolith and metamorphism of the Blyb complex as the Late Devonian - Early Carboniferous. We have recently shown that the BMC has not the dome, as previously thought, but nappe structure (Vidjapin, Kamzolkin, 2015), and is metamorphically coherent with the peak metamorphism pressures up to 22 kbar (Kamzolkin et al., 2015; Konilov et al., 2013). Considering the age and structure of the Blyb complex it is necessary to revise the age of granitoid intrusions and their relations with gneisses and schists, which constitute the main part of the section of the complex. Most authors (Gamkrelidze, Shengelia, 2007; Lavrischev, 2002; Baranov, 1967) adheres to Early Paleozoic age of intrusives, which is doubtful, considering the younger age of metamorphic rocks. We suppose, that the intrusive bodies broke through a BMC nappe structure during the exhumation of the complex (Perchuk, 1991) at the Devonian - Carboniferous boundary. Seemingly, the massive monzodiorites body (Lavrischev, 2002), intruding garnet-muscovite schists and amphibolite gneisses of the Blyb complex and cut by the Main Caucasian fault (MCF), are younger. Given the timing of termination of the MCF movement activity as the Middle Jurassic (Greater Caucasus..., 2005), their age should be in the Early Carboniferous - Middle Jurassic interval. At the same time, on the modern geological map (Lavrischev, 2002) monzodiorites body is assigned to the Middle Paleozoic. The study of the BMC granitoids and monzodiorites will help in determining of the mechanism and age of exhumation of the Blyb metamorphic complex high-pressure rocks. The reported study was partially supported by RFBR, research projects No. 16-35-00571mol_a; 16-05-01012a

Geology of the Biwabik Iron Formation and Duluth Complex.

PubMed

Jirsa, Mark A; Miller, James D; Morey, G B

2008-10-01

The Biwabik Iron Formation is a approximately 1.9 billion year-old sequence of iron-rich sedimentary rocks that was metamorphosed at its eastern-most extent by approximately 1.1 billion year-old intrusions of the Duluth Complex. The metamorphic recrystallization of iron-formation locally produced iron-rich amphiboles and other fibrous iron-silicate minerals. The presence of these minerals in iron-formation along the eastern part of what is known as the Mesabi Iron Range, and their potential liberation by iron mining has raised environmental health concerns. We describe here the geologic setting and mineralogic composition of the Biwabik Iron Formation in and adjacent to the contact metamorphic aureole of the Duluth Complex. The effects of metamorphism are most pronounced within a few kilometers of the contact, and decrease progressively away from it. The contact aureole has been divided into four metamorphic zones-each characterized by the composition and crystal structure of the metamorphic minerals it contains. The recrystallization of iron-formation to iron-rich amphibole minerals (grunerite and cummingtonite) and iron-pyroxene minerals (hedenbergite and ferrohypersthene) is best developed in zones that are most proximal to the Duluth Complex contact.

Geology of the Biwabik Iron Formation and Duluth Complex

USGS Publications Warehouse

Jirsa, M.A.; Miller, J.D.; Morey, G.B.

2008-01-01

The Biwabik Iron Formation is a ???1.9 billion year-old sequence of iron-rich sedimentary rocks that was metamorphosed at its eastern-most extent by ???1.1 billion year-old intrusions of the Duluth Complex. The metamorphic recrystallization of iron-formation locally produced iron-rich amphiboles and other fibrous iron-silicate minerals. The presence of these minerals in iron-formation along the eastern part of what is known as the Mesabi Iron Range, and their potential liberation by iron mining has raised environmental health concerns. We describe here the geologic setting and mineralogic composition of the Biwabik Iron Formation in and adjacent to the contact metamorphic aureole of the Duluth Complex. The effects of metamorphism are most pronounced within a few kilometers of the contact, and decrease progressively away from it. The contact aureole has been divided into four metamorphic zones-each characterized by the composition and crystal structure of the metamorphic minerals it contains. The recrystallization of iron-formation to iron-rich amphibole minerals (grunerite and cummingtonite) and iron-pyroxene minerals (hedenbergite and ferrohypersthene) is best developed in zones that are most proximal to the Duluth Complex contact. ?? 2007 Elsevier Inc. All rights reserved.

DOMstudio: an integrated workflow for Digital Outcrop Model reconstruction and interpretation

NASA Astrophysics Data System (ADS)

Bistacchi, Andrea

2015-04-01

Different Remote Sensing technologies, including photogrammetry and LIDAR, allow collecting 3D dataset that can be used to create 3D digital representations of outcrop surfaces, called Digital Outcrop Models (DOM), or sometimes Virtual Outcrop Models (VOM). Irrespective of the Remote Sensing technique used, DOMs can be represented either by photorealistic point clouds (PC-DOM) or textured surfaces (TS-DOM). The first are datasets composed of millions of points with XYZ coordinates and RGB colour, whilst the latter are triangulated surfaces onto which images of the outcrop have been mapped or "textured" (applying a tech-nology originally developed for movies and videogames). Here we present a workflow that allows exploiting in an integrated and efficient, yet flexible way, both kinds of dataset: PC-DOMs and TS-DOMs. The workflow is composed of three main steps: (1) data collection and processing, (2) interpretation, and (3) modelling. Data collection can be performed with photogrammetry, LIDAR, or other techniques. The quality of photogrammetric datasets obtained with Structure From Motion (SFM) techniques has shown a tremendous improvement over the past few years, and this is becoming the more effective way to collect DOM datasets. The main advantages of photogrammetry over LIDAR are represented by the very simple and lightweight field equipment (a digital camera), and by the arbitrary spatial resolution, that can be increased simply getting closer to the out-crop or by using a different lens. It must be noted that concerns about the precision of close-range photogrammetric surveys, that were justified in the past, are no more a problem if modern software and acquisition schemas are applied. In any case, LIDAR is a well-tested technology and it is still very common. Irrespective of the data collection technology, the output will be a photorealistic point cloud and a collection of oriented photos, plus additional imagery in special projects (e.g. infrared images). This dataset can be used as-is (PC-DOM), or a 3D triangulated surface can be interpolated from the point cloud, and images can be used to associate a texture to this surface (TS-DOM). In the DOMstudio workflow we use both PC-DOMs and TS-DOMs. Particularly, the latter are obtained projecting the original images onto the triangulated surface, without any downsampling, thus retaining the original resolution and quality of images collected in the field. In the DOMstudio interpretation step, PC-DOM is considered the best option for fracture analysis in outcrops where facets corresponding to fractures are present. This allows obtaining orientation statistics (e.g. stereoplots, Fisher statistics, etc.) directly from a point cloud where, for each point, the unit vector normal to the outcrop surface has been calculated. A recent development in this kind of processing is represented by the possibility to automatically select (segment) subset point clouds representing single fracture surfaces, which can be used for studies on fracture length, spacing, etc., allowing to obtain parameters like the frequency-length distribution, P21, etc. PC-DOM interpretation can be combined or complemented, depending on the outcrop morphology, with an interpretation carried out on a TS-DOM in terms of traces, which are the linear intersection of "geological" surfaces (fractures, faults, bedding, etc.) with the outcrop surface. This kind of interpretation is very well suited for outcrops with smooth surfaces, and can be performed either by manual picking, or by applying image analysis techniques on the images associated with the DOM. In this case, a huge mass of data, with very high resolution, can be collected very effectively. If we consider applications like lithological or mineral map-ping, TS-DOM datasets are the only suitable support. Finally, the DOMstudio workflow produces output in formats that are compatible with all common geomodelling packages (e.g. Gocad/Skua, Petrel, Move), allowing to directly use the quantitative data collected on DOMs to generate and calibrate geological, structural, or geostatistical models. I will present examples of applications including hydrocarbon reservoir analogue studies, studies on fault zone architecture, lithological mapping on sedimentary and metamorphic rocks, and studies on the surface of planets and small bodies in the Solar System.

Metamorphic facies map of Southeastern Alaska; distribution, facies, and ages of regionally metamorphosed rocks

USGS Publications Warehouse

Dusel-Bacon, Cynthia; Brew, D.A.; Douglass, S.L.

1996-01-01

Nearly all of the bedrock in Southeastern Alaska has been metamorphosed, much of it under medium-grade conditions during metamorphic episodes that were associated with widespread plutonism. The oldest metamorphisms affected probable arc rocks near southern Prince of Wales Island and occurred during early and middle Paleozoic orogenies. The predominant period of metamorphism and associated plutonism occurred during Early Cretaceous to early Tertiary time and resulted in the development of the Coast plutonic-metamorphic complex that extends along the inboard half of Southeastern Alaska. Middle Tertiary regional thermal metamorphism affected a large part of Baranof Island.

Comprehensive structure-selective characterization of dissolved organic matter by reducing molecular complexity and increasing analytical dimensions.

PubMed

Li, Yan; Harir, Mourad; Lucio, Marianna; Gonsior, Michael; Koch, Boris P; Schmitt-Kopplin, Philippe; Hertkorn, Norbert

2016-12-01

Deciphering the molecular codes of dissolved organic matter (DOM) improves our understanding of its role in the global element cycles and its active involvement in ecosystem services. This study demonstrates comprehensive characterization of DOM by an initial polarity-based stepwise solid phase extraction (SPE) with single methanol elution of the cartridges, but separate collection of equal aliquots of eluate. The reduction of molecular complexity in the individual DOM fractions attenuates intermolecular interactions and substantially increases the disposable resolution of any structure selective characterization. Suwannee River DOM (SR DOM) was used to collect five distinct SPE fractions with overall 91% DOC recovery. Optical spectroscopy (UV and fluorescence spectroscopy), high-field Fourier transform ion cyclotron mass spectrometry (FTICR MS) and nuclear magnetic resonance (NMR) spectroscopy showed analogous hierarchical clustering among the five eluates corroborating the robustness of this approach. Two abundant moderately hydrophobic fractions contained most of the SR DOM compounds, with substantial proportions of aliphatics, carboxylic-rich alicyclic molecules, carbohydrates and aromatics. A minor early eluting hydrophilic fraction was highly aliphatic and presented a large diversity of alicyclic carboxylic acids, whereas the two late eluting, minor hydrophobic fractions appeared as a largely defunctionalized mixture of aliphatic molecules. Comparative mass analysis showed that fractionation of SR DOM was governed by multiple molecular interactions depending on O/C ratio, molecular weight and aromaticity. The traditional optical indices SUVA 254 and fluorescence index (FI) indicated the relative aromaticity in agreement with FTICR mass and NMR spectra; the classical fluorescent peaks A and C were observed in all four latter eluates. This versatile approach can be easily expanded to preparative scale under field conditions, and transferred to different DOM sources and SPE conditions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Submarine hydrothermal metamorphism of the Del Puerto ophiolite, California.

USGS Publications Warehouse

Evarts, R.C.; Schiffman, P.

1983-01-01

Metamorphic zonation overprinted on the volcanic member and overlying volcanogenic sediments of the ophiolite complex increases downward in grade and is characterized by the sequential appearance with depth of zeolites, ferric pumpellyite and pistacitic epidote. Metamorphic assemblages of the plutonic member of the complex are characterized by the presence of calcic amphibole. The overprinting represents the effects of hydrothermal metamorphism resulting from the massive interaction between hot igneous rocks and convecting sea-water in a submarine environment. A thermal gradient of 100oC/km is postulated to account for the zonal recrystallization effects in the volcanic member. The diversity and sporadic distribution of mineral assemblages in the amphibole zone are considered due to the limited availability of H2O in the deeper part of the complex. Details of the zonation and representative microprobe analyses are tabulated.-M.S.

Distribution, Source and Fate of Dissolved Organic Matter in Shelf Seas

NASA Astrophysics Data System (ADS)

Carr, N.; Mahaffey, C.; Hopkins, J.; Sharples, J.; Williams, R. G.; Davis, C. E.

2016-02-01

Dissolved organic matter (DOM) is a complex array of molecules containing carbon (DOC), nitrogen (DON) and phosphorous (DOP), and represents the largest pool of organic matter in the marine environment. DOM in the sea originates from a variety of sources, including allochthonous inputs of terrestrial DOM from land via rivers, and autochthonous inputs through in-situ biotic processes that include phytoplankton exudation, grazing and cell lysis. Marine DOM is a substrate for bacterial growth and can act as a source of nutrients for autotrophs. However, a large component of DOM is biologically refractory. This pool is carbon-rich and nutrient-poor, and can transport and store its compositional elements over large areas and on long time scales. The role of DOM in the shelf seas is currently unclear, despite these regions acting as conduits between the land and open ocean, and also being highly productive ecosystems. Using samples collected across the Northwest European Shelf Sea, we studied the distribution, source, seasonality and potential fate of DOM using a combination of analytical tools, including analysis of amino acids, DOM absorbance spectra and excitation emission matrices, in conjunction with parallel factor analysis (PARAFAC). Strong cross shelf and seasonal gradients in DOM source and lability were found. We observed a strong seasonally dependent significant correlation between salinity and terrestrial DOM in the bottom mixed layer, an enrichment of DOM at the shelf edge in winter and a three-fold increase in fresh marine DOM coinciding with the timing of a spring bloom. Together, our findings illustrate the dynamic nature of DOM in shelf seas over a seasonal cycle and, highlight the potential for DOM to play a key role in the carbon cycle in these regions.

Sorptive and desorptive fractionation of dissolved organic matter by mineral soil matrices.

PubMed

Oren, Adi; Chefetz, Benny

2012-01-01

Interactions of dissolved organic matter (DOM) with soil minerals, such as metal oxides and clays, involve various sorption mechanisms and may lead to sorptive fractionation of certain organic moieties. While sorption of DOM to soil minerals typically involves a degree of irreversibility, it is unclear which structural components of DOM correspond to the irreversibly bound fraction and which factors may be considered determinants. To assist in elucidating that, the current study aimed at investigating fractionation of DOM during sorption and desorption processes in soil. Batch DOM sorption and desorption experiments were conducted with organic matter poor, alkaline soils. Fourier-transform infrared (FTIR) and UV-Vis spectroscopy were used to analyze bulk DOM, sorbed DOM, and desorbed DOM fractions. Sorptive fractionation resulted mainly from the preferential uptake of aromatic, carboxylic, and phenolic moieties of DOM. Soil metal-oxide content positively affected DOM sorption and binding of some specific carboxylate and phenolate functional groups. Desorptive fractionation of DOM was expressed by the irreversible-binding nature of some carboxylic moieties, whereas other bound carboxylic moieties were readily desorbed. Inner-sphere, as opposed to outer-sphere, ligand-exchange complexation mechanisms may be responsible for these irreversible, as opposed to reversible, interactions, respectively. The interaction of aliphatic DOM constituents with soil, presumably through weak van der Waals forces, was minor and increased with increasing proportion of clay minerals in the soil. Revealing the nature of DOM-fractionation processes is of great importance to understanding carbon stabilization mechanisms in soils, as well as the overall fate of contaminants that might be associated with DOM. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Factorial analysis of the trihalomethane formation in the reaction of colloidal, hydrophobic, and transphilic fractions of DOM with free chlorine.

PubMed

Platikanov, Stefan; Tauler, Roma; Rodrigues, Pedro M S M; Antunes, Maria Cristina G; Pereira, Dilson; Esteves da Silva, Joaquim C G

2010-09-01

This study focuses on the factors that affect trihalomethane (THMs) formation when dissolved organic matter (DOM) fractions (colloidal, hydrophobic, and transphilic fractions) in aqueous solutions were disinfected with chlorine. DOM fractions were isolated and fractionated from filtered lake water and were characterized by elemental analysis. The investigation involved a screening Placket-Burman factorial analysis design of five factors (DOM concentration, chlorine dose, temperature, pH, and bromide concentration) and a Box-Behnken design for a detailed assessment of the three most important factor effects (DOM concentration, chlorine dose, and temperature). The results showed that colloidal fraction has a relatively low contribution to THM formation; transphilic fraction was responsible for about 50% of the chloroform generation, and the hydrophobic fraction was the most important to the brominated THM formation. When colloidal and hydrophobic fraction solutions were disinfected, the most significant factors were the following: higher DOM fraction concentration led to higher THM concentration, an increase of pH corresponded to higher concentration levels of chloroform and reduced bromoform, higher levels of chlorine dose and temperature produced a rise in the total THM formation, especially of the chlorinated THMs; higher bromide concentration generates higher concentrations of brominated THMs. Moreover, linear models were implemented and response surface plots were obtained for the four THM concentrations and their total sum in the disinfection solution as a function of the DOM concentration, chlorine dose, and temperature. Overall, results indicated that THM formation models were very complex due to individual factor effects and significant interactions among the factors. In order to reduce the concentration of THMs in drinking water, DOM concentrations must be reduced in the water prior to the disinfection. Fractionation of DOM, together with an elemental analysis of the fractions, is important issue in the revealing of the quality and quantity characteristics of DOM. Systematic study composed from DOM fraction investigation and factorial analysis of the responsible parameters in the THM formation reaction can, after an evaluation of the adjustment of the models with the reality, serves well for the evaluation of the spatial and temporal variability in the THM formation in dependence of DOM. However, taking into consideration the natural complexity of DOM, different operations and a strict control of them (like coagulation/flocculation and filtration) has to be used to quantitatively remove DOM from the raw water. Assuming that this study represents a local case study, similar experiments can be easily applied and will supply with relevant information every local water treatment plant meeting problems with THM formation. The coagulation/flocculation and the filtration stages are the main mechanisms to remove DOM, particularly the colloidal DOM fraction. With the objective to minimize THMs generation, different unit operation designed to quantitatively remove DOM from water must be optimized.

Extending the analytical window for water-soluble organic matter in sediments by aqueous Soxhlet extraction

NASA Astrophysics Data System (ADS)

Schmidt, Frauke; Koch, Boris P.; Witt, Matthias; Hinrichs, Kai-Uwe

2014-09-01

Dissolved organic matter (DOM) in marine sediments is a complex mixture of thousands of individual constituents that participate in biogeochemical reactions and serve as substrates for benthic microbes. Knowledge of the molecular composition of DOM is a prerequisite for a comprehensive understanding of the biogeochemical processes in sediments. In this study, interstitial water DOM was extracted with Rhizon samplers from a sediment core from the Black Sea and compared to the corresponding water-extractable organic matter fraction (<0.4 μm) obtained by Soxhlet extraction, which mobilizes labile particulate organic matter and DOM. After solid phase extraction (SPE) of DOM, samples were analyzed for the molecular composition by Fourier Transform Ion-Cyclotron Resonance Mass Spectrometry (FT-ICR MS) with electrospray ionization in negative ion mode. The average SPE extraction yield of the dissolved organic carbon (DOC) in interstitial water was 63%, whereas less than 30% of the DOC in Soxhlet-extracted organic matter was recovered. Nevertheless, Soxhlet extraction yielded up to 4.35% of the total sedimentary organic carbon, which is more than 30-times the organic carbon content of the interstitial water. While interstitial water DOM consisted primarily of carbon-, hydrogen- and oxygen-bearing compounds, Soxhlet extracts yielded more complex FT-ICR mass spectra with more peaks and higher abundances of nitrogen- and sulfur-bearing compounds. The molecular composition of both sample types was affected by the geochemical conditions in the sediment; elevated concentrations of HS- promoted the early diagenetic sulfurization of organic matter. The Soxhlet extracts from shallow sediment contained specific three- and four-nitrogen-bearing molecular formulas that were also detected in bacterial cell extracts and presumably represent proteinaceous molecules. These compounds decreased with increasing sediment depth while one- and two-nitrogen-bearing molecules increased, resulting in a higher similarity of both sample types in the deep sediment. In summary, Soxhlet extraction of sediments accessed a larger and more complex pool of organic matter than present in interstitial water DOM.

Assembly of Functional Porous Solids in Complex Hybrid Composites

DTIC Science & Technology

2004-03-19

synthesis … 30 7.1.2 Grafting … 34 7.2 Surface functionalization of 3DOM oxide supports with polyelectrolytes and nanoparticles of another oxide … 34...incorporating hydrothermally prepared rutile/anatase nanoparticles (᝿ nm) within the walls of 3DOM silica, varying the titania content from ca. 0.5-20 wt... nanoparticles showing the bright colors that can be obtained and varied through synthesis parameters. 5.7 Effects of 3DOM particle sizes on optical

Spectroscopic study of interactions of lead (II) ions with dissolved organic matter: Evidence of preferential engagement of carboxylic groups

NASA Astrophysics Data System (ADS)

Lu, Yujuan; Yan, Mingquan; Korshin, Gregory V.

2017-09-01

The speciation, bioavailability and transport of Pb(II) in the environment are strongly affected by dissolved organic matter (DOM). Despite the importance of these interactions, the nature of Pb(II)-DOM binding is insufficiently attested. This study addressed this deficiency using the method of differential absorbance spectroscopy in combination with the non-ideal competitive adsorption (NICA)-Donnan model. Differential absorbance data allowed quantifying the interactions between Pb(II) and DOM in a wide range of pH values, ionic strengths and Pb(II) concentrations at an environmentally relevant DOM concentration (5 mg L-1). Changes of the slopes of the log-transformed absorbance spectra of DOM in the range of wavelength 242-262 and 350-400 nm were found to be predictive of the extent of Pb(II) bound by DOM carboxylic groups and of the total amount of DOM-bound Pb(II), respectively. The results also demonstrated the preferential involvement of DOM carboxylic groups in Pb(II) binding. The spectroscopic data allowed optimizing selected Pb(II)-DOM complexation constants used in the NICA-Donnan Model. This resulted in a markedly improved performance of that model when it was applied to interpret previously published Pb(II)-fulvic acid datasets.

Ecosystem consequences of changing inputs of terrestrial dissolved organic matter to lakes: current knowledge and future challenges

USGS Publications Warehouse

Solomon, Christopher T.; Jones, Stuart E.; Weidel, Brian C.; Buffam, Ishi; Fork, Megan L; Karlsson, Jan; Larsen, Soren; Lennon, Jay T.; Read, Jordan S.; Sadro, Steven; Saros, Jasmine E.

2015-01-01

Lake ecosystems and the services that they provide to people are profoundly influenced by dissolved organic matter derived from terrestrial plant tissues. These terrestrial dissolved organic matter (tDOM) inputs to lakes have changed substantially in recent decades, and will likely continue to change. In this paper, we first briefly review the substantial literature describing tDOM effects on lakes and ongoing changes in tDOM inputs. We then identify and provide examples of four major challenges which limit predictions about the implications of tDOM change for lakes, as follows: First, it is currently difficult to forecast future tDOM inputs for particular lakes or lake regions. Second, tDOM influences ecosystems via complex, interacting, physical-chemical-biological effects and our holistic understanding of those effects is still rudimentary. Third, non-linearities and thresholds in relationships between tDOM inputs and ecosystem processes have not been well described. Fourth, much understanding of tDOM effects is built on comparative studies across space that may not capture likely responses through time. We conclude by identifying research approaches that may be important for overcoming those challenges in order to provide policy- and management-relevant predictions about the implications of changing tDOM inputs for lakes.

Inheritance, Variscan tectonometamorphic evolution and Permian to Mesozoic rejuvenations in the metamorphic basement complexes of the Romanian Carpathians revealed by monazite microprobe geochronology

NASA Astrophysics Data System (ADS)

Săbău, Gavril; Negulescu, Elena

2014-05-01

Monazite U-Th-Pb chemical dating reaches an acceptable compromise between precision and accuracy on one side, and spatial resolution and textural constraints on the other side. Thus it has a powerful potential in testing the coherence of individual metamorphic basement units, and enabling correlations among them. Yet, sensitivity and specificity issues in monazite response to thermotectonic events, especially in the case of superposed effects, remain still unclear. Monazite dating at informative to detailed scale in the main metamorphic basement units of the Carpathians resulted in complex age spectra. In the main, the spectra are dominated by the most pervasive thermal and structural overprint, as checked against independent geochronological data. Post-peak age resetting is mostly present, but statistically subordinate. Resetting in case of superposed events is correlated with the degree of textural and paragenetic overprinting, inheritances being always indicated by more or less well-defined age clusters. The lack of relict ages correlating with prograde structural and porphyroblast zonation patterns is indicative for juvenile formations. Age data distribution in the Carpathians allowed distinction of pre-Variscan events, syn-metamorphic Variscan tectonic stacking of juvenile and reworked basement, post-Variscan differential tectonic uplift, as well as prograde metamorphic units ranging down to Upper Cretaceous ages. In the South Carpathians, the Alpine Danubian domain consists of several Variscan and Alpine thrust sheets containing a metamorphic complex dominated by Upper Proterozoic to Lower Cambrian metamorphic and magmatic ages (Lainici-Păiuş), and several complexes with metamorphic overprints ranging from Carboniferous to Lower Permian. Any correlation among these units, as well as geotectonic models placing a Lower Paleozoic oceanic domain between pre-existing Lainici-Păiuş and Drăgşan terranes are precluded by the age data. Other basement of the South Carpathians contain lower Paleozoic or older units intruded by Ordovician granitoids, imbricated with juvenile Variscan slivers, the structural sequence differing in individual basement complexes. So, in the Leaota Massif the lowermost term of the sequence is prograde Variscan, tectonically overlain by reworked lower Paleozoic gneisses, supporting thrust sheets with very low- to low-grade Variscan schists. In the Făgăraş Massif a lower Paleozoic (Cumpăna) complex bearing a strong Variscan overprint, straddles Variscan juvenile rocks, and the lowermost visible structural level is assumed by upper Carboniferous to Permian juvenile medium-grade metamorphic schists. In the Lotru Metamorphic Suite of the Alpine Getic Nappe, the Variscan stacking is overprinted by post-orogenic differential uplift, documented by the correlation among younging ages, structural and metamorphic low-pressure overprints, recording often higher metamorphic temperatures. The most spectacular structure is Upper Jurassic in age, contains high-grade metamorphic rocks and peraluminous anatectic granitoids, is outlined by a deformed boundary evolving from ductile to brittle regime during cooling, and induces a thermal overprint in the neighbouring rocks. In the basement units thrust over the Getic Nappe, the Sibişel unit yielded Permian prograde peak metamorphic ages and Triassic post-peak overprints, while an adjacent gneissic unit (Laz) delivered an exclusively Cretaceous age pattern. Unexpectedly young metamorphic ages resulted also for the East Carpathians and the Apuseni Mountains. While most of the ages obtained so far correspond to Variscan retrogression of older basement units, the lowermost structural unit of the infra-Bucovinian nappe system in the East Carpathians yielded Upper Cretaceous metamorphic ages in apparently monometamorphic medium-grade schists. In the Apuseni Mountains, schists of the Baia de Arieş Unit display an Upper Jurassic age spectrum, corresponding to a clearly prograde medium-grade event. The ages recorded not only question some of the currently accepted correlations among basement units, but urge to reconsideration of the way in which the basement-cover relationships are interpreted and extrapolated.

The river as a chemostat: fresh perspectives on dissolved organic matter flowing down the river continuum

USGS Publications Warehouse

Creed, Irena F.; McKnight, Diane M.; Pellerin, Brian; Green, Mark B.; Bergamaschi, Brian; Aiken, George R.; Burns, Douglas A.; Findlay, Stuart E G; Shanley, James B.; Striegl, Robert G.; Aulenbach, Brent T.; Clow, David W.; Laudon, Hjalmar; McGlynn, Brian L.; McGuire, Kevin J.; Smith, Richard A.; Stackpoole, Sarah M.

2015-01-01

A better understanding is needed of how hydrological and biogeochemical processes control dissolved organic carbon (DOC) concentrations and dissolved organic matter (DOM) composition from headwaters downstream to large rivers. We examined a large DOM dataset from the National Water Information System of the US Geological Survey, which represents approximately 100 000 measurements of DOC concentration and DOM composition at many sites along rivers across the United States. Application of quantile regression revealed a tendency towards downstream spatial and temporal homogenization of DOC concentrations and a shift from dominance of aromatic DOM in headwaters to more aliphatic DOM downstream. The DOC concentration–discharge (C-Q) relationships at each site revealed a downstream tendency towards a slope of zero. We propose that despite complexities in river networks that have driven many revisions to the River Continuum Concept, rivers show a tendency towards chemostasis (C-Q slope of zero) because of a downstream shift from a dominance of hydrologic drivers that connect terrestrial DOM sources to streams in the headwaters towards a dominance of instream and near-stream biogeochemical processes that result in preferential losses of aromatic DOM and preferential gains of aliphatic DOM.

Paleomagnetic and Tectonic studies in Uruguay: a brief synthesis of the last decade

NASA Astrophysics Data System (ADS)

Sanchez Bettucci, L.

2013-05-01

The paleomagnetic studies in Uruguay have been applied as a complementary tool to geological studies. Paleomagnetic data can be very useful for geodynamic reconstructions, fundamentally for determine the latitudinal tectonic transport, rotations of crustal blocks. This technique has been applied to Paleoproterozoic, Neoproterozoic and Paleozoic units. The geology of the Uruguayan territory is divided into four tectonic units of Uruguay that include a) the Piedra Alta tectonostratigraphic terrane (PATT) and b) Nico Pérez tectonostratigraphic terrane (NPTT), separated by the Sarandí del Yí high-strain zone. Both terranes are well exposed in the Río de La Plata craton (RPC) and have paleoproterozoic ages, the last was reworked in Neoproterozoic times (metacraton). The most thoroughly investigated Neoproterozoic sections are located in the eastern and southeastern regions of Uruguay. The c) Dom Feliciano Belt shows a tectonic evolution from back-arc to foreland basin characterized by fold-and-thrust, thick-skinned belts developed during the Brasiliano/Pan-African orogenic cycle. And finally d) The high metamorphic grade Punta del Este terrane where its most notable feature is their African affinity. There is a significant shortage of geochemical and geochronological data for the existing geological complexity.

Metamorphism, P-T-t Conditions of Formation, and Prospects for the Practical Use of Al2SiO5 Polymorphs, Chloritoid, and Staurolite (Yenisei Ridge)

NASA Astrophysics Data System (ADS)

Kozlov, P. S.

2017-12-01

The Yenisei Ridge is an accretion-collisional orogen located in the southwestern frame of the Siberian Craton in the interfluve between Podkamennaya Tunguska, Angara, Kan, and Yenisei rivers. The Precambrian mono- and polymetamorphic complexes composed predominantly of the Mesoarchean-Neoproterozoic metapelitic rocks have been studied. Based on the typification of metamorphic complexes by pressure, temperature, metamorphic gradient, as well as age of metamorphism, the location scheme of the fields of the Precambrian sedimentary-metamorphic rock which are prospective for searching deposits of high-alumina metamorphic minerals (andalusite, kyanite, and sillimanite, chloritoid, and staurolite) in the Trans-Angara segment of the Yenisei Region, was compiled. The Teya sillimanite and Panimbinsk andalusite deposits, which are confined to the fields of regional metamorphic complexes of iron-alumina metapelites of the And-Sill facies series, are recommended as a priority for the organization of prospecting works and the subsequent involvement to the metallurgical industry. These metapelites are classified as monomineral. Owing to widespread occurrence and abundance of andalusite and sillimanite, the above deposits have significant inferred resources. Stratiform deposits of garnet-staurolite and chloritoid high-alumina rocks are still insufficiently studied and should be investigated further. The prospects for the possible use of high-alumina andalusite and sillimanite together with Middle Tatarka and Kiya nepheline syenite massifs and the bauxites of the Chadobets uplift, already being explored in the region, for production of aluminum oxide, silumin, and aluminum, as well as, the prospects for the expansion of the raw material base of the Boguchansk Electrometallurgical Complex, brought into operation in 2016 in the Lower Angara region, are considered.

Textural and isotopic development of marble assemblages during the Barrovian-style M2 metamorphic event, Naxos, Greece

NASA Astrophysics Data System (ADS)

Baker, Judy; Matthews, Alan

1994-03-01

A detailed petrological analysis of the marble assemblages observed within the M2 metamorphic complex on Naxos is presented. Two distinct periods of mineral growth are documented; the first is associated with prograde M2 metamorphism and the second with retrograde M2 metamorphism occurring during ductile extensional thinning of the complex. The textural and miner-alogical characteristics and the carbon and oxygen isotope compositions of each generation are described, and the P-T-X CO 2 conditions at which these two mineral generations were stable, and the compositions of the fluids present during metamorphism are characterised. Whereas the low variance and stable isotope compositions of prograde siliceous dolomite assemblages are consistent with internally buffered fluid evolution, the retrograde mineral generation is shown to have grown as a result of the infiltration of a water-rich fluid phase that transported silica, Al2O3, Na2O and FeO into the host rocks. This observation, together with the stable isotope compositions of the retrograde calcite, and the fact that occurrences of veins of this type are limited to marbles in the highest grade areas ( T>600° C) of the metamorphic complex, suggests that the fluids responsible for vein formation were generated during the crystallisation of melts as the metamorphic complex cooled from peak temperatures. The existence of this second generation of minerals has significant implications for previous studies of heat transport by fluid flow on Naxos, because many of the unusually low δ18O compositions of pelites at high grades may be ascribable to the effects of interaction with retrograde M2 fluids, rather than with prograde fluids.

Co-precipitation of dissolved organic matter by calcium carbonate in Pyramid Lake, Nevada

USGS Publications Warehouse

Leenheer, Jerry A.; Reddy, Michael M.

2008-01-01

Our previous research has demonstrated that dissolved organic matter (DOM) influences calcium carbonate mineral formation in surface and ground water. To better understand DOM mediation of carbonate precipitation and DOM co-precipitation and/or incorporation with carbonate minerals, we characterized the content and speciation of DOM in carbonate minerals and in the lake water of Pyramid Lake, Nevada, USA. A 400-gram block of precipitated calcium carbonate from the Pyramid Lake shore was dissolved in 8 liters of 10% acetic acid. Particulate matter not dissolved by acetic acid was removed by centrifugation. DOM from the carbonate rock was fractionated into nine portions using evaporation, dialysis, resin adsorption, and selective precipitations to remove acetic acid and inorganic constituents. The calcium carbonate rock contained 0.23% DOM by weight. This DOM was enriched in polycarboxylic proteinaceous acids and hydroxy-acids in comparison with the present lake water. DOM in lake water was composed of aliphatic, alicyclic polycarboxylic acids. These compound classes were found in previous studies to inhibit calcium carbonate precipitation. DOM fractions from the carbonate rock were 14C-age dated at about 3,100 to 3,500 years before present. The mechanism of DOM co-precipitation and/or physical incorporation in the calcium carbonate is believed to be due to formation of insoluble calcium complexes with polycarboxylic proteinaceous acids and hydroxy-acids that have moderately large stability constants at the alkaline pH of the lake. DOM co-precipitation with calcium carbonate and incorporation in precipitated carbonate minerals removes proteinaceous DOM, but nearly equivalent concentrations of neutral and acidic forms of organic nitrogen in DOM remain in solution. Calcium carbonate precipitation during lime softening pretreatment of drinking water may have practical applications for removal of proteinaceous disinfection by-product precursors.

Multiple tectonic mode switches indicate short-duration heat pulses in a Mio-Pliocene metamorphic core complex, West Papua, Indonesia

NASA Astrophysics Data System (ADS)

White, L. T.; Hall, R.; Gunawan, I.

2017-12-01

The Wandaman Peninsula is a narrow (<20 km), but mountainous (>2 km) promontory in remote western New Guinea. The peninsula is almost entirely composed of medium- to high-grade metamorphic rocks considered to be associated with a Mio-Pliocene metamorphic core complex. Previous work has shown that the uplift and exhumation of the core complex has potentially brought some extremely young eclogite to the surface. These might be comparable to the world's youngest (4.3 Ma) eclogites found in the D'Entrecasteaux Islands at the opposite end of New Guinea. We show that tectonic history of this region is complex. This is because the metamorphic sequences in the Wandaman Peninsula record multiple phases of deformation, all within the last few million years. This is demonstrated through methodical collation of cross-cutting relations from field and microstructural studies across the peninsula. The first phase of deformation and metamorphism is associated with crustal extension and partial melting that took place at 5-7 Ma according to new U-Pb data from metamorphic zircons. This extensional phase ceased after a tectonic mode switch and the region was shortened. This is demonstrated by two phases of folding (1. recumbent and 2. open) that overprint the earlier extensional fabrics. All previous structures were later overprinted by brittle extensional faults and uplift. This extensional phase is still taking place today, as is indicated by submerged forests exposed along the coastline associated with recent earthquakes and hot springs. The sequence of metamorphic rocks that are exposed in the Wandaman Peninsula show that stress and thermal conditions can change rapidly. If we consider that the present is a key to the past, then such results can identify the duration of deformation and metamorphic events more accurately than in much older orogenic systems.

Non-riverine pathways of terrigenous carbon to the ocean

NASA Astrophysics Data System (ADS)

Dittmar, T.

2007-12-01

The extent and nature of non-riverine fluxes of carbon from land to ocean are poorly understood. Tidal pumping from highly productive coastal environments, atmospheric deposition and submarine groundwater discharge can be significant transport mechanisms for carbon to the ocean. Evidence is mounting that tidally-induced porewater fluxes ("outwelling") of dissolved organic matter (DOM) from mangroves and salt marshes alone may be similar in magnitude as the global riverine flux of DOM. Tidal pumping of dissolved inorganic carbon (DIC) might exceed organic carbon fluxes by far, but the existing knowledge on DIC outwelling is too scarce for a first global estimate. Results from two case studies on the biogeochemistry of DOM outwelling are presented, from the mangroves in Northern Brazil and the salt marshes in the Northern Gulf of Mexico. Ongoing research in the Northern Gulf of Mexico indicates that outwelling and groundwater inputs probably exceed riverine DOM fluxes in this region. Similar observations were made in Northern Brazil. There, the fate of mangrove-derived DOM could be traced from its source in the mangrove sediments to the outer North Brazil shelf by using a combination of isotopic and molecular approaches. Reversed-phase liquid chromatography / mass spectrometry (LC/MS) provided a multifaceted array of information that mirrors the molecular complexity of DOM. Statistical analyses on these data revealed significant differences between mangrove and open-ocean DOM which successively disappeared by irradiating the samples with natural sunlight. Nuclear magnetic resonance analyses yielded concurrent results. Ultrahigh-resolution Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) is the only technique capable of resolving and identifying individual elemental compositions in these complex mixtures. We applied this technique for characterizing mangrove-derived DOM and to assess the molecular changes that occur in the initial stages of outwelling. The different approaches concordantly show the presence of photodegraded mangrove DOM on the North Brazil shelf. During transport offshore, sunlight efficiently destroyed aromatic molecules, removing about one third of mangrove-derived DOM. The remainder was refractory and may thus be distributed over the oceans.

Tectono-stratigraphy and low-grade metamorphism of Late Permian and Early Jurassic accretionary complexes within the Kurosegawa belt, Southwest Japan: Implications for mechanisms of crustal displacement within active continental margin

NASA Astrophysics Data System (ADS)

Hara, Hidetoshi; Kurihara, Toshiyuki; Mori, Hiroshi

2013-04-01

We characterize the tectono-stratigraphic architecture and low-grade metamorphism of the accretionary complex preserved in the Kurosegawa belt of the Kitagawa district in eastern Shikoku, Southwest Japan, in order to understand its internal structure, tectono-metamorphic evolution, and assessments of displacement of continental fragments within the complex. We report the first ever documented occurrence of an Early Jurassic radiolarian assemblage within the accretionary complex of the Kurosegawa belt that has been previously classified as the Late Permian accretionary complex, thus providing a revised age interpretation for these rocks. The accretionary complex is subdivided into four distinct tectono-stratigraphic units: Late Permian mélange and phyllite units, and Early Jurassic mélange and sandstone units. The stratigraphy of these four units is structurally repeated due to an E-W striking, steeply dipping regional fault. We characterized low-grade metamorphism of the accretionary complex via illite crystallinity and Raman spectroscopy of carbonaceous material. The estimated pattern of low-grade metamorphism showed pronounced variability within the complex and revealed no discernible spatial trends. The primary thermal structure in these rocks was overprinted by later tectonic events. Based on geological and thermal structure, we conclude that continental fragments within the Kurosegawa belt were structurally translated into both the Late Permian and Early Jurassic accretionary complexes, which comprise a highly deformed zone affected by strike-slip tectonics during the Early Cretaceous. Different models have been proposed to explain the initial structural evolution of the Kurosegawa belt (i.e., micro-continent collision and klippe tectonic models). Even if we presuppose either model, the available geological evidence requires a new interpretation, whereby primary geological structures are overprinted and reconfigured by later tectonic events.

Mercury reduction and complexation by natural organic matter in anoxic environments.

PubMed

Gu, Baohua; Bian, Yongrong; Miller, Carrie L; Dong, Wenming; Jiang, Xin; Liang, Liyuan

2011-01-25

Mercuric Hg(II) species form complexes with natural dissolved organic matter (DOM) such as humic acid (HA), and this binding is known to affect the chemical and biological transformation and cycling of mercury in aquatic environments. Dissolved elemental mercury, Hg(0), is also widely observed in sediments and water. However, reactions between Hg(0) and DOM have rarely been studied in anoxic environments. Here, under anoxic dark conditions we show strong interactions between reduced HA and Hg(0) through thiolate ligand-induced oxidative complexation with an estimated binding capacity of ~3.5 μmol Hg/g HA and a partitioning coefficient >10(6) mL/g. We further demonstrate that Hg(II) can be effectively reduced to Hg(0) in the presence of as little as 0.2 mg/L reduced HA, whereas production of Hg(0) is inhibited by complexation as HA concentration increases. This dual role played by DOM in the reduction and complexation of mercury is likely widespread in anoxic sediments and water and can be expected to significantly influence the mercury species transformations and biological uptake that leads to the formation of toxic methylmercury.

The chemical composition and source identification of soil dissolved organic matter in riparian buffer zones from Chongming Island, China.

PubMed

Wang, Yulai; Yang, Changming; Li, Jianhua; Shen, Shuo

2014-09-01

Dissolved organic matter (DOM) that is derived from the soil of riparian buffer zones has a complex chemical composition, and it plays an important role in the transport and transformation of pollutants. To identify the source of DOM and to better understand its chemical and structural properties, we collected 33 soil samples from zones with fluctuating water levels along the major rivers on Chongming Island, evaluated the DOM contents in riparian soil, analyzed the chemical composition and functional groups and traced DOM origins by using liquid chromatography quadrupole time-of-flight mass spectrometry (LC-Q-TOF-MS) combined with clustering analysis. All sampling sites were divided into four groups by principal component analysis (PCA) on the basis of the DOM molecules. The results showed that there was no significant difference in the DOM contents between every two groups; however, the DOM fractions differed significantly among the different site groups in the following order: Σ lipids and Σ proteins>Σ sugars and Σ fatty acids>Σ amino acids, Σ indoles and Σ alkaloids. DOM in the riparian buffer zones originated from riparian plants, domestic sewage and agricultural activities, and the hydrophobic and amphiphilic fractions accounting for over 60% of the identified molecules were the dominant fractions. Our study has confirmed the heterogeneous properties of DOM, and it is of vital importance to isolate and characterize the various DOM fractions at the molecular level for a better understanding of the behavior and roles of DOM in the natural environment. Copyright © 2014 Elsevier Ltd. All rights reserved.

Source and Processes of Dissolved Organic Matter in a Bangladesh Groundwater

NASA Astrophysics Data System (ADS)

McKnight, D. M.; Simone, B. E.; Mladenov, N.; Zheng, Y.; Legg, T. M.; Nemergut, D.

2010-12-01

Arsenic contamination of groundwater is a global health crisis, especially in Bangladesh where an estimated 40 million people are at risk. The release of geogenic arsenic bound to sediments into groundwater is thought to be influenced by dissolved organic matter (DOM) through several biogeochemical processes. Abiotically, DOM can promote the release of sediment bound As through the formation of DOM-As complexes and competitive interactions between As and DOM for sorption sites on the sediment. Additionally, the labile portion of groundwater DOM can serve as an electron donor to support microbial growth and the more recalcitrant humic DOM may serve as an electron shuttle, facilitating the eventual reduction of ferric iron present as iron oxides in sediments and consequently the mobilization of sorbed As and organic material. The goal of this study is to understand the source of DOM in representative Bangladesh groundwaters and the DOM sorption processes that occur at depth. We report chemical characteristics of representative DOM from a surface water, a shallow low-As groundwater, mid-depth high-As groundwater from the Araihazar region of Bangladesh. The humic DOM from groundwater displayed a more terrestrial chemical signature, indicative of being derived from plant and soil precursor materials, while the surface water humic DOM had a more microbial signature, suggesting an anthropogenic influence. In terms of biogeochemical processes occurring in the groundwater system, there is evidence from a diverse set of chemical characteristics, ranging from 13C-NMR spectroscopy to the analysis of lignin phenols, for preferential sorption onto iron oxides influencing the chemistry and reactivity of humic DOM in high As groundwater in Bangladesh. Taken together, these results provide chemical evidence for anthropogenic influence and the importance of sorption reactions at depth controlling the water quality of high As groundwater in Bangladesh.

A Sociolinguistic Study of Differential Object Marking (DOM) in Two Varieties of Contemporary Spanish

ERIC Educational Resources Information Center

Balasch Rodriguez, Sonia

2011-01-01

This sociolinguistic-variationist investigation sheds light on two little-studied issues concerning Spanish DOM, or variable use of a before animate "direct objects" (DOs), in vernacular language: the complex interaction of co-occurring linguistic (type of verb; definiteness, specificity, grammatical number, topicality, type and…

Application of fluorescence spectroscopy for dissolved organic matter characterization in constructed wetlands

NASA Astrophysics Data System (ADS)

Sardana, A.; Aziz, T. N.; Cottrell, B. A.

2017-12-01

In this presentation we will discuss our ongoing work to characterize the photochemical behavior of dissolved organic matter (DOM) from wastewater treated in constructed wetlands. We have used a suite of spectroscopic and chromatographic techniques to characterize the DOM and to quantify the potential production of reactive oxygenated species (ROS). In the present study, DOM was fractionated based on its hydrophobicity and both the natural water isolates and fractionated DOM were characterized using SUVA254, spectral slope ratios, excitation emission matrix fluorescence spectroscopy (EEMs) and proton nuclear magnetic resonance (1H NMR). Photodegradation of wetland DOM and the formation of the hydroxyl radical (*OH), singlet oxygen (1O2), and the triplet-excited state (3DOM*) was also determined to assess the reactivity of DOM. EEM spectra exhibited the four main fluorescence peaks that are characteristic of DOM: peak A humic-like DOM, Peak C (fulvic or chromophoric DOM), Peak M (marine-like DOM), and peak T (tryptophan or protein-like absorbance). Two additional observed peaks with shorter emission wavelengths (A' Ex/Em = 243/278 nm and T' Ex/Em = 272/319 nm) were attributed to the microbial DOM in wastewater effluent. The spectral slope ratios decreased from 1.46 at the wetland inlet to 0.89 at the wetland outlet. The protein-like Peak T fluorescence decreased from 50% at the wetland inlet to 6.7% at the Wetland 2 outlet. A negative correlation between the percent fluorescence of Peak T and Peaks A, C and M confirmed the transition from the spectrum of pure wastewater with a primarily protein-like signature to a spectrum characteristic of terrestrially derived DOM. This transition coincided with enhanced formation rates and steady state concentrations of photochemically produced reactive intermediates (PPRIs). Size Exclusion Chromatography demonstrated that the influent wastewater had a lower molecular weight as compared to downstream wetland locations. Fractionation of DOM based on hydrophobicity followed by 1H NMR analysis indicated an increase in the complexity and composition of wetland effluent DOM. This presentation will summarize these findings and present results from our new microcosm constructed wetlands built to develop insights into DOM production and photochemical characteristics.

Peak Metamorphic Temperature Profile across Eastern Belt Franciscan, Northern California Coast Ranges

NASA Astrophysics Data System (ADS)

Schmidt, W. L.; Platt, J. P.

2017-12-01

Previous work done on metamorphic temperatures across the lawsonite-albite to blueschist facies rocks of the Eastern Belt of the Franciscan accretionary complex has relied on a combination of many methods, and suggests that temperature broadly increases from west to east. The Taliaferro Metamorphic Complex is an exception to this pattern and shows higher pressures, and possibly higher temperatures, than its surroundings. The exact location and nature of the faults separating accreted packets in the Eastern Belt is somewhat controversial. A recently calibrated low-temperature laser Raman geothermometer for use on carbonaceous material provides a uniform method of estimating peak metamorphic temperature across the eastern Franciscan and is here used to identify the position of major tectonic boundaries. Temperatures were obtained from exposures in Thomes Creek, Cottonwood Creek, Grindstone Creek, and the middle fork of the Eel River. Peak T in the South Fork Mountain Schist, the highest grade and easternmost unit in the Franciscan, is 310-375°C, whereas in immediately underlying lawsonite-albite facies rocks below the Log Springs thrust, peak T is 270 - 300°C. The Taliaferro Metamorphic Complex reached a peak temperature of 336°C, whereas the surrounding lawsonite-albite facies rocks yield peak temperatures as low as 232°C. Preliminary temperature profiles clearly allow the major faults bounding the Taliaferro Metamorphic Complex and the South Fork Mountain Schist to be located. Extension of the temperature profile has the potential to reveal further detail within these units and the lower grade rocks surrounding them.

Implications of effluent organic matter and its hydrophilic fraction on zinc(II) complexation in rivers under strong urban pressure: aromaticity as an inaccurate indicator of DOM-metal binding.

PubMed

Louis, Yoann; Pernet-Coudrier, Benoît; Varrault, Gilles

2014-08-15

The zinc binding characteristics of dissolved organic matter (DOM) fractions from the Seine River Basin were studied after being separated and extracted according to their polarity: hydrophobic, transphilic, and hydrophilic. The applied experimental methodology was based on a determination of labile zinc species by means of differential pulse anodic stripping voltammetry (DPASV) at increasing concentrations of total zinc on a logarithmic scale and at fixed levels of: pH, ionic strength, and temperature. Fitting the DOM fractions with two discrete classes of ligands successfully allowed determining the conditional zinc binding constants (Ki) as well as total ligand density (LiT). The binding constants obtained for each DOM fraction were then compared and discussed with respect to the hydrophobic/hydrophilic nature and sample origin. Results highlighted a strong complexation of zinc to the effluent organic matter and especially the most hydrophilic fraction, which also displayed a very low specific UV absorbance. Although the biotic ligand model takes into account the quality of DOM through UV absorbance in the predictions of metal bioavailability and toxicity, this correction is not efficient for urban waters. Copyright © 2014 Elsevier B.V. All rights reserved.

Metamorphic P-T evolution of the Gotsu blueschists from the Suo metamorphic belt in SW Japan: Implications for tectonic correlation with the Heilongjiang Complex, NE China

NASA Astrophysics Data System (ADS)

Kabir, Md. Fazle; Takasu, Akira; Li, Weimin

2018-05-01

In the Gotsu area of the c. 200 Ma high-P/T Suo metamorphic belt in the Inner Zone of southwest Japan, blueschists occur as lenses or layers within pelitic schists. Prograde, peak, and retrograde stages are distinguished in the blueschists, and the prograde and the peak metamorphic conditions are determined using pseudosection modelling in the NCKFMASHO system. The prograde metamorphic stage is defined by inclusions in porphyroblastic epidote and glaucophane, such as phengite, chlorite, albite, epidote and glaucophane/winchite, and the estimated metamorphic conditions are <325 °C and < 4-5 kbar at the boundary between the glaucophane schist facies and the greenschist facies. The peak metamorphic stage is well-defined by the schistosity-forming minerals, i.e. epidote, glaucophanic amphibole, phengite, and chlorite, suggesting the glaucophane schist facies conditions of 475-500 °C and 14-16 kbar. Actinolite/magnesiohornblende, chlorite, and albite replacing the peak stage minerals suggest the retrograde metamorphism into the greenschist facies. The metamorphic facies series of the Suo belt is defined by pumpellyite-actinolite facies to epidote-blueschist facies, and it has a relatively lower-P/T compared with the c. 300 Ma Renge belt in the Inner Zone of southwest Japan, which is defined by a sequence of lawsonite-blueschist facies to glaucophane-eclogite facies. The P- {M}_{{H}_2O} pseudosection and water isopleth show that the rocks were dehydrated during the initial stage of the exhumation and remained in water-saturated conditions. Similarities of the detrital zircon and peak metamorphic ages of the blueschists from the Suo metamorphic belt in southwest Japan and the Heilongjiang Complex in northeast China suggest that both metamorphic belts were probably formed in the same Paleo-Pacific subduction system in the Late Triassic to Jurassic period.

High field NMR Spectroscopy and FTICR Mass Spectrometry: Powerful Discovery Tools for the Characterization of Marine Dissolved Organic Matter

NASA Astrophysics Data System (ADS)

Hertkorn, N.; Harir, M.; Koch, B. P.; Michalke, B.; Grill, P.; Schmitt-Kopplin, P.

2012-04-01

High-field NMR and FTMS of SPE-derived marine dissolved organic matter (SPE-DOM) from the South Atlantic Ocean provided molecular level information of complex unknowns with unprecedented coverage of carbon and resolution. SPE-DOM represented major oceanic regimes of general significance: 5 m (near surface photic zone), 48 m (fluorescence maximum), 200 m (upper mesopelagic zone) and 5446 m (30 m above ground). 1H NMR spectra showed rather smooth bulk NMR envelopes with a few percent of visibly resolved signatures. 1H NMR spectra of SPE-DOM indicated considerable variance in abundance for all major chemical environments. Two-dimensional NMR spectra of SPE-DOM displayed exceptional resolution. JRES (sensitive but limited resolution), COSY (highly resolved) and HMBC NMR (informative but limited S/N ratio) spectra depicted resolved molecular signatures in excess of a certain minimum abundance. COSY cross peaks were most diverse for sample FMAX and conformed to >1,500 molecules present. Classical methyl groups terminating aliphatic chains represented only ~ 15 % of total methyl in all marine DOM investigated; 2 % of methyl was bound to olefinic carbon. Methyl ethers were abundant in surface marine DOM, and the chemical diversity of carbohydrates was larger than that of freshwater and soil DOM. TOCSY and HSQC cross peaks enabled unprecedented depiction of sp2-hybridized carbon chemical environments in marine SPE-DOM with discrimination of isolated and conjugated olefins as well as ?,?-unsaturated double bonds. Olefinic protons were more abundant than aromatic protons; relative HSQC cross peak integrals indicated more abundant olefinic carbon than aromatic carbon in all marine DOM as well. Furan, pyrrol and thiophene derivatives were marginal. Benzene derivatives and phenols as well as six-membered nitrogen heterocycles were prominent. Various key polycyclic aromatic hydrocarbon substructures suggested the presence of thermogenic organic matter (TMOC) in marine DOM at all water depths. Eventually, olefinic unsaturation in marine DOM will be more directly traceable to ultimate biogenic precursors than aromatic unsaturation. The conformity of key NMR signatures suggests the presence of a numerous set of identical molecules throughout the entire ocean column even if the investigated water masses belonged to different oceanic regimes and currents. High field (12 T) negative electrospray ionization FTICR mass spectra showed abundant CHO, CHNO, CHOS and CHNOS molecular series with slightly increasing numbers of mass peaks and average mass from surface to bottom SPE-DOM. The proportion of CHO and CHNO molecular series increased from surface to depth whereas CHOS and especially CHNOS molecular series markedly declined. The exhaustive characterization of complex unknowns in marine DOM will enable a meaningful assessment of individual marine biogeosignatures which carry the holistic memory of the oceanic water masses.

High field NMR spectroscopy and FTICR mass spectrometry: powerful discovery tools for the molecular level characterization of marine dissolved organic matter from the South Atlantic Ocean

NASA Astrophysics Data System (ADS)

Hertkorn, N.; Harir, M.; Koch, B. P.; Michalke, B.; Grill, P.; Schmitt-Kopplin, P.

2012-01-01

Non target high resolution organic structural spectroscopy of marine dissolved organic matter (DOM) isolated on 27 November 2008 by means of solid phase extraction (SPE) from four different depths in the South Atlantic Ocean off the Angola coast (3.1° E; -17.7° S; Angola basin) provided molecular level information of complex unknowns with unprecedented coverage and resolution. The sampling was intended to represent major characteristic oceanic regimes of general significance: 5 m (FISH; near surface photic zone), 48 m (FMAX; fluorescence maximum), 200 m (upper mesopelagic zone) and 5446 m (30 m above ground). 800 MHz proton (1H) nuclear magnetic resonance (NMR) 1H NMR, spectra were least affected by fast and differential transverse NMR relaxation and produced at first similar looking, rather smooth bulk NMR envelopes reflecting intrinsic averaging from massive signal overlap. Visibly resolved NMR signatures were most abundant in surface DOM but contributed at most a few percent to the total 1H NMR integral and were mainly limited to unsaturated and singly oxygenated carbon chemical environments. The relative abundance and variance of resolved signatures between samples was maximal in the aromatic region; in particular, the aromatic resolved NMR signature of the deep ocean sample at 5446 m was considerably different from that of all other samples. When scaled to equal total NMR integral, 1H NMR spectra of the four marine DOM samples revealed considerable variance in abundance for all major chemical environments across the entire range of chemical shift. Abundance of singly oxygenated CH units and acetate derivatives declined from surface to depth whereas aliphatics and carboxyl-rich alicyclic molecules (CRAM) derived molecules increased in abundance. Surface DOM contained a remarkably lesser abundance of methyl esters than all other marine DOM, likely a consequence of photodegradation from direct exposure to sunlight. All DOM showed similar overall 13C NMR resonance envelopes typical of an intricate mixture of natural organic matter with noticeable peaks of anomerics and C-aromatics carbon whereas oxygenated aromatics and ketones were of too low abundance to result in noticeable humps at the S/N ratio provided. Integration according to major substructure regimes revealed continual increase of carboxylic acids and ketones from surface to deep marine DOM, reflecting a progressive oxygenation of marine DOM, with concomitant decline of carbohydrate-related substructures. Isolation of marine DOM by means of SPE likely discriminated against carbohydrates but produced materials with beneficial NMR relaxation properties: a substantial fraction of dissolved organic molecules present allowed the acquisition of two-dimensional NMR spectra with exceptional resolution. JRES, COSY and HMBC NMR spectra were capable to depict resolved molecular signatures of compounds exceeding a certain minimum abundance. Here, JRES spectra suffered from limited resolution whereas HMBC spectra were constrained because of limited S/N ratio. Hence, COSY NMR spectra appeared best suited to depict organic complexity in marine DOM. The intensity and number of COSY cross peaks was found maximal for sample FMAX and conformed to about 1500 molecules recognizable in variable abundance. Surface DOM (FISH) produced a slightly (~25%) lesser number of cross peaks with remarkable positional accordance to FMAX (~80% conforming COSY cross peaks were found in FISH and FMAX). With increasing water depth, progressive attenuation of COSY cross peaks was caused by fast transverse NMR relaxation of yet unknown origin. However, most of the faint COSY cross peak positions of deep water DOM conformed to those observed in the surface DOM, suggesting the presence of a numerous set of identical molecules throughout the entire ocean column even if the investigated water masses belonged to different oceanic regimes and currents. Aliphatic chemical environments of methylene (CH2) and methyl (CH3) in marine DOM were nicely discriminated in DEPT HSQC NMR spectra. Classical methyl groups terminating aliphatic chains represented only ~15% of total methyl in all marine DOM investigated. Chemical shift anisotropy from carbonyl derivatives (i.e. most likely carboxylic acids) displaced aliphatic methyl 1H NMR resonances up to δH ~1.6 ppm, indicative of alicyclic geometry which furnishes more numerous short range connectivities for any given atom pairs. A noticeable fraction of methyl (~2%) was bound to olefinic carbon. The comparatively large abundance of methyl ethers in surface marine DOM contrasted with DOM of freshwater and soil origin. The chemical diversity of carbohydrates as indicated by H2CO-groups (δC ~ 62 ± 2 ppm) and anomerics (δC ~ 102 ± 7 ppm) exceeded that of freshwater and soil DOM considerably. HSQC NMR spectra were best suited to identify chemical environments of methin carbon (CH) and enabled discrimination of olefinic and aromatic cross peaks (δC > 110 ppm) and those of doubly oxygenated carbon (δC < 110 ppm). The abundance of olefinic protons exceeded that of aromatic protons; comparison of relative HSQC cross peak integrals indicated larger abundance of olefinic carbon than aromatic carbon in all marine DOM as well. A considerable fraction of olefins seemed isolated and likely sterically constrained as judged from small nJHH couplings associated with those olefins. High S/N ratio and fair resolution of TOCSY and HSQC cross peaks enabled unprecedented depiction of sp2-hybridized carbon chemical environments in marine DOM with discrimination of isolated and conjugated olefins as well as α, β-unsaturated double bonds. However, contributions from five-membered heterocycles (furan, pyrrol and thiophene derivatives) even if very unlikely from given elemental C/N and C/S ratios and upfield proton NMR chemical shift (δH < 6.5 ppm) could not yet been ruled out entirely. In addition to classical aromatic DOM, like benzene derivatives and phenols, six-membered nitrogen heterocycles were found prominent contributors to the downfield region of proton chemical shift (δH > 8 ppm). Specifically, a rather confined HSQC cross peak at δH/δC = 8.2/164 ppm indicated a limited set of nitrogen heterocycles with several nitrogen atoms in analogy to RNA derivatives present in all four marine DOM. Appreciable amounts of extended HSQC and TOCSY cross peaks derived from various key polycyclic aromatic hydrocarbon substructures suggested the presence of previously proposed but NMR invisible thermogenic organic matter (TMOC) in marine DOM at all water depths. Eventually, olefinic unsaturation in marine DOM will be more directly traceable to ultimate biogenic precursors than aromatic unsaturation of which a substantial fraction originates from an aged material which from the beginning was subjected to complex and less specific biogeochemical reactions like thermal decomposition. The variance in molecular mass as indicated from Fourier transform ion cyclotron resonance (FTICR) mass spectra was limited and could not satisfactorily explain the observed disparity in NMR transverse relaxation of the four marine DOM samples. Likewise, the presence of metal ions in isolated marine DOM remained near constant or declined from surface to depth for important paramagnetic ions like Mn, Cr, Fe, Co, Ni and Cu. Iron in particular, a strong complexing paramagnetic ion, was found most abundant by a considerable margin in surface (FISH) marine DOM for which well resolved COSY cross peaks were observed. Hence, facile relationships between metal content of isolated DOM (which does not reflect authentic marine DOM metal content) and transverse NMR relaxation were not observed. High field (12 T) negative electrospray ionization FTICR mass spectra showed at first view rather conforming mass spectra for all four DOM samples with abundant CHO, CHNO, CHOS and CHNOS molecular series with slightly increasing numbers of mass peaks from surface to bottom DOM and similar fractions (~50%) of assigned molecular compositions throughout all DOM samples. The average mass increased from surface to bottom DOM by about 10 Dalton. The limited variance of FTICR mass spectra probably resulted from a rather inherent conformity of marine DOM at the mandatory level of intrinsic averaging provided by FTICR mass spectrometry, when many isomers unavoidably project on single nominal mass peaks. In addition, averaging from ion suppression added to the accordance observed. The proportion of CHO and CHNO molecular series increased from surface to depth whereas CHOS and especially CHNOS molecular series markedly declined. The abundance of certain aromatic CHOS compounds declined with water depth. For future studies, COSY NMR spectra appear best suited to assess organic molecular complexity of marine DOM and to define individual DOM molecules of yet unknown structure and function. Non-target organic structural spectroscopy at the level demonstrated here covered nearly all carbon present in marine DOM. The exhaustive characterization of complex unknowns in marine DOM will reveal a meaningful assessment of individual marine biogeosignatures which carry the holistic memory of the oceanic water masses (Koch et al., 2011).

From an active continental plate margin to continental collision: New constraints from the petrological, structural and geochronological record of the (ultra) high-P metamorphic Rhodope domain (N-Greece)

NASA Astrophysics Data System (ADS)

Mposkos, E.; Krohe, A.; Wawrzenitz, N.; Romer, R. L.

2012-04-01

The Rhodope domain occupies a key area along the suture between the European and the Apulian/Adriatic plate (Schmid et al., 2008), which collided in the early Tertiary (closure of the Vardar/Axios ocean, cf. Mposkos & Krohe, 2006). An integrated study of the geochronological, tectonic and petrological data of the Rhodope domain provides the unique opportunity resolving a 160 my lasting metamorphic evolution (Jurassic to Miocene) of an active plate margin to a high degree. The Greek Rhodope consists of several composite metamorphic complexes bounded by the Nestos thrust and several normal detachment systems. The PT- and structural records of the complexes constrain metamorphic, magmatic and tectonic processes, associated with subduction along a convergent plate margin including UHP metamorphism, MP to HP metamorphism associated with continental collision, and core complex formation linked to Aegean back arc extension. We focus on the Sidironero Complex that shows a polymetamorphic history. This is documented by SHRIMP and LA-ICP-MS U-Pb zircon ages of ca. 150 Ma from garnet-kyanite gneisses that are interpreted to record the HP/UHP metamorphism (Liati, 2005; Krenn et al., 2010). SHRIMP zircon ages of ca. 51 Ma from an amphibolitized eclogite is interpreted by Liati (2005) to record a second Eocene HP metamorphic event. We present new data from an integrated petrological, geochronological and tectonic study. Granulite facies and upper amphibolite facies metamorphic conditions are recorded by the mineral assemblage Grt-Ky-Bt-Pl-Kfs-Qtz-Rt and Grt-Ky-Bt-Ms-Pl-Qtz-Rt, respectively, in deformed migmatitic metapelites. Deformation occurred under granulite facies conditions. Monazites from the matrix, that formed during the granulite facies deformation, lack core/rim structures and are only locally patchy zoned. Monazite chemical compositions are related to varying reaction partners. Single grains and fractions of few grains yield ID-TIMS U-Pb ages that plot along the concordia between 64 to 60 Ma. One date of 55 Ma might represent Pb-loss during later fluid-induced dissolution-reprecipitation. We discuss the following questions: What is the history of the high-P metamorphic rocks in the Sidironero Complex? Were high-P rocks that have been already exhumed again dragged into the subduction channel? Which rocks from the upper plate are affected by high-P metamorphism evincing that subduction erosion is an important mechanism? We reconsider the significance of the P-T-t evolution in the light of the tectonic processes that took place along the depth extension of a convergent plate interface and during subsequent continental collision along the European/Apulian Suture zone. Krenn et al., 2010. Tectonics 29, TC4001. Liati, A., 2005. Contribution to Mineralogy and Petrology 150, 608-630. Mposkos, E. & Krohe, A. 2006. Canadian Journal of Earth Sciences 43, 1755-1776. Schmid S.M., et al. 2008. Swiss Journal of Geoscience 101, 139-183.

Partitioning of dissolved organic matter-bound mercury between a hydrophobic surface and polysulfide-rubber polymer.

PubMed

Kim, Eun-Ah; Luthy, Richard G

2011-11-01

This study investigated the role of dissolved organic matter on mercury partitioning between a hydrophobic surface (polyethylene, PE) and a reduced sulfur-rich surface (polysulfide rubber, PSR). Comparative sorption studies employed polyethylene and polyethylene coated with PSR for reactions with DOM-bound mercuric ions. These studies revealed that PSR enhanced the Hg-DOM removal from water when DOM was Suwannee River natural organic matter (NOM), fulvic acid (FA), or humic acid (HA), while the same amount of 1,3-propanedithiol-bound mercuric ion was removed by both PE and PSR-PE. The differences for Hg-DOM removal efficiencies between PE and PSR-PE varied depending on which DOM was bound to mercuric ion as suggested by the PE/water and PSR-PE/water partition coefficients for mercury. The surface concentrations of mercury on PE and PSR-PE with the same DOM measured by x-ray photoelectron spectroscopy were similar, which indicated the comparable amounts of immobilized mercury on PE and PSR-PE being exposed to the aqueous phase. With these observations, two major pathways for the immobilization reactions between PSR-PE and Hg-DOM were examined: 1) adsorption of Hg-DOM on PE by hydrophobic interactions between DOM and PE, and 2) addition reaction of Hg-DOM onto PSR by a complexation reaction between Hg and PSR. The percent contribution of each pathway was derived from a mass balance and the ratios among aqueous mercury, PE-bound Hg-DOM, and PSR-bound Hg-DOM concentrations. The results indicate strong binding of mercuric ion with both dissolved organic matter and PSR polymer. The FT-IR examination of Hg-preloaded-PSR-PEs after the reaction with DOM corroborated a strong interaction between mercuric ion and 1,3-propanedithiol compared to Hg-HA, Hg-FA, or Hg-NOM interactions. Copyright © 2011 Elsevier Ltd. All rights reserved.

Partitioning of dissolved organic matter-bound mercury between a hydrophobic surface and polysulfide-rubber polymer

PubMed Central

Kim, Eun-Ah

2011-01-01

This study investigated the role of dissolved organic matter on mercury partitioning between a hydrophobic surface (polyethylene, PE) and a reduced sulfur-rich surface (polysulfide rubber, PSR). Comparative sorption studies employed polyethylene and polyethylene coated with PSR for reactions with DOM-bound mercuric ions. These studies revealed that PSR enhanced the Hg-DOM removal from water when DOM was Suwannee River natural organic matter (NOM), fulvic acid (FA), or humic acid (HA), while the same amount of 1,3-propanedithiol-bound mercuric ion was removed by both PE and PSR-PE. The differences for Hg-DOM removal efficiencies between PE and PSR-PE varied depending on which DOM was bound to mercuric ion as suggested by the PE/water and PSR-PE/water partition coefficients for mercury. The surface concentrations of mercury on PE and PSR-PE with the same DOM measured by x-ray – photoelectron spectroscopy were similar, which indicated the comparable amounts of immobilized mercury on PE and PSR-PE being exposed to the aqueous phase. With these observations, two major pathways for the immobilization reactions between PSR-PE and Hg- DOM were examined: 1) adsorption of Hg-DOM on PE by hydrophobic interactions between DOM and PE, and 2) addition reaction of Hg-DOM onto PSR by a complexation reaction between Hg and PSR. The percent contribution of each pathway was derived from a mass balance and the ratios among aqueous mercury, PE-bound Hg-DOM, and PSR-bound Hg-DOM concentrations. The results indicate strong binding of mercuric ion with both dissolved organic matter and PSR polymer. The FT-IR examination of Hg-preloaded-PSR-PEs after the reaction with DOM corroborated a strong interaction between mercuric ion and 1,3-propanedithiol compared to Hg-HA, Hg-FA, or Hg-NOM interactions. PMID:21872900

Hydrothermal alteration and timing of gold mineralisation in the Rumbia Complex, Southeast Arm of Sulawesi, Indonesia

NASA Astrophysics Data System (ADS)

Mawaleda, Musri; Suparka, Emmy; Idham Abdullah, Chalid; Indro Basuki, Nurcahyo; Forster, Marnie; Jamal; Kaharuddin

2017-06-01

The Rumbia Mountains, which in this study named Rumbia schist Complex is an east-west oriented, composed by a high-pressure/low-temperature, and a medium-pressure/low-temperature metamorphic rocks. Identified as mica schist, glauchopane schist, and green schist. Rumbia complex known as the location of gold deposits prospects discovered by local communities since 2007. The results of research showed that the metamorphic rocks are as hosts. There are two phase of gold mineralization that occurs in this area, namely: 1) Associated with tectonic deformation and metamorphic rocks exhumation, and 2) gold-related hydrothermal deposits. Radiometric age dating used 40Ar/39Ar geochronology, indicate that the first of gold mineralisation in the Rumbia Complex occurred ∼23 million years ago, and the second gold mineralisation were subsequently overprinting at 7 million years ago.

PT conditions of metamorphism in the Wami River granulite complex, central coastal Tanzania: implications for Pan-African geotectonics in the Mozambique Belt of eastern Africa

NASA Astrophysics Data System (ADS)

Maboko, M. A. H.

1997-02-01

Solid-solution equilibria for gamet-clinopyroxene pairs in the early Pan-African Wami River granulite complex of central coastal Tanzania indicate metamorphic recrystallization at a temperature of about 700°C and a pressure of 8-9 kb, corresponding to metamorphism at a depth of 30-40 km. This suggests that granulite formation was preceded by an anomalous regional crustal thickening, similar to the crustal doubling that accompanies Phanerozoic continent-continent collisions of the Himalaya type. The analogy prompts the interpretation of the Wami River granulite complex, and possibly the rest of the granulite complexes in the Mozambique Belt, as slices of the underthrusted plate, which were accreted to the present day African plate following a continent-continent collision during early Pan-African time.

Mercury reduction and complexation by natural organic matter in anoxic environments

PubMed Central

Gu, Baohua; Bian, Yongrong; Miller, Carrie L.; Dong, Wenming; Jiang, Xin; Liang, Liyuan

2011-01-01

Mercuric Hg(II) species form complexes with natural dissolved organic matter (DOM) such as humic acid (HA), and this binding is known to affect the chemical and biological transformation and cycling of mercury in aquatic environments. Dissolved elemental mercury, Hg(0), is also widely observed in sediments and water. However, reactions between Hg(0) and DOM have rarely been studied in anoxic environments. Here, under anoxic dark conditions we show strong interactions between reduced HA and Hg(0) through thiolate ligand-induced oxidative complexation with an estimated binding capacity of ~3.5 μmol Hg/g HA and a partitioning coefficient >106 mL/g. We further demonstrate that Hg(II) can be effectively reduced to Hg(0) in the presence of as little as 0.2 mg/L reduced HA, whereas production of Hg(0) is inhibited by complexation as HA concentration increases. This dual role played by DOM in the reduction and complexation of mercury is likely widespread in anoxic sediments and water and can be expected to significantly influence the mercury species transformations and biological uptake that leads to the formation of toxic methylmercury. PMID:21220311

Molecular Characterization and Reactivity of Dissolved Organic Matter by High Resolution Nanospray Ionization Fourier Transform-Ion Cyclotron Resonance Mass Spectrometry (FTICR-MS)

NASA Astrophysics Data System (ADS)

Sleighter, R. L.; Hatcher, S. A.; Hatcher, P. G.

2006-12-01

The ultrahigh resolving power of FTICR-MS allows for the intense characterization of dissolved organic matter (DOM). DOM is the largest reactive component of the global carbon cycle, and an improved understanding of its composition is necessary to determine the transport and eventual fate of pollutants. The seasonal and spatial variations in DOM composition are investigated by taking surface water samples from five different sampling sites, four times a year. Water sampling begins at the Dismal Swamp in North Carolina, continues north up the Elizabeth River to the Chesapeake Bay, and concludes approximately ten miles off the coast in the Atlantic Ocean. DOM was extracted from the water samples using C18 extraction disks and were prepared in 50:50 methanol:water. Ammonium hydroxide was added prior to nanospray in order to solubilize the DOM as well as to increase the ionization efficiency. The samples were continuously infused into the Apollo II ion source with an Advion TriVersa NanoMate system of a Bruker 12 Tesla Apex QE FTICR-MS with resolving powers exceeding 400,000. All samples were analyzed in negative ion mode and were externally and internally calibrated prior to data analysis. Our DOM mass spectra consist of a multitude of peaks spanning the range of 200-850 m/z. Complexity is apparent from the detection of up to 20 peaks per nominal mass at nearly every mass throughout that range. A molecular formula calculator generated molecular formula matches from which van Krevelen plots were constructed for characterization purposes. A wide range of molecules were observed each containing oxygen, sulfur and nitrogen functional groups. We utilize the van Krevelen diagram to assist in clustering the molecules according to their functional group compositions. To test the hypothesis that formation of adducts to DOM serve to protect peptides from bacterial degradation, microcosm experiments were performed with a small isotopically enriched peptide, GGGR. This peptide was predicted to covalently bond to DOM via a Michael addition reaction or Schiff base formation. Following the incubation of GGGR with DOM, adduct formation was examined by FTICR-MS. Covalent binding of GGGR to DOM is a process that may reduce the bioavailability and degradation of proteins in the environment and could potentially lead to their preservation on longer time scales. FTICR-MS is clearly a powerful technique used to examine the complex composition of DOM and allow for advancements in the areas of aquatic and analytical chemistry.

The lateral boundary of a metamorphic core complex: the Moutsounas shear zone on Naxos, Cyclades, Greece

NASA Astrophysics Data System (ADS)

Cao, S.; Neubauer, F.

2012-04-01

One of the apparently best investigated metamorphic core complexes all over world is that of Naxos in the Aegean Sea and numerous high-quality data on structures and microfabrics have been published. Among these structures is the Naxos-Paros ductile low-angle fault (Gautier et al., 1993), which is located along the northern margin of Naxos and which is part of the North Cycladic Detachment System (Jolivet et al., 2010). There, structural evidence indicates that the hanging wall of the core complex experienced large-scale top-to-the-north (ca. 010°) transport along a low-angle detachment fault. Interestingly no attention has been paid on the well exposed boundary fault on the eastern margin of the Naxos Island, which is even not mentioned in the lierarure. We denote this fault as Moutsounas shear zone, which represents the lateral boundary of the Naxos metamorphic core complex. The Naxos metamorphic core complex is a N-trending elongated dome, which exposes on its eastern side moderately E-dipping micaschists and marbles, which are largely well annealed due to late heating. These annealed rocks grade towards the Moutsounas Peninsula in retrogressed sheared rocks, mostly phyllonitic micaschists and phyllites with an E-dipping foliation and a ca. NNE-trending subhorizontal stretching lineation. Shear bands, asymmetric fringes around rigid clasts and oblique mineralized extension veins consistently indicate top-to-the-NNE shear. The shear zone is structurally overlain by hydrothermally altered Miocene conglomerates, which contain no pebbles from the Naxos metamorphic core complex but exclusively from the ophiolitic hangingwall unit. Miocene rocks are exposed both on the northern and southern edge of the Moutsounas Peninsula. Their bedding is variable but dips generally towards NW, oblique to the detachment fault, which dips with a medium-angle towards east indicating therefore a rollover structure. The Miocene succession is overlain by subhorizontal conglomerates of Pliocene age, which form the main portion of the Moutsounas Peninsula and which contain numerous clasts, mainly marble, of the metamorphic core complex. These sedimentary data indicate that exhumation of the Naxos metamorphic core complex postdate deposition of Miocene successions and predate Pliocene rocks. We interpret the Moutsounas shear zone as a lateral boundary of the Naxos migmatite dome and relate their main activity with top NNE-shear with the main stage of updoming during migmatite formation and granite uplift between ca. 15 and 11 Ma.

High-pressure granulites in the Fuping Complex of the central North China Craton: Metamorphic P-T-t evolution and tectonic implications

NASA Astrophysics Data System (ADS)

Qian, Jiahui; Yin, Changqing; Zhang, Jian; Ma, Li; Wang, Luojuan

2018-04-01

Mafic granulites in the Fuping Complex occur as lenses or boudins within high-grade TTG (Trondhjemite-Tonalite-Granodiorite) gneisses. Petrographic observations reveal four generations of mineral assemblage in the granulites: an inclusion assemblage of hornblende + plagioclase + ilmenite + quartz within garnet core; an inferred peak assemblage composed of garnet ± hornblende + plagioclase + clinopyroxene + rutile/ilmenite + quartz; a decompression assemblage characterized by symplectites of clinopyroxene ± orthopyroxene + plagioclase, coronae of plagioclase ± clinopyroxene ± hornblende around embayed garnet porphyroblasts or a two-pyroxene association; and a late amphibolite-facies retrogressive assemblage. Two representative samples were used for pseudosection modeling in NCFMASHTO model system to determine their metamorphic evolution. The results show that these granulites experienced a high-pressure stage of metamorphism with peak P-T conditions of 12-13 kbar and 760-800 °C (Pmax) and a post-peak history under P-T conditions of ∼9.0 kbar and 805-835 °C (Tmax), indicating a nearly isothermal decompression process (ITD) with a slight heating. Metamorphic evolution from the Pmax to the Tmax is predicted to be dominated by garnet breakdown through continuous metamorphic reactions of garnet + quartz ± diopside = hornblende + plagioclase + liquid and garnet + quartz + hornblende = plagioclase + diopside + liquid + orthopyroxene. Further metamorphic evolution after the Tmax is dominated by cooling, suggesting that high-pressure (HP) granulites may also exist in the Fuping Complex. Metamorphic zircons in the Fuping HP mafic granulites have left inclined REE patterns, Ti contents of 1.68-6.88 ppm and crystallization temperatures of 602-712 °C. SIMS zircon U-Pb dating on these zircons yields 207Pb/206Pb ages of 1891 ± 14 Ma and 1849 ± 6 Ma, interpreted to represent the cooling stage of metamorphism. The P-T-t evolution of the Fuping HP mafic granulites records well the protracted Paleoproterozoic orogenic event occurred in the central North China Craton.

Age, temperature and pressure of metamorphism in the Tasriwine Ophiolite Complex, Sirwa, Morocco

NASA Astrophysics Data System (ADS)

Samson, S. D.; Inglis, J.; Hefferan, K. P.; Admou, H.; Saquaque, A.

2013-12-01

Sm-Nd garnet-whole rock geochronology and phase equilbria modeling have been used to determine the age and conditions of regional metamorphism within the Tasriwine ophiolite complex,Sirwa, Morocco. Pressure and temperature estimates obtained using a NaCaKFMASHT phase diagram (pseudosection) and garnet core and rim compositions predict that garnet growth began at ~0.72GPa and ~615°C and ended at ~0.8GPa and ~640°C. A bulk garnet Sm-Nd age of 645.6 × 1.6 Ma, calculated from a four point isochron that combines whole rock, garnet full dissolution and two successively more aggressive partial dissolutions, provides a precise date for garnet formation and regional metamorphism. The age is nearly 20 million years younger than a previous age estimate of regional metamorphism of 663 × 14 Ma based upon a SHRIMP U-Pb date from rims on zircon from the Irri migmatite. The new data provide further constraints on the age and nature of regional metamorphism in the Anti-Atlas mountains and emphasizes that garnet growth during regional metamorphism may not necessarily coincide with magmatism/anatexis which predominate the signature witnessed by previous U-Pb studies. The ability to couple PT estimates for garnet formation with high precision Sm- Nd geochronology highlights the utility of garnet studies for uncovering the detailed metamorphic history of the Anti-Atlas mountain belt.

Induced structural changes of humic acid by exposure of polystyrene microplastics: A spectroscopic insight.

PubMed

Chen, Wei; Ouyang, Zhen-Yu; Qian, Chen; Yu, Han-Qing

2018-02-01

The occurrence of microplastics (MPs) as emerging contaminants in the environment may cause changes in water or sediment characteristics, and further affect their biogeochemical cycles. Thus, insights into the interactions between dissolved organic matter (DOM) and MPs are essential for the assessment of environmental impacts of MPs in ecosystems. Integrating spectroscopic methods with chemometric analyses, this work explored the chemical and microstructural changes of DOM-MP complex to reveal the mechanism of DOM-MP interaction at a molecular level. MPs were found to interact with the aromatic structure of DOM via π-π conjugation, then be entrapped in the DOM polymers by the carboxyl groups and C=O bonds, constituting a highly conjugated co-polymer with increased electron density. This induced the fluorescence intensity increase in DOM. The interaction affinity of DOM-MP was highly dependent on the MP size and solution pH. This work offers a new insight into the impact of MP discharge on environment and may provide an analytical framework for evaluating MP hetero-aggregation and the roles of MPs in the transportation of other contaminants. Furthermore, the integrated methods used in this work exhibit potential applications in exploring the fragmentation processes of MPs and formation of secondary MPs under natural conditions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Dissolved organic matter enhances microbial mercury methylation under sulfidic conditions

USGS Publications Warehouse

Graham, Andrew M.; Aiken, George R.; Gilmour, Cynthia

2012-01-01

Dissolved organic matter (DOM) is generally thought to lower metal bioavailability in aquatic systems due to the formation of metal–DOM complexes that reduce free metal ion concentrations. However, this model may not be pertinent for metal nanoparticles, which are now understood to be ubiquitous, sometimes dominant, metal species in the environment. The influence of DOM on Hg bioavailability to microorganisms was examined under conditions (0.5–5.0 nM Hg and 2–10 μM sulfide) that favor the formation of β-HgS(s) (metacinnabar) nanoparticles. We used the methylation of stable-isotope enriched 201HgCl2 by Desulfovibrio desulfuricans ND132 in short-term washed cell assays as a sensitive, environmentally significant proxy for Hg uptake. Suwannee River humic acid (SRHA) and Williams Lake hydrophobic acid (WLHPoA) substantially enhanced (2- to 38-fold) the bioavailability of Hg to ND132 over a wide range of Hg/DOM ratios (9.4 pmol/mg DOM to 9.4 nmol/mg DOM), including environmentally relevant ratios. Methylmercury (MeHg) production by ND132 increased linearly with either SRHA or WLHPoA concentration, but SRHA, a terrestrially derived DOM, was far more effective at enhancing Hg-methylation than WLHPoA, an aquatic DOM dominated by autochthonous sources. No DOM-dependent enhancement in Hg methylation was observed in Hg–DOM–sulfide solutions amended with sufficient l-cysteine to prevent β-HgS(s) formation. We hypothesize that small HgS particles, stabilized against aggregation by DOM, are bioavailable to Hg-methylating bacteria. Our laboratory experiments provide a mechanism for the positive correlations between DOC and MeHg production observed in many aquatic sediments and wetland soils.

The effect of advanced secondary municipal wastewater treatment on the molecular composition of dissolved organic matter.

PubMed

Maizel, Andrew C; Remucal, Christina K

2017-10-01

There is a growing interest in water reuse and in recovery of nutrients from wastewater. Because many advanced treatment processes are designed to remove organic matter, a better understanding of the composition of dissolved organic matter (DOM) in wastewater is needed. To that end, we assessed DOM in the Nine Springs Wastewater Treatment Plant in Madison, Wisconsin by UV-visible spectroscopy and Fourier transform-ion cyclotron resonance mass spectrometry. Samples were collected from the influent and effluent of two different secondary treatment processes and their respective secondary clarifiers, the UV disinfection unit, and an Ostara treatment system, which produces struvite via chemical precipitation. The optical properties reveal that DOM throughout the plant is relatively aliphatic and is low in molecular weight compared to DOM in freshwater systems. Furthermore, the DOM is rich in heteroatoms (e.g., N, S, P, and Cl) and its molecular formulas are present in the lipid-, protein-, carbohydrate-, and lignin-like regions of van Krevelen diagrams. Secondary treatment produces DOM that is more aromatic and more complex, as shown by the loss of highly saturated formulas and the increase in the number of CHO, CHON, and CHOP formulas. The two secondary treatment processes produce DOM with distinct molecular compositions, while the secondary clarifiers and UV disinfection unit result in minimal changes in DOM composition. The Ostara process decreases the molecular weight of DOM, but does not otherwise alter its composition. The optical properties agree with trends in the molecular composition of DOM within the main treatment train of the Nine Springs plant. Copyright © 2017 Elsevier Ltd. All rights reserved.

Fiskenaesset Anorthosite Complex: Stable isotope evidence for shallow emplacement into Archean ocean crust

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peck, W.H.; Valley, J.W.

1996-06-01

Oxygen and hydrogen isotope ratios indicate that unusual rocks at the upper contact of the Archean Fiskenaesset Anorthosite Complex at Fiskenaesset Harbor (southwest Greenland) are the products of hydrothermal alteration by seawater at the time of anorthosite intrusion. Subsequent granulite-facies metamorphism of these Ca-poor and Al- and Mg-rich rocks produced sapphirine- and kornerupine-bearing assemblages. Because large amounts of surface waters cannot penetrate to depths of 30 km during granulite-facies metamorphism, the isotopic signature of the contact rocks must have been obtained prior to regional metamorphism. The stable isotope and geochemical characteristics of the contact rocks support a model of shallowmore » emplacement into Archean ocean crust for the Fiskenaesset Anorthosite Complex. 45 refs., 3 figs., 2 tabs.« less

Deciphering ocean carbon in a changing world

PubMed Central

Moran, Mary Ann; Stubbins, Aron; Fatland, Rob; Aluwihare, Lihini I.; Buchan, Alison; Crump, Byron C.; Dorrestein, Pieter C.; Dyhrman, Sonya T.; Hess, Nancy J.; Howe, Bill; Longnecker, Krista; Medeiros, Patricia M.; Obernosterer, Ingrid; Repeta, Daniel J.; Waldbauer, Jacob R.

2016-01-01

Dissolved organic matter (DOM) in the oceans is one of the largest pools of reduced carbon on Earth, comparable in size to the atmospheric CO2 reservoir. A vast number of compounds are present in DOM, and they play important roles in all major element cycles, contribute to the storage of atmospheric CO2 in the ocean, support marine ecosystems, and facilitate interactions between organisms. At the heart of the DOM cycle lie molecular-level relationships between the individual compounds in DOM and the members of the ocean microbiome that produce and consume them. In the past, these connections have eluded clear definition because of the sheer numerical complexity of both DOM molecules and microorganisms. Emerging tools in analytical chemistry, microbiology, and informatics are breaking down the barriers to a fuller appreciation of these connections. Here we highlight questions being addressed using recent methodological and technological developments in those fields and consider how these advances are transforming our understanding of some of the most important reactions of the marine carbon cycle. PMID:26951682

Deciphering ocean carbon in a changing world.

PubMed

Moran, Mary Ann; Kujawinski, Elizabeth B; Stubbins, Aron; Fatland, Rob; Aluwihare, Lihini I; Buchan, Alison; Crump, Byron C; Dorrestein, Pieter C; Dyhrman, Sonya T; Hess, Nancy J; Howe, Bill; Longnecker, Krista; Medeiros, Patricia M; Niggemann, Jutta; Obernosterer, Ingrid; Repeta, Daniel J; Waldbauer, Jacob R

2016-03-22

Dissolved organic matter (DOM) in the oceans is one of the largest pools of reduced carbon on Earth, comparable in size to the atmospheric CO2 reservoir. A vast number of compounds are present in DOM, and they play important roles in all major element cycles, contribute to the storage of atmospheric CO2 in the ocean, support marine ecosystems, and facilitate interactions between organisms. At the heart of the DOM cycle lie molecular-level relationships between the individual compounds in DOM and the members of the ocean microbiome that produce and consume them. In the past, these connections have eluded clear definition because of the sheer numerical complexity of both DOM molecules and microorganisms. Emerging tools in analytical chemistry, microbiology, and informatics are breaking down the barriers to a fuller appreciation of these connections. Here we highlight questions being addressed using recent methodological and technological developments in those fields and consider how these advances are transforming our understanding of some of the most important reactions of the marine carbon cycle.

Role of Free Radicals/Reactive Oxygen Species in MeHg Photodegradation: Importance of Utilizing Appropriate Scavengers.

PubMed

Han, Xiaoxiao; Li, Yanbin; Li, Dan; Liu, Chang

2017-04-04

A variety of free radicals (FR)/reactive oxygen species (ROS) have been proposed to dominate methylmercury (MeHg) photodegradation, primarily based on the results of FR/ROS scavenger addition experiments. However, in addition to eliminating FR/ROS, the added scavengers may also affect the experimental results by altering some water chemical properties, resulting in a misleading assessment of the importance of FR/ROS. In this study, 20 common FR/ROS scavengers were evaluated in terms of their influence on light absorbance, pH, MeHg analysis, MeHg-dissolved organic matter (DOM) complexation, and the scavenger-induced degradation of MeHg. Only nine scavengers were identified to be appropriate for investigating MeHg photodegradation. By utilizing these appropriate scavengers, direct photodegradation of MeHg-DOM complexes was found to be the major pathway of MeHg photodegradation in Laoshan Reservoir water and Stone Old Beach seawater. In contrast, MeHg photodegradation in Ink River water primarily occurs through both ·OH and 3 DOM* mediated indirect pathways and direct photodegradation of MeHg-DOM complexes. The diverse pathways of MeHg photodegradation in the tested water may be due to differences in water chemical properties. A severe overestimation of the role of FR/ROS was observed when several improper but commonly used scavengers were adopted, highlighting the necessity of utilizing appropriate scavengers.

Eclogites and garnet clinopyroxenites in the Anrakhai complex, Central Asian Orogenic Belt, Southern Kazakhstan: P-T evolution, protoliths and some geodynamic implications

NASA Astrophysics Data System (ADS)

Pilitsyna, Anfisa V.; Tretyakov, Andrey A.; Degtyarev, Kirill E.; Cuthbert, Simon J.; Batanova, Valentina G.; Kovalchuk, Elena V.

2018-03-01

The Anrakhai Metamorphic Complex (AMC), located in the SE part of the Chu-Ili Mountains of Southern Kazakhstan in the western part of Central Asian Orogenic Belt, exhibits occurrences of HP metamorphic rocks in the form of eclogites and garnet clinopyroxenites with peak metamorphic conditions of 750-850° and 15-19 kbar estimated with both conventional geothermobarometric methods and phase diagram modeling. P-T estimates as well as intimate field relations evidently imply a common metamorphic history for eclogites and garnet clinopyroxenites of the AMC. These high-pressure, medium temperature eclogite facies P-T conditions are indicative of a collision or subduction tectonic setting. Major and trace element geochemistry suggests that they probably had a common magmatic origin as part of a suite of differentiated tholeiitic intrusions. Furthermore, distinctive mineral and chemical compositions of these eclogites and garnet clinopyroxenites correspond to the Fe-Ti type of ultramafic rocks suggesting that they may have been derivatives of intraplate tholeiitic melts, introduced into continental crust before HP metamorphism.

Chemical and oxygen isotope zonings in garnet from subducted continental crust record mineral replacement and metasomatism

NASA Astrophysics Data System (ADS)

Vho, Alice; Rubatto, Daniela; Regis, Daniele; Baumgartner, Lukas; Bouvier, Anne-Sophie

2017-04-01

Garnet is a key mineral in metamorphic petrology for constraining pressure, temperature and time paths. Garnet can preserve multiple growth stages due to its wide P-T stability field and the relatively slow diffusivity for major and trace elements at sub-solidus temperatures. Pressure-temperature-time-fluid paths of the host rock may be reconstructed by combining metamorphic petrology with microscale trace element and oxygen isotope measurements in garnet. Subduction zones represent relevant geological settings for geochemical investigation of element exchanges during aqueous fluid-rock interactions. The Sesia Zone consists of a complex continental sequence containing a variety of mono-metamorphic and poly-metamorphic lithologies such as metagranitoids, sediments and mafic boudins. The precursor Varisican-Permian amphibolite-facies basement (6-9 kbar 650-850°C; Lardeaux and Spalla, 1991; Robyr et al., 2013) experienced high pressure metamorphism (15-22 kbar 500-550°C; Regis, et al. 2014; Robyr et al., 2013) during Alpine subduction. In different lithologies of the Internal Complex (Eclogitic Micaschist Complex), including metabasites from the Ivozio Complex, Ti-rich metasediments from Val Malone and pre-Alpine Mn-quartzites associated to metagabbros from Cima Bonze, garnet is abundant and shows a variety of complex textures that cannot be reconciled with typical growth zoning, but indicate resorption and replacement processes and possible metasomatism. In-situ, microscale oxygen isotopes analysis of garnet zones was performed by ion microprobe with the SwissSIMS Cameca IMS 1280-HR at University of Lausanne and SHRIMP-SI at the Australian National University. Each sample has a distinct δ18O composition, and the δ18O values show different degrees of variation between domains. Homogeneously low values of < 5‰ are measured in the garnets from the Ivozio Complex metagabbro. Intragrain variations of up to 3.5‰ in the porphyroblasts from Val Malone metasediments, and variations up to 6.5‰ in Cima Bonze garnets suggest significant metasomatic replacement from external fluids. The combination of oxygen isotopes, trace element geochemistry and P-T modelling allows reconstructing the major stages of metasomatism, as well as identifying the nature of the fluid interacting with the rock at each metamorphic stage. REFERENCES Lardeaux, J. M., & Spalla, M. I. (1991). From granulites to eclogites in the Sesia zone (Italian Western Alps): A record of the opening and closure of the Piedmont ocean. Journal of Metamorphic Geology, 9, 35-59. Regis, D., Rubatto, D., Darling, J., Cenki-Tok, B., Zucali, M., & Engi, M. (2014). Multiple metamorphic stages within an eclogite-facies terrane (Sesia Zone, Western Alps) revealed by Th-U-Pb petrochronology. Journal of Petrology, 55(7), 1429-1456. Robyr, M., Darbellay, B., & Baumgartner, L. P. (2014). Matrix-dependent garnet growth in polymetamorphic rocks of the Sesia zone, Italian Alps. Journal of Metamorphic Geology, 32(1), 3-24.

Application of Bayesian belief net in modelling the origin and effects of terrigenous dissolved organic matter in a boreal aquatic ecosystem

NASA Astrophysics Data System (ADS)

Rahikainen, Mika; Hoikkala, Laura; Soinne, Helena

2013-04-01

Bayesian belief nets (BBN) are capable of developing holistic understanding of the origin, transportation, and effects of dissolved organic matter (DOM) in ecosystems. The role of riverine DOM, transporting carbon and macronutrients N and P into lakes and coastal areas, has been largely neglected in research about processes influencing aquatic ecosystem functions although dissolved organic matter provides a significant nutrient source for primary producers in aquatic environments. This neglect has also contributed to the environmental policies which are focused in the control of inorganic N and P load. It is of great social and economic interest to gain improved knowledge of whether the currently applied policy instruments act in synchrony in mitigating eutrophication caused by N and P versus DOM load. DOM is a complex mixture of compounds that are poorly characterized. DOM export is strongly regulated by land use (urban, forest, agricultural land, peat land), in addition to soil type and soil organic carbon concentration. Furthermore, the composition of DOM varies according to its origin. The fate and effects of DOM loads in the fresh water and coastal environments depend, for example, on their biodegradability. Degradation kinetics again depends on the interactions between composition of the DOM pool and the receiving environment. Impact studies of dissolved organic matter pose a complicated environmental impact assessment challenge for science. There exists strategic uncertainty in the science about the causal dependencies and about the quality of knowledge related to DOM. There is a clear need for systematization in the approach as uncertainty is typically high about many key processes. A cross-sectorial, integrative analysis will aid in focusing on the most relevant issues. A holistic and unambiguous analysis will provide support for policy-decisions and management by indicating which outcome is more probable than another. The task requires coupling complex models of different environmental compartments (soil chemistry, agricultural management practices, aquatic processes, costs and benefits for society) with explicit treatment of uncertainty. In order to achieve policy relevance, these models have to be integrated into resource management. We use a Bayesian belief net to describe the probabilistic dependencies among the driving forces, processes, and impacts relevant to dissolved organic matter in boreal waterways.

Characterisation of dissolved organic matter in stormwater using high-performance size exclusion chromatography.

PubMed

Huang, Huiping; Chow, Christopher W K; Jin, Bo

2016-04-01

Understanding the complexity of dissolved organic matter (DOM) in stormwater has drawn a lot of interest, since DOM from stormwater causes not only environmental impacts, but also worsens downstream aquatic quality associated with water supply and treatability. This study introduced and employed high-performance size exclusion chromatography (HPSEC) coupled with an ultraviolet-visible (UV-vis) diode array detector to assess changes in stormwater-associated DOM characteristics. Stormwater DOM was also analysed in relation to storm event characteristics, water quality and spectroscopic analysis. Statistical tools were used to determine the correlations within DOM and water quality measurements. Results showed that dissolved organic carbon (DOC) and UV absorbance at 254 nm (UV254) as conventional DOM parameters were found to be correlated well to the changes in stormwater quality during each of the three storm events studied. Both detector wavelengths (210 and 254 nm) and their ratio (A210/A254) were found to provide additional information on the physiochemical properties of stormwater-associated DOM. This study indicated that A210/A254 is an important parameter which could be used to estimate the DOM proportions of functional groups and conjugated carbon species. This study provided also an understanding of stormwater quality constituents through assessing variability and sensitivity for various parameters, and the additional information of rainfall characteristics on runoff quality data for a better understanding of parameter correlations and influences. Copyright © 2015. Published by Elsevier B.V.

Dissolved organic matter kinetically controls mercury bioavailability to bacteria.

PubMed

Chiasson-Gould, Sophie A; Blais, Jules M; Poulain, Alexandre J

2014-03-18

Predicting the bioavailability of inorganic mercury (Hg) to bacteria that produce the potent bioaccumulative neurotoxin monomethylmercury remains one of the greatest challenges in predicting the environmental fate and transport of Hg. Dissolved organic matter (DOM) affects mercury methylation due to its influence on cell physiology (as a potential nutrient) and its influence on Hg(II) speciation in solution (as a complexing agent), therefore controlling Hg bioavailability. We assessed the role of DOM on Hg(II) bioavailability to a gram-negative bacterium bioreporter under oxic pseudo- and nonequilibrium conditions, using defined media and field samples spanning a wide range of DOM levels. Our results showed that Hg(II) was considerably more bioavailable under nonequilibrium conditions than when DOM was absent or when Hg(II) and DOM had reached pseudoequilibrium (24 h) prior to cell exposure. Under these enhanced uptake conditions, Hg(II) bioavailability followed a bell shaped curve as DOM concentrations increased, both for defined media and natural water samples, consistent with bioaccumulation results in a companion paper (this issue) observed for amphipods. Experiments also suggest that DOM may not only provide shuttle molecules facilitating Hg uptake, but also alter cell wall properties to facilitate the first steps toward Hg(II) internalization. We propose the existence of a short-lived yet critical time window (<24 h) during which DOM facilitates the entry of newly deposited Hg(II) into aquatic food webs, suggesting that the bulk of mercury incorporation in aquatic food webs would occur within hours following its deposition from the atmosphere.

Characterization of Whole Porewater Dissolved Organic Matter by 1H NMR

NASA Astrophysics Data System (ADS)

Fox, C.; Lewicki, J. P.; Abdulla, H. A.; Burdige, D.; Magen, C.; Chanton, J.; Komada, T.

2014-12-01

Dissolved organic matter (DOM) is a key intermediate in microbial remineralization of organic matter, but only a small percentage of this complex pool has been fully characterized. We present the results of a novel approach to the characterization of DOM in whole porewater samples from the anoxic sediments of the Santa Barbara Basin, California Borderland, using solution state nuclear magnetic resonance (NMR) techniques. Profiles of porewater DOM were obtained by 1H NMR from 95 to 435 cm sediment depth. 1H NMR spectra of each whole porewater sample showed continuous, broad regions from ~0.5 to ~4.5 ppm, indicative of significant signal overlap inherent to complex mixtures, superimposed on a few highly resolved peaks. The individual samples consist of a broad range of chemical environments with varying relative abundances that show a near linear trend with depth. The normalized spectral data were analyzed by principal component analysis to resolve variations in chemical composition of DOM as a function of depth. In addition to detecting the major components such as carbohydrates, cyclic aliphatics and aromatics, our results demonstrate a negative correlation between carbohydrates concurrent with a relative increase in levels of aliphatics. Furthermore, we have identified a decrease in the abundance of alkenes coupled with an increase in a broad region from ~1.9 to ~3.2 ppm, likely corresponding to signals from carboxylic-rich alicyclic molecules. In both trends, the greatest variation occurs between 115 and 135 cm, which straddles the sulfate-methane transition zone (~125 cm), potentially highlighting a region of relatively high DOM transformation. Our work has also identified thiol species which are thought to be formed by dissolved (inorganic) sulfide incorporation into porewater DOM compounds. The implications of these results with respect to carbon cycling in anaerobic sediments will be discussed.

Survival of Acetate in Biodegraded Stream Water DOM: New Insights Based on NMR Spectroscopy

NASA Astrophysics Data System (ADS)

Whitty, S.; Waggoner, D. C.; Bowen, J. C.; Cory, R. M.; Kaplan, L.; Hatcher, P.

2017-12-01

DOM is a complex chemical mixture of high- (HMW) and low-molecular-weight (LMW) organic molecules that serve as the primary energy sources for heterotrophic bacteria in freshwater environments. However, there are still large uncertainties on the composition of DOM that is labile and thus rapidly metabolized. The current thinking is that labile DOM is primarily composed of monosaccharides, amino acids, and other LMW organic acids such as formic, acetic, or propionic among others, although some humic substances also are biologically labile. To test the contribution of LMW organic acids to the labile fraction of DOM, freshwater samples were collected from five streams within the Rio Tempisquito watershed in Costa Rica and subjected to differing degrees of biodegradation using a series of plug-flow bioreactors with residence times ranging from 0.5-150 min. Varying the residence times of bioreactors allows for separation and identification of labile from less labile to more recalcitrant DOM. The stream water fed into the bioreactors had DOC concentrations that ranged from 0.7-1.2 ppm C and the GF/F-filtered stream water as well as the bioreactor effluents were analyzed directly without pre-treatment using proton nuclear magnetic resonance spectroscopy (1H NMR). Small molecules dominated the 1H NMR spectra with the greatest changes, as a function of bioreactor residence time, in the carbohydrate, terminal methyl, and long-chain methylene structures. In contrast, acetate remained relatively constant after 150 min of bioreactor residence time, thus raising the question of why this inherently labile volatile fatty acid was not consumed by stream microbes colonizing bioreactors that otherwise metabolized approximately 35% of the total dissolved organic carbon present in the stream water. We suggest that acetate may resist biodegradation because it is complexed strongly with inorganic cations.

Structural development of the Red Hill portion of the Feather River ultramafic complex, Pulmas County, California

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weisenberg, C.W.

1979-01-01

The Feather River Ultramafic Complex is a partially serpentinized body of metamorphosed alpine peridotite and gabbro that lies along the northern part of the Melones fault zone, a NNW trending belt in the Northern Sierra Nevada. The complex was studied in the area of Red Hill, near the canyon of the North Fork, Feather River. The complex is separated from the Calaveras Terrain and Arlington Formation country rocks by steep faults; the Melones Fault on the east and the Rich Bar Fault on the west. Units recognized within the complex include Rich Bar metamorphic rocks, peridotite, metaperidotite, tremolite-olivine schist, hornblendemore » schist, and layered metagabbro. The Rich Bar metamorphic rocks are tectonic slices of amphibolite grade hornblende schist, mica schist, and quartzite found along the Rich Bar Fault. The complex shows evidence of 4 major events. E-1 (Pennsylvania-Permian) was formation of the peridotite-gabbro complex. E-2 (Permo-Triassic) consisted of pervasive shearing parallel to the Rich Bar Fault associated with initial emplacement within the Sierra Nevada. E-3 is believed to be compression and metamorphism (serpentinization) associated with the Nevadan orogeny. E-4 was associated with intrusion of nearby plutons. The regional association of the complex with late paleozoic arc volcanics of the Taylorsville area suggest formation near or under an island arc. Metamorphism during emplacement indicates association with the arc at that time. Left-lateral shear during emplacement along the Rich Bar Fault indicates NW directed thrusting when the layering in metagabbro is rotated to horizontal.« less

Geochemical modeling of mercury speciation in surface water and implications on mercury cycling in the everglades wetland.

PubMed

Jiang, Ping; Liu, Guangliang; Cui, Wenbin; Cai, Yong

2018-06-01

The geochemical model PHREEQC, abbreviated from PH (pH), RE (redox), EQ (equilibrium), and C (program written in C), was employed on the datasets generated by the USEPA Everglades Regional Environmental Monitoring and Assessment Program (R-EMAP) to determine the speciation distribution of inorganic mercury (iHg) in Everglades water and to explore the implications of iHg speciation on mercury cycling. The results suggest that sulfide and DOM were the key factors that regulate inorganic Hg speciation in the Everglades. When sulfide was present at measurable concentrations (>0.02 mg/L), Hg-S complexes dominated iHg species, occurring in the forms of HgS 2 2- , HgHS 2 - , and Hg(HS) 2 that were affected by a variety of environmental factors. When sulfide was assumed nonexistent, Hg-DOM complexes occurred as the predominant Hg species, accounting for almost 100% of iHg species. However, when sulfide was presumably present at a very low, environmentally relevant concentration (3.2 × 10 -7  mg/L), both Hg-DOM and Hg-S complexes were present as the major iHg species. These Hg-S species and Hg-DOM complex could be related to methylmercury (MeHg) in environmental matrices such floc, periphyton, and soil, and the correlations are dependent upon different circumstances (e.g., sulfide concentrations). The implications of the distribution of iHg species on MeHg production and fate in the Everglades were discussed. Copyright © 2018 Elsevier B.V. All rights reserved.

Extensional unroofing of the metamorphic core of the southern Appalachian orogen prior to the breakup of Pangea: Insights from 40Ar/39Ar thermochronology

NASA Astrophysics Data System (ADS)

Ma, C.; Foster, D. A.; Hames, W. E.; Mueller, P. A.

2017-12-01

Orogenic collapse commonly occurs following the collisional phase of an orogeny and often leads to exhumation of deep crustal metamorphic rocks. The Alleghanian orogeny in the southern Appalachian orogen (SAO) occurred during final assembly of Pangea. 40Ar/39Ar data of hornblende, muscovite, and biotite from Alleghanian granitic plutons in Georgia, Alabama, and Florida of the SAO give cooling ages that progressively young toward the south-southeast prior to ca. 280 Ma and young locally toward the north-northwest after ca. 280 Ma. These cooling-age gradients, along with geometry of the Suwannee suture zone and timing/structures of the South Georgia basin, suggest that metamorphic rocks north of the Suwannee suture in the study area formed the lower plate of a metamorphic core complex. The faults of the Suwannee suture zone were reactivated to form a master extensional detachment fault with the Suwannee terrane comprising the upper plate. Thermochronologic data show that rapid extension of the metamorphic core complex footwall started at ca. 300-295 Ma and the extension continued to at least ca. 240 Ma. The maximum average extension rate is estimated to be 10.3 km/m.y. during ca. 300-280 Ma along the master detachment fault and 2.4 km/m.y. during ca. 280-240 Ma along a secondary detachment fault, reflecting differential extension over time. Main cooling rates of 10‒85˚C/m.y. and exhumation rates of 0.3‒2.8 km/m.y. are calculated for the Alleghanian granitic plutons studied. This work shows that, in the southernmost Appalachians, orogenic collapse resulted in metamorphic core complex-style extension between about 300 and 240 Ma. The horst-and-graben systems of the South Georgia basin formed within the upper plate in this tectonic setting. Metamorphic core complex-style extension, therefore, played a critical role in initial rifting that led to the eventual breakup of Pangea and formation of the Atlantic Ocean and the Gulf of Mexico.

Phase equilibria modelling and zircon dating for Precambrian metapelites from Xinghuadukou Group in Lvlin Forest of Erguna Massif, NE China

NASA Astrophysics Data System (ADS)

Xu, Jiulei; Zheng, Changqing; Tajcmanova, Lucie; Zhong, Xin; Xu, Xuechun; Han, Xiaomeng; Wang, Zhaoyuan

2017-04-01

Xinghuadukou Group, the basement metamorphic complex of Erguna Massif in NE China, is considered to be Mesoproterozoic with Sm-Nd age of 1157±32 Ma. However, the new zircon data from these metamorphic supracrustal rocks in Lvlin Forest show that they formed in Neoproterozoic with the age of 800 Ma. Old zircon age with 2.5 Ga, 2.0 Ga and 1.8 Ga, indicate that the Erguna Massif had an affinity to both Columbia and Rodinia continents. Furthermore, we also present 500 Ma metamorphic age in micashists and 500 Ma age of adjacent granitoids that might have thermally influenced its surrounding. No detailed studies have been undertaken on the metamorphic evolution of the Xinghuadukou Complex. The typical paragneissic mineral assemblage of garnet sillimanite mica schist is Grt+Sil+Bt+Mus+Qtz±Kfs. (Zhou et al., 2011) proposed that the Xinghuadukou Complex appears to have undergone similar granulite facies metamorphic conditions based on the similarity of mineral assemblages to the Mashan Complex in the Jiamusi Massif, NE China. However, the new phase equilibria modelling result shows that these rocks are high amphibolite facies product with 650℃. We can easily find K-feldspar formed by partial melting due to the consuming of muscovite. Also the remaining muscovite is directly connected with a fluid channel in thin sections which indicate that the remaining muscovite formed from retrograde with the existence of fluid. The zoned garnet has low MgO and high CaO content in rims and high MgO and low CaO content in core. It seems that this garnet has high pressure and low temperature (HP-LT) in rims and low pressure and high temperature (LP-HT) in core which would point to an anti-clockwise metamorphic evolution. Zhou, J.B., Wilde, S.A., Zhang, X.Z., Zhao, G.C., Liu, F.L., Qiao, D.W., Ren, S.M. and Liu, J.H., 2011b. A> 1300km late Pan-African metamorphic belt in NE China: new evidence from the Xing'an block and its tectonic implications. Tectonophysics, 509(3): 280-292.

Syn-extensional plutonism and peak metamorphism in the albion-raft river-grouse creek metamorphic core complex

USGS Publications Warehouse

Strickland, A.; Miller, E.L.; Wooden, J.L.; Kozdon, R.; Valley, J.W.

2011-01-01

The Cassia plutonic complex (CPC) is a group of variably deformed, Oligocene granitic plutons exposed in the lower plate of the Albion-Raft River- Grouse Creek (ARG) metamorphic core complex of Idaho and Utah. The plutons range from granodiorite to garnet-bearing, leucogranite, and during intrusion, sillimanite- grade peak metamorphism and ductile attenuation occurred in the country rocks and normal-sense, amphibolite-grade deformation took place along the Middle Mountain shear zone. U-Pb zircon geochronology from three variably deformed plutons exposed in the lower plate of the ARG metamorphic core complex revealed that each zircon is comprised of inherited cores (dominantly late Archean) and Oligocene igneous overgrowths. Within each pluton, a spread of concordant ages from the Oligocene zircon overgrowths is interpreted as zircon recycling within a long-lived magmatic system. The plutons of the CPC have very low negative whole rock ??Nd values of -26 to -35, and initial Sr values of 0.714 to 0.718, consistent with an ancient, crustal source. Oxygen isotope ratios of the Oligocene zircon overgrowths from the CPC have an average ??18O value of 5.40 ?? 0.63 permil (2SD, n = 65) with a slight trend towards higher ??18O values through time. The ??18O values of the inherited cores of the zircons are more variable at 5.93 ?? 1.51 permil (2SD, n = 29). Therefore, we interpret the plutons of the CPC as derived, at least in part, from melting Archean crust based on the isotope geochemistry. In situ partial melting of the exposed Archean basement that was intruded by the Oligocene plutons of the CPC is excluded as the source for the CPC based on field relationships, age and geochemistry. Correlations between Ti and Hf concentrations in zircons from the CPC suggest that the magmatic system may have become hotter (higher Ti concentration in zircon) and less evolved (lower Hf in zircon concentration) through time. Therefore, the CPC represents prolonged or episodic magmatism system (32-25 Ma), and the intrusions were each accompanied by sillimanite-grade deformation and extension. The Oligocene magmatism and peak metamorphism preserved in the ARG metamorphic core complex are likely related to regional trends in mantle-derived magmatism that led to protracted heating, melting and mobilization of the deeper crust.

Multi-spectroscopic investigation on the complexation of tetracycline with dissolved organic matter derived from algae and macrophyte.

PubMed

Bai, Leilei; Zhao, Zhen; Wang, Chunliu; Wang, Changhui; Liu, Xin; Jiang, Helong

2017-11-01

Interactions of antibiotics with algae-derived dissolved organic matter (ADOM) and macrophyte-derived dissolved organic matter (MDOM) are of vital importance to the transport and ecotoxicity of antibiotics in eutrophic freshwater lakes. Multi-spectroscopic techniques were used to investigate the complexation of tetracycline (TTC) with ADOM and MDOM collected from Lake Taihu (China). The 3 fluorescent components, tyrosine-, tryptophan-, and humic-like component, were identified by excitation emission matrix spectra with parallel factor analysis. Their fluorescence was quenched at different degree by TTC titration through static quenching. The complexation of TTC induced conformational changes in DOM fractions. Synchronous fluorescence spectra combined with two dimensional correlation spectroscopy further suggested that the formation of TTC-DOM complexes occurred on the sequential order of tryptophan-like→tyrosine-like→humic-like component. The effective quenching constants of tryptophan- and tyrosine-like component were similar, higher than those of humic-like component. The strong binding ability and abundant content of protein-like substances indicated their prominent role in the TTC-DOM complexation. Fourier transform infrared spectroscopy further revealed that the heterogeneous functional groups, including amide I and II, aromatics, and aliphatics, were responsible for the complexation. These results highlight the significant impact of the overgrowth of algae and macrophyte on the environmental behavior of antibiotics in waters. Copyright © 2017 Elsevier Ltd. All rights reserved.

Protolith and metamorphic ages of the Haiyangsuo Complex, eastern China: A non-UHP exotic tectonic slab in the Sulu ultrahigh-pressure terrane

USGS Publications Warehouse

Liou, J.G.; Tsujimori, T.; Chu, W.; Zhang, R.Y.; Wooden, J.L.

2006-01-01

The Haiyangsuo Complex in the NE Sulu ultrahigh-pressure (UHP) terrane has discontinuous, coastal exposures of Late Archean gneiss with amphibolitized granulite, amphibolite, Paleoproterozoic metagabbroic intrusives, and Cretaceous granitic dikes over an area of about 15 km2. The U-Pb SHRIMP dating of zircons indicates that theprotolith age of a garnet-biotite gneiss is >2500 Ma, whereas the granulite-facie metamorphism occurred at around 1800 Ma. A gabbroic intrusion was dated at ???1730 Ma, and the formation of amphibolite-facies assemblages in both metagabbro and granulite occurred at ???340-460 Ma. Petrologic and geochronological data indicate that these various rocks show no evidence of Triassic eclogite-facies metamorphism and Neoproterozoic protolith ages that are characteristics of Sulu-Dabie HP-UHP rocks, except Neoproterozoic inherited ages from post-collisional Jurassic granitic dikes. Haiyangsuo retrograde granulites with amphibolite-facies assemblages within the gneiss preserve relict garnet formed during granulite-facies metamorphism at ???1.85 Ga. The Paleoproterozoic metamorphic events are almost coeval with gabbroic intrusions. The granulite-bearing gneiss unit and gabbro-dominated unit of the Haiyangsuo Complex were intruded by thin granitic dikes at about 160 Ma, which is coeval with post-collisional granitic intrusions in the Sulu terrane. We suggest that the Haiyangsuo Complex may represent a fragment of the Jiao-Liao-Ji Paleoproterozoic terrane developed at the eastern margin of the Sino-Korean basement, which was juxtaposed with the Sulu terrane prior to Jurassic granitic activity and regional deformation. ?? Springer-Verlag 2006.

[The Influence of Runoff Pollution to DOM Features in an Urban Wastewater Treatment Plant].

PubMed

He, Li; Ji, Fang-ying; Lai, Ming-sheng; Xu, Xuan; Zhou, Wei-wei; Mao, Bo-lin; Yang, Ming-jia

2015-03-01

Combined with wastewater treatment process, the sewage in sunny and rainy day was collected from a wastewater treatment plant in Chongqing. Three-dimensional fluorescence spectra was used to investigate the characteristic fluorescence of dissolved organic matter (DOM). DOM dissolved organic carbon (DOC), chemical oxygen demand (COD), fluorescence index (ƒ450/500) and fluorescence intensity ratio γ (A, C) of fulvic acid in ultraviolet and visible region were used to analyze the impact of rain runoff pollution on sewage DOM. According to the experimental data, the DOM fluorescence fingerprints of this wastewater treatment plant were quite different from typical municipal sewage, and the main component was tryptophan with low excitation wavelength (Peak S), then the tryptophan with long wavelength excitation (Peak T) followed. A2/O process had an approximative degradation of the protein-like both in sunny day and rainy day, but had a better degradation of fulvic-like, DOC and COD in rainy day than that in sunny day. Morever, the fluorescence peaks got red-shifted after the biological treatment. The differences of DOM fluorescence fingerprint between sunny and rainy day were significant, the fluorescence center of UV fulvic (Peak A) in rainy day getting blue-shifted obviously, shifting from 240 - 248/390 - 440 to 240 - 250/370 - 400 nm. Although the DOM types in sunny and rainy day were the same, the source of fulvic got more complex by runoff and the component ratio of DOM also changed. Compared with the sunny day, the proportion of Peak S in DOM dereased by 10%, and the proportion of Peak A increased by 7% in rainy day.

Cation-induced coagulation of aquatic plant-derived dissolved organic matter: Investigation by EEM-PARAFAC and FT-IR spectroscopy.

PubMed

Liu, Shasha; Zhu, Yuanrong; Liu, Leizhen; He, Zhongqi; Giesy, John P; Bai, Yingchen; Sun, Fuhong; Wu, Fengchang

2018-03-01

Complexation and coagulation of plant-derived dissolved organic matter (DOM) by metal cations are important biogeochemical processes of organic matter in aquatic systems. Thus, coagulation and fractionation of DOM derived from aquatic plants by Ca(II), Al(III), and Fe(III) ions were investigated. Metal ion-induced removal of DOM was determined by analyzing dissolved organic carbon in supernatants after addition of these metal cations individually. After additions of metal ions, both dissolved and coagulated organic fractions were characterized by use of fluorescence excitation emission matrix-parallel factor (EEM-PARAFAC) analysis and Fourier transform infrared (FT-IR) spectroscopy. Addition of Ca(II), Fe(III) or Al(III) resulted in net removal of aquatic plant-derived DOM. Efficiencies of removal of DOM by Fe(III) or Al(III) were greater than that by Ca(II). However, capacities to remove plant-derived DOM by the three metals were less than which had been previously reported for humic materials. Molecular and structural features of plant-derived DOM fractions in associations with metal cations were characterized by changes in fluorescent components and infrared absorption peaks. Both aromatic and carboxylic-like organic matters could be removed by Ca(II), Al(III) or Fe(III) ions. Whereas organic matters containing amides were preferentially removed by Ca(II), and phenolic materials were selectively removed by Fe(III) or Al(III). These observations indicated that plant-derived DOM might have a long-lasting effect on water quality and organisms due to its poor coagulation with metal cations in aquatic ecosystems. Plant-derived DOM is of different character than natural organic matter and it is not advisable to attempt removal through addition of metal salts during treatment of sewage. Copyright © 2017 Elsevier Ltd. All rights reserved.

Source to sink characterization of dissolved organic matter in a tropical karst system

NASA Astrophysics Data System (ADS)

Lechleitner, Franziska; Lang, Susan Q.; McIntyre, Cameron; Baldini, James U. L.; Dittmar, Thorsten; Eglinton, Timothy I.

2016-04-01

Karst systems are widespread surface features present on all continents. They are characterized by complex hydrology with a multitude of possible flow regimes, from diffuse seepage through the host rock to fracture flow in larger conduits. As stalagmite proxy records are important indicators of past terrestrial climate conditions, detailed understanding of the biogeochemistry of cave systems and their relationships to the overlying karst network is crucial. Microbial communities that drive the carbon cycle in caves are nourished by dissolved organic matter (DOM) carried with water into the cave system. Water samples from the Yok Balum cave in Belize were collected for DOM analysis, including soil waters, drip waters and pool waters from inside the cave. Additionally, DOM extracts from a stalagmite from the same cave were analysed to examine DOM signatures and test their applicability for reconstruction of environmental conditions. Ultrahigh-resolution mass spectrometry (via the ESI-FT-ICR-MS technique) yielded detailed molecular fingerprints on DOM from these samples. Several thousand molecular formulae of DOM compounds were identified. In addition, radiocarbon analyses were performed on the DOM samples to gain information on karst turnover times. A principal component analysis of the molecular data revealed a clear gradient between soil waters and cave waters, as soil waters were enriched in highly unsaturated oxygen-rich compounds (typical for vascular plants), which were much less abundant in drip waters. Conversely, peptides, which can originate from bacterial processes, were present only in the drip waters. Our data clearly show connectivity between the cave and overlaying soils, and reworking of DOM by the cave bacterial community. Furthermore, we found molecular evidence for the selective removal of vascular plant-derived DOM in the caves, possibly due to abiotic interactions with minerals.

Molecular alteration of marine dissolved organic matter under experimental hydrothermal conditions

NASA Astrophysics Data System (ADS)

Hawkes, Jeffrey A.; Hansen, Christian T.; Goldhammer, Tobias; Bach, Wolfgang; Dittmar, Thorsten

2016-02-01

Marine dissolved organic matter (DOM) is a large (660 Pg) pool of reduced carbon that is subject to thermal alteration in hydrothermal systems and sedimentary basins. In natural high-temperature hydrothermal systems, DOM is almost completely removed, but the mechanism and temperature dependence of this removal have not been studied to date. We investigated molecular-level changes to DOM that was solid-phase extracted (SPE-DOM) from the deep ocean of the North Pacific Ocean. This complex molecular mixture was experimentally exposed to temperatures between 100 and 380 °C over the course of two weeks in artificial seawater, and was then characterised on a molecular level via ultrahigh-resolution Fourier-transform ion cyclotron mass spectrometry (FT-ICR-MS). Almost 93% of SPE-DOM was removed by the treatment at 380 °C, and this removal was accompanied by a consistent pattern of SPE-DOM alteration across the temperatures studied. Higher molecular weight and more oxygen rich compounds were preferentially removed, suggesting that decarboxylation and dehydration of carboxylic acid and alcohol groups are the most rapid degradation mechanisms. Nitrogen containing compounds followed the same overall trends as those containing just C, H and O up to 300 °C. Above this temperature, the most highly altered samples contained very little of the original character of marine DOM, instead being mainly composed of very low intensity N- and S- containing molecules with a high H/C ratio (>1.5). Our results suggest that abiotic hydrothermal alteration of SPE-DOM may already occur at temperatures above 68 °C. Our experiments were conducted without a sedimentary or mineral phase, and demonstrate that profound molecular alteration and almost complete removal of marine SPE-DOM requires nothing more than heating in a seawater matrix.

Chemical fractionation-enhanced structural characterization of marine dissolved organic matter

NASA Astrophysics Data System (ADS)

Arakawa, N.; Aluwihare, L.

2016-02-01

Describing the molecular fingerprint of dissolved organic matter (DOM) requires sample processing methods and separation techniques that can adequately minimize its complexity. We have employed acid hydrolysis as a way to make the subcomponents of marine solid phase-extracted (PPL) DOM more accessible to analytical techniques. Using a combination of NMR and chemical derivatization or reduction analyzed by comprehensive (GCxGC) gas chromatography, we observed chemical features strikingly similar to terrestrial DOM. In particular, we observed reduced alicylic hydrocarbons believed to be the backbone of previously identified carboxylic rich alicyclic material (CRAM). Additionally, we found carbohydrates, amino acids and small lipids and acids.

The timing of tertiary metamorphism and deformation in the Albion-Raft River-Grouse Creek metamorphic core complex, Utah and Idaho

USGS Publications Warehouse

Strickland, A.; Miller, E.L.; Wooden, J.L.

2011-01-01

The Albion-Raft River-Grouse Creek metamorphic core complex of southern Idaho and northern Utah exposes 2.56-Ga orthogneisses and Neoproterozoic metasedimentary rocks that were intruded by 32-25-Ma granitic plutons. Pluton emplacement was contemporaneous with peak metamorphism, ductile thinning of the country rocks, and top-to-thewest, normal-sense shear along the Middle Mountain shear zone. Monazite and zircon from an attenuated stratigraphic section in the Middle Mountain were dated with U-Pb, using a SHRIMP-RG (reverse geometry) ion microprobe. Zircons from the deformed Archean gneiss preserve a crystallization age of 2532 ?? 33 Ma, while monazites range from 32.6 ?? 0.6 to 27.1 ?? 0.6 Ma. In the schist of the Upper Narrows, detrital zircons lack metamorphic overgrowths, and monazites produced discordant U-Pb ages that range from 52.8 ?? 0.6 to 37.5 ?? 0.3 Ma. From the structurally and stratigraphically highest unit sampled, the schist of Stevens Spring, narrow metamorphic rims on detrital zircons yield ages from 140-110 Ma, and monazite grains contained cores that yield an age of 141 ??2 Ma, whereas rims and some whole grains ranged from 35.5 ?? 0.5 to 30.0 ?? 0.4 Ma. A boudinaged pegmatite exposed in Basin Creek is deformed by the Middle Mountains shear zone and yields a monazite age of 27.6 ?? 0.2 Ma. We interpret these data to indicate two periods of monazite and metamorphic zircon growth: a poorly preserved Early Cretaceous period (???140 Ma) that is strongly overprinted by Oligocene metamorphism (???32-27 Ma) related to regional plutonism and extension. ?? 2011 by The University of Chicago.

Fate of 14C-labeled dissolved organic matter in paddy and upland soils in responding to moisture.

PubMed

Chen, Xiangbi; Wang, Aihua; Li, Yang; Hu, Lening; Zheng, Hua; He, Xunyang; Ge, Tida; Wu, Jinshui; Kuzyakov, Yakov; Su, Yirong

2014-08-01

Soil organic matter (SOM) content in paddy soils is higher than that in upland soils in tropical and subtropical China. The dissolved organic matter (DOM) concentration, however, is lower in paddy soils. We hypothesize that soil moisture strongly controls the fate of DOM, and thereby leads to differences between the two agricultural soils under contrasting management regimens. A 100-day incubation experiment was conducted to trace the fate and biodegradability of DOM in paddy and upland soils under three moisture levels: 45%, 75%, and 105% of the water holding capacity (WHC). (14)C labeled DOM, extracted from the (14)C labeled rice plant material, was incubated in paddy and upland soils, and the mineralization to (14)CO2 and incorporation into microbial biomass were analyzed. Labile and refractory components of the initial (14)C labeled DOM and their respective half-lives were calculated by a double exponential model. During incubation, the mineralization of the initial (14)C labeled DOM in the paddy soils was more affected by moisture than in the upland soils. The amount of (14)C incorporated into the microbial biomass (2.4-11.0% of the initial DOM-(14)C activity) was less affected by moisture in the paddy soils than in the upland soils. At any of the moisture levels, 1) the mineralization of DOM to (14)CO2 within 100 days was 1.2-2.1-fold higher in the paddy soils (41.9-60.0% of the initial DOM-(14)C activity) than in the upland soils (28.7-35.7%), 2) (14)C activity remaining in solution was significantly lower in the paddy soils than in the upland soils, and 3) (14)C activity remaining in the same agricultural soil solution was not significantly different among the three moisture levels after 20 days. Therefore, moisture strongly controls DOM fate, but moisture was not the key factor in determining the lower DOM in the paddy soils than in the upland soils. The UV absorbance of DOM at 280 nm indicates less aromaticity of DOM from the paddy soils than from the upland soils. At any of the moisture levels, much more labile DOM was found in paddy soils (34.3-49.2% of the initial (14)C labeled DOM) compared with that in upland soils (19.4-23.9%). This demonstrates that the lower DOM content in the paddy soil compared with that in the upland soil is probably determined by the less complex components and structure of the DOM. Copyright © 2014 Elsevier B.V. All rights reserved.

The behaviour of monazite from greenschist facies phyllites to anatectic gneisses: An example from the Chugach Metamorphic Complex, southern Alaska

PubMed Central

Gasser, Deta; Bruand, Emilie; Rubatto, Daniela; Stüwe, Kurt

2012-01-01

Monazite is a common accessory mineral in various metamorphic and magmatic rocks, and is widely used for U–Pb geochronology. However, linking monazite U–Pb ages with the PT evolution of the rock is not always straightforward. We investigated the behaviour of monazite in a metasedimentary sequence ranging from greenschist facies phyllites into upper amphibolites facies anatectic gneisses, which is exposed in the Eocene Chugach Metamorphic Complex of southern Alaska. We investigated textures, chemical compositions and U–Pb dates of monazite grains in samples of differing bulk rock composition and metamorphic grade, with particular focus on the relationship between monazite and other REE-bearing minerals such as allanite and xenotime. In the greenschist facies phyllites, detrital and metamorphic allanite is present, whereas monazite is absent. In lower amphibolites facies schists (~ 550–650 °C and ≥ 3.4 kbar), small, medium-Y monazite is wide-spread (Mnz1), indicating monazite growth prior and/or simultaneous with growth of garnet and andalusite. In anatectic gneisses, new low-Y, high-Th monazite (Mnz2) crystallised from partial melts, and a third, high-Y, low-Th monazite generation (Mnz3) formed during initial cooling and garnet resorption. U–Pb SHRIMP analysis of the second and third monazite generations yields ages of ~ 55–50 Ma. Monazite became unstable and was overgrown by allanite and/or allanite/epidote/apatite coronas within retrograde muscovite- and/or chlorite-bearing shear zones. This study documents polyphase, complex monazite growth and dissolution during a single, relatively short-lived metamorphic cycle. PMID:26525358

Domesticated, Genetically Engineered, and Wild Plant Relatives Exhibit Unintended Phenotypic Differences: A Comparative Meta-Analysis Profiling Rice, Canola, Maize, Sunflower, and Pumpkin

PubMed Central

Hernández-Terán, Alejandra; Wegier, Ana; Benítez, Mariana; Lira, Rafael; Escalante, Ana E.

2017-01-01

Agronomic management of plants is a powerful evolutionary force acting on their populations. The management of cultivated plants is carried out by the traditional process of human selection or plant breeding and, more recently, by the technologies used in genetic engineering (GE). Even though crop modification through GE is aimed at specific traits, it is possible that other non-target traits can be affected by genetic modification due to the complex regulatory processes of plant metabolism and development. In this study, we conducted a meta-analysis profiling the phenotypic consequences of plant breeding and GE, and compared modified cultivars with wild relatives in five crops of global economic and cultural importance: rice, maize, canola, sunflower, and pumpkin. For these five species, we analyzed the literature with documentation of phenotypic traits that are potentially related to fitness for the same species in comparable conditions. The information was analyzed to evaluate whether the different processes of modification had influenced the phenotype in such a way as to cause statistical differences in the state of specific phenotypic traits or grouping of the organisms depending on their genetic origin [wild, domesticated with genetic engineering (domGE), and domesticated without genetic engineering (domNGE)]. In addition, we tested the hypothesis that, given that transgenic plants are a construct designed to impact, in many cases, a single trait of the plant (e.g., lepidopteran resistance), the phenotypic differences between domGE and domNGE would be either less (or inexistent) than between the wild and domesticated relatives (either domGE or domNGE). We conclude that (1) genetic modification (either by selective breeding or GE) can be traced phenotypically when comparing wild relatives with their domesticated relatives (domGE and domNGE) and (2) the existence and the magnitude of the phenotypic differences between domGE and domNGE of the same crop suggest consequences of genetic modification beyond the target trait(s). PMID:29259610

Metamorphic P-T conditions across the Chugach Metamorphic Complex (Alaska)—A record of focussed exhumation during transpression

NASA Astrophysics Data System (ADS)

Bruand, Emilie; Gasser, Deta; Stüwe, Kurt

2014-03-01

The Chugach Metamorphic Complex (CMC) is a large high-grade metamorphic complex that developed in the Eocene within the Chugach accretionary complex along the margin of Alaska where subduction is still ongoing. The CMC has a conspicuous asymmetric structure with a migmatitic zone flanked in the north and west by amphibolite facies schists and in the south by a metabasite belt. To the north and south, major, crustal-scale fault zones juxtapose the Chugach terrane against much lower-grade and less-deformed sequences belonging to different terranes. Curiously these crustal-scale structures are known to have largely strike slip motion posing the question as to the nature of the exhumation of the high-grade complex between them. However, P-T conditions which would allow an estimation of the amount of exhumation were lacking for large parts of the complex. This paper presents petrographic descriptions, biotite-garnet thermometry, RSCM thermometry, average P-T calculations and pseudosection modelling from three major across-strike transects covering the complex from west to south-east. Our results reveal that, both temperature and pressure vary substantially across the complex. More specifically, peak metamorphic conditions evolve from 4-7 kbar and ~ 550-650 °C in the northern schist zone to 5-11 kbar and ~ 650-750 °C in the migmatite zone in the south of the complex. The higher pressure estimates in the south of the complex indicate that focussed exhumation must have occurred in this area and was probably initiated by the subduction of a high topographic relief (intra-oceanic arc or ridge subduction) and the accretion of the metabasite belt in the south. Exhumation of the CMC occurred in an overall transpressive strain regime, with strike-slip deformation concentrated along the northern Border Range fault zone and thrusting and exhumation focussed within the southern migmatite zone and splay faults of the Contact fault zone. The T/P ratios in the southern migmatite zone indicate that the thermal perturbation of the migmatites is less than previously inferred. These new results, associated with the structural data and the accretion of a metabasite belt in the south of the complex, seem incompatible with the existing ridge-subduction models.

Trace Metal-Humic Complexes in Natural Waters: Insights From Speciation Experiments

NASA Astrophysics Data System (ADS)

Stern, J. C.; Salters, V.; Sonke, J.

2006-12-01

The DOM cycle is intimately linked to the cycling and bioavailability of trace metals in aqueous environments. The presence or absence of DOM in the water column can determined whether trace elements will be present in limited quantities as a nutrient, or in surplus quantities as a toxicant. Humic substances (HS), which represent the refractory products of DOM degradation, strongly affect the speciation of trace metals in natural waters. To simulate metal-HS interactions in nature, experiments must be carried out using trace metal concentrations. Sensitive detection systems such as ICP-MS make working with small (nanomolar) concentrations possible. Capillary electrophoresis coupled with ICP-MS (CE-ICP-MS) has recently been identified as a rapid and accurate method to separate metal species and calculate conditional binding constants (log K_c) of metal-humic complexes. CE-ICP-MS was used to measure partitioning of metals between humic substances and a competing ligand (EDTA) and calculate binding constants of rare earth element (REE) and Th, Hf, and Zr-humic complexes at pH 3.5-8 and ionic strength of 0.1. Equilibrium dialysis ligand exchange (EDLE) experiments to validate the CE-ICP-MS method were performed to separate the metal-HS and metal-EDTA species by partitioning due to size exclusion via diffusion through a 1000 Da membrane. CE-ICP-MS experiments were also conducted to compare binding constants of REE with humic substances of various origin, including soil, peat, and aquatic DOM. Results of our experiments show an increase in log K_c with decrease in ionic radius for REE-humic complexes (the lanthanide contraction effect). Conditional binding constants of tetravalent metal-humic complexes were found to be several orders of magnitude higher than REE-humic complexes, indicating that tetravalent metals have a very strong affinity for humic substances. Because thorium is often used as a proxy for the tetravalent actinides, Th-HS binding constants can allow us to assess the importance of tetravalent actinide-humic complexes in groundwater transport from nuclear repositories. Our results suggest that tetravalent actinide-humic complexes couild be more important to account for in predictive speciation models than previously thought.

UHP metamorphism in Greece: Petrologic data from the Rhodope Mountains

NASA Astrophysics Data System (ADS)

Baziotis, I. P.; Mposkos, E.; Krohe, A.; Wawrzenitz, N. H.; Liu, Y.; Taylor, L. A.

2012-12-01

Metamorphic rocks contain invaluable information for understanding the orogenic mechanisms of a tectonic regime. It is now well recorded and recognized that subduction of oceanic lithosphere and collision of continental blocks can result in sinking of subducted rocks to deeper levels than normal (>100 km). Further, the discovery of coesite and diamond in apparently regionally metamorphosed rocks provoked issues, for returning these rocks to the surface relatively fast, thereby preserving the UHP conditions. These UHPM terrains have been identified in more than twenty provinces worldwide. In Greece, UHPM rocks occur in the Rhodope area, one of the major tectono-metamorphic units located in NE Greece. This region consists of different metamorphic complexes involved in the Alpine collisional history between the Eurasian and African plates (e.g., Krohe & Mposkos, 2002-Geol Soc London Spec Pub, 204, 151). In Rhodope, a Jurassic UHP metamorphism is confirmed in the uppermost Kimi and the underlying Sidironero complexes (Mposkos & Kostopoulos, 2001- EPSL, 192, 497; Perraki et al., 2004-5th ISEMG, T2-35, 2006- EPSL, 241, 672; Liati, 2005- Con Min Pet, 150, 608; Bauer et al., 2007- Lithos, 99, 207). UHP metamorphism is evidenced by the presence of octahedral microdiamond inclusions (3 to 10 μm) in protective garnets, within the metapelitic gneisses. Microdiamonds probably formed from a supercritical fluid under extreme P-T conditions. The latter is strengthened by the presence of composite inclusions consisting of CO2, calcite, and microdiamonds. Other UHP indicators include: 1) quartz rods and rutile needle exsolutions in metapelitic garnet, suggesting a former titaniferous super-silicic (majoritic) garnet formed at P >4GPa; 2) oriented quartz lamellae in eclogitic clinopyroxene having been exsolved from a former super-silicic UHP precursor; and 3) coesite pseudomorphs in garnet, where radial cracks around multi-crystalline-quartz aggregates are indicative of the former coesite existence (e.g., Mposkos & Krohe, 2006- Can J Earth Sci, 43, 1755). Jurassic UHP rocks are overprinted by late Jurassic/early Cretaceous HP granulite facies metamorphism (P >1.5GPa; T~900 oC). In the Eastern and Western Rhodope, exhumation of these rocks occurred along different P-T paths. In the eastern Rhodope (Kimi Complex), UHP rocks re-equilibrated under relatively static annealing conditions and emerged at the surface in the Eocene. In the western Rhodope (Sidironero Complex), these rocks have been subjected to an overprinting Eocene MP to HP metamorphism, followed by exhumation along a major shear zone at about 40 Ma. In either case, a long-lasting post-UHP metamorphic history retrograded and almost completely destroyed the UHP minerals, thereby limiting the UHP record mainly to textural evidences and scarce UHP polymorphs. Consequently, some of the micro-diamonds have been partially or fully graphitized during this extensive exhumation period.

Fluorescence-based proxies for lignin in freshwater dissolved organic matter

USGS Publications Warehouse

Hernes, Peter J.; Bergamaschi, Brian A.; Eckard, Robert S.; Spencer, Robert G.M.

2009-01-01

Lignin phenols have proven to be powerful biomarkers in environmental studies; however, the complexity of lignin analysis limits the number of samples and thus spatial and temporal resolution in any given study. In contrast, spectrophotometric characterization of dissolved organic matter (DOM) is rapid, noninvasive, relatively inexpensive, requires small sample volumes, and can even be measured in situ to capture fine-scale temporal and spatial detail of DOM cycling. Here we present a series of cross-validated Partial Least Squares models that use fluorescence properties of DOM to explain up to 91% of lignin compositional and concentration variability in samples collected seasonally over 2 years in the Sacramento River/San Joaquin River Delta in California, United States. These models were subsequently used to predict lignin composition and concentration from fluorescence measurements collected during a diurnal study in the San Joaquin River. While modeled lignin composition remained largely unchanged over the diurnal cycle, changes in modeled lignin concentrations were much greater than expected and indicate that the sensitivity of fluorescence-based proxies for lignin may prove invaluable as a tool for selecting the most informative samples for detailed lignin characterization. With adequate calibration, similar models could be used to significantly expand our ability to study sources and processing of DOM in complex surface water systems.

Illuminating the dark side of DOM: A bottom up approach to understanding the structure and composition of DOM.

NASA Astrophysics Data System (ADS)

Zito, P.; Tarr, M. A.; Spencer, R. G.; Podgorski, D. C.

2017-12-01

Dissolved organic matter (DOM) is one of the most complex natural mixtures on Earth. It is generally comprised of hydrocarbons incorporating a diverse subset of oxygen-containing functional groups along with a small amount of nitrogen, sulfur and phosphorous heteroatoms all of which make it very difficult to chromatographically separate. The only way to directly characterize and quantify these structural and compositional changes is by separating the DOM continuum into defined bins of structure and chemistry. In this study, we take an alternate bottom-up approach that utilizes petroleum to work toward identifying the molecular structures of DOM. Although petroleum is the most structurally diverse mixture in nature, it is almost exclusively comprised of hydrocarbons with only trace quantities of heteroatoms, including oxygen. Here, crude oil was chromatographically separated into bins based on the number of aromatic rings to be used as a starting carbon source. Photochemically produced DOM from these aromatic ring bins provides unique opportunities to gain insight in the compositional controls associated with transport, processing and fate of DOM in natural systems. Here, we present EEMs data from individual ring fractions that were subjected to 24 hours of sunlight to use as a model to fingerprint specific aromatic regions in the DOM fraction. Results illustrate that the 1-, 2-, 3-, 4- and 5- ring fractions exhibit a wide range of structurally dependent excitation and emission spectra. A well-known red-shift in the emission and excitation occurs as the number of rings increase. In order to understand changes in the elemental composition of the data, ultra high-resolution mass spectrometry was used to obtain molecular level information. Together, these data will provide a tool to help understand the relationship of the composition and structure of DOM released into the environment in terms of aromaticity. It is well known that aromaticity is an important indicator of the chemical characteristics of DOM and can be used to explain the role of DOM in environmental processes. Thus, identifying these compounds in terms of aromaticity after photodegradation will provide information about the fate, transport and mechanisms of the photolabile and recalcitrant compounds in the environment.

Spatial variation of dissolved organic matter composition and characteristics in an urbanized watershed

NASA Astrophysics Data System (ADS)

Hsieh, C.; Li, M.

2013-12-01

Dissolved organic matter (DOM) is a chemically complex mixture of organic polymers that plays an important role in river ecosystems and originates from various sources. Some DOMs are autochthonous originating through phytoplankton and microbial activity in situ. On the other hand, some DOMs are allochthonous which are transported to river from the surrounding watershed by natural or anthropogenic activities. The studies of DOM in river are usually conducted at the watershed scale; however, factors of local spatial scale affecting DOM composition also need to take into consideration for the study of DOM in an urbanized watershed. Through increasing urbanization, changes in a watershed occur not only in land use patterns but also in river channel characteristics. The objective of this study is to investigate effects of different river channel characteristics and patterns on changes in DOM source and composition. In this study, we chose three tributaries of Tamsui river in Taiwan according to its land use pattern and river channel characteristics. At each sub-basin, river water samples were sampled from three study sites. River water DOM was measured by using optical measurements of UV absorption and fluorescence spectroscopy. Water samples were also collected for laboratory analysis of different water quality parameters. From our study sites, they are from three sub-basins which are in the similar physical environments but with different river channel types: the highly channelized Keelung river, the less channelized Xindian river, and less channelized Dahan river with five human-made wetlands. From the upstream to the urbanized downstream, composition of DOM showed variation among different sampled sites. In all three sub-basins, the trends of 5-day biochemical oxygen demand (BOD5) and suspended solids (SS) are also different. The changes in DOM source and composition as well as different water quality parmaters occur at the local spatial-scale depended on their river channel characters in urbanized watersheds. Based on our result, it indicates river channel characters which can have effects on biogeochemical processes of DOM. This knowledge can help us in understanding biogeochemical processes controlled or manipulated by anthropogenic activities at different spatial scales, and help us to make an integrative river health management in a watershed.

U-Pb age of the Diana Complex and Adirondack granulite petrogenesis

USGS Publications Warehouse

Basu, A.R.; Premo, W.R.

2001-01-01

U-Pb isotopic analyses of eight single and multi-grain zircon fractions separated from a syenite of the Diana Complex of the Adirondack Mountains do not define a single linear array, but a scatter along a chord that intersects the Concordia curve at 1145 ?? 29 and 285 ?? 204 Ma. For the most concordant analyses, the 207Pb/206Pb ages range between 1115 and 1150 Ma. Detailed petrographic studies revealed that most grains contained at least two phases of zircon growth, either primary magmatic cores enclosed by variable thickness of metamorphic overgrowths or magmatic portions enclosing presumably older xenocrystic zircon cores. The magmatic portions are characterized by typical dipyramidal prismatic zoning and numerous black inclusions that make them quite distinct from adjacent overgrowths or cores when observed in polarizing light microscopy and in back-scattered electron micrographs. Careful handpicking and analysis of the "best" magmatic grains, devoid of visible overgrowth of core material, produced two nearly concordant points that along with two of the multi-grain analyses yielded an upper-intercept age of 1118 ?? 2.8 Ma and a lower-intercept age of 251 ?? 13 Ma. The older age is interpreted as the crystallization age of the syenite and the younger one is consistent with late stage uplift of the Appalachian region. The 1118 Ma age for the Diana Complex, some 35 Ma younger than previously believed, is now approximately synchronous with the main Adirondack anorthosite intrusion, implying a cogenetic relationship among the various meta-igneous rocks of the Adirondacks. The retention of a high-temperature contact metamorphic aureole around Diana convincingly places the timing of Adirondack regional metamorphism as early as 1118 Ma. This result also implies that the sources of anomalous high-temperature during granulite metamorphism are the syn-metamorphic intrusions, such as the Diana Complex.

Revised nomenclature and stratigraphic relationships of the Fredericksburg Complex and Quantico Formation of the Virginia Piedmont

USGS Publications Warehouse

Pavlides, Louis

1980-01-01

The Fredericksburg Complex, in part a migmatitic terrane in northeast Virginia, is subdivided on the basis of lithology, as well as aeromagnetic and aeroradiometric data, into two metamorphic suites. These suites are separated by the northeast-trending Spotsylvania lineament, a rectilinear geophysical feature that is probably the trace of an old fault zone. East of the lineament, the Po River Metamorphic Suite, of Proterozoic Z and (or) early Paleozoic age, consists dominantly of biotite gneiss, generally augen gneiss, and lesser amounts of hornblende gneiss and mica schist. West of the Spotsylvania lineament is the Ta River Metamorphic Suite, composed mostly of amphibolite and amphibole gneiss. However, to the southwest, along its strike belt, the Ta River contains abundant biotite gneiss and mica schist. Both the Ta River and Po River contain abundant foliated granitoid and pegmatoid bodies as concordant tabular masses and as crosscutting dikes; these rocks are considered part of the Ta River and Po River Metamorphic Suites. The amphibolitic Holly Corner Gneiss is interpreted to be a western allochthonous equivalent of the Ta River. Both the Ta River and Holly Corner are considered to be coeval, eastern, distal facies of the Lower Cambrian(?) Chopawamsic Formation. The Paleozoic Falls Run Granite Gneiss intrudes the Ta River Metamorphic Suite and the Holly Corner Gneiss; locally the Falls Run is interpreted to have been transported westward with the Holly Corner after intrusion. The Quantico Formation, in the core of the Quantico-Columbia synclinorium, rests with angular unconformity along its northwest and southeast limbs, respectively, on the Chopawamsic Formation and the Ta River Metamorphic Suite. The Quantico Formation is assigned the same Late Ordovician age and similar stratigraphic position as the Arvonia Slate of the Arvonia syncline. The youngest rocks of the area are the granitoid and pegmatoid bodies of the Falmouth Intrusive Suite. They consist of several generations of chiefly dikes and sills that are intrusive into the Fredericksburg Complex and into the Quantico Formation. Granitoid rocks also form small plutons. The Falmouth is isotopically dated as Carboniferous in age. Some of the metavolcanic rocks of the Evington Group and part of the amphibolite gneiss and amphibolite of the Hatcher Complex, named by W. B. Brown in 1969, are probably coeval with the Chopawamsic Formation and hence equivalents of the Ta River Metamorphic Suite and the Holly Corner Gneiss. The biotitic gneiss and granitoid rocks east of the Spotsylvania lineament in the Dillwyn area are considered to be coeval with the Po River Metamorphic Suite.

Late Mesoproterozoic to Early Paleozoic history of metamorphic basement from the southeastern Chiapas Massif Complex, Mexico, and implications for the evolution of NW Gondwana

NASA Astrophysics Data System (ADS)

Weber, Bodo; González-Guzmán, Reneé; Manjarrez-Juárez, Román; Cisneros de León, Alejandro; Martens, Uwe; Solari, Luigi; Hecht, Lutz; Valencia, Victor

2018-02-01

In this paper, U-Pb zircon geochronology, Lu-Hf and Sm-Nd isotope systematics, geochemistry and geothermobarometry of metaigneous basement rocks exposed in the southeastern Chiapas Massif Complex are presented. Geologic mapping of the newly defined "El Triunfo Complex" located at the southeastern edge of the Chiapas Massif reveals (1) partial melting of a metamorphic basement mainly constituted by mafic metaigneous rocks (Candelaria unit), (2) an Ediacaran metasedimentary sequence (Jocote unit), and (3) occurrence of massif-type anorthosite. All these units are intruded by undeformed Ordovician plutonic rocks of the Motozintla suite. Pressure and temperature estimates using Ca-amphiboles, plagioclase and phengite revealed prograde metamorphism that reached peak conditions at 650 °C and 6 kbar, sufficient for partial melting under water saturated conditions. Relict rutile in titanite and clinopyroxene in amphibolite further indicate a previous metamorphic event at higher P-T conditions. U-Pb zircon ages from felsic orthogneiss boudins hosted in deformed amphibolite and migmatite yield crystallization ages of 1.0 Ga, indicating that dry granitic protoliths represent remnants of Rodinia-type basement. Additionally, a mid-Tonian ( 920 Ma) metamorphic overprint is suggested by recrystallized zircon from a banded gneiss. Zircon from folded amphibolite samples yield mainly Ordovician ages ranging from 457 to 444 Ma that are indistinguishable from the age of the undeformed Motozintla plutonic suite. Similar ages between igneous- and metamorphic- zircon suggest a coeval formation during a high-grade metamorphic event, in which textural discrepancies are explained in terms of differing zircon formation mechanisms such as sub-solidus recrystallization and precipitation from anatectic melts. In addition, some amphibolite samples contain inherited zircon yielding Stenian-Tonian ages around 1.0 Ga. Lu-Hf and Sm-Nd isotopes and geochemical data indicate that the protoliths of the amphibolite have E-MORB characteristics and were derived from a depleted mantle source younger than the Rodinia-type basement. Inasmuch as similar amphibolites also occur in the Ediacaran metasedimentary rocks as dykes or lenses, Late Neoproterozoic magmatism in a rift setting is suggested. Hence, the geologic record of the El Triunfo Complex includes evidences for Rodinia assemblage, Tonian circum-Rodinia subduction, and breakup during the Late Neoproterozoic. Metamorphism, and partial melting are interpreted in terms of a convergent margin setting during the Ordovician. The results place the southern Chiapas Massif along with Oaxaquia and similar Northern Andes terranes on the NW margin of Gondwana interpreted as the extension of the Famatinian orogen that evolved during the closure of the Iapetus Ocean.

Biogeochemical Processes That Produce Dissolved Organic Matter From Wheat Straw

USGS Publications Warehouse

Wershaw, Robert L.; Rutherford, David W.; Leenheer, Jerry A.; Kennedy, Kay R.; Cox, Larry G.; Koci, Donald R.

2003-01-01

The chemical reactions that lead to the formation of dissolved organic matter (DOM) in natural waters are poorly understood. Studies on the formation of DOM generally are complicated because almost all DOM isolates have been derived from mixtures of plant species composed of a wide variety of different types of precursor compounds for DOM formation. This report describes a study of DOM derived mainly from bales of wheat straw that had been left in a field for several years. During this period of time, black water from the decomposing wheat straw accumulated in pools in the field. The nuclear magnetic resonance and infrared spectra of the black water DOM indicate that it is composed almost entirely of lignin and carbohydrate polymeric units. Analysis by high-performance size-exclusion chromatography with multi-angle laser-light scattering detection indicates that the number average molecular weight of the DOM is 124,000 daltons. The results presented in this report indicate that the black water DOM is composed of hemicellulose chains cross-linked to lignin oligomers. These types of structures have been shown to exist in the hemicellulose matrix of plant cell walls. The cross-linked lignin-hemicellulose complexes apparently were released from partially degraded wheat-straw cell walls with little alteration. In solution in the black water, these lignin-hemicellulose polymers fold into compact globular particles in which the nonpolar parts of the polymer form the interiors of the particles and the polar groups are on the exterior surfaces of the particles. The tightly folded, compact conformation of these particles probably renders them relatively resistant to microbial degradation. This should be especially the case for the aromatic lignin structures that will be buried in the interiors of the particles.

Fractionation and characterization of dissolved organic matter (DOM) in refinery wastewater by revised phase retention and ion-exchange adsorption solid phase extraction followed by ESI FT-ICR MS.

PubMed

Fang, Zhi; He, Chen; Li, Yongyong; Chung, Keng H; Xu, Chunming; Shi, Quan

2017-01-01

Although the progress of high resolution mass spectrometry in the past decade has enabled the molecular characterization of dissolved organic matter (DOM) in water as a whole, fractionation of DOM is necessary for a comprehensive characterization due to its super-complex nature. Here we proposed a method for the fractionation of DOM in a wastewater based on solubility and acidic-basic properties. Solid phase extraction (SPE) cartridges with reversed phase retention and ion-exchange adsorption capacities, namely MAX and MCX, were used in succession to fractionate a petroleum refinery wastewater into four fractions: hydrophobic acid (HOA), hydrophobic neutral (HON), hydrophobic base (HOB), and hydrophilic substance (HIS) fractions. According to the total organic carbon (TOC) analysis, 72.6% (in term of TOC) of DOM was extracted in hydrophobic fractions, in which HON was the most abundant. Hydrophobic extracts were characterized by negative and positive ion electrospray (ESI) Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), respectively. Compounds with multiple oxygen atoms were predominant in the HOA, which were responded strongly in the negative ESI MS. Nitrogen containing compounds were the major detected species by positive ion ESI in all hydrophobic fractions. The molecular composition of the DOM were discussed based on the FT-ICR MS results. The fractionation provided salt free samples which enables the direct analysis of the fractions by ESI and a deep insight into the molecular composition of DOM in the wastewater. The method is potential for routine evaluation of DOM in industry wastewaters, as well as environmental water samples. Copyright © 2016. Published by Elsevier B.V.

Molecular Alteration of Marine Dissolved Organic Matter under Experimental Hydrothermal Conditions

NASA Astrophysics Data System (ADS)

Hawkes, J. A.; Hansen, C. T.; Goldhammer, T.; Bach, W.; Dittmar, T.

2016-02-01

Marine dissolved organic matter (DOM) is a large (660 Pg) pool of reduced carbon that is subject to thermal alteration in hydrothermal systems and sedimentary basins. In natural hydrothermal systems, DOM is almost completely removed, but the mechanism, kinetics and temperature dependence of this removal have not been studied to date. We investigated molecular-level changes to DOM that was solid-phase extracted (SPE-DOM) from the deep ocean of the North Pacific Ocean. This complex molecular mixture was experimentally exposed to temperatures between 100-380 °C over the course of two weeks in artificial seawater, and was then characterized on a molecular level via ultrahigh-resolution mass spectrometry (FTICRMS & Orbitrap). Almost 93% of SPE-DOM was removed by the treatment at 380 °C, and this removal was accompanied by a consistent pattern of SPE-DOM alteration across the temperatures studied, which can likely be extrapolated down to temperatures around 68 °C. Higher molecular weight and more oxygen rich compounds were preferentially degraded, suggesting that decarboxylation and dehydration of carboxylic acid and alcohol groups are the most rapid degradation mechanisms. Nitrogen containing compounds followed the same overall trends as those containing just C, H and O up to 300 °C. Above this temperature, the most highly degraded samples contained very little of the original character of marine DOM, instead being mainly composed of very low intensity N- and S- containing molecules with a high H:C ratio (>1.5). Our experiments were conducted without a sedimentary or mineral phase, and demonstrate that profound molecular alteration and almost complete removal of marine SPE-DOM requires nothing more than heating in a seawater matrix.

Molecular characterization of dissolved organic matter in contrasted freshwater environments by electrospray ionization mass spectrometry and EEM-PARAFAC

NASA Astrophysics Data System (ADS)

Parot, Jérémie; Parlanti, Edith; Guéguen, Céline

2015-04-01

Dissolved organic matter (DOM) is a key parameter in the fate, transport and mobility of inorganic and organic pollutants in natural waters. Excitation emission matrix (EEM) spectra coupled to parallel factor analysis (PARAFAC) provide insights on the main fluorescent DOM constituents. However, the molecular structures associated with PARAFAC DOM remain poorly understood. In this study, DOM from rivers, marshes and algal culture was characterized by EEM-PARAFAC and electrospray ionization Fourier transform mass spectrometry (ESI-FT-MS, Orbitrap Q Exactive). The high resolution of the Orbitrap (i.e. 140,000) allowed us to separate unique molecular species from the complex DOM mixtures. The majority of chemical species were found within the mass to charge ratio (m/z) 200 to 400. Weighted averages of neutral mass were 271.254, 236.480, 213.992Da for river, marsh and algal-derived DOM, respectively, congruent with previous studies. The assigned formula were dominated by CHO in humic-rich river waters whereas N- and S-containing compounds were predominant in marsh and algal samples. Marsh consisted of N and S-containing compounds, which were presumed to be linear alkylbenzene sulfonates. And the double bond equivalent (DBE) was higher in the marsh and in comparison was lower in the algal culture. Kendrick masses, used to identify homologous compounds differing only by a number of base units in high resolution mass spectra, and Van Krevelen diagrams, plot of molar ratio of hydrogen to carbon (H/C) versus oxygen to carbon (O/C), will be discussed in relation to PARAFAC components to further discriminate freshwater systems based on the origin and maturity of DOM. Together, these results showed that ESI-FT-MS has a great potential to distinguish freshwater DOM at the molecular level without any fractionation.

Petrography and zircon U-Pb isotopic study of the Bayanwulashan Complex: Constrains on the Paleoproterozoic evolution of the Alxa Block, westernmost North China Craton

NASA Astrophysics Data System (ADS)

Wu, Sujuan; Hu, Jianmin; Ren, Minghua; Gong, Wangbin; Liu, Yang; Yan, Jiyuan

2014-11-01

The Bayanwulashan Metamorphic Complex (BMC) exposes along the eastern margin of the Alxa Block, the westernmost part of the North China Craton (NCC). BMC is principally composed of metamorphic rocks with amphibole plagiogneiss, biotite plagioclase gneiss and granitic gneiss. Our research has been focused on the petrography and zircon U-Pb geochronology of the BMC to better understand the evolution of the Alxa Block and its relationship with the NCC. Evidences from field geology, petrography, and mineral chemistry indicate that two distinct metamorphic assemblages, the amphibolite and greenschist facies, had overprinted the preexisting granitic gneiss and suggest that the BMC experienced retrograde metamorphic episodes. The LA-ICP-MS zircon U-Pb ages reveal that the primary magmatic activities of BMC were at ca. 2.30-2.24 Ga and the two metamorphic events were at ca. 1.95-1.91 Ga and ca. 1.88-1.85 Ga respectively. These ages indicate that BMC initially intruded during Paleoproterozoic, not as previously suggested at Archean period. The Early Paleoproterozoic metamorphic records and the magmatic thermochronological data in BMC exhibit different evolution paths between the Alxa Block and the NCC. The Alxa Block was most likely an independent Early Paleoproterozoic terrain. Following different amalgamation processes, The Alxa Block combined with Western Block at ca. 1.95 Ga and then united with NCC at ca. 1.85 Ga.

Characterization and copper binding of humic and nonhumic organic matter isolated from the South Platte River: Evidence for the presence of nitrogenous binding site

USGS Publications Warehouse

Croue, J.-P.; Benedetti, M.F.; Violleau, D.; Leenheer, J.A.

2003-01-01

Humic substances typically constitute 40-60% of the dissolved organic matter (DOM) in surface waters. However, little information is available regarding the metal binding properties of the nonhumic hydrophilic portion of the DOM. In this study, humic and nonhumic DOM samples were isolated from the South Platte River (Colorado, DOC = 2.6 mg??L-1, SUVA254 = 2.4 L/mg??m) using a two-column array of XAD-8 and XAD-4 resins. The three major isolated fractions of DOM, which accounted for 57% of the bulk DOM, were characterized using a variety of analytical tools. Proton and copper binding properties were studied for each fraction. The main objective of this work was to compare the structural and chemical characteristics of the isolated fractions and test models describing DOM reactivity toward metal ions. The characterization work showed significant structural differences between the three isolated fractions of DOM. The hydrophobic acid fraction (i.e., humic substances isolated from the XAD-8 resin) gave the largest C/H, C/O, and C/N ratios and aromatic carbon content among the three isolated fractions. The transphilic acid (TPHA) fraction ("transphilic" meaning fraction of intermediate polarity isolated from the XAD-4 resin) was found to incorporate the highest proportion of polysaccharides, whereas the transphilic neutral (TPHN) fraction was almost entirely proteinaceous. The gradual increase of the charge with pH for the three DOM fractions is most likely caused by a large distribution of proton affinity constants for the carboxylic groups, as well as a second type of group more generally considered to be phenolic. In the case of the DOM fraction enriched in proteinaceous material (i.e., TPHN fraction), the results showed that the amino groups are reponsible for the charge reversal. For low copper concentrations, nitrogen-containing functional groups similar to those of amino acids are likely to be involved in complexation, in agreement with previously published data.

Metamorphic and structural evidence for significant vertical displacement along the Ross Lake fault zone, a major orogen-parallel shear zone in the Cordillera of western North America

USGS Publications Warehouse

Baldwin, J.A.; Whitney, D.L.; Hurlow, H.A.

1997-01-01

Results of an investigation of the petrology and structure of the Skymo complex and adjacent terranes constrain the amount, timing, and sense of motion on a segment of the > 600-km-long Late Cretaceous - early Tertiary Ross Lake fault zone (RLFZ), a major orogen-parallel shear zone in the Cordillera of western North America. In the study area in the North Cascades, Washington state, the RLFZ accommodated significant pre-middle Eocene vertical displacement, and it juxtaposes the Skymo complex with upper amphibolite facies (650??-690??C and 6-7 kbar) Skagit Gneiss of the North Cascades crystalline core to the SW and andalusite-bearing phyllite of the Little Jack terrane (Intermontane superterrane) to the NE. The two main lithologic units of the Skymo complex, a primitive mafic intrusion and a fault-bounded block of granulite facies metasedimentary rocks, are unique in the North Cascades. Granulite facies conditions were attained during high-temperature (> 800??C), low pressure (??? 4 kbar) contact metamorphism associated with intrusion of the mafic magma. P-T estimates and reaction textures in garnet-orthopyroxene gneiss suggest that contact metamorphism followed earlier, higher pressure regional metamorphism. There is no evidence that the Skagit Gneiss experienced high-T - low-P contact metamorphism. In the Little Jack terrane, however, texturally late cordierite ?? spinel and partial replacement of andalusite by sillimanite near the terrane's fault contact with Skymo gabbro suggest that the Little Jack terrane experienced high-T (??? 600??C) - low-P (??? 4 kbar) contact metamorphism following earlier low-grade regional metamorphism. Similarities in the protoliths of metasedimentary rocks in the Skymo and Little Jack indicate that they may be part of the same terrane. Differences in pressure estimates for the Little Jack versus Skymo for regional metamorphism that preceded contact metamorphism indicate vertical displacement of ??? 10 km (west side up) on the strand of the RLFZ that now separates the two structural blocks. High-angle faults in the study area are dextral-reverse mylonitic shear zones that experienced later brittle normal slip. Vertical motion on these shear zones before intrusion of Skymo gabbro can account for metamorphic discontinuities indicated by P-T results. The terranes have also been internally deformed by nonintersecting but coeval dextral and sinistral shear zones that formed after the terranes were brought together in the RLFZ and intruded by Eocene dikes. These results show that the RLFZ has accommodated significant vertical displacement but perhaps no more than tens of kilometers of early Tertiary lateral movement. Structural evidence for earlier, large-magnitude strike-slip displacement is not preserved.

Tracking oil and gas wastewater-derived organic matter in a hybrid biofilter membrane treatment system: A multi-analytical approach.

PubMed

Riley, Stephanie M; Ahoor, Danika C; Regnery, Julia; Cath, Tzahi Y

2018-02-01

Dissolved organic matter (DOM) present in oil and gas (O&G) produced water and fracturing flowback was characterized and quantified by multiple analytical techniques throughout a hybrid biological-physical treatment process. Quantitative and qualitative analysis of DOM by liquid chromatography - organic carbon detection (LC-OCD), liquid chromatography-high-resolution mass spectrometry (LC-HRMS), gas chromatography-mass spectrometry (GC-MS), and 3D fluorescence spectroscopy, demonstrated increasing removal of all groups of DOM throughout the treatment train, with most removal occurring during biological pretreatment and some subsequent removal achieved during membrane treatment. Parallel factor analysis (PARAFAC) further validated these results and identified five fluorescent components, including DOM described as humic acids, fulvic acids, proteins, and aromatics. Tryptophan-like compounds bound by complexation to humics/fulvics were most difficult to remove biologically, while aromatics (particularly low molecular weight neutrals) were more challenging to remove with membranes. Strong correlation among PARAFAC, LC-OCD, LC-HRMS, and GC-MS suggests that PARAFAC can be a quick, affordable, and accurate tool for evaluating the presence or removal of specific DOM groups in O&G wastewater. Copyright © 2017 Elsevier B.V. All rights reserved.

Characterization of atrazine binding to dissolved organic matter of soil under different types of land use.

PubMed

Zhu, Long-Ji; Zhao, Yue; Chen, Yan-Ni; Cui, Hong-Yang; Wei, Yu-Quan; Liu, Hai-Long; Chen, Xiao-Meng; Wei, Zi-Min

2018-01-01

Atrazine is widely used in agriculture. In this study, dissolved organic matter (DOM) from soils under four types of land use (forest (F), meadow (M), cropland (C) and wetland (W)) was used to investigate the binding characteristics of atrazine. Fluorescence excitation-emission matrix-parallel factor (EEM-PARAFAC) analysis, two-dimensional correlation spectroscopy (2D-COS) and Stern-Volmer model were combined to explore the complexation between DOM and atrazine. The EEM-PARAFAC indicated that DOM from different sources had different structures, and humic-like components had more obvious quenching effects than protein-like components. The Stern-Volmer model combined with correlation analysis showed that log K values of PARAFAC components had a significant correlation with the humification of DOM, especially for C3 component, and they were all in the same order as follows: meadow soil (5.68)>wetland soil (5.44)>cropland soil (5.35)>forest soil (5.04). The 2D-COS further confirmed that humic-like components firstly combined with atrazine followed by protein-like components. These findings suggest that DOM components can significantly influence the bioavailability, mobility and migration of atrazine in different land uses. Copyright © 2016 Elsevier Inc. All rights reserved.

Catchment-fed cyanobacterial blooms in brownified temperate lakes

NASA Astrophysics Data System (ADS)

Senar, O.; Creed, I. F.

2017-12-01

One of the most significant impacts of global atmospheric change is the alteration of hydrological regimes and the associated disruption of hydrological connectivity within watersheds. We show how changes in the frequency, magnitude, and duration of hydrological connectivity and disconnectivity is compromising the capacity of forest soils to store organic carbon, and increasing its export to both aquatic and atmospheric systems. Increases in dissolved organic matter (DOM) loads from forested landscapes to aquatic systems and the shift of the DOM pool to a more refractory mixture of organic compounds, a process known as brownification, alters the physical and chemical characteristics of lake environments. Furthermore, by characterizing the stages of brownification (from low to high concentrations of refractory DOM), we show a shift in the limiting factors for phytoplankton growth from macronutrients (nitrogen -N- and phosphorus -P) to micronutrients (iron -Fe) and light availability. This shift is driven by the low concentrations of DOM supplying N and P in early stages of brownification, to the strong Fe-binding capacity of refractory DOM in brownified lakes. As lakes undergo brownification, cyanobacteria adapted to scavenge Fe from DOM-Fe complexes have a competitive advantage leading to the formation of cyanobacterial blooms. Our findings provide evidence that brownification is a driving force leading to cyanobacterial blooms in lakes on forested landscapes, with expected cascading consequences to lake food webs.

Petrologic Constraints on the Exhumation of the Sierra Blanca Metamorphic Core Complex (AZ)

NASA Astrophysics Data System (ADS)

Koppens, K. M.; Gottardi, R.

2017-12-01

The Sierra Blanca metamorphic core complex (SBMCC), located 90 miles west of Tucson, is part of the southern belt of metamorphic core complexes that stretches across southern Arizona. The SBMCC exposes Jurassic age sedimentary rocks that have been metamorphosed by intruding Late Cretaceous peraluminous granites and pegmatites. Evidence of this magmatic episode includes polysythetic twinning in plagioclase, albite exsolution of potassium feldspar resulting in myrmekitic texture, and garnet, mica and feldspar assemblages. The magmatic fabric is overprinted by a Tertiary (Miocene?) tectonic fabric, associated with the exhumation of the Sierra Blanca metamorphic core along a low-angle detachment fault, forming the SBMCC. The NW-SE elongated dome of metamorphic rocks forms the footwall of the detachment shear zone, and is separated from the hanging wall, composed of Paleozoic and Mesozoic metasedimentary rocks, by a low-angle detachment shear zone. Foliation is defined by gneissic layering and aligned muscovite, and is generally sub-horizontal, defining the dome. The NNW-SSE mineral stretching lineation is expressed by plagioclase and K-feldspar porphyroclasts, and various shear sense indicators are all consistent with a top-to the-NNW shear sense. Lineation trends in a NNW-SSE orientation; however, plunge changes across the domiform shape of the MCC. Much of the deformation is preserved in the blastomylonitic gneiss derived from the peraluminous granite, including epidote porphyroclasts, grain boundary migration in quartz, lozenged amphiboles, mica fish, and retrograde mineral alterations. Detailed petrologic observation and microstructural analysis presented here provide thermomechanical constraints on the evolution of the SBMCC.

Tectono-metamorphic evolution of high-P/T and low-P/T metamorphic rocks in the Tia Complex, southern New England Fold Belt, eastern Australia: Insights from K-Ar chronology

NASA Astrophysics Data System (ADS)

Fukui, Shiro; Tsujimori, Tatsuki; Watanabe, Teruo; Itaya, Tetsumaru

2012-10-01

The Tia Complex in the southern New England Fold Belt is a poly-metamorphosed Late Paleozoic accretionary complex. It consists mainly of high-P/low-T type pumpellyite-actinolite facies (rare blueschist facies) schists, phyllite and serpentinite (T = 300 °C and P = 5 kbar), and low-P/high-T type amphibolite facies schist and gneiss (T = 600 °C and P < 5 kbar) associated with granodioritic plutons (Tia granodiorite). White mica and biotite K-Ar ages distinguish Carboniferous subduction zone metamorphism and Permian granitic intrusions, respectively. The systematic K-Ar age mapping along a N-S traverse of the Tia Complex exhibits a gradual change. The white mica ages become younger from the lowest-grade zone (339 Ma) to the highest-grade zone (259 Ma). In contrast, Si content of muscovite changes drastically only in the highest-grade zone. The regional changes of white mica K-Ar ages and chemical compositions of micas indicate argon depletion from precursor high-P/low-T type phengitic white mica during the thermal overprinting and recrystallization by granitoids intrusions. Our new K-Ar ages and available geological data postulate a model of the eastward rollback of a subduction zone in Early Permian. The eastward shift of a subduction zone system and subsequent magmatic activities of high-Mg andesite and adakite might explain formation of S-type granitoids (Hillgrove suite) and coeval low-P/high-T type metamorphism in the Tia Complex.

Effects of short-term warming and nitrogen addition on the quantity and quality of dissolved organic matter in a subtropical Cunninghamia lanceolata plantation.

PubMed

Yuan, Xiaochun; Si, Youtao; Lin, Weisheng; Yang, Jingqing; Wang, Zheng; Zhang, Qiufang; Qian, Wei; Chen, Yuehmin; Yang, Yusheng

2018-01-01

Increasing temperature and nitrogen (N) deposition are two large-scale changes projected to occur over the coming decades. The effects of these changes on dissolved organic matter (DOM) are largely unknown. This study aimed to assess the effects of warming and N addition on the quantity and quality of DOM from a subtropical Cunninghamia lanceolata plantation. Between 2014 and 2016, soil solutions were collected from 0-15, 15-30, and 30-60 cm depths by using a negative pressure sampling method. The quantity and quality of DOM were measured under six different treatments. The spectra showed that the DOM of the forest soil solution mainly consisted of aromatic protein-like components, microbial degradation products, and negligible amounts of humic-like substances. Warming, N addition, and warming + N addition significantly inhibited the concentration of dissolved organic carbon (DOC) in the surface (0-15 cm) soil solution. Our results suggested that warming reduced the amount of DOM originating from microbes. The decrease in protein and carboxylic acid contents was mostly attributed to the reduction of DOC following N addition. The warming + N addition treatment showed an interactive effect rather than an additive effect. Thus, short-term warming and warming + N addition decreased the quantity of DOM and facilitated the migration of nutrients to deeper soils. Further, N addition increased the complexity of the DOM structure. Hence, the loss of soil nutrients and the rational application of N need to be considered in order to prevent the accumulation of N compounds in soil.

Effects of short-term warming and nitrogen addition on the quantity and quality of dissolved organic matter in a subtropical Cunninghamia lanceolata plantation

PubMed Central

Yuan, Xiaochun; Si, Youtao; Lin, Weisheng; Yang, Jingqing; Wang, Zheng; Zhang, Qiufang; Qian, Wei; Yang, Yusheng

2018-01-01

Increasing temperature and nitrogen (N) deposition are two large-scale changes projected to occur over the coming decades. The effects of these changes on dissolved organic matter (DOM) are largely unknown. This study aimed to assess the effects of warming and N addition on the quantity and quality of DOM from a subtropical Cunninghamia lanceolata plantation. Between 2014 and 2016, soil solutions were collected from 0–15, 15–30, and 30–60 cm depths by using a negative pressure sampling method. The quantity and quality of DOM were measured under six different treatments. The spectra showed that the DOM of the forest soil solution mainly consisted of aromatic protein-like components, microbial degradation products, and negligible amounts of humic-like substances. Warming, N addition, and warming + N addition significantly inhibited the concentration of dissolved organic carbon (DOC) in the surface (0–15 cm) soil solution. Our results suggested that warming reduced the amount of DOM originating from microbes. The decrease in protein and carboxylic acid contents was mostly attributed to the reduction of DOC following N addition. The warming + N addition treatment showed an interactive effect rather than an additive effect. Thus, short-term warming and warming + N addition decreased the quantity of DOM and facilitated the migration of nutrients to deeper soils. Further, N addition increased the complexity of the DOM structure. Hence, the loss of soil nutrients and the rational application of N need to be considered in order to prevent the accumulation of N compounds in soil. PMID:29360853

Retrogressive hydration of calc-silicate xenoliths in the eastern Bushveld complex: evidence for late magmatic fluid movement

NASA Astrophysics Data System (ADS)

Wallmach, T.; Hatton, C. J.; De Waal, S. A.; Gibson, R. L.

1995-11-01

Two calc-silicate xenoliths in the Upper Zone of the Bushveld complex contain mineral assemblages which permit delineation of the metamorphic path followed after incorporation of the xenoliths into the magma. Peak metamorphism in these xenoliths occurred at T=1100-1200°C and P <1.5 kbar. Retrograde metamorphism, probably coinciding with the late magmatic stage, is characterized by the breakdown of akermanite to monticellite and wollastonite at 700°C and the growth of vesuvianite from melilite. The latter implies that water-rich fluids (X CO 2 <0.2) were present and probably circulating through the cooling magmatic pile. In contrast, calc-silicate xenoliths within the lower zones of the Bushveld complex, namely in the Marginal and Critical Zones, also contain melilite, monticellite and additional periclase with only rare development of vesuvianite. This suggests that the Upper Zone cumulate pile was much 'wetter' in the late-magmatic stage than the earlier-formed Critical and Marginal Zone cumulate piles.

Metamorphic core complexes: Expression of crustal extension by ductile-brittle shearing of the geologic column

NASA Technical Reports Server (NTRS)

Davis, G. H.

1985-01-01

Metamorphic core complexes and detachment fault terranes in the American Southwest are products of stretching of continental crust in the Tertiary. The physical and geometric properties of the structures, fault rocks, and contact relationships that developed as a consequence of the extension are especially well displayed in southeastern Arizona. The structures and fault rocks, as a system, reflect a ductile-through-brittle continuum of deformation, with individual structures and faults rocks showing remarkably coordinated strain and displacement patterns. Careful mapping and analysis of the structural system has led to the realization that strain and displacement were partitioned across a host of structures, through a spectrum of scales, in rocks of progressively changing rheology. By integrating observations made in different parts of the extensional system, especially at different inferred depth levels, it has been possible to construct a descriptive/kinematic model of the progressive deformation that achieved continental crustal extension in general, and the development of metamorphic core complexes in particular.

Anatomy of a metamorphic core complex: seismic refraction/wide-angle reflection profiling in southeastern California and western Arizona

USGS Publications Warehouse

McCarthy, J.; Larkin, S.P.; Fuis, G.S.; Simpson, R.W.; Howard, K.A.

1991-01-01

The metamorphic core complex belt in southeastern California and western Arizona is a NW-SE trending zone of unusually large Tertiary extension and uplift. Midcrustal rocks exposed in this belt raise questions about the crustal thickness, crustal structure, and the tectonic evolution of the region. Three seismic refraction/wide-angle reflection profiles were collected to address these issues. The results presented here, which focus on the Whipple and Buckskin-Rawhide mountains, yield a consistent three-dimensiional image of this part of the metamorphic core complex belt. The final model consists of a thin veneer (<2 km) of upper plate and fractured lower plate rocks (1.5-5.5 km s-1) overlying a fairly homogeneous basement (~6.0 km s-1) and a localized high-velocity (6.4 km s -1) body situated beneath the western Whipple Mountains. A prominent midcrustal reflection is identified beneath the Whipple and Buckskin Rawhide mountains between 10 and 20km depth. -from Authors

Determination of natural organic matter and iron binding capacity in fen samples

NASA Astrophysics Data System (ADS)

Kügler, Stefan; Cooper, Rebecca E.; Frieder Mohr, Jan; Wichard, Thomas; Küsel, Kirsten

2017-04-01

Natural organic matter (NOM) plays an important role in ecosystem processes such as soil carbon stabilization, nutrient availability and metal complexation. Iron-NOM-complexes, for example, are known to increase the solubility and, as a result, the bioavailability of iron in natural environments leading to several effects on the microbial community. Due to the various functions of NOM in natural environments, there is a high level of interest in the characterization of the molecular composition. The complexity of NOM presents a significant challenge in the elucidation of its composition. However, the development and utilization of high resolution mass spectrometry (HR-MS) as a tool to detect single compounds in complex samples has spearheaded the effort to elucidate the composition of NOM. Over the past years, the accuracy of ion cyclotron- or Orbitrap mass spectrometers has increased dramatically resulting in the possibility to obtain a mass differentiation of the large number of compounds in NOM. Together these tools provide significant and powerful insight into the molecular composition of NOM. In the current study, we aim to understand abiotic and biotic interactions between NOM and metals, such as iron, found in the Schlöppnerbrunnen fen (Fichtelgebirge, Germany) and how these interactions impact the microbial consortia. We characterized the dissolved organic matter (DOM) as well as basic chemical parameters in the iron-rich (up to 20 mg (g wt peat)-1), slightly acidic (pH 4.8) fen to gain more information about DOM-metal interactions. This minerotrophic peatland connected to the groundwater has received Fe(II) released from the surrounding soils in the Lehstenbach catchment. Absorption spectroscopy (AAS), differential pulse polarography (DPP) and high resolution electrospray ionization mass spectrometry (HR-ESI-Orbitrap-MS) was applied to characterize the molecular composition of DOM in the peat water extract (PWE). We identified typical patterns for DOM illustrated by van Krevelen plots, which indicate the presence of different substance classes including condensed aromatics, lignins and tannins known to complex iron. Our results indicate a variety of potential Fe-DOM-complexes present in the PWE samples when iron is incorporated into the elemental composition search. Using DPP we determine the complexation capacity of iron in the natural matrix of the fen along with the identification of ligands in order to estimate the iron bioavailability for bacteria. As the microbial redox system of the fen is impacted by other metals in the environment, we perform comprehensive analysis of the entirety of metal ions and concentrations in the water samples. Dialysis chambers are currently installed in the iron-rich fen from which pore water samples will be collected at 1 cm increments between 0-20 cm depth to determine the depth profiles of Fe(II)- and Fe(III)-concentration and evaluate the influence of the depth profiles on the interplay between microorganism comprising the natural microbial redox system of the fen. We have shown that metal-DOM-pH interactions affect the bioavailable metal concentration in fen water systems. This information will pave the way for a better understanding of the bacterial recruitment of trace elements and microbial redox reactions.

Early post-collisional Brasiliano magmatism in Botuverá region, Santa Catarina, southern Brazil: Evidence from petrology, geochemistry, isotope geology and geochronology of the diabase and lamprophyre dikes

NASA Astrophysics Data System (ADS)

Sacks de Campos, Roberto; Philipp, Ruy Paulo; Massonne, Hans-Joachim; Chemale, Farid

2012-08-01

The post-collisional magmatism related to Brasiliano orogeny represented the final stage of the Dom Feliciano Belt in Rio Grande do Sul and Santa Catarina states, southern Brazil, presenting high-K calc-alkaline to shoshonitic and alkaline chemical signatures. Magmatic episodes related to this early period were found in Botuverá region, Santa Catarina state, represented by diabase and lamprophyre (spessartite-type) dikes intrusive in metavolcano-sedimentary rocks of the Brusque Metamorphic Complex (CMB). These dikes have massive structure and igneous textures ranging from very fine equigranular to porphyritic, and the latter is characterized by the presence of phenocrysts of plagioclase and hornblende. The dikes have northeast direction and sharp contacts with the metamorphic rocks, indicating that its position was after the main orogenic regional metamorphism that affected the CMB, interpreted as of collisional nature. The diabase has a basic composition, whereas spessartite lamprophyres are intermediate, with geochemical affinities to the tholeiitic series, with a significant enrichment in light rare-earth elements (LREE) and large ion lithophile elements (LILE) such as Cs, Rb, Ba, K and Sr, and negative anomalies for high-field-strength elements (HFS) such as Nb, Ta, U and T. The concentration of standard trace elements and the Th/Yb and Ta/Yb ratios indicate that these magmas were derived from an enriched mantle source and were strongly contaminated by crust. Except for higher values of K, these features are similar to those found in basaltic volcanic rocks associated with the post-collisional period in south Brazil. The widely dispersed values of ɛND (618), ranging between -13.74 and +5.52, highlights the heterogeneity of the source and reinforces the importance of a crustal component in the generation of these rocks. The extremely low value of ɛNd (618), of -21.67 obtained for spessartite lamprophyres supports the importance of the involvement of crust in the genesis of this rock. Using the U-Pb and LA-ICP-MS method, a concordant age of 618 ± 8.7 Ma was obtained in zircon crystals of a diabase dike of the region of Barra do Areia, in Botuverá, SC. The existence of inherited zircon grains older than 1800 Ma in this sample supports the involvement of Paleoproterozoic continental crust. The data analysis characterizes the first magmatic age related to the post-collisional period of the Brasiliano orogeny in this region of the Santa Catarina Shield.

Metamorphic InAsSb-based Barrier Photodetectors for the Long Wave Infrared Region

DTIC Science & Technology

2013-08-02

The character of the I–V for structures with AlInSb layer grown undoped reflects the complex nature of the potential profile in the valence band ...Al0.75In0.25Sb-based barrier photodetectors were grown metamorphically on compositionally graded Ga1?xInxSb buffer layers and GaSb substrates by...ABSTRACT InAs0.6Sb0.4/Al0.75In0.25Sb-based barrier photodetectors were grown metamorphically on compositionally graded Ga1?xInxSb buffer layers and GaSb

Factors controlling the abiotic photo-degradation of monomethylmercury in surface waters

NASA Astrophysics Data System (ADS)

Black, Frank J.; Poulin, Brett A.; Flegal, A. Russell

2012-05-01

Photo-decomposition is among the most important mechanisms responsible for degrading monomethylmercury (MMHg) in aquatic systems, but this process is not fully understood. We investigated the relative importance of different factors in controlling the rate of MMHg photo-decomposition in surface waters in experiments using DOM isolated from natural waters. We found no evidence of net abiotic production of MMHg in any dark or light exposed treatments. The average (mean ± s.d.) MMHg photo-decomposition rate constant for all light exposed samples using DOM concentrated from three coastal wetlands was 0.0099 ± 0.0020 E-1m2 (range of 0.006-0.015 E-1m2) when expressed in photon flux from 330-700 nm. This was roughly 3-fold higher than the average MMHg photo-decomposition rate constant in coastal seawater of 0.0032 ± 0.0010 E-1m2. MMHg photo-degradation was highly wavelength dependent. The ratio of MMHg photo-decomposition rate constants, with respect to photon flux, was 400:37:1 for UVB:UVA:PAR. However, when integrated across the entire water column over which MMHg photo-demethylation occurs, PAR was responsible for photo-degrading more MMHg than UVB and UVA combined in the three wetland sites because of the more rapid attenuation of UV light with depth. MMHg half-lives in the wetlands were calculated for the upper 250 cm where photo-degradation occurred, and ranged from 7.6 to 20 days under typical summer sunlight conditions at 37°N. Rates of MMHg photo-decomposition decreased with increasing salinity, and were 27% higher at a salinity of 5 than those at a salinity of 25. This difference could not be accounted for by changes in the complexation of MMHg by DOM and chloride. Differences in MMHg photo-degradation rate constants of up to 18% were measured between treatments using DOM concentrated from three different wetlands. Surprisingly, increasing DOM concentration from 1.5 to 11.3 mg OC L-1 had only a small (6%) effect on MMHg photo-decomposition, which was much smaller than the 34% decrease predicted due to the attenuation of light at the higher DOM levels. This suggests that DOM plays an important role in MMHg photo-decomposition apart from mediating light levels and MMHg complexation. Experiments employing various scavengers implied that singlet oxygen and hydroxyl radicals were not involved in the photo-degradation of MMHg in the natural waters used. Varying concentrations of Fe, Cu, and Mn had only small (⩽11%) effects on rates of MMHg photo-decomposition, and relatively high rates were measured in high purity water with no trace metals or DOM. These results demonstrate that MMHg photo-decomposition can occur via pathways not involving Fe, the photo-Fenton reaction, nitrate photolysis, or thiol complexation. Taken with previous studies, multiple reaction pathways appear to exist, and their importance varies as a function of water chemistry and light wavelength.

The Anarak, Jandaq and Posht-e-Badam metamorphic complexes in central Iran: New geological data, relationships and tectonic implications

NASA Astrophysics Data System (ADS)

Bagheri, Sasan; Stampfli, Gérard M.

2008-04-01

The Anarak, Jandaq and Posht-e-Badam metamorphic complexes occupy the NW part of the Central-East Iranian Microcontinent and are juxtaposed with the Great Kavir block and Sanandaj-Sirjan zone. Our recent findings redefine the origin of these complexes, so far attributed to the Precambrian-Early Paleozoic orogenic episodes, and now directly related to the tectonic evolution of the Paleo-Tethys Ocean. This tectonic evolution was initiated by Late Ordovician-Early Devonian rifting events and terminated in the Triassic by the Eocimmerian collision event due to the docking of the Cimmerian blocks with the Asiatic Turan block. The "Variscan accretionary complex" is a new name we proposed for the most widely distributed metamorphic rocks connected to the Anarak and Jandaq complexes. This accretionary complex exposed from SW of Jandaq to the Anarak and Kabudan areas is a thick and fine grain siliciclastic sequence accompanied by marginal-sea ophiolitic remnants, including gabbro-basalts with a supra-subduction-geochemical signature. New 40Ar/ 39Ar ages are obtained as 333-320 Ma for the metamorphism of this sequence under greenschist to amphibolite facies. Moreover, the limy intercalations in the volcano-sedimentary part of this complex in Godar-e-Siah yielded Upper Devonian-Tournaisian conodonts. The northeastern part of this complex in the Jandaq area was intruded by 215 ± 15 Ma arc to collisional granite and pegmatites dated by ID-TIMS and its metamorphic rocks are characterized by some 40Ar/ 39Ar radiometric ages of 163-156 Ma. The "Variscan" accretionary complex was northwardly accreted to the Airekan granitic terrane dated at 549 ± 15 Ma. Later, from the Late Carboniferous to Triassic, huge amounts of oceanic material were accreted to its southern side and penetrated by several seamounts such as the Anarak and Kabudan. This new period of accretion is supported by the 280-230 Ma 40Ar/ 39Ar ages for the Anarak mild high-pressure metamorphic rocks and a 262 Ma U-Pb age for the trondhjemite-rhyolite association of that area. The Triassic Bayazeh flysch filled the foreland basin during the final closure of the Paleo-Tethys Ocean and was partly deposited and/or thrusted onto the Cimmerian Yazd block. The Paleo-Tethys magmatic arc products have been well-preserved in the Late Devonian-Carboniferous Godar-e-Siah intra-arc deposits and the Triassic Nakhlak fore-arc succession. On the passive margin of the Cimmerian block, in the Yazd region, the nearly continuous Upper Paleozoic platform-type deposition was totally interrupted during the Middle to Late Triassic. Local erosion, down to Lower Paleozoic levels, may be related to flexural bulge erosion. The platform was finally unconformably covered by Liassic continental molassic deposits of the Shemshak. One of the extensional periods related to Neo-Tethyan back-arc rifting in Late Cretaceous time finally separated parts of the Eocimmerian collisional domain from the Eurasian Turan domain. The opening and closing of this new ocean, characterized by the Nain and Sabzevar ophiolitic mélanges, finally transported the Anarak-Jandaq composite terrane to Central Iran, accompanied by large scale rotation of the Central-East Iranian Microcontinent (CEIM). Due to many similarities between the Posht-e-Badam metamorphic complex and the Anarak-Jandaq composite terrane, the former could be part of the latter, if it was transported further south during Tertiary time.

Petrologic and zircon U-Pb geochronological characteristics of the pelitic granulites from the Badu Complex of the Cathaysia Block, South China

NASA Astrophysics Data System (ADS)

Zhao, Lei; Zhou, Xiwen; Zhai, Mingguo; Liu, Bo; Cui, Xiahong

2018-06-01

The recognition of the Indosinian Orogeny in the South China block has been controversial and difficult because of strong weathering and thick cover. High temperature (HT) and high pressure (HP) metamorphic rocks related to this orogeny were considered to be absent from this orogenic belt until the recent discovery of eclogite and granulite facies meta-igneous rocks, occurring as lenses within the meta-sedimentary rocks of the Badu Complex. However, metamorphic state of these meta-sedimentary rocks is still not clear. Besides, there have been no geochronological data of HT pelitic granulites previously reported from the Badu Complex. This paper presents petrographic characteristics and zircon geochronological results on the newly discovered kyanite garnet gneiss, pyroxene garnet gneiss and the HT pelitic granulites (sillimanite garnet gneiss). Mineral assemblages are garnet + sillimanite + ternary feldspar + plagioclase + quartz + biotite for the HT pelitic granulite, kyanite + ternary feldspar + garnet + sillimanite + plagioclase + quartz + biotite for the kyanite garnet gneiss, and garnet + biotite + pyroxene + plagioclase + ternary feldspar + quartz for the pyroxene garnet gneiss, respectively. Decompressional coronas around garnet grains can be observed in all these pelitic rocks. Typical granulite facies mineral assemblages and reaction textures suggest that these rocks experienced HP granulite facies metamorphism and overprinted decompression along a clockwise P-T loop. Results from integrated U-Pb dating and REE analysis indicate the growth of metamorphic zircons from depleted heavy REE sources (100-50 chondrite) compared with detrital zircons derived from granitic sources (typically > 1000 chondrite). Metamorphic zircons in HP granulite exhibit no or subdued negative Eu anomalies, which perhaps indicate zircon overgrowth under eclogite facies conditions. The zircon overgrowth ages range from 250 to 235 Ma, suggesting that HP granulite (eclogite) to granulite facies metamorphism of these supracrustal rocks occurred in the Early-Middle Triassic. Based on the presence of HP granulite facies pelitic rocks, it is inferred that significant underthrusting was involved during the Indosinian Orogeny which introduced these supracrustal rocks to lower crustal levels.

A tectonic linkage between the Rodelide orogen (Sierra Leone) and the St. Lucie metamorphic complex in the Florida subsurface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dallmeyer, R.D.

1989-03-01

Hornblende concentrates prepared from cuttings from two deep test wells penetrating the complex display internally concordant {sup 40}Ar/{sup 39}Ar incremental-release spectra defining plateau ages of 510.8 {plus minus} 1.1 Ma and 513.1 {plus minus} 1.8 Ma, which are interpreted to date post-metamorphic cooling through temperatures required for intracrystalline argon retention. The Kasila Group constitutes the western segment of the Rokelide orogen in Sierra Leone. Four hornblende concentrations prepared for amphibolite within the Kasila Group yield {sup 40}Ar/{sup 39}Ar plateau ages of 505.0 {plus minus} 5.2, 508.2 {plus minus} 2.1, 510.5 {plus minus} 2.6, and 546.1 {plus minus} 6.8 Ma. Theymore » are interpreted to date post-metamorphic cooling through appropriate argon closure temperature following a ca. 550-560 Ma, Pan-African II phase of tectonothermal activity. A biotite concentrate from paragneiss within the Kasila Group displays an internally concordant {sup 40}/Ar{sup 39}Ar release spectrum defining a plateau age of 524.7 {plus minus} 1.3 Ma, which likely reflects slight contamination with extraneous (excess) argon. Muscovite from the Marampa Group yields a {sup 40}Ar/{sup 39}Ar plateau age of 561.1 {plus minus} 2.3 Ma, which is interpreted to date cooling through appropriate argon closure temperatures. Although these temperatures are generally considered to be lower than those for hornblenede, the muscovite records an older cooling age, suggesting that the Marampa Group experienced slightly earlier post-metamorphic uplift and cooling relative to the Kasila Group. Lithologic comparison combined with similarities in post-metamorphic thermal evolution suggest that the St. Lucie Metamorphic Complex originated within the Rockelide orogen. This and other lithotectonic elements of the Suwannee terrane appear to represent a fragment of Gondwana which accreted to Laurentia during late Paleozoic amalgamation of Pangea.« less

Gamma spectrometry application of the Kola Peninsula (in Russian)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Golovin, I.V.; Kolesnik, N.N.; Antipov, V.S.

1973-03-01

The methods and results are reported of a spectrometric study, carried out with the SP-3 instrument in Pre-Cambrian fornnations in the northwest ranges of Kola Peninsula for clarification of the radiochemical characteristics of the rocks of the region and of the distribution characteristics of radioactive elements in Cu-Ni mineralizations. It was established that the content of radioactive elements in the rocks varies within a wide interval and corresponds basically to the Vinogradov content. The radioactive element content in typical metamorphic and magmatic complexes and sulfide ores was determined. The spectrometric method can be used for the solution of various geologicalmore » problems. It is particularly useful for studying the separation of strata, the genesis of magmatic and metamorphic complexes, and the metamorphic and geochemical zonality and granitization processes. (tr-auth)« less

High-P metamorphic rocks from the Himalaya and their tectonic implication ? a review

NASA Astrophysics Data System (ADS)

Jan, M. Qasim

The suture zones bordering the Indian subcontinent on the E, N and W are characterized in several places by the occurrence of ophiolitic complexes and tectonic melanges. High-P metamorphic rocks have recently been discovered in the melanges in Burma, Naga Hills, southern Tibet, eastern and western Ladakh, Kohistan (Jijal, Allai, Shangla) and Khost (Afghanistan). The development of these rocks has an important bearing on the plate tectonics of the Himalaya. The High-P metamorphic rocks belong to prehnite-pumpellyite, blueschist and high-P greenschist facies but extensive garnet-granulites have developed at 35 km depth in Jijal. In the Indus-Zangbo suture zone (IZS) the high-P metamorphism is complemented to the N by low- or medium-P metamorphism and calc-alkaline magmatism in Tibet, Ladakh as well as Kohistan. High-P metamorphism in Jijal has been dated at 104 Ma, in Shangla at 70-100 Ma and in western Ladakh during mid-Cretaceous. Elsewhere, the timing of the high-P metamorphism is not known but a Cretaceous age is inferred. Since collision along the IZS occurred during Eocene, the high-P metamorphism is therefore related to the northwards subduction of the neo-Tethyan lithosphere under Tibet or late Mesozoic magmatic arcs. The timing of high-P metamorphism coincides with the breakup of India from Gondwanaland and its rapid northwards movement, whereas the tectonic melanges may principally have formed during Eocene collision and obduction.

The post collisional metamorphic evolution from Ultra High Temperature to Amphibolite facies metamorphism in the Odesan area during the Triassic collision between the North and South China cratons.

NASA Astrophysics Data System (ADS)

Lee, Byung Choon; Oh, Chang Whan; Kim, Tae Sung; Yi, Kee Wook

2015-04-01

The Odaesan Gneiss Complex (OGC) is the eastern end of the Hongseong-Odesan collision belt in Korean Peninsula which is the extension of the Dabie-Sulu collision belt between the North and South China blocks. The OGC mainly consists of banded and migmatitic gneiss with porphyritic granitoid and amphibolite. The banded gneiss can be subdivided into garnet-biotite and garnet-orthopyroxene banded gneisses. The highest metamorphic P/T conditions of the migmatitic and garnet-biotite banded gneiss were 760-820°C/6.3-7.2kbar and 810-840°C/7.2-7.8kbar respectively. On the other hand, the garnet-orthopyroxene banded gneiss records 940-950°C/10.5-10.7kbar that is corresponded to UHT metamorphic condition. These data indicate that the peak UHT metamorphic condition of the study area was preserved only within the garnet-orthopyroxene banded gneiss because its lower water content than other gneisses and UHT metamorphic mineral assemblage was completely replaced by the granulite facies metamorphism in other gneisses due to their higher water content than the garnet-orthopyroxene banded gneiss. Finally all gneisses experienced amphibolite facies retrograde metamorphism which is observed locally within rocks, such as garnet rim and surrounding area. The peak UHT metamorphism is estimated to occur at ca. 250-230 Ma using SHRIMP zircon U-Pb age dating and was caused by the heat supplied from asthenospheric mantle through the opening formed by slab break-off during early post collision stage. The calculated metamorphic conditions represent that geothermal gradient of the study area during the post collision stage was 86°C/kbar indicating the regional low-P/T metamorphic event. Besides the Triassic metamorphic age, two Paleoproterozoic metamorphic ages of ca. 1930 and 1886 Ma are also recognized by the SHRIMP age dating from the banded gneisses and Paleoproterozoic emplacement age of ca. 1847 Ma is identified from the porphyritic granitoid which formed in the within plate tectonic setting. These ages are well matched with 1880Ma-1885Ma regional post-collision igneous and metamorphic activities in other areas of the GM indicating that the OGC had undergone Paleoproterozoic metamorphic and igneous activities before the Triassic metamorphism. However it is difficult to confirm the Paleoproterozoic activities due to the strong Triassic metamorphism.

Effect of dissolved organic matter on pre-equilibrium passive sampling: A predictive QSAR modeling study.

PubMed

Lin, Wei; Jiang, Ruifen; Shen, Yong; Xiong, Yaxin; Hu, Sizi; Xu, Jianqiao; Ouyang, Gangfeng

2018-04-13

Pre-equilibrium passive sampling is a simple and promising technique for studying sampling kinetics, which is crucial to determine the distribution, transfer and fate of hydrophobic organic compounds (HOCs) in environmental water and organisms. Environmental water samples contain complex matrices that complicate the traditional calibration process for obtaining the accurate rate constants. This study proposed a QSAR model to predict the sampling rate constants of HOCs (polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and pesticides) in aqueous systems containing complex matrices. A homemade flow-through system was established to simulate an actual aqueous environment containing dissolved organic matter (DOM) i.e. humic acid (HA) and (2-Hydroxypropyl)-β-cyclodextrin (β-HPCD)), and to obtain the experimental rate constants. Then, a quantitative structure-activity relationship (QSAR) model using Genetic Algorithm-Multiple Linear Regression (GA-MLR) was found to correlate the experimental rate constants to the system state including physicochemical parameters of the HOCs and DOM which were calculated and selected as descriptors by Density Functional Theory (DFT) and Chem 3D. The experimental results showed that the rate constants significantly increased as the concentration of DOM increased, and the enhancement factors of 70-fold and 34-fold were observed for the HOCs in HA and β-HPCD, respectively. The established QSAR model was validated as credible (R Adj. 2 =0.862) and predictable (Q 2 =0.835) in estimating the rate constants of HOCs for complex aqueous sampling, and a probable mechanism was developed by comparison to the reported theoretical study. The present study established a QSAR model of passive sampling rate constants and calibrated the effect of DOM on the sampling kinetics. Copyright © 2018 Elsevier B.V. All rights reserved.

Metamorphism in the Potomac composite terrane, Virginia-Maryland

DOE Office of Scientific and Technical Information (OSTI.GOV)

Drake, A.A. Jr.

1985-01-01

Metamorphic rocks in the Potomac Valley occur in three allochthon-precursory melange pairs unconformably overlain by the Popes Head Formation which is at greenschist facies of metamorphism. The highest motif, the Piney Branch Complex and Yorkshire Formation are also in the greenschist facies. The middle motif, consists of the Peters Creek Schist and the Sykesville Formation. Quartzose schists and metagraywacke of the Peters Creek contain serpentinite debris and have had a complex metamorphic history: Barrovian prograde to amphibolite facies (with sillimanite), a localized retrograde event producing chlorite phyllonite, and a later greenschist prograde event. The Sykeville is at biotite +/- garnetmore » grade and contains deformed olistoliths of Peters Creek, including phyllonite, at various grades. The lower motif consists of the Annandale Group (pelitic schists and metasandstone) and Indian Run Formation. The Annandale has experienced two greenschist metamorphisms. The Indian Run is at biotite +/- garnet grade and contains previously metamorphosed and deformed olistoliths of Annandale. The allochthons have had different histories, but after stacking they were metamorphosed with their melanges and the Popes Head to biotite grade. The Popes Head has experienced three phases of folding, the earliest synkinematic with Occoquan emplacement. These fold phases are superposed on earlier structures in the older rocks and are probably of Late Cambrian age (Penobscotian). Earlier deformation is probably of Late Proterozoic age (Cadomian). Neither of these deformations is recognized in North American rocks.« less

Reconnaissance geologic map of the Kuskokwim Bay region, southwest Alaska

USGS Publications Warehouse

Wilson, Frederic H.; Hults, Chad P.; Mohadjer, Solmaz; Coonrad, Warren L.

2013-01-01

The rocks of the map area range from Proterozoic age metamorphic rocks of the Kanektok metamorphic complex (Kilbuck terrane) to Quaternary age mafic volcanic rocks of Nunivak Island. The map area encompasses much of the type area of the Togiak-Tikchik Complex. The geologic maps used to construct this compilation were, for the most part, reconnaissance studies done in the time period from the 1950s to 1990s. Pioneering work in the map area by J.M. Hoare and W.L. Coonrad forms the basis for much of this map, either directly or as the stepping off point for later studies compiled here. Physiographically, the map area ranges from glaciated mountains, as much as 1,500 m high, in the Ahklun Mountains to the coastal lowlands of northern Bristol Bay and the Kuskokwim River delta. The mountains and the finger lakes (drowned fiords) on the east have been strongly affected by Pleistocene and Holocene glaciation. Within the map area are a number of major faults. The Togiak-Tikchik Fault and its extension to the northeast, the Holitna Fault, are considered extensions of the Denali fault system of central Alaska. Other sub-parallel faults include the Golden Gate, Sawpit, Goodnews, and East Kulukak Faults. Northwest-trending strike-slip faults crosscut and offset northeast-trending fault systems. Rocks of the area are assigned to a number of distinctive lithologic packages. Most distinctive among these packages are the high-grade metamorphic rocks of the Kanektok metamorphic complex or Kilbuck terrane, composed of a high-grade metamorphic orthogneiss core surrounded by greenschist and amphibolite facies schist, gneiss, and rare marble and quartzite. These rocks have yielded radiometric ages strongly suggestive of a 2.05 Ga emplacement age. Poorly known Paleozoic rocks, including Ordovician to Devonian and Permian limestone, are found east of the Kanektok metamorphic complex. A Triassic(?) ophiolite complex is on the southeast side of Kuskokwim Bay; otherwise only minor Triassic rock units are known. The most widespread rocks of the area are Jurassic and Early Cretaceous(?) volcanic and volcaniclastic rocks. The Kuskokwim Group flysch is restricted largely to the northeast part of the map area. It consists primarily of shelf and minor nearshore facies rocks. Primarily exposed in the lowlands west of the Ahklun Mountains, extensive latest Tertiary and Quaternary alkalic basalt flows and lesser pyroclastic rocks form much of the bedrock of the remaining area. On Saint Matthew Island, Cretaceous volcanic and pyroclastic rocks occur that are not found elsewhere within the map area. The Kuskokwim Group and older rocks, including on Saint Matthew Island, but not the Kanektok metamorphic complex, are intruded by widely dispersed Late Cretaceous and (or) Early Tertiary granitic rocks. Much of the lowland area is mantled by unconsolidated deposits that include glacial, alluvial and fluvial, marine, estuarine, and eolian deposits. These formed during several episodes of Quaternary glaciation.

A critical review of three methods used for the measurement of mercury (Hg2+)-dissolved organic matter stability constants

USGS Publications Warehouse

Gasper, J.D.; Aiken, G.R.; Ryan, J.N.

2007-01-01

Three experimental techniques - ion exchange, liquid-liquid extraction with competitive ligand exchange, and solid-phase extraction with competitive ligand exchange (CLE-SPE) - were evaluated as methods for determining conditional stability constants (K) for the binding of mercury (Hg2+) to dissolved organic matter (DOM). To determine the utility of a given method to measure stability constants at environmentally relevant experimental conditions, experimental results should meet three criteria: (1) the data must be experimentally valid, in that they were acquired under conditions that meet all the requirements of the experimental method, (2) the Hg:DOM ratio should be determined and it should fall within levels that are consistent with environmental conditions, and (3) the stability constants must fall within the detection window of the method. The ion exchange method was found to be limited by its detection window, which constrains the method to stability constants with log K values less than about 14. The liquid-liquid extraction method was found to be complicated by the ability of Hg-DOM complexes to partition into the organic phase. The CLE-SPE method was found to be the most suitable of these methods for the measurement of Hg-DOM stability constants. Stability constants for DOM isolates measured using the CLE-SPE method at environmentally relevant Hg:DOM ratios were log K = 25-30 (M-1). These values are consistent with the strong Hg2+ binding expected for reduced S-containing binding sites. ?? 2007 Elsevier Ltd. All rights reserved.

Deciphering associations between dissolved organic molecules and bacterial communities in a pelagic marine system

PubMed Central

Osterholz, Helena; Singer, Gabriel; Wemheuer, Bernd; Daniel, Rolf; Simon, Meinhard; Niggemann, Jutta; Dittmar, Thorsten

2016-01-01

Dissolved organic matter (DOM) is the main substrate and energy source for heterotrophic bacterioplankton. To understand the interactions between DOM and the bacterial community (BC), it is important to identify the key factors on both sides in detail, chemically distinct moieties in DOM and the various bacterial taxa. Next-generation sequencing facilitates the classification of millions of reads of environmental DNA and RNA amplicons and ultrahigh-resolution mass spectrometry yields up to 10 000 DOM molecular formulae in a marine water sample. Linking this detailed biological and chemical information is a crucial first step toward a mechanistic understanding of the role of microorganisms in the marine carbon cycle. In this study, we interpreted the complex microbiological and molecular information via a novel combination of multivariate statistics. We were able to reveal distinct relationships between the key factors of organic matter cycling along a latitudinal transect across the North Sea. Total BC and DOM composition were mainly driven by mixing of distinct water masses and presumably retain their respective terrigenous imprint on similar timescales on their way through the North Sea. The active microbial community, however, was rather influenced by local events and correlated with specific DOM molecular formulae indicative of compounds that are easily degradable. These trends were most pronounced on the highest resolved level, that is, operationally defined ‘species', reflecting the functional diversity of microorganisms at high taxonomic resolution. PMID:26800236

North American import? Charting the origins of an enigmatic Trypanosoma cruzi domestic genotype.

PubMed

Zumaya-Estrada, Federico A; Messenger, Louisa A; Lopez-Ordonez, Teresa; Lewis, Michael D; Flores-Lopez, Carlos A; Martínez-Ibarra, Alejandro J; Pennington, Pamela M; Cordon-Rosales, Celia; Carrasco, Hernan V; Segovia, Maikel; Miles, Michael A; Llewellyn, Martin S

2012-10-10

Trypanosoma cruzi, the agent of Chagas disease, is currently recognized as a complex of six lineages or Discrete Typing Units (DTU): TcI-TcVI. Recent studies have identified a divergent group within TcI - TcI(DOM). TcI(DOM). is associated with a significant proportion of human TcI infections in South America, largely absent from local wild mammals and vectors, yet closely related to sylvatic strains in North/Central America. Our aim was to examine hypotheses describing the origin of the TcI(DOM) genotype. We propose two possible scenarios: an emergence of TcI(DOM) in northern South America as a sister group of North American strain progenitors and dispersal among domestic transmission cycles, or an origin in North America, prior to dispersal back into South American domestic cycles. To provide further insight we undertook high resolution nuclear and mitochondrial genotyping of multiple Central American strains (from areas of México and Guatemala) and included them in an analysis with other published data. Mitochondrial sequence and nuclear microsatellite data revealed a cline in genetic diversity across isolates grouped into three populations: South America, North/Central America and TcI(DOM). As such, greatest diversity was observed in South America (A(r) = 4.851, π = 0.00712) and lowest in TcI(DOM) (Ar = 1.813, π = 0.00071). Nuclear genetic clustering (genetic distance based) analyses suggest that TcI(DOM) is nested within the North/Central American clade. Declining genetic diversity across the populations, and corresponding hierarchical clustering suggest that emergence of this important human genotype most likely occurred in North/Central America before moving southwards. These data are consistent with early patterns of human dispersal into South America.

Seasonal Variation in Dissolved Organic Matter Composition and Photoreactivity within a Small Sub-arctic Stream.

NASA Astrophysics Data System (ADS)

Guerard, J.; Osborne, R.

2015-12-01

Dissolved organic matter (DOM) is a complex heterogeneous mixture, ubiquitous to all natural surface waters, uniquely composed of source inputs specific to spatial, temporal, and ecological circumstances. In arctic and sub-arctic regions, elucidating DOM composition and reactivity is complicated by seasonal variations. These include changes in productivity and source inputs to the water column, as well as winter overflow events that may contribute allochthonous organic material. DOM from a small boreal stream in a watershed of discontinuous permafrost in the Goldstream Valley of interior Alaska was isolated by solid-phase extraction (PPL) at multiple points during the year - late spring, late summer, and in the winter during an active overflow event. Compositional characteristics of each of the isolates were characterized by SPR-W5-WATERGATE 1H NMR spectroscopy, specific UV-Vis absorbance, and excitation emission matrix (EEM) fluorescence spectroscopy and compared against end-member reference DOM isolates. Kinetics of photobleaching experiments reveal the influence of compositional differences among the isolated DOMs on their chemical reactivity, and offer insight into potential differences in their source materials and ecological function throughout the year. Photobleaching studies were conducted using a variety of reactive species quenchers or sensitizers in order to assess susceptibility of oxidative transformation mechanisms on the different DOM isolates, which were then analyzed by 1H NMR, UV-Vis degradation kinetics, and parallel factor analysis (PARAFAC) of fluorescence EEMs. Better understanding of the seasonal variations of boreal DOM character and function on a molecular level is critical to assessing alterations in its ecological role and cycling in the face of current and future ecosystem perturbations in arctic and sub-arctic regions.

Regional and contact metamorphism within the Moy Intrusive Complex, Grampian Highlands, Scotland

NASA Astrophysics Data System (ADS)

Zaleski, E.

1985-04-01

In central Scotland, the Moy Intrusive Complex consists of (1) the Main Phase — syntectonic peraluminous granodiorite to granite emplaced at c. 455 Ma, intruded by (2) the Finglack Alaskite — post-tectonic leucocratic granite emplaced at 407+/-5 Ma. The Main Phase was emplaced into country rocks at amphibolite facies temperatures. Rb-Sr dates and a compositional spectrum of decreasing celadonite content in Main Phase muscovite suggest the persistence of c. 550° C temperatures for c. 30 Ma but with a declining pressure regime, i.e. isothermal uplift. The Finglack Alaskite was intruded at high structural level, leading to the development of a contact metamorphic aureole in the Main Phase. The thermal effects of contact metamorphism include intergrowths of andalusite, biotite and feldspar in pseudomorphs after muscovite. This is associated with recrystallized granoblastic quartz. Muscovite breakdown and reaction with adjacent biotite, quartz and feldspar, i.e. a function of local mineral assemblage rather than bulk rock composition, is postulated to explain the occurrence of metamorphic andalusite in a granitoid rock. The Main Phase pluton of the Moy Intrusive Complex lies within a NNE trending belt of c. 450 Ma Caledonian tectonic and magmatic activity paralleling the Moine Thrust, and extending from northern Scotland to the Highland Boundary Fault. Syntectonic ‘S-type’ magmatism with upper crustal source areas implies crustal thickening and suggests an intracratonic orogeny.

U-Pb dating and isotopic signature of the alkaline ring complexes of Bou Naga (Mauritania): its bearing on late proterozoic plate tectonics around the West African craton

NASA Astrophysics Data System (ADS)

Blanc, A.; Bernard-Griffiths, J.; Caby, R.; Caruba, C.; Caruba, R.; Dars, R.; Fourcade, S.; Peucat, J. J.

1992-04-01

In the West African fold belt of Mauritania, high-grade metamorphic series, similar to those of Amsaga (Reguibat shield-West African Craton), are exposed in a window. At Bou Naga-Mauritania (19° N, 13° 15' W) in the South of this window, an alkaline ring complex has intruded the metamorphic country rocks. This complex consists of two geological formations: the Eastern formation is mainly composed of red rhyolite sills, whereas the Western formation is made up of several kinds of alkaline rocks both saturated and under-saturated which cross cut the earlier saturated units. Three U-Pb zircon age measurements have been made on the alkaline complex, and one on an orthogneiss from the metamorphic country rocks. The syenite and the alkaline granite of the Western block are 676 ± 8 and 687 ± 5 Ma old. The orthogneiss is Archaean with an age of 2709 ± 136 Ma, but the lower intercept of discordia on concordia, shows an age of 756 ± 25 Ma linked with the genesis of the alkaline complex. A major crustal contribution is recorded by Nd and O isotopes in the SiO 2-saturated rocks. These results provide evidence for the correlation of the metamorphic country rocks with the Reguibat Archaean basement and for an early Pan-African continental rifting phase in this area before the tectonometamorphic events in the Mauritanide belt. Furthermore, with regards with previous geodynamic works of the West African Craton, our results leads us to suggest a significant diachronism between late Proterozoic crustal evolution to the West and to the East of the West African Craton. This is a further evidence for modern-type plate tectonics at this time.

Single quantum dot emission at telecom wavelengths from metamorphic InAs/InGaAs nanostructures grown on GaAs substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Seravalli, L.; Trevisi, G.; Frigeri, P.

We report on the growth by molecular beam epitaxy and the study by atomic force microscopy and photoluminescence of low density metamorphic InAs/InGaAs quantum dots. subcritical InAs coverages allow to obtain 10{sup 8} cm{sup -2} dot density and metamorphic In{sub x}Ga{sub 1-x}As (x=0.15,0.30) confining layers result in emission wavelengths at 1.3 {mu}m. We discuss optimal growth parameters and demonstrate single quantum dot emission up to 1350 nm at low temperatures, by distinguishing the main exciton complexes in these nanostructures. Reported results indicate that metamorphic quantum dots could be valuable candidates as single photon sources for long wavelength telecom windows.

[Three-dimensional Fluorescence Spectral Characteristics of Different Molecular Weight Fractionations of Dissolved Organic Matter in the Water-level Fluctuation Zones of Three Gorges Reservoir Areas].

PubMed

Chen, Xue-shuang; Jiang, Tao; Lu, Song; Wei, Shi-qiang; Wang, Ding-yong; Yan, Jin-long

2016-03-15

The study of the molecular weight (MW) fractions of dissolved organic matter (DOM) in aquatic environment is of interests because the size plays an important role in deciding the biogeochemical characteristics of DOM. Thus, using ultrafiltration ( UF) technique combined with three-dimensional fluorescence spectroscopy, DOM samples from four sampling sites in typical water-level fluctuation zones of Three Gorge Reservoir areas were selected to investigate the differences of properties and sources of different DOM MW fractions. The results showed that in these areas, the distribution of MW fractions was highly dispersive, but the approximately equal contributions from colloidal (Mr 1 x 10³-0.22 µm) and true dissolved fraction (Mr < 1 x 10³) to the total DOC concentration were found. Four fluorescence signals (humic-like A and C; protein-like B and T) were observed in all MW fractions including bulk DOM, which showed the same distribution trend: true dissolved > low MW (Mr 1 x 10³-10 x 10³) > medium MW (Mr 10 x 10³-30 x 10³) > high MW (Mr 30 x 10³-0.22 µm). Additionally, with decreasing MW fraction, fluorescence index (FI) and freshness index (BIX) increased suggesting enhanced signals of autochthonous inputs, whereas humification index ( HIX) decreased indicating lowe humification degree. It strongly suggested that terrestrial input mainly affected the composition and property of higher MW fractions of DOM, as compared to lower MW and true dissolved fractions that were controlled by autochthonous sources such as microbial and alga activities, instead of allochthonous sources. Meanwhile, the riparian different land-use types also affected obviously on the characteristics of DOM. Therefore, higher diversity of land-use types, and also higher complexity of ecosystem and landscapes, induced higher heterogeneity of fluorescence components in different MW fraction of DOM.

Tracking Changes in Dissolved Organic Matter Patterns in Perennial Headwater Streams Throughout a Hydrologic Year Using In-situ Sensors and Optical Properties

NASA Astrophysics Data System (ADS)

Armstrong, A.; Epting, S.; Hosen, J. D.; Palmer, M.

2015-12-01

Dissolved organic matter (DOM) plays a central role in freshwater streams but key questions remain unanswered about temporal patterns in its quantity and composition. DOM in perennial streams in the temperate zone is a complex mixture reflecting a variety of sources such as leached plant material, organic matter from surrounding soils, and microbial processes in the streams themselves. Headwater perennial streams in the Tuckahoe Creek watershed of the Atlantic coastal plain (Maryland, USA) drain a mosaic of land cover types including row crops, forests, and both forested and marshy small depressional wetlands. Wetland-stream surface hydrologic connections generally occur between mid-fall and late spring, coinciding with peak wetland hydrologic expression (i.e. highest groundwater levels and surface inundation extent). When inundated, these wetlands contain high DOM concentrations, and surface connections may serve as conduits for downstream export. We hypothesized that changes in wetland-stream surface hydrologic connectivity would affect patterns of DOM concentration and composition in these streams. We deployed 6 sondes equipped with fluorescent DOM sensors in 4 perennial streams, 1 forested wetland, and the larger downstream channel draining all study sites for the 2015 water year. The 4 headwater streams drain areas containing forested wetlands and have documented temporary channel connections. Combined with baseflow and stormflow sampling, the sondes provided 15 minute estimates of dissolved organic carbon (DOC) concentrations. This resolution provided insights into patterns of DOC concentration across temporal scales from daily rhythms to seasonal changes, during both baseflow and storm conditions. Discrete measurements of absorbance and fluorescence provided information about DOM composition throughout the study. Together these measurements give a detailed record of DOM dynamics in multiple perennial headwater streams for an entire year. This information could inform future studies, such as investigations into stream network scale thresholds in DOM cycling, carbon cycling modelling for the study region, or understanding the impact of wetlands sometimes considered geographically isolated on downstream ecosystems.

Molecular characterization of dissolved organic matter (DOM): a critical review.

PubMed

Nebbioso, Antonio; Piccolo, Alessandro

2013-01-01

Advances in water chemistry in the last decade have improved our knowledge about the genesis, composition, and structure of dissolved organic matter, and its effect on the environment. Improvements in analytical technology, for example Fourier-transform ion cyclotron (FT-ICR) mass spectrometry (MS), homo and hetero-correlated multidimensional nuclear magnetic resonance (NMR) spectroscopy, and excitation emission matrix fluorimetry (EEMF) with parallel factor (PARAFAC) analysis for UV-fluorescence spectroscopy have resulted in these advances. Improved purification methods, for example ultrafiltration and reverse osmosis, have enabled facile desalting and concentration of freshly collected DOM samples, thereby complementing the analytical process. Although its molecular weight (MW) remains undefined, DOM is described as a complex mixture of low-MW substances and larger-MW biomolecules, for example proteins, polysaccharides, and exocellular macromolecules. There is a general consensus that marine DOM originates from terrestrial and marine sources. A combination of diagenetic and microbial processes contributes to its origin, resulting in refractory organic matter which acts as carbon sink in the ocean. Ocean DOM is derived partially from humified products of plants decay dissolved in fresh water and transported to the ocean, and partially from proteinaceous and polysaccharide material from phytoplankton metabolism, which undergoes in-situ microbial processes, becoming refractory. Some of the DOM interacts with radiation and is, therefore, defined as chromophoric DOM (CDOM). CDOM is classified as terrestrial, marine, anthropogenic, or mixed, depending on its origin. Terrestrial CDOM reaches the oceans via estuaries, whereas autochthonous CDOM is formed in sea water by microbial activity; anthropogenic CDOM is a result of human activity. CDOM also affects the quality of water, by shielding it from solar radiation, and constitutes a carbon sink pool. Evidence in support of the hypothesis that part of marine DOM is of terrestrial origin, being the result of a long-term carbon sedimentation, has been obtained from several studies discussed herein.

The Cimmerian accretionary wedge of Anarak, Central Iran

NASA Astrophysics Data System (ADS)

Zanchi, Andrea; Malaspina, Nadia; Zanchetta, Stefano; Berra, Fabrizio; Benciolini, Luca; Bergomi, Maria; Cavallo, Alessandro; Javadi, Hamid Reza; Kouhpeyma, Meyssam

2015-04-01

The occurrence in Iran of several ophiolite belts dating between Late Palaeozoic to Triassic poses several questions on the possible existence of various sutures marking the closure of the Palaeotethys ocean between Eurasia and this Gondwana-derived microplate. In this scenario, the Anarak region in Central Iran still represents a conundrum. Contrasting geochronological, paleontological, paleomagnetic data and reported field evidence suggest different origins for the Anarak Metamorphic Complex (AMC). The AMC is either interpreted, as: (1) relict of an accretionary wedge developed at the Eurasia margin during the Palaeotethys subduction as part of the Cimmerian suture zone of NE Iran, displaced to Central Iran by a large counter-clockwise rotation of the central Iranian blocks; (2) autochthonous unit forming a secondary branch of the main suture zone. Our structural, petrographic and geochemical data indicate that the AMC consists of several metamorphic units also including dismembered "ophiolites" which display different tectono-metamorphic evolutions. Three main ductile deformational events can be distinguished in the AMC. The Morghab and Chah Gorbeh complexes preserve a different M1 metamorphism, characterized by blueschist relics in the S1 foliation of the former unit, and greenschist assemblages in the latter. They share a subsequent similar D2 deformational and M2 metamorphic history, showing a prograde metamorphism with syn- to post-deformation growth of blueschist facies mineral assemblages on pre-existing greenschist facies associations. High pressure, low temperature (HP/LT) metamorphism responsible for the growth of sodic amphibole has been recognized also within marble lenses at the contact between the Chah Gorbeh Complex and serpentinites. Evidence of HP/LT metamorphism also occurs in glaucophane-bearing meta-pillow lavas and serpentinites, which contain antigorite and form most of the "ophiolites" within the AMC. Structural relationships show that the Chah Gorbeh and Morghab units and the "ophiolites" were tectonically coupled within an accretionary wedge before the D2 folding stage. The other units of the AMC lack evidence of HP metamorphism in the area around Anarak, especially the Lakh Marble, a large thrust sheet that occupies the uppermost structural position in the AMC. Available radiometric ages of trondhjemite dikes and stocks that intruded the accretionary wedge, as well as our new data, constrain the subduction event at the end of the Carboniferous, before 290 Ma. These data suggest that the AMC is part of an allochthonous crustal fragment belonging to the Variscan belt developed along the southern Eurasian margin before the Cimmerian collision of Iran. Subsequent deformational events that occurred during the Mesozoic and the Cenozoic, up to the Miocene and possibly later, resulted in folding, thrusting and faulting that dismembered the original structure of the wedge accompanying its displacement to the present day position.

Early Tertiary Anaconda metamorphic core complex, southwestern Montana

USGS Publications Warehouse

O'Neill, J. M.; Lonn, J.D.; Lageson, D.R.; Kunk, Michael J.

2004-01-01

A sinuous zone of gently southeast-dipping low-angle Tertiary normal faults is exposed for 100 km along the eastern margins of the Anaconda and Flint Creek ranges in southwest Montana. Faults in the zone variously place Mesoproterozoic through Paleozoic sedimentary rocks on younger Tertiary granitic rocks or on sedimentary rocks older than the overlying detached rocks. Lower plate rocks are lineated and mylonitic at the main fault and, below the mylonitic front, are cut by mylonitic mesoscopic to microscopic shear zones. The upper plate consists of an imbricate stack of younger-on-older sedimentary rocks that are locally mylonitic at the main, lowermost detachment fault but are characteristically strongly brecciated or broken. Kinematic indicators in the lineated mylonite indicate tectonic transport to the east-southeast. Syntectonic sedimentary breccia and coarse conglomerate derived solely from upper plate rocks were deposited locally on top of hanging-wall rocks in low-lying areas between fault blocks and breccia zones. Muscovite occurs locally as mica fish in mylonitic quartzites at or near the main detachment. The 40Ar/39Ar age spectrum obtained from muscovite in one mylonitic quartzite yielded an age of 47.2 + 0.14 Ma, interpreted to be the age of mylonitization. The fault zone is interpreted as a detachment fault that bounds a metamorphic core complex, here termed the Anaconda metamorphic core complex, similar in age and character to the Bitterroot mylonite that bounds the Bitterroot metamorphic core complex along the Idaho-Montana state line 100 km to the west. The Bitterroot and Anaconda core complexes are likely components of a continuous, tectonically integrated system. Recognition of this core complex expands the region of known early Tertiary brittle-ductile crustal extension eastward into areas of profound Late Cretaceous contractile deformation characterized by complex structural interactions between the overthrust belt and Laramide basement uplifts, overprinted by late Tertiary Basin and Range faulting. ?? 2004 NRC Canada.

The case for simultaneous deformation, metamorphism and plutonism: an example from Proterozoic rocks in central Arizona

NASA Astrophysics Data System (ADS)

Karlstrom, K. E.; Williams, M. L.

1995-01-01

The syntectonic 1.70 Ga Crazy Basin Monzogranite provides an example of the complex spatial and temporal interactions between metamorphism, deformation, and plutonism. Synchronous plutonism and deformation is indicated by syn-shortening dikes, sills, and veins; parallel magmatic and solid state fabrics; fabrics in xenoliths; and a foliation triple point. Synchronous plutonism and metamorphism is indicated by a systematic increase from 400 °C to 630 °C towards the pluton at a constant pressure of 300 MPa (3 kb). Temperatures are consistent with a conductive cooling model in which a 700 °C pluton was emplaced into country rocks undergoing greenschist facies regional metamorphism. Synchronous deformation and metamorphism is indicated by porphyroblast inclusion geometries that document the synmetamorphic development of the S2 cleavage. The pluton was emplaced adjacent to the Shylock shear zone during progressive shortening. Emplacement of granite as NE-trending sheets was facilitated by temporal partitioning of transpressional convergence into strike-slip and dip-slip components. At the scale of the pluton's aureole and on the relatively rapid time scale of 10 3-10 6 y, regional deformation and metamorphism were punctuated by thermal softening and increased diffusion rates. Data suggests that accretion of Proterozoic arcs in Arizona involved diachronous pluton-enhanced deformation and associated high temperature-low pressure regional metamorphism.

Wet-dry cycles impact DOM retention in subsurface soils

NASA Astrophysics Data System (ADS)

Olshansky, Yaniv; Root, Robert A.; Chorover, Jon

2018-02-01

Transport and reactivity of carbon in the critical zone are highly controlled by reactions of dissolved organic matter (DOM) with subsurface soils, including adsorption, transformation and exchange. These reactions are dependent on frequent wet-dry cycles common to the unsaturated zone, particularly in semi-arid regions. To test for an effect of wet-dry cycles on DOM interaction and stabilization in subsoils, samples were collected from subsurface (Bw) horizons of an Entisol and an Alfisol from the Catalina-Jemez Critical Zone Observatory and sequentially reacted (four batch steps) with DOM extracted from the corresponding soil litter layers. Between each reaction step, soils either were allowed to air dry (wet-dry treatment) before introduction of the following DOM solution or were maintained under constant wetness (continually wet treatment). Microbial degradation was the dominant mechanism of DOM loss from solution for the Entisol subsoil, which had higher initial organic C content, whereas sorptive retention predominated in the lower C Alfisol subsoil. For a given soil, bulk dissolved organic C losses from solution were similar across treatments. However, a combination of Fourier transform infrared (FTIR) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopic analyses revealed that wet-dry treatments enhanced the interactions between carboxyl functional groups and soil particle surfaces. Scanning transmission X-ray microscopy (STXM) data suggested that cation bridging by Ca2+ was the primary mechanism for carboxyl association with soil surfaces. STXM data also showed that spatial fractionation of adsorbed OM on soil organo-mineral surfaces was diminished relative to what might be inferred from previously published observations pertaining to DOM fractionation on reaction with specimen mineral phases. This study provides direct evidence of the role of wet-dry cycles in affecting sorption reactions of DOM to a complex soil matrix. In the soil environment, where wet-dry cycles occur at different frequencies from site to site and along the soil profile, different interactions between DOM and soil surfaces are expected and need to be considered for the overall assessment of carbon dynamics.

Middle Ordovician subduction of continental crust in the Scandinavian Caledonides: an example from Tjeliken, Seve Nappe Complex, Sweden

NASA Astrophysics Data System (ADS)

Fassmer, Kathrin; Klonowska, Iwona; Walczak, Katarzyna; Andersson, Barbro; Froitzheim, Nikolaus; Majka, Jarosław; Fonseca, Raúl O. C.; Münker, Carsten; Janák, Marian; Whitehouse, Martin

2017-12-01

The Seve Nappe Complex of the Scandinavian Caledonides is thought to be derived from the distal passive margin of Baltica which collided with Laurentia in the Scandian Phase of the Caledonian Orogeny at 430-400 Ma. Parts of the Seve Nappe Complex were affected by pre-Scandian high- and ultrahigh-pressure metamorphism, in a tectonic framework that is still unclear, partly due to uncertainties about the exact timing. Previous age determinations yielded between 505 and 446 Ma, with a general trend of older ages in the North (Norrbotten) than in the South (Jämtland). New age determinations were performed on eclogite and garnet-phengite gneiss at Tjeliken in northern Jämtland. Thermodynamic modelling yielded peak metamorphic conditions of 25-27 kbar/680-760 °C for the garnet-phengite gneiss, similar to published peak metamorphic conditions of the eclogite (25-26 kbar/650-700 °C). Metamorphic rims of zircons from the garnet-phengite gneiss were dated using secondary ion mass spectrometry and yielded a concordia age of 458.9 ± 2.5 Ma. Lu-Hf garnet-whole rock dating yielded 458 ± 1.0 Ma for the eclogite. Garnet in the eclogite shows prograde major-element zoning and concentration of Lu in the cores, indicating that this age is related to garnet growth during pressure increase, i.e. subduction. The identical ages from both rock types, coinciding with published Sm-Nd ages from the eclogite, confirm subduction of the Seve Nappe Complex in Northern Jämtland during the Middle Ordovician in a fast subduction-exhumation cycle.

Characterizing Low Molecular Weight Organic Matter in Arctic Polygonal Tundra Soils to Identify Biogeochemical Hotspots Using a Dual-Separation, High-Resolution Mass Spectrometry Approach

NASA Astrophysics Data System (ADS)

Ladd, M.; Wullschleger, S. D.; Iversen, C. M.; Hettich, R.

2016-12-01

Reliably modeling biogeochemical processes (e.g. decomposition, plant-microbial competition for nutrients) across spatial or temporal scales requires elucidating the chemical composition of low molecular weight (LMW) dissolved soil organic matter (DOM). Our understanding is limited, however, by the wide-ranging physicochemical properties and high fluxes of these compounds, posing major challenges in detection, isolation, and quantification. Here, we developed and evaluated a sensitive, non-targeted approach to characterize LMW DOM in the Arctic, a unique system that is warming at a rate twice that of the global average and may have significant feedbacks to global C and N cycles. Soil cores were collected from a continuous permafrost, polygonal tundra landscape near Barrow, Alaska (71° 16' N) and sectioned into 5 cm increments. Water and salt extracts from each section were filtered and injected onto C18 reversed-phase or zwitterionic-type hydrophilic interaction chromatography (ZIC-pHILIC) columns for separation. LMW DOM profiles were obtained using high-resolution mass spectrometry (HRMS), and unique features, known and unknown, were characterized by LC retention time, accurate mass (m/z), and molecular fragmentation pattern. Coupling two orthogonal chromatographic separations with HRMS enabled the characterization of hundreds of analytes in a single measurement providing enhanced, high-throughput coverage of LMW DOM from soil extracts. The complexity and relative/absolute intensities of LMW DOM features (e.g. organic acids, amino sugars, peptides) varied across polygon type (high- or low-centered), extract condition, and with depth, providing an information-rich, molecular signal of LMW DOM availability across scales. Comprehensively profiling this complex mixture of small molecules of both biotic and abiotic origin provides a chemical signature of biological function, allowing for more reliable predictions of how discrete, molecular-scale processes may control landscape dynamics. In the Arctic, this platform can be leveraged to identify biogeochemical hotspots to gain insight into to how warming temperatures will impact microbial dynamics and CO2 and CH4 fluxes from these systems.

Isukasia area: Regional geological setting (includes excursion guide)

NASA Technical Reports Server (NTRS)

Nutman, A. P.; Rosing, M.

1986-01-01

A brief account of the geology of the Isukasis area is given and is biased toward the main theme of the itinerary for the area: What has been established about the protoliths of the early Archean rocks of the area - the Isua supracrustal belt and the Amitsoq gneisses? The area's long and complex tectonometamorphic history of events can be divided into episodes using a combination of dike chronology, isotopic, and petrological studies. The earliest dikes, the ca 3700 Ma Inaluk dikes, intrude the earliest (tonalitic) components of the Amitsoq gneisses but are themselves cut up by the injection of the younger (granitic and pegmatitic) phases of the Amitsoq gneisses of the area. The areas of low late Archean deformation, strongly deformed early Archean mafic rocks have coarse grained metamorphic segregations and are cut by virtually undeformed mid-Archean Tarssartoq (Ameralik) dikes devoid of metamorphic segregations. The shows that the area was affected by regional amphibolite facies metamorphism in the early Archean. Late Archean and Proterozoic metamorphic imprints are marked to very strong in the area. Much of the early Archean gneiss complex was already highly deformed when the mid-Archean Tarssartoq dikes were intruded.

The Influences of Dissolved Organic Matter on Mercury Biogeochemistry in Mesocosm Experiments in the Florida Everglades

NASA Astrophysics Data System (ADS)

Aiken, G. R.; Gilmour, C. A.; Krabbenhoft, D. P.; Orem, W.

2007-12-01

Interactions of mercury (Hg) with dissolved organic matter (DOM) play important roles in controlling reactivity, bioavailability and transport of Hg in aquatic systems. Laboratory experiments using a variety of organic matter isolates from surface waters in the Florida Everglades indicate that DOM binds Hg very strongly and is the dominant ligand for Hg in the absence of sulfide. These experiments have also shown that the presence of DOM influences the geochemical behavior of cinnabar (HgS) through the stabilization of nanocolloidal HgS resulting in relatively high Hg concentrations under supersaturated conditions with respect to HgS, a common condition in waters containing measurable sulfide concentrations. In this paper, the results of in-situ mesocosm experiments designed to directly measure the effects of DOM -Hg interactions on Hg biogeochemistry will be described. In these experiments, mesocosms (wetland enclosures), located in the central Everglades region of Water Conservation Area 3A (WCA 3A15), were amended with isotopically enriched Hg (200Hg, 202Hg), sulfate (SO4=) and the hydrophobic organic acid (HPOA) fraction of DOM from a site (F1) in the eutrophic northern Everglades. The use of stable isotope spikes in these studies allowed us to examine the delivery of Hg to surface soils (which are the predominant zones of methylation); partitioning of Hg and MeHg among phases (which impacts bioavailability); net MeHg production; loss of Hg and MeHg through photodemethylation, reduction and volatization; and bioaccumulation. The F1 HPOA isolate, obtained using XAD resins, was more aromatic, had a greater specific ultra-violet absorbance and had previously been shown to be more reactive with Hg than the DOM present at the 3A15 site. The F1 HPOA isolate formed strong DOM-Hg complexes (KDOM') = 1023.2 L kg-1 at pH = 7.0 and I = 0.1) and effectively inhibited the precipitation of HgS in laboratory experiments. Select mesocosms were amended with either F1-HPOA or SO4= resulting in a range of concentrations for each constituent. For the DOM amended mesocosms, DOC concentrations increased from 50-100% and the overall SUVA increased from 2.9 to 3.7 L mg C-1 m-1 relative to control mesocosms, indicating that both the concentration and overall reactivity of the DOM in the amended mesocosms had been altered substantially. In these mesocosms, the concentrations of both ambient and isotopically enriched dissolved Hg increased significantly compared to controls. Greater concentrations of both dissolved ambient and labeled methylmercury were also observed in the DOM amended mesocosms indicating that the added DOM increased Hg bioavailabilty of both Hg pools for methylation. In addition, DOM shielded Hg and MeHg from photodemethylation and volatilization, however, it inhibited subsequent MeHg bioaccumulation. Overall, the addition of DOM resulted in increased concentrations of labeled methylmercury comparable to those measured in mesocosms amended with SO4= suggesting that DOM is an important constituent influencing the methylation of Hg. This effect is likely due to increased concentrations of dissolved Hg in the DOM amended mesocosms.

P-T evolution of metasedimentary rocks of the Santa Filomena Complex, Riacho do Pontal Orogen, Borborema Province (NE Brazil): Geothermobarometry and metamorphic modelling

NASA Astrophysics Data System (ADS)

Santos, Felipe H.; Amaral, Wagner S.; Luvizotto, George L.; Martins de Sousa, Daniel F.

2018-03-01

We present in this paper petrologic data and discuss the pressure-temperature (P-T) metamorphic history of the neoproterozoic metasedimentary rocks of the Santa Filomena Complex, Riacho do Pontal Orogen, which is inserted in the southern portion of the Borborema Province (Northeast Brazil). Therefore, the data provide constraints on metamorphic evolution during Neoproterozoic Brasiliano Orogeny in Northeast Brazil. The rocks studied are aluminous schists and paragneisses. Silver-gray and red pelitic schists are intensely deformed, biotite-muscovite rich, contain centimeter-sized garnet, staurolite and kyanite porphyroblasts, and subordinately plagioclase and quartz. Paragneisses are from light gray to dark gray colored, medium to coarse-grained and display a well-spaced foliated matrix of biotite, and kyanite and garnet porphyroblasts. Locally, the schists and paragneisses are migmatized. Pressure-temperature modelling based on thermobarometric calculations indicate that metamorphism reached 643 °C with pressures estimated in 12 kbar. Pre-peak and post-peak metamorphic conditions are constrained by mineralogical and textural relationships: garnet inclusion-rich and inclusion-free (possible of higher T) are documented and the inclusion-rich core probably indicates a Sn-1 foliation that was transposed by Sn. The pre-peak stage most probably occurred close to 500 °C and 8 kbar, in upper greenschist to lower amphibolite facies metamorphism along kyanite stability field. We also propose that post-peak stage was associated with isothermal decompression along a possible path of tectonic exhumation in conditions of 600 °C and 7 kbar. To further evaluate the equilibrium condition, pressure-temperature pseudosections were calculated for the metasedimentary rocks. Thus, the estimated metamorphic peak took place in the upper amphibolite facies. A suggested clockwise pressure-temperature path is compatible with the regional tectonic setting of continent-continent collision which occurred in the Late Neoproterozoic of Borborema Province, during the Brasiliano Orogeny.

Metamorphic and geochronogical study of the Triassic El Oro metamorphic complex, Ecuador: Implications for high-temperature metamorphism in a forearc zone

NASA Astrophysics Data System (ADS)

Riel, N.; Guillot, S.; Jaillard, E.; Martelat, J.-E.; Paquette, J.-L.; Schwartz, S.; Goncalves, P.; Duclaux, G.; Thebaud, N.; Lanari, P.; Janots, E.; Yuquilema, J.

2013-01-01

In the forearc of the Andean active margin in southwest Ecuador, the El Oro metamorphic complex exhibits a well exposed tilted forearc section partially migmatized. We used Raman spectroscopy on carbonaceous matter (RSCM) thermometry and pseudosections coupled with mineralogical and textural studies to constrain the pressure-temperature (P-T) evolution of the El Oro metamorphic complex during Triassic times. Our results show that anatexis of the continental crust occurred by white-mica and biotite dehydration melting along a 10 km thick crustal domain (from 4.5 to 8 kbar) with increasing temperature from 650 to 700 °C. In the biotite dehydration melting zone, temperature was buffered at 750-820 °C in a 5 km thick layer. The estimated average thermal gradient during peak metamorphism is of 30 °C/km within the migmatitic domain can be partitioned into two apparent gradients parts. The upper part from surface to 7 km depth records a 40-45 °C/km gradient. The lower part records a quasi-adiabatic geotherm with a 10 °C/km gradient consistent with an isothermal melting zone. Migmatites U-Th-Pb geochronology yielded zircon and monazite ages of 229.3 ± 2.1 Ma and 224.5 ± 2.3 Ma, respectively. This thermal event generated S-type magmatism (the Marcabeli granitoid) and was immediately followed by underplating of the high-pressure low-temperature (HP-LT) Arenillas-Panupalí unit at 225.8 ± 1.8 Ma. The association of high-temperature low-pressure (HT-LP) migmatites with HP-LT unit constitutes a new example of a paired metamorphic belt along the South American margin. We propose that in addition to crustal thinning, underplating of the Piedras gabbroic unit before 230 Ma provided the heat source necessary to foster crustal anatexis. Furthermore, its MORB signature shows that the asthenosphere was involved as the source of the heat anomaly. S-type felsic magmatism is widespread during this time and suggests that a large-scale thermal anomaly affected a large part of the South American margin during the late Triassic. We propose that crustal anatexis is related to an anomaly that arose during subduction of the Panthalassa ocean under the South American margin. Slab verticalization or slab break-off can be invoked as the origin of the upwelling of the asthenosphere.

Metamorphic and tectonic evolution of the Greater Himalayan Crystalline Complex in Nyalam region, south Tibet

NASA Astrophysics Data System (ADS)

Wang, Jia-Min; Zhang, Jin-Jiang; Rubatto, Daniela

2016-04-01

Recent studies evoke dispute whether the Himalayan metamorphic core - Greater Himalayan Crystalline Complex (GHC) - was exhumed as a lateral crustal flow or a critical taper wedge during the India-Asia collision. This contribution investigated the evolution of the GHC in the Nyalam region, south Tibet, with comprehensive studies on structural kinematics, metamorphic petrology and geochronology. The GHC in the Nyalam region can be divided into the lower and upper GHC. Phase equilibria modelling and conventional thermobarometric results show that peak temperature conditions are lower in the lower GHC (~660-700°C) and higher in the upper GHC (~740-780°C), whereas corresponding pressure conditions at peak-T decrease from ~9-13 kbar to ~4 kbar northward. Monazite, zircon and rutile U-Pb dating results reveal two distinct blocks within the GHC of the Nyalam region. The upper GHC underwent higher degree of partial melting (15-25%, via muscovite dehydration melting) that initiated at ~32 Ma, peaked at ~29 Ma to 25 Ma, possibly ended at ~20 Ma. The lower GHC underwent lower degree of melting (0-10%) that lasted from 19 to 16 Ma, which was produced mainly via H2O-saturated melting. At different times, both the upper and lower blocks underwent initial slow cooling (35 ± 8 and 10 ± 5°C/Myr, respectively) and subsequent rapid cooling (120 ± 40°C/Myr). The established timescale of metamorphism suggests that high-temperature metamorphism within the GHC lasted a long duration (~15 Myr), whereas duration of partial melting lasted for ~3 Myr in the lower GHC and lasted for 7-12 Myr in the upper GHC. The documented diachronous metamorphism and discontinuity of peak P-T conditions implies the presence of the Nyalam Thrust in the study area. This thrust is probably connected to the other thrusts in Nepal and Sikkim Himalaya, which extends over ~800 km and is named the "High Himalayan Thrust". Timing of activity along this thrust is at ~25-16 Ma, which is coeval with active timing along the South Tibetan detachment (27-16 Ma) but precedes that along the MCT (16-10 Ma). Comparison between the obtained P-T-t data and model predictions implies that a lateral crustal flow process dominated the exhumation of the high-grade upper GHC migmitites during 25-16 Ma, whereas a critical taper thrusting process dominated the exhumation of the MCT zone nonmigmatites and cooled migmatites in the lower GHC at 16-10 Ma. In other words, at different temporal and spatial scale, both propagating thrusting along large tectonic boundaries and a low-viscosity melting crust could contribute to the exhumation of high-grade metamorphic rocks in Himalaya-like large hot collisional orogens. KEY WORDS: Greater Himalayan Crystalline Complex; P-T path; U-Pb geochronology; channel flow; tectonic discontinuity References: Wang, J.M., Rubatto, D., Zhang, J.J., 2015a. Timing of partial melting and cooling across the Greater Himalayan Crystalline Complex (Nyalam, central Himalaya): in-sequence thrusting and its implications. Journal of Petrology, 56, 1677-1702. Wang, J.M., Zhang, J.J., Wei, C.J., Rai, S.M., Wang, M., Qian, J.H., 2015b. Characterizing the metamorphic discontinuity across the Main Central Thrust Zone of eastern-central Nepal. Journal of Asian Earth Sciences 101, 83-100. Wang, J.M., Zhang, J.J., Wang, X.X., 2013. Structural kinematics, metamorphic P-T profiles and zircon geochronology across the Greater Himalayan Crystalline Complex in south-central Tibet: implication for a revised channel flow. Journal of Metamorphic Geology 31, 607-628.

Thermal Evolution of Juvenile Subduction Zones ' New Constraints from Lu-Hf Geochronology on HP oceanic rocks (Halilbaǧi, Central Anatolia)

NASA Astrophysics Data System (ADS)

Pourteau, Amaury; Scherer, Erik; Schmidt, Alexander; Bast, Rebecca

2015-04-01

The thermal structure of subduction zones plays a key role on mechanical and chemical processes taking place along the slab-mantle interface. Until now, changes through time of this thermal structure have been explored mostly by the means of numerical simulations. However, both "warm" (i.e., epidote-bearing), and "cold" (i.e., lawsonite-bearing) HP oceanic rocks have been reported in some fossil subduction complexes exposed at the Earth's surface (e.g., Franciscan Complex, California; Rio San Juan Complex, Hispañola; Halilbağı Unit, Central Anatolia). These a-priori "incompatible" rocks witness different thermal stages of ancient subduction zones and their study might provide complementary constraints to numerical models. To decipher the meaning of these contrasting metamorphic rocks in the Halilbağı Unit, we are carrying out Lu-Hf geochronology on garnet (grt) and lws from a variety of HP oceanic rocks, as well as the metamorphic sole of the overlying ophiolite. We selected five samples that are representative of the variety of metamorphic evolutions (i.e. peak conditions and P-T paths) encountered in this area. Preliminary analyses yielded 110 Ma (grt-hbl isochron) for a sub-ophiolitic grt amphibolite; 92 Ma (grt-omp) for an eclogite with prograde and retrograde ep; 90 Ma (grt-omp) for an eclogitic metabasite with prograde ep and retrograde ep+lws; 87 Ma (grt-gln) for a lws eclogite with prograde ep; and 86 Ma (grt-gln) for a blueschist with prograde and retrograde lws. These ages are mainly two-point isochrons. Further-refined data will be presented at the EGU General Assembly 2015, in Vienna. The consistent younging trend from "warm" to "cold" metamorphic rocks revealed by these first-order results points to metamorphic-sole formation during the initiation of intra-oceanic subduction at ~110 Ma, and subsequent cooling of the slab-mantle interface between 92 and 86 Ma. Therefore, the contrasting metamorphic evolutions encountered in the Halilbağı Unit record the progressive thermal maturation of the juvenile Neotethyan subduction zone. This period of ~23 myr between subduction initiation and thermal "steady state" is significantly shorter than that obtained for the Rio San Juan Complex (~60 myr; Krebs et al. 2008, Lithos, 103, 106-137), but compares well with that for the Franciscan Complex (~22 myr; Anczkiewicz et al. 2004, EPSL, 225, 147-161) and falls in the range predicted in numerical simulations (e.g., Gerya et al. 2002, Tectonics, 21/6, 1056).

Geologic and Geochronologic Studies of the Early Proterozoic Kanektok Metamorphic Complex of Southwestern Alaska

USGS Publications Warehouse

Turner, Donald L.; Forbes, Robert B.; Aleinikoff, John N.; McDougall, Ian; Hedge, Carl E.; Wilson, Frederic H.; Layer, Paul W.; Hults, Chad P.

2009-01-01

The Kanektok complex of southwestern Alaska appears to be a rootless terrane of early Proterozoic sedimentary, volcanic, and intrusive rocks which were metamorphosed to amphibolite and granulite facies and later underwent a pervasive late Mesozoic thermal event accompanied by granitic plutonism and greenschist facies metamorphism of overlying sediments. The terrane is structurally complex and exhibits characteristics generally attributed to mantled gneiss domes. U-Th-Pb analyses of zircon and sphene from a core zone granitic orthogneiss indicate that the orthogneiss protolith crystallized about 2.05 b.y. ago and that the protolithic sedimentary, volcanic and granitic intrusive rocks of the core zone were metamorphosed to granulite and amphibolite facies about 1.77 b.y. ago. A Rb-Sr study of 13 whole-rock samples also suggests metamorphism of an early Proterozoic [Paleoproterozoic] protolith at 1.77 Ga, although the data are scattered and difficult to interpret. Seventy-seven conventional 40K/40Ar mineral ages were determined for 58 rocks distributed throughout the outcrop area of the complex. Analysis of the K-Ar data indicate that nearly all of these ages have been totally or partially reset by a pervasive late Mesozoic thermal event accompanied by granitic plutonism and greenschist facies metamorphism. Several biotites gave apparent K-Ar ages over 2 Ga. These ages appear to be controlled by excess radiogenic 40Ar produced by the degassing protolith during the 1.77 Ga metamorphism and incorporated by the biotites when they were at temperatures at which Ar could diffuse through the lattice. Five amphibolites yielded apparent Precambrian 40K/40Ar hornblende ages. There is no evidence that these hornblende ages have been increased by excess argon. The oldest 40K/40Ar hornblende age of 1.77 Ga is identical to the sphene 207Pb/206Pb orthogneiss age and to the Rb-Sr 'isochron' age for six of the 13 whole-rock samples. The younger hornblende ages are interpreted as having been partially reset during the late Mesozoic thermal event. 40Ar/39Ar incremental heating experiments suggest metamorphism occurred at least 1.2 b.y. ago but do not exhibit high temperature plateau ages significantly older than the 40Ar/39Ar total fusion ages of these samples. The age spectra are much more uniform than expected from a terrane with such a complex thermal history, perhaps caused by the small grain size of the samples which may possibly be less than the effective Ar diffusion radii of the analyzed hornblendes.

Signatures of Pacific-type orogeny in Lleyn and Anglesey areas, northwest Wales

NASA Astrophysics Data System (ADS)

Asanuma, H.; Okada, Y.; Sawaki, Y.; Yamamoto, S.; Hirata, T.; Maruyama, S.

2014-12-01

The orogeny is a fundamental process of plate tectonics, and its record is useful for understanding of ancient plate motion. Geotectonic history of British isles has been explained by collision-type orogeny accompanied by closure of Iapetus ocean. High pressure metamorphic rocks such as blueschist and eclogite characterizing Pacific-type orogeny occur in some places, but have not attracted much interests because of their smallness. The subduction-related (Pacific-type) orogeny is characterized by contemporaneous formation of a batholith belt, a regional metamorphic belt (high P/T type) and an accretionary complex. Late Proterozoic-Cambrian (677-498 Ma) calc-alkaline volcano-plutonic complexes crop out in Lleyn and Anglesey areas, northwest Wales. The metamorphic age of high-P/T metamorphic belt in eastern Anglesey was constrained by Ar-Ar isochron age of 560-550 Ma. However, depositional age of the rocks composing accretionary complex wasn't fully constrained due to the limited zircon U-Pb age data and vague microfossil records. Monian Supergroup at Lleyn and Anglesey areas includes three groups; South Stack Group (Gp), New Harbour Gp and Gwna Gp. The Gwna Gp is located at the structural top and includes typical rocks of an ocean plate stratigraphy (OPS), a fundamental unit composing of an accretionary complex. We described detailed geological map and reconstructed the OPSs at some localities with careful attention to layer-parallel thrust. In order to constrain the sedimentary ages of each OPS, we collected sandstones from individual OPSs. We determined U-Pb ages of detrital zircons from the sandstones with LA-ICP-MS at Kyoto University. We adopted the youngest age of the detrital zircons as a constraint of sedimentary age. The results indicate that sediments in Gwna Gp deposited from 623 ± 17 Ma to 535 ± 14 Ma. These are contemporary with the ages of both batholith belt and regional metamorphic belt. In addition, it became evident that structurally upper level is older than lower level. This structurally downward-younging polarity is one of the characteristics of accretionary complex. Therefore, we concluded that the accretionary complex at northwestern Wales was formed between 623 ± 17 Ma and 535 ± 14 Ma, and the subduction-related Pacific-type orogeny had formed a part of British Isles.

Detrital zircons from the Tananao metamorphic complex of Taiwan: Implications for sediment provenance and Mesozoic tectonics

NASA Astrophysics Data System (ADS)

Yui, T. F.; Maki, K.; Lan, C. Y.; Hirata, T.; Chu, H. T.; Kon, Y.; Yokoyama, T. D.; Jahn, B. M.; Ernst, W. G.

2012-05-01

Taiwan formed during the Plio-Pleistocene collision of Eurasia with the outboard Luzon arc. Its pre-Tertiary basement, the Tananao metamorphic complex, consists of the western Tailuko belt and the eastern Yuli belt. These circum-Pacific belts have been correlated with the high-temperature/low-pressure (HT/LP) Ryoke belt and the high-pressure/low-temperature (HP/LT) Sanbagawa belt of Japan, respectively. To test this correlation and to reveal the architecture and plate-tectonic history of the Tananao metamorphic basement, detrital zircons were separated from 7 metasedimentary rock samples for U-Pb dating by LA-ICPMS techniques. Results of the present study, coupled with previous data, show that (1) the Tailuko belt consists of a Late Jurassic to earliest Cretaceous accretionary complex sutured against a Permian-Early Jurassic marble ± metabasaltic terrane, invaded in the north by scattered Late Cretaceous granitic plutons; the latter as well as minor Upper Cretaceous cover strata probably formed in a circum-Pacific forearc; (2) the Yuli belt is a mid- to Late Cretaceous accretionary complex containing HP thrust sheets that were emplaced attending the Late Cenozoic Eurasian plate-Luzon arc collision; (3) these two Late Mesozoic belts are not coeval, and in part were overprinted by low-grade metamorphism during the Plio-Pleistocene collision; (4) accreted clastic sediments of the Tailuko belt contain mainly Phanerozoic detrital zircons, indicating that terrigenous sediments were mainly sourced from western Cathaysia, whereas in contrast, clastic rocks of the Yuli accretionary complex contain a significant amount of Paleoproterozoic and distinctive Neoproterozoic zircons, probably derived from the North China craton and the Yangtze block ± eastern Cathaysia, as a result of continent uplift/exhumation after the Permo-Triassic South China-North China collision; and (5) the Late Jurassic-Late Cretaceous formation of the Tananao basement complex precludes the possibility that the early Yanshanian (Early Jurassic) granitoids in southern China represent a landward arc contemporaneous with the later, outboard Tananao accretionary event.

Dating Paleogene Subduction in the Alborán Domain (Alpujárride Complex, S. Spain)

NASA Astrophysics Data System (ADS)

Williams, J. R.; Ashley, K.; Loewy, S. L.; Platt, J. P.

2016-12-01

The multimineral 87Rb/86Sr method has been used in recent studies to date subduction in high-pressure (HP) metamorphic belts of the Mediterranean region. In the Alpujárride Complex, the largest tectonic unit of the Alborán Domain, southern Spain, the timing of burial and HP metamorphism is controversial, with published 40Ar/39Ar white mica ages that range from 48Ma to 25Ma. Dating the HP event is complicated by a pervasive high-temperature (HT) metamorphic overprint (23-19Ma) associated with late-orogenic extension. We have identified 5 rock samples for 87Rb/86Sr dating which preserve a HP equilibrium assemblage: a garnet-staurolite-chloritoid schist, two calcareous Mg-chloritoid schists and two calcareous phyllites with previous 40Ar/39Ar ages of 48Ma and 41Ma. Improved constraints on the time gap between HP and HT metamorphism are important to test geodynamic models of the Alborán Domain, which range from prolonged thickening of continental lithosphere followed by extensional collapse, to punctuated subduction followed by back-arc extension. Furthermore, determining the onset and duration of HP metamorphism has broad implications for whether the Alborán Domain formed in the context of a single Alpine belt, or a separate and local accretionary setting. Lastly, this study will test the advantages and limitations of the 87Rb/86Sr method in a HP domain with a late HT overprint, a very common issue in orogenic systems.

Complex Catchment Processes that Control Stream Nitrogen and Organic Matter Concentrations in a Northeastern USA Upland Catchment

NASA Astrophysics Data System (ADS)

Sebestyen, S. D.; Shanley, J. B.; Pellerin, B.; Saraceno, J.; Aiken, G. R.; Boyer, E. W.; Doctor, D. H.; Kendall, C.

2009-05-01

There is a need to understand the coupled biogeochemical and hydrological processes that control stream hydrochemistry in upland forested catchments. At watershed 9 (W-9) of the Sleepers River Research Watershed in the northeastern USA, we use high-frequency sampling, environmental tracers, end-member mixing analysis, and stream reach mass balances to understand dynamic factors affect forms and concentrations of nitrogen and organic matter in streamflow. We found that rates of stream nitrate processing changed during autumn baseflow and that up to 70% of nitrate inputs to a stream reach were retained. At the same time, the stream reach was a net source of the dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) fractions of dissolved organic matter (DOM). The in-stream nitrate loss and DOM gains are examples of hot moments of biogeochemical transformations during autumn when deciduous litter fall increases DOM availability. As hydrological flowpaths changed during rainfall events, the sources and transformations of nitrate and DOM differed from baseflow. For example, during storm flow we measured direct inputs of unprocessed atmospheric nitrate to streams that were as large as 30% of the stream nitrate loading. At the same time, stream DOM composition shifted to reflect inputs of reactive organic matter from surficial upland soils. The transport of atmospheric nitrate and reactive DOM to streams underscores the importance of quantifying source variation during short-duration stormflow events. Building upon these findings we present a conceptual model of interacting ecosystem processes that control the flow of water and nutrients to streams in a temperate upland catchment.

Environmental characteristics and changes of sediment pore water dissolved organic matter in four Chinese lakes.

PubMed

Mostofa, Khan M G; Li, Wen; Wu, Fengchang; Liu, Cong-Qiang; Liao, Haiqing; Zeng, Li; Xiao, Min

2018-01-01

Sediment pore waters were examined in four Chinese lakes (Bosten, Qinghai, Chenghai and Dianchi) to characterise the sources of dissolved organic matter (DOM) and their microbial changes in the sediment depth profiles. Parallel factor (PARAFAC) modelling on the sample fluorescence spectra confirmed that the pore water DOM was mostly composed of two components with a mixture of both allochthonous and autochthonous fulvic acid-like substances in three lakes, except Lake Dianchi, and protein-like components in Lake Bosten. However, DOM in Lake Dianchi was composed of three components, including a fulvic acid-like, and two unidentified components, which could originate from mixed sources of either sewerage-impacted allochthonous or autochthonous organic matter (OM). Dissolved organic carbon (DOC) concentrations were typically high (583-7410 μM C) and fluctuated and increased vertically in the depth profile. The fluorescence intensity of the fulvic acid-like substance and absorbance at 254 nm increased vertically in the sediment pore waters of three lakes. A significant relationship between DOC and the fluorescence intensity of the fulvic acid-like component in the sediment pore waters of three lakes, except Lake Dianchi, suggested that the fulvic acid-like component could significantly contribute to total DOM and could originate via complex microbial processes in early diagenesis on OM (ca. phytoplankton, terrestrial plant material) in these lakes. Pore water DOM components could therefore be a useful indicator to assess the DOM sources of the lake sediment during sedimentation over the past several decades, which have been heavily affected by ambient terrestrial vegetation and human activities.

Analysis and Characterization of Dissolved Organic Matter in Ice Cores as Indicators of Past Environmental Conditions Using High Resolution FTICR-MS

NASA Astrophysics Data System (ADS)

Boschi, V.; Grannas, A. M.; Willoughby, A. S.; Catanzano, V.; Hatcher, P.

2015-12-01

With rapid changes in global temperatures, research aimed at better understanding past climatic events in order to predict future trends is an area of growing importance. Carbonaceous gases stored in ice cores are known to correlate with temperature change and provide evidence of such events. However, more complex forms of carbon preserved in ice cores such as dissolved organic matter (DOM) can provide additional information relating to changes in environmental conditions over time. The examination of ice core samples presents unique challenges including detection of ultra-low concentrations of organic material and extremely limited sample amounts. In this study, solid phase extraction techniques combined with ultra-high resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FTICR-MS) were utilized to successfully extract, concentrate and analyze the low concentrations of DOM in only 100 mL of ice core samples originating from various regions of Antarctica and Greenland. We characterize the DOM composition in each sample by evaluating elemental ratios, molecular formula distribution (CHO, CHON, CHOS and CHNOS) and compound class composition (lignin, tannin, lipid, condensed aromatic, protein and unsaturated hydrocarbon content). Upon characterization, we identified molecular trends in ice core DOM chemistry that correlated with past climatic events in addition to observing possible photochemical and microbial influences affecting DOM chemistry. Considering these samples range in age from 350-1175 years old, thus being formed during the Medieval Warm Period and Little Ice Age, we observed that DOM properties reflected anticipated changes in composition as influenced by warming and cooling events occurring during that time period.

Lunar anorthosite 15415: Texture, mineralogy, and metamorphic history

USGS Publications Warehouse

James, O.B.

1972-01-01

Lunar anorthosite 15415 consists almost entirely of anorthite (homogeneous anorthite 96.6 molecule percent), with accessory diopsidic augite and traces of hypersthene, ilmenite, and a silica mineral. The rock has had a complex metamorphic history. The texture reflects at least two episodes of shearing (followed by intense and partial recrystallization, respectively), one episode of cataclastic deformation, and one or more episodes of shattering and fragmentation.

First description of a metamorphic sole related to ophiolite obduction in the northern Caribbean: Geochemistry and petrology of the Güira de Jauco Amphibolite complex (eastern Cuba) and tectonic implications

NASA Astrophysics Data System (ADS)

Lázaro, C.; Blanco-Quintero, I. F.; Rojas-Agramonte, Y.; Proenza, J. A.; Núñez-Cambra, K.; García-Casco, A.

2013-10-01

The Güira de Jauco Amphibolite Complex underlies the Mayarí-Baracoa Ophiolitic Belt (eastern Cuba) and is composed of highly foliated amphibolite, locally with blocks of sheared serpentinitie that enclose concordant layers of amphibolite. These amphibolites are interpreted as remnants of a sub-ophiolitic metamorphic sole likely formed during late Cretaceous times before the initiation of the collision between the Caribbean and the North American plates. The complex includes common amphibolites (Hbl + Pl ± Ep ± Ttn ± Rt ± Qtz ± Ap), garnet amphibolites (Hbl + Grt + Pl + Ep ± Ttn ± Qtz ± Ap) and clinopyroxene amphibolites (Hbl + Pl + Cpx ± Ep ± Ttn ± Qtz ± Ap). Geochemical data indicates that the protoliths are igneous mafic rocks of basaltic composition that likely formed part of the upper and lower(?)crust of an oceanic lithosphere. Rare Earth element contents suggest a Mid-Ocean Ridge Basalt (MORB) origin. However, the enrichment in Large-Ion Lithophile elements and the depletion in NbTaTi as compared to Normal-MORB, suggests a suprasubduction scenario, either a back-arc or a fore-arc setting. The pressure-temperature estimates of metamorphism indicate that the entire amphibolite body underwent similar peak metamorphic conditions at 650-665 °C and 8.5-8.7 kbar (ca. 30 km depth), corresponding to a relatively high apparent geothermal gradient of 23 °C/km.

Cathodoluminescence of diamond as an indicator of its metamorphic history

NASA Astrophysics Data System (ADS)

Kopylova, Maya; Bruce, Loryn; Longo, Micaela; Ryder, John; Dobrzhinetskaya, Larissa

2010-05-01

Diamond displays a supreme resistance to chemical and mechanical weathering, ensuring its survival through complex and prolonged crustal processes, including metamorphism and exhumation. For these reasons, volcanic sources and secondary and tertiary collectors for detrital placer diamonds, like Ural or Bingara diamonds, may be difficult to determine. If metamorphic processes leave their marks on diamond, they can be used to reconstruct crustal geologic processes and ages of primary diamondiferous volcanics. Four diamond suites extracted from metamorphic rocks have been characterized using optical CL, infrared and CL spectroscopy, and photoluminescence at the liquid nitrogen temperature. The studied diamonds are from the ~2.7 Ga sedimentary conglomerate and lamprophyric breccia metamorphosed in the greenschist facies (Wawa, Northern Ontario, Canada) during the 2.67 Ga Kenoran orogeny, and from the ultra-high pressure (UHP) terranes of Kokchetav (Kazakhstan) and Erzgebirge (Germany) exhumated in the Paleozoic. Wawa diamonds (Type IaAB and Type II) displayed green, yellow, orange, and red CL colours controlled by the CL emittance at 520, 576 nm, and between 586 and 664 nm. The UHP terranes diamonds show much weaker CL; few luminescent stones display CL peaks at 395, 498, 528 nm and a broad band at 580-668 nm. In contrast, most common diamonds found in unmetamorphosed rocks, i.e. octahedrally grown Type IaAB stones, luminescence blue emitting light at ~415-440 nm and 480-490 nm. There is a noticeable difference between cathodoluminescence of these diamonds and diamonds in metamorphic rocks. The studied diamonds that experienced metamorphism show a shift of CL emission to longer wavelengths (above 520 nm) and to green, yellow and red CL colours. Photoluminescence has the high resolution necessary to assign luminescence to specific optical centers of diamond. Diamonds in metamorphic rocks contain H3 (pairs of substitutional nitrogen atoms separated by a vacancy) and NVo optical centers (neutrally charged complexes of a vacancy and a single nitrogen). We ascribe the effect of metamorphism on the diamond CL to low-T, low-P deformation that creates lattice dislocations and vacancies. These combine with substitutional N to make and enhance optical centers. The metamorphism-induced CL anneals when diamonds are stored at high-T mantle conditions, as the mobility of dislocations at T>750oC quenches the luminescence. Indeed, all studied diamonds that displayed unusual green, yellow and red CL were found in low and medium grade metamorphic rocks, i.e. Wawa greenschists (T<350oC and P< 3 kb) and Kokchetav and Erzgebirge UHP terranes retrograded in the amphibolite facies (T<750oC, P<14 kb) Our study suggest that a low abundance of octahedrally grown Type IaAB diamonds with blue CL colours among detrital diamonds may indicate that the stones may have once been a part of a low- or medium-grade metamorphic terrane. The CL characteristics superimposed by metamorphism could survive through billions of years of the geological history if not annealed by a high -T process. The discovered record of metamorphism in the diamond crystal lattice provides an opportunity for a better reconstruction of the crustal history and provenance studies of diamond.

Unliganded Thyroid Hormone Receptor Regulates Metamorphic Timing via the Recruitment of Histone Deacetylase Complexes

PubMed Central

2014-01-01

Anuran metamorphosis involves a complex series of tissue transformations that change an aquatic tadpole to a terrestrial frog and resembles the postembryonic perinatal period in mammals. Thyroid hormone (TH) plays a causative role in amphibian metamorphosis and its effect is mediated by TH receptors (TRs). Molecular analyses during Xenopus development have shown that unliganded TR recruits histone deacetylase (HDAC)-containing N-CoR/SMRT complexes and causes histone deacetylation at target genes while liganded TR leads to increased histone acetylations and altered histone methylations at target genes. Transgenic studies involving mutant TR-cofactors have shown that corepressor recruitment by unliganded TR is required to ensure proper timing of the onset of metamorphosis while coactivator levels influence the rate of metamorphic progression. In addition, a number of factors that can influence cellular free TH levels appear to contribute the timing of metamorphic transformations of different organs by regulating the levels of unliganded vs. liganded TR in an organ-specific manner. Thus, the recruitment of HDAC-containing corepressor complexes by unliganded TR likely controls both the timing of the initiation of metamorphosis and the temporal regulation of organ-specific transformations. Similar mechanisms likely mediate TR function in mammals as the maturation of many organs during postembryonic development is dependent upon TH and resembles organ metamorphosis in amphibians. PMID:23962846

The magmatism and metamorphism at the Malayer area, Western Iran

NASA Astrophysics Data System (ADS)

Ahadnejad, V.; Valizadeh, M. V.; Esmaeily, D.

2009-04-01

The Malayer area is located in the NW-SE aligned Sanandaj-Sirjan metamorphic belt, western Iran and consists mainly of Mesozoic schists so-called Hamadan Phyllites, Jurassic to Tertiary intrusive rocks and related contact metamorphic aureoles, aplites and pegmatites. The Sanandj-Sirjan Zone is produced by oblique collisional event between Arabian plate and Central Iran microcontinent. Highest level of regional metamorphism in the area is greenschist facies and injection of felsic magmas is caused contact metamorphism. Magmatism is consist of a general northwest trend large felsic to intermediate intrusive bodies. The main trend of structural features i.e. faults, fractures and other structural features is NW-SE. The Malayer granitoid complex is ellipsoid in shape and has NW-SE foliation especially at the corners of the intrusions. Petrography of the magmatic rocks revealed recrystallization of quartz and feldspars, bending of biotite, and aligment of minerals paralle to the main trend of magmatic and metamorphic country rocks. These indicated that intrusion of felsic magma is coincide to the regional metamorphism and is syn-tectoinc. Non-extensive contact metamorphism aureoles and rareness of pegmatite and aplite in the area are interpreted as injection of felsic magmas into the high-strain metamorphic zone. The regional metamorphic rocks mainly consist of meta-sandstone, slate, phyllite, schist. These gray to dark metasedimentary rocks are consist of quartz, muscovite, turmaline, epidote, biotite and chlorite. Sheeted minerals form extended schistosity and study of porphyroblast-matrix relationships shows that injection of granitic magma into the country rocks is syn to post-tectonic. Syn-tectonic indicating porphyroblast growth synchronous with the development of the external fabric. The thermal contact area of the granite can be observed in the contact margin of granite and regional metamorphic rocks, where it produced hornfelses, andalusit-garnet schists and local feldspatisation. Hornfels has surrounded the Malayer intrusive body in its southern, eastern and to some extent northeastern parts. It shows a rather sharp contact with the granodiorite. According to field and microscopic investigations, an original clay-sandstone has been converted into hornfels due to contact metamorphism. Some small highly altered granitic patches are seen in the hornfels unit, especially close to its contact with the Malayer intrusive body.

Isotope and chemical age of the Greater Caucasus basement metamorphic rocks

NASA Astrophysics Data System (ADS)

Konilov, A. N.; Somin, M. L.; Mukhanova, A. A.

2009-04-01

It is widely accepted that metamorphic basement of the Greater Caucasus is essentially Proterozoic [i.e. Gamkrelidze & Shengelia, 2005 ]. New results of geochronological study, mainly on magmatic zircon, contradict this opinion [Somin, 2007; Somin et al., 2007a, b, c and references therein]. To precise age of metamorphism we tried to apply CHIME method on monazite [Suzuki, Adachi, 1991]. The facility consists of Tescan SEM VEGA II xmu equipped with EDS Energy 400 and WDS Wave 500 from Oxford Instruments. This system and analytical protocol for monazite analysis are close to described by Slagstad [2006]. Samples of three metamorphic units were used with purpose to investigate their PT conditions and chemical composition of accessory monazite, xenotime and zircon. In the Blyb Complex Ky-bearing St-Grt-Bt schist was studied. Temperature calculated using Grt-St and Grt-Bt thermometers are 550-600 oC at 10 kb. Because xenotime absence and very low Y2O3 content in monazite, temperature determination on Mnz thermometer was impossible. Isochron chemical age of monazite is 288±24 Ma. In the Gondary Complex the Sil-bearing Grt-Bt gneiss was studied. Temperature calculated using Grt-Bt thermometer and Grt-Pl-Sil-Qtz geobarometer correspond to 610 oC at 4 kb. Monazite thermometer [Pyle et al., 2001] indicates temperature range 533-640 oC for three samples. Monazite chemical age is 303±31 Ma, zircon of leucosome yields SHRIMP age 321-288 Ma. In the Makera Complex the And-Bt-Ms and Grt-Bt-Ms metapelites were examinated. Temperature calculated using Grt-Bt thermometer and Grt-Pl-And-Qtz geobarometer correspond to 500 oC at 2,5 kb. Monazite thermometer indicates average temperatures 293-433-447 oC. Two isochrones correspond to 239±28 Ma and 282±19 Ma. Our results of monazite dating are close to the U-Pb zircon data although not similar being some younger. Therefore conclusion on Precambrian metamorphic events in the studied complexes of the Greater Caucasus is erroneous. These complexes independently of baric type seem to be formed roughly synchronously during Variscan epoch. References: Gamkrelidze I.P., Shengelia D.M. ( 2005).The Precambrian-Paleozoic Regional Metamorphism, Granitoid Magmatism, and Geodynamics of the Caucasus. M: Nauchnyi Mir [in Russian]. Pyle J.M., Frank S. Spear F.S. et al. (2001). Monazite-Xenotime-Garnet Equilibrium in Metapelites and a New Monazite-Garnet Thermometer. Journal of Petrology, , 42, 2083-2107. Slagstad T. (2006).Chemical (U-Th-Pb) dating of monazite: Analytical protocol for a LEO 1450VP scanning electron microscope and examples from Rogaland and Finnmark, Norway. Norges geologiske undersøkelse Bulletin, 446, 11-18. Somin M.L. (2007a). Pre-Alpine basement of the Greater Caucasus: main features. In: Alpine history of the Greater Caucasus (Yu.G. Leonovб Ed.). GEOS. Moscow. P.15-38. Somin M.L., Lepekhina E.N., Konilov A.N. ( 2007b). Age of the High-Temperature Gneiss Core of the Central Caucasus. Doklady Earth Sciences, 415, 690-694. Somin M.L., Levchenkov O.A., Kotov A.B. et al. (2007c). The Paleozoic Age of High-Pressure Metamorphic Rocks in the Dakhov Salient, North-Western Caucasus: Results of U-Pb Geochronological Investigations. Doklady Earth Sciences, 416, 1018-1021. Suzuki K., Adachi M. (1991). Precambrian provenance and Silurian metamorphism of the Tsunosava paragneiss in South Kitakami terrane, northeast Japan, revealed by the chemical Th-U-total Pb isochron ages of monazite, zircon and xenotime. Journal of Geochemistry, 25, 357-376.

Metamorphic records of multiple seismic cycles during subduction

PubMed Central

Hacker, Bradley R.; Seward, Gareth G. E.; Kelley, Chris S.

2018-01-01

Large earthquakes occur in rocks undergoing high-pressure/low-temperature metamorphism during subduction. Rhythmic major-element zoning in garnet is a common product of such metamorphism, and one that must record a fundamental subduction process. We argue that rhythmic major-element zoning in subduction zone garnets from the Franciscan Complex, California, developed in response to growth-dissolution cycles driven by pressure pulses. Using electron probe microanalysis and novel techniques in Raman and synchrotron Fourier transform infrared microspectroscopy, we demonstrate that at least four such pressure pulses, of magnitude 100–350 MPa, occurred over less than 300,000 years. These pressure magnitude and time scale constraints are most consistent with the garnet zoning having resulted from periodic overpressure development-dissipation cycles, related to pore-fluid pressure fluctuations linked to earthquake cycles. This study demonstrates that some metamorphic reactions can track individual earthquake cycles and thereby opens new avenues to the study of seismicity. PMID:29568800

Evaluation of the Orbitrap Mass Spectrometer for the Molecular Fingerprinting Analysis of Natural Dissolved Organic Matter.

PubMed

Hawkes, Jeffrey A; Dittmar, Thorsten; Patriarca, Claudia; Tranvik, Lars; Bergquist, Jonas

2016-08-02

We investigated the application of the LTQ-Orbitrap mass spectrometer (LTQ-Velos Pro, Thermo Fisher) for resolving complex mixtures of natural aquatic dissolved organic matter (DOM) and compared this technique to the more established state-of-the-art technique, Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS, Bruker Daltonics), in terms of the distribution of molecular masses detected and the reproducibility of the results collected. The Orbitrap was capable of excellent reproducibility: Bray-Curtis dissimilarity between duplicate measurements was 2.85 ± 0.42% (mean ± standard deviation). The Orbitrap was also capable of the detection of most major ionizable organic molecules in typical aquatic mixtures, with the exception of most sulfur and phosphorus containing masses. This result signifies that the Orbitrap is an appropriate technique for the investigation of very subtle biogeochemical processing of bulk DOM. The lower costs (purchase and maintenance) and wider availability of Orbitrap mass spectrometers in university departments means that the tools necessary for research into DOM processing at the molecular level should be accessible to a much wider group of scientists than before. The main disadvantage of the technique is that substantially fewer molecular formulas can be resolved from a complex mixture (roughly one third as many), meaning some loss of information. In balance, most biogeochemical studies that aim at molecularly fingerprinting the source of natural DOM could be satisfactorily carried out with Orbitrap mass spectrometry. For more targeted metabolomic studies where individual compounds are traced through natural systems, FTICR-MS remains advantageous.

Application of EEM fluorescence spectroscopy in understanding of the "LIGA" phenomenon in the Bay of Biscay (France)

NASA Astrophysics Data System (ADS)

Parot, Jérémie; Susperregui, Nicolas; Rouaud, Vanessa; Dubois, Laurent; Anglade, Nathalie; Parlanti, Edith

2014-05-01

Marine mucilage is present in all oceans over the world, and in particular in the Mediterranean Sea and in the Pacific Ocean. Surface water warming and hydrodynamic processes can favor the coalescence of marine mucilage, large marine aggregates representing an ephemeral and extreme habitat for biota. DOM is a heterogeneous, complex mixture of compounds, including extracellular polymeric substances (EPS), with wide ranging chemical properties and it is well known to interact with pollutants and to affect their transport and their fate in aquatic environment. The LIGA French research program focuses on tracing colloidal dissolved organic matter (DOM) sources and cycling in the Bay of Biscay (South Western French coast). This ephemeral phenomenon (called "LIGA" in the South West of France) has been observed more than 750 times since 2010. It presents a great ecological impact on marine ecosystems and has been shown to be concomitant with the development of pathogen organisms. A one-year intensive survey of fluorescent DOM was undertaken. From April 2013 until May 2014, water samples were monthly collected from the Adour River (main fresh water inputs) and from 2 sites in the Bay of Biscay at 3 depths of the water column (surface water, at the maximum of chlorophyll-a, and deep water). Moreover, intensified samplings took place from the appearance of the phenomenon twice a week during 4 weeks. UV/visible absorbance and excitation emission matrix (EEM) fluorescence spectroscopy combined with PARAFAC and PCA analyses have been used to characterize colloidal DOM in the Bay of Biscay in order to estimate DOM sources as well as spatial and temporal variability of DOM properties. The preliminary results, obtained for about 70 samples of this survey, have already highlighted spatial and temporal variations of DOM optical properties and a peculiar fluorescent component (exc300nm/em338nm) was detected while the LIGA phenomenon arises. The appearance of this specific fluorescence signal seems to be correlated with high freshwater and terrestrial DOM inputs combined with physical forcing (flows, swell) as well as a rise in temperature and sunshine. This work already allowed us to identify different sources of colloidal DOM in the Bay of Biscay and highlighted a specific fingerprint of the LIGA phenomenon. The combination of EEM fluorescence spectroscopy with PARAFAC and PCA analyses appears thus to be a very powerful tool for the long term monitoring of such a phenomenon and would be very useful for a better understanding of the biogeochemical processes in marine environments and of the marine colloidal DOM ecodynamics.

Molecular formulae of marine and terrigenous dissolved organic matter detected by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

NASA Astrophysics Data System (ADS)

Koch, Boris P.; Witt, Matthias; Engbrodt, Ralph; Dittmar, Thorsten; Kattner, Gerhard

2005-07-01

The chemical structure of refractory marine dissolved organic matter (DOM) is still largely unknown. Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR-MS) was used to resolve the complex mixtures of DOM and provide valuable information on elemental compositions on a molecular scale. We characterized and compared DOM from two sharply contrasting aquatic environments, algal-derived DOM from the Weddell Sea (Antarctica) and terrigenous DOM from pore water of a tropical mangrove area in northern Brazil. Several thousand molecular formulas in the mass range of 300-600 Da were identified and reproduced in element ratio plots. On the basis of molecular elemental composition and double-bond equivalents (DBE) we calculated an average composition for marine DOM. O/C ratios in the marine samples were lower (0.36 ± 0.01) than in the mangrove pore-water sample (0.42). A small proportion of chemical formulas with higher molecular mass in the marine samples were characterized by very low O/C and H/C ratios probably reflecting amphiphilic properties. The average number of unsaturations in the marine samples was surprisingly high (DBE = 9.9; mangrove pore water: DBE = 9.4) most likely due to a significant contribution of carbonyl carbon. There was no significant difference in elemental composition between surface and deep-water DOM in the Weddell Sea. Although there were some molecules with unique marine elemental composition, there was a conspicuous degree of similarity between the terrigenous and algal-derived end members. Approximately one third of the molecular formulas were present in all marine as well as in the mangrove samples. We infer that different forms of microbial degradation ultimately lead to similar structural features that are intrinsically refractory, independent of the source of the organic matter and the environmental conditions where degradation took place.

Paleo- and Neoproterozoic magmatic and tectonometamorphic evolution of the Isla Cristalina de Rivera (Nico Pérez Terrane, Uruguay)

NASA Astrophysics Data System (ADS)

Oyhantçabal, Pedro; Wagner-Eimer, Martin; Wemmer, Klaus; Schulz, Bernhard; Frei, Robert; Siegesmund, Siegfried

2012-10-01

The Isla Cristalina de Rivera crystalline complex in northeastern Uruguay underwent a multistage magmatic and metamorphic evolution. Based on SHRIMP U-Pb zircon, Th-U-Pb monazite (CHIME-EPMA method) and K-Ar age data from key units several events can be recognized: (1) multistage magmatism at 2,171-2,114 Ma, recorded on zircon of the granulitic orthogneisses and their 2,093-2,077 Ma overgrowths; (2) a distinct amphibolite facies metamorphism at ~1,980 Ma, recorded by monazite; (3) greenschist facies reworking and shearing at ca. 606 Ma (monazite and K-Ar on muscovite) along the Rivera Shear Zone, and finally (4) intrusion of the post-tectonic Sobresaliente and Las Flores granites at around 585 Ma. Lithological similarities, geographic proximity and coeval magmatic and metamorphic events indicate a similar tectonometamorphic evolution for the Isla Cristalina de Rivera, the Valentines Block in Uruguay and the Santa María Chico Granulitic Complex in southern Brazil, since at least 2.1 Ga.

Uplifted ophiolitic rocks on Isla Gordon, southernmost Chile: implications for the closure history of the Rocas Verdes marginal basin and the tectonic evolution of the Beagle Channel region

NASA Astrophysics Data System (ADS)

Cunningham, W. D.

1994-04-01

A succession of mafic rocks that includes gabbro, sheeted dikes and deformed pillow basalts has been mapped in detail on Isla Gordon, southernmost Chile and is identified as an upper ophiolitic complex representing the uplifted floor of the Late Jurassic-Early Cretaceous Rocas Verdes marginal basin. The complex was uplifted, deformed, and regionally metamorphosed prior to the intrusion of an undeformed 90 Ma granodiorite that cuts the complex. The complex appears para-autochthonous, is gently tilted to the northeast and is internally sheared by near-vertical foliation zones. No evidence for obduction was observed although the base of the complex is not exposed. The ophiolitic rocks have been regionally metamorphosed to mid-upper greenschist levels. Isla Gordon is bounded by the northwest and southwest arms of the Beagle Channel, two important structural boundaries in the southernmost Andes that are interpreted to have accommodated north-side-up and left-lateral displacements. Directly north of Isla Gordon is the Cordillera Darwin metamorphic complex that exposes the highest grade metamorphic rocks in the Andes south of Peru. On the north coast of Isla Gordon a volcaniclastic turbidite sequence that is interpreted to have been deposited above the mafic floor is metamorphosed to lower greenschist levels in strong metamorphic contrast to amphibolite-grade othogneisses exposed in Cordillera Darwin only 2 km away across the northwest arm of the Beagle Channel. The profound metamorphic break across the northwest arm of the Beagle Channel and the regional northeast tilt of the ophiolitic complex are consistent with the previously proposed hypothesis that Isla Gordon represents the upper plate to an extensional fault that accommodated tectonic unroofing of Cordillera Darwin. However, limited structural evidence for extension was identified in this study to support the model and further work is needed to determine the relative importance of contractional, extensional and strike-slip displacements during the closure of the Rocas Verdes marginal basin and uplift of Cordillera Darwin. The Isla Gordon ophiolitic complex is correlative with other regional occurrences of ophiolitic rocks including the previously studied Tortuga, Sarmiento and Larsen Harbour complexes. The existence of the Isla Gordon ophiolitic complex helps link the known occurrences of the marginal basin floor into a semi-continuous belt that sheds light on the original continuity of the basin.

Timing and Nature of Events Leading to the Formation of the Albion-Raft River-Grouse Creek (ARG) Metamorphic Core complex, Northern Great Basin, W. U.S.

NASA Astrophysics Data System (ADS)

Miller, E. L.; Konstantinou, A.; Sheu, D.; Strickland, A.; Grove, M.

2016-12-01

Interpretations of the geodynamic significance of metamorphic core complexes in the northern Basin and Range are intimately tied to a combination of P-T data, geochronology and mica thermochronology used to infer episodes of deformation and uplift related to syn-shortening gravitational collapse of the crust in the latest Cretaceous-early Cenozoic. The ARG is no exception and we bring new geologic mapping, microstructural analysis, geochronology and 40Ar/39Ar thermochronology to bear on these questions. The petrogenesis of Eocene-Miocene magmas, the structural fabrics and metamorphism developed in wall rocks of plutons and the history of flanking basins outline a three-part Cenozoic story of this complex: Part 1: Mantle-derived heat input into the crust in the Eocene (42-36 Ma), related to Farallon slab removal, produced volcanism, plutonism, but little regional extension. Part 2: Heat input led to increased crustal melting as surface volcanism ceased. Diapiric rise of granite-cored gneiss domes sheathed by high grade, high strain metamorphic fabrics and mylonites took place over a protracted time, 32-25 Ma, stalling at depths > 10 km. Transitions upward from penetrative stretching fabrics to brittle crust were complex damage zones of multiply deformed and faulted Paleozoic strata overlain by a more intact 7-8 km thick section of Late Paleozoic and Triassic. Extension was localized and no sedimentary basins formed during this time. Part 3: Metamorphic and igneous rocks were brought to near surface conditions during Miocene extension, between 14-8 Ma ago. Structures accommodating E-W extension are high-angle, rotational normal faults that currently bound both sides of the ARG complex with linked sedimentary basins in their hanging wall. New 40Ar/39Ar data show that country rocks near the Oligocene Almo pluton share the pluton's cooling history. Further from the pluton, where pre-Oligocene fabrics are variably preserved, white mica total gas and plateau ages increase up structural section. Ages in the 40-50 Ma range are likely the result of incomplete argon loss from Mesozoic (Jurassic and or Cretaceous?) micas in the Oligocene and/or partial retention zone residence prior to final Miocene uplift rather than the result of proposed latest Cretaceous-early Cenozoic tectonic or deformational events.

The grand tour of the Ruby-East Humboldt metamorphic core complex, northeastern Nevada: Part 1 - Introduction & road log

USGS Publications Warehouse

Snoke, A.W.; Howard, K.A.; McGrew, A.J.; Burton, B.R.; Barnes, C.G.; Peters, M.T.; Wright, J.E.

1997-01-01

The purpose of this geological excursion is to provide an overview of the multiphase developmental history of the Ruby Mountains and East Humboldt Range, northeastern Nevada. Although these mountain ranges are commonly cited as a classic example of a Cordilleran metamorphic core complex developed through large-magnitude, mid-Tertiary crustal extension, a preceding polyphase Mesozoic contractional history is also well preserved in the ranges. An early phase of this history involved Late Jurassic two-mica granitic magmatism, high-temperature but relatively low-pressure metamorphism, and polyphase deformation in the central Ruby Mountains. In the northern Ruby Mountains and East Humboldt Range, a Late Cretaceous history of crustal shortening, metamorphism, and magmatism is manifested by fold-nappes (involving Archean basement rocks in the northern East Humboldt Range), widespread migmatization, injection of monzogranitic and leucogranitic magmas, all coupled with sillimanite-grade metamorphism. Following Late Cretaceous contraction, a protracted extensional deformation partially overprinted these areas during the Cenozoic. This extensional history may have begun as early as the Late Cretaceous or as late as the mid-Eocene. Late Eocene and Oligocene magmatism occurred at various levels in the crust yielding mafic to felsic orthogneisses in the deep crust, a composite granitic pluton in the upper crust, and volcanic rocks at the surface. Movement along a west-rooted, extensional shear zone in the Oligocene and early Miocene led to core-complex exhumation. The shear zone produced mylonitic rocks about 1 km thick at deep crustal levels, and an overprint of brittle detachment faulting at shallower levels as unroofing proceeded. Megabreccias and other synextensional sedimentary deposits are locally preserved in a tilted, upper Eocene through Miocene stratigraphic sequence. Neogene magmatism included the emplacement of basalt dikes and eruption of rhyolitic rocks. Subsequent Basin and Range normal faulting, as young as Holocene, records continued tectonic extension.

Joint Inversion of Geochemical Data and Geophysical Logs for Lithology Identification in CCSD Main Hole

NASA Astrophysics Data System (ADS)

Deng, Chengxiang; Pan, Heping; Luo, Miao

2017-12-01

The Chinese Continental Scientific Drilling (CCSD) main hole is located in the Sulu ultrahigh-pressure metamorphic (UHPM) belt, providing significant opportunities for studying the metamorphic strata structure, kinetics process and tectonic evolution. Lithology identification is the primary and crucial stage for above geoscientific researches. To release the burden of log analyst and improve the efficiency of lithology interpretation, many algorithms have been developed to automate the process of lithology prediction. While traditional statistical techniques, such as discriminant analysis and K-nearest neighbors classifier, are incompetent in extracting nonlinear features of metamorphic rocks from complex geophysical log data; artificial intelligence algorithms are capable of solving nonlinear problems, but most of the algorithms suffer from tuning parameters to be global optimum to establish model rather than local optimum, and also encounter challenges in making the balance between training accuracy and generalization ability. Optimization methods have been applied extensively in the inversion of reservoir parameters of sedimentary formations using well logs. However, it is difficult to obtain accurate solution from the logging response equations of optimization method because of the strong overlapping of nonstationary log signals when applied in metamorphic formations. As oxide contents of each kinds of metamorphic rocks are relatively less overlapping, this study explores an approach, set in a metamorphic formation model and using the Broyden Fletcher Goldfarb Shanno (BFGS) optimization algorithm to identify lithology from oxide data. We first incorporate 11 geophysical logs and lab-collected geochemical data of 47 core samples to construct oxide profile of CCSD main hole by using backwards stepwise multiple regression method, which eliminates irrelevant input logs step by step for higher statistical significance and accuracy. Then we establish oxide response equations in accordance with the metamorphic formation model and employ BFGS algorithm to minimize the objective function. Finally, we identify lithology according to the composition content which accounts for the largest proportion. The results show that lithology identified by the method of this paper is consistent with core description. Moreover, this method demonstrates the benefits of using oxide content as an adhesive to connect logging data with lithology, can make the metamorphic formation model more understandable and accurate, and avoid selecting complex formation model and building nonlinear logging response equations.

Experimental insights into the importance of aquatic bacterial community composition to the degradation of dissolved organic matter

PubMed Central

Logue, Jürg B; Stedmon, Colin A; Kellerman, Anne M; Nielsen, Nikoline J; Andersson, Anders F; Laudon, Hjalmar; Lindström, Eva S; Kritzberg, Emma S

2016-01-01

Bacteria play a central role in the cycling of carbon, yet our understanding of the relationship between the taxonomic composition and the degradation of dissolved organic matter (DOM) is still poor. In this experimental study, we were able to demonstrate a direct link between community composition and ecosystem functioning in that differently structured aquatic bacterial communities differed in their degradation of terrestrially derived DOM. Although the same amount of carbon was processed, both the temporal pattern of degradation and the compounds degraded differed among communities. We, moreover, uncovered that low-molecular-weight carbon was available to all communities for utilisation, whereas the ability to degrade carbon of greater molecular weight was a trait less widely distributed. Finally, whereas the degradation of either low- or high-molecular-weight carbon was not restricted to a single phylogenetic clade, our results illustrate that bacterial taxa of similar phylogenetic classification differed substantially in their association with the degradation of DOM compounds. Applying techniques that capture the diversity and complexity of both bacterial communities and DOM, our study provides new insight into how the structure of bacterial communities may affect processes of biogeochemical significance. PMID:26296065

Chemodiversity of dissolved organic matter in the Amazon Basin

NASA Astrophysics Data System (ADS)

Gonsior, Michael; Valle, Juliana; Schmitt-Kopplin, Philippe; Hertkorn, Norbert; Bastviken, David; Luek, Jenna; Harir, Mourad; Bastos, Wanderley; Enrich-Prast, Alex

2016-07-01

Regions in the Amazon Basin have been associated with specific biogeochemical processes, but a detailed chemical classification of the abundant and ubiquitous dissolved organic matter (DOM), beyond specific indicator compounds and bulk measurements, has not yet been established. We sampled water from different locations in the Negro, Madeira/Jamari and Tapajós River areas to characterize the molecular DOM composition and distribution. Ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) combined with excitation emission matrix (EEM) fluorescence spectroscopy and parallel factor analysis (PARAFAC) revealed a large proportion of ubiquitous DOM but also unique area-specific molecular signatures. Unique to the DOM of the Rio Negro area was the large abundance of high molecular weight, diverse hydrogen-deficient and highly oxidized molecular ions deviating from known lignin or tannin compositions, indicating substantial oxidative processing of these ultimately plant-derived polyphenols indicative of these black waters. In contrast, unique signatures in the Madeira/Jamari area were defined by presumably labile sulfur- and nitrogen-containing molecules in this white water river system. Waters from the Tapajós main stem did not show any substantial unique molecular signatures relative to those present in the Rio Madeira and Rio Negro, which implied a lower organic molecular complexity in this clear water tributary, even after mixing with the main stem of the Amazon River. Beside ubiquitous DOM at average H / C and O / C elemental ratios, a distinct and significant unique DOM pool prevailed in the black, white and clear water areas that were also highly correlated with EEM-PARAFAC components and define the frameworks for primary production and other aspects of aquatic life.

Provenance and metamorphic PT conditions of Cryogenian-Ediacaran metasediments from the Kid metamorphic complex, Sinai, NE Arabian-Nubian Shield: Insights from detrital zircon geochemistry and mineral chemistry

NASA Astrophysics Data System (ADS)

El-Bialy, Mohammed Z.; Ali, Kamal A.; Abu El-Enen, Mahrous M.; Ahmed, Ahmed H.

2015-12-01

The Malhaq and Um Zariq formations occupy the northern part of the Neoproterozoic Kid metamorphic complex of SE Sinai, NE Arabian-Nubian Shield. This study presents new mineral chemistry data and LA-ICP-MS analyses of the trace element concentrations on zircons separated from metapelites from these formations. The detrital zircons of Um Zariq Formation are more enriched in ΣREE, whereas Malhaq Formation zircons are markedly HREE-enriched with strongly fractionated HREE patterns. The quite differences in the overall slope and size of the Eu and Ce anomalies between REE patterns of the two zircon suites provide a robust indication of different sources. The Ti-in-zircon thermometer has revealed that the zircons separated from Malhaq Formation were crystallized within the 916-1018 °C range, while those from Um Zariq Formation exhibit higher range of crystallization temperatures (1084-1154 °C). The detrital zircons of Malhaq Formation were derived mainly from mafic source rocks (basalt and dolerite), whereas Um Zariq Formation zircons have varied and more evolved parent rocks. Most of the investigated zircons from both formations are concluded to be unaltered magmatic that were lately crystallized from a high LREE/HREE melt. All the studied detrital zircon grains show typical trace elements features of crustal-derived zircons. All of the Um Zariq Formation and most of Malhaq Formation detrital zircons are geochemically discriminated as continental zircons. Both formation metapelites record similar, overlapping peak metamorphic temperatures (537-602 °C and 550-579 °C, respectively), and pressures (3.83-4.93 kbar and 3.69-4.07 kbar, respectively). The geothermal gradient, at the peak metamorphic conditions, was quite high (37-41 °C/km) corresponding to metamorphism at burial depth of 14-16 km. The peak regional metamorphism of Um Zariq and Malhaq formations is concluded to be generated during extensional regime and thinning of the lithosphere in an island arc setting with heat flow from the underlying arc granitoids.

Preliminary geologic map of the Winchester 7.5' quadrangle, Riverside County, California

USGS Publications Warehouse

Morton, Douglas M.

2003-01-01

The Winchester quadrangle is located in the northern part of the Peninsular Ranges Province within the central part of the Perris block, a relatively stable, rectangular in plan view, area located between the Elsinore and San Jacinto fault zones (see location map). The quadrangle is underlain by Cretaceous and older basement rocks. Cretaceous plutonic rocks are part of the composite Peninsular Ranges batholith, which indicates wide variety of granitic rocks, ranging from granite to gabbro. Parts of three major plutonic complexes are within the quadrangle, the Lakeview Mountains pluton, the Domenigoni Valley pluton and the Paloma Valley ring complex. In the northern part of the quadrangle is the southern part of the Lakeview Mountains pluton, a large composite body, most of which lies in the quadrangle to the north. In the center part of the quadrangle is the eastern part of the Domenigoni Valley pluton, which consists of massive biotite-hornblende granodiorite and tonalite; some tonalite in the southern part of the pluton has a relatively pronounced foliation produced by oriented biotite and hornblende. Common to abundant equant-shaped, mafic inclusions occur through out the pluton except in the outermost part where inclusions are absent. The pluton was passively emplaced by piecemeal stoping of a variety of older rocks and the eastern contact is well exposed in the quadrangle. Associated with the Domenigoni Valley pluton is a swarm of latite dikes; the majority of these dikes occur in the Winchester quadrangle, but they extend into the Romoland quadrangle to the west. The latite dikes intrude both the pluton and adjacent metamorphic rocks, most are foliated, and most have a well developed lineation defined by oriented biotite and/or hornblende crystals. Dikes intruding the pluton were emplaced in northwest striking joints; and dikes intruding the metamorphic rocks were emplaced along foliation planes. In the eastern part of the quadrangle a Cretaceous age suture juxtaposes low-metamorphic grade Mesozoic rocks against high-metamorphic grade gneissic-textured Mesozoic rocks. Juxtaposition occurred when the high-metamorphic grade rocks were at upper amphibolite grade temperatures, and produced a steep thermal gradient in the low-metamorphic grade Mesozoic rocks. Age of suturing and attendant metamorphism, based on metamorphic mineral ages, is about 100 Ma (L. Snee, personal communication, 2002). The suture zone appears to vary in thickness, and includes within it a number of metadunite bodies and related rocks. Prebatholithic rocks of Mesozoic age include a wide variety of sedimentary rocks of greenschist or lower metamorphic grade, in the western and central part of the quadrangle, and upper amphibolite grade near the eastern edge of the quadrangle. The metamorphic grade increases from greenschist to upper amphibolite grade over a distance of less than two miles; andalusite and sillimanite isograds are closely spaced near the suture. Metamorphism was Buchan type of relatively high temperature and relatively low pressure (Schwarcz, 1969). Common lithologies of the low metamorphic grade suite include phyllite, lithic greywacke, impure quartzite, meta-arkose, and interlayered quartzite and phyllite. Most of the layering and foliation in the metamorphic rocks is the result of intense structural transposition. Relic bedding appears to be restricted to very local occurrences in hinges of slip folds. The upper amphibolite grade, gneissic-textured Mesozoic rocks consist of sillimanite-biotite gneiss, black amphibolite, and impure quartzite. Anatectic gneiss containing igneous textured segregations of quartz and feldspar is commonly inter leaved with biotite gneiss.

Ultrastructural and geochemical characterization of Archean-Paleoproterozoic graphite particles: implications for recognizing traces of life in highly metamorphosed rocks.

PubMed

Schiffbauer, James D; Yin, Leiming; Bodnar, Robert J; Kaufman, Alan J; Meng, Fanwei; Hu, Jie; Shen, Bing; Yuan, Xunlai; Bao, Huiming; Xiao, Shuhai

2007-08-01

Abundant graphite particles occur in amphibolite-grade quartzite of the Archean-Paleoproterozoic Wutai Metamorphic Complex in the Wutaishan area of North China. Petrographic thin section observations suggest that the graphite particles occur within and between quartzite clasts and are heterogeneous in origin. Using HF maceration techniques, the Wutai graphite particles were extracted for further investigation. Laser Raman spectroscopic analysis of a population of extracted graphite discs indicated that they experienced a maximum metamorphic temperature of 513 +/- 50 degrees C, which is consistent with the metamorphic grade of the host rock and supports their indigenicity. Scanning and transmission electron microscopy revealed that the particles bear morphological features (such as hexagonal sheets of graphite crystals) related to metamorphism and crystal growth, but a small fraction of them (graphite discs) are characterized by a circular morphology, distinct marginal concentric folds, surficial wrinkles, and complex nanostructures. Ion microprobe analysis of individual graphite discs showed that their carbon isotope compositions range from -7.4 per thousand to -35.9 per thousand V-PDB (Vienna Pee Dee Belemnite), with an average of -20.3 per thousand, which is comparable to bulk analysis of extracted carbonaceous material. The range of their size, ultrastructures, and isotopic signatures suggests that the morphology and geochemistry of the Wutai graphite discs were overprinted by metamorphism and their ultimate carbon source probably had diverse origins that included abiotic processes. We considered both biotic and abiotic origins of the carbon source and graphite disc morphologies and cannot falsify the possibility that some circular graphite discs characterized by marginal folds and surficial wrinkles represent deflated, compressed, and subsequently graphitized organic-walled vesicles. Together with reports by other authors of acanthomorphic acritarchs from greenschist-amphibolite-grade metamorphic rocks, this study suggests that it is worthwhile to examine carbonaceous materials preserved in highly metamorphosed rocks for possible evidence of ancient life.

Multi-scale characterization of pore evolution in a combustion metamorphic complex, Hatrurim basin, Israel: Combining (ultra) small-angle neutron scattering and image analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Hsiu-Wen; Anovitz, Lawrence; Burg, Avihu

Backscattered scanning electron micrograph and ultra small- and small-angle neutron scattering data have been combined to provide statistically meaningful data on the pore/grain structure and pore evolution of combustion metamorphic complexes from the Hatrurim basin, Israel. Three processes, anti-sintering roughening, alteration of protolith (dehydration, decarbonation, and oxidation) and crystallization of high-temperature minerals, occurred simultaneously, leading to significant changes in observed pore/grain structures. Pore structures in the protoliths, and in lowand high-grade metamorphic rocks show surface (Ds) and mass (Dm) pore fractal geometries with gradual increases in both Ds and Dm values as a function of metamorphic grade. This suggests thatmore » increases in pore volume and formation of less branching pore networks are accompanied by a roughening of pore/grain interfaces. Additionally, pore evolution during combustion metamorphism is also characterized by reduced contributions from small-scale pores to the cumulative porosity in the high-grade rocks. At high temperatures, small-scale pores may be preferentially closed by the formation of high-temperature minerals, producing a rougher morphology with increasing temperature. Alternatively, large-scale pores may develop at the expense of small-scale pores. These observations (pore fractal geometry and cumulative porosity) indicate that the evolution of pore/grain structures is correlated with the growth of high-temperature phases and is a consequence of the energy balance between pore/grain surface energy and energy arising from heterogeneous phase contacts. The apparent pore volume density further suggests that the localized time/temperature development of the high-grade Hatrurim rocks is not simply an extension of that of the low-grade rocks. The former likely represents the "hot spots (burning foci)" in the overall metamorphic terrain while the latter may represent contact aureoles.« less

A global carbon assimilation system based on a dual optimization method

NASA Astrophysics Data System (ADS)

Zheng, H.; Li, Y.; Chen, J. M.; Wang, T.; Huang, Q.; Huang, W. X.; Wang, L. H.; Li, S. M.; Yuan, W. P.; Zheng, X.; Zhang, S. P.; Chen, Z. Q.; Jiang, F.

2015-02-01

Ecological models are effective tools for simulating the distribution of global carbon sources and sinks. However, these models often suffer from substantial biases due to inaccurate simulations of complex ecological processes. We introduce a set of scaling factors (parameters) to an ecological model on the basis of plant functional type (PFT) and latitudes. A global carbon assimilation system (GCAS-DOM) is developed by employing a dual optimization method (DOM) to invert the time-dependent ecological model parameter state and the net carbon flux state simultaneously. We use GCAS-DOM to estimate the global distribution of the CO2 flux on 1° × 1° grid cells for the period from 2001 to 2007. Results show that land and ocean absorb -3.63 ± 0.50 and -1.82 ± 0.16 Pg C yr-1, respectively. North America, Europe and China contribute -0.98 ± 0.15, -0.42 ± 0.08 and -0.20 ± 0.29 Pg C yr-1, respectively. The uncertainties in the flux after optimization by GCAS-DOM have been remarkably reduced by more than 60%. Through parameter optimization, GCAS-DOM can provide improved estimates of the carbon flux for each PFT. Coniferous forest (-0.97 ± 0.27 Pg C yr-1) is the largest contributor to the global carbon sink. Fluxes of once-dominant deciduous forest generated by the Boreal Ecosystems Productivity Simulator (BEPS) are reduced to -0.78 ± 0.23 Pg C yr-1, the third largest carbon sink.

Reactivity and mobilization of permafrost-derived organic matter along the Lena River Delta - Laptev Sea transition

NASA Astrophysics Data System (ADS)

Koch, Boris P.; Dubinenkov, Ivan; Flerus, Ruth; Schmitt-Kopplin, Philippe; Kattner, Gerhard

2015-04-01

The impact of global warming on organic carbon budgets in permafrost systems are not well constrained. Changes in organic carbon fluxes caused by permafrost thaw depend on microbial activity, coastal erosion, mobilization of organic matter by increased porewater fluxes, and the inherent chemical stability of organic matter in permafrost soils. Here we aim at the identification and molecular characterization of active and inactive dissolved organic matter (DOM) components within the river-ocean transition. We studied four transects in the coastal Laptev Sea characterized by steep physico-chemical gradients. Molecular information on solid-phase extracted DOM was derived from ultrahigh resolution mass spectrometry. Changes of the chemical composition with salinity were used as a measure for DOM reactivity. Although changes of dissolved organic carbon (DOC) in the estuary suggested conservative mixing, only 27% of the identified molecular formulas behaved conservatively, 32% were moderately affected, and 41% were actively involved in estuarine processes. The molecular complexity in the DOM samples increased with growing marine influence and the average elemental composition (i.e. relative contribution of organic nitrogen and oxygen compounds) changed significantly with increasing salinity. These chemical changes were consistent with the results of a 20-day microbial incubation experiment, during which more than half of the permafrost-derived DOC was mineralized. We conclude that, although the DOC gradient in the estuary suggests conservative behavior, terrestrial DOM is substantially affected by estuarine processes which in turn also impact organic carbon budgets in the Lena Delta.

Structure of a preternary complex involving a prokaryotic NHEJ DNA polymerase.

PubMed

Brissett, Nigel C; Martin, Maria J; Pitcher, Robert S; Bianchi, Julie; Juarez, Raquel; Green, Andrew J; Fox, Gavin C; Blanco, Luis; Doherty, Aidan J

2011-01-21

In many prokaryotes, a specific DNA primase/polymerase (PolDom) is required for nonhomologous end joining (NHEJ) repair of DNA double-strand breaks (DSBs). Here, we report the crystal structure of a catalytically active conformation of Mycobacterium tuberculosis PolDom, consisting of a polymerase bound to a DNA end with a 3' overhang, two metal ions, and an incoming nucleotide but, significantly, lacking a primer strand. This structure represents a polymerase:DNA complex in a preternary intermediate state. This polymerase complex occurs in solution, stabilizing the enzyme on DNA ends and promoting nucleotide extension of short incoming termini. We also demonstrate that the invariant Arg(220), contained in a conserved loop (loop 2), plays an essential role in catalysis by regulating binding of a second metal ion in the active site. We propose that this NHEJ intermediate facilitates extension reactions involving critically short or noncomplementary DNA ends, thus promoting break repair and minimizing sequence loss during DSB repair. Copyright © 2011 Elsevier Inc. All rights reserved.

Zircon U-Pb dating, Hf analysis from the Horoman perdiotite -age constraint for lithospheric process, and tectonic juxtaposition of collision root zone-

NASA Astrophysics Data System (ADS)

Okamoto, K.; Yi, K.; Wang, K. L.; Chung, S. L.

2017-12-01

Hidaka metamorphic belt, Hokkaido, Japan is known as youngest arc-arc collision in the world. It ncludes the youngest granulite and the Horoman peridotite complex in the highest grade zone. Age of these rocks have been determined by various methods (K-Ar, U-Pb, Rb-Sr). However, the age of Horoman peridotite complex has not been determined yet. Only Yoshikawa et al 1993) reported the cooling age of the complex as 23 Ma according to whole rock Rb-Sr isochron. This study has performed U-Pb dating of zircons from the Horoman peridotite, and from the paragneiss surrounding the peridotite complex in order to determine the intrusive age of the Horoman peridotite complex into the lower crustal conditions. Several zircon grains were separated from the peridotite. All zircons are homogeneous exhibiting different age group; 267-278 Ma, 33-40 Ma and 18-20 Ma. Hf isotope analysis indicates that the 267-278 Ma is juvenile age and other two are recycled. As a result of this measurement, rims of the zircons from the gneisses show that 238U-206Pb ages are 20 Ma and detrital cores are ranging from 580-510 Ma, 60-50 Ma, 46-40 Ma and 27 Ma. The rim ages are from the gneiss suffered amphibolite facies and granulite faices, and there is a consistancy with zircon rim ages (19 Ma) from the granulite (Kemp et al 2007, Usuki et al 2006 and so on). That is, granulite faices metamorphism was coeval to regional metamorphism in the lower crust at 20 Ma. The zircon ages from the peridotite was probably related to local hydration related to precipitation of phlogopite at 20 Ma, I type magma infiltration at 40 Ma and lithosphere formation at 270 Ma. It is considered that the Horoman peridotite complex was part of the lithosphere at 270 Ma, and the joined as subarc mantle prior to I type magma activity at 40 Ma, aud suffered local hydration and regional metamorphism at 20 Ma. Ref. Kemp, A.I.S., et al., 2007, Geology, 35, 807-810; Usuki, T. et al, 2006, Island Arc, 14, 503-516.

New Rb-Sr mineral ages temporally link plume events with accretion at the margin of Gondwana

USGS Publications Warehouse

Flowerdew, M.J.; Daly, J.S.; Riley, T.R.

2007-01-01

Five of six Rb-Sr muscovite mineral isochron ages from the Scotia Metamorphic Complex of the South Orkney Islands, West Antarctica, average 190 ± 4 Ma. The muscovite ages are interpreted to date foliation-formation and thus also accretion and subduction at the Gondwana margin. Coincident picrite and ferropicrite magmatism, indicative of melts from deep-seated depleted mantle, permits a causative link between accretion and the arrival of the Karoo – Ferrar – Chon Aike mantle plume in the Early Jurassic. Three biotite Rb-Sr mineral isochron ages are consistently younger and average 176 ± 5 Ma. The biotite ages may record post-metamorphic cooling or more likely retrogressive metamorphic effects during uplift.

Metamorphic conditions and CHIME monazite ages of Late Eocene to Late Oligocene high-temperature Mogok metamorphic rocks in central Myanmar

NASA Astrophysics Data System (ADS)

Maw Maw Win; Enami, Masaki; Kato, Takenori

2016-03-01

The high temperature (T)/pressure (P) regional Mogok metamorphic belt is situated in central Myanmar, and is mainly composed of pelitic gneisses, amphibolites, marbles, and calc-silicate rocks. The garnet-biotite-plagioclase-sillimanite-quartz assemblage and its partial system suggest equilibrium P/T conditions of 0.6-1.0 GPa/780-850 °C for the peak metamorphic stage, and 0.3-0.5 GPa/600-680 °C for the exhumation and hydration stage. Monazite grains show complex compositional zoning consisting of three segments-I, II, and III. Taking into consideration the monazite zoning and relative misfit curves, the calculated chemical Th-U-total Pb isochron method (CHIME) monazite age data (284 spot analyses) indicated four age components: 49.3 ± 2.6-49.9 ± 7.9, 37.8 ± 1.0-38.1 ± 1.7, 28.0 ± 0.8-28.8 ± 1.6, and 23.7 ± 1.3 Ma (2σ level). The ages of the Late Eocene and Late Oligocene epochs were interpreted as the peak metamorphic stage of upper-amphibolite and/or granulite facies and the postdated hydration stage, respectively.

Identifying Early Paleozoic tectonic relations in a region affected by post-Taconian transcurrent faulting, an example from the PA-DE Piedmont

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alcock, J.; Wagner, M.E.; Srogi, L.A.

1993-03-01

Post-Taconian transcurrent faulting in the Appalachian Piedmont presents a significant problem to workers attempting to reconstruct the Early Paleozoic tectonic history. One solution to the problem is to identify blocks that lie between zones of transcurrent faulting and that retain the Early Paleozoic arrangement of litho-tectonic units. The authors propose that a comparison of metamorphic histories of different units can be used to recognize blocks of this type. The Wilmington Complex (WC) arc terrane, the pre-Taconian Laurentian margin rocks (LM) exposed in basement-cored massifs, and the Wissahickon Group metapelites (WS) that lie between them are three litho-tectonic units in themore » PA-DE Piedmont that comprise a block assembled in the Early Paleozoic. Evidence supporting this interpretation includes: (1) Metamorphic and lithologic differences across the WC-WS contact and detailed geologic mapping of the contact that suggest thrusting of the WC onto the WS; (2) A metamorphic gradient in the WS with highest grade, including spinel-cordierite migmatites, adjacent to the WC indicating that peak metamorphism of the WS resulted from heating by the WC; (3) A metamorphic discontinuity at the WS-LM contact, evidence for emplacement of the WS onto the LM after WS peak metamorphism; (4) A correlation of mineral assemblage in the Cockeysville Marble of the LM with distance from the WS indicating that peak metamorphism of the LM occurred after emplacement of the WS; and (5) Early Paleozoic lower intercept zircon ages for the LM that are interpreted to date Taconian regional metamorphism. Analysis of metamorphism and its timing relative to thrusting suggest that the WS was associated with the WC before the WS was emplaced onto the LM during the Taconian. It follows that these units form a block that has not been significantly disrupted by later transcurrent shear.« less

Mesozoic thermal history and timing of structural events for the Yukon-Tanana Upland, east-central Alaska: 40Ar/39Ar data from metamorphic and plutonic rocks

USGS Publications Warehouse

Dusel-Bacon, C.; Lanphere, M.A.; Sharp, W.D.; Layer, P.W.; Hansen, V.L.

2002-01-01

We present new 40Ar/39Ar ages for hornblende, muscovite, and biotite from metamorphic and plutonic rocks from the Yukon-Tanana Upland, Alaska. Integration of our data with published 40Ar/39Ar, kinematic, and metamorphic pressure (P) and temperature (T) data confirms and refines the complex interaction of metamorphism and tectonism proposed for the region. The oldest metamorphic episode(s) postdates Middle Permian magmatism and predates the intrusion of Late Triassic (215-212 Ma) granitoids into the Fortymile River assemblage (Taylor Mountain assemblage of previous papers). In the eastern Eagle quadrangle, rapid and widespread Early Jurassic cooling is indicated by ???188-186 Ma 40Ar/39Ar plateau ages for hornblende from plutons that intrude the Fortymile River assemblage, and for metamorphic minerals from the Fortymile River assemblage and the structurally underlying Nasina assemblage. We interpret these Early Jurassic ages to represent cooling resulting from northwest-directed contraction that emplaced the Fortymile River assemblage onto the Nasina assemblage to the north as well as the Lake George assemblage to the south. This cooling was the final stage of a continuum of subduction-related contraction that produced crustal thickening, intermediate- to high-P metamorphism within both the Fortymile River assemblage and the structurally underlying Lake George assemblage, and Late Triassic and Early Jurassic plutonism in the Fortymile River and Nasina assemblages. Although a few metamorphic samples from the Lake George assemblage yield Jurassic 40Ar/39Ar cooling ages, most yield Early Cretaceous 40Ar/39Ar ages: hornblende ???135-115 Ma, and muscovite and biotite ???110-108 Ma. We interpret the Early Cretaceous metamorphic cooling, in most areas, to have resulted from regional extension and exhumation of the lower plate, previously tectonically thickened during Early Jurassic and older convergence.

Behavioral characterization of 2-O-desmethyl and 5-O-desmethyl metabolites of the phenylethylamine hallucinogen DOM.

PubMed

Eckler, J R; Chang-Fong, J; Rabin, R A; Smith, C; Teitler, M; Glennon, R A; Winter, J C

2003-07-01

The present investigation was undertaken to test the hypothesis that known metabolites of the phenylethylamine hallucinogen 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM) are pharmacologically active. This hypothesis was tested by evaluating the ability of racemic DOM metabolites 2-O-desmethyl DOM (2-DM-DOM) and 5-O-desmethyl DOM (5-DM-DOM) to substitute for the stimulus properties of (+)lysergic acid diethylamide (LSD). The data indicate that both metabolites are active in LSD-trained subjects and are significantly inhibited by the selective 5-HT(2A) receptor antagonist M100907. Full generalization of LSD to both 2-DM-DOM and 5-DM-DOM occurred, and 5-DM-DOM was slightly more potent than 2-DM-DOM. Similarly, 5-DM-DOM had a slightly higher affinity than 2-DM-DOM for both 5-HT(2A) and 5-HT(2C) receptors. Additionally, it was of interest to determine if the formation of active metabolite(s) resulted in a temporal delay associated with maximal stimulus effects of DOM. We postulated that if metabolite formation resulted in the aforementioned delay, direct administration of the metabolites might result in maximally stable stimulus effects at an earlier pretreatment time. This hypothesis was tested by evaluating (1) the time point at which DOM produces the greatest degree of LSD-appropriate responding, (2) the involvement of 5-HT(2A) receptor in the stimulus effects of DOM at various pretreatment times by administration of M100907 and (3) the ability of 2-DM-DOM and 5-DM-DOM to substitute for the stimulus properties of LSD using either 15- or 75-min pretreatment time. The data indicate that (a) the DOM stimulus produces the greatest degree of LSD-appropriate responding at the 75-min time point in comparison with earlier pretreatment times and (b) the stimulus effects of DOM are differentially antagonized by M100907 and this effect is a function of DOM pretreatment time prior to testing. Both 2-DM-DOM and 5-DM-DOM were found to be most active, at all doses tested, using a 75-min versus a 15-min pretreatment time. The present data do not permit unequivocal acceptance or rejection of the hypothesis that active metabolites of (-)-DOM provide a full explanation of the observed discrepancy between brain levels of (-)-DOM and maximal stimulus effects.

Oxygen and hydrogen isotopic composition of the fluid during formation of anthophyllite metaultramafic rocks in the Sysert metamorphic complex, central Urals

NASA Astrophysics Data System (ADS)

Murzin, V. V.

2014-12-01

The oxygen (δ18O) and hydrogen (δD) isotopic composition of H2O-bearing minerals was studied for the ore-bearing amphibole metaultramafic rocks, which are the products of the early regional (435 ± 44 Ma) and late local (260 ± 6 Ma) silicic metasomatose in the Sysert metamorphic complex. The gold-sulfide mineralization of the Karas'evogorskoe deposit and anthophyllite-asbestos bodies of the Tersut deposit are related to the regional and local metasomatose combined with plagiogranitization and potassium granitization, respectively. The H2O-bearing minerals of metasomatites (anthophyllite, tremolite, talc) of the Karas'evogorskoe and Tersut deposits are characterized by heavier δ18O (9.8 to 12.2 and 7.6 to 9.4‰, respectively) and lighter ·D (87 to -91 and -56 to -67‰, respectively) values. The calculated isotopic composition of the fluid in equilibrium with these minerals indicates a heterogeneous source of water for the fluids related to the formation of metasomatites and the metamorphic origin of fluids. During the regional metasomatose, this fluid was a result of equilibrium of the deep fluid with volcanosedimentary rocks enriched in the heavy oxygen isotope. At the local metasomatose, the metamorphic fluid was formed by interaction of magmatic water produced by potassium granitization with ultramafic rocks.

Evidence for multiple metamorphic events in the Adirondack Mountains, N. Y

DOE Office of Scientific and Technical Information (OSTI.GOV)

McLelland, J.; Lochhead, A.; Vyhnal, C.

1988-05-01

Field evidence consisting of: (1) rotated, foliated xenoliths, (2) country rock foliation truncated by isoclinally folded igneous intrusions bearing granulite facies assemblages document one, or more, early dynamothermal event(s) of regional scale and high grade. Early metamorphism resulted in pronounced linear and planar fabric throughout the Adirondacks and preceded the emplacement of the anorthosite-mangerite-charnockite-granite-alaskite (AMCA) suite which contains xenoliths of the metamorphosed rocks. Olivine metagabbros, believed to be approximately contemporaneous with the AMCA-suite, also crosscut and contain xenoliths of, strongly foliated metasediments. These intrusive rocks caused contact metamorphism in the metasediments which locally exhibit both anatectite and restite assemblages. Subsequently,more » this already complex framework underwent three phases of folding, including an early recumbent isoclinical event, and was metamorphosed to granulite facies P,T conditions. The age of the early metamorphism cannot yet be narrowly constrained, but isotopic results suggest that it may be as young as approx. 1200 Ma or older than approx. 1420 Ma. U-Pb zircon ages indicate emplacement of the AMCA-(metagabbro)-suite in the interval 1160-1130 Ma and place the peak of granulite facies metamorphism between 1070-1025 Ma. The anorogenic character of the AMCA-suite, and the occurrence of metadiabase dike swarms within it, are further evidence of the separate nature of the metamorphic events that precede and postdate AMCA emplacement.« less

Spatio-temporal variations of organic matter along the Seine estuary (France)

NASA Astrophysics Data System (ADS)

Thibault, Alexandre; Huguet, Arnaud; Parlanti, Edith; Derenne, Sylvie

2017-04-01

Organic matter (OM) in aquatic systems plays an important role in water quality and biogeochemical processes. It is thus essential to characterize OM, especially in estuaries which are the place of the transport and the reactivity of natural and anthropogenic compounds. However, the characterization of OM in estuaries is complex due to its heterogeneity and variability in addition to specific features of these environments (salinity, turbidity…). Two types of aquatic OM, namely particulate (POM) and dissolved (DOM) are commonly distinguished by filtration. Due to its low concentration in estuaries (few mg/L), DOM has to be concentrated prior to its molecular (or structural) analysis. However, this step also induces the concentration of salts which are predominant (several g/L) in coastal environments. To overcome this issue, DOM has been isolated by a combination of reverse osmosis and electrodialysis. This method is more efficient than classical ones (ultrafiltration, solid phase techniques) in the isolation of representative DOM material. As a result, DOM can be characterized just as POM and sedimentary OM. The aim of this study is to characterize the spatiotemporal variability of DOM, POM and sedimentary OM along the Seine estuary (France) so as to understand its role in the functioning of this ecosystem. To this end, 5 sampling campaigns were performed in the Seine estuary between January 2015 and April 2016, during which large water samples (100 L) and sediment cores (10 cm) were collected. These campaigns covered the whole estuary. The three OM pools were analyzed through (i) elemental and isotopic analyses (Elemental Analysis-isotope ratio Mass Spectrometry, 14C ages) and (ii) structural analyses (13C solid state nuclear magnetic resonance, pyrolysis coupled with gas chromatography and mass spectrometry and ultrahigh resolution mass spectrometry), allowing to obtain both bulk and molecular information. The combination of these chemical characterization and statistical analyses shows that the 2 main factors driving the composition of OM in the Seine estuary are the OM pool (DOM, POM or sedimentary) and its origin (marine vs freshwater) whereas seasonal variations appear less pronounced. Indeed, OM exhibits higher C/N ratio and is richer in aliphatic and alkoxyl carbons than POM and sedimentary OM. The latter share the same elemental and isotopic composition but POM is enriched in aliphatic carbons with respect to sedimentary OM. These results confirm the higher hydrophilic nature of DOM when compared to POM and that the sedimentary OM in the Seine estuary is close to POM. Moreover, the dating of OM shows that DOM and POM are recent (> 1950 AD) contrary to sedimentary OM. When going downstream along the estuary, DOM is depleted in aliphatic carbons and enriched in alkoxyl carbons, the reverse trend being observed for POM. Both are enriched in δ13C.

Paleoproterozoic multistage metamorphic events in Jining metapelitic rocks from the Khondalite Belt in the North China Craton: Evidence from petrology, phase equilibria modelling and U-Pb geochronology

NASA Astrophysics Data System (ADS)

Cai, Jia; Liu, Fulai; Liu, Pinghua

2017-05-01

Metapelitic rocks of the Jining Complex (sillimanite-cordierite-garnet (Sil-Crd-Grt) gneisses, sillimanite-garnet (Sil-Grt) gneisses and quartzofeldspathic rocks) are exposed in the eastern segment of the Khondalite Belt (KB) in the North China Craton (NCC). The Sil-Crd-Grt gneisses have preserved polyphase mineral assemblages and microstructural evidence of anatexis, resulting from biotite dehydration melting. Petrological observations revealed that the Sil-Crd-Grt gneisses contain three metamorphic assemblages: a peak assemblage of garnet porphyroblast and matrix biotite + sillimanite + K-feldspar + plagioclase + quartz + ilmenite + magnetite, a post-peak near-isothermal decompressional assemblage of garnet + cordierite + biotite + sillimanite + K-feldspar + plagioclase + quartz + ilmenite + magnetite, and a decompressional cooling assemblage of garnet + biotite + cordierite + K-feldspar + plagioclase + quartz + ilmenite + magnetite. A clockwise P-T path was defined involving the inferred peak stage followed by post-peak near-isothermal decompression and decompressional cooling stages, with P-T conditions of 790-825 °C and 9-10 kbar, 810-890 °C and 6.0-6.5 kbar, and 780-810 °C and 4.0-5.5 kbar, respectively. Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) U-Pb analyses of the Sil-Crd-Grt gneisses and Sil-Grt gneisses for the detrital and metamorphic zircons yielded a protolith age of ∼2.0 Ga and the late Paleoproterozoic metamorphic age of 1895-1885 Ma. The results reveal that the metapelitic rocks of the Jining Complex underwent continent-continent subduction or collision in the peak metamorphic stage, followed by a post-collisional exhumation event in the post-peak decompressional stage, and a subsequent decompressional cooling stage between the Yinshan and Ordos blocks to form the Paleoproterozoic KB.

Stepwise exhumation of the Triassic Lanling high-pressure metamorphic belt in Central Qiangtang, Tibet: Insights from a coupled study of metamorphism, deformation, and geochronology

NASA Astrophysics Data System (ADS)

Liang, Xiao; Wang, Genhou; Yang, Bo; Ran, Hao; Zheng, Yilong; Du, Jinxue; Li, Lingui

2017-04-01

The E-W trending Central Qiangtang metamorphic belt (CQMB) is correlated to the Triassic orogeny of the Paleo-Tethys Ocean prior to Cenozoic growth of the Tibetan Plateau. The well-exposed Lanling high-pressure, low-temperature (HP-LT) metamorphic complex was chosen to decipher the process by which it was exhumed, which thereby provides insights into the origin of the CQMB and Qiangtang terrane. After a detailed petrological and structural mapping, three distinct N-S-trending metamorphic domains were distinguished. Microscopic observations show that core domain garnet (Grt)-bearing blueschist was exhumed in a heating plus depressurization trajectory after peak eclogitic conditions, which is more evident in syntectonic vein form porphyroblastic garnets with zoning typical of a prograde path. Grt-free blueschist of the mantle domain probably underwent an exhumation path of temperature increasing and dehydration, as evidenced by pervasive epidote veins. The compilation of radiometric results of high-pressure mineral separates in Lanling and Central Qiantang, and reassessments on the published phengite data sets of Lanling using Arrhenius plots allow a two-step exhumation model to be formulated. It is suggested that core domain eclogitic rocks were brought onto mantle domain blueschist facies level starting at 244-230 Ma, with exhumation continuing to 227-223.4 Ma, and subsequently were exhumed together starting at 223-220 Ma, reaching lower greenschist facies conditions generally after 222-217 Ma. These new observations indicate that the CQMB formed as a Triassic autochthonous accretionary complex resulting from the northward subdcution of the Paleo-Tethys Ocean and that HP-LT rocks therein were very probably exhumed in an extensional regime.

The paradox of 5-methoxy-N,N-dimethyltryptamine: an indoleamine hallucinogen that induces stimulus control via 5-HT1A receptors.

PubMed

Winter, J C; Filipink, R A; Timineri, D; Helsley, S E; Rabin, R A

2000-01-01

Stimulus control was established in rats trained to discriminate either 5-methoxy-N,N-dimethyltryptamine (3 mg/kg) or (-)-2,5-dimethoxy-4-methylamphetamine (0.56 mg/kg) from saline. Tests of antagonism of stimulus control were conducted using the 5-HT1A antagonists (+/-)-pindolol and WAY-100635, and the 5-HT2 receptor antagonist pirenperone. In rats trained with 5-MeO-DMT, pindolol and WAY-100635 both produced a significant degree of antagonism of stimulus control, but pirenperone was much less effective. Likewise, the full generalization of 5-MeO-DMT to the selective 5-HT1A agonist [+/-]-8-hydroxy-dipropylaminotetralin was blocked by WAY-100635, but unaffected by pirenperone. In contrast, the partial generalization of 5-MeO-DMT to the 5-HT2 agonist DOM was completely antagonized by pirenperone, but was unaffected by WAY-100635. Similarly, in rats trained with (-)-DOM, pirenperone completely blocked stimulus control, but WAY-100635 was inactive. The results obtained in rats trained with (-)-DOM and tested with 5-MeO-DMT were more complex. Although the intraperitoneal route had been used for both training drugs, a significant degree of generalization of (-)-DOM to 5-MeO-DMT was seen only when the latter drug was administered subcutaneously. Furthermore, when the previously effective dose of pirenperone was given in combination with 5-MeO-DMT (s.c.), complete suppression of responding resulted. However, the combination of pirenperone and WAY-100635 given prior to 5-MeO-DMT restored responding in (-)-DOM-trained rats, and provided evidence of antagonism of the partial substitution of 5-MeO-DMT for (-)-DOM. The present data indicate that 5-MeO-DMT-induced stimulus control is mediated primarily by interactions with 5-HT1A receptors. In addition, however, the present findings suggest that 5-MeO-DMT induces a compound stimulus that includes an element mediated by interactions with a 5-HT2 receptors. The latter component is not essential for 5-MeO-DMT-induced stimulus control, but is revealed in animals tested or trained with a 5-HT2-selective agonist such as (-)-DOM. Based upon the present data, we conclude that 5-MeO-DMT differs from DOM with respect to the serotonergic element that mediates stimulus control in the rat, but that it shares with DOM a functionally significant interaction with 5-HT2 receptors.

Fluorescence spectroscopy for field surveillance of THM formation precursors to increase sustainable drinking water treatment for the water industry

NASA Astrophysics Data System (ADS)

Stutter, Marc; Cooper, Pat; Wyness, Adam; Allan, Richard; Weir, Paul; Frogbrook, Zoe; Haffey, Mark

2017-04-01

Our understanding of the composition and diversity of dissolved organic matter (DOM) in natural waters is improving rapidly with techniques such as fluorescence spectroscopy. For the water industry issues of the reaction of DOM and different processes used to reduce microbial contamination in water for public supply are a pressing concern. A range of processes can be used but the common disinfection by free chlorine can react with DOM to produce a group of substances referred to as disinfection by-products (DBPs) that have been linked to health concerns. Hence, management at water treatment works aims to remove DOM prior to the disinfection reaction or change the treatment method. Both are costly financially and in terms of process chemical, such as coagulents that work variably with different DOM forms. Hence, enabling methods of catchment management, which have long been associated with tackling other forms of pollution (e.g. N, P) through source-pathway-receptor concepts, are options for the water industry where catchment raw water source management is a possible sustainable addition to conventional treatment. This presentation looks at the requirements and ongoing work to inform source water management options using bench-top fluorescence excitation-emission spectroscopy and hand-held sensors to detect DBP precursors, namely trihalomethanes (THMs), in complex multi-source environments. We start by introducing the forms of DOM discernible in the fluorescence excitation-emission matrix, how these have been ascribed to different compounds by previous studies and what wavelengths are available for in-situ detection. We then discuss methodology issues for sample storage and standard materials. Then we draw on results from a national set of Scottish catchments and a small catchment study to evaluate relationships between THM compounds from standard assay and GC-MS detection against spectral DOM surrogates, including catchment hydrochemical and spatial data covariates. This is supported by laboratory batch work on potential synergistic interactions for THM formation in mixtures of DOM types from isolated humic substances and amino-acid compounds; where the latter can provide markers for anthropogenic pollution sources such as wastewater and farm effluents. Finally, we conclude on some of the potential for these techniques for catchment raw source water management. We present a circular-sustainability argument whereby the broad range of DOM combinations detectable by fluorescence techniques allows consideration of catchment C-source markers of potential THM formation resulting from disinfection and of the microbial contaminants necessitating the disinfection treatment.

Singlet oxygen in the coupled photochemical and biochemical oxidation of dissolved organic matter.

PubMed

Cory, Rose M; McNeill, Kristopher; Cotner, James P; Amado, Andre; Purcell, Jeremiah M; Marshall, Alan G

2010-05-15

Dissolved organic matter (DOM) is a significant (>700 Pg) global C pool. Transport of terrestrial DOM to the inland waters and coastal zones represents the largest flux of reduced C from land to water (215 Tg yr(-1)) (Meybeck, M. Am. J. Sci. 1983, 282, 401-450). Oxidation of DOM by interdependent photochemical and biochemical processes largely controls the fate of DOM entering surface waters. Reactive oxygen species (ROS) have been hypothesized to play a significant role in the photooxidation of DOM, because they may oxidize the fraction of DOM that is inaccessible to direct photochemical degradation by sunlight. We followed the effects of photochemically produced singlet oxygen ((1)O(2)) on DOM by mass spectrometry with (18)O-labeled oxygen, to understand how (1)O(2)-mediated transformations of DOM may lead to altered DOM bioavailability. The photochemical oxygen uptake by DOM attributed to (1)O(2) increased with DOM concentration, yet it remained a minority contributor to photochemical oxygen uptake even at very high DOM concentrations. When DOM samples were exposed to (1)O(2)-generating conditions (Rose Bengal and visible light), increases were observed in DOM constituents with higher oxygen content and release of H(2)O(2) was detected. Differential effects of H(2)O(2) and (1)O(2)-treated DOM showed that (1)O(2)-treated DOM led to slower bacterial growth rates relative to unmodified DOM. Results of this study suggested that the net effect of the reactions between singlet oxygen and DOM may be production of partially oxidized substrates with correspondingly lower potential biological energy yield.

UPTAKE OF LIPOPHILIC CADMIUM COMPLEXES BY THREE GREEN ALGAE: INFLUENCE OF HUMIC ACID AND ITS pH DEPENDENCE(1).

PubMed

Boullemant, Amiel; Le Faucheur, Séverine; Fortin, Claude; Campbell, Peter G C

2011-08-01

Cadmium forms neutral, lipophilic CdL2 (0) complexes with diethyldithiocarbamate (L = DDC) and with ethylxanthate (L = XANT). In a synthetic solution and in the absence of natural dissolved organic matter (DOM), for a given total Cd concentration, uptake of these complexes by unicellular algae is much faster than the uptake of the free Cd(2+) cation. The objective of the present study was to determine how this enhanced uptake of the lipophilic CdL2 (0) complexes was affected by the presence of natural DOM (Suwannee River humic acid, SRHA). Experiments were performed with Cd(DDC)2 (0) and Cd(XANT)2 (0) at two pH values (7.0 and 5.5) and with the three chlorophytes [Chlamydomonas reinhardtii P. A. Dang., Pseudokirchneriella subcapitata (Korshikov) Hindák, Chlorella fusca var. vacuolata Shihira et R. W. Krauss]. Short-term uptake (30-40 min) of the CdL2 (0) complexes was followed in the absence and presence of SRHA (6.5 mg C · L(-1) ). Acidification from pH 7.0 to 5.5 decreased CdL2 (0) uptake by the three algae, in the presence or absence of humic acid (HA). The dominant effect of the HA was to decrease Cd uptake, due to its interaction with the CdL2 (0) complexes in solution. However, if uptake of the free CdL2 (0) complexes was compared in the presence and absence of HA, in four of eight cases initial uptake rate constants (ki ) were significantly higher (P < 0.05) in the presence of the HA, suggesting the operation of an interfacial effect of the HA at the algal cell membrane, favoring uptake of CdL2 (0) . Overall, the experimental results suggest that neutral metal complexes will be less bioavailable in natural waters than they are in synthetic laboratory media in the absence of natural DOM. © 2011 Phycological Society of America.

Structural analysis and deformation characteristics of the Yingba metamorphic core complex, northwestern margin of the North China craton, NE Asia

NASA Astrophysics Data System (ADS)

Yin, Congyuan; Zhang, Bo; Han, Bao-Fu; Zhang, Jinjiang; Wang, Yang; Ai, Sheng

2017-01-01

The presence of the Yingba (Yinggete-Bagemaode) metamorphic core complex (MCC) is confirmed near the Sino-Mongolian border in China. We report its structural evolution and the rheological features of ductile shear zones within this complex. Three deformations (Ds, Dm, and Db) since the Late Jurassic are identified. Ds is characterized by ductile structures that resulted from early NW-oriented, low-angle, extensional ductile shearing. Dm is associated with partial melting and magmatic diapirism, which accelerated the formation of the dome-like geometry of the Yingba MCC. Synchronously with or slightly subsequently to Ds and Dm, the Yingba MCC was subjected to brittle, extensional faulting (Db), which was accompanied by the exhumation of the lower crust and the formation of supracrustal basins. The ductile shearing (Ds) developed under greenschist-to amphibolite-facies metamorphic conditions (400-650 °C), as indicated by microstructures in quartz and feldspar, quartz [c] axis fabrics, and two-feldspar geothermometry. The mean kinematic vorticity estimates of 48-62% show a pure shear-preferred flow during Ds. The Yingba MCC provides an excellent sample that recorded an intermediate to high temperature shearing, which also implies the widely extensional regime in northeastern Asia at that time.

Deformation sequences of the Day Nui Con Voi metamorphic belt, northern Vietnam

NASA Astrophysics Data System (ADS)

Yeh, M. W.; Lee, T. Y.; Lo, C. H.; Chung, S. L.; Lan, C. Y.; Lee, J. C.; Lin, T. S.; Lin, Y. J.

2003-04-01

The correlation of structure, microstructure and metamorphic assemblages is of fundamental importance to the understanding of the complex tectonic history and kinematics of the Day Nui Con Voi (DNCV) metamorphic belt in Vietnam along the Ailao Shan-Red River (ASRR) shear zone as it provides constraints on the relative timing of the deformation, kinematics and metamorphism. High-grade metamorphic rocks of amphibolite faces showed consistent deformation sequences of three folding events followed by one brittle deformation through all four cross sections from Lao Cai to Viet Tri indicated the DNCV belt experienced similar deformation condition throughout its length. The first deformation event, D1, produced up-right folds (locally preserved) with sub-vertical, NE-SW striking axial planes with dextral sense of shear probably formed during the early phase of the lowermost Triassic Indosinian orogeny. Followed by this compressional event is a gravitational collapsing event, D2, which is the major deformation and metamorphic event characterized by kyanite grade metamorphism and large scale horizontal folds with NW-SE (320) striking sub-horizontal axial pane showing sinsistral sense of shear most likely formed during the Oligocene-Miocene SE extrusion of Indochina peninsula. The 3rd folding event, D3, is a post-metamorphism doming event with NW-SE (310) striking sub-vertical axial plane that folded/tilted the once sub-horizontal D2 axial planes into shallowly (<30 degrees) NE dipping on the NE limb, and SW dipping on the SW limb possibly due to left-lateral movement of the N-S trending Xian Shui He fault system in Mid-Miocene. The outward decreasing of the metamorphic grade from kyanite to garnet then biotite indicated the D3 occurred post metamorphism. Reactivation of the sub-horizontal D2 fold axial planes showed dextral sense of shear possibly due to Late Miocene-Pliocene right-lateral movement of the ASRR shear zone. This right lateral movement continuously deformed the DNCV with brittle fractures such as joints and normal faults (D4) striking NE-SW to E-W and NW-SE.

Carbon, hydrogen, and oxygen isotope studies of the regional metamorphic complex at Naxos, Greece

USGS Publications Warehouse

Rye, R.O.; Schuiling, R.D.; Rye, D.M.; Jansen, J.B.H.

1976-01-01

At Naxos, Greece, a migmatite dome is surrounded by schists and marbles of decreasing metamorphic grade. Sillimanite, kyanite, biotite, chlorite, and glaucophane zones are recognized at successively greater distances from the migmatite dome. Quartz-muscovite and quartz-biotite oxygen isotope and mineralogie temperatures range from 350 to 700??C. The metamorphic complex can be divided into multiple schist-rich (including migmatites) and marblerich zones. The ??18O values of silicate minerals in migmatite and schist units and quartz segregations in the schist-rich zones decrease with increase in metamorphic grades. The calculated ??18OH2O values of the metamorphic fluids in the schist-rich zones decrease from about 15??? in the lower grades to an average of about 8.5??? in the migmatite. The ??D values of OH-minerals (muscovite, biotite, chlorite, and glaucophane) in the schist-rich zones also decrease with increase in grade. The calculated ??DH2O values for the metamorphic fluid decrease from -5??? in the glaucophane zone to an average of about -70??? in the migmatite. The ??D values of water in fluid inclusions in quartz segregations in the higher grade rocks are consistent with this trend. The??18O values of silicate minerals and quartz segregations in marble-rich zones are usually very large and were controlled by exchange with the adjacent marbles. The ??D values of the OH minerals in some marble-rich zones may reflect the value of water contained in the rocks prior to metamorphism. Detailed data on 20 marble units show systematic variations of ??18O values which depend upon metamorphic grade. Below the 540??C isograd very steep ??18O gradients at the margins and large ??18O values in the interior of the marbles indicate that oxygen isotope exchange with the adjacent schist units was usually limited to the margins of the marbles with more exchange occurring in the stratigraphic bottom than in the top margins. Above the 540??C isograd lower ??18O values occur in the interior of the marble units reflecting a greater degree of recrystallization and the occurrence of Ca-Mg-silicates. Almost all the ??13C values of the marbles are in the range of unaltered marine limestones. Nevertheless, the ??13C values of most marble units show a general correlation with ??18O values. The CO2 H2O mole ratio of fluid inclusions in quartz segregations range from 0.01 to 2. The??13C values of the CO2 range from -8.0 to 3.6??? and indicate that at some localities CO2 in the metamorphic fluid was not in carbon isotopic equilibrium with the marbles. ?? 1976.

Structure and metamorphism of the Franciscan Complex, Mt. Hamilton area, Northern California

USGS Publications Warehouse

Blake, M.C.; Wentworth, C.M.

1999-01-01

Truncation of metamorphic isograds and fold axes within coherent terranes of Franciscan metagraywacke by intervening zones of melange indicate that the melange is tectonic and formed after the subduction-related metamorphism and folding. These relations are expressed in two terranes of blueschist-facies rocks of the Franciscan Complex in the Mt. Hamilton area, northern California-the Jurassic Yolla Bolly terrane and the structurally underlying Cretaceous Burnt Hills terrane. Local preservation in both terranes of basal radiolarian chert and oceanic basalt beneath continent-derived metagraywacke and argillite demonstrates thrust repetition within the coherent terranes, although these relations are scarce near Mt. Hamilton. The metagraywackes range from albite-pumpellyite blueschists to those containing well-crystallized jadeitic pyroxene, and a jadeite-in isograd can be defined in parts of the area. Primary bedding defines locally coherent structural orientations and folds within the metagraywacke units. These units are crosscut by thin zones of tectonic melange containing blocks of high-grade blueschist, serpentinite, and other exotic rocks, and a broader, but otherwise identical melange zone marks the discordant boundary between the two terranes.

K-Ar geochronology of the Survey Pass, Ambler River and Eastern Baird Mountains quadrangles, southwestern Brooks Range, Alaska

USGS Publications Warehouse

Turner, Donald L.; Forbes, R.B.; Mayfield, C.F.

1978-01-01

We report 76 previously unpublished K-Ar mineral ages from 47 metamorphic and igneous rocks in the southwestern Brooks Range. The pattern of radiometric ages is complex, reflecting the complex geologic history of this area. Local and regional radiometric evidence suggests that the southern Brooks Range schist belt has, at least in part, undergone a late Precambrian metamorphism and that the parent sedimentary and igneous rocks for the metamorphic rocks dated as late Precambrian are at least this old (Precambrian Z). This schist terrane experienced a major thermal event in mid-Cretaceous time, causing widespread resetting of nearly all K-Ar mica ages. A series of apparent ages intermediate between late Precambrian and mid-Cretaceous are interpreted as indicating varying amounts of partial argon loss from older rocks during the Cretaceous event. The schist belt is characterized by dominant metasediments and subordinate metabasites and metafelsites. Blueschists occur within the schist belt from the Chandalar quadrangle westward to the Baird Mountains quadrangle, but geologic evidence does not support the existence of a fossil subduction zone.

Toward understanding the role of individual fluorescent components in DOM-metal binding.

PubMed

Wu, Jun; Zhang, Hua; Yao, Qi-Sheng; Shao, Li-Ming; He, Pin-Jing

2012-05-15

Knowledge on the function of individual fractions in dissolved organic matter (DOM) is essential for understanding the impact of DOM on metal speciation and migration. Herein, fluorescence excitation-emission matrix quenching and parallel factor (PARAFAC) analysis were adopted for bulk DOM and chemically isolated fractions from landfill leachate, i.e., humic acids (HA), fulvic acids and hydrophilic (HyI) fraction, to elucidate the role of individual fluorescent components in metal binding (Cu(II) and Cd(II)). Three components were identified by PARAFAC model, including one humic substance (HS)-like, one protein-like and one component highly correlated with the HyI fraction. Among them, the HS-like and protein-like components were responsible for Cu(II) binding, while the protein-like component was the only fraction involved in Cd(II) complexation. It was further identified that the slight quenching effect of HA fraction by Cd(II) was induced by the presence of proteinaceous materials in HA. Fluorescent substances in the HyI fraction of landfill leachate did not play as important a role as HS did. Therefore, it was suggested that the potential risk of aged leachate (more humified) as a carrier of heavy metal should not be overlooked. Copyright © 2012 Elsevier B.V. All rights reserved.

Uncertainty analysis of the nonideal competitive adsorption-donnan model: effects of dissolved organic matter variability on predicted metal speciation in soil solution.

PubMed

Groenenberg, Jan E; Koopmans, Gerwin F; Comans, Rob N J

2010-02-15

Ion binding models such as the nonideal competitive adsorption-Donnan model (NICA-Donnan) and model VI successfully describe laboratory data of proton and metal binding to purified humic substances (HS). In this study model performance was tested in more complex natural systems. The speciation predicted with the NICA-Donnan model and the associated uncertainty were compared with independent measurements in soil solution extracts, including the free metal ion activity and fulvic (FA) and humic acid (HA) fractions of dissolved organic matter (DOM). Potentially important sources of uncertainty are the DOM composition and the variation in binding properties of HS. HS fractions of DOM in soil solution extracts varied between 14 and 63% and consisted mainly of FA. Moreover, binding parameters optimized for individual FA samples show substantial variation. Monte Carlo simulations show that uncertainties in predicted metal speciation, for metals with a high affinity for FA (Cu, Pb), are largely due to the natural variation in binding properties (i.e., the affinity) of FA. Predictions for metals with a lower affinity (Cd) are more prone to uncertainties in the fraction FA in DOM and the maximum site density (i.e., the capacity) of the FA. Based on these findings, suggestions are provided to reduce uncertainties in model predictions.

Evaluating Changes in the Molecular Composition and Optical Properties of Pacific Ocean Dissolved Organic Matter (DOM) caused by Borodeuteride Reduction

NASA Astrophysics Data System (ADS)

Bianca, M.; Blough, N. V.; Del Vecchio, R.; Cartisano, C. M.; Schmitt-Kopplin, P.; Gonsior, M.

2016-02-01

Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR MS) is a powerful tool to obtain detailed molecular information for complex DOM and was combined in this study with optical measurements to determine the molecular fingerprint of Pacific Ocean DOM before and after borodeuteride reduction. Selective chemical reductions, using sodium borodeuteride, has been previously demonstrated to produce unique mass markers of ketone and aldehyde-containing species in ultrahigh resolution mass spectrometry. These functional groups have also been proposed to be responsible for chromophoric dissolved organic matter (CDOM) long wavelength optical properties through charge transfer interactions and their chemical reduction has shown to irreversibly alter the CDOM optical properties. ESI-FT-ICR MS coupled with borodeuteride reduction was thus applied to reference material, Suwannee River Fulvic Acid (SRFA), and CDOM extracts collected from Station ALOHA, in the North Pacific Ocean during December 2014. Results showed distinct differences between samples collected at different depths, indicating that the combination of FT-ICR-MS with borodeuteride reduction is a useful analytical tool to further understand marine DOM molecular composition. When this method is combined with optical measurements, specific insights into the CDOM composition can also be obtained.

Development and application of laser microprobe techniques for oxygen isotope analysis of silicates, and, fluid/rock interaction during and after granulite-facies metamorphism, highland southwestern complex, Sri Lanka

DOE Office of Scientific and Technical Information (OSTI.GOV)

Elsenheimer, D.W.

1992-01-01

The extent of fluid/rock interaction within the crust is a function of crustal depth, with large hydrothermal systems common in the brittle, hydrostatically pressured upper crust, but restricted fluid flow in the lithostatically pressured lower crust. To quantify this fluid/rock interaction, a Nd-YAG/CO[sub 2] laser microprobe system was constructed to analyze oxygen isotope ratios in silicates. Developed protocols produce high precision in [sigma][sup 18]O ([+-]0.2, 1[sigma]) and accuracy comparable to conventional extraction techniques on samples of feldspar and quartz as small as 0.3mg. Analysis of sub-millimeter domains in quartz and feldspar in granite from the Isle of Skye, Scotland, revealsmore » complex intragranular zonation. Contrasting heterogeneous and homogeneous [sigma][sup 18]O zonation patterns are revealed in samples <10m apart. These differences suggest fluid flow and isotopic exchange was highly heterogeneous. It has been proposed that granulite-facies metamorphism in the Highland Southwestern Complex (HSWC), Sri Lanka, resulted from the pervasive influx of CO[sub 2], with the marbles and calc-silicates within the HSWC a proposed fluid source. The petrologic and stable isotopic characteristic of HSWC marbles are inconsistent with extensive decarbonation. Wollastonite calc-silicates occur as deformed bands and as post-metamorphis veins with isotopic compositions that suggest vein fluids that are at least in part magmatic. Post-metamorphic magmatic activity is responsible for the formation of secondary disseminated graphite growth in the HSWC. This graphite has magmatic isotopic compositions and is associated with vein graphite and amphibolite-granulite facies transitions zones. Similar features in Kerela Khondalite Belt, South India, may suggest a common metamorphic history for the two terranes.« less

Mayer Kangri metamorphic complexes in Central Qiangtang (Tibet, western China): implications for the Triassic-early Jurassic tectonics associated with the Paleo-Tethys Ocean

NASA Astrophysics Data System (ADS)

Wang, Yixuan; Liang, Xiao; Wang, Genhou; Yuan, Guoli; Bons, Paul D.

2018-03-01

The Mesozoic orogeny in Central Qiangtang Metamorphic Belt, northern Tibet, provides important insights into the geological evolution of the Paleo-Tethys Ocean. However, the Triassic-early Jurassic tectonics, particularly those associated with the continental collisionstage, remains poorly constrained. Here we present results from geological mapping, structural analysis, P-T data, and Ar-Ar geochronology of the Mayer Kangri metamorphic complex. Our data reveal an E-W-trending, 2 km wide dome-like structure associated with four successive tectonic events during the Middle Triassic and Early Jurassic. Field observations indicate that amphibolite and phengite schist complexes in this complex are separated from the overlying lower greenschist mélange by normal faulting with an evident dextral shearing component. Open antiform-like S2 foliation of the footwall phengite schist truncates the approximately north-dipping structures of the overlying mélange. Microtextures and mineral chemistry of amphibole reveal three stages of growth: Geothermobarometric estimates yield temperatures and pressures of 524 °C and 0.88 GPa for pargasite cores, 386 °C and 0.34 GPa for actinolite mantles, and 404 °C and 0.76 GPa for winchite rims. Peak blueschist metamorphism in the phengite schist occurred at 0.7-1.1 GPa and 400 °C. Our Ar-Ar dating of amphibole reveals rim-ward decreasing in age bands, including 242.4-241.2 Ma, ≥202.6-196.8, and 192.9-189.8 Ma. The results provide evidence for four distinct phases of Mesozoic tectonic evolution in Central Qiangtang: (1) northward oceanic subduction beneath North Qiangtang ( 244-220 Ma); (2) syn-collisional slab-break off (223-202 Ma); (3) early collisional extension driven by buoyant extrusion flow from depth ( 202.6-197 Ma); and (4) post-collision contraction and reburial (195.6-188.7 Ma).

On protolith-, metamorphic overprint, microstructure and rheology of mineral assemblages in orogenic peridotites of the central Scandinavian Caledonides

NASA Astrophysics Data System (ADS)

Gilio, Mattia; Clos, Frediano; Van Roermund, Herman L. M.

2013-04-01

The Scandinavian Caledonides (SC) are a deeply eroded Alpine-type orogenic belt formed by closure of the Iapetus ocean and collision between Baltica and Laurentia (500-380 Ma). The SC consists of a stack of Nappe Complexes (from bottom to top called Lower, Middle, Upper and Uppermost Allochthons) thrusted to the east over the Baltic Shield (Brueckner and Van Roermund, 2004; Gee et al., 2008). Fossil lithospheric mantle fragments, called orogenic peridotites, have been found within the (upper part of) middle, upper and uppermost Allochthons, as well as in the reworked basement gneisses (a.o Western Gneiss Complex (WGC)) along the Norwegian west coast. They occur as isolated lenses that contain diverse mineral parageneses and/or bulk rock compositions. Crustal incorporation of orogenic peridotite is classically interpreted to be the result of plate collisional processes related to orogeny (Brueckner and Medaris, 2000). The WGC and parts of the upper part of the Middle Allochthon (a.o. Seve Nappe Complex (SNC) in N Jämtland/S Västerbotten, central Sweden), are well known for the occurrence of high (HP) and ultrahigh pressure (UHP) metamorphic terranes (of Caledonian age). The (U)HPM evidence clearly demonstrates the deep metamorphic origin of these rocks interpreted to be caused by continental subduction and/or collision. Other metamorphic rocks (of Caledonian age) exposed in allochthonous nappes are solely characterised by greenschist-, amphibolite- and/or MP granulite "facies" mineral assemblages that can be interpreted, in the absence of retrogression, to have formed in less deeply subducted (and/or metamorphic) environments. This duality in metamorphic "facies" allows for a discrimination (at least theoretically) between "deep" versus "shallow" rooted nappes (in central parts of the Scandinavian Caledonides). Conform this reasoning, this duality should also be present within the Caledonian mineral assemblages (= metamorphic overprint) of orogenic peridotites (in central parts of the orogen), which, at least in the allochtonous nappes, have been interpreted to be "isofacial" with their host country rocks (Bucher, 1991). The latter strongly contrast to the interpretation of their "primary" (="protolith"- related) mineral assemblage(s) which clearly suggest a bimodal origin: here called thick (>80 km) versus thin (< 70 km) rooted lithospheric mantle protoliths. Distinction can be made on the basis of the presence of the stable (minimal Proterozoic) garnet-olivine assemblages in the protolith (i.e. much older than the Scandian collision event (Brueckner et al., 2010). For this reason orogenic garnet peridotite was first called "relict" garnet peridotite (Brueckner and Medaris, 2000), later rephrased into mantle wedge garnet peridotite (MWgp) by Van Roermund (2009). MWgp occurs in the WGC and in the SNC of the Upper Allochthon in central Sweden (Zhang et al., 2009). Most (All?) other protolith assemblages of orogenic peridotite in the CSC belong to the thin-rooted protolith subtype. No examples are known to us in which thin rooted prototypes became overprinted (during the Caledonian orogeny) by (U)HP metamorphic minerals, except for the subduction zone garnet peridotites (SZgp) in the WGC (Van Roermund, 2009). The latter can thus savely be interpreted as being enclosed within normal "MP" (or lower pressure) nappe sequences. As such it will be clear that this duality in protolith (and/or metamorphic) mineral assemblages of orogenic peridotite can be used to identify former, but now strongly retrogressed, (U)HP metamorphic terranes in other parts of the CSC (Gee et al, 2012). For this reason a comparative study has been made concerning field, (micro-)structural, mineral-chemical and/or geochemical aspects of two major orogenic peridotites from the SNC, central Sweden; here called the Friningen Garnet Peridotite (FGP) and the Kittelfjäll Spinel Peridotite (KSP), both exposed within the central belt of the SNC in central Sweden. The ultimate aim was to investigate whether the MWgp sub-type can be extended towards (Al-poor) spinel-bearing protolith assemblages or not. Results, including some hitherto unexpected mechanical effects, will be presented. References: Brueckner, H.K., Carswell, D.A., Griffin, W.L., Medaris, L.G., Van Roermund, H.L.M., Cuthbert, S.J. (2010). The mantle and crustal evolution of two garnet peridotite suites from the Western Gneiss Region, Norwegian Caledonides: An isotopic investigation. Lithos, 117, 1-19. doi:10.1016/j. Lithos.2010.01.011 Brueckner, H.K.and Medaris, L.G. (2000). A general model for the intrusion and evolution of "mantle" garnet peridotites in high-pressure and ultra-high-pressure metamorphic terranes. J. Metamorphic Geol., 18, 123-133. Brueckner H.K. and Van Roermund,H.L.M. (2004). Dunk tectonics: A multiple subduction//eduction model for the evolution of the Scandinavian Caledonides. Tectonics, 23, TC2004, doi:10.1029/2003tc001502. Bucher, K. (1991). Mantle fragments in the Scandinavian Caledonides. Tectonophysics, 190, 173-192. Gee, D.G., Fossen, H., Henriksen, N., Higgins, K. (2008). From the Early Paleozoic Platforms of Baltica and Laurentia to the Caledonide Orogen of Scandinavia and Greenland. Episodes, 31, 44-51. Gee, D.G., Janak, M., Majka, J., Robinson, P., Van Roermund, H.L.M (2012). UHP metamorphism along the Baltoscandian outer margin: evidence from the Seve Nappe Complex of the Swedish Caledonides. Lithosphere, in press. Janak, M., Van Roermund, H., Majka, J., Gee, D. (2012). UHP metamorphism recorded by kyanite-bearing eclogite in the Seve Nappe Complex of northern Jämtland, Swedish Caledonides. Gondwana Research, in press. Van Roermund, H.L.M. (2009). Mantle-wedge garnet peridotites from the northernmost ultra-high pressure domain of the Western Gneiss Region, SW Norway. Eur. J. Mineralogy, 21, 1085-1096. Zhang, C., Van Roermund, H.L.M., Zhang, L.F (2011). 16 - Orogenic Garnet Peridotites: Tools to Reconstruct Paleo-Geodynamic Settings of Fossil Continental Collision Zones. In: Ultrahigh Pressure Metamorphism, 25 Years After The Discovery Of Coesite And Diamond. London. Doi:10.1016/B978-0-12-385144-4.00015-1

Chemical properties of dissolved organic matter derived from sugarcane rind and the impacts on copper adsorption onto red soil.

PubMed

Hu, Sihai; Wu, Yaoguo; Yi, Na; Zhang, Shuai; Zhang, Yuanjing; Xin, Xu

2017-09-01

Dissolved organic matter (DOM), as the most active organic carbon in the soil, has a coherent affinity with heavy metals from inherent and exogenous sources. Although the important roles of DOM in the adsorption of heavy metals in soil have previously been demonstrated, the heterogeneity and variability of the chemical constitution of DOM impede the investigation of its effects on heavy metal adsorption onto soil under natural conditions. Fresh DOM (FDOM) and degraded DOM (DDOM) from sugarcane rind were prepared, and their chemical properties were measured by Fourier-transform infrared spectrometry (FTIR), excitation-emission matrix (EEM) fluorescence spectroscopes, nuclear magnetic resonance (NMR), and molecular weight distribution (MWD). They were also used in batch experiments to evaluate their effects on the adsorption of Cu(II) onto farmland red soil. Based on our results, the chemical structure and composition of DDOM greatly varied; compared with FDOM, the C/O ratio (from 24.0 to 9.6%) and fluorescence index (FI) (from 1.4 to 1.0) decreased, and high molecular weight (>10 kDa) compounds increased from 23.18 to 70.51%, while low molecular weight (<3 kDa) compounds decreased from 56.13 to 12.13%; aromaticity and humification degree were markedly enhanced. The discrepancy of FDOM and DDOM in terms of chemical properties greatly influenced Cu(II) adsorption onto red soil by affecting DOM-Cu(II) complex capacity. The FDOM inhibited the adsorption of Cu(II), while DDOM promoted adsorption, which was significantly influenced by soil pH. Maximum adsorption capacity (Q m ) was 0.92 and 5.76 mg g -1 in the presence of FDOM and DDOM, respectively. The adsorption process with DDOM could be better described by the Langmuir model, while that with FDOM was better described by the Freundlich model. The impacts caused by the dynamic changes of the chemical properties of DOM under natural conditions should therefore be considered in the risk assessment and remediation of soils contaminated with heavy metals.

Mobilization of dissolved organic matter from soils and sediments impacted by thermal processes

NASA Astrophysics Data System (ADS)

Rosario-Ortiz, F.; Webster, J.; Retuta, A.; Borch, T.; Young, R. B.

2016-12-01

The frequency and intensity of wildfires has increased in recent decades and this trend is expected to continue for the foreseeable future. Global climate change is predicted to result in the persistence of warmer and drier conditions, leading to an increase in fire frequency, fire season duration, and fire-impacted area. This trend has specifically been observable in the Western United States. The impacts on forested watersheds and the high quality drinking water these forests provide are still relatively uncharacterized and elucidation is needed to adapt treatment strategies as wildfire frequency increases. One main concern is an increase in the mobilization of dissolved organic matter (DOM). Furthermore, there is paucity of information regarding how an altered landscape from wildland fires affects the physical and chemical properties of the DOM, which may adjust the mechanisms that control DOM release and ultimately lead to changes in treatment efficacy. Investigating these parameters may help to explain why this concentration has been observed to increase. Because DOM supplies the precursors for disinfection byproduct formation during drinking water treatment, such differences could affect drinking water quality and public health. In this work, we studied the effect of heating soils and litter on the mobilization of DOM. To do this, soils and litter from two geographical areas, a conifer forest the western U.S. and a deciduous forest collected from the eastern U.S., were collected and heated to 225 and 350 °C for 2 hours. The material was then suspended in water for 24 hours prior to filtration. Leachate water quality was assessed by testing for two parameters including dissolved organic carbon (DOC) concentration and optical properties (absorbance and fluorescence). The water samples were also extracted with C18 solid-phase extraction cartridges, eluted, and analyzed using Fourier transform ion cyclotron resonance mass spectrometry, a high resolution mass spectrometry technique that can simultaneously resolve and uniquely identify tens of thousands of molecular formulas in complex mixtures like DOM. The results indicated that chemical changes to the soil and litter organic matter account for the differences in DOM mobilization from forest materials after thermal alteration.

What can blueschists tell about the Deep? High Pressure in the Anatolide - Taurid Belt

NASA Astrophysics Data System (ADS)

Oberhaensli, R.

2011-12-01

High-pressure metamorphic terranes in the Anatolide - Taurid belt document the complex distribution of paleo-sutures in the Tethyan realm. Field based petrologic studies of metapelites in the Anatolide-Taurid realm allow to trace HP-LT metamorphism not only in the well known ophiolitic Tavsanli Zone (2.4 GPa/500 °C) but also in the Afyon Zone (0.9 GPa/350 °C), the Menderes Massif (1.2 Gpa/500 °C;) and in the Lycian Nappes (1.0 Gpa/400 °C) - all situated north of the so called Taurid Platform. While the HP metamorphism is dated to 90-80 Ma (Rb/Sr; Ar/Ar) in the Tavsanli Zone, it ranges from 60-70 Ma (Ar/Ar) in the Afyon Zone and its tectonic equivalent, the Lycian Nappes. The Afyon Zone s.l. is closely related to the glaucophane- lawsonite-bearing rocks of the Tavsanli Zone and its eastward extension. Blueschist-facies metamorphism is documented by Fe,Mg-carpholite in regionally distributed metapelites and glaucophane in sparse mafic rocks (Afyon, Menderes, Lycia). Since observations of HP are based on Fe,Mg-carpholite bearing metasediments and not on mafic blueschists new thermodynamic data and petrologic modelling was elaborated to match P-T data and field-based observations. Moreover, newly formed phengitic mica allows precise dating. Both, Tavsanli and Afyon Zones can be followed along strike over more than 600 km and around the southern edge of the Central Anatolian Crystalline Complex. The two zones are situated north of the Taurid Platform and correlate with the Amasia Zone in Armenia. To the extreme East the Bitlis Complex underwent a LT - HP metamorphic blueschist evolution (1,1 GPa/ 350 °C; glaucophane, Fe,Mg-carpholite) in its sedimentary cover while the basement is eclogitic. Depending on the structural position and mineral association of phengitic mica metamorphic ages of the Bitlis blueschists scatter around 70-80 Ma. Eclogites from the basement are slightly older. These LT-HP units cannot be correlated with the Tavsanli - Afyon blueschist belts since they occur south of the Taurid Platform. Thus the Bitlis Complex represents a terrane detached from the Arabian Platform that subsequently collided with the Taurus Platform during closure of the Neo-Tethys. In SW Anatolia, south of the Taurus Platform, the Alanya Zone documents a Late Cretaceous HP evolution with blueschists and eclogites. Together with the Bitlis Complex the two Late Cretaceous HP-LT regions represent a suture south of the Taurid Platform but still north of the Hatay - Güleyman - Zagros ophiolites separating the Arabian Platform from the Anatolide-Taurid realm. The dissection of the Anatolide-Taurid realm into several paleo-subduction zones of Late Cretaceous age impacts on the lithospheric structure and has consequences for the Tertiary plateau formation in Central and Eastern Anatolia. Geophysical data and observations from the East Anatolian Plateau can be explained with petrologic modelling when hydration of the lithospheric lids above subduction zones is considered.

Subduction of Proterozoic to Late Triassic continental basement in the Guatemala suture zone: A petrological and geochronological study of high-pressure metagranitoids from the Chuacús complex

NASA Astrophysics Data System (ADS)

Maldonado, Roberto; Ortega-Gutiérrez, Fernando; Ortíz-Joya, Guillermo A.

2018-05-01

Many continental subduction complexes contain abundant granitic rocks coexisting with minor volumes of eclogite-facies rocks. Characterization of granitic protoliths is crucial to decipher the origin of subducted continental crust, whereas knowledge of its metamorphic evolution is required to constrain the mechanisms of burial and exhumation. In this work we present geochronological and petrological evidence that demonstrate the occurrence of a subducted Proterozoic to Late Triassic granitic basement in the Chuacús complex of central Guatemala. Metagranitoids exposed in this area are interlayered with eclogite and other high-pressure rocks, and their structure is considerably variable due to strain partitioning during deformation. Laser ablation-inductively coupled plasma-mass spectrometry U-Pb zircon data from two ferroan metagranites yield protolith crystallization ages of ca. 1.1 Ga and their trace-element abundances suggest an origin related to intraplate magmatism, while a high-silica, peraluminous metagranite is dated at 1.0 Ga and was probably originated by partial melting of a high-grade continental crust. On the other hand, two megacrystic to augen metagranitoids yield protolith crystallization ages of ca. 224 Ma, which are identical within errors to the protolith age of hosted eclogitic metabasites. Their high incompatible trace element abundances together with the observed spatial-temporal relationships with mafic protoliths suggest that Late Triassic bimodal magmatism in the Chuacús complex was probably originated in a within-plate setting. Regardless of their age or structure, the studied metagranites preserve evidences for high-pressure metamorphic equilibration, such as the occurrence of Ca-rich garnet (XCa up to 0.52) in association with phengite (Si contents of up to 3.4 pfu) and rutile. The integration of Zr-in-rutile thermometry and phengite barometry allows the peak metamorphic conditions to be constrained at 640-680 °C and 13 kbar. This pressure-temperature estimate indicates that metagranitoids underwent high-pressure metamorphism but equilibrated at significantly lower pressures than associated eclogite-facies rocks, and, therefore, they do not necessarily share a common high-pressure metamorphic evolution. The new data show that the Chuacús complex in the study area represents a Proterozoic (1.1-1.0 Ga) to Late Triassic (220 Ma) continental basement that was subducted, and consequently metamorphosed under high-pressure conditions, during the Cretaceous evolution of the North America-Caribbean plate boundary.

A global carbon assimilation system based on a dual optimization method

NASA Astrophysics Data System (ADS)

Zheng, H.; Li, Y.; Chen, J. M.; Wang, T.; Huang, Q.; Huang, W. X.; Li, S. M.; Yuan, W. P.; Zheng, X.; Zhang, S. P.; Chen, Z. Q.; Jiang, F.

2014-10-01

Ecological models are effective tools to simulate the distribution of global carbon sources and sinks. However, these models often suffer from substantial biases due to inaccurate simulations of complex ecological processes. We introduce a set of scaling factors (parameters) to an ecological model on the basis of plant functional type (PFT) and latitudes. A global carbon assimilation system (GCAS-DOM) is developed by employing a Dual Optimization Method (DOM) to invert the time-dependent ecological model parameter state and the net carbon flux state simultaneously. We use GCAS-DOM to estimate the global distribution of the CO2 flux on 1° ×1° grid cells for the period from 2000 to 2007. Results show that land and ocean absorb -3.69 ± 0.49 Pg C year-1 and -1.91 ± 0.16 Pg C year-1, respectively. North America, Europe and China contribut -0.96 ± 0.15 Pg C year-1, -0.42 ± 0.08 Pg C year-1 and -0.21 ± 0.28 Pg C year-1, respectively. The uncertainties in the flux after optimization by GCAS-DOM have been remarkably reduced by more than 60%. Through parameter optimization, GCAS-DOM can provide improved estimates of the carbon flux for each PFT. Coniferous forest (-0.97 ± 0.27 Pg C year-1) is the largest contributor to the global carbon sink. Fluxes of once-dominant deciduous forest generated by BEPS is reduced to -0.79 ± 0.22 Pg C year-1, being the third largest carbon sink.

Effect of dissolved organic matter source and character on microbial Hg methylation in Hg–S–DOM solutions

USGS Publications Warehouse

Graham, Andrew M.; Aiken, George R.; Gilmour, Cynthia

2013-01-01

Dissolved organic matter (DOM) is a key component of fate and transport models for most metals, including mercury (Hg). Utilizing a suite of diverse DOM isolates, we demonstrated that DOM character, in addition to concentration, influences inorganic Hg (Hg(II)i) bioavailability to Hg-methylating bacteria. Using a model Hg-methylating bacterium, Desulfovibrio desulfuricansND132, we evaluated Hg-DOM-sulfide bioavailability in washed-cell assays at environmentally relevant Hg/DOM ratios (∼1–8 ng Hg/mg C) and sulfide concentrations (1–1000 μM). All tested DOM isolates significantly enhanced Hg methylation above DOM-free controls (from ∼2 to >20-fold for 20 mg C/L DOM solutions), but high molecular weight/highly aromatic DOM isolates and/or those with high sulfur content were particularly effective at enhancing Hg methylation. Because these experiments were conducted under conditions of predicted supersaturation with respect to metacinnabar (β-HgS(s)), we attribute the DOM-dependent enhancement of Hg(II)i bioavailability to steric and specific chemical (e.g., DOM thiols) inhibition of β-HgS(s) growth and aggregation by DOM. Experiments examining the role of DOM across a wide sulfide gradient revealed that DOM only enhances Hg methylation under fairly low sulfide conditions (≲30 μM), conditions that favor HgS nanoparticle/cluster formation relative to dissolved HgS species.

Bacterial production and their role in the removal of dissolved organic matter from tributaries of drinking water reservoirs.

PubMed

Kamjunke, Norbert; Oosterwoud, Marieke R; Herzsprung, Peter; Tittel, Jörg

2016-04-01

Enhanced concentrations of dissolved organic matter (DOM) in freshwaters are an increasing problem in drinking water reservoirs. In this study we investigated bacterial DOM degradation rates in the tributaries of the reservoirs and tested the hypotheses that (1) DOM degradation is high enough to decrease DOM loads to reservoirs considerably, (2) DOM degradation is affected by stream hydrology, and (3) phosphorus addition may stimulate bacterial DOM degradation. Bacterial biomass production, which was used as a measure of DOM degradation, was highest in summer, and was usually lower at upstream than at downstream sites. An important proportion of bacterial production was realized in epilithic biofilms. Production of planktonic and biofilm bacteria was related to water temperature. Planktonic production weakly correlated to DOM quality and to total phosphorus concentration. Addition of soluble reactive phosphorus did not stimulate bacterial DOM degradation. Overall, DOM was considerably degraded in summer at low discharge levels, whereas degradation was negligible during flood events (when DOM load in reservoirs was high). The ratio of DOM degradation to total DOM release was negatively related to discharge. On annual average, only 0.6-12% of total DOM released by the catchments was degraded within the tributaries. Copyright © 2016 Elsevier B.V. All rights reserved.

Inorganics in Organics: Tracking down the Intrinsic Equilibriums between Organic Molecules and Trace Elements in Oceanic Waters

NASA Astrophysics Data System (ADS)

Lechtenfeld, O. J.; Koch, B. P.; Kattner, G.

2010-12-01

Recent developments in analytical instrumentation enable to describe biogeochemical processes in oceanic waters on a molecular level. This is the prerequisite to integrate biological and geochemical parameters and to develop chemical cycles on a global perspective. The state-of-the-art Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) applications for dissolved organic matter (DOM) focus mainly on carbon, hydrogen, oxygen and nitrogen isotopes. Implementation of sulfur and especially phosphorus in the molecular formula assignment has been questionable because of ambiguous calculated elemental formulas. On the other hand, many compounds bearing these elements are well known to occur in the dissolved state as part of the permanent recycling processes (e.g. phospholipids, phosphonates) but analytics of dissolved organic phosphorus (DOP) and sulfur (DOS) are often hampered by the large inorganic P and S pools. Even less is known about complexation characteristics of the DOM moieties. Although electrochemical methods provide some information about trace metal speciation, the high amount of organic molecules and its insufficient description as chemical functional classes prevent the assignment of trace metals to ligand classes. Nevertheless, it is undoubtful that a varying but extensive amount of transition metals is bond in form of organic complexes. Hyphenation of reversed phase high performance liquid chromatography (RP-HPLC) with high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) is a valuable tool to study these metal-organic interactions in a qualitative and quantitative approach. We established a desolvation method that allows direct transfer of high organic solvent loads into the plasma. Thus, in combination with internal standardization and external calibration, the investigation of a broad polarity scale was possible. This approach overcomes previous restrictions to non-organic solvent separation techniques like size exclusion chromatography (SEC). We used solid phase extracted DOM (SPE-DOM) from Atlantic and Southern Ocean water samples to show that organic sulfur and phosphorus species can be separated via RP-HPLC and that the partitioning can be correlated to trace metal binding capabilities in the different fractions. A molecular level investigation of these fractions via FT-ICR-MS revealed further details of the complexation features and connects the polarity-based separation on a C18 column to O/C and H/C elemental ratios. With our study, we showed that biologically relevant transition metals (e.g. Fe, Ni, Cu) and uranium are intrinsic constituents of the DOM fractions. Moreover, a comparison between samples from different ecological provinces and diagenetic conditions was performed to highlight the benefits of this approach for future marine biogeochemical research.

Influence of dissolved organic matter on sorption and desorption of MCPA in ferralsol.

PubMed

Wu, Dongming; Yun, Yonghuan; Jiang, Lei; Wu, Chunyuan

2018-03-01

MCPA (4-chloro-2-methylphenoxyacetic acid) is an acidic herbicide, widely used in paddy fields. The presence of dissolved organic matter (DOM) modifies the sorption-desorption of herbicides in soils. In this study, effects of DOM on sorption- desorption of MCPA were tested using three typical ferralsol soil types from China: rhodic ferralsol, haplic ferralsol and paddy soil. DOM preparations were extracted from the paddy soil (DOM P ), from a compost mixture of cassava stems with chicken manure (DOM C ), and from rice straw (DOM R ). Sorption-desorption of MCPA in the tested soil types was shown to follow pseudo first-order kinetics, and the calculated isotherm data fitted well with a Freundlich equilibrium model in the range of the studied concentrations. MCPA was weakly sorbed by the soils, producing low Freundlich coefficient values (K f ) (0.854 to 4.237). The presence of DOM reduced the K f whereby DOM C had the strongest and DOM R the weakest effect. Presence of DOM also promoted MCPA desorption from the soils, again with DOM C having the strongest effect and DOM R the weakest. DOM coating changed the soil particle surface, as demonstrated by electron microscopy, and DOM also directly interacted with MCPA, as shown by Fourier-transform infrared spectroscopy. The experimental data were interpreted to suggest a competing sorption of DOM to ferralsol and an increased solubility of MCPA in the presence of DOM. The results indicate that the environmental risk of MCPA leaching to groundwater and surface flow is increased by presence of DOM, for instance as a result of organic fertilizer use. Copyright © 2017. Published by Elsevier B.V.

Relating the Chemical Composition of Dissolved Organic Matter Draining Permafrost Soils to its Photochemical Degradation in Arctic Surface Waters.

NASA Astrophysics Data System (ADS)

Ward, C.; Cory, R. M.

2015-12-01

Thawing permafrost soils are expected to shift the chemical composition of DOM exported to and degraded in arctic surface waters. While DOM photo-degradation is an important component of the freshwater C cycle in the Arctic, the molecular controls on DOM photo-degradation remain poorly understood, making it difficult to predict how shifting chemical composition may alter DOM photo-degradation in arctic surface waters. To address this knowledge gap, we quantified the susceptibility of DOM draining the shallow organic mat and the deeper permafrost layer to complete photo-oxidation to CO₂ and partial photo-oxidation to compounds that remain in the DOM pool, and investigated changes in DOM chemical composition following sunlight exposure. DOM leached from the organic mat contained higher molecular weight, more oxidized and unsaturated aromatic species compared to permafrost DOM. Despite significant differences in initial chemical composition, permafrost and organic mat DOM had similar susceptibilities to complete photo-oxidation to CO₂. Concurrent losses of carboxyl moieties and shifts in chemical composition during photo-degradation indicated that carboxyl-rich tannin-like compounds in both DOM sources were likely photo-decarboxylated to CO₂. Permafrost DOM had a higher susceptibility to partial photo-oxidation compared to organic mat DOM, potentially due to a lower abundance of phenolic compounds that act as "antioxidants" and slow the oxidation of DOM. These results demonstrated how chemical composition controls the photo-degradation of DOM in arctic surface waters, and that DOM photo-degradation will likely remain an important component of the freshwater C budget in the Arctic with increased export of permafrost DOM to surface waters.

Structures, microfabrics and textures of the Cordilleran-type Rechnitz metamorphic core complex, Eastern Alps☆

PubMed Central

Cao, Shuyun; Neubauer, Franz; Bernroider, Manfred; Liu, Junlai; Genser, Johann

2013-01-01

Rechnitz window group represents a Cordilleran-style metamorphic core complex, which is almost entirely located within nearly contemporaneous Neogene sediments at the transition zone between the Eastern Alps and the Neogene Pannonian basin. Two tectonic units are distinguished within the Rechnitz metamorphic core complex (RMCC): (1) a lower unit mainly composed of Mesozoic metasediments, and (2) an upper unit mainly composed of ophiolite remnants. Both units are metamorphosed within greenschist facies conditions during earliest Miocene followed by exhumation and cooling. The internal structure of the RMCC is characterized by the following succession of structure-forming events: (1) blueschist relics of Paleocene/Eocene age formed as a result of subduction (D1), (2) ductile nappe stacking (D2) of an ophiolite nappe over a distant passive margin succession (ca. E–W to WNW–ESE oriented stretching lineation), (3) greenschist facies-grade metamorphism annealing dominant in the lower unit, and (4) ductile low-angle normal faulting (D3) (with mainly NE–SW oriented stretching lineation), and (5) ca. E to NE-vergent folding (D4). The microfabrics are related to mostly ductile nappe stacking to ductile low-angle normal faulting. Paleopiezometry in conjunction with P–T estimates yield high strain rates of 10− 11 to 10− 13 s− 1, depending on the temperature (400–350 °C) and choice of piezometer and flow law calibration. Progressive microstructures and texture analysis indicate an overprint of the high-temperature fabrics (D2) by the low-temperature deformation (D3). Phengitic mica from the Paleocene/Eocene high-pressure metamorphism remained stable during D2 ductile deformation as well as preserved within late stages of final sub-greenschist facies shearing. Chlorite geothermometry yields two temperature groups, 376–328 °C, and 306–132 °C. Chlorite is seemingly accessible to late-stage resetting. The RMCC underwent an earlier large-scale coaxial deformation accommodated by a late non-coaxial shear with ductile low-angle normal faulting, resulting in subvertical thinning in the extensional deformation regime. The RMCC was rapidly exhumed during ca. 23–18 Ma. PMID:27065502

Complicated secondary textures in zircon record evolution of the host granitic rocks: Studies from Western Tauern Window and Ötztal-Stubai Crystalline Complex (Eastern Alps, Western Austria)

NASA Astrophysics Data System (ADS)

Kovaleva, Elizaveta; Harlov, Daniel; Klötzli, Urs

2017-07-01

Samples of metamorphosed and deformed granitic rocks were collected from two Alpine complexes with well-constrained metamorphic history: Western Tauern Window and Ötztal-Stubai Crystalline Complex. Zircon grains from these samples were investigated in situ by a combination of scanning electron microscope techniques, cathodoluminescence (CL) imaging and Raman spectroscopy. The aims were: to describe and interpret complicated secondary textures and microstructures in zircon; based on cross-cutting relationships between secondary microstructures, reconstruct the sequence of processes, affecting zircon crystals; link the evolution of zircon with the history of the host rocks. The results indicate that zircon in the sampled granitic rocks forms growth twins and multi-grain aggregates, which are unusual for this mineral. Moreover, various secondary textures have been found in the sampled zircon, often cross-cutting each other in a single crystal. These include: distorted oscillatory CL zoning with inner zones forming inward-penetrating, CL-bright embayments, which are the evidence of dry recrystallization via annealing/lattice recovery; CL mosaicism with no preservation of growth zoning, but abundant nano- and micro-scale pores and mineral inclusions, which are the evidence of recrystallization by coupled dissolution-reprecipitation and/or leaching; embayed zircon boundaries filled with apatite, monazite, epidote and mylonitic matrix, indicating mineral-fluid reactions resulting in zircon dissolution and fragmentation; overgrowth CL-dark rims, which contain nano-pores and point to transport and precipitation of dissolved zircon matter. We conclude that zircon in our meta-granites is sensitive to metamorphism/deformation events, and was reactive with metamorphic fluids. Additionally, we have found evidence of crystal-plastic deformation in the form of low angle boundaries and bent grain tips, which is a result of shearing and ductile deformation of the host rock. We suggest that the observed complicated secondary textures in zircon can be linked to the evolutionary stages of the host rocks such as magmatic crystallization, prograde metamorphism, peak of amphibolite-facies metamorphism, post-peak cooling and exhumation, formation of ductile shear zones and final cooling to 250 °C.

Metamorphic belts of Anatolia

NASA Astrophysics Data System (ADS)

Oberhänsli, Roland; Prouteau, Amaury; Candan, Osman; Bousquet, Romain

2015-04-01

Investigating metamorphic rocks from high-pressure/low-temperature (HP/LT) belts that formed during the closure of several oceanic branches, building up the present Anatolia continental micro-plate gives insight to the palaeogeography of the Neotethys Ocean in Anatolia. Two coherent HP/LT metamorphic belts, the Tavşanlı Zone (distal Gondwana margin) and the Ören-Afyon-Bolkardağ Zone (proximal Gondwana margin), parallel their non-metamorphosed equivalent (the Tauride Carbonate Platform) from the Aegean coast in NW Anatolia to southern Central Anatolia. P-T conditions and timing of metamorphism in the Ören-Afyon-Bolkardağ Zone (>70?-65 Ma; 0.8-1.2 GPa/330-420°C) contrast those published for the overlying Tavşanlı Zone (88-78 Ma; 2.4 GPa/500 °C). These belts trace the southern Neotethys suture connecting the Vardar suture in the Hellenides to the Inner Tauride suture along the southern border of the Kirşehir Complex in Central Anatolia. Eastwards, these belts are capped by the Oligo-Miocene Sivas Basin. Another HP/LT metamorphic belt, in the Alanya and Bitlis regions, outlines the southern flank of the Tauride Carbonate Platform. In the Alanya Nappes, south of the Taurides, eclogites and blueschists yielded metamorphic ages around 82-80 Ma (zircon U-Pb and phengite Ar-Ar data). The Alanya-Bitlis HP belt testifies an additional suture not comparable to the northerly Tavşanlı and Ören-Afyon belts, thus implying an additional oceanic branch of the Neotethys. The most likely eastern lateral continuation of this HP belt is the Bitlis Massif, in SE Turkey. There, eclogites (1.9-2.4 GPa/480-540°C) occur within calc-arenitic meta-sediments and in gneisses of the metamorphic (Barrovian-type) basement. Zircon U-Pb ages revealed 84.4-82.4 Ma for peak metamorphism. Carpholite-bearing HP/LT metasediments representing the stratigraphic cover of the Bitlis Massif underwent 0.8-1.2 GPa/340-400°C at 79-74 Ma (Ar-Ar on white mica). These conditions compares to the Tavşanlı-Afyon realm. However the differences in time and P-T conditions (eclogite- vs. blueschist-facies units) in the Bitlis Massif indicate that the different metamorphic peak conditions were reached at different times in a single subduction zone. Exhumation from approx. 65 to 35 km depth occurred within <10 myr. The special relations between eclogite-blueschist are due to the fact that collision with the Arabian plate was and still is on going in the Bitlis area. The Bitlis HP rocks represent a subduction realm that separated the Bitlis-Pütürge(-Bistun?) continental block from the South-Armenian (Tauride?) block, further north. Post-Eocene blueschists south of the Bitlis Massif witness the separation of the Bitlis-Pütüre block from the Arabian plate, and the southward migration of the subduction zone from the Late Cretaceous to the Oligocene. Continuous convergence of Africa and Eurasia engendered the simultaneous consumption of several, separated branches of the Neotethys Ocean and amalgamation of different terranes. The rise of the Eastern Anatolia Plateau is related to this complex geodynamic setting. Reduced seismic velocities inferred from geophysical observations, which are interpreted as complete replacement of lithospheric- by asthenospheric mantle, can be explained by thermodynamic modelling as partial hydration of the lithospheric mantle wedge during protracted subduction. Hydrated lithospheric mantle is interpreted as result of the complex geodynamic setting in Anatolia with multiple simultaneous subduction zones.

Developing an inverted Barrovian sequence; insights from monazite petrochronology

NASA Astrophysics Data System (ADS)

Mottram, Catherine M.; Warren, Clare J.; Regis, Daniele; Roberts, Nick M. W.; Harris, Nigel B. W.; Argles, Tom W.; Parrish, Randall R.

2014-10-01

In the Himalayan region of Sikkim, the well-developed inverted metamorphic sequence of the Main Central Thrust (MCT) zone is folded, thus exposing several transects through the structure that reached similar metamorphic grades at different times. In-situ LA-ICP-MS U-Th-Pb monazite ages, linked to pressure-temperature conditions via trace-element reaction fingerprints, allow key aspects of the evolution of the thrust zone to be understood for the first time. The ages show that peak metamorphic conditions were reached earliest in the structurally highest part of the inverted metamorphic sequence, in the Greater Himalayan Sequence (GHS) in the hanging wall of the MCT. Monazite in this unit grew over a prolonged period between ∼37 and 16 Ma in the southerly leading-edge of the thrust zone and between ∼37 and 14.5 Ma in the northern rear-edge of the thrust zone, at peak metamorphic conditions of ∼790 °C and 10 kbar. Monazite ages in Lesser Himalayan Sequence (LHS) footwall rocks show that identical metamorphic conditions were reached ∼4-6 Ma apart along the ∼60 km separating samples along the MCT transport direction. Upper LHS footwall rocks reached peak metamorphic conditions of ∼655 °C and 9 kbar between ∼21 and 16 Ma in the more southerly-exposed transect and ∼14.5-12 Ma in the northern transect. Similarly, lower LHS footwall rocks reached peak metamorphic conditions of ∼580 °C and 8.5 kbar at ∼16 Ma in the south, and 9-10 Ma in the north. In the southern transect, the timing of partial melting in the GHS hanging wall (∼23-19.5 Ma) overlaps with the timing of prograde metamorphism (∼21 Ma) in the LHS footwall, confirming that the hanging wall may have provided the heat necessary for the metamorphism of the footwall. Overall, the data provide robust evidence for progressively downwards-penetrating deformation and accretion of original LHS footwall material to the GHS hanging wall over a period of ∼5 Ma. These processes appear to have occurred several times during the prolonged ductile evolution of the thrust. The preserved inverted metamorphic sequence therefore documents the formation of sequential 'paleo-thrusts' through time, cutting down from the original locus of MCT movement at the LHS-GHS protolith boundary and forming at successively lower pressure and temperature conditions. The petrochronologic methods applied here constrain a complex temporal and thermal deformation history, and demonstrate that inverted metamorphic sequences can preserve a rich record of the duration of progressive ductile thrusting.

Spectral Exploration of Calcium Accumulation in Organic Matter in Gray Desert Soil from Northwest China

PubMed Central

Wang, Ping; Ma, Yucui; Wang, Xihe; Jiang, Hong; Liu, Hua; Ran, Wei; Shen, Qirong

2016-01-01

Little attention has been paid to the accumulation of soil organic matter (SOM) in the fringes of the mid-latitude desert. In this paper, soil samples from a long-term field experiment conducted from 1990 to 2013 at a research station in Urumqi, China by different fertilizer treatments, were used to determine soil properties and soil dissolved organic matter (DOM) by chemical analysis, fluorescence excitation emission matrix (EEM) spectroscopy, and high resolution-transmission electron microscopy (HR-TEM). The binding features of DOM under the addition of Ca2+ were analyzed using a two-dimensional (2D) Fourier transform infrared (FTIR) spectrometer further to explore the response of the DOM to increasing concentrations of Ca2+. Long-term application of chemical fertilizers and goat manure increased soil organic carbon (SOC) by 1.34- and 1.86-fold, respectively, relative to the non-fertilized control (8.95g.kg-1). Compared with the control, application of chemical fertilizers and manure significantly increased the concentrations of Ca, Mg, Si, humic and fulvic acid-like substances in DOM but decreased the amounts of trivalent metals (Al and Fe) and protein-like substances. Although crystalline Al/Fe nanoparticles and amorphous or short-range-order Si/Al nanoparticles existed in all DOM samples, crystalline Ca/Si nanoparticles were predominant in the samples treated with goat manure. Although organic matter and Si-O-containing nanoparticles were involved in the binding of Ca2+ to DOM, application of chemical fertilizers weakened Ca2+ association with components of the amide II group (1510 cm-1) and Si-O linkage (1080 cm-1), whereas application of goat manure enhanced the affinity of Ca2+ for Si-O linkage. Our results suggested that the enrichment of Ca in gray desert soil possibly helps accumulate SOM by forming crystalline Ca/Si nanoparticles in addition to Ca2+ and organic matter complexes. PMID:26751962

Characterizing the release of different composition of dissolved organic matter in soil under acid rain leaching using three-dimensional excitation-emission matrix spectroscopy.

PubMed

Liu, Li; Song, Cunyi; Yan, Zengguang; Li, Fasheng

2009-09-01

Although excitation-emission matrix spectroscopy (EEMS) has been widely used to characterize dissolved organic matter (DOM), there has no report that EEMS has been used to study the effects of acid rain on DOM and its composition in soil. In this work, we employed three-dimensional EEMS to characterize the compositions of DOM leached by simulated acid rain from red soil. The red soil was subjected to leaching of simulated acid rain of different acidity, and the leached DOM presented five main peaks in its EEMS: peak-A, related to humic acid-like (HA-like) material, at Ex/Em of 310-330/395-420nm; peak-B, related to UV fulvic acid-like (FA-like) material, at Ex/Em of 230-280/400-435nm; peak-C and peak-D, both related to microbial byproduct-like material, at Ex/Em of 250-280/335-355nm and 260-280/290-320nm, respectively; and peak-E, related to simple aromatic proteins, at Ex/Em of 210-240/290-340nm. EEMS analysis results indicated that most DOM could be lost from red soil in the early phase of acid rain leaching. In addition to the effects of the pH of acid rain, the loss of DOM also depended on the properties of its compositions and the solubility of their complexes with aluminum. HA-like and microbial byproduct-like materials could be more easily released from red soil by acid rain at both higher pH (4.5 and 5.6) and lower pH (2.5 and 3) than that at middle pH (3.5). On the contrary, FA-like material lost in a similar manner under the action of different acid rains with pH ranging from 2.5 to 5.6.

Spectral Exploration of Calcium Accumulation in Organic Matter in Gray Desert Soil from Northwest China.

PubMed

Wang, Ping; Ma, Yucui; Wang, Xihe; Jiang, Hong; Liu, Hua; Ran, Wei; Shen, Qirong

2016-01-01

Little attention has been paid to the accumulation of soil organic matter (SOM) in the fringes of the mid-latitude desert. In this paper, soil samples from a long-term field experiment conducted from 1990 to 2013 at a research station in Urumqi, China by different fertilizer treatments, were used to determine soil properties and soil dissolved organic matter (DOM) by chemical analysis, fluorescence excitation emission matrix (EEM) spectroscopy, and high resolution-transmission electron microscopy (HR-TEM). The binding features of DOM under the addition of Ca(2+) were analyzed using a two-dimensional (2D) Fourier transform infrared (FTIR) spectrometer further to explore the response of the DOM to increasing concentrations of Ca(2+). Long-term application of chemical fertilizers and goat manure increased soil organic carbon (SOC) by 1.34- and 1.86-fold, respectively, relative to the non-fertilized control (8.95 g.kg(-1)). Compared with the control, application of chemical fertilizers and manure significantly increased the concentrations of Ca, Mg, Si, humic and fulvic acid-like substances in DOM but decreased the amounts of trivalent metals (Al and Fe) and protein-like substances. Although crystalline Al/Fe nanoparticles and amorphous or short-range-order Si/Al nanoparticles existed in all DOM samples, crystalline Ca/Si nanoparticles were predominant in the samples treated with goat manure. Although organic matter and Si-O-containing nanoparticles were involved in the binding of Ca(2+) to DOM, application of chemical fertilizers weakened Ca(2+) association with components of the amide II group (1510 cm(-1)) and Si-O linkage (1080 cm(-1)), whereas application of goat manure enhanced the affinity of Ca(2+) for Si-O linkage. Our results suggested that the enrichment of Ca in gray desert soil possibly helps accumulate SOM by forming crystalline Ca/Si nanoparticles in addition to Ca(2+) and organic matter complexes.

Differences in dissolved organic matter between reclaimed water source and drinking water source.

PubMed

Hu, Hong-Ying; Du, Ye; Wu, Qian-Yuan; Zhao, Xin; Tang, Xin; Chen, Zhuo

2016-05-01

Dissolved organic matter (DOM) significantly affects the quality of reclaimed water and drinking water. Reclaimed water potable reuse is an effective way to augment drinking water source and de facto reuse exists worldwide. Hence, when reclaimed water source (namely secondary effluent) is blended with drinking water source, understanding the difference in DOM between drinking water source (dDOM) and reclaimed water source (rDOM) is essential. In this study, composition, transformation, and potential risk of dDOM from drinking water source and rDOM from secondary effluent were compared. Generally, the DOC concentration of rDOM and dissolved organic nitrogen (DON) content in reclaimed water source were higher but rDOM exhibited a lower aromaticity. Besides, rDOM comprises a higher proportion of hydrophilic fractions and more low-molecular weight compounds, which are difficult to be removed during coagulation. Although dDOM exhibited higher specific disinfection byproducts formation potential (SDBPFP), rDOM formed more total disinfection byproducts (DBPs) during chlorination including halomethanes (THMs) and haloacetic acids (HAAs) due to high DOC concentration. Likewise, in consideration of DOC basis, rDOM contained more absolute assimilable organic carbon (AOC) despite showing a lower specific AOC (normalized AOC per unit of DOC). Besides, rDOM exhibited higher biotoxicity including genotoxicity and endocrine disruption. Therefore, rDOM presents a greater potential risk than dDOM does. Reclaimed water source needs to be treated carefully when it is blended with drinking water source. Copyright © 2015. Published by Elsevier B.V.

Uncoupling of Bacterial and Terrigenous Dissolved Organic Matter Dynamics in Decomposition Experiments

PubMed Central

Herlemann, Daniel P. R.; Manecki, Marcus; Meeske, Christian; Pollehne, Falk; Labrenz, Matthias; Schulz-Bull, Detlef; Dittmar, Thorsten; Jürgens, Klaus

2014-01-01

The biodegradability of terrigenous dissolved organic matter (tDOM) exported to the sea has a major impact on the global carbon cycle, but our understanding of tDOM bioavailability is fragmentary. In this study, the effects of preparative tDOM isolation on microbial decomposition were investigated in incubation experiments consisting of mesocosms containing mesohaline water from the Baltic Sea. Dissolved organic carbon (DOC) consumption, molecular DOM composition, bacterial activities, and shifts in bacterial community structure were compared between mesocosms supplemented with riverine tDOM, either as filtered, particle-free river water or as a concentrate obtained by lyophilization/tangential ultrafiltration, and those containing only Baltic Sea water or river water. As shown using ultra-high-resolution mass spectrometry (15 Tesla Fourier-transform ion cyclotron resonance mass spectrometry, FT-ICR-MS) covering approximately 4600 different DOM compounds, the three DOM preparation protocols resulted in distinct patterns of molecular DOM composition. However, despite DOC losses of 4–16% and considerable bacterial production, there was no significant change in DOM composition during the 28-day experiment. Moreover, tDOM addition affected neither DOC degradation nor bacterial dynamics significantly, regardless of the tDOM preparation. This result suggested that the introduced tDOM was largely not bioavailable, at least on the temporal scale of our experiment, and that the observed bacterial activity and DOC decomposition mainly reflected the degradation of unknown, labile, colloidal and low-molecular weight DOM, both of which escape the analytical window of FT-ICR-MS. In contrast to the different tDOM preparations, the initial bacterial inoculum and batch culture conditions determined bacterial community succession and superseded the effects of tDOM addition. The uncoupling of tDOM and bacterial dynamics suggests that mesohaline bacterial communities cannot efficiently utilize tDOM and that in subarctic estuaries other factors are responsible for the removal of imported tDOM. PMID:24718626

Adsorptive fractionation of dissolved organic matter (DOM) by carbon nanotubes.

PubMed

Engel, Maya; Chefetz, Benny

2015-02-01

Dissolved organic matter (DOM) and carbon nanotubes are introduced into aquatic environments. Thus, it is important to elucidate whether their interaction affects DOM amount and composition. In this study, the composition of DOM, before and after interactions with single-walled carbon nanotubes (SWCNTs), was measured and the adsorption affinity of the individual structural fractions of DOM to SWCNTs was investigated. Adsorption of DOM to SWCNTs was dominated by the hydrophobic acid fraction, resulting in relative enhancement of the hydrophilic character of non-adsorbed DOM. The preferential adsorption of the HoA fraction was concentration-dependent, increasing with increasing concentration. Adsorption affinities of bulk DOM calculated as the normalized sum of affinities of the individual structural fractions were similar to the measured affinities, suggesting that the structural fractions of DOM act as independent adsorbates. The altered DOM composition may affect the nature and reactivity of DOM in aquatic environments polluted with carbon nanotubes. Copyright © 2014 Elsevier Ltd. All rights reserved.

Removal of dissolved organic matter by anion exchange: Effect of dissolved organic matter properties

USGS Publications Warehouse

Boyer, T.H.; Singer, P.C.; Aiken, G.R.

2008-01-01

Ten isolates of aquatic dissolved organic matter (DOM) were evaluated to determine the effect that chemical properties of the DOM, such as charge density, aromaticity, and molecular weight, have on DOM removal by anion exchange. The DOM isolates were characterized asterrestrial, microbial, or intermediate humic substances or transphilic acids. All anion exchange experiments were conducted using a magnetic ion exchange (MIEX) resin. The charge density of the DOM isolates, determined by direct potentiometric titration, was fundamental to quantifying the stoichiometry of the anion exchange mechanism. The results clearly show that all DOM isolates were removed by anion exchange; however, differences among the DOM isolates did influence their removal by MIEX resin. In particular, MIEX resin had the greatest affinity for DOM with high charge density and the least affinity for DOM with low charge density and low aromaticity. This work illustrates that the chemical characteristics of DOM and solution conditions must be considered when evaluating anion exchange treatment for the removal of DOM. ?? 2008 American Chemical Society.

Evidence for pre-Taconic metamorphism in the Potomac terrane, Maryland and Virginia: Hornblende and Muscovite [sup 40]Ar/[sup 39]Ar results

DOE Office of Scientific and Technical Information (OSTI.GOV)

Becker, J.L.; Wintsch, R.P.; Kunk, M.J.

1993-03-01

New [sup 40]Ar/[sup 39]Ar age spectra of hornblende and white mica from the Great Falls area of the Potomac terrane of Maryland and Virginia indicate pre-Taconic metamorphism. Age spectra of hornblende samples are interpreted to represent cooling from peak metamorphic conditions through their closure temperatures for argon diffusion ([approximately]500C) at about 490 Ma. These older Ordovician postmetamorphic cooling ages strongly contrast with younger post-Ordovician metamorphic cooling ages now being reported in the Blue Ridge and Goochland terranes to the west and east respectively. A late phyllitic sheen observed on rocks in the field and petrographic observations of undulose plagioclase andmore » amphibole, and older muscovite, and kinked primary muscovite in the Bear Island Granodiorite reflect a younger retrogressive metamorphism involving the growth of secondary muscovite (Fisher's S4 ). [sup 40]Ar/[sup 39]Ar Age spectra of white micas from the Bear Island Granodiorite are complex and probably indicate both primary and secondary white mica, the latter apparently growing below the closure temperature for retention of argon in muscovite ([approximately]350C). The age spectra permit an estimate of a minimum age of 420 Ma for cooling through closure of the older generation of white mica. The above ages of hornblende and muscovite closure imply a minimum cooling rate of [approximately]2C/m.y., and exhumation rate of about 1 mm/yr. The projected time of peak metamorphism at upper amphibolite facies for the Great Falls area clearly predates the Ordovician Taconic orogeny and suggests that these rocks escaped this event and largely escaped younger Paleozoic metamorphic events, which are well documented in adjacent terranes.« less

Mapping age and trace elements using laser ablation split-stream (LASS) ICPMS

NASA Astrophysics Data System (ADS)

Kylander-Clark, A. R.; Hacker, B. R.; Cottle, J. M.

2012-12-01

One of the biggest challenges in the determination of the timing and rates of metamorphic processes is tying the age of a particular mineral to the conditions (i.e., pressure, temperature, fluid composition) at which that phase grew. Conventional microbeam techniques increase our understanding of crustal evolution by enabling this linkage; e.g., x-ray maps of monazite allow us to pinpoint grain segments that grew under a different set of conditions, cathodoluminescence images of zircon reveal zoning patterns and hence targets for dating different metamorphic and/or igneous events, and rare-earth element (REE) transects across garnet reveal the budget of a variety of trace elements during a metamorphic episode, to name but a few. More recent advances in LA-ICPMS and SIMS have allowed the ability to produce age maps or trace element maps—thus further our understanding of crystallization processes—but not both. Here we employ laser ablation split-stream (LASS) to quantitatively image the age, and trace element signature of datable phases such as zircon, monazite, titanite, and rutile in metamorphic rocks on the micron scale. By mapping the age and TE signature of a metamorphic phase, we can better interpret the metamorphic stage at which all portions of that phase grew, and relate it to other phases/portions of phases within that rock, such as garnet. For example, zircons and monazites from from eclogites reveal complex zoning in REEs indicating growth prior to, during, and post eclogite-facies metamorphism; those zones correspond to distinct age domains. Metamorphosed titanite reveals differences in diffusivities of TEs in inherited portions of the grain; e.g., Pb-loss is more prominent than diffusion of REEs, which in turn diffuse faster than higher charged ions, such as Th.

Long distance transport of eclogite and blueschist during early Pacific Ocean subduction rollback

NASA Astrophysics Data System (ADS)

Tamblyn, Renee; Hand, Martin; Kelsey, David; Phillips, Glen; Anczkiewicz, Robert

2017-04-01

The Tasmanides in eastern Australia represent a period of continental crustal growth on the western margin of the Pacific Ocean associated with slab rollback from the Cambrian until the Triassic. During rollback numerical models predict that subduction products can become trapped in the forearc (Geyra et al., 2002), and can migrate with the trench as it retreats. In a long-lived subduction controlled regime such as the Tasmanides, this should result in an accumulation of subduction products with protracted geochronological and metamorphic histories. U-Pb, Lu-Hf, Sm-Nd and Ar-Ar geochronology and phase equilibria modelling of lawsonite-eclogite and garnet blueschist in the Southern New England Fold Belt in Australia demonstrate that high-P low-T rocks remained within a subduction setting for c. 40 Ma, from c. 500 to 460 Ma. High-P metamorphic rocks initially formed close to the Australian cratonic margin during the late Cambrian, and were subsequently transported over 1500 Ma oceanward, during which time subducted material continued to accumulate, resulting in the development of complex mélange which records eclogite and blueschist metamorphism and partial exhumation over 40 Ma. The duration of refrigerated metamorphism approximates the extensional evolution of the upper plate which culminated in the development of the Lachlan Fold Belt. The protracted record of eclogite and blueschist metamorphism indicates that rapid exhumation is not necessarily required for preservation of high-pressure metamorphic rocks from subduction systems. Reference: Gerya, T. V., Stockhert, B., & Perchuk, A. L. (2002). Exhumation of high-pressure metamorphic rocks in a subduction channel: A numerical simulation. Tectonics, 21(6), 6-1-6-19. doi:10.1029/2002tc001406

The Age and Geodynamic Evolution of the Metamorphic sole rocks from Izmir-Ankara-Erzıncan suture zone (Northern-Turkey)

NASA Astrophysics Data System (ADS)

Melih Çörtük, Rahmi; Faruk Çelik, Ömer; Özkan, Mutlu; Sherlock, Sarah C.; Marzoli, Andrea; Altıntaş, İsmail Emir; Topuz, Gültekin

2016-04-01

The İzmir-Ankara-Erzincan suture zone in northern Turkey is one of the major tectonic zones separating the Pontides to the North from the Anatolide-Tauride block and Kı rşehir Massif to the South. The accretionary complex of the İzmir-Ankara-Erzincan suture zone, near Artova, is composed mainly of peridotites with varying degree serpentinization, metamorphic rocks, basalt, sandstones, pelagic and neritic limestones. The metamorphic rocks are represented by amphibolite, garnet micaschit, calc-schist and marble. The metamorphic rocks were interpreted as the metamorphic sole rocks. Because; (i) They are tectonically located beneath the serpentinized peridotites. (ii) Foliation planes of both the amphibolites and mantle tectonites are parallel to each other. (iii) The metamorphic rocks are crosscut by non-metamorphic dolerite dikes which exhibite Nb and Ta depletion relative to Th enrichment on the N-MORB normalized multi-element spider diagram. The dolerite dikes display flat REE patterns (LaN/YbN=0.85-1.24). These geochemical signatures of the dolerite dikes are indicative of subduction component during their occurrences. Geochemical observations of the amphibolites suggest E-MORB- and OIB-like signatures (LaN/SmN= 1.39-3.14) and their protoliths are represented by basalt and alkali basaltic rocks. Amphiboles from the amphibolites are represented by calcic amphiboles (magnesio-hornblende, tchermakite and tremolite) and they yielded 40Ar-39Ar ages between 157.8 ± 3.6 Ma and 139 ± 11 Ma. These cooling ages were interpreted to be the intra-oceanic subduction/thrusting time of the İzmir-Ankara-Erzincan oceanic domain. This study was funded by TÜBİTAK (Project no: 112Y123).

Volatile transfer and recycling at convergent margins: Mass-balance and insights from high-P/T metamorphic rocks

NASA Astrophysics Data System (ADS)

Bebout, Gray E.

The efficiency with which volatiles are deeply subducted is governed by devolatilization histories and the geometries and mechanisms of fluid transport deep in subduction zones. Metamorphism along the forearc slab-mantle interface may prevent the deep subduction of many volatile components (e.g., H2O, Cs, B, N, perhaps As, Sb, and U) and result in their transport in fluids toward shallower reservoirs. The release, by devolatilization, and transport of such components toward the seafloor or into the forearc mantle wedge, could in part explain the imbalances between the estimated amounts of subducted volatiles and the amounts returned to Earth's surface. The proportion of the initially subducted volatile component that is retained in rocks subducted to depths greater than those beneath magmatic arcs (>100 km) is largely unknown, complicating assessments of deep mantle volatile budgets. Isotopic and trace element data and volatile contents for the Catalina Schist, the Franciscan Complex, and eclogite-facies complexes in the Alps (and elsewhere) provide insight into the nature and magnitude of fluid production and transport deep in subduction zones and into the possible effects of metamorphism on the compositions of subducting rocks. Compatibilities of the compositions of the subduction-related rocks and fluids with the isotopic and trace element compositions of various mantle-derived materials (igneous rocks, xenoliths, serpentinite seamounts) indicate the potential to trace the recycling of rock and fluid reservoirs chemically and isotopically fractionated during subduction-zone metamorphism.

Hydrology controls dissolved organic matter export and composition in an Alpine stream and its hyporheic zone.

PubMed

Fasching, Christina; Ulseth, Amber J; Schelker, Jakob; Steniczka, Gertraud; Battin, Tom J

2016-03-01

Streams and rivers transport dissolved organic matter (DOM) from the terrestrial environment to downstream ecosystems. In light of climate and global change it is crucial to understand the temporal dynamics of DOM concentration and composition, and its export fluxes from headwaters to larger downstream ecosystems. We monitored DOM concentration and composition based on a diurnal sampling design for 3 years in an Alpine headwater stream. We found hydrologic variability to control DOM composition and the coupling of DOM dynamics in the streamwater and the hyporheic zone. High-flow events increased DOM inputs from terrestrial sources (as indicated by the contributions of humic- and fulvic-like fluorescence), while summer baseflow enhanced the autochthonous imprint of DOM. Diurnal and seasonal patterns of DOM composition were likely induced by biological processes linked to temperature and photosynthetic active radiation (PAR). Floods frequently interrupted diurnal and seasonal patterns of DOM, which led to a decoupling of streamwater and hyporheic water DOM composition and delivery of aromatic and humic-like DOM to the streamwater. Accordingly, DOM export fluxes were largely of terrigenous origin as indicated by optical properties. Our study highlights the relevance of hydrologic and seasonal dynamics for the origin, composition and fluxes of DOM in an Alpine headwater stream.

Jurassic to Miocene magmatism and metamorphism in the Mogok metamorphic belt and the India-Eurasia collision in Myanmar

NASA Astrophysics Data System (ADS)

Barley, M. E.; Pickard, A. L.; Zaw, Khin; Rak, P.; Doyle, M. G.

2003-06-01

Situated south of the eastern Himalayan syntaxis at the western margin of the Shan-Thai terrane the high-grade Mogok metamorphic belt (MMB) in Myanmar occupies a key position in the tectonic evolution of Southeast Asia. The first sensitive high-resolution ion microprobe U-Pb in zircon geochronology for the MMB shows that strongly deformed granitic orthogneisses near Mandalay contain Jurassic (˜170 Ma) zircons that have partly recrystallized during ˜43 Ma high-grade metamorphism. A hornblende syenite from Mandalay Hill also contains Jurassic zircons with evidence of Eocene metamorphic recrystallization rimmed by thin zones of 30.9 ± 0.7 Ma magmatic zircon. The relative abundance of Jurassic zircons in these rocks is consistent with suggestions that southern Eurasia had an Andean-type margin at that time. Mid-Cretaceous to earliest Eocene (120 to 50 Ma) I-type granitoids in the MMB, Myeik Archipelago, and Western Myanmar confirm that prior to the collision of India, an up to 200 km wide magmatic belt extended along the Eurasian margin from Pakistan to Sumatra. Metamorphic overgrowths to zircons in the orthogneiss near Mandalay date a period of Eocene (˜43 Ma) high-grade metamorphism possibly during crustal thickening related to the initial collision between India and Eurasia (at 65 to 55 Ma). This was followed by emplacement of syntectonic hornblende syenites and leucogranites between 35 and 23 Ma. Similar syntectonic syenites and leucogranites intruded the Ailao Shan-Red River shear belt in southern China and Vietnam during the Eocene-Oligocene to Miocene, and the Wang Chao and Three Pagodas faults in northern Thailand (that most likely link with the MMB) were also active at this time. The complex history of Eocene to early Miocene metamorphism, deformation, and magmatism in the MMB provides evidence that it may have played a key role in the network of deformation zones that accommodated strain during the northwards movement of India and resulting extrusion or rotation of Indochina.

Late Cretaceous to Paleocene metamorphism and magmatism in the Funeral Mountains metamorphic core complex, Death Valley, California

USGS Publications Warehouse

Mattinson, C.G.; Colgan, J.P.; Metcalf, J.R.; Miller, E.L.; Wooden, J.L.

2007-01-01

Amphibolite-facies Proterozoic metasedimentary rocks below the low-angle Ceno-zoic Boundary Canyon Detachment record deep crustal processes related to Meso-zoic crustal thickening and subsequent extension. A 91.5 ?? 1.4 Ma Th-Pb SHRIMP-RG (sensitive high-resolution ion microprobe-reverse geometry) monazite age from garnet-kyanite-staurolite schist constrains the age of prograde metamorphism in the lower plate. Between the Boundary Canyon Detachment and the structurally deeper, subparallel Monarch Spring fault, prograde metamorphic fabrics are overprinted by a pervasive greenschist-facies retrogression, high-strain subhorizontal mylonitic foliation, and a prominent WNW-ESE stretching lineation parallel to corrugations on the Boundary Canyon Detachment. Granitic pegmatite dikes are deformed, rotated into parallelism, and boudinaged within the mylonitic foliation. High-U zircons from one muscovite granite dike yield an 85.8 ?? 1.4 Ma age. Below the Monarch Spring fault, retrogression is minor, and amphibolite-facies mineral elongation lineations plunge gently north to northeast. Multiple generations of variably deformed dikes, sills, and leucosomal segregations indicate a more complex history of partial melting and intrusion compared to that above the Monarch Spring fault, but thermobarometry on garnet amphibolites above and below the Monarch Spring fault record similar peak conditions of 620-680 ??C and 7-9 kbar, indicating minor (<3-5 km) structural omission across the Monarch Spring fault. Discordant SHRIMP-RG U-Pb zircon ages and 75-88 Ma Th-Pb monazite ages from leucosomal segregations in paragneisses suggest that partial melting of Proterozoic sedimentary protoliths was a source for the structurally higher 86 Ma pegmatites. Two weakly deformed two-mica leucogranite dikes that cut the high-grademetamorphic fabrics below the Monarch Spring fault yield 62.3 ?? 2.6 and 61.7 ?? 4.7 Ma U-Pb zircon ages, and contain 1.5-1.7 Ga cores. The similarity of metamorphic, leuco-some, and pegmatite ages to the period of Sevier belt thrusting and the period of most voluminous Sierran arc magmatism suggests that both burial by thrusting and regional magmatic heating contributed to metamorphism and subsequent partial melting. ??2007 Geological Society of America. All rights reserved.

Microstructural observation and chemical dating on monazite from the Shilu Group, Hainan Province of South China: Implications for origin and evolution of the Shilu Fe-Co-Cu ore district

NASA Astrophysics Data System (ADS)

Xu, Deru; Kusiak, Monika A.; Wang, Zhilin; Chen, Huayong; Bakun-Czubarow, Nonna; Wu, Chuanjun; Konečný, Patrik; Hollings, Peter

2015-02-01

New monazite chemical U-Th-total-Pb (CHIME) ages, combined with microstructural observations, mineral compositions, and whole-rock geochemistry, indicate that the large-scale, banded iron formation (BIF)-type Shilu Fe-Co-Cu ore district in Hainan Province, South China is a multistage product of sedimentation, metamorphism, and hydrothermal-metasomatic alteration associated with multiple orogenies. Two types of monazite, i.e. "polygenetic" and "metamorphic", were identified. The "polygenetic monazite" comprises a magmatic and/or metamorphic core surrounded by a metamorphic rim, and shows complex zoning. Breakdown corona structure, with a core of monazite surrounded by a mantle of fluorapatite, allanite, and/or epidote as concentric growth rings, is commonly observed. This type of monazite yielded three main CHIME-age peaks at ca. 980 Ma, ca. 880 Ma and ca. 450 Ma. The ages which range up to ca. 880 Ma for detrital cores, record a pre-deformational magmatic and/or metamorphic event(s), and is considered to be the depositional time-interval of the Shilu Group and interbedded BIFs in a marine, back-arc foreland basin likely due to the Grenvillian or South China Sibao orogeny. After deposition, the Shilu district was subjected to an orogenic event, which is recorded by the syndeformational metamorphic monazite with ca. 560-450 Ma population. Probably this event not only caused amphibolite facies metamorphism and associated regional foliation S1 but also enriched the original BIFs, and most likely corresponds to the "Pan-African" and/or the South China Caledonian orogeny. The post-deformational "metamorphic" monazite occurs mostly as inclusions in garnet and shows ca. 260 Ma age. It likely represents the Late Permian post-magmatic hydrothermal and related retrograde event(s) initiated by the Indosinian orogeny due to the closure of the Paleo-Tethys. The breakdown of monazite to secondary coronal mineral phases as well as the Fe-remobilization and associated skarnization of the Shilu BIF ore source rocks might also be induced during this retrograde greenschist-facies metamorphism.

Dissolved organic matter and estrogen interactions regulate estrogen removal in the aqueous environment: A review.

PubMed

Ma, Li; Yates, Scott R

2018-06-03

This review summarizes the characterization and quantification of interactions between dissolved organic matter (DOM) and estrogens as well as the effects of DOM on aquatic estrogen removal. DOM interacts with estrogens via binding or sorption mechanisms like π-π interaction and hydrogen bonding. The binding affinity is evaluated in terms of organic-carbon-normalized sorption coefficient (Log K OC ) which varies with types and composition of DOM. DOM has been suggested to be a more efficient sorbent compared with other matrices, such as suspended particulate matter, sediment and soil; likely associated with its large surface area and concentrated carbon content. As a photosensitizer, DOM enhanced estrogen photodegradation when the concentration of DOM was below a threshold value, and when above, the acceleration effect was not observed. DOM played a dual role in affecting biodegradation of estrogens depending on the recalcitrance of the DOM and the nutrition status of the degraders. DOM also acted as an electron shuttle (redox mediator) mediating the degradation of estrogens. DOM hindered enzyme-catalyzed removal of estrogens while enhanced their transformation during the simultaneous photo-enzymatic process. Membrane rejection of estrogens was pronounced for hydrophobic DOM with high aromaticity and phenolic moiety content. Elimination of estrogens via photolysis, biodegradation, enzymolysis and membrane rejection in the presence of DOM is initiated by sorption, accentuating the role of DOM as a mediator in regulating aquatic estrogen removal. Published by Elsevier B.V.

Dissolved Organic Matter in Groundwater: a Shadow of its Former Self

NASA Astrophysics Data System (ADS)

Chapelle, F.

2017-12-01

The occurrence and dynamics of dissolved organic matter (DOM) are fundamentally different between ground- and surface water systems. The most obvious difference is that primary production, an important source of DOM to many surface waters, it is wholly absent from groundwater systems. Because of that, the composition and bioavailability of DOM is functionally linked to its residence time within the subsurface. While sorption/desorption processes segregate chemical fractions of DOM in both ground- and surface water systems, their effects are magnified by the much higher sediment/water mass ratio characteristic of groundwater systems. These differences, which often act in concert with each other, explain many observed characteristics of DOM in groundwater systems including (1) the low and nearly uniform DOM concentrations (0.5-1.0 mg/L) characteristic of many aquifers, (2) the progressive loss of carbohydrate and amino acid DOM and the enrichment of aromatic DOM, with increasing aquifer residence time (3) the progressive loss of VIS/UV absorption capacity (color) of DOM with increasing aquifer residence time, (4) the negative correlation between dissolved oxygen concentrations and DOM bioavailability, and (5) the positive correlation between DOM bioavailability and the final products of anoxic redox processes. Thus, while the principal sources of DOM to many groundwater systems are surface-derived, the dynamics unique to subsurface environments tend to render that DOM a shadow of its former self.

High-temperature metamorphism and its relation with magmatism (Svecofennian Belt, the Ladoga region, Russia)

NASA Astrophysics Data System (ADS)

Baltybaev, Shauket

2010-05-01

The Ladoga region, situated in the south-eastern part of the Fennoscandian shield, is subdivided into the Archean (ARD) and the Proterozoic (PRD) domains. The boundary between them is a wide shear-zone. The ARD consists mostly of AR-PR middle-low temperature gneisses and the PRD consists of turbidites, pelites, volcanics metamorphosed under HT-conditions (granulite facies). Metamorphism within the PRD is culminated at T= 800-900C and P=5-6 kbar. The peak of metamorphism of granulite facies is dated at 1881 Ma by Pb-Pb stepwise leaching method of rock-forming minerals of the granulites. Pb-Pb results are within error limits coeval with the U-Pb ages of metamorphic monazites. The same (1881Ma) age has gabbro-enderbites. Next stage of metamorphism lasts from 1881 to 1860 Ma under conditions of amphibolite facies. It was restricted with U-Pb, Pb-Pb, Sm-Nd data based on the closure temperature of zircon, monazite, garnet, sillimanite from gneisses, leucosomes of migmatites and synmetamorphic diorites and tonalites. The lowermost point of the trend shows P-T: ~3-4 kbar, 600C. By the time 1860 Ma K-rich granites were emplaced and the uppermost limit for granulite metamorphism comes from the ages of the aplitic/pegmatitic veins (1860-1850 Ma), which cut the K-rich granites. Thermal and tectonic settings can be described based on spatial and temporal changes during magma emplacement. The granulites of the PRD were produced by the emplacement of the extensive basic intrusion (gabbro-enderbites) into the lower-middle crust. A prolonged thermal flux over all area was supported by new generated dioritic and tonalitic melts, which were intruded into the middle crust. The final stage of tectono-metamorphic evolution was marked by emplacement of the K-rich granites. Numerical simulation of the process of magma emplacement (sequences: gabbro-enderbites, diorites and tonalites) and related heat production shows good correlation between intrusive activity and metamorphism of the surrounding rocks. Baltybaev Sh. K., Levchenkov O. A., Levsky L. K., Eklund O., Kilpeläinen T. 2006. Two metamorphic stages in the Svecofennian Domain: evidence from the isotopic geochronological study of the Ladoga and Sulkava metamorphic complexes. Petrology, 14(3), 247-261.

Stacking and metamorphism of continuous segments of subducted lithosphere in a high-pressure wedge: The example of Alpine Corsica (France)

NASA Astrophysics Data System (ADS)

Vitale Brovarone, Alberto; Beyssac, Olivier; Malavieille, Jacques; Molli, Giancarlo; Beltrando, Marco; Compagnoni, Roberto

2013-01-01

Alpine Corsica consists of a stack of variably metamorphosed units of continental and Tethys-derived rocks. It represents an excellent example of high-pressure (HP) orogenic belt, such as the Western Alps, exposed over a small and accessible area. Compared to the Western Alps, the geology of Alpine Corsica is poorly unraveled. During the 1970s-80s, based on either lithostratigraphic or metamorphic field observations, various classifications of the belt have been proposed, but these classifications have been rarely matched together. Furthermore, through time, the internal complexity of large domains has been progressively left aside in the frame of large-scale geodynamic reconstructions. As a consequence, major open questions on the internal structure of the belt have remained unsolved. Apart from a few local studies, Alpine Corsica has not benefited of modern developments in petrology and basin research. This feature results in several uncertainties when combining lithostratigraphic and metamorphic patterns and, consequently, in the definition of an exhaustive architecture of the belt. In this paper we provide a review on the geology of Alpine Corsica, paying particular attention to the available lithostratigraphic and metamorphic classifications of the metamorphic terranes. These data are completed by a new and exhaustive metamorphic dataset obtained by means of thermometry based on Raman Spectroscopy of Carbonaceous Material (RSCM). This technique provides reliable insights on the peak temperature of the metamorphic history for CM-bearing metasediments. A detailed metamorphic characterization of metasediments, which have been previously largely ignored due to retrogression or to the lack of diagnostic mineralogy, is thus obtained and fruitfully coupled with the available lithostratigraphic data. Nine main tectono-metamorphic units are defined, from subgreenschist (ca. 280-300 °C) to the lawsonite-eclogite-facies (ca. 500-550 °C) condition. These units are homogeneous in metamorphism, laterally continuous and have characteristic lithostratigraphic features. This study also suggests a direct link between the pre-orogenic extensional setting and the present-day compressional structure of Alpine Corsica, indicating that large sections of subducted lithosphere were subducted and exhumed as coherent domains. These features provide important insight on the mechanism of stacking and exhumation of HP rocks, and make Alpine Corsica a unique reference for mountain-building processes in Tethyan-type orogens.

Dissolved oxygen and its response to eutrophication in a tropical black water river.

PubMed

Rixen, Tim; Baum, Antje; Sepryani, Harni; Pohlmann, Thomas; Jose, Christine; Samiaji, Joko

2010-08-01

The Siak is a typical, nutrient-poor, well-mixed, black water river in central Sumatra, Indonesia, which owes its brown color to dissolved organic matter (DOM) leached from surrounding, heavily disturbed peat soils. We measured dissolved organic carbon (DOC) and oxygen concentrations along the river, carried out a 36-h experiment in the province capital Pekanbaru and quantified organic matter and nutrient inputs from urban wastewater channels into the Siak. In order to consider the complex dynamic of oxygen in rivers, a box-diffusion model was used to interpret the measured data. The results suggest that the decomposition of soil derived DOM was the main factor influencing the oxygen concentration in the Siak which varied between approximately 100 and 140 micromol l(-1). Additional DOM input caused by wastewater discharges appeared to reduce the oxygen concentrations by approximately 20 micromol l(-1) during the peak-time in household water use in the early morning and in the early evening. Associated enhanced nutrient inputs appear to reduce the impact of the anthropogenic DOM by favoring the photosynthetic production of oxygen in the morning. A reduction of 20 micromol l(-1), which although perhaps not of great significance in Pekanbaru, has strong implications for wastewater management in the fast developing areas downstream Pekanbaru where oxygen concentrations rarely exceed 20 micromol l(-1). Copyright 2010 Elsevier Ltd. All rights reserved.

Visualizing DOM super-spectrum covariance in vanKrevelen space

NASA Astrophysics Data System (ADS)

Fatland, D. R.; Kalawe, J.; Stubbins, A.; Spencer, R. G.; Sleighter, R. L.; Abdulla, H. A.; Dittmar, T.

2011-12-01

We investigate the fate of terrigenous organic matter, DOM exported to the coastal marine environ. Many methods (fluor., FT-ICR-MS, NMR, 13C, lignin, etc) help characterize this DOM. We define a 'super spectrum' as amalgamation of analyses to a data stack and we search for physically significant patterns therein beginning with covariance across 31 samples from six circum-Arctic rivers: The Ob, Kolyma, Mackenzie, Yukon, Lena, and Yenisey sampled five times throughout the year. A vanKrevelen diagram is convenient to view distributions of molecules provided by Fourier Transform Ion Cyclotron Resonance Mass Spectometry (FT-ICR-MS). We augment this distribution space in the vertical dimension, for example to show peak height, molecular mass, principle component weighting or covariance. We use Worldwide Telescope, a virtual globe with strong data support from Microsoft Research to explore covariance results along 3+ dimensions (adding brightness, color and a parameter slide). The results show interesting covariance e.g. between molecules and PARAFAC peaks, a step towards fluorophore and cohort identification in the terrigenous DOM spectrum. Given the geoscience explosion in data volume and data complexity we feel these results should survive beyond the end point of a journal article. We are building a cloud-based Library on the Microsoft Azure platform to support this and subsequent analyses to enable data and methods to carry over and benefit other research groups and objectives.

Visible light photodegradation of phenanthrene catalyzed by Fe(III)-smectite: role of soil organic matter.

PubMed

Jia, Hanzhong; Li, Li; Fan, Xiaoyun; Liu, Mingdeng; Deng, Wenye; Wang, Chuanyi

2013-07-15

In the present study, phenanthrene is employed as a model to explore the roles played by three soil organic matter (SOM) fractions, i.e., dissolved organic matter (DOM), humic acid (HA), and fulvic acid (FA), in its photodegradation with assistance of Fe(III)-smectite under visible-light. Slight decrease in phenanthrene photodegradation rate was observed in the presence of DOM, which is explained in terms of oxidative-radical competition between DOM and target phenanthrene molecules due to the high electron-donor capacity of phenolic moieties in DOM. On the other hand, a critic content is observed with FA (0.70mg/g) and HA (0.65mg/g). Before reaching the critic content, the removal of phenanthrene is accelerated; while after that, the photodegradation rate is suppressed. The acceleration of phenanthrene degradation can be attributed to the photosensitization of FA and HA. Due to the strong interaction between phenanthrene and the phenyl rings, however, the retention of phenanthrene on SOM-Fe(III)-smectite in the presence of high content of HA or FA is enhanced, thus slowing down its photodegradation. Those observations provide valuable insights into the transformation and fate of PAHs in the natural soil environment and open a window for using clay-humic substances complexes for remediation of contaminated soil. Copyright © 2013 Elsevier B.V. All rights reserved.

Selective Leaching of Dissolved Organic Matter From Alpine Permafrost Soils on the Qinghai-Tibetan Plateau

NASA Astrophysics Data System (ADS)

Wang, Yinghui; Xu, Yunping; Spencer, Robert G. M.; Zito, Phoebe; Kellerman, Anne; Podgorski, David; Xiao, Wenjie; Wei, Dandan; Rashid, Harunur; Yang, Yuanhe

2018-03-01

Ongoing global temperature rise has caused significant thaw and degradation of permafrost soils on the Qinghai-Tibetan Plateau (QTP). Leaching of organic matter from permafrost soils to aquatic systems is highly complex and difficult to reproduce in a laboratory setting. We collected samples from natural seeps of active and permafrost layers in an alpine swamp meadow on the QTP to shed light on the composition of mobilized dissolved organic matter (DOM) by combining optical measurements, ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry, radiocarbon (14C), and solid-state 13C nuclear magnetic resonance spectroscopy. Our results show that even though the active layer soils contain large amounts of proteins and carbohydrates, there is a selective release of aromatic components, whereas in the deep permafrost layer, carbohydrate and protein components are preferentially leached during the thawing process. Given these different chemical characteristics of mobilized DOM, we hypothesize that photomineralization contributes significantly to the loss of DOM that is leached from the seasonally thawed surface layer. However, with continued warming, biodegradation will become more important since biolabile materials such as protein and carbohydrate are preferentially released from deep-layer permafrost soils. This transition in DOM leachate source and associated chemical composition has ramifications for downstream fluvial networks on the QTP particularly in terms of processing of carbon and associated fluxes.

What Do We Know about DOM Chemical Composition Based on Its Optical Properties?

NASA Astrophysics Data System (ADS)

Aiken, G.

2016-02-01

Dissolved organic matter (DOM) optical measurements (UV-Vis light absorbance and fluorescence) provide useful information related to DOM composition and reactivity, and can serve as proxies for DOM concentration and the concentrations of some metals, such as mercury. While these measurements are useful for a range of objectives, they only measure aromatic molecules that absorb UV-Vis light and a smaller subset of these molecules that fluoresce. They provide no information about the substantial fraction of DOM that is non-chromophoric. Based on chromatographic fractionation on XAD resins, DOM optical properties measured on whole water samples strongly correlate with both the concentration and composition of the hydrophobic acid (HPOA) fraction of the DOM. In this presentation the results of DOM optical measurements, DOM fractionation analyses, and 13C-nuclear magnetic resonance (NMR) and ultrahigh-resolution mass spectrometry (FTICR_MS) of HPOA fractions obtained from a wide range a natural waters will be presented to examine the relationships between DOM optical properties and DOM chemical composition. The HPOA fractions within and between rivers exhibit a wide range of optical behaviors reflective of sources and transformations compared to other DOM fractions. While, 13C-NMR and FTICR-MS analyses generally show greater relative concentrations of aromatic molecules for those samples with strong optical signals, they also indicate that the HPOA fractions are mostly composed of a large number of non-chromophoric molecules, such as carbohydrates carboxyl-rich alicyclic molecules (CRAM), and other aliphatic molecules, all of which have implications regarding DOM reactivity, biolability, sources, and age. The utility and short-comings of employing optical data for assessing sources and transformations of DOM in natural waters will be examined using case studies involving organic matter in the Yukon River Basin and riverine export of DOM to the Gulf of Maine.

Lability of High Molecular Weight Dissolved Organic Matter Polysaccharides Increases with Mild Acid or Base Treatment.

NASA Astrophysics Data System (ADS)

Pedler Sherwood, B.; Sosa, O.; Nelson, C. E.; Repeta, D.; DeLong, E.

2016-02-01

Approximately 662 Pg of dissolved organic carbon (DOC) has accumulated in the global ocean, yet the biological and chemical constraints on DOC turnover remain poorly understood. High molecular weight dissolved organic matter (HMWDOM) is largely comprised of semi-labile polysaccharides. These polysaccharides resist degradation even in the presence of nutrient amendments, suggesting unknown factors of polysaccharide composition affect microbial degradation. In a series of microcosm incubations conducted at station ALOHA in the North Pacific Subtropical Gyre, we tested the affect of mild base (KOH-DOM) and acid (HCl-DOM) treatments on polysaccharide lability. KOH-DOM, HCl-DOM, and untreated HMWDOM was added to seawater from the deep chlorophyll maximum and 200m. Microcosms amended with KOH-DOM and HCl-DOM yielded higher bacterial abundance and greater carbon drawdown relative to untreated HMWDOM and unamended controls. Microcosms amended with KOH-DOM and HCl-DOM also showed significant production of fluorescent DOM (fDOM), whereas untreated HMWDOM and unamended controls showed a net decrease in fDOM as measured by parallel factor analysis of DOM excitation-emission spectra. Metagenomic analyses revealed that microcosms amended with untreated HMWDOM and controls became dominated by Alteromonas genera ( 60% total sequence reads). In contrast, KOH-DOM and HCl-DOM amended microcosms yielded greater bacterial diversity; Alteromonas genera comprised 25% of sequence reads, with differences primarily accounted for by proportional increases in vibrio, roseobacter, rugeria and marinomonas clades. Transcriptomic analyses identified differential gene expression during growth on each DOM fraction. This study provides new insight into specific chemical moieties that may limit the bacterial degradation rate of semi-labile HMWDOM in the ocean.

Influence of dissolved organic matter character on mercury incorporation by planktonic organisms: an experimental study using oligotrophic water from Patagonian lakes

USGS Publications Warehouse

Diéguez, Maria C.; Queimaliños, Claudia P.; Guevara, Sergio Ribeiro; Marvin-DiPasquale, Mark C.; Cárdenas, Carolina Soto; Arribére, María A.

2013-01-01

Ligands present in dissolved organic matter (DOM) form complexes with inorganic divalent mercury (Hg2+) affecting its bioavailability in pelagic food webs. This investigation addresses the influence of a natural gradient of DOM present in Patagonian lakes on the bioaccumulation of Hg2+ (the prevailing mercury species in the water column of these lakes) by the algae Cryptomonas erosa and the zooplankters Brachionus calyciflorus and Boeckella antiqua. Hg2+ accumulation was studied through laboratory experiments using natural water of four oligotrophic Patagonian lakes amended with197Hg2+. The bioavailability of Hg2+ was affected by the concentration and character of DOM. The entrance of Hg2+ into pelagic food webs occurs mostly through passive and active accumulation. The incorporation of Hg2+ by Cryptomonas, up to 27% of the Hg2+ amended, was found to be rapid and dominated by passive adsorption, and was greatest when low molecular weight compounds with protein-like or small phenolic signatures prevailed in the DOM. Conversely, high molecular weight compounds with a humic or fulvic signature kept Hg2+ in the dissolved phase, resulting in the lowest Hg2+ accumulation in this algae. In Brachionus and Boeckella the direct incorporation of Hg from the aqueous phase was up to 3% of the Hg2+ amended. The dietary incorporation of Hg2+ by Boeckella exceeded the direct absorption of this metal in natural water, and was remarkably similar to the Hg2+ adsorbed in their prey. Overall, DOM concentration and character affected the adsorption of Hg2+ by algae through competitive binding, while the incorporation of Hg2+ into the zooplankton was dominated by trophic or dietary transfer.

Parameterizing the binding properties of dissolved organic matter with default values skews the prediction of copper solution speciation and ecotoxicity in soil.

PubMed

Djae, Tanalou; Bravin, Matthieu N; Garnier, Cédric; Doelsch, Emmanuel

2017-04-01

Parameterizing speciation models by setting the percentage of dissolved organic matter (DOM) that is reactive (% r-DOM) toward metal cations at a single 65% default value is very common in predictive ecotoxicology. The authors tested this practice by comparing the free copper activity (pCu 2+  = -log 10 [Cu 2+ ]) measured in 55 soil sample solutions with pCu 2+ predicted with the Windermere humic aqueous model (WHAM) parameterized by default. Predictions of Cu toxicity to soil organisms based on measured or predicted pCu 2+ were also compared. Default WHAM parameterization substantially skewed the prediction of measured pCu 2+ by up to 2.7 pCu 2+ units (root mean square residual = 0.75-1.3) and subsequently the prediction of Cu toxicity for microbial functions, invertebrates, and plants by up to 36%, 45%, and 59% (root mean square residuals ≤9 %, 11%, and 17%), respectively. Reparametrizing WHAM by optimizing the 2 DOM binding properties (i.e., % r-DOM and the Cu complexation constant) within a physically realistic value range much improved the prediction of measured pCu 2+ (root mean square residual = 0.14-0.25). Accordingly, this WHAM parameterization successfully predicted Cu toxicity for microbial functions, invertebrates, and plants (root mean square residual ≤3.4%, 4.4%, and 5.8%, respectively). Thus, it is essential to account for the real heterogeneity in DOM binding properties for relatively accurate prediction of Cu speciation in soil solution and Cu toxic effects on soil organisms. Environ Toxicol Chem 2017;36:898-905. © 2016 SETAC. © 2016 SETAC.

Domain similarity based orthology detection.

PubMed

Bitard-Feildel, Tristan; Kemena, Carsten; Greenwood, Jenny M; Bornberg-Bauer, Erich

2015-05-13

Orthologous protein detection software mostly uses pairwise comparisons of amino-acid sequences to assert whether two proteins are orthologous or not. Accordingly, when the number of sequences for comparison increases, the number of comparisons to compute grows in a quadratic order. A current challenge of bioinformatic research, especially when taking into account the increasing number of sequenced organisms available, is to make this ever-growing number of comparisons computationally feasible in a reasonable amount of time. We propose to speed up the detection of orthologous proteins by using strings of domains to characterize the proteins. We present two new protein similarity measures, a cosine and a maximal weight matching score based on domain content similarity, and new software, named porthoDom. The qualities of the cosine and the maximal weight matching similarity measures are compared against curated datasets. The measures show that domain content similarities are able to correctly group proteins into their families. Accordingly, the cosine similarity measure is used inside porthoDom, the wrapper developed for proteinortho. porthoDom makes use of domain content similarity measures to group proteins together before searching for orthologs. By using domains instead of amino acid sequences, the reduction of the search space decreases the computational complexity of an all-against-all sequence comparison. We demonstrate that representing and comparing proteins as strings of discrete domains, i.e. as a concatenation of their unique identifiers, allows a drastic simplification of search space. porthoDom has the advantage of speeding up orthology detection while maintaining a degree of accuracy similar to proteinortho. The implementation of porthoDom is released using python and C++ languages and is available under the GNU GPL licence 3 at http://www.bornberglab.org/pages/porthoda .

Mercury in a stream-lake network of Andean Patagonia (Southern Volcanic Zone): Partitioning and interaction with dissolved organic matter.

PubMed

Soto Cárdenas, Carolina; Diéguez, María Del Carmen; Queimaliños, Claudia; Rizzo, Andrea; Fajon, Vesna; Kotnik, Jože; Horvat, Milena; Ribeiro Guevara, Sergio

2018-04-01

Lake Nahuel Huapi (NH) is a large, ultraoligotrophic deep system located in Nahuel Huapi National Park (NHNP) and collecting a major headwater network of Northwestern Patagonia (Argentina). Brazo Rincón (BR), the westernmost branch of NH, is close to the active volcanic formation Puyehue-Cordón Caulle. In BR, aquatic biota and sediments display high levels of total Hg (THg), ranging in contamination levels although it is an unpolluted region. In this survey, Hg species and fractionation were assessed in association with dissolved organic matter (DOM) in several aquatic systems draining to BR. THg varied between 16.8 and 363 ng L -1 , with inorganic Hg (Hg 2+ ) contributing up to 99.8% and methyl mercury (MeHg) up to 2.10%. DOC levels were low (0.31-1.02 mg L -1 ) resulting in high THg:DOC and reflecting in high Hg 2+ availability for binding particles (partitioning coefficient log K d up to 6.03). In streams, Hg fractionation and speciation related directly with DOM terrestrial prints, indicating coupled Hg-DOM inputs from the catchment. In the lake, DOM quality and photochemical and biological processing drive Hg fractionation, speciation and vertical levels. Dissolved gaseous Hg (Hg 0 ) reached higher values in BR (up to 3.8%), particularly in upper lake layers where solar radiation enhances the photoreduction of Hg 2+ and Hg-DOM complexes. The environmental conditions in BR catchment promote Hg 2+ binding to abiotic particles and bioaccumulation and the production of Hg 0 , features enhancing Hg mobilization among ecosystem compartments. Overall, the aquatic network studied can be considered a "natural Hg hotspot" within NHNP. Copyright © 2018 Elsevier Ltd. All rights reserved.

A statistic-thermodynamic model for the DOM degradation in the estuary

NASA Astrophysics Data System (ADS)

Zheng, Quanan; Chen, Qin; Zhao, Haihong; Shi, Jiuxin; Cao, Yong; Wang, Dan

2008-03-01

This study aims to clarify the role of dissolved salts playing in the degradation process of terrestrial dissolved organic matter (DOM) at a scale of molecular movement. The molecular thermal movement is perpetual motion. In a multi-molecular system, this random motion also causes collision between the molecules. Seawater is a multi-molecular system consisting from water, salt, and terrestrial DOM molecules. This study attributes the DOM degradation in the estuary to the inelastic collision of DOM molecule with charged salt ions. From statistic-thermodynamic theories of molecular collision, the DOM degradation model and the DOM distribution model are derived. The models are validated by the field observations and satellite data. Thus, we conclude that the inelastic collision between the terrestrial DOM molecules and dissolved salt ions in seawater is a decisive dynamic mechanism for rapid loss of terrestrial DOM.

Tracking the evolution of stream DOM source during storm events using end member mixing analysis based on DOM quality

NASA Astrophysics Data System (ADS)

Yang, Liyang; Chang, Soon-Woong; Shin, Hyun-Sang; Hur, Jin

2015-04-01

The source of river dissolved organic matter (DOM) during storm events has not been well constrained, which is critical in determining the quality and reactivity of DOM. This study assessed temporal changes in the contributions of four end members (weeds, leaf litter, soil, and groundwater), which exist in a small forested watershed (the Ehwa Brook, South Korea), to the stream DOM during two storm events, using end member mixing analysis (EMMA) based on spectroscopic properties of DOM. The instantaneous export fluxes of dissolved organic carbon (DOC), chromophoric DOM (CDOM), and fluorescent components were all enhanced during peak flows. The DOC concentration increased with the flow rate, while CDOM and humic-like fluorescent components were diluted around the peak flows. Leaf litter was dominant for the DOM source in event 2 with a higher rainfall, although there were temporal variations in the contributions of the four end members to the stream DOM for both events. The contribution of leaf litter peaked while that of deeper soils decreased to minima at peak flows. Our results demonstrated that EMMA based on DOM properties could be used to trace the DOM source, which is of fundamental importance for understanding the factors responsible for river DOM dynamics during storm events.

Impacts of global changes on the biogeochemistry and environmental effects of dissolved organic matter at the land-ocean interface: a review.

PubMed

Zhuang, Wan-E; Yang, Liyang

2018-02-01

Dissolved organic matter (DOM) is an important component in the biogeochemistry and ecosystem function of aquatic environments at the highly populated land-ocean interface. The mobilization and transformation of DOM at this critical interface are increasingly affected by a series of notable global changes such as the increasing storm events, intense human activities, and accelerating glacier loss. This review provides an overview of the changes in the quantity and quality of DOM under the influences of multiple global changes. The profound implications of changing DOM for aquatic ecosystem and human society are further discussed, and future research needs are suggested for filling current knowledge gaps. The fluvial export of DOM is strongly intensified during storm events, which is accompanied with notable changes in the chemical composition and reactivity of DOM. Land use not only changes the mobilization of natural DOM source pools within watersheds but also adds DOM of distinct chemical composition and reactivity from anthropogenic sources. Glacier loss brings highly biolabile DOM to downstream water bodies. The changing DOM leads to significant changes in heterotrophic activity, CO 2 out gassing, nutrient and pollutant biogeochemistry, and disinfection by-product formation. Further studies on the source, transformations, and downstream effects of storm DOM, temporal variations of DOM and its interactions with other pollutants in human-modified watersheds, photo-degradability of glacier DOM, and potential priming effects, are essential for better understanding the responses and feedbacks of DOM at the land-ocean interface under the impacts of global changes.

Changes in dissolved organic matter quality in a peatland and forest headwater stream as a function of seasonality and hydrologic conditions

NASA Astrophysics Data System (ADS)

Broder, Tanja; Knorr, Klaus-Holger; Biester, Harald

2017-04-01

Peatlands and peaty riparian zones are major sources of dissolved organic matter (DOM), but are poorly understood in terms of export dynamics and controls thereof. Thereby quality of DOM affects function and behavior of DOM in aquatic ecosystems, but DOM quality can also help to track DOM sources and their export dynamics under specific hydrologic preconditions. The objective of this study was to elucidate controls on temporal variability in DOM concentration and quality in stream water draining a bog and a forested peaty riparian zone, particularly considering drought and storm flow events. DOM quality was monitored using spectrofluorometric indices for aromaticity (SUVA254), apparent molecular size (SR) and precursor organic material (FI), as well as PARAFAC modeling of excitation emission matrices (EEMs). Indices for DOM quality exhibited major changes due to different hydrologic conditions, but patterns were also dependent on season. Stream water at the forested site with mineral, peaty soils generally exhibited higher variability in DOM concentrations and quality compared to the outflow of an ombrotrophic bog, where DOM was less susceptible to changes in hydrologic conditions. During snowmelt and spring events, near-surface protein-like DOM pools were exported. A microbial DOM fraction originating from groundwater and deep peat layers was increasing during drought, while a strongly microbially altered DOM fraction was also exported by discharge events with dry preconditions at the forested site. This might be due to accelerated microbial activity in the peaty riparian zone of the forested site under these preconditions. Our study demonstrated that DOM export dynamics are not only a passive mixing of different hydrological sources, but monitoring studies have to consider that DOM quality depends on hydrologic preconditions and season. Moreover, the forested peaty riparian zone generated the most variability in headwater DOM quantity and quality, as could be tracked by the used spectrofluorometric indices.

The Taili-Yiwulüshan metamorphic core complex corridor: Diachronous exhumation and relationships to the adjacent basins based on new 40Ar/39Ar and (U-Th-Sm)/He mineral ages

NASA Astrophysics Data System (ADS)

Liang, Chenyue; Neubauer, Franz; Liu, Yongjiang; Genser, Johann; Dunkl, István; Heberer, Bianca; Jin, Wei; Zeng, Zuoxun; Li, Weimin; Wen, Quanbo; Li, Jing

2015-04-01

The Xingcheng-Taili ductile shear zone (western Liaoning Province in China) formed during latest Jurassic to Early Cretaceous crustal extension of the eastern North China craton, and exhumed low to medium metamorphic grade Archean, Upper Triassic and Upper Jurassic granitic rocks. The Mesozoic Yiwulüshan metamorphic core complex (Yiwulüshan MCC) is dominated by a NNE-SSW elongated dome with a left-lateral shear zone, which is located in the northeastern part of Xingcheng-Taili ductile shear zone, and combine as Taili-Yiwulüshan metamorphic core complex corridor. To the east, it is bounded by the NNE-trending Cretaceous to Eocene Liaohe basin (the northern extension of the Bohai Bay basin), and to the west by the Cretaceous-aged Fuxin-Yixian basin, which could potentially interpreted as supra-detachment basins. Here, we present results from a multi-method thermochronological study and coupled with structural investigations and sections of adjacent supra-detachment basins, which constrain the timing of regional deformation as well as the cooling history and exhumation processes of the low- to middle-grade metamorphic complex in the Taili-Yiwulüshan MCC corridor, in order to understand the mode of lithospheric scale reactivation, extension and thinning of the North China craton. The new40Ar/39Ar muscovite, biotite, K-feldspar and (U-Th)/He apatite ages from granitic rocks help constrain the thermal evolution during its exhumation. The thermochronologic studies have shown at least three stages of exhumation and cooling from late Jurassic to Eocene in Xingcheng-Taili shear zone should be distinguished, e.g., ~ 150-130 Ma, 130-115 Ma and 115-52 Ma, respectively. Diachronous onset and subsequent parallel cooling and exhumation characterize the early thermal history. The Yiwulüshan MCC has a similar exhumation history from 135 to 97 Ma with a similar cooling history. The development of Taili-Yiwulüshan MCC corridor is associated with synkinematic emplacement, exhumation, and volcanic-clastic deposition in the supra-detachment basins. Initiation of the unroofing history resulted from ductile left-lateral shearing since latest Jurassic times. Diachronous onset and subsequent cooling and exhumation characterize the early thermal history. The second and third stages of cooling started lasted until the recently active faulting. Start form the Early Cretaceous the detachment shear zone truncating by the later brittle normal fault. The (U-Th)/He age of 52.3 ± 4.7 Ma indicating final Eocene exhumation of the Taili area is consistent with normal faulting in the Bohai basin area in the east. Based on the present results and published information, that Cretaceous WNW-ESE extensional deformation and lithosphere thinning in the Taili-Yiwulüshan corridor and throughout the eastern North China craton, the synchroneity of cooling and exhumation of metamorphic core complexes, the formation of supra-detachment basins, and regional alkaline igneous activity reflects Early Cretaceous regional extensional tectonics , possibly resulting from roll-back of the subducted Pacific plate beneath North China Craton.

The Bossoroca Complex, São Gabriel Terrane, Dom Feliciano Belt, southernmost Brazil: Usbnd Pb geochronology and tectonic implications for the neoproterozoic São Gabriel Arc

NASA Astrophysics Data System (ADS)

Gubert, Mauricio Lemos; Philipp, Ruy Paulo; Stipp Basei, Miguel Angelo

2016-10-01

Usbnd Pb LA-ICPMS geochronological analyses were carried out on zircon grains from metavolcanic rocks of the Bossoroca Complex and for one ash tuff of the Acampamento Velho Formation of the Camaquã Basin, in order to understand the evolution of the Neoproterozoic São Gabriel magmatic arc. A total of 42 analyses of igneous zircon grains were performed in three samples. The results yielded Usbnd Pb ages of 767.2 ± 2.9 Ma for the metavolcanic agglomerate (BOS-02); 765 ± 10 Ma for the metacrystal tuff (BOS-03) and 565.8 ± 4.8 Ma for the ash tuff (BOS-04). The Orogenic Cycle in Brazil is characterized by a set of orogenic belts consisting of petrotectonic associations juxtaposed by two collisional events that occurred at the end of the Neoproterozoic. In southern Brazil this orogeny formed the Dom Feliciano Belt, a unit composed of associations of rocks developed during two major orogenic events called São Gabriel (900-680 Ma) and Dom Feliciano (650-540 Ma). The main São Gabriel associations are tectonically juxtaposed as elongated strips according to the N20-30°E direction, bounded by ductile shear zones. The Bossoroca Complex comprises predominantly metavolcano-sedimentary rocks, characterized by medium-K calc-alkaline association generated in a cordillera-type magmatic arc. The volcanism occurred in sub-aerial environment, developing deposits generated by flow, resurgence and fall, sporadically interrupted by subaqueous epiclastic deposits, suggesting an arc related basin. The São Gabriel Terrane contains the petrotectonic units that represent the closure of the Charrua Ocean associated to the subduction period of the Brasiliano Orogenic Cycle in the Sul-rio-grandense Shield.

Molecular Insights on Dissolved Organic Matter Transformation by Supraglacial Microbial Communities.

PubMed

Antony, Runa; Willoughby, Amanda S; Grannas, Amanda M; Catanzano, Victoria; Sleighter, Rachel L; Thamban, Meloth; Hatcher, Patrick G; Nair, Shanta

2017-04-18

Snow overlays the majority of Antarctica and is an important repository of dissolved organic matter (DOM). DOM transformations by supraglacial microbes are not well understood. We use ultrahigh resolution mass spectrometry to elucidate molecular changes in snowpack DOM by in situ microbial processes (up to 55 days) in a coastal Antarctic site. Both autochthonous and allochthonous DOM is highly bioavailable and is transformed by resident microbial communities through parallel processes of degradation and synthesis. DOM thought to be of a more refractory nature, such as dissolved black carbon and carboxylic-rich alicyclic molecules, was also rapidly and extensively reworked. Microbially reworked DOM exhibits an increase in the number and magnitude of N-, S-, and P-containing formulas, is less oxygenated, and more aromatic when compared to the initial DOM. Shifts in the heteroatom composition suggest that microbial processes may be important in the cycling of not only C, but other elements such as N, S, and P. Microbial reworking also produces photoreactive compounds, with potential implications for DOM photochemistry. Refined measurements of supraglacial DOM and their cycling by microbes is critical for improving our understanding of supraglacial DOM cycling and the biogeochemical and ecological impacts of DOM export to downstream environments.

[Absorption and fluorescence characteristics of dissolved organic matter (DOM) in rainwater and sources analysis in summer and winter season].

PubMed

Liang, Jian; Jiang, Tao; WeiI, Shi-Qiang; Lu, Song; Yan, Jin-Long; Wang, Qi-Lei; Gao, Jie

2015-03-01

This study aimed at evaluating the variability of the optical properties including UV-Vis and fluorescence characteristics of dissolved organic matter (DOM) from rainwater in summer and winter seasons. UV-Vis and fluorescence spectroscopy, together with Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model and fire events map, were conducted to characterize DOM and investigate its sources and contributions. The results showed that as compared with aquatic and soil DOM, rainwater DOM showed similar spectral characteristics, suggesting DOM in precipitation was also an important contributor to DOM pool in terrestrial and aquatic systems. The concentrations of DOC in rainwater were 0.88-12.80 mg x L(-1), and the CDOM concentrations were 3.17-21.11 mg x L(-1). Differences of DOM samples between summer and winter were significant (P < 0.05). In comparison to summer, DOM samples in winter had lower molecular weight and aromaticity, and also lower humification. Input of DOM in winter was predominantly derived from local and short-distance distances, while non-special scattering sources were identified as the main contributors in summer. Although absorption and fluorescence spectroscopy could be used to identify DOM composition and sources, there were obvious differences in spectra and sources analysis between rainwater DOM and the others from other sources. Thus, the classic differentiation method by "allochthonous (terrigenous) and autochthonous (authigenic)" is possibly too simple and arbitrary for characterization of DOM in rainwater.

Seasonal and air mass trajectory effects on dissolved organic matter of bulk deposition at a coastal town in south-western Europe.

PubMed

Santos, Patrícia S M; Santos, Eduarda B H; Duarte, Armando C

2013-01-01

Rainwater contains a complex mixture of organic compounds which may influence climate, terrestrial and maritime ecosystems and thus human health. In this work, the characteristics of DOM of bulk deposition at a coastal town on the southwest of Europe were assessed by UV-visible and three-dimensional excitation-emission matrix fluorescence spectroscopies and by dissolved organic carbon (DOC) content. The seasonal and air mass trajectory effects on dissolved organic matter (DOM) of bulk deposition were evaluated. The absorbance at 250 nm (UV(250 nm)) and integrated fluorescence showed to be positively correlated with each other, and they were also positively correlated to the DOC in bulk deposition, which suggest that a constant fraction of DOM is likely to fluoresce. There was more chromophoric dissolved organic matter (CDOM) present in summer and autumn seasons than in winter and spring. Bulk deposition associated with terrestrial air masses contained a higher CDOM content than bulk deposition related to marine air masses, thus highlighting the contribution of terrestrial/anthropogenic sources.

XML schemas for common bioinformatic data types and their application in workflow systems

PubMed Central

Seibel, Philipp N; Krüger, Jan; Hartmeier, Sven; Schwarzer, Knut; Löwenthal, Kai; Mersch, Henning; Dandekar, Thomas; Giegerich, Robert

2006-01-01

Background Today, there is a growing need in bioinformatics to combine available software tools into chains, thus building complex applications from existing single-task tools. To create such workflows, the tools involved have to be able to work with each other's data – therefore, a common set of well-defined data formats is needed. Unfortunately, current bioinformatic tools use a great variety of heterogeneous formats. Results Acknowledging the need for common formats, the Helmholtz Open BioInformatics Technology network (HOBIT) identified several basic data types used in bioinformatics and developed appropriate format descriptions, formally defined by XML schemas, and incorporated them in a Java library (BioDOM). These schemas currently cover sequence, sequence alignment, RNA secondary structure and RNA secondary structure alignment formats in a form that is independent of any specific program, thus enabling seamless interoperation of different tools. All XML formats are available at , the BioDOM library can be obtained at . Conclusion The HOBIT XML schemas and the BioDOM library simplify adding XML support to newly created and existing bioinformatic tools, enabling these tools to interoperate seamlessly in workflow scenarios. PMID:17087823

Photochemical reactions between mercury (Hg) and dissolved organic matter decrease Hg bioavailability and methylation

DOE PAGES

Luo, Hong-Wei; Yin, Xiangping; Jubb, Aaron M.; ...

2016-11-09

Atmospheric deposition of mercury (Hg) to surface water is one of the dominant sources of Hg in aquatic environments and ultimately drives methylmercury (MeHg) toxin accumulation in fish. It is known that freshly deposited Hg is more readily methylated by microorganisms than aged or preexisting Hg; however the underlying mechanism of this process is unclear. Here we report that Hg bioavailability is decreased by photochemical reactions between Hg and dissolved organic matter (DOM) in water. Photo-irradiation of Hg-DOM complexes results in loss of Sn(II)-reducible (i.e. reactive) Hg and up to an 80% decrease in MeHg production by the methylating bacteriummore » Geobacter sulfurreducens PCA. Loss of reactive Hg proceeded at a faster rate with a decrease in the Hg to DOM ratio and is attributed to the possible formation of mercury sulfide (HgS). Lastly, these results suggest a new pathway of abiotic photochemical formation of HgS in surface water and provide a mechanism whereby freshly deposited Hg is readily methylated but, over time, progressively becomes less available for microbial uptake and methylation.« less

Photochemical reactions between mercury (Hg) and dissolved organic matter decrease Hg bioavailability and methylation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Hong-Wei; Yin, Xiangping; Jubb, Aaron M.

Atmospheric deposition of mercury (Hg) to surface water is one of the dominant sources of Hg in aquatic environments and ultimately drives methylmercury (MeHg) toxin accumulation in fish. It is known that freshly deposited Hg is more readily methylated by microorganisms than aged or preexisting Hg; however the underlying mechanism of this process is unclear. Here we report that Hg bioavailability is decreased by photochemical reactions between Hg and dissolved organic matter (DOM) in water. Photo-irradiation of Hg-DOM complexes results in loss of Sn(II)-reducible (i.e. reactive) Hg and up to an 80% decrease in MeHg production by the methylating bacteriummore » Geobacter sulfurreducens PCA. Loss of reactive Hg proceeded at a faster rate with a decrease in the Hg to DOM ratio and is attributed to the possible formation of mercury sulfide (HgS). Lastly, these results suggest a new pathway of abiotic photochemical formation of HgS in surface water and provide a mechanism whereby freshly deposited Hg is readily methylated but, over time, progressively becomes less available for microbial uptake and methylation.« less

Is the molecular diversity of marine dissolved organic matter already imprinted in the exometabolome of single strains?

NASA Astrophysics Data System (ADS)

Noriega-Ortega, B. E.; Wienhausen, G.; Dittmar, T.; Simon, M.; Niggemann, J.

2016-02-01

Dissolved organic matter (DOM) in the ocean, the marine geometabolome, is an extremely complex mixture composed of a wide variety of compounds. The molecular chemodiversity affects the function and turnover rate of DOM in the ocean. We hypothesize that the active microbial community essentially contributes to the complexity of the DOM pool through uptake and excretion of compounds. We tested this hypothesis in culture experiments with fully-sequenced strains of the Roseobacter clade. Bacteria of the Roseobacter clade are among the most abundant microbial players in the ocean. We studied the exometabolome of two representatives of the Roseobacter clade, Phaeobacter inhibens DSM 17395 and Dinoroseobacter shibae. The organisms were grown separately in cultures on defined single model substrates (acetate, succinate, glutamate, glucose). We used a non-targeted analytical approach via Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) to characterize the exometabolome at the molecular level, complemented by compound-specific analyses of free and combined amino acids and carbohydrates. The exometabolome composition varied between the tested strains, which released a different suite of compounds depending on the growth phase as well as on growth conditions (substrate). Both organisms exhibited a core exometabolome with compounds released when growing on either substrate and at all growth phases, and a variable exometabolome specific for different substrates and growth phases. However, only a small fraction of the exometabolites detected by FT-ICR-MS could be directly linked to the genome or transcriptome. We interpret these findings as evidence for the excretion of molecularly highly-diverse metabolic waste, whose composition is dependent on the metabolic state and genetic repertoire of the organisms. The molecular diversity of compounds excreted by a single strain is extraordinary and is likely the reason for the molecular diversity of natural DOM in the ocean.

New U-Pb zircon age data on polyphase plutono-metamorphic complex in western Enderby Land (East Antarctica) and its implications for Neoproterozoic amalgamation of the Gondwanaland

NASA Astrophysics Data System (ADS)

Mikhalskii, Evgenii; Krylov, Dmitriy; Rodionov, Nikolay

2017-04-01

Western Enderby Land occupies a key position on Gondwanaland reconstructions near India - Sri Lanka - Antarctica junction and eastwards the Lützow-Holm Bay metamorphic complex commonly identified as a Cambrian suture zone. We present U-Pb zircon isotopic age determinations with SHRIMP II obtained on tonalite- to granite-gneiss samples from the Thala Hills and the Polkanova Hills. In the Thala Hills three high-temperature tectonomagmatic episodes may be distinguished at ca 980-970 Ma, ca 780-720 Ma, and ca 545-530 Ma. All of them included sin-kinematic granitic orthogneiss protolith emplacements and high-grade metamorphism. In the Polkanova Hills tonalitic to granodioritic orthogneisses, intercalated with prevailing amphibolites, were emplaced during ca 980-950 Ma episode (or at both of these ages) and subsequently metamorphosed under amphibolite facies accompanied by migmatization at ca 600-530 Ma. The ca 980-950 Ma event corresponds to the Rayner Structural Episode which affected much of East Antarctica, including Sør Rondane Mountains to the west and Kemp Land to the east of study area. The Polkanova Hills area is underlain by basic amphibolites and tonalitic to granodioritic orthogneisses characterized by LILE enrichment and Nb-Ta troughs in a primitive mantle normalized spiderdiagram suggestive of derivation in arc-related convergent palaeotectonic environments. Co-eval orthogneisses in the Thala Hills are characterized by granitic compositions and occur in intercalation with paragneisses, which points out to more in-land palaeotectonic environments. The ca 780-720 Ma episode included two events at ca 780 Ma (high-grade anatexis) and 720 Ma (sin-tectonic granitoid emplacement) and was roughly co-eval with magmatic and/or metamorphic events in Dronning Maud Land of East Antarctica as well as in other Gondwanaland regions, like Madagascar, Sri Lanka and eastern Africa. The ca 780-720 Ma episode (Thala Episode) may be correlated with the East African Orogeny. Our new data provide a correlation of both ca 980-950 Ma and ca 800-700 Ma events between western Enderby Land and (partly) Dronning Maud Land, thus indicating their conjugate positions in the early Neoproterozoic, which in turn argues against a late Neoproterozoic-Cambrian suture running between them (i.e., the Lützow-Holm Bay Complex). We suggest that these terrains were juxtaposed prior to final amalgamation of the Gondwanaland. The Polkanova Hills basic to intermediate protoliths may represent a Rayner-aged active continental margin. The Late Neoproterozoic - Cambrian (ca 600-530 Ma) episode was manifested by high-grade anatexis (under granulite facies in the Thala Hills and amphibolite facies in the Polkanova Hills) co-eval with the Lützow-Holm Bay metamorphic complex. However, the nature of this metamorphism yet seems to have not been understood well and we believe it was of within-plate rather than continent collision origin. This study was supported by the RFBR grant #15-05-02761 to EVM.

Concurrent photolytic degradation of aqueous methylmercury and dissolved organic matter

USGS Publications Warehouse

Fleck, Jacob A.; Gill, Gary W.; Bergamaschi, Brian A.; Kraus, Tamara E.C.; Downing, Bryan D.; Alpers, Charles N.

2014-01-01

Monomethyl mercury (MeHg) is a potent neurotoxin that threatens ecosystem viability and human health. In aquatic systems, the photolytic degradation of MeHg (photodemethylation) is an important component of the MeHg cycle. Dissolved organic matter (DOM) is also affected by exposure to solar radiation (light exposure) leading to changes in DOM composition that can affect its role in overall mercury (Hg) cycling. This study investigated changes in MeHg concentration, DOM concentration, and the optical signature of DOM caused by light exposure in a controlled field-based experiment using water samples collected from wetlands and rice fields. Filtered water from all sites showed a marked loss in MeHg concentration after light exposure. The rate of photodemethylation was 7.5 × 10-3 m2 mol-1 (s.d. 3.5 × 10-3) across all sites despite marked differences in DOM concentration and composition. Light exposure also caused changes in the optical signature of the DOM despite there being no change in DOM concentration, indicating specific structures within the DOM were affected by light exposure at different rates. MeHg concentrations were related to optical signatures of labile DOM whereas the percent loss of MeHg was related to optical signatures of less labile, humic DOM. Relationships between the loss of MeHg and specific areas of the DOM optical signature indicated that aromatic and quinoid structures within the DOM were the likely contributors to MeHg degradation, perhaps within the sphere of the Hg-DOM bond. Because MeHg photodegradation rates are relatively constant across freshwater habitats with natural Hg–DOM ratios, physical characteristics such as shading and hydrologic residence time largely determine the relative importance of photolytic processes on the MeHg budget in these mixed vegetated and open-water systems.

Concurrent photolytic degradation of aqueous methylmercury and dissolved organic matter.

PubMed

Fleck, Jacob A; Gill, Gary; Bergamaschi, Brian A; Kraus, Tamara E C; Downing, Bryan D; Alpers, Charles N

2014-06-15

Monomethyl mercury (MeHg) is a potent neurotoxin that threatens ecosystem viability and human health. In aquatic systems, the photolytic degradation of MeHg (photodemethylation) is an important component of the MeHg cycle. Dissolved organic matter (DOM) is also affected by exposure to solar radiation (light exposure) leading to changes in DOM composition that can affect its role in overall mercury (Hg) cycling. This study investigated changes in MeHg concentration, DOM concentration, and the optical signature of DOM caused by light exposure in a controlled field-based experiment using water samples collected from wetlands and rice fields. Filtered water from all sites showed a marked loss in MeHg concentration after light exposure. The rate of photodemethylation was 7.5×10(-3)m(2)mol(-1) (s.d. 3.5×10(-3)) across all sites despite marked differences in DOM concentration and composition. Light exposure also caused changes in the optical signature of the DOM despite there being no change in DOM concentration, indicating specific structures within the DOM were affected by light exposure at different rates. MeHg concentrations were related to optical signatures of labile DOM whereas the percent loss of MeHg was related to optical signatures of less labile, humic DOM. Relationships between the loss of MeHg and specific areas of the DOM optical signature indicated that aromatic and quinoid structures within the DOM were the likely contributors to MeHg degradation, perhaps within the sphere of the Hg-DOM bond. Because MeHg photodegradation rates are relatively constant across freshwater habitats with natural Hg-DOM ratios, physical characteristics such as shading and hydrologic residence time largely determine the relative importance of photolytic processes on the MeHg budget in these mixed vegetated and open-water systems. Published by Elsevier B.V.

Contrasting effects of photochemical and microbial degradation on Cu(II) binding with fluorescent DOM from different origins.

PubMed

Xu, Huacheng; Guan, Dong-Xing; Zou, Li; Lin, Hui; Guo, Laodong

2018-08-01

Effects of photochemical and microbial degradation on variations in composition and molecular-size of dissolved organic matter (DOM) from different sources (algal and soil) and the subsequent influence on Cu(II) binding were investigated using UV-Vis, fluorescence excitation-emission matrices coupled with parallel factor analysis, flow field-flow fractionation (FlFFF), and metal titration. The degradation processes resulted in an initial rapid decline in the bulk dissolved organic carbon and chromophoric and fluorescent DOM components, followed by a small or little decrease. Specifically, photochemical reaction decreased the aromaticity, humification and apparent molecular weights of all DOM samples, whereas a reverse trend was observed during microbial degradation. The FlFFF fractograms revealed that coagulation of both protein- and humic-like DOM induced an increase in molecular weights for algal-DOM, while the molecular weight enhancement for allochthonous soil samples was mainly attributed to the self-assembly of humic-like components. The Cu(II) binding capacity of algal-derived humic-like and fulvic-like DOM consistently increased during photo- and bio-degradation, while the soil-derived DOM exhibited a slight decline in Cu(II) binding capacity during photo-degradation but a substantial increase during microbial degradation, indicating source- and degradation-dependent metal binding heterogeneities. Pearson correlation analysis demonstrated that the Cu(II) binding potential was mostly related with aromaticity and molecular size for allochthonous soil-derived DOM, but was regulated by both DOM properties and specific degradation processes for autochthonous algal-derived DOM. This study highlighted the coupling role of inherent DOM properties and external environmental processes in regulating metal binding, and provided new insights into metal-DOM interactions and the behavior and fate of DOM-bound metals in aquatic environments. Copyright © 2018 Elsevier Ltd. All rights reserved.

Effects of dissolved organic matter (DOM) sources and nature of solid extraction sorbent on recoverable DOM composition: Implication into potential lability of different compound groups.

PubMed

Chen, Meilian; Kim, Sunghwan; Park, Jae-Eun; Kim, Hyun Sik; Hur, Jin

2016-07-01

Noting the source-dependent properties of dissolved organic matter (DOM), this study explored the recoverable compounds by solid phase extraction (SPE) of two common sorbents (C18 and PPL) eluted with methanol solvent for contrasting DOM sources via fluorescence excitation-emission matrix coupled with parallel factor analysis (EEM-PARAFAC) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Fresh algae and leaf litter extracts DOM, one riverine DOM, and one upstream lacustrine DOM were selected for the comparison. C18 sorbent was generally found to extract more diverse molecular formula, relatively higher molecular weight, and more heteroatomic DOM compounds within the studied mass range than PPL sorbent except for the leaf litter extract. Even with the same sorbent, the main molecular features of the two end member DOM were distributed on different sides of the axes of a multivariate ordination, indicating the source-dependent characteristics of the recoverable compounds by the sorbents. In addition, further examination of the molecular formula uniquely present in the two end members and the upstream lake DOM suggested that proteinaceous, tannin-like, and heteroatomic DOM constituents might be potential compound groups which are labile and easily degraded during their mobilization into downstream watershed. This study provides new insights into the sorbent selectivity of DOM from diverse sources and potential lability of various compound groups.

Reactivity of Triplet Excited States of Dissolved Natural Organic Matter in Stormflow from Mixed-Use Watersheds.

PubMed

McCabe, Andrew J; Arnold, William A

2017-09-05

Dissolved organic matter (DOM) quantity and composition control the rate of formation (R f,T ) of triplet excited states of dissolved natural organic matter ( 3 DOM*) and the efficiency of 3 DOM* formation (the apparent quantum yield, AQY T ). Here, the reactivity of 3 DOM* in stormflow samples collected from watersheds with variable land covers is examined. Stormflow DOM reflects variability in DOM quantity and composition as a function of land cover and may be important in controlling the fate of cotransported pollutants. R f,T and AQY T were measured using 2,4,6-trimethylphenol in stormflow samples under simulated sunlight. The DOM source and composition was characterized using absorbance and fluorescence spectroscopies and high-resolution mass spectrometry. R f,T and the total rate of light absorption by the water samples (R a ) increased with the dissolved organic carbon (DOC) concentration. AQY T was independent of DOC concentration, but varied with DOM source: developed land cover (4-6%) ≈ open water > vegetated land cover (3%). AQY T was positively related to an index for microbial/algal DOM content and negatively related to DOM molecular weight, DOM aromaticity, and the content of polyphenols. This work demonstrates that TMP is an effective probe for the determination of R f,T and AQY T in whole water samples after accounting for the inhibition of TMP photodegradation by DOM.

Recent progress in recognition of UHP metamorphism in allochthons of the Scandinavian Caledonides (Seve Nappe Complex and Tromsø Nappe)

NASA Astrophysics Data System (ADS)

Janák, Marian; Ravna, Erling; Majka, Jarosław; Klonowska, Iwona; Kullerud, Kåre; Gee, David; Froitzheim, Nikolaus

2017-04-01

During the last ten years, UHP rocks have been discovered within far-travelled allochthons of the Scandinavian Caledonides including the Seve Nappe Complex (SNC) of the Middle Allochthon and Tromsø Nappe within the Uppermost Allochthon. The first evidence for UHP conditions in the SNC was documented in a kyanite-bearing eclogite dike within the Friningen garnet peridotite. Subsequently, UHP conditions were determined for phengite eclogite and garnet pyroxenite from Stor Jougdan and pelitic gneisses from Åreskutan. Finally, diamond was found in metasedimentary rocks of the SNC at three localities (Snasahögarna, Åreskutan and most recently near Saxnäs), c. 250 km apart, confirming regional UHP conditions within this allochthon. In the Tromsø Nappe (northern Norway), evidence for UHP metamorphism comes from phengite- and kyanite-bearing eclogites from Tønsvika and Tromsdalstind, and diamond-bearing gneisses from Tønsvika. Microdiamond occurs in-situ as single and composite (mostly with Mg-Fe carbonate) inclusions within garnet and zircon. The calculated P-T conditions for the diamond-bearing samples are 4.1-4.2 GPa/830-840°C (Åreskutan), and 3.5-4.0 GPa/ 750-800°C (Tønsvika), in the diamond stability field. The UHP metamorphism in the SNC and Tromsø Nappe is probably Late Ordovician (c. 460-450 Ma), i.e. c. 40-50 Ma older than that in the Western Gneiss Region of southwestern Norway. Whereas the latter occurred during the collision between Laurentia and Baltica in the Late Silurian to Early Devonian, the processes leading to Ordovician UHP metamorphism occurred during closure of the Iapetus Ocean and are less well understood. The occurrence of two UHP metamorphic events in the Scandinavian Caledonides implies subduction, exhumation, and re-subduction of continental crust. This is an observation that could be of importance for the understanding of orogeny at convergent plate boundaries in general. The following questions remain to be answered: (1) Was UHP metamorphism in the SNC related to continent-continent or arc-continent collision? (2) Which processes lead to the emplacement of peridotite bodies with subcontinental mantle affinity into Baltican continental crust? (3) Was the Tromsø Nappe of Laurentian origin, or a part of the Baltoscandian margin emplaced by out-of-sequence thrusting, or a terrane of unknown affinity? Therefore, it is important to constrain the areal extent, pressure-temperature conditions, timing, and kinematics of UHP metamorphism in these allochthonous units.

Detrital zircon analysis of Mesoproterozoic and neoproterozoic metasedimentary rocks of northcentral idaho: Implications for development of the Belt-Purcell basin

USGS Publications Warehouse

Lewis, R.S.; Vervoort, J.D.; Burmester, R.F.; Oswald, P.J.

2010-01-01

The authors analyzed detrital zircon grains from 10 metasedimentary rock samples of the Priest River complex and three other amphibolite-facies metamorphic sequences in north-central Idaho to test the previous assignment of these rocks to the Mesoproterozoic Belt-Purcell Supergroup. Zircon grains from two samples of the Prichard Formation (lower Belt) and one sample of Cambrian quartzite were also analyzed as controls with known depositional ages. U-Pb zircon analysis by laser ablation - inductively coupled plasma - mass spectrometry reveals that 6 of the 10 samples contain multiple age populations between 1900 and 1400 Ma and a scatter of older ages, similar to results reported from the Belt- Purcell Supergroup to the north and east. Results from the Priest River metamorphic complex confirm previous correlations with the Prichard Formation. Samples from the Golden and Elk City sequences have significant numbers of 1500-1380 Ma grains, which indicates that they do not predate the Belt. Rather, they are probably from a relatively young, southwestern part of the Belt Supergroup (Lemhi subbasin). Non-North American (1610-1490 Ma) grains are rare in these rocks. Three samples of quartzite from the Syringa metamorphic sequence northwest of the Idaho batholith contain zircon grains younger than the Belt Supergroup and support a Neoproterozoic age. A single Cambrian sample has abundant 1780 Ma grains and none younger than ~1750 Ma. These results indicate that the likely protoliths of many high-grade metamorphic rocks in northern Idaho were strata of the Belt-Purcell Supergroup or overlying rocks of the Neoproterozoic Windermere Supergroup and not basement rocks.

The behavior of iron and zinc stable isotopes accompanying the subduction of mafic oceanic crust: A case study from Western Alpine ophiolites

NASA Astrophysics Data System (ADS)

Inglis, Edward C.; Debret, Baptiste; Burton, Kevin W.; Millet, Marc-Alban; Pons, Marie-Laure; Dale, Christopher W.; Bouilhol, Pierre; Cooper, Matthew; Nowell, Geoff M.; McCoy-West, Alex J.; Williams, Helen M.

2017-07-01

Arc lavas display elevated Fe3+/ΣFe ratios relative to MORB. One mechanism to explain this is the mobilization and transfer of oxidized or oxidizing components from the subducting slab to the mantle wedge. Here we use iron and zinc isotopes, which are fractionated upon complexation by sulfide, chloride, and carbonate ligands, to remark on the chemistry and oxidation state of fluids released during prograde metamorphism of subducted oceanic crust. We present data for metagabbros and metabasalts from the Chenaillet massif, Queyras complex, and the Zermatt-Saas ophiolite (Western European Alps), which have been metamorphosed at typical subduction zone P-T conditions and preserve their prograde metamorphic history. There is no systematic, detectable fractionation of either Fe or Zn isotopes across metamorphic facies, rather the isotope composition of the eclogites overlaps with published data for MORB. The lack of resolvable Fe isotope fractionation with increasing prograde metamorphism likely reflects the mass balance of the system, and in this scenario Fe mobility is not traceable with Fe isotopes. Given that Zn isotopes are fractionated by S-bearing and C-bearing fluids, this suggests that relatively small amounts of Zn are mobilized from the mafic lithologies in within these types of dehydration fluids. Conversely, metagabbros from the Queyras that are in proximity to metasediments display a significant Fe isotope fractionation. The covariation of δ56Fe of these samples with selected fluid mobile elements suggests the infiltration of sediment derived fluids with an isotopically light signature during subduction.

Cenozoic geodynamic evolution of the Aegean

NASA Astrophysics Data System (ADS)

Jolivet, Laurent; Brun, Jean-Pierre

2010-01-01

The Aegean region is a concentrate of the main geodynamic processes that shaped the Mediterranean region: oceanic and continental subduction, mountain building, high-pressure and low-temperature metamorphism, backarc extension, post-orogenic collapse, metamorphic core complexes, gneiss domes are the ingredients of a complex evolution that started at the end of the Cretaceous with the closure of the Tethyan ocean along the Vardar suture zone. Using available plate kinematic, geophysical, petrological and structural data, we present a synthetic tectonic map of the whole region encompassing the Balkans, Western Turkey, the Aegean Sea, the Hellenic Arc, the Mediterranean Ridge and continental Greece and we build a lithospheric-scale N-S cross-section from Crete to the Rhodope massif. We then describe the tectonic evolution of this cross-section with a series of reconstructions from ~70 Ma to the Present. We follow on the hypothesis that a single subduction has been active throughout most of the Mesozoic and the entire Cenozoic, and we show that the geological record is compatible with this hypothesis. The reconstructions show that continental subduction (Apulian and Pelagonian continental blocks) did not induce slab break-off in this case. Using this evolution, we discuss the mechanisms leading to the exhumation of metamorphic rocks and the subsequent formation of extensional metamorphic domes in the backarc region during slab retreat. The tectonic histories of the two regions showing large-scale extension, the Rhodope and the Cyclades are then compared. The respective contributions to slab retreat, post-orogenic extension and lower crust partial melting of changes in kinematic boundary conditions and in nature of subducting material, from continental to oceanic, are discussed.

Photoreduction of Hg(II) and photodemethylation of methylmercury: the key role of thiol sites on dissolved organic matter

USGS Publications Warehouse

Jeremiason, Jeffrey D.; Portner, Joshua C.; Aiken, George R.; Hiranaka, Amber J.; Dvorak, Michelle T.; Tran, Khuyen T.; Latch, Douglas E.

2015-01-01

This study examined the kinetics of photoreduction of Hg(II) and photodemethylation of methylmercury (MeHg+) attached to, or in the presence of, dissolved organic matter (DOM). Both Hg(II) and MeHg+ are principally bound to reduced sulfur groups associated with DOM in many freshwater systems. We propose that a direct photolysis mechanism is plausible for reduction of Hg(II) bound to reduced sulfur groups on DOM while an indirect mechanism is supported for photodemethylation of MeHg+ bound to DOM. UV spectra of Hg(II) and MeHg+ bound to thiol containing molecules demonstrate that the Hg(II)–S bond is capable of absorbing UV-light in the solar spectrum to a much greater extent than MeHg+–S bonds. Experiments with chemically distinct DOM isolates suggest that concentration of DOM matters little in the photochemistry if there are enough reduced S sites present to strongly bind MeHg+ and Hg(II); DOM concentration does not play a prominent role in photodemethylation other than to screen light, which was demonstrated in a field experiment in the highly colored St. Louis River where photodemethylation was not observed at depths ≥10 cm. Experiments with thiol ligands yielded slower photodegradation rates for MeHg+ than in experiments with DOM and thiols; rates in the presence of DOM alone were the fastest supporting an intra-DOM mechanism. Hg(II) photoreduction rates, however, were similar in experiments with only DOM, thiols plus DOM, or only thiols suggesting a direct photolysis mechanism. Quenching experiments also support the existence of an intra-DOM photodemethylation mechanism for MeHg+. Utilizing the difference in photodemethylation rates measured for MeHg+ attached to DOM or thiol ligands, the binding constant for MeHg+ attached to thiol groups on DOM was estimated to be 1016.7.

Characterization and origin of polar dissolved organic matter from the Great Salt Lake

USGS Publications Warehouse

Leenheer, J.A.; Noyes, T.I.; Rostad, C.E.; Davisson, M.L.

2004-01-01

Polar dissolved organic matter (DOM) was isolated from a surface-water sample from the Great Salt Lake by separating it from colloidal organic matter by membrane dialysis, from less-polar DOM fractions by resin sorbents, and from inorganic salts by a combination of sodium cation exchange followed by precipitation of sodium salts by acetic acid during evaporative concentration. Polar DOM was the most abundant DOM fraction, accounting for 56% of the isolated DOM. Colloidal organic matter was 14C-age dated to be about 100% modern carbon and all of the DOM fractions were 14C-age dated to be between 94 and 95% modern carbon. Average structural models of each DOM fraction were derived that incorporated quantitative elemental and infrared, 13C-NMR, and electrospray/mass spectrometric data. The polar DOM model consisted of open-chain N-acetyl hydroxy carboxylic acids likely derived from N-acetyl heteropolysaccharides that constituted the colloidal organic matter. The less polar DOM fraction models consisted of aliphatic alicyclic ring structures substituted with carboxyl, hydroxyl, ether, ester, and methyl groups. These ring structures had characteristics similar to terpenoid precursors. All DOM fractions in the Great Salt Lake are derived from algae and bacteria that dominate DOM inputs in this lake.

Complete and Partial Photo-oxidation of Dissolved Organic Matter Draining Permafrost Soils.

PubMed

Ward, Collin P; Cory, Rose M

2016-04-05

Photochemical degradation of dissolved organic matter (DOM) to carbon dioxide (CO2) and partially oxidized compounds is an important component of the carbon cycle in the Arctic. Thawing permafrost soils will change the chemical composition of DOM exported to arctic surface waters, but the molecular controls on DOM photodegradation remain poorly understood, making it difficult to predict how inputs of thawing permafrost DOM may alter its photodegradation. To address this knowledge gap, we quantified the susceptibility of DOM draining the shallow organic mat and the deeper permafrost layer of arctic soils to complete and partial photo-oxidation and investigated changes in the chemical composition of each DOM source following sunlight exposure. Permafrost and organic mat DOM had similar lability to photomineralization despite substantial differences in initial chemical composition. Concurrent losses of carboxyl moieties and shifts in chemical composition during photodegradation indicated that photodecarboxylation could account for 40-90% of DOM photomineralized to CO2. Permafrost DOM had a higher susceptibility to partial photo-oxidation compared to organic mat DOM, potentially due to a lower abundance of phenolic moieties with antioxidant properties. These results suggest that photodegradation will likely continue to be an important control on DOM fate in arctic freshwaters as the climate warms and permafrost soils thaw.

SPRUCE Advanced Molecular Techniques Provide a Rigorous Method for Characterizing Organic Matter Quality in Complex Systems: Supporting Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilson, Rachel M; Tfaily, Malak M

These data are provided in support of the Commentary, Advanced molecular techniques provide a rigorous method for characterizing organic matter quality in complex systems, Wilson and Tfaily (2018). Measurement results demonstrate that optical characterization of peatland dissolved organic matter (DOM) may not fully capture classically identified chemical characteristics and may, therefore, not be the best measure of organic matter quality.

The Mt. Ochi melange (South Evvia Island, Greece): a case study for HP metamorphism and syn-convergent exhumation.

NASA Astrophysics Data System (ADS)

Moustaka, Eleni; Soukis, Konstantinos; Huet, Benjamin; Lozios, Stylianos; Magganas, Andreas

2014-05-01

The Attic-Cycladic complex (central Aegean Sea, Greece) experienced profound extension since at least the Oligo-Miocene boundary during which the previously thickened crust was reworked by a series of detachments forming the NE directed North Cycladic Detachment System (NCDS) and the SSW directed West Cycladic Detachment System (WCDS). South Evvia Island is located at the northwestern part of the Attic Cycladic complex linking the highly thinned and polymetamorphosed central part of the complex with mainland Greece. Furthermore, greenschists-facies retrograde metamorphism has only partially overprinted the HP mineral assemblages. Consequently, it is an ideal area to study tectonic processes associated with subduction, HP metamorphism and subsequent exhumation from eclogitic depths to the surface. Geological mapping in 1:2:000 scale revealed that the tectonostratigraphy of Mt. Ochi includes three distinct units all metamorphosed in HP conditions followed by greenschist facies overprint. These units are from top to bottom a) the Ochi Unit, a thick metavolcanosedimentary sequence with some intensely folded cipoline marble intercalations and isolated occurrences of metabasic rocks b) the ophiolitic mélange (metagabbros, metawherlites, peridotites, metabasites within a metasedimentary+serpentinite matrix) and c) the lowermost Styra Unit, a cipoline marble-dominated unit with thin mica schists and rare quartzitic layers often boudinaged. The thrust fault that was responsible for the juxtaposition of these three units acted in an early stage during HP metamorphism and it was isoclinally folded and sheared by the following syn-metamorphic deformation events. Detailed structural study in meso- and microscopic scale combined with petrological and geochemical analyses of the Mt Ochi rocks led to the distinction of at least three syn-metamorphic and two post-metamorphic deformation episodes that affected all units. The oldest structure identified is a relic foliation formed by the mineral assemblage Na-amphibole + lawsonite seen as inclusion in epidote porphyroblasts within the melange. It could represent a structure of the prograde path but it could also have formed during the peak HP event. This is followed by successive folding episodes that are related to axial plane foliations and a ~E-W intersection/stretching lineation formed by typical blueschist- to epidote-blueschist facies mineral assemblages. The main foliation that can be observed in all three units is a greenschist-facies axial plane foliation accompanied by a ~ENE-WSW stretching lineation. The shear sense during the prograde path is constantly towards the WSW. In the greenschists-facies an unambiguous top-to ENE can be observed mostly in mylonitic rocks. The following deformation episodes include semi-brittle to brittle structures (shear bands brittle open folds, crenulation cleavage, and faults with increasingly higher-angle) that are not as penetrative and record the passage of the units through the brittle-ductile transitions and to higher structural levels. The kinematics of these late episodes is also towards the NE. Based on the above, the Mt Ochi HP units exhibit a common tectonometamorphic evolution since at least the early stages of the prograde path. The Ochi Unit/Styra Unit contact is a structure that formed prior to or during peak HP metamorphism and therefore it couldn't have served as the normal fault to an extrusion wedge.

The systematic change of metamorphism along the Dabie-Sulu-Hongseong-Odesan collision belt between the North and South China blocks

NASA Astrophysics Data System (ADS)

Oh, C. W.

2013-12-01

As a last step of formation of the Pangea supercontinent, the North China block collided with the South China block during Permo-Triassic time forming the Oinling-Dabie-Sulu collision belt which was identified by the finding of ultrahigh- and high-P/T eclogites along the belt. After the Qiling-Dabie-Sulu collision belt was found, the continuation of the collision belt into Korean Peninsula became a hot issue. Although the Imjingang belt in Korean Peninsula was suggested as an extension of the belt, no evidence of collision belt such as eclogite and ophiolite, was found. Whereas recent studies on Korean Peninsula reveal that Triassic eclogite (ca. > 230 Ma) formed in the Hongseong area and Triassic post collision igneous rocks (with ca. 230 Ma intrusion ages) occurred throughout the Gyeonggi Massif locating to the north of the line connecting the Hongseong, Yangpyeong and Odesan areas. These new findings derive the tectonic model in which the Permo-Triassic Qinling-Dabie-Sulu collision belt between the North and South China blocks extends into the Hongseong-Yangpyeong-Odesan collision belt in Korean Peninsula. The belt may be further extended into the late Paleozoic subduction complex in the Yanji belt in North Korea through the Paleozoic subduction complex in the inner part of SW Japan. The collision had started from Korea at ca. 250 Ma and propagated towards China. The collision completed during late Triassic. The metamorphic conditions systematically change along the collision belt; ultrahigh-temperature metamorphism occurred in the Odesan area (at 245-230Ma; 9.0-10.6 kbar, 915-1160°C), high-P/T metamorphism in the Hongseong area (17.0-21.9 kbar, 835-860°C) and ultrahigh-pressure metamorphism in the Dabie and Sulu belts (30-40 kbar, 680-880°C). This systematic increasing peak pressure condition and decreasing peak temperature condition towards west, may be due to the increase in the depth of slab break-off towards west, which might be related to the increase of the amounts of subducted ocecnic slab towards west. The wide distribution of Permo-Triassic arc-related granitoids in the Yeongnam Massif, southern part of Korean Peninsula and in the southern part of the South China block, indicate the Permo-Triassic subduction along the southern boundary of the South China block which may be due to compression caused by the Permo-Triassic collision between the North and South China blocks. The collision belt divides the Gyeonggi Massif into two parts; the northern and southern parts can be correlated to the North and South China blocks, respectively. The Ogcheon metamorphic belt which locates between the Gyeonggi and Youngnam Massifs in Korean Peninsula, can be correlated to the Nanhua rift which formed at 760 Ma and separated the South China blocks into the Yantze and Cathaysia cratons. In that case, the southern Gyeonggi Massif and Yeongnam Massif can be correlated to the Yangtze and Cathaysia cratons in the South China block, respectively. Recently Neoproterozoic igneous complex which was metamorphosed by the late Silurian intermediate-P/T and early Devonian ultrahigh temperature metamorphism, are recognized in the Hongseong area. These metamorphisms indicate the possibility of Middle Paleozoic collision of Neoproterozoic microcontinent with the northern margin of the South China block.

Partitioning of the pesticide trifluralin between dissolved organic matter and water using automated SPME-GC/MS.

PubMed

Caupos, Emilie; Touffet, Arnaud; Mazellier, Patrick; Croue, Jean-Philippe

2015-03-01

Solid-phase microextraction (SPME) was used to determine the equilibrium association constant for a pesticide, trifluralin (TFR), with dissolved organic matter (DOM). After optimization of the SPME method for the analysis of TFR, partition coefficients (K DOM) with three different sources of DOM were determined in buffered solutions at pH 7. Commercial humic acids and DOM fractions isolated from two surface waters were used. The values of log K DOM varied from 4.3 to 5.8, depending on the nature of the organic material. A good correlation was established between log K DOM and DOM properties (as measured with the H/O atomic ratio and UV absorbance), in agreement with literature data. This is consistent with the effect of polarity and aromaticity for governing DOM-pollutant associations, regardless of the origin of DOM. This association phenomenon is relevant to better understand the behavior of pesticides in the environment since it controls part of pesticide leaching and fate in aquatic systems.

Protracted or multiple subduction of metapelites (Rhodope UHP domain, Greece)?

NASA Astrophysics Data System (ADS)

Krohe, A.; Wawrzenitz, N. H.; Mposkos, E.; Romer, R. L.

2012-12-01

The Rhodope domain formed along the suture between the European and the Apulian/Adriatic plate, which collided in the early Tertiary (closure of the Vardar/Axios ocean). Its metamorphic history includes UHP metamorphism documented by diamond inclusions in garnet (Mposkos & Kostopoulos 2001, Perraki et al. 2006, Schmidt et al. 2010), presumably of Jurassic age, and Eocene stages of MP and HP metamorphism. The age of UHPM is still a matter of debate: U-Pb SHRIMP ages extend from 184-172 Ma (monazite in metapelites) to ca. 42 Ma with clusters at 170-160, 150-140, 80-60, 50, 42 Ma, (U-Pb SHRIMP dating of zircon from amphibolitized eclogites and metapelites). These ages are interpreted to date subsequent stages of (U)HP metamorphism and decompression (Liati et al., 2005, Hoinkes et al. 2008, Bauer et al. 2006, Krenn et al 2010). However, these ages are obviously difficult to link with the metamorphic reactions. The metamorphic history has been interpreted in different ways, reflecting: (i) successive accretion of small terranes with rapid subduction and uplift histories (e.g. Liati et al. 2005); (ii) a composite of different tectonic units varying in earlier P-T histories, assembled by shear zones that reflect tectonic erosion and differential exhumation along the plate interface and that are now erased and overprinted (Krohe and Mposkos, 2002, Mposkos et al., 2010). These interpretations imply a different kinematics of the tectonic movements at depths, mechanical processes and process rates. Additionally, a protracted polymetamorphic history of larger volumes of the Rhodope UHP domain may be considered; e.g. the Kimi complex stayed in the lower crust for ca. 50-60 Ma after exhumation of the UHP rocks to this lower crustal level (Mposkos and Krohe, 2006). To constrain a precise age of the HP granulite facies and a minimum age of UHP metamorphism, we conduct an integrated structural, petrologic and geochronological study in a metapelite from the Sidronero Complex. The mineral assemblages Grt-Ky-Bt-Pl-Kfs-Qtz-Rt and Grt-Ky-Bt-Ms-Pl-Qtz-Rt, record a HP granulite facies metamorphism followed by upper amphibolite facies. The rock is particularly well suited for studying the granulite facies metamorphism, as it contains domains that are only weakly overprinted by later metamorphic episodes. ID-TIMS U-Pb ages of single monazite grains and fractions of few grains, that are only locally patchy-zoned and associated with garnet and kyanite, plot along the concordia between 64 to 60 Ma. One date of 55 Ma might represent Pb-loss during later fluid-induced dissolution-reprecipitation, probably related to biotite growth during the amphibolite facies overprint. On the base of these data, a model is discussed, in which rocks from the upper plate and HP-rocks that have been already exhumed, were dragged again into the subduction channel by subduction erosion Bauer et al. 2006, Lithos, 29, 207-228; Hoinkes et al. 2008, 3rd IGC Oslo, UHP-4; Krenn et al 2010, Tectonics, 29, TC4001; Krohe & Mposkos, 2002, Geol. Soc. Sp. Pub. 204, 151-178; Liati, A., 2005, Contrib. Mineral. Petrol., 150, 608-630; Mposkos, & Kostopoulos, 2001, EPSL, 192, 497-506; Mposkos & Krohe, 2006. Can. J. Earth Sci., 43, 1755-1776; Mposkos et al., 2010 Proc. XIX CBGA Congress, 100, 173-178; Perraki et al., 2006, EPSL, 241, 672-685; Schmidt et al., 2010, EJM, 22, 189-198.

P-T-t paths from polyphased garnets of the Yenisey Ridge: evidence for three tectonothermal events along the western margin of Siberian craton

NASA Astrophysics Data System (ADS)

Likhanov, Igor

2015-04-01

Studies of pelitic gneisses and schists within the Yenisey regional shear zone (Garevka complex) at the western margin of the Siberian craton provide important constraints on the tectonothermal events and geodynamic processes in the Yenisey Ridge. In situ U-Th-Pb geochronology of monazite and xenotime from different growth zones of the garnet porphyroblasts coupled with P-T path calculations derived from garnet zoning patterns records three superimposed metamorphic event [1]. The different field gradients reflect contrasting tectonic settings. The first stage occurred as a result of the Grenville-age orogeny during late Meso-early Neoproterozoic (1050-850 Ma) and was marked by low-pressure zoned metamorphism at c. 4.8-5.0 kbar and 565-580 °C with a metamorphic field gradient of dT/dZ = 20-30 °C/km. At the second stage, the rocks experienced middle Neoproterozoic (801-793 Ma) collision-related medium-pressure metamorphism at c. 7.7-7.9 kbar and 630 °C with dT/dZ < 10 °C/km. The final stage evolved as a synexhumation retrograde metamorphism (785-776 Ma) at c. 4.8-5.4 kbar and 500 °C with dT/dZ < 14 °C/km and recorded uplift of the rocks to upper crustal levels in shear zones. The duration of post-collisional thrust exhumation does not exceed 16 Myr, which gives an exhumation rate of the metamorphic rocks of about 500-700 m/Myr [2]. This is in good agreement with the rate of exhumation (400 m/Myr) calculated for coeval collision-related metamorphic events in the Teya complex of the Yenisey Ridge [3] resulted from crustal thickening due to overthrusting [4] and also agrees with the results of thermomechanical numerical modeling (350 m/Myr) [5]. The final stages of collisional orogeny were followed by the development of rift-related bimodal dyke swarms of the Baikal-Yenisey belt, resulting from Neoproterozoic (790-780 Ma) extensional processes along the western margin of the Siberian craton and the onset of Rodinia's breakup [6]. Post-Grenville metamorphic episodes of regional crust evolution are correlated with the synchronous succession and similar style of the later tectonometamorphic events within the Valhalla orogen along the Arctic margin of Rodinia [7,8] and supports the spatial proximity of Siberia and North Atlantic cratons (Laurentia, Baltica, Svalbard) at c. 800 Ma, as indicated by the Neoproterozoic paleocontinental reconstructions of the classic Rodinia configuration [9,10]. [1] Likhanov et al. (2013) Petrology 21, 561-578. [2] Likhanov et al. (2014) J. Asian Earth Sci., http://dx.doi.org/10.1016/j.jseaes.2014.10.026. [3] Likhanov et al. (2011) Russ. Geol. Geophys. 52, 1256-1269. [4] Likhanov & Reverdatto (2011) Int. Geol. Rev. 53, 802-845. [5] Likhanov et al. (2004) J. Metamorph. Geol. 22, 743-762. [6] Likhanov et al. (2013) Dokl. Earth Sci. 450, 613-617. [7] Cutts et al. (2010) J. Metamorph. Geol. 28, 249-267. [8] Cawood et al. (2010) Geology 38, 99-102. [9] Dalziel et al. (2000) J. Geol. 108, 499-513. [10] Torsvik (2003) Science 300, 1379-1381.

Ocean metabolism and dissolved organic matter: How do small dissolved molecules persist in the ocean?

NASA Astrophysics Data System (ADS)

Benner, Ronald

2010-05-01

The ocean reservoir of dissolved organic matter (DOM) is among the largest global reservoirs (~700 Pg C) of reactive organic carbon. Marine primary production (~50 Pg C/yr) by photosynthetic microalgae and cyanobacteria is the major source of organic matter to the ocean and the principal substrate supporting marine food webs. The direct release of DOM from phytoplankton and other organisms as well as a variety of other processes, such as predation and viral lysis, contribute to the ocean DOM reservoir. Continental runoff and atmospheric deposition are relatively minor sources of DOM to the ocean, but some components of this material appear to be resistant to decomposition and to have a long residence time in the ocean. Concentrations of DOM are highest in surface waters and decrease with depth, a pattern that reflects the sources and diagenesis of DOM in the upper ocean. Most (70-80%) marine DOM exists as small molecules of low molecular weight (<1 kDalton). Surprisingly, high-molecular-weight (>1 kDalton) DOM is relatively enriched in major biochemicals, such as combined neutral sugars and amino acids, and is more bioavailable than low-molecular-weight DOM. The observed relationships among the size, composition, and reactivity of DOM have led to the size-reactivity continuum model, which postulates that diagenetic processes lead to the production of smaller molecules that are structurally altered and resistant to microbial degradation. The radiocarbon content of these small dissolved molecules also indicates these are the most highly aged components of DOM. Chemical signatures of bacteria are abundant in DOM and increase during diagenesis, indicating bacteria are an important source of slowly cycling biochemicals. Recent analyses of DOM isolates by ultrahigh-resolution mass spectrometry have revealed an incredibly diverse mixture of molecules. Carboxyl-rich alicyclic molecules are abundant in DOM, and they appear to be derived from diagenetically-altered terpenoids, such as sterols and hopanoids. Thermally-altered molecules, including black carbon, also appear to be important components of DOM, but their origins are unclear. We are rapidly acquiring novel information about the composition and molecular identity of DOM, and novel insights about the origins, transformations and fates this vast reservoir of DOM are emerging. This presentation will review and synthesize this information for comparison with non-living organic matter in other systems.

Copper(II) binding by dissolved organic matter: Importance of the copper-to-dissolved organic matter ratio and implications for the Biotic Ligand Model

USGS Publications Warehouse

Craven, Alison M.; Aiken, George R.; Ryan, Joseph N.

2012-01-01

The ratio of copper to dissolved organic matter (DOM) is known to affect the strength of copper binding by DOM, but previous methods to determine the Cu2+–DOM binding strength have generally not measured binding constants over the same Cu:DOM ratios. In this study, we used a competitive ligand exchange–solid-phase extraction (CLE-SPE) method to determine conditional stability constants for Cu2+–DOM binding at pH 6.6 and 0.01 M ionic strength over a range of Cu:DOM ratios that bridge the detection windows of copper-ion-selective electrode and voltammetry measurements. As the Cu:DOM ratio increased from 0.0005 to 0.1 mg of Cu/mg of DOM, the measured conditional binding constant (cKCuDOM) decreased from 1011.5 to 105.6 M–1. A comparison of the binding constants measured by CLE-SPE with those measured by copper-ion-selective electrode and voltammetry demonstrates that the Cu:DOM ratio is an important factor controlling Cu2+–DOM binding strength even for DOM isolates of different types and different sources and for whole water samples. The results were modeled with Visual MINTEQ and compared to results from the biotic ligand model (BLM). The BLM was found to over-estimate Cu2+ at low total copper concentrations and under-estimate Cu2+ at high total copper concentrations.

Carotenoids are the likely precursor of a significant fraction of marine dissolved organic matter

PubMed Central

Arakawa, Neal; Aluwihare, Lihini I.; Simpson, Andre J.; Soong, Ronald; Stephens, Brandon M.; Lane-Coplen, Daniel

2017-01-01

The ocean’s biota sequester atmospheric carbon dioxide (CO2) in part by producing dissolved organic matter (DOM) that persists in the ocean for millennia. This long-term accumulation of carbon may be facilitated by abiotic and biotic production of chemical structures that resist degradation, consequently contributing disproportionately to refractory DOM. Compounds that are selectively preserved in seawater were identified in solid-phase extracted DOM (PPL-DOM) using comprehensive gas chromatography (GC) coupled to mass spectrometry (MS). These molecules contained cyclic head groups that were linked to isoprenoid tails, and their overall structures closely resembled carotenoid degradation products (CDP). The origin of these compounds in PPL-DOM was further confirmed with an in vitro β-carotene photooxidation experiment that generated water-soluble CDP with similar structural characteristics. The molecular-level identification linked at least 10% of PPL-DOM carbon, and thus 4% of total DOM carbon, to CDP. Nuclear magnetic resonance spectra of experimental CDP and environmental PPL-DOM overlapped considerably, which indicated that even a greater proportion of PPL-DOM was likely composed of CDP. The CDP-rich DOM fraction was depleted in radiocarbon (14C age > 1500 years), a finding that supports the possible long-term accumulation of CDP in seawater. By linking a specific class of widespread biochemicals to refractory DOM, this work provides a foundation for future studies that aim to examine how persistent DOM forms in the ocean. PMID:28959723

Late Vendian Complexes in the Structure of Metamorphic Basement of the Fore Range Zone, Greater Caucasus

NASA Astrophysics Data System (ADS)

Kamzolkin, V. A.; Latyshev, A. V.; Vidyapin, Yu. P.; Somin, M. L.; Smul'skaya, A. I.; Ivanov, S. D.

2018-05-01

The paper presents new data on the composition, age, and relationships (with host and overlying deposits) of intrusive rocks in the basement of the Fore Range zone (Greater Caucasus), in the Malaya Laba River Basin. The evolutionary features of intrusive units located within the Blyb metamorphic complex are described. It is shown for the first time that the lower levels of this complex are, in a structural sense, outcrops of the Late Vendian basement. The basement is composed of the Balkan Formation and a massif of quartz metadiorites that intrudes it; for the rocks of this massif, ages ranging from 549 ± 7.4 to 574.1 ± 6.7 Ma are obtained for three U-Pb datings by the SHRIMP-II method. The Herzyinan magmatic event is represented by a group of granodiorite intrusions penetrating the Blyb complex on a series of faults extending along its boundary with the Main Range zone. The obtained estimate for the U-Pb age of one of the intrusions (319 ± 3.8 Ma) corresponds to the end of the Serpukhovian stage of the Early Carboniferous.

Cadomian magmatism and metamorphism at the Ossa Morena/Central Iberian zone boundary, Iberian Massif, Central Portugal: Geochemistry and P-T constraints of the Sardoal Complex

NASA Astrophysics Data System (ADS)

Henriques, S. B. A.; Neiva, A. M. R.; Tajčmanová, L.; Dunning, G. R.

2017-01-01

A well preserved Cadomian basement is exposed in the Iberian Massif, Central Portugal, at the Ossa Morena/Central Iberian zone boundary, which allows the determination of reliable geochemical data. A sequence of Cadomian and Variscan magmatic and tectonometamorphic events has been already described for this area and are documented in other areas of the Avalonian-Cadomian orogen. However, the geochemical information concerning the Cadomian basement for this area is still limited. We present whole rock geochemical and oxygen isotopic information to characterize the igneous protoliths of the Sardoal Complex, located within the Tomar-Badajoz-Córdoba Shear Zone, and identify their tectonic setting. We use detailed petrography, mineral chemistry and P-T data to characterize the final Cadomian tectonometamorphic event. The Sardoal Complex contains orthogneiss and amphibolite units. The protoliths of the orthogneiss are calc-alkaline magmas of acid composition and peraluminous character that were generated in an active continental margin in three different stages (ca. 692 Ma, ca. 569 Ma and ca. 548 Ma). The most significant processes in their petrogenesis are the partial melting of old metasedimentary and meta-igneous crust at different crustal levels and the crystal fractionation of plagioclase, alkali feldspars, apatite, zircon and Fe-Ti oxides. The protoliths of the amphibolite, older than ca. 540 Ma, are tholeiitic and calc-alkaline magmas of basic composition that display N-, T- and E-MORB affinities. They were generated in an active continental margin. Crustal contamination and fractional crystallization of hornblende and diopside were involved in their petrogenesis. However, the fractional crystallization was not significant. The magmatic activity recorded in the Sardoal Complex indicates the existence of a long-lived continental arc (ca. 692-540 Ma) with coeval felsic and mafic magmatism. The final stage of the Cadomian metamorphism is usually represented in other areas of the Cadomian basement as a LP-HT metamorphic event. However, the P-T data obtained by thermodynamic modelling indicates medium pressure/high temperature conditions at ca. 540 Ma. These data suggest that the Sardoal Complex represents a deeper level of the exhumed Cadomian basement where the final stage of the Cadomian metamorphism was recorded.

Influence of land use and land cover on the spatial variability of dissolved organic matter in multiple aquatic environments.

PubMed

Singh, Shatrughan; Dash, Padmanava; Silwal, Saurav; Feng, Gary; Adeli, Ardeshir; Moorhead, Robert J

2017-06-01

Water quality of lakes, estuaries, and coastal areas serves as an indicator of the overall health of aquatic ecosystems as well as the health of the terrestrial ecosystem that drains to the water body. Land use and land cover plays not only a significant role in controlling the quantity of the exported dissolved organic matter (DOM) but also influences the quality of DOM via various biogeochemical and biodegradation processes. We examined the characteristics and spatial distribution of DOM in five major lakes, in an estuary, and in the coastal waters of the Mississippi, USA, and investigated the influence of the land use and land cover of their watersheds on the DOM composition. We employed absorption and fluorescence spectroscopy including excitation-emission matrix (EEM) combined with parallel factor (PARAFAC) analysis modeling techniques to determine optical properties of DOM and its characteristics in this study. We developed a site-specific PARAFAC model to evaluate DOM characteristics resulting in five diverse DOM compositions that included two terrestrial humic-like (C1 and C3), two microbial humic-like (C2 and C5), and one protein-like (C4) DOM. Our results showed elevated fluorescence levels of microbial humic-like or protein-like DOM in the lakes and coastal waters, while the estuarine waters showed relatively high fluorescence levels of terrestrial humic-like DOM. The results also showed that percent forest and wetland coverage explained 68 and 82% variability, respectively, in terrestrial humic-like DOM exports, while 87% variability in microbially derived humiclike DOM was explained by percent agricultural lands. Strong correlations between microbial humic-like DOM and fluorescence-derived DOM indices such as biological index (BIX) and fluorescence index (FI) indicated autochthonous characteristics in the lakes, while the estuary showed largely allochthonous DOM of terrestrial origin. We also observed higher concentrations of total dissolved phosphorous (TDP) and ammonium nitrogen (NH 4 -N) in coastal waters potentially due to photodegradation of refractory DOM derived from the sediment-bound organic matter in the coastal wetlands. This study highlights the relationships between the DOM compositions in the water and the land use and land cover in the watershed. The spatial variability of DOM in three different types of aquatic environments enhances the understanding of the role of land use and land cover in carbon cycling through export of organic matter to the aquatic ecosystems..

Dom34 Links Translation to Protein O-mannosylation

PubMed Central

van Wijlick, Lasse; Geissen, René; Hilbig, Jessica S.; Lagadec, Quentin; Cantero, Pilar D.; Juchimiuk, Mateusz; Kluge, Sven; Wickert, Stephan; Alepuz, Paula; Ernst, Joachim F.

2016-01-01

In eukaryotes, Dom34 upregulates translation by securing levels of activatable ribosomal subunits. We found that in the yeast Saccharomyces cerevisiae and the human fungal pathogen Candida albicans, Dom34 interacts genetically with Pmt1, a major isoform of protein O-mannosyltransferase. In C. albicans, lack of Dom34 exacerbated defective phenotypes of pmt1 mutants, while they were ameliorated by Dom34 overproduction that enhanced Pmt1 protein but not PMT1 transcript levels. Translational effects of Dom34 required the 5′-UTR of the PMT1 transcript, which bound recombinant Dom34 directly at a CA/AC-rich sequence and regulated in vitro translation. Polysomal profiling revealed that Dom34 stimulates general translation moderately, but that it is especially required for translation of transcripts encoding Pmt isoforms 1, 4 and 6. Because defective protein N- or O-glycosylation upregulates transcription of PMT genes, it appears that Dom34-mediated specific translational upregulation of the PMT transcripts optimizes cellular responses to glycostress. Its translational function as an RNA binding protein acting at the 5′-UTR of specific transcripts adds another facet to the known ribosome-releasing functions of Dom34 at the 3′-UTR of transcripts. PMID:27768707

Dom34 Links Translation to Protein O-mannosylation.

PubMed

van Wijlick, Lasse; Geissen, René; Hilbig, Jessica S; Lagadec, Quentin; Cantero, Pilar D; Pfeifer, Eugen; Juchimiuk, Mateusz; Kluge, Sven; Wickert, Stephan; Alepuz, Paula; Ernst, Joachim F

2016-10-01

In eukaryotes, Dom34 upregulates translation by securing levels of activatable ribosomal subunits. We found that in the yeast Saccharomyces cerevisiae and the human fungal pathogen Candida albicans, Dom34 interacts genetically with Pmt1, a major isoform of protein O-mannosyltransferase. In C. albicans, lack of Dom34 exacerbated defective phenotypes of pmt1 mutants, while they were ameliorated by Dom34 overproduction that enhanced Pmt1 protein but not PMT1 transcript levels. Translational effects of Dom34 required the 5'-UTR of the PMT1 transcript, which bound recombinant Dom34 directly at a CA/AC-rich sequence and regulated in vitro translation. Polysomal profiling revealed that Dom34 stimulates general translation moderately, but that it is especially required for translation of transcripts encoding Pmt isoforms 1, 4 and 6. Because defective protein N- or O-glycosylation upregulates transcription of PMT genes, it appears that Dom34-mediated specific translational upregulation of the PMT transcripts optimizes cellular responses to glycostress. Its translational function as an RNA binding protein acting at the 5'-UTR of specific transcripts adds another facet to the known ribosome-releasing functions of Dom34 at the 3'-UTR of transcripts.

Stormwater dissolved organic matter: influence of land cover and environmental factors.

PubMed

McElmurry, Shawn P; Long, David T; Voice, Thomas C

2014-01-01

Dissolved organic matter (DOM) plays a major role in defining biological systems and it influences the fate and transport of many pollutants. Despite the importance of DOM, understanding of how environmental and anthropogenic factors influence its composition and characteristics is limited. This study focuses on DOM exported as stormwater from suburban and urban sources. Runoff was collected before entering surface waters and DOM was characterized using specific ultraviolet absorbance at 280 nm (a proxy for aromaticity), molecular weight, polydispersity and the fraction of DOM removed from solution via hydrophobic and H-bonding mechanisms. General linear models (GLMs) incorporating land cover, precipitation, solar radiation and selected aqueous chemical measurements explained variations in DOM properties. Results show (1) molecular characteristics of DOM differ as a function of land cover, (2) DOM produced by forested land is significantly different from other landscapes, particularly urban and suburban areas, and (3) DOM from land cover that contains paved surfaces and sewers is more hydrophobic than from other types of land cover. GLMs incorporating environmental factors and land cover accounted for up to 86% of the variability observed in DOM characteristics. Significant variables (p < 0.05) included solar radiation, water temperature and water conductivity.

The genesis and exodus of vascular plant DOM from an oak woodland landscape

NASA Astrophysics Data System (ADS)

Hernes, Peter J.; Spencer, Robert G. M.; Dyda, Rachael Y.; O'Geen, Anthony T.; Dahlgren, Randy A.

2017-02-01

Evaluating the collective impact of small source inputs to larger rivers is a constant challenge in riverine biogeochemistry. In this study, we investigated the generation of dissolved organic matter (DOM) in a small oak woodland catchment in the foothills of northern California, the subsequent transformation in lignin biomarkers and chromophoric DOM (CDOM) parameters during transport through the landscape to an exporting stream, and finally the overall compositional impact on the larger receiving stream and river. Our study included a natural leaching experiment in which precipitation passing through oak, pine, and grass litter and duff samples was collected after each of a series of storms. Also included were soil trench samples to capture subsurface flow, stream samples along with point-source reservoir inputs, and samples of canopy throughfall, stemflow, and gopher hole (bypass) flow. The litter/duff leaching study demonstrated changing DOM fractionation patterns throughout the season, as evidenced by changing lignin compositions in the leachates with each successive storm. This adds a necessary seasonal component to interpreting lignin compositions in streams, as the source signatures are constantly changing. Released DOM from leaching was modified extensively during transit through the subsurface to the stream, with preferential increases in aromaticity as evidenced by increases in carbon-normalized absorbance at 254 nm, yet preferential decreases in lignin phenols, as evidence by carbon-normalized lignin yields in the headwater stream that was less than half that of the litter/duff leachates. Our extensive number of lignin measurements for source materials reveals a much more complex perspective on using lignin as a source indicator, as many riverine values for syringyl:vanillyl and cinnamyl:vanillyl ratios that have previously been interpreted as degraded lignin signatures are also possible as unmodified source signatures. Finally, this study demonstrated that the impact of numerous small headwater streams can significantly overprint the DOM signatures of much larger rivers over relatively short distances spanning several to tens of kilometers. This finding in particular challenges the assumption that river studies can be adequately conducted by focusing only on the main tributaries.

P- T- t constraints on the development of the Doi Inthanon metamorphic core complex domain and implications for the evolution of the western gneiss belt, northern Thailand

NASA Astrophysics Data System (ADS)

Macdonald, A. S.; Barr, S. M.; Miller, B. V.; Reynolds, P. H.; Rhodes, B. P.; Yokart, B.

2010-01-01

The western gneiss belt in northern Thailand is exposed within two overlapping Cenozoic structural domains: the extensional Doi Inthanon metamorphic core complex domain located west of the Chiang Mai basin, and the Mae Ping strike-slip fault domain located west of the Tak batholith. New P- T estimates and U-Pb and 40Ar/ 39Ar age determinations from the Doi Inthanon domain show that the gneiss there records a complex multi-stage history that can be represented by a clockwise P- T- t path. U-Pb zircon and titanite dating of mylonitic calc-silicate gneiss from the Mae Wang area of the complex indicates that the paragneissic sequence experienced high-grade, medium-pressure metamorphism (M1) in the Late Triassic - Early Jurassic (ca. 210 Ma), in good agreement with previously determined zircon ages from the underlying core orthogneiss exposed on Doi Inthanon. Late Cretaceous monazite ages of 84 and 72 Ma reported previously from the core orthogneiss are attributed to a thermal overprint (M2) to upper-amphibolite facies in the sillimanite field. U-Pb zircon and monazite dating of granitic mylonite from the Doi Suthep area of the complex provides an upper age limit of 40 Ma (Late Eocene) for the early stage(s) of development of the actual core complex, by initially ductile, low-angle extensional shearing under lower amphibolite-facies conditions (M3), accompanied by near-isothermal diapiric rise and decompression melting. 40Ar/ 39Ar laserprobe dating of muscovite from both Doi Suthep and Doi Inthanon provided Miocene ages of ca. 26-15 Ma, representing cooling through the ca. 350 °C isotherm and marking late-stage development of the core complex by detachment faulting of the cover rocks and isostatic uplift of the sheared core zone and mantling gneisses in the footwall. Similarities in the thermochronology of high-grade gneisses exposed in the core complex and shear zone domains in the western gneiss belt of northern Thailand (and also in northern Vietnam, Laos, Yunnan, and central Myanmar) suggest a complex regional response to indentation of Southeast Asia by India.

How Reservoirs Alter DOM Amount and Composition: Sources, Sinks, and Transformations

NASA Astrophysics Data System (ADS)

Kraus, T. E.; Bergamaschi, B. A.; Hernes, P. J.; Doctor, D. H.; Kendall, C.; Losee, R. F.; Downing, B. D.

2011-12-01

Reservoirs are critical components of many water supply systems as they allow the storage of water when supply exceeds demand. However, during water storage biogeochemical processes can alter both the amount and composition of dissolved organic matter (DOM), which can in turn affect water quality. While the balance between production and loss determines whether a reservoir is a net sink or source of DOM, changes in chemical composition are also relevant as they affect DOM reactivity (e.g. persistence in the environment, removability during coagulation treatment, and potential to form toxic compounds during drinking water treatment). The composition of the DOM pool also provides information about the DOM sources and processing, which can inform reservoir management. We examined the concentration and composition of DOM in San Luis Reservoir (SLR), a large off-stream impoundment of the California State Water Project. We used an array of DOM chemical tracers including dissolved organic carbon (DOC) concentration, optical properties, isotopic composition, lignin phenol content, and structural groupings determined by 13C NMR. There were periods when the reservoir was i) a net source of DOM due to the predominance of algal production (summer), ii) a net sink due to the predominance of degradation (fall/winter), and iii) balanced between production and consumption (spring). Despite only moderate variation in bulk DOC concentration (3.0-3.6 mg C/L), substantial changes in DOM composition indicated that terrestrial-derived material entering the reservoir was being degraded and replaced by aquatic-derived DOM produced within the reservoir. Results suggest reservoirs have the potential to reduce DOM amount and reactivity via degradative processes, however, these benefits can be decreased or even negated by the production of algal-derived DOM.

Geology of the Lake Mary quadrangle, Iron County, Michigan

USGS Publications Warehouse

Bayley, Richard W.

1959-01-01

The Lake Mary quadrangle is in eastern Iron County, in the west part of the Upper Peninsula of Michigan. The quadrangle is underlain by Lower and Middle Precambrian rocks, formerly designated Archean and Algonkian rocks, and is extensively covered by Pleistocene glacial deposits. A few Upper Precambrian (Keweenawan) diabase dikes and two remnants of sandstone and dolomite of early Paleozoic age are also found in the area. The major structural feature is the Holmes Lake anticline, the axis of which strikes northwest through the northeast part of the quadrangle. Most of the quadrangle, therefore, is underlain by rock of the west limb of the anticline. To the northwest along the fold axis, the Holmes Lake anticline is separated from the Amasa oval by a saddle of transverse folds in the vicinity of Michigamme Mountain in the Kiernan quadrangle. The Lower Precambrian rocks are represented by the Dickinson group and by porphyritic red granite whose relation to the Dickinson group is uncertain, but which may be older. The rocks of the Dickinson group are chiefly green to black metavolcanic schist and red felsite, some of the latter metarhyolite. The dark schist is commonly magnetic. The Dickinson group underlies the core area of the Holmes Lake anticline, which is flanked by steeply dipping Middle Precambrian formations of the Animikie series. A major unconformity separates the Lower Precambrian rocks from the overlying Middle Precambrian rocks. In ascending order the formations of the Middle Precambrian are the Randville dolomite, the Hemlock formation, which includes the Mansfield iron-bearing slate member, and the Michigamme slate. An unconformity occurs between the Hemlock formation and Michigamme slate. The post-Hemlock unconformity is thought to be represented in the Lake Mary quadrangle by the absence of iron-formation of the Amasa formation, which is known to lie between the Hemlock and the Michigamme to the northwest of the Lake Mary quadrangle in the Crystal Falls quadrangle. Post-Hemlock erosion may account also for the absence of iron-formation of the Fence River formation on the east limb of the Holmes Lake anticline within the Lake Mary quadrangle. The Randville dolomite is not exposed and is known only from diamond drilling in the northeast part of the area where it occurs in the east and west limbs of the Holmes Lake anticline. The formation has a maximum thickness of about 2,100 feet; this includes a lower arkosic phase, some of which is quartz pebble conglomerate, a medial dolomitic phase, and an upper slate phase. The triad is gradational. Included within the formation are a few beds of chloritic schist thought to be of volcanic origin. An unconformity between the Randville and the succeeding Hemlock is not indicated in the quadrangle, but is probably present. The Hemlock formation is best exposed in the northwest and south-central parts of the area. The apparent thickness of the formation is 10,000- 17,000 feet. It is composed mainly of mafic metavolcanic rocks and intercalated slate and iron-formation. In the north part of the quadrangle the volcanic rocks are greenstone, which includes altered basaltic flow rocks, volcanic breccia, tuff, and slate. Pillow structures are common in the metabasalt. It is not certain if any Hemlock rocks are present in the east limb of the Holmes Lake anticline. In the south part of the quadrangle, the rocks of the Hemlock are chiefly chlorite and hornblende schist and hornfels. Pyroxene hornfels is sparingly present. At least two sedimentary slate belts are included in the Hemlock formation. One of these, the Mansfield iron-bearing slate member, includes in its upper part an altered chert-siderite iron-formation 30 to over 150 feet thick from which iron ore has been mined at the Mansfield location. The position of the iron-bearing rocks has been determined magnetically, and past explorations for iron ore are discussed. Though probably; unconformable, the contact between the Hemlock and the Michigamme formations appears conformable. The Michigamme slate consists of at least 4,000 feet of interbedded mica schist and granulite, the altered equivalents of the slate and graywacke characteristic of the Michigamme in adjacent areas. The Michigamme rocks are best exposed in the south part of the quadrangle in the vicinity of Peavy Pond. Two periods of regional metamorphism have resulted in the alteration of almost all of the rocks of the quadrangle. The Lower Precambrian rocks underwent at least one period of metamorphism, uplift, and erosion before the deposition of the Randville dolomite. After the deposition of the Michigamme slate, a post-Middle Precambrian period of regional metamorphism occurred with attending deformation and igneous intrusion. The grade of metamorphism rises toward the south in the area. The rocks in the northern two-thirds of the quadrangle are representative of greenschist facies of regional metamorphism, whereas the rocks in the southern onethird of the quadrangle are representative of the albite-epidote-amphibolite, the amphibolite, and the pyroxene hornfels facies, the metamorphic node centering about the intrusive Peavy Pond complex in the Peavy Pond area. The Precambrian sedimentary and volcanic rocks are cut by intrusive igneous rocks of different types and several different ages. Gabbroic sills and dikes invaded the Hemlock rocks at some time after the Hemlock was deposited and before the post-Middle Precambrian orogeny and metamorphism. Some contact metamorphism attended the intrusion of the major sills. One of the sills, the West Kiernan sill, is well differentiated. A syntectonic igneous body, composed of gabbro and minor ultramafic parts and fringed with intermediate and felsic differentiates and hybrids, the Peavy; Pond complex, was intruded into the Hemlock and Michigamme formations during the post-Middle Precambrian orogeny. The complex is situated in the Peavy Pond area at the crest of the regional metamorphic node. Contact-altered sedimentary and volcanic rocks margin the complex. The effects of regional metamorphism have been superposed on the contact metamorphic rocks peripheral to the complex and on the igneous rocks of the complex as well. The mafic augite-bearing rocks of the complex emplaced early in the orogeny were deformed by granulation at the peak of the deformation and subsequently metamorphosed to hornblende rocks. Some of the intermediate and felsic rocks of the complex were foliated by the deformation, while the more fluid, felsic parts of the complex were intruded under orogenic stress and crystallized after the peak of deformation. The deformation culminated in major faulting during which the formations were dislocated, and some of the granite of the complex was extremely brecciated. A few diabase dikes, probably of Keweenawan age, have intruded the deformed and altered Animikie rocks. The only known metallic resource is iron ore. The Mansfield mine produced 1¥2 million tons of high-grade iron ore between the years 1890 and 1913. Sporadic exploration since 1913 has failed to reveal other ore deposits of economic importance.

Interactions between plutonism and detachments during metamorphic core complex formation, Serifos Island (Cyclades, Greece)

NASA Astrophysics Data System (ADS)

Rabillard, Aurélien; Arbaret, Laurent; Jolivet, Laurent; Le Breton, Nicole; Gumiaux, Charles; Augier, Romain; Grasemann, Bernhard

2015-06-01

In order to better understand the interactions between plutonic activity and strain localization during metamorphic core complex formation, the Miocene granodioritic pluton of Serifos (Cyclades, Greece) is studied. This pluton (11.6-9.5 Ma) intruded the Cycladic Blueschists during thinning of the Aegean domain along a system of low-angle normal faults belonging to the south dipping West Cycladic Detachment System (WCDS). Based on structural fieldwork, together with microstructural observations and anisotropy of magnetic susceptibility, we recognize a continuum of deformation from magmatic to brittle conditions within the magmatic body. This succession of deformation events is kinematically compatible with the development of the WCDS. The architecture of the pluton shows a marked asymmetry resulting from its interaction with the detachments. We propose a tectonic scenario for the emplacement of Serifos pluton and its subsequent cooling during the Aegean extension: (1) A first stage corresponds to the metamorphic core complex initiation and associated southwestward shearing along the Meghàlo Livadhi detachment. (2) In the second stage, the Serifos pluton has intruded the dome at shallow crustal level, piercing through the ductile/brittle Meghàlo Livadhi detachment. Southwest directed extensional deformation was contemporaneously transferred upward in the crust along the more localized Kàvos Kiklopas detachment. (3) The third stage was marked by synmagmatic extensional deformation and strain localization at the contact between the pluton and the host rocks resulting in nucleation of narrow shear zones, which (4) continued to develop after the pluton solidification.

Geospeedometry in the inverted metamorphic gradient of the Nestos Thrust Zone in central Rhodope (Northern Greece)

NASA Astrophysics Data System (ADS)

Cioldi, Stefania; Moulas, Evangelos; Burg, Jean-Pierre

2015-04-01

Thrust tectonics and inverted metamorphic gradients are major consequences of large and likely fast movements of crustal segments in compressional environments. The purpose of this study is to investigate the tectonic setting and the timescale of inverted metamorphic zonations related to crustal-scale thrusting. The aim is to contribute understanding the link between mechanical and thermal evolution of major thrust zones and to clarify the nature and the origin of orogenic heat. The Rhodope metamorphic complex (Northern Greece) is interpreted as a part of the Alpine-Himalaya orogenic belt and represents a collisional system with an association of both large-scale thrusting and pervasive exhumation tectonics. The Nestos Shear Zone overprints the suture boundary with a NNE-dipping pile of schists displaying inverted isograds. The inverted metamorphic zones start from chlorite-muscovite grade at the bottom and reach kyanite-sillimanite grades with migmatites in the upper structural levels. In order to reconstruct the thermo-tectonic evolution of inverted metamorphic zonation, reliable geochronological data are essential. 40Ar/39Ar geochronology with step-heating technique on white mica from micaschists provided a temporal resolution with the potential to characterize shearing. 40Ar/39Ar dating across the Nestos Shear Zone yields Late Eocene-Early Oligocene (40-30 Ma) cooling (~400-350° C) ages, which correspond to local thermo-deformation episodes linked to late and post-orogenic intrusions. U-Pb Sensitive High Resolution Ion Microprobe (SHRIMP) zircon geochronology on leucosomes from migmatitic orthogneisses were considered to estimate the age of peak metamorphic conditions, contemporaneous with anatexis. U-Pb ages of zircon rims specify regional partial melting during the Early Cretaceous (160-120 Ma). This is in disagreement with previous assertions, which argued that the formation of leucosomes in this region is Late Eocene (42-35 Ma) and implied multiple subductions and multiple metamorphic cycles during orogeny. Garnet geospeedometry considers the kinetic response of minerals and allowed estimating the absolute time-dependent thermal evolution by diffusive element profiles in garnet. Inverse-fitting numerical model considering Fractionation and Diffusion in GarnEt (FRIDGE) calculates garnet composition profiles by introducing P-T-t paths and bulk-rock composition of a specific sample. Preliminary results of Fe-Mg - Ca - Mn garnet fractionation-diffusion modelling indicate very short timescale (between 2 and 5 Ma) for peak metamorphic conditions in the Rhodope collisional system.

Deciphering the tectonometamorphis history of the Anarak Metamorphic Complex, Central Iran

NASA Astrophysics Data System (ADS)

Zanchetta, Stefano; Malaspina, Nadia; Zanchi, Andrea; Martin, Silvana; Benciolini, Luca; Berra, Fabrizio; Javadi, Hamid Reza; Koohpeyma, Meysam; Ghasemi, Mohammad R.; Sheikholeslami, Mohammad Reza

2014-05-01

The Cimmerian orogeny shaped the southern margin of Eurasia during the Late Permian and the Triassic. Several microplates, detached from Gondwana in the Early Permian, migrated northward to be accreted to the Eurasia margin. In the reconstruction of such orogenic event Iran is a key area. The occurrence of several "ophiolites" belt of various age, from Paleozoic to Cretaceous, poses several questions on the possibility that a single rather than multiple Paleotethys sutures occur between Eurasia and Iran. In this scenario the Anarak region in Central Iran still represents a conundrum. Contrasting geochronological, paleontological, paleomagnetic data and reported field evidence suggest different origins for the Anarak Metamorphic Complex (AMC). The AMC is either interpreted to be part of microplate of Gondwanan affinity, a relic of an accretionary wedge developed at the Eurasia margin during the Paleothetys subduction or part of the Cimmerian suture zone, occurring in NE Iran, displaced to central Iran by counterclockwise rotation of the central Iranian blocks from the Triassic. Our field structural data, petrographic and geochemical data, carried out in the frame of the DARIUS PROGRAMME, indicate that the AMC is not a single coherent block, but it consists of several units (Morghab, Chah Gorbeh, Patyar, Palhavand Gneiss, Lakh Marble, Doshak and dismembered "ophiolites") which display different tectonometamorphic evolutions. The Morghab and Chah Gorbeh units share a common history and they preserve, as a peculiar feature within metabasites, a prograde metamorphism with sin- to post-deformation growth of blueschists facies assemblages on pre-existing greenschist facies mineralogical associations. LT-HP metamorphism responsible for the growth of sodic amphibole has been recognized also within marble lenses at the southern limit of the Chah Gorbeh unit. Finally, evidence of LT-HP metamorphism also occur in the metabasites and possibly also in the serpentinites that form most of the "ophiolites" within the AMC. Structural analyses show that the Chah Gorbeh, Morghab units and the "ophiolites" have been tectonically coupled during at least two deformational phases that occurred at greenschist facies conditions and predate the LT-HP metamorphic overprint. Available geochronological data loosely constraints the subduction event in the Late Permian - Early Triassic times. Subsequent deformation events that occurred during the whole Mesozoic and the Cenozoic up to the Miocene and possibly later, resulted in folding, thrusting and faulting that dismembered the original tectonic contacts. Therefore, the correlations among deformation structures and metamorphic events in the different units are not straightforward. The other units of the AMC lack evidence of HP metamorphism, especially the Lakh Marble a large thrust sheet that occupies the uppermost structural position in the AMC. The contact with the underlying units is invariably tectonic, thus no original relationships have been preserved. So, if structural and petrographic data point out an accretionary wedge setting for the evolution of the Chah Gorbeh, Morghab and the "ophiolites", geodynamic significance and paleogeographic attribution of other units still remain controversial. In progress U-Pb dating of undeformed intrusive bodies and metamorphic minerals in the LT-HP rocks will soon help to better constrain the evolution of the ACM.

Duration of convergence at the Pacific-Gondwana plate margin: insights from accessory phase petrochronology of the Alpine Schist, New Zealand

NASA Astrophysics Data System (ADS)

Briggs, S. I.; Cottle, J. M.; Smit, M. A.; Arnush, N. F.

2016-12-01

The timing, duration and along-strike synchroneity of metamorphism and anataxis in the Alpine Schist of New Zealand is a matter of considerable debate. Our preliminary data indicate that metamorphism resulting in garnet growth occurred from 97 - 75 Ma, and anatectic melting occurred from 80 - 51 Ma. These events are contemporaneous with rifting of Zealandia from East Gondwana, and Tasman Sea spreading from 83 - 52 Ma. An important implication of these results is that Late Cretaceous convergence along the Zealandia segment of the Pacific-Gondwana plate margin may have persisted much later than previously thought, and that convergence and extension occurred coevally in adjacent areas. This poses the question: for how long did convergence continue along the Pacific-Gondwana plate margin during East Gondwana breakup? To fully decipher the multiple stages of the complex metamorphic history recorded in the Alpine Schist, we combine Lu-Hf garnet geochronology with U-Th/Pb and REE analyses of zircon and monazite. We use the newly developed `single-shot laser ablation split stream' (SS-LASS) analysis method to obtain depth profiles through 5-10 µm metamorphic zircon overgrowths at 100 nm depth resolution to constrain both the timing and petrological context of discrete metamorphic zircon (re-)crystallization events recorded in the Alpine Schist. We also employ high spatial resolution LASS analysis to target rare 5 - 20 µm monazite in thin section to augment garnet and zircon data. Our multi-accessory phase petrochronology approach is capable of resolving discrete short-duration thermal events, strengthening the geological interpretation of `mean' Lu-Hf garnet ages and discerning between an episodic versus a prolonged history of metamorphism. In addition, comparison with geochronology from anatectic pegmatites clarifies the temporal relationship between metamorphism and melting in the Alpine Schist, while providing direct constraints on the timing and duration of convergence along the Zealandia segment of the Pacific-Gondwana margin.

Newly discovered Late Triassic Baqing eclogite in central Tibet indicates an anticlockwise West-East Qiangtang collision.

PubMed

Zhang, Yu-Xiu; Jin, Xin; Zhang, Kai-Jun; Sun, Wei-Dong; Liu, Jian-Ming; Zhou, Xiao-Yao; Yan, Li-Long

2018-01-17

The Triassic eclogite-bearing central Qiangtang metamorphic belt (CQMB) in the northern Tibetan Plateau has been debated whether it is a metamorphic core complex underthrust from the Jinsha Paleo-Tethys or an in-situ Shuanghu suture. The CQMB is thus a key issue to elucidate the crustal architecture of the northern Tibetan Plateau, the tectonics of the eastern Tethys, and the petrogenesis of Cenozoic high-K magmatism. We here report the newly discovered Baqing eclogite along the eastern extension of the CQMB near the Baqing town, central Tibet. These eclogites are characterized by the garnet + omphacite + rutile + phengite + quartz assemblages. Primary eclogite-facies metamorphic pressure-temperature estimates yield consistent minimum pressure of 25 ± 1 kbar at 730 ± 60 °C. U-Pb dating on zircons that contain inclusions (garnet + omphacite + rutile + phengite) gave eclogite-facies metamorphic ages of 223 Ma. The geochemical continental crustal signature and the presence of Paleozoic cores in the zircons indicate that the Baqing eclogite formed by continental subduction and marks an eastward-younging anticlockwise West-East Qiangtang collision along the Shuanghu suture from the Middle to Late Triassic.

External micro-PIXE analysis of fluid inclusions: Test of the LABEC facility on samples of quartz veins from Apuan Alps (Italy)

NASA Astrophysics Data System (ADS)

Massi, M.; Calusi, S.; Giuntini, L.; Ruggieri, G.; Dini, A.

2008-05-01

Fluid inclusions are small portions, usually smaller than 100 μm, of fluid trapped within minerals during or after growth. Their characteristics provide therefore fundamental information on nature and evolution of fluids present in the past in different geological environments. At the LABEC laboratory in Firenze, high-salinity fluid inclusions in quartz crystals, coming from the Apuan Alps metamorphic complex, were analysed at the external scanning microbeam. Results, although still preliminary, have already provided us with hints on fluid-rock interaction processes during the metamorphism of the Apuan Alps.

Hydrological Controls on Dissolved Organic Matter Quality and Export in a Coastal River System in Southeastern USA

NASA Astrophysics Data System (ADS)

Bhattacharya, R.; Osburn, C. L.

2017-12-01

Dissolved organic matter (DOM) exported from river catchments can influence the biogeochemical processes in coastal environments with implications for water quality and carbon budget. High flow conditions are responsible for most DOM export ("pulses") from watersheds, and these events reduce DOM transformation and production by "shunting" DOM from river networks into coastal waters: the Pulse-Shunt Concept (PSC). Subsequently, the source and quality of DOM is also expected to change as a function of river flow. Here, we used stream dissolved organic carbon concentrations ([DOC]) along with DOM optical properties, such as absorbance at 350 nm (a350) and fluorescence excitation and emission matrices modeled by parallel factor analysis (PARAFAC), to characterize DOM source, quality and fluxes under variable flow conditions for the Neuse River, a coastal river system in the southeastern US. Observations were made at a flow gauged station above head of tide periodically between Aug 2011 and Feb 2013, which captured low flow periods in summer and several high flow events including Hurricane Irene. [DOC] and a350 were correlated and varied positively with river flow, implying that a large portion of the DOM was colored, humic and flow-mobilized. During high flow conditions, PARAFAC results demonstrated the higher influx of terrestrial humic DOM, and lower in-stream phytoplankton production or microbial degradation. However, during low flow, DOM transformation and production increased in response to higher residence times and elevated productivity. Further, 70% of the DOC was exported by above average flows, where 3-4 fold increases in DOC fluxes were observed during episodic events, consistent with PSC. These results imply that storms dramatically affects DOM export to coastal waters, whereby high river flow caused by episodic events primarily shunt terrestrial DOM to coastal waters, whereas low flow promotes in-stream DOM transformation and amendment with microbial DOM.

Temporal Changes in Photochemically Labile DOM and Implications for Carbon Budgets in Peatland Aquatic Systems

NASA Astrophysics Data System (ADS)

Pickard, A.

2015-12-01

Aquatic systems in peatland catchments are subject to high loading of dissolved organic matter (DOM) from surrounding terrestrial environments. However the significance of photochemical transformation of DOM in peatland carbon budgets remains poorly constrained. In this study UV irradiation experiments were conducted on water samples collected over one year from two contrasting systems in Scotland: a stream draining a peatland with high levels of DOM and a reservoir draining a peat catchment with low levels of DOM. Further samples were collected from the high DOM system during two storm events. After experimental exposure, optical and chemical analyses were employed to determine photochemical lability of the DOM pool. At both sites irradiation-induced decreases in dissolved organic carbon (DOC) as a percentage of the total carbon pool were greatest in winter, suggesting that DOM was depleted in photo-reactive molecules in summer. Seasonal variability in DOC was high at the stream site and was positively correlated with CO₂ and CO photoproduction (r2 = 0.81 and 0.83, respectively; p<0.05). Lignin phenol analyses indicate considerable contribution of peat to the DOM pool at the stream site, particularly during summer. Whilst DOC concentrations did not vary greatly during storm events, UV-Vis absorbance indicators did, signifying changing DOM source material from activation of different hydrological pathways. The most photo-reactive DOM occurred 5-10 hours after peak discharge, suggesting that storms replenish photochemically labile DOM in headwater streams. Conservative estimates using data from this study suggest that up to 7% of the DOM pool of peatland streams can be lost (primarily as CO₂ and CO) upon exposure to 8 hours of environmentally representative UV irradiation. Further investigation in field campaigns under natural UV exposure are underway to assess the importance of photodegradation of DOM as a loss pathway of carbon based gases from aquatic systems.

Dynamics of dissolved organic matter (DOM) in a typical inland lake of the Three Gorges Reservoir area: Fluorescent properties and their implications for dissolved mercury species.

PubMed

Jiang, Tao; Chen, Xueshuang; Wang, Dingyong; Liang, Jian; Bai, Weiyang; Zhang, Cheng; Wang, Qilei; Wei, Shiqiang

2018-01-15

Dissolved organic matter (DOM) plays an important environmental and ecological role in inland aquatic systems, including lakes. In this study, using fluorescence analysis, we investigated the seasonal dynamics of DOM characteristics in Changshou Lake, which is a typical inland lake in the Three Gorges Reservoir (TGR) area. We also discuss the environmental implications of DOM for mercury (Hg) dynamics. Based on the origins of two end-members, the variations in DOM observed in this study in Changshou Lake suggest that hydrological processes (e.g., terrestrial inputs resulting from runoff and humic-like component residences) and biological activities (e.g., microbial and algae growth) are the two main principal components controlling the seasonal dynamics of DOM characteristics. Furthermore, the dynamics of dissolved Hg co-varied with variations in DOM properties, rather than with dissolved organic carbon (DOC) concentrations. This indicates that the previously reported simple correlations between DOC and Hg were not comprehensive and may lead to misunderstanding the interactions between DOM and Hg. Therefore, we recommend that when using DOM-Hg correlations to evaluate the role of DOM in the environmental fate of Hg, especially in field investigations of the spatial and temporal distribution of Hg, the properties of DOM must be taken into account. Copyright © 2017 Elsevier Ltd. All rights reserved.

Mixing and photoreactivity of dissolved organic matter in the Nelson/Hayes estuarine system (Hudson Bay, Canada)

NASA Astrophysics Data System (ADS)

Guéguen, C.; Mokhtar, M.; Perroud, A.; McCullough, G.; Papakyriakou, T.

2016-09-01

This work presents the results of a 4-year study (2009-2012) investigating the mixing and photoreactivity of dissolved organic matter (DOM) in the Nelson/Hayes estuary (Hudson Bay). Dissolved organic carbon (DOC), colored DOM, and humic-like DOM decreased with increasing salinity (r2 = 0.70-0.84). Removal of DOM was noticeable at low to mid salinity range, likely due to degradation and/or adsorption to particles. DOM photobleaching rates (i.e., decrease in DOM signal resulting from exposure to solar radiation) ranged from 0.005 to 0.030 h- 1, corresponding to half-lives of 4.9-9.9 days. Dissolved organic matter from the Nelson and Hayes Rivers was more photoreactive than from the estuary where the photodegradation of terrestrial DOM decreased with increasing salinity. Coincident with the loss of CDOM absorption was an increase in spectral slope S, suggesting a decrease in DOM molecular weight. Marked differences in photoreactivity of protein- and humic-like DOM were observed with highly humidified material being the most photosensitive. Information generated by our study will provide a valuable data set for better understanding the impacts of future hydroelectric development and climate change on DOM biogeochemical dynamics in the Nelson/Hayes estuary and coastal domain. This study will constitute a reference on terrestrial DOM fate prior to building additional generating capacity on the Nelson River.

Mercury photolytic transformation affected by low-molecular-weight natural organics in water.

PubMed

He, Feng; Zheng, Wang; Liang, Liyuan; Gu, Baohua

2012-02-01

Mechanisms by which dissolved organic matter (DOM) mediates the photochemical reduction of Hg(II) in aquatic ecosystems are not fully understood, owing to the heterogeneous nature and complex structural properties of DOM. In this work, naturally occurring aromatic compounds including salicylic, 4-hydrobenzoic, anthranilic, 4-aminobenzoic, and phthalic acid were systematically studied as surrogates for DOM in order to gain an improved mechanistic understanding of these compounds in the photoreduction of Hg(II) in water. We show that the photoreduction rates of Hg(II) are influenced not only by the substituent functional groups such as -OH, -NH(2) and -COOH on the benzene ring, but also the positioning of these functional groups on the ring structure. The Hg(II) photoreduction rate decreases in the order anthranilic acid>salicylic acid>phthalic acid according to the presence of the -NH(2), -OH, -COOH functional groups on benzoic acid. The substitution position of the functional groups affects reduction rates in the order anthranilic acid>4-aminobenzoic acid and salicylic acid>4-hydroxybenzoic acid. Reduction rates correlate strongly with ultraviolet (UV) absorption of these compounds and their concentrations, suggesting that the formation of organic free radicals during photolysis of these compounds is responsible for Hg(II) photoreduction. These results provide insight into the role of low-molecular-weight organic compounds and possibly DOM in Hg photoredox transformation and may thus have important implications for understanding Hg geochemical cycling in the environment. Copyright © 2011 Elsevier B.V. All rights reserved.

Antarctic snow: metals bound to high molecular weight dissolved organic matter.

PubMed

Calace, Nicoletta; Nardi, Elisa; Pietroletti, Marco; Bartolucci, Eugenia; Pietrantonio, Massimiliana; Cremisini, Carlo

2017-05-01

In this paper we studied some heavy metals (Cu, Zn, Cd, Pb, As, U) probably associated to high molecular weight organic compounds present in the Antarctic snow. Snow-pit samples were collected and analysed for high molecular weight fraction and heavy metals bound to them by means of ultrafiltration treatment. High molecular weight dissolved organic matter (HMW-DOM) recovered by ultrafiltration showed a dissolved organic carbon concentration (HMW-DOC) of about 18-83% of the total dissolved organic carbon measured in Antarctic snow. The characterisation of HMW-DOM fraction evidenced an ageing of organic compounds going from surface layers to the deepest ones with a shift from aliphatic compounds and proteins/amino sugars to more high unsaturated character and less nitrogen content. The heavy metals associated to HMW-DOM fraction follows the order: Zn > Cu > Pb > Cd ∼ As ∼ U. The percentage fraction of metals bound to HMW-DOM respect to total metal content follows the order: Cu > Pb > Zn, Cd in agreement with humic substance binding ability (Irwing-William series). Going down to depth of trench, all metals except arsenic, showed a high concentration peak corresponding to 2.0-2.5 m layer. This result was attributed to particular structural characteristic of organic matter able to form different type of complexes (1:1, 1:2, 1:n) with metals. Copyright © 2017 Elsevier Ltd. All rights reserved.

Constraining Biomarkers of Dissolved Organic Matter Sourcing Using Microbial Incubations of Vascular Plant Leachates of the California landscape

NASA Astrophysics Data System (ADS)

Harfmann, J.; Hernes, P.; Chuang, C. Y.; Kaiser, K.; Spencer, R. G.; Guillemette, F.

2017-12-01

Source origin of dissolved organic matter (DOM) is crucial in determining reactivity, driving chemical and biological processing of carbon. DOM source biomarkers such as lignin (a vascular plant marker) and D-amino acids (bacterial markers) are well-established tools in tracing DOM origin and fate. The development of high-resolution mass spectrometry and optical studies has expanded our toolkit; yet despite these advances, our understanding of DOM sources and fate remains largely qualitative. Quantitative data on DOM pools and fluxes become increasingly necessary as we refine our comprehension of its composition. In this study, we aim to calibrate and quantify DOM source endmembers by performing microbial incubations of multiple vascular plant leachates, where total DOM is constrained by initial vascular plant input and microbial production. Derived endmembers may be applied to endmember mixing models to quantify DOM source contributions in aquatic systems.

On the use of hydroxyl radical kinetics to assess the number-average molecular weight of dissolved organic matter.

PubMed

Appiani, Elena; Page, Sarah E; McNeill, Kristopher

2014-10-21

Dissolved organic matter (DOM) is involved in numerous environmental processes, and its molecular size is important in many of these processes, such as DOM bioavailability, DOM sorptive capacity, and the formation of disinfection byproducts during water treatment. The size and size distribution of the molecules composing DOM remains an open question. In this contribution, an indirect method to assess the average size of DOM is described, which is based on the reaction of hydroxyl radical (HO(•)) quenching by DOM. HO(•) is often assumed to be relatively unselective, reacting with nearly all organic molecules with similar rate constants. Literature values for HO(•) reaction with organic molecules were surveyed to assess the unselectivity of DOM and to determine a representative quenching rate constant (k(rep) = 5.6 × 10(9) M(-1) s(-1)). This value was used to assess the average molecular weight of various humic and fulvic acid isolates as model DOM, using literature HO(•) quenching constants, kC,DOM. The results obtained by this method were compared with previous estimates of average molecular weight. The average molecular weight (Mn) values obtained with this approach are lower than the Mn measured by other techniques such as size exclusion chromatography (SEC), vapor pressure osmometry (VPO), and flow field fractionation (FFF). This suggests that DOM is an especially good quencher for HO(•), reacting at rates close to the diffusion-control limit. It was further observed that humic acids generally react faster than fulvic acids. The high reactivity of humic acids toward HO(•) is in line with the antioxidant properties of DOM. The benefit of this method is that it provides a firm upper bound on the average molecular weight of DOM, based on the kinetic limits of the HO(•) reaction. The results indicate low average molecular weight values, which is most consistent with the recent understanding of DOM. A possible DOM size distribution is discussed to reconcile the small nature of DOM with the large-molecule behavior observed in other studies.

Modeling Effects of Lability on Microbial Uptake of DOM in River Reaches

NASA Astrophysics Data System (ADS)

Li, A.; Drummond, J. D.; Bowen, J. C.; Cory, R. M.; Kaplan, L.; Packman, A. I.

2017-12-01

Rivers are hotspots for biological degradation of dissolved organic matter (DOM), contributing to 1.8 petagrams of carbon emissions per year. DOM represents approximately 60% of the total mass of organic carbon transported within river networks, fueling stream ecosystem metabolism. Not all DOM is biodegradable, biodegradation rates vary based on lability, and lability decreases with reaction time. Fluorescent fractions of DOM (FDOM) are often used as proxies of DOM lability. Humic-like FDOM, previously considered recalcitrant and thought to contribute minimally to the biodegradable DOM pools, has recently been shown to contribute more than 50% to DOM uptake in bioreactor columns colonized by bacteria in stream water. Protein-like FDOM, a proxy for the biodegradable DOM pool, also contributes to the recalcitrant DOM pool in bioreactors. However, the contribution of different lability pools to DOM uptake at the reach scale remains elusive. Here we combine local-scale results from a bioreactor study and measures of stream geomorphology parameters to model reach-scale DOM uptake in White Clay Creek, a Pennsylvania piedmont stream with an intact, forested riparian zone and inputs from upland agriculture. Steady state modeling of a point-source, continuous injection of FDOM shows that humic-like FDOM contributes up to 80% of the total removal of FDOM at the reach scale, suggesting its importance to in-stream DOM uptake. Tryptophan-like FDOM, a protein-like FDOM, contributes to 80% of the remaining fraction of FDOM at the reach scale that incorporates longer timescales of transport and retention. This is consistent with recent local-scale findings that the lability of tryptophan-like FDOM decreases substantially with reaction time in bioreactors, such that it becomes much more recalcitrant as it travels downstream. Steady state modeling of a distributed source, continuous injection of FDOM shows that contributing sources distribute differently along the river reach for each FDOM component, due to their different uptake patterns. Thus, variations of DOM lability are important for estimating reach-scale microbial uptake and contributing sources of in-stream DOM.

Stream Dissolved Organic Matter Quantity and Quality Along a Wetland-Cropland Catchment Gradient

NASA Astrophysics Data System (ADS)

McDonough, O.; Hosen, J. D.; Lang, M. W.; Oesterling, R.; Palmer, M.

2012-12-01

Wetlands may be critical sources of dissolved organic matter (DOM) to stream networks. Yet, more than half of wetlands in the continental United States have been lost since European settlement, with the majority of loss attributed to agriculture. The degree to which agricultural loss of wetlands impacts stream DOM is largely unknown and may have important ecological implications. Using twenty headwater catchments on the Delmarva Peninsula (Maryland, USA), we investigated the seasonal influence of wetland and cropland coverage on downstream DOM quantity and quality. In addition to quantifying bulk downstream dissolved organic carbon (DOC) concentration, we used a suite of DOM UV-absorbance metrics and parallel factor analysis (PARAFAC) modeling of excitation-emission fluorescence spectra (EEMs) to characterize DOM composition. Percent bioavailable DOC (%BDOC) was measured during the Spring sampling using a 28-day incubation. Percent wetland coverage and % cropland within the watersheds were significantly negatively correlated (r = -0.93, p < 0.001). Results show that % wetland coverage was positively correlated with stream DOM concentration, molecular weight, aromaticity, humic-like fluorescence, and allochthonous origin. Conversely, increased wetland coverage was negatively correlated with stream DOM protein-like fluorescence. Percent BDOC decreased with DOM humic-like fluorescence and increased with protein-like fluorescence. We observed minimal seasonal interaction between % wetland coverage and DOM concentration and composition across Spring, Fall, and Winter sampling seasons. However, principal component analysis suggested more pronounced seasonal differences exist in stream DOM. This study highlights the influence of wetlands on downstream DOM in agriculturally impacted landscapes where loss of wetlands to cultivation may significantly alter stream DOM quantity and quality.

Spatial pattern of dissolved organic matter (DOM) along a stream drainage in a forested, Piedmont catchment

NASA Astrophysics Data System (ADS)

Inamdar, S. P.; Singh, S.

2013-12-01

Understanding how dissolved organic matter (DOM) varies spatially in catchments and the processes and mechanisms that regulate this variation is critical for developing accurate and reliable models of DOM. We determined the concentrations and composition of DOM at multiple locations along a stream drainage network in a 79 ha forested, Piedmont, watershed in Maryland, USA. DOM concentrations and composition was compared for five stream locations during baseflow (drainage areas - 0.62, 3.5, 4.5, 12 and 79 ha) and three locations (3.5, 12, 79 ha) for storm flow. Sampling was conducted by manual grab samples and automated ISCO samplers. DOM composition was characterized using a suite of spectrofluorometric indices which included - HIX, a254, and FI. A site-specific PARAFAC model was also developed for DOM fluorescence to determine the humic-, fulvic-, and protein-like DOM constituents. Hydrologic flow paths during baseflow and stormflow were characterized for all stream locations using an end-member mixing model (EMMA). DOM varied notably across the sampled positions for baseflow and stormflow. During baseflow, mean DOC concentrations for the sampled locations ranged between 0.99-3.1 mg/L whereas for stormflow the range was 5.22-8.11 mg/L. Not surprisingly, DOM was more humic and aromatic during stormflow versus baseflow. The 3.5 ha stream drainage location that contained a large wetland yielded the highest DOC concentration as well as the most humic and aromatic DOM, during both, baseflow and stormflow. In contrast, a headwater stream location (0.62 ha) that received runoff from a groundwater seep registered the highest mean value for % protein-like DOM (30%) and the lowest index for aromaticity (mean a254 = 6.52) during baseflow. During stormflow, the mean % protein-like DOM was highest at the largest 79 ha drainage location (mean = 11.8%) and this site also registered the lowest mean value for a254 (46.3). Stream drainage locations that received a larger proportion of runoff along surficial flow paths produced a more aromatic and humic DOM with high DOC concentrations; whereas those with a greater proportion of groundwater contributions produced DOM with greater % of protein-like content. Overall, our observations suggest that occurrence of wetlands and the nature of hydrologic flow paths were the key determinants for the spatial pattern of DOM.

Compositions and constituents of freshwater dissolved organic matter isolated by reverse osmosis.

PubMed

Zhang, Yulong; Huang, Wen; Ran, Yong; Mao, Jingdong

2014-08-15

Dissolved organic matter (DOM) from riverine and lacustrine water was isolated using a reverse osmosis (RO) system. Solid-state (13)C nuclear magnetic resonance ((13)C NMR) was used to quantitatively evaluate the compositions and constituents of DOM, which are compared with previous investigations on marine DOM. Results indicated that concentration factor (CF) was a key metric controlling yield and sorption of DOM on the RO system. The sorption was likely non-selective, based on the (13)C NMR and δ(13)C analyses. Carbohydrates and lipids accounted for 25.0-41.5% and 30.2-46.3% of the identifiable DOM, followed by proteins (18.2-19.8%) and lignin (7.17-12.8%). The freshwater DOM contained much higher alkyl and aromatic C but lower alkoxyl and carboxyl C than marine DOM. The structural difference was not completely accounted for by using structure of high molecular weight (HMW) DOM, suggesting a size change involved in transformations of DOM during the transport from rivers to oceans. Copyright © 2014 Elsevier Ltd. All rights reserved.

High-field NMR spectroscopy and FTICR mass spectrometry: powerful discovery tools for the molecular level characterization of marine dissolved organic matter

NASA Astrophysics Data System (ADS)

Hertkorn, N.; Harir, M.; Koch, B. P.; Michalke, B.; Schmitt-Kopplin, P.

2013-03-01

High-performance, non-target, high-resolution organic structural spectroscopy was applied to solid phase extracted marine dissolved organic matter (SPE-DOM) isolated from four different depths in the open South Atlantic Ocean off the Angola coast (3° E, 18° S; Angola Basin) and provided molecular level information with extraordinary coverage and resolution. Sampling was performed at depths of 5 m (Angola Current; near-surface photic zone), 48 m (Angola Current; fluorescence maximum), 200 m (still above Antarctic Intermediate Water, AAIW; upper mesopelagic zone) and 5446 m (North Atlantic Deep Water, NADW; abyssopelagic, ~30 m above seafloor) and produced SPE-DOM with near 40% carbon yield and beneficial nuclear magnetic resonance (NMR) relaxation properties, a crucial prerequisite for the acquisition of NMR spectra with excellent resolution. 1H and 13C NMR spectra of all four marine SPE-DOM showed smooth bulk envelopes, reflecting intrinsic averaging from massive signal overlap, with a few percent of visibly resolved signatures and variable abundances for all major chemical environments. The abundance of singly oxygenated aliphatics and acetate derivatives in 1H NMR spectra declined from surface to deep marine SPE-DOM, whereas C-based aliphatics and carboxyl-rich alicyclic molecules (CRAM) increased in abundance. Surface SPE-DOM contained fewer methyl esters than all other samples, likely a consequence of direct exposure to sunlight. Integration of 13C NMR spectra revealed continual increase of carboxylic acids and ketones from surface to depth, reflecting a progressive oxygenation, with concomitant decline of carbohydrate-related substructures. Aliphatic branching increased with depth, whereas the fraction of oxygenated aliphatics declined for methine, methylene and methyl carbon. Lipids in the oldest SPE-DOM at 5446 m showed a larger share of ethyl groups and methylene carbon than observed in the other samples. Two-dimensional NMR spectra showed exceptional resolution and depicted resolved molecular signatures in excess of a certain minimum abundance. Classical methyl groups terminating aliphatic chains represented ~15% of total methyl in all samples investigated. A noticeable fraction of methyl (~2%) was bound to olefinic carbon. Methyl ethers were abundant in surface marine SPE-DOM, and the chemical diversity of carbohydrates was larger than that of freshwater and soil DOM. In all samples, we identified sp2-hybridized carbon chemical environments with discrimination of isolated and conjugated olefins and α,β-unsaturated double bonds. Olefinic proton and carbon atoms were more abundant than aromatic ones; olefinic unsaturation in marine SPE-DOM will be more directly traceable to ultimate biogenic precursors than aromatic unsaturation. The abundance of furan, pyrrol and thiophene derivatives was marginal, whereas benzene derivatives, phenols and six-membered nitrogen heterocycles were prominent; a yet unassigned set of six-membered N-heterocycles with likely more than one single nitrogen occurred in all samples. Various key polycyclic aromatic hydrocarbon substructures suggested the presence of thermogenic organic matter at all water depths. Progressive NMR cross-peak attenuation from surface to deep marine SPE-DOM was particularly strong in COSY NMR spectra and indicated a continual disappearance of biosignatures as well as entropy gain from an ever increased molecular diversity. Nevertheless, a specific near-seafloor SPE-DOM signature of unsaturated molecules recognized in both NMR and Fourier transform ion cyclotron mass spectrometry (FTICR/MS) possibly originated from sediment leaching. The conformity of key NMR and FTICR/MS signatures suggested the presence of a large set of identical molecules throughout the entire ocean column even though the investigated water masses belonged to different oceanic regimes and currents. FTICR/MS showed abundant CHO, CHNO, CHOS and CHNOS molecular series with slightly increasing numbers of mass peaks and average mass from surface to bottom SPE-DOM. The proportion of CHO and CHNO negative ions increased from surface to depth, whereas CHOS and especially CHNOS molecular series markedly declined. While certain rather aliphatic CHOS and CHNOS ions were observed solely in the surface, deep marine SPE-DOM was enriched in unique unsaturated and rather oxygenated CHO and CHNO molecular series. With the exception of abyssopelagic SPE-DOM at 5446 m, which showed a peculiar CHOS chemistry of unsaturated carbon and reduced sulphur (black sulphur), CHO and CHNO molecular series contributed ~87% to total positive electrospray ionization FTICR mass peak integral, with a near constant ratio of CHNO / CHO molecular compositions near 1.13 ± 0.05. In case of all four marine SPE-DOM, remarkably disparate average elemental compositions as determined from either MS and NMR spectra were observed, caused by a pronounced ionization selectivity in electrospray ionization FTICR/MS. The study demonstrates that the exhaustive characterization of complex unknowns in marine DOM will enable a meaningful classification of individual marine biogeosignatures. Future in-depth functional biodiversity studies with a clear understanding of DOM structure and function might eventually lead to a novel, unified perception of biodiversity and biogeochemistry.

The Rondonian-San Ignacio Province in the SW Amazonian Craton: An overview

NASA Astrophysics Data System (ADS)

Bettencourt, Jorge Silva; Leite, Washington Barbosa; Ruiz, Amarildo Salina; Matos, Ramiro; Payolla, Bruno Leonelo; Tosdal, Richard M.

2010-01-01

The Rondonian-San Ignacio Province (1.56-1.30 Ga) is a composite orogen created through successive accretion of arcs, ocean basin closure and final oblique microcontinent-continent collision. The effects of the collision are well preserved mostly in the Paraguá Terrane (Bolivia and Mato Grosso regions) and in the Alto Guaporé Belt and the Rio Negro-Juruena Province (Rondônia region), considering that the province was affected by later collision-related deformation and metamorphism during the Sunsás Orogeny (1.25-1.00 Ga). The Rondonian-San Ignacio Province comprises: (1) the Jauru Terrane (1.78-1.42 Ga) that hosts Paleoproterozoic basement (1.78-1.72 Ga), and the Cachoeirinha (1.56-1.52 Ga) and the Santa Helena (1.48-1.42 Ga) accretionary orogens, both developed in an Andean-type magmatic arc; (2) the Paraguá Terrane (1.74-1.32 Ga) that hosts pre-San Ignacio units (>1640 Ma: Chiquitania Gneiss Complex, San Ignacio Schist Group and Lomas Manechis Granulitic Complex) and the Pensamiento Granitoid Complex (1.37-1.34 Ga) developed in an Andean-type magmatic arc; (3) the Rio Alegre Terrane (1.51-1.38 Ga) that includes units generated in a mid-ocean ridge and an intra-oceanic magmatic arc environments; and (4) the Alto Guaporé Belt (<1.42-1.34 Ga) that hosts units developed in passive marginal basin and intra-oceanic arc settings. The collisional stage (1.34-1.32 Ga) is characterized by deformation, high-grade metamorphism, and partial melting during the metamorphic peak, which affected primarily the Chiquitania Gneiss Complex and Lomas Manechis Granulitic Complex in the Paraguá Terrane, and the Colorado Complex and the Nova Mamoré Metamorphic Suite in the Alto Guaporé Belt. The Paraguá Block is here considered as a crustal fragment probably displaced from its Rio Negro-Juruena crustal counterpart between 1.50 and 1.40 Ga. This period is characterized by extensive A-type and intra-plate granite magmatism represented by the Rio Crespo Intrusive Suite (ca. 1.50 Ga), Santo Antonio Intrusive Suite (1.40-1.36 Ga), and the Teotônio Intrusive Suite (1.38 Ga). Magmatism of these types also occur at the end of the Rondonian-San Ignacio Orogeny, and are represented by the Alto Candeias Intrusive Suite (1.34-1.36 Ga), and the São Lourenço-Caripunas Intrusive Suite (1.31-1.30 Ga). The cratonization of the province occurred between 1.30 and 1.25 Ga.

Preliminary geologic map of the Murrieta 7.5' quadrangle, Riverside County, California

USGS Publications Warehouse

Kennedy, Michael P.; Morton, Douglas M.

2003-01-01

The Murrieta quadrangle is located in the northern part of the Peninsular Ranges Province and includes parts of two structural blocks, or structural subdivisions of the province. The quadrangle is diagonally crossed by the active Elsinore fault zone, a major fault zone of the San Andreas fault system, and separates the Santa Ana Mountains block to the west from the Perris block to the east. Both blocks are relatively stable internally and within the quadrangle are characterized by the presence of widespread erosional surfaces of low relief. The Santa Ana Mountains block, in the Murrieta quadrangle, is underlain by undifferentiated, thick-layered, granular, impure quartzite and well-layered, fissile, phyllitic metamorphic rock of low metamorphic grade. Both quartzite and phyllitic rocks are Mesozoic. Unconformably overlying the metamorphic rocks are remnants of basalt flows having relatively unmodified flow surfaces. The age of the basalt is about 7-8Ma. Large shallow depressions on the surface of the larger basalt remnants form vernal ponds that contain an endemic flora. Beneath the basalt the upper part of the metamorphic rocks is deeply weathered. The weathering appears to be the same as the regional Paleocene saprolitic weathering in southern California. West of the quadrangle a variable thickness sedimentary rock, physically resembling Paleogene rocks, occurs between the basalt and metamorphic rock. Where not protected by the basalt, the weathered rock has been removed by erosion. The dominant feature on the Perris block in the Murrieta quadrangle is the south half of the Paloma Valley ring complex, part of the composite Peninsular Ranges batholith. The complex is elliptical in plan view and consists of an older ring-dike with two subsidiary short-arced dikes that were emplaced into gabbro by magmatic stoping. Small to large stoped blocks of gabbro are common within the ring-dikes. A younger ring-set of hundreds of thin pegmatite dikes occur largely within the central part of the complex. These pegmatite dikes were emplaced into a domal fracture system, apparently produced by cauldron subsidence, and include in the center of the complex, a number of flat-floored granophyre bodies. The granophyre is interpreted to be the result of pressure quenching of pegmatite magma. Along the eastern edge of the quadrangle is the western part of a large septum of medium metamorphic grade Mesozoic schist. A dissected basalt flow caps the Hogbacks northeast of Temecula, and represents remnants of a channel filling flow. Beneath the basalt is a thin deposit of stream gravel. Having an age of about 10Ma, this basalt is about 2-3Ma older than the basalt flows in the Santa Ana Mountains. The Elsinore fault zone forms a complex of pull-apart basins. The west edge of the fault zone, the Willard Fault, is marked by the high, steep eastern face of the Santa Ana Mountains. The east side of the zone, the Wildomar Fault, forms a less pronounced physiographic step. In the center of the quadrangle a major splay of the fault zone, the Murrieta Hot Springs Fault, strikes east. Branching of the fault zone causes the development of a broad alluvial valley between the Willard Fault and the Murrieta Hot Springs Fault. All but the axial part of the zone between the Willard and Wildomar Faults consist of dissected Pleistocene sedimentary units. The axial part of the zone is underlain by Holocene and latest Pleistocene sedimentary units.

The impact of solar radiation on the use of dissolved organic matter in two Ozark Streams: Possible role of photo-enhanced humification

NASA Astrophysics Data System (ADS)

Townsend, S. L.; Ziegler, S. E.

2005-05-01

The effect of solar radiation on dissolved organic matter (DOM) utilization was studied in two contrasting streams from June 2002 through October 2004. Moores Creek is an agricultural stream with elevated nutrient and dissolved organic carbon (DOC) concentrations. Huey Hollow is a forested stream with low nutrient and DOC concentrations. A series of experiments were conducted seasonally to assess how solar radiation influenced DOM utilization. Exposure of DOM to solar radiation significantly decreased its utilization during most seasons in both streams. Each stream experienced one seasonal period when exposure of DOM significantly increased bacterial production; during these periods, DOM appeared to be the least bioavailable and most photochemically reactive. Interestingly, in spring when bioavailability of DOM was lowest in Moores Creek solar radiation exposure further reduced DOM bioavailability. Elevated ammonium concentrations during this spring experiment suggest photochemically-enhanced humification may have been an important mechanism influencing DOM cycling. Bioassays using 15N-labeled ammonium indicated no significant effect of elevated ammonium on the utilization of DOM in either stream in fall 2004. Detection of elevated 15N in the DOM fractions, however, would reveal light stimulated humification under elevated ammonium concentrations not detected with the bioassay.

Effects of dissolved organic matter from a eutrophic lake on the freely dissolved concentrations of emerging organic contaminants.

PubMed

Xiao, Yi-Hua; Huang, Qing-Hui; Vähätalo, Anssi V; Li, Fei-Peng; Chen, Ling

2014-08-01

The authors studied the effects of dissolved organic matter (DOM) on the bioavailability of bisphenol A (BPA) and chloramphenicol by measuring the freely dissolved concentrations of the contaminants in solutions containing DOM that had been isolated from a mesocosm in a eutrophic lake. The abundance and aromaticity of the chromophoric DOM increased over the 25-d mesocosm experiment. The BPA freely dissolved concentration was 72.3% lower and the chloramphenicol freely dissolved concentration was 56.2% lower using DOM collected on day 25 than using DOM collected on day 1 of the mesocosm experiment. The freely dissolved concentrations negatively correlated with the ultraviolent absorption coefficient at 254 nm and positively correlated with the spectral slope of chromophoric DOM, suggesting that the bioavailability of these emerging organic contaminants depends on the characteristics of the DOM present. The DOM-water partition coefficients (log KOC ) for the emerging organic contaminants positively correlated with the aromaticity of the DOM, measured as humic acid-like fluorescent components C1 (excitation/emission=250[313]/412 nm) and C2 (excitation/emission=268[379]/456 nm). The authors conclude that the bioavailability of emerging organic contaminants in eutrophic lakes can be affected by changes in the DOM. © 2014 SETAC.

Dissolved organic matter reduces algal accumulation of methylmercury

USGS Publications Warehouse

Luengen, Allison C.; Fisher, Nicholas S.; Bergamaschi, Brian A.

2012-01-01

Dissolved organic matter (DOM) significantly decreased accumulation of methylmercury (MeHg) by the diatom Cyclotella meneghiniana in laboratory experiments. Live diatom cells accumulated two to four times more MeHg than dead cells, indicating that accumulation may be partially an energy-requiring process. Methylmercury enrichment in diatoms relative to ambient water was measured by a volume concentration factor (VCF). Without added DOM, the maximum VCF was 32 x 104, and the average VCF (from 10 to 72 h) over all experiments was 12.6 x 104. At very low (1.5 mg/L) added DOM, VCFs dropped by approximately half. At very high (20 mg/L) added DOM, VCFs dropped 10-fold. Presumably, MeHg was bound to a variety of reduced sulfur sites on the DOM, making it unavailable for uptake. Diatoms accumulated significantly more MeHg when exposed to transphilic DOM extracts than hydrophobic ones. However, algal lysate, a labile type of DOM created by resuspending a marine diatom in freshwater, behaved similarly to a refractory DOM isolate from San Francisco Bay. Addition of 67 μM L-cysteine resulted in the largest drop in VCFs, to 0.28 x 104. Although the DOM composition influenced the availability of MeHg to some extent, total DOM concentration was the most important factor in determining algal bioaccumulation of MeHg.

Controls on the dynamics of dissolved organic matter in soils: A review

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kalbitz, K.; Solinger, S.; Park, J.H.

Dissolved organic matter (DOM) in soils plays an important role in the biogeochemistry of carbon, nitrogen, and phosphorus, in pedogenesis, and in the transport of pollutants in soils. The aim of this review is to summarize the recent literature about controls on DOM concentrations and fluxes in soils. The authors focus on comparing results between laboratory and field investigations and on the differences between the dynamics of dissolved organic carbon (DOC), nitrogen (DON), and phosphorus (DOP). Both laboratory and field studies show that litter and humus are the most important DOM sources in soils. However, it is impossible to quantifymore » the individual contributions of each of these sources to DOM release. In addition, it is not clear how changes in the pool sizes of litter or humus may affect DOM release. High microbial activity, high fungal abundance, and any conditions that enhance mineralization all promote high DOM concentrations. However, under field conditions, hydrologic variability in soil horizons with high carbon contents may be more important than biotic controls. In subsoil horizons with low carbon contents, DOM may be adsorbed strongly to mineral surfaces, resulting in low DOM concentrations in the soil solution. There are strong indications that microbial degradation of DOM also controls the fate of DOM in the soil.« less

Comprehensive assessment of precursors, diagenesis, and reactivity to water treatment of dissolved and colloidal organic matter

USGS Publications Warehouse

Leenheer, J.A.

2004-01-01

A comprehensive isolation, fractionation, and characterization research approach was developed for dissolved and colloidal organic matter (DOM) in water, and it was applied to various surface- and groundwaters to assess DOM precursors, DOM diagenesis, and DOM reactivity to water treatment processes. Major precursors for natural DOM are amino sugars, condensed tannins, and terpenoids. Amino sugar colloids derived from bacterial cell walls are incompletely removed by drinking water treatment and foul reverse osmosis membranes, but are nearly quantitatively removed by soil/aquifer treatment. When chlorinated, amino sugars produce low yields of regulated disinfection by-products (DBFs) but they produce significant chlorine demand that is likely caused by chlorination of free amino groups. Condensed tannins are major precursors for "blackwater" DOM such as that found in the Suwannee River. This DOM produces high yields of DBPs upon chorination, and is efficiently removed by coagulation/flocculation treatment. Terpenoid-derived DOM appears to be biologically refractory, infiltrates readily into groundwater with little removal by soil/aquifer treatment, gives low DBF-yields upon chlorination and is poorly removed by coagulation/flocculation treatments. Peptides derived from proteins are major components of the base DOM fraction (10% or less of the mass of DOM), and this fraction produces large yields of haloacetonitriles upon chorination.

Aspects of the evolution of the West Antarctic margin of Gondwanaland

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grunow, A.M.

1989-01-01

A combination of paleomagnetism, structural field mapping, microprobe analysis, microfabric analysis and {sup 40}Ar/{sup 39}Ar geochronology was used to elucidate the history of the West Antarctic crustal block and the evolution of subduction complexes along the Scotia Ridge. West Antarctica is composed of four crustal blocks whose relationship to East Antarctica and to each other throughout the Phanerozoic is not well known. These blocks are: the Ellsworth-Whitmore Mountains (EWM); the Antarctic Peninsula (AP); Thurston Island (TI); Marie Byrd Land (MBL). Paleomagnetic sampling and analysis were conducted on rocks from the EWM and TI blocks in the hope of constraining themore » motion of these blocks and the opening history of the Weddell Sea. The paleomagnetic results suggest that the AP, EWM, and TI blocks have moved relative to East Antarctica prior to the mid-Cretaceous and that the main opening of the Weddell Sea was between the Early and mid-Cretaceous. Detailed field mapping was conducted on the subduction complexes of the Scotia Metamorphic Complex (SMC) on Smith Island and Elephant Island (Antarctica). Polyphase ductile deformation characterizes the Smith Island and Elephant Island tectonites. Microprobe analyses indicate that the blue amphiboles from both areas are primary crossite. Pressure-temperature estimates for Smith Island blueschist metamorphism are {approximately}350 C at 6-7 kbars. The {sup 40}Ar/{sup 39}Ar geochronology indicates a complex thermal evolution for the SMC. The north to south increase in intensity of deformation and metamorphism on Elephant Island corresponds to decrease in {sup 40}Ar/{sup 39}Ar age. Uplift of the Smith Island blueschists occurred since 47 Ma while most of the uplift on Elephant Island occurred since {approximately}102 Ma.« less

The extending lithosphere (Arthur Holmes Medal Lecture)

NASA Astrophysics Data System (ADS)

Brun, Jean-Pierre

2017-04-01

Extension of the lithosphere gives birth to a wide range of structures, with characteristic widths between 10 and 1000 km, which includes continental rifts, passive margins, oceanic rifts, core complexes, or back-arc basins. Because the rheology of rocks strongly depends on temperature, this variety of extensional structures falls in two broad categories of extending lithospheres according to the initial Moho temperature TM. "Cold extending systems", with TM < 750°C and mantle-dominated strength, lead to narrow rifts and, if extension is maintained long enough, to passive margins and then mantle core complexes. "Hot extending systems", with TM > 750°C and crustal-dominated strength, lead, depending on strain rate, to either wide rifts or metamorphic core complexes. A much less quoted product of extension is the exhumation of high-pressure (HP ) metamorphic rocks occurring in domains of back-arc extension driven by slab rollback (e.g. Aegean; Appennines-Calabrian) or when the subduction upper plate undergoes extension for plate kinematics reasons (e.g. Norwegian Caledonides; Papua New Guinea). In these tectonic environments, well-documented pressure-temperature-time (P - T - t) paths of HP rocks show a two-stage retrogression path whose the first part corresponds to an isothermal large pressure drop ΔP proportional to the maximum pressure Pmax recorded by the rocks. This linear relation between ΔP and Pmax, which likely results from a stress switch between compression and extension at the onset of exhumation, is in fact observed in all HP metamorphism provinces worldwide, suggesting that the exhumation of HP rocks in extension is a general process rather than an uncommon case. In summary, the modes and products of extension are so diverse that, taken all together, they constitute a very versatile natural laboratory to decipher the rheological complexities of the continental lithosphere and their mechanical implications.

Revealing the significance and polyphase tectonothermal evolution of a major metamorphic unit in an orogen: the central Sanandaj-Sirjan zone, Zagros Mts., Iran

NASA Astrophysics Data System (ADS)

Shakerardakani, Farzaneh; Neubauer, Franz; Genser, Johann; Liu, Xiaoming; Dong, Yunpeng; Monfaredi, Behzad; Benroider, Manfred; Finger, Fritz; Waitzinger, Michael

2016-04-01

The Dorud-Azna region in the central Sanandaj-Sirjan metamorphic belt plays a key role in promoting the tectonic evolution of Zagros orogen, within the frame of the Arabia-Eurasia collision zone. From footwall to hangingwall, structural data combined with the U-Pb zircon and extensive 40Ar-39Ar mineral dating survey demonstrate three metamorphosed tectonic units, which include: (1) The Triassic June complex is metamorphosed within greenschist facies conditions, overlain by (2) the amphibolite-grade metamorphic Galeh-Doz orthogneiss, which is intruded by mafic dykes, and (3) the Amphibolite-Metagabbro unit. To the east, these units were intruded by the Jurassic Darijune gabbro. We present U-Pb detrital zircon ages of a garnet-micaschist from the Amphibolite-Metagabbro unit, which yield six distinctive age groups, including a previously unrecognized Late Grenvillian age population at ~0.93 to 0.99 Ga. We speculate that this unique Late Grenvillian group coupled with biogeographic evidence suggests either relationship with the South China craton or to the "Gondwana superfan". The laser ablation ICP-MS U-Pb zircon ages of 608 ± 18 Ma and 588 ± 41 Ma of the granitic Galeh-Doz orthogneiss reveals a Panafrican basement same as known from the Yazd block of Central Iran. Geochemistry and Sr-Nd isotopes of alkaline and subalkaline mafic dykes within the Galeh-Doz orthogneiss show OIB-type to MORB-type and indicate involvement of both depleted and enriched sources for its genesis. The new 40Ar-39Ar amphibole age of ca. 322.2 ± 3.9 Ma from the alkaline mafic dyke implies Carboniferous cooling age after intrusion. The metagabbros (including the Dare-Hedavand metagabbro with a 206Pb/238U age of 314.6 ± 3.7 Ma) and amphibolites with E-MORB geochemical signature of the Amphibolite-Metagabbro unit represent an Upper Paleozoic rift. The geochemical composition of the Triassic greenschist facies metamorphosed June complex, implying formation in a same, but younger tectonic environment. The Darijune gabbro with the mean U-Pb zircon age of 170.2 ± 3.1 Ma postdates greenschist facies-grade metamorphism. This age marks the beginning of the initial subduction of Neotethyan oceanic in a continental arc setting. The best average P-T estimates for the metamorphic mineral assemblages of the Galeh-Doz orthogneiss range between 600 ± 50 °C at 2 ± 0.8 kbar. The subsequent cooling history after an amphibolite facies-grade metamorphism has been constrained with 40Ar-39Ar amphibole ages of plateau ages between 240-260 Ma. The estimate P-T conditions for the Carboniferous metagabbro from core (580 ± 50 °C, 4.0 ± 0.8 kbar) to rim (700 ± 20 °C, 7.5 ± 0.7 kbar) are in favor of a prograde P-T path. The new 40Ar-39Ar mineral ages integrated with structural field and microfabric studies reveals that the amphibolite-grade Carboniferous metagabbro indicate a Late Carboniferous age of amphibolite-grade metamorphism associated with ductile deformation of the new-detected Galeh-Doz nappe (Galeh-Doz orthogneiss and Amphibolite-Metagabbro unit). In the same unit, two lenses of metapelite including a garnet-muscovite-biotite schist give a P-T estimate of garnet cores from 640 ± 20 °C at 6.2 ± 0.8 kbar and garnet rims from 680 ± 20 °C at 7.2 ± 1.0 kbar, as well as garnet-biotite schist that yield lower P-T conditions, which vary from 620 °C at 5.5 ± 0.5 kbar in garnet cores to 600 ± 30 °C at 4.0 ± 1.0 kbar in garnet rims. Chemical monazite ages from garnet micaschists are at 322 ± 28 Ma. 40Ar-39Ar experiments on white mica in the first and second types yield staircase patterns from ca. 36 to 170 Ma and a plateau age of 137.84 ± 0.65 Ma, respectively. Taking all data together, we suggest that amphibolite-grade metamorphism is Carboniferous and is overprinted by two events: (1) during Late Jurassic- Cretaceous during ductile dextral transpressive nappe emplacement of the Galeh-Doz nappe over the June complex (peak conditions of greenschist facies metamorphism at ca. 107 Ma followed by an overprint at 50 Ma) and (2) in ca. 50-32 Ma during shortening and emplacement of the metamorphic nappe complexes over unmetamorphic units of the Zagros orogen.

Electrochemically modified dissolved organic matter accelerates the combining photodegradation and biodegradation of 17α-ethinylestradiol in natural aquatic environment.

PubMed

He, Huan; Huang, Bin; Fu, Gen; Xiong, Dan; Xu, Zhixiang; Wu, Xinhao; Pan, Xuejun

2018-06-15

The photochemical conversion and microbial transformation of pollutants mediated by dissolved organic matter (DOM), including 17α-ethinylestradiol (EE2), are often accompanied in natural water. However, there are few studies to explore the connection and mechanism between the two processes. This research aims to investigate the mechanism of DOM after electrochemically modification mediated EE2 combining photodegradation and biodegradation in the environment and it want to explain the natural phenomena of DOM after electrochemical advanced treatment entering the water environment mediated EE2 natural degradation. The results showed that combining photodegradation with biodegradation rates of EE2 mediated by DOM and electrochemically modified DOM (E-DOM) were promoted obviously. The efficiency of EE2 biodegradation was shown to be strongly correlated with electron accepting capacity (EAC) of DOM. Electrochemical modification can increase the EAC of DOM leading to EE2 biodegradation accelerated, and it also can form more triplet-state DOM moieties to promote the EE2 photodegradation in irradiation conditions, due to the increasing of quinone-type structures in DOM. Moreover, cell polymeric secretion (CPS) secreted from the microorganism could be stimulated to an excited state by irradiation, and that also accelerated EE2 degradation. Photolysis combined with biochemical degradation yielded less toxic degradation products. This study shows that the emission of DOM in wastewater after electrochemical treatment could accelerate estrogen degradation and play a positive role on the pollutant transformation in the environment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Effects of quantity, quality, and contact time of dissolved organic matter on bioconcentration of benzo[a]pyrene in the nematode Caenorhabditis elegans

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haitzer, M.; Hoess, S.; Burnison, B.K.

1999-03-01

Quantity and quality of dissolved organic matter (DOM) and the time allowed for DOM to interact with organic contaminants can influence their bioavailability. The authors studied the effect of natural aquatic DOM that had been in contact with benzo[a]pyrene (B[a]P) for 1 to 12 d on the bioconcentration of B[a]P in the nematode Caenorhabditis elegans. Dissolved organic matter quality and quantity was varied by using DOM from three different sources, each in three different concentrations. A model, based on the assumption that only freely dissolved B[a]P is bioavailable, was employed to estimate biologically determined partition coefficients [K{sub p}(biol.)]. Expressing themore » data for each combination of DOM source and contact time in a single K{sub p} (biol.) value allowed a direct comparison of the effects of different DOM qualities and contact times. The results show that the effect of DOM from a specific source was dependent on DOM quantity, but they also observed a distinct effect of DOM quality (represented by different sampling locations) on the bioconcentration of B[a]P. Contact time had no significant influence for the effects of two DOM sources on the bioconcentration of B[a]P. However, the third DOM source was significantly more effective with increased contact time, leading to lower B[a]P bioconcentration in the nematodes.« less

Temporal Dynamics in the Concentration, Flux, and Optical Properties of Tree-derived Dissolved Organic Matter (Tree-DOM) in an Epiphyte-laden Oak-cedar Forest.

NASA Astrophysics Data System (ADS)

Whitetree, A.; Van Stan, J. T., II; Wagner, S.; Guillemette, F.; Lewis, J.; Silva, L.; Stubbins, A.

2017-12-01

Studies on the fate and transport of dissolved organic matter (DOM) along the rainfall-to-discharge flow pathway typically begin in streams or soils, neglecting the initial enrichment of rainfall with DOM during contact with plant canopies. However, rain water can gather significant amounts of tree-derived DOM (tree-DOM) when it drains from the canopy, as throughfall, and down the stem, as stemflow. We examined the temporal variability of event-scale tree-DOM concentrations, yield, and optical (light absorbance and fluorescence) characteristics from an epiphyte-laden Quercus virginiana-Juniperus virginiana forest on Skidaway Island, Savannah, Georgia (USA). All tree-DOM fluxes were highly enriched compared to rainfall and epiphytes further increased concentrations. Stemflow DOC concentrations were greater than throughfall across study species, yet larger throughfall water yields produced greater DOC yields versus stemflow. Tree-DOM optical characteristics indicate it is aromatic-rich with FDOM dominated by humic-like fluorescence, containing 10-20% protein-like (tryptophan-like) fluorescence. Storm size was the only storm condition that strongly correlated with tree-DOM concentration and flux; however, throughfall and stemflow optical characteristics varied little across a wide range of storm conditions (from low magnitude events to intense tropical storms). Annual tree-DOM yields from the study forest (0.8-46 g-C m-2 yr-1) compared well to other yields along the rainfall-to- discharge flow pathway, exceeding DOM yields from some river watersheds.

Origins and bioavailability of dissolved organic matter in groundwater

USGS Publications Warehouse

Shen, Yuan; Chapelle, Francis H.; Strom, Eric W.; Benner, Ronald

2015-01-01

Dissolved organic matter (DOM) in groundwater influences water quality and fuels microbial metabolism, but its origins, bioavailability and chemical composition are poorly understood. The origins and concentrations of dissolved organic carbon (DOC) and bioavailable DOM were monitored during a long-term (2-year) study of groundwater in a fractured-rock aquifer in the Carolina slate belt. Surface precipitation was significantly correlated with groundwater concentrations of DOC, bioavailable DOM and chromophoric DOM, indicating strong hydrological connections between surface and ground waters. The physicochemical and biological processes shaping the concentrations and compositions of DOM during its passage through the soil column to the saturated zone are conceptualized in the regional chromatography model. The model provides a framework for linking hydrology with the processes affecting the transformation, remineralization and microbial production of DOM during passage through the soil column. Lignin-derived phenols were relatively depleted in groundwater DOM indicating substantial removal in the unsaturated zone, and optical properties of chromophoric DOM indicated lower molecular weight DOM in groundwater relative to surface water. The prevalence of glycine, γ-aminobutyric acid, and d-enantiomers of amino acids indicated the DOM was highly diagenetically altered. Bioassay experiments were used to establish DOC-normalized yields of amino acids as molecular indicators of DOM bioavailability in groundwater. A relatively small fraction (8 ± 4 %) of DOC in groundwater was bioavailable. The relatively high yields of specific d-enantiomers of amino acids indicated a substantial fraction (15–34 %) of groundwater DOC was of bacterial origin.

Genomics of a Metamorphic Timing QTL: met1 Maps to a Unique Genomic Position and Regulates Morph and Species-Specific Patterns of Brain Transcription

PubMed Central

Page, Robert B.; Boley, Meredith A.; Kump, David K.; Voss, Stephen R.

2013-01-01

Very little is known about genetic factors that regulate life history transitions during ontogeny. Closely related tiger salamanders (Ambystoma species complex) show extreme variation in metamorphic timing, with some species foregoing metamorphosis altogether, an adaptive trait called paedomorphosis. Previous studies identified a major effect quantitative trait locus (met1) for metamorphic timing and expression of paedomorphosis in hybrid crosses between the biphasic Eastern tiger salamander (Ambystoma tigrinum tigrinum) and the paedomorphic Mexican axolotl (Ambystoma mexicanum). We used existing hybrid mapping panels and a newly created hybrid cross to map the met1 genomic region and determine the effect of met1 on larval growth, metamorphic timing, and gene expression in the brain. We show that met1 maps to the position of a urodele-specific chromosome rearrangement on linkage group 2 that uniquely brought functionally associated genes into linkage. Furthermore, we found that more than 200 genes were differentially expressed during larval development as a function of met1 genotype. This list of differentially expressed genes is enriched for proteins that function in the mitochondria, providing evidence of a link between met1, thyroid hormone signaling, and mitochondrial energetics associated with metamorphosis. Finally, we found that met1 significantly affected metamorphic timing in hybrids, but not early larval growth rate. Collectively, our results show that met1 regulates species and morph-specific patterns of brain transcription and life history variation. PMID:23946331

Extraneous dissolved organic matter enhanced adsorption of dibutyl phthalate in soils: Insights from kinetics and isotherms.

PubMed

Wu, Wei; Sheng, Hongjie; Gu, Chenggang; Song, Yang; Willbold, Sabine; Qiao, Yan; Liu, Guangxia; Zhao, Wei; Wang, Yu; Jiang, Xin; Wang, Fang

2018-08-01

The widespread use of plastic film, especially in agricultural practices, has resulted in phthalic acid esters (PAEs) pollution, which poses risks for greenhouse soils. Application of composted manure is a common agricultural practice that adds extraneous dissolved organic matter (DOM) to the soil, however, the effect of extraneous DOM on the behavior of PAEs in agricultural soil is not clear. Dibutyl phthalate (DBP) was used as a model compound to investigate the effect and mechanism of extraneous DOM on the adsorption kinetics and isotherms of PAEs in two types of soils, through batch experiments and characterization of extraneous DOM and soils using fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). The equilibrium adsorption amount of DBP in black soil was higher than in red soil regardless of the presence of extraneous DOM, due to the higher organic matter content of black soil. Hydrophobic partition played a dominant role in the DBP adsorption process of soils with and without extraneous DOM. The addition of DOM enhanced the adsorption capacity of DBP through partition in the two soils, especially at high DBP concentrations. Additions of a lower concentration of DOM better enhanced the adsorption effect than the higher concentrated DOM, due to an increase in water solubility of DBP resulted from excessive extraneous DOM in aqueous phase. Differences in mineral composition of soils led to diverse adsorption mechanisms of DBP as affected by additions of extraneous DOM. The FTIR spectra indicated that the intra-molecular and intermolecular hydrogen bond interactions of carboxylic acids, aromatic CC and CO in amides were involved in DBP adsorption in soils. Therefore, addition of DOM may increase adsorption of DBP in soils and thus influence its bioavailability and transformation in soils. Copyright © 2018 Elsevier B.V. All rights reserved.

The Effect of Increased Loads of Dissolved Organic Matter on Estuarine Microbial Community Composition and Function

PubMed Central

Traving, Sachia J.; Rowe, Owen; Jakobsen, Nina M.; Sørensen, Helle; Dinasquet, Julie; Stedmon, Colin A.; Andersson, Agneta; Riemann, Lasse

2017-01-01

Increased river loads are projected as one of the major consequences of climate change in the northern hemisphere, leading to elevated inputs of riverine dissolved organic matter (DOM) and inorganic nutrients to coastal ecosystems. The objective of this study was to investigate the effects of elevated DOM on a coastal pelagic food web from the coastal northern Baltic Sea, in a 32-day mesocosm experiment. In particular, the study addresses the response of bacterioplankton to differences in character and composition of supplied DOM. The supplied DOM differed in stoichiometry and quality and had pronounced effects on the recipient bacterioplankton, driving compositional changes in response to DOM type. The shifts in bacterioplankton community composition were especially driven by the proliferation of Bacteroidetes, Gemmatimonadetes, Planctomycetes, and Alpha- and Betaproteobacteria populations. The DOM additions stimulated protease activity and a release of inorganic nutrients, suggesting that DOM was actively processed. However, no difference between DOM types was detected in these functions despite different community compositions. Extensive release of re-mineralized carbon, nitrogen and phosphorus was associated with the bacterial processing, corresponding to 25–85% of the supplied DOM. The DOM additions had a negative effect on phytoplankton with decreased Chl a and biomass, particularly during the first half of the experiment. However, the accumulating nutrients likely stimulated phytoplankton biomass which was observed to increase towards the end of the experiment. This suggests that the nutrient access partially outweighed the negative effect of increased light attenuation by accumulating DOM. Taken together, our experimental data suggest that parts of the future elevated riverine DOM supply to the Baltic Sea will be efficiently mineralized by microbes. This will have consequences for bacterioplankton and phytoplankton community composition and function, and significantly affect nutrient biogeochemistry. PMID:28337180

How reservoirs alter drinking water quality: Organic matter sources, sinks, and transformations

USGS Publications Warehouse

Kraus, Tamara E.C.; Bergamaschi, Brian A.; Hernes, Peter J.; Doctor, Daniel H.; Kendall, Carol; Downing, Bryan D.; Losee, Richard F.

2011-01-01

Within reservoirs, production, transformation, and loss of dissolved organic matter (DOM) occur simultaneously. While the balance between production and loss determines whether a reservoir is a net sink or source of DOM, changes in chemical composition are also important because they affect DOM reactivity with respect to disinfection by-product (DBP) formation. The composition of the DOM pool also provides insight into DOM sources and processing, which can inform reservoir management. We examined the concentration and composition of DOM in San Luis Reservoir, a large off-stream impoundment of the California State Water Project. We used a wide array of DOM chemical tracers including dissolved organic carbon (DOC) concentration, trihalomethane and haloacetic acid formation potentials (THMFP and HAAFP, respectively), absorbance properties, isotopic composition, lignin phenol content, and structural groupings determined by 13C nuclear magnetic resonance (NMR). There were periods when the reservoir was a net source of DOC due to the predominance of algal production (summer), a net sink due to the predominance of degradation (fall–winter), and balanced between production and consumption (spring). Despite only moderate variation in bulk DOC concentration (3.0–3.6 mg C/L), changes in DOM composition indicated that terrestrial-derived material entering the reservoir was being degraded and replaced by aquatic-derived DOM produced within the reservoir. Substantial changes in the propensity of the DOM pool to form THMs and HAAs illustrate that the DBP precursor pool was not directly coupled to bulk DOC concentration and indicate that algal production is an important source of DBP precursors. Results suggest reservoirs have the potential to attenuate DOM amount and reactivity with respect to DBP precursors via degradative processes; however, these benefits can be decreased or even negated by the production of algal-derived DOM.

Human activities cause distinct dissolved organic matter composition across freshwater ecosystems.

PubMed

Williams, Clayton J; Frost, Paul C; Morales-Williams, Ana M; Larson, James H; Richardson, William B; Chiandet, Aisha S; Xenopoulos, Marguerite A

2016-02-01

Dissolved organic matter (DOM) composition in freshwater ecosystems is influenced by the interactions among physical, chemical, and biological processes that are controlled, at one level, by watershed landscape, hydrology, and their connections. Against this environmental template, humans may strongly influence DOM composition. Yet, we lack a comprehensive understanding of DOM composition variation across freshwater ecosystems differentially affected by human activity. Using optical properties, we described DOM variation across five ecosystem groups of the Laurentian Great Lakes region: large lakes, Kawartha Lakes, Experimental Lakes Area, urban stormwater ponds, and rivers (n = 184 sites). We determined how between ecosystem variation in DOM composition related to watershed size, land use and cover, water quality measures (conductivity, dissolved organic carbon (DOC), nutrient concentration, chlorophyll a), and human population density. The five freshwater ecosystem groups had distinctive DOM composition from each other. These significant differences were not explained completely through differences in watershed size nor spatial autocorrelation. Instead, multivariate partial least squares regression showed that DOM composition was related to differences in human impact across freshwater ecosystems. In particular, urban/developed watersheds with higher human population densities had a unique DOM composition with a clear anthropogenic influence that was distinct from DOM composition in natural land cover and/or agricultural watersheds. This nonagricultural, human developed impact on aquatic DOM was most evident through increased levels of a microbial, humic-like parallel factor analysis component (C6). Lotic and lentic ecosystems with low human population densities had DOM compositions more typical of clear water to humic-rich freshwater ecosystems but C6 was only present at trace to background levels. Consequently, humans are strongly altering the quality of DOM in waters nearby or flowing through highly populated areas, which may alter carbon cycles in anthropogenically disturbed ecosystems at broad scales. © 2015 John Wiley & Sons Ltd.

Human activities cause distinct dissolved organic matter composition across freshwater ecosystems

USGS Publications Warehouse

Williams, Clayton J.; Frost, Paul C.; Morales-Williams, Ana M.; Larson, James H.; Richardson, William B.; Chiandet, Aisha S.; Xenopoulos, Marguerite A.

2016-01-01

Dissolved organic matter (DOM) composition in freshwater ecosystems is influenced by interactions between physical, chemical, and biological processes that are controlled, at one level, by watershed landscape, hydrology, and their connections. Against this environmental template, humans may strongly influence DOM composition. Yet, we lack a comprehensive understanding of DOM composition variation across freshwater ecosystems differentially affected by human activity. Using optical properties, we described DOM variation across five ecosystem groups of the Laurentian Great Lakes Region: large lakes, Kawartha Lakes, Experimental Lakes Area, urban stormwater ponds, and rivers (n = 184 sites). We determined how between ecosystem variation in DOM composition related to watershed size, land use and cover, water quality measures (conductivity, dissolved organic carbon (DOC), nutrient concentration, chlorophyll a), and human population density. The five freshwater ecosystem groups had distinctive DOM composition from each other. These significant differences were not explained completely through differences in watershed size nor spatial autocorrelation. Instead, multivariate partial least squares regression showed that DOM composition was related to differences in human impact across freshwater ecosystems. In particular, urban/developed watersheds with higher human population densities had a unique DOM composition with a clear anthropogenic influence that was distinct from DOM composition in natural land cover and/or agricultural watersheds. This nonagricultural, human developed impact on aquatic DOM was most evident through increased levels of a microbial, humic-like parallel factor analysis component (C6). Lotic and lentic ecosystems with low human population densities had DOM compositions more typical of clear water to humic-rich freshwater ecosystems but C6 was only present at trace to background levels. Consequently, humans are strongly altering the quality of DOM in waters nearby or flowing through highly populated areas, which may alter carbon cycles in anthropogenically disturbed ecosystems at broad scales.

Photodegradation of dissolved organic matter in ice under solar irradiation.

PubMed

Xue, Shuang; Wang, Chao; Zhang, Zhaohong; Song, Youtao; Liu, Qiang

2016-02-01

The photodegradation behavior of dissolved organic matter (DOM) with different origins in ice under solar irradiation was investigated. Exposure to sunlight at 2.7 × 10(5) J m(-2) resulted in dissolved organic carbon (DOC) reductions of 22.1-36.5% in ice. The naturally occurring DOM had higher photodegradation potentials than the wastewater-derived DOM in ice. Ultraviolet (UV)-absorbing compounds in DOM, regardless of DOM origin, had much higher photodegradation potentials than gross DOC in ice. The susceptibility of UV-absorbing compounds with natural origin to sunlight exposure in ice was higher than those derived from wastewater. Trihalomethane (THM) precursors were more susceptible to photochemical reactions than gross DOC and haloacetic acid (HAA) precursors in ice. THM precursors in naturally occurring DOM were more photoreactive than those in wastewater-derived DOM in ice, while the photoreactivity of HAA precursors in ice was independent of DOM origin. In ice, the photoreactivity of humic-like fluorescent materials, regardless of DOM origin, was higher than that of gross DOC and protein-like fluorescent materials. DOC reductions caused by sunlight irradiation were found to be negatively correlated to DOC levels, and positively correlated to the aromaticity of DOM. The photodegradation of both wastewater-derived and naturally occurring DOM in ice was significantly facilitated at both acid and alkaline pH, as compared to neutral pH. The photodegradation of DOM in ice, regardless of the origin, was facilitated by nitrate ion [Formula: see text] , nitrite ion [Formula: see text] , ferric ion (Fe(3+)) and ferrous ion (Fe(2+)), and on the other hand, was inhibited by chloridion ion (Cl(-)) and copper ion (Cu(2+)). Copyright © 2015 Elsevier Ltd. All rights reserved.

The effect of probe choice and solution conditions on the apparent photoreactivity of dissolved organic matter.

PubMed

Maizel, Andrew C; Remucal, Christina K

2017-08-16

Excited triplet states of dissolved organic matter ( 3 DOM) are quantified directly with the species-specific probes trans,trans-hexadienoic acid (HDA) and 2,4,6-trimethylphenol (TMP), and indirectly with the singlet oxygen ( 1 O 2 ) probe furfuryl alcohol (FFA). Although previous work suggests that these probe compounds may be sensitive to solution conditions, including dissolved organic carbon concentration ([DOC]) and pH, and may quantify different 3 DOM subpopulations, the probes have not been systematically compared. Therefore, we quantify the apparent photoreactivity of diverse environmental waters using HDA, TMP, and FFA. By conducting experiments under ambient [DOC] and pH, with standardized [DOC] and pH, and with solid phase extraction isolates, we demonstrate that much of the apparent dissimilarity in photochemical measurements is attributable to solution conditions, rather than intrinsic differences in 3 DOM production. In general, apparent quantum yields (Φ 1 O 2 ≥ Φ 3 DOM,TMP ≫ Φ 3 DOM,HDA ) and pseudo-steady state concentrations ([ 1 O 2 ] ss > [ 3 DOM] ss,TMP > [ 3 DOM] ss,HDA ) show consistent relationships in all waters under standardized conditions. However, intrinsic differences in 3 DOM photoreactivity are apparent between DOM from diverse sources, as seen in the higher Φ 1 O 2 and lower Φ 3 DOM,TMP of wastewater effluents compared with oligotrophic lakes. Additionally, while conflicting trends in photoreactivity are observed under ambient conditions, all probes observe quantum yields increasing from surface wetlands to terrestrially influenced waters to oligotrophic lakes under standardized conditions. This work elucidates how probe selection and solution conditions influence the apparent photoreactivity of environmental waters and confirms that 3 DOM or 1 O 2 probes cannot be used interchangeably in waters that vary in [DOC], pH, or DOM source.

Biochar amendment to soil changes dissolved organic matter content and composition.

PubMed

Smebye, Andreas; Alling, Vanja; Vogt, Rolf D; Gadmar, Tone C; Mulder, Jan; Cornelissen, Gerard; Hale, Sarah E

2016-01-01

Amendments of biochar, a product of pyrolysis of biomass, have been shown to increase fertility of acidic soils by enhancing soil properties such as pH, cation-exchange-capacity and water-holding-capacity. These parameters are important in the context of natural organic matter contained in soils, of which dissolved organic matter (DOM) is the mobile and most bioavailable fraction. The effect of biochar on the content and composition of DOM in soils has received little research attention. This study focuses on the effects of amendments of two different biochars to an acidic acrisol and a pH-neutral brown soil. A batch experiment showed that mixing biochar with the acrisols at a 10 wt.% dose increased the pH from 4.9 to 8.7, and this resulted in a 15-fold increase in the dissolved organic carbon concentration (from 4.5 to 69 mg L(-1)). The pH-increase followed the same trend as the release of DOM in the experiment, causing higher DOM solubility and desorption of DOM from mineral sites. The binding to biochar of several well-characterised reference DOM materials was also investigated and results showed a higher sorption of aliphatic DOM to biochar than aromatic DOM, with DOM-water partitioning coefficients (Kd-values) ranging from 0.2 to 590 L kg(-1). A size exclusion occurring in biochar's micropores, could result in a higher sorption of smaller aliphatic DOM molecules than larger aromatic ones. These findings indicate that biochar could increase the leaching of DOM from soil, as well as change the DOM composition towards molecules with a larger size and higher aromaticity. Copyright © 2015 Elsevier Ltd. All rights reserved.

The effect of dissolved organic matter (DOM) on sodium transport and nitrogenous waste excretion of the freshwater cladoceran (Daphnia magna) at circumneutral and low pH.

PubMed

Al-Reasi, Hassan A; Yusuf, Usman; Smith, D Scott; Wood, Chris M

2013-11-01

Dissolved organic matter (DOM), a heterogeneous substance found in all natural waters, has many documented abiotic roles, but recently, several possible direct influences of DOM on organism physiology have been reported. However, most studies have been carried out with a limited number of natural DOM isolates or were restricted to the use of commercial or artificial humic substances. We therefore employed three previously characterized, chemically-distinct natural DOMs, as well as a commercially available humic acid (Aldrich, AHA), at circumneutral (7-8) and acidic pH (~5), to examine DOM effects on whole-body Na(+) concentration, unidirectional influx and efflux rates of Na(+), and ammonia and urea excretion rates in Daphnia magna. Whole-body Na(+) concentration, Na(+) influx, and Na(+) efflux rates were all unaffected regardless of pH, suggesting no influence of the various natural DOMs on active uptake and passive diffusion of Na(+) in this organism. Ammonia and urea excretion rates were both increased by low pH. Ammonia excretion rates were reduced at circumneutral pH by the most highly colored, allochthonous DOM, and at low pH by all three natural DOMs, as well as by the commercial AHA. Urea excretion rates were not influenced by the presence of the various DOMs in circumneutral solutions, but were attenuated by the presence of two allochthonous DOM sources (isolated from Bannister Lake and Luther Marsh) at acidic pH. The observed reductions may be attributed partially to the higher buffering capacities of natural DOM sources, as well as their ability to interact with biological membranes as estimated by a new measure calculated from their acid-base titration characteristics, the Proton Binding Index (PBI). © 2013.

Chronology of paleozoic metamorphism and deformation in the Blue Ridge thrust complex, North Carolina and Tennessee

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goldberg, S.A.; Dallmeyer, R.D.

1997-05-01

The Blue Ridge province in northwestern North Carolina and northeastern Tennessee records a multiphase collisional and accretionary history from the Mesoproterozoic through the Paleozoic. To constrain the tectonothermal evolution in this region, radiometric ages have been determined for 23 regionally metamorphosed amphibolites, granitic gneisses, and pelitic schists and from mylonites along shear zones that bound thrust sheets and within an internal shear zone. The garnet ages from the Pumpkin Patch a thrust sheet (458, 455, and 451 Ma) are similar to those from the structurally overlying Spruce Pine thrust sheet (460, 456, 455, and 450 Ma). Both thrust sheets exhibitmore » similar upper amphibolite-facies conditions. Because of the high closure temperature for garnet, the garnet ages are interpreted to date growth at or near the peak of Taconic metamorphism. Devonian metamorphic ages are recognized in the Spruce Pine thrust sheet, where Sm-Nd and Rb-Sr garnet ages of 386 and 393 Ma and mineral isochron ages of 397 {+-} 14 and 375 {+-} 27 Ma are preserved. Hornblendes record similar {sup 40}Ar/{sup 39}Ar, Sm-Nd, and Rb-Sr ages of 398 to 379 Ma. Devonian {sup 40}Ar/{sup 39}Ar hornblende ages are also recorded in the structurally lower Pumpkin Patch thrust sheet. The Devonian mineral ages are interpreted to date a discrete tectonothermal event, as opposed to uplift and slow cooling from an Ordovician metamorphic event. The Mississippian mylonitization is interpreted to represent thrusting and initial assembly of crystalline sheets associated with the Alleghanian orogeny. The composite thrust stack of the Blue Ridge complex was subsequently thrust northwestward along the Linville Falls fault during middle Alleghanian orogeny (about 300 Ma).« less

Dynamics of Metamorphic Core Complexes Inferred From Modeling and Metamorphic Petrology

NASA Astrophysics Data System (ADS)

Whitney, D. L.; Rey, P.; Teyssier, C.

2008-12-01

Orogenic collapse involves extension and thinning of thick, hot, and in some cases partially molten, crust, leading to the formation of metamorphic core complexes (MCC) that are commonly cored by migmatite domes. 2D numerical modeling predicts that the geometry and P-T-t history of MCC varies as a function of the presence/absence of a partially molten layer in the deep crust; the nature of heterogeneities that localize the MCC (e.g. normal fault in upper crust vs. point-like anomaly in the deep crust); and extensional strain rate. The presence of melt in particular has a significant effect on the thermal and structural history of MCC because the presence of partially molten crust or magma bodies at depth enhances upward advection of material and heat. At high extension rate (cm/year in the region of the MCC), partially molten crust crystallizes as migmatite and cools along a high geothermal gradient (35-65 C/km); material remains partially molten during ascent, forming a migmatite dome when it crystallizes at shallower crustal levels (e.g. cordierite/sillimanite stability field). At low strain rate (mm/yr in the MCC region), the partially molten crust crystallizes at high pressure (e.g. kyanite zone); this material is subsequently deformed in the solid-state along a cooler geothermal gradient (20-35 C/km) during ascent. MCC that develop during extension of partially molten crust may therefore record distinct crystallization versus exhumation histories as a function of extensional strain rate. The mineral assemblages, metamorphic reaction histories, and structures of migmatite-cored (Mc) MCC can therefore be used to interpret the dynamics of MCC formation, e.g. "fast" McMCC in the northern N American Cordillera and Aegean regions.

­Oligo-Miocene Monazite Ages in the Lesser Himalaya Sequence, Arunachal Pradesh, India; Geological Content of Age Variations

NASA Astrophysics Data System (ADS)

Clarke, G. L.; Bhowmik, S. K.; Ireland, T. R.; Aitchison, J. C.; Chapman, S. L.; Kent, L.

2016-12-01

A telescoped and inverted greenschist-upper amphibolite facies sequence in the in the Siyom Valley of eastern Arunachal Pradesh is tectonically overlain by an upright (grade decreasing upward) granulite to lower amphibolite facies sequence. Such grade relationships would normally attribute the boundary to a Main Central Thrust (MCT) structure, and predict a change from underlying Lesser Himalaya Sequence (LHS) to Greater Himalaya Sequence rocks across the boundary. However, all pelitic and psammitic samples have similar detrital zircon age spectra, involving c. 2500, 1750-1500, 1200 and 1000 Ma Gondwanan populations correlated with the LHS. Isograds are broadly parallel to a penetrative NW-dipping S2 foliation, developed contemporaneously with the inversion. Garnet growth in garnet, staurolite and kyanite zone schists beneath the thrust commenced at P>8 kbar and T≈550°C, before syn- to post-S2 heating of staurolite and kyanite zone rocks to T≈640°C at P≈8.5 kbar, most probably at c. 18.5 Ma. Kyanite-rutile-garnet migmatite immediately above the thrust records peak conditions of P≈10 kbar and T≈750°C and c. 21.5 Ma monazite ages. Complexity in c. 21-1000 Ma monazite ages in overlying amphibolite facies schists reflects the patchy recrystallization of detrital grains, intra-grain complexity being dependent on whole rock composition, metamorphic grade and evolition. Slip on a SE-propagating thrust was likely contemporaneous with early Miocene metamorphism, based on the distribution of structure, metamorphic textures, and overlap of age relationships. It is inferred to have initially controlled the uplift of granulite to mid-crustal levels between 22 and 19 Ma, thermal relaxation within a disrupted LHS metamorphic profile inducing a post-S2 thermal peak in lower grade footwall rocks.

Composition, dynamics, and fate of leached dissolved organic matter in terrestrial ecosystems: Results from a decomposition experiment

USGS Publications Warehouse

Cleveland, C.C.; Neff, J.C.; Townsend, A.R.; Hood, E.

2004-01-01

Fluxes of dissolved organic matter (DOM) are an important vector for the movement of carbon (C) and nutrients both within and between ecosystems. However, although DOM fluxes from throughfall and through litterfall can be large, little is known about the fate of DOM leached from plant canopies, or from the litter layer into the soil horizon. In this study, our objectives were to determine the importance of plant-litter leachate as a vehicle for DOM movement, and to track DOM decomposition [including dissolve organic carbon (DOC) and dissolved organic nitrogen (DON) fractions], as well as DOM chemical and isotopic dynamics, during a long-term laboratory incubation experiment using fresh leaves and litter from several ecosystem types. The water-extractable fraction of organic C was high for all five plant species, as was the biodegradable fraction; in most cases, more than 70% of the initial DOM was decomposed in the first 10 days of the experiment. The chemical composition of the DOM changed as decomposition proceeded, with humic (hydrophobic) fractions becoming relatively more abundant than nonhumic (hydrophilic) fractions over time. However, in spite of proportional changes in humic and nonhumic fractions over time, our data suggest that both fractions are readily decomposed in the absence of physicochemical reactions with soil surfaces. Our data also showed no changes in the ??13C signature of DOM during decomposition, suggesting that isotopic fractionation during DOM uptake is not a significant process. These results suggest that soil microorganisms preferentially decompose more labile organic molecules in the DOM pool, which also tend to be isotopically heavier than more recalcitrant DOM fractions. We believe that the interaction between DOM decomposition dynamics and soil sorption processes contribute to the ??13C enrichment of soil organic matter commonly observed with depth in soil profiles.

Composition and transformation of dissolved organic matter in the Baltic Sea

NASA Astrophysics Data System (ADS)

Seidel, Michael; Manecki, Marcus; Herlemann, Daniel P. R.; Deutsch, Barbara; Schulz-Bull, Detlef; Jürgens, Klaus; Dittmar, Thorsten

2017-05-01

The processing of terrestrial dissolved organic matter (DOM) in coastal shelf seas is an important part of the global carbon cycle, yet, it is still not well understood. One of the largest brackish shelf seas, the Baltic Sea in northern Europe, is characterized by high freshwater input from sub-arctic rivers and limited water exchange with the Atlantic Ocean via the North Sea. We studied the molecular and isotopic composition and turnover of solid-phase extractable (SPE) DOM and its transformation along the salinity and redox continuum of the Baltic Sea during spring and autumn. We applied ultrahigh-resolution mass spectrometry and other geochemical and biological approaches. Our data demonstrate a large influx of terrestrial riverine DOM, especially into the northern part of the Baltic Sea. The DOM composition in the central Baltic Sea changed seasonally and was mainly related to autochthonous production by phytoplankton in spring. Especially in the northern, river-dominated basins, a major fraction of riverine DOM was removed, likely by bio- and photo-degradation. We estimate that the removal rate of terrestrial DOM in the Baltic Sea (Bothnian Bay to the Danish Straits/Kattegat area) is 1.6 - 1.9 Tg C per year which is 43 to 51% of the total riverine input. The export of terrestrial DOM from the Danish Straits/Kattegat area towards the North Sea is 1.8 - 2.1 Tg C per year. Due to the long residence time of terrestrial DOM in the Baltic Sea (total of ca. 12 years), seasonal variations caused by bio- and photo-transformations and riverine discharge are dampened, resulting in a relatively invariant DOM molecular and isotopic signature exported to the North Sea. In the deep stagnant basins of the Baltic Sea, the DOM composition and dissolved organic nitrogen concentrations changed seasonally, likely because of vertical particle transport and subsequent degradation releasing DOM. DOM in the deep anoxic basins was also enriched in sulfur-containing organic molecules, pointing to abiotic sulfurization of DOM under sulfidic conditions.

SHRIMP study of zircons from Early Archean rocks in the Minnesota River Valley: Implications for the tectonic history of the Superior Province

USGS Publications Warehouse

Bickford, M.E.; Wooden, J.L.; Bauer, R.L.

2006-01-01

Interest in Paleoarchean to early Mesoarchean crust in North America has been sparked by the recent identification of ca. 3800-3500 Ma rocks on the northern margin of the Superior craton in the Assean Lake region of northern Manitoba and the Porpoise Cove terrane in northern Quebec. It has long been known that similarly ancient gneisses are exposed on the southern margin of the Superior craton in the Minnesota River Valley and in northern Michigan, but the ages of these rocks have been poorly constrained, because methods applied in the 1960s through late 1970s were inadequate to unravel the complexities of their thermotectonic history. Rocks exposed in the Minnesota River Valley include a complex of migmatitic granitic gneisses, schistose to gneissic amphibolite, metagabbro, and paragneisses. The best-known units are the Morton Gneiss and the Montevideo Gneiss. The complex of ancient gneisses is intruded by a major younger, weakly deformed granite body, the Sacred Heart granite. Regional geophysical anomalies that extend across the Minnesota River Valley have been interpreted as defining boundaries between distinct blocks containing the various gneissic units. New sensitive high-resolution ion microprobe (SHRIMP) U-Pb data from complex zircons yielded the following ages: Montevideo Gneiss near Montevideo, 3485 ?? 10 Ma, granodiorite intrusion, 3385 ?? 8 Ma; Montevideo Gneiss at Granite Falls, 3497 ?? 9 Ma, metamorphic event, 3300-3350 Ma, mafic intrusion, 3141 ?? 2 Ma, metamorphic overprint (rims), 2606 ?? 4 Ma; Morton Gneiss: 3524 ?? 9 Ma, granodiorite intrusion, 3370 ?? 8 Ma, metamorphic overprints (growth of rims), 3140 ?? 2 Ma and 2595 ?? 4 Ma; biotite-garnet paragneiss, 2619 ?? 20 Ma; and Sacred Heart granite, 2604 ?? 4 Ma. Zircons from a cordierite-bearing feldspar-biotite schist overlying the Morton Gneiss yielded well-defined age peaks at 3520, 3480, 3380, and 3140 Ma, showing detrital input from most of the older rock units; 2600 Ma rims on these zircons indicate metamorphism at this time. Zircons from a hypersthene-bearing biotite-garnet paragneiss, overlying the Montevideo Gneiss near Granite Falls, yielded ca. 2600 Ma ages, indicating zircon growth during high-grade metamorphism at this time. Despite some differences in the intensity of the 2600 Ma event between the Morton and Montevideo blocks, both blocks display similar thermochronologic relationships and ages, suggesting that their boundary is not a fundamental suture between two distinct Paleoarchean terranes. Previously obtained zircon age data from the tonalitic gneiss at Watersmeet Dome in northern Michigan indicated formation at ca. 3500 Ma, whereas a granite body near Thayer was dated at 2745 ?? 65 Ma and leucogranite dikes are ca. 2600 Ma. Thus, these rocks and those in the Minnesota River Valley were formed in the late Paleoarchean and show a history of igneous activity and metamorphism in the Mesoarchean and Neoarchean. The occurrence of ancient crustal rocks on both the northern and southern margins of the ca. 2900-2700 Superior craton suggests that they are remnants of once more-extensive Paleoarchean crust that existed prior to formation of the Neoarchean Superior craton. ?? 2006 Geological Society of America.

Phototransformation of pesticides in prairie potholes: effect of dissolved organic matter in triplet-induced oxidation.

PubMed

Karpuzcu, M Ekrem; McCabe, Andrew J; Arnold, William A

2016-02-01

Photochemical reactions involving a variety of photosensitizers contribute to the abiotic transformation of pesticides in prairie pothole lakes (PPLs). Despite the fact that triplet excited state dissolved organic matter (DOM) enhances phototransformation of pesticides by acting as a photosensitizer, it may also decrease the overall phototransformation rate through various mechanisms. In this study, the effect of DOM on the phototransformation of four commonly applied pesticides in four different PPL waters was investigated under simulated sunlight using photoexcited benzophenone-4-carboxylate as the oxidant with DOM serving as an anti-oxidant. For atrazine and mesotrione, a decrease in phototransformation rates was observed, while phototransformations of metolachlor and isoproturon were not affected by DOM inhibition. Phototransformation rates and the extent of inhibition/enhancement by DOM varied spatially and temporally across the wetlands studied. Characterization of DOM from the sites and different seasons suggested that the DOM type and variations in the DOM structure are important factors controlling phototransformation rates of pesticides in PPLs.

Formation of nanocolloidal metacinnabar in mercury-DOM-sulfide systems

USGS Publications Warehouse

Gerbig, Chase A.; Kim, Christopher S.; Stegemeier, John P.; Ryan, Joseph N.; Aiken, George R.

2011-01-01

Direct determination of mercury (Hg) speciation in sulfide-containing environments is confounded by low mercury concentrations and poor analytical sensitivity. Here we report the results of experiments designed to assess mercury speciation at environmentally relevant ratios of mercury to dissolved organic matter (DOM) (i.e., <4 nmol Hg (mg DOM)−1) by combining solid phase extraction using C18 resin with extended X-ray absorption fine structure (EXAFS) spectroscopy. Aqueous Hg(II) and a DOM isolate were equilibrated in the presence and absence of 100 μM total sulfide. In the absence of sulfide, mercury adsorption to the resin increased as the Hg:DOM ratio decreased and as the strength of Hg-DOM binding increased. EXAFS analysis indicated that in the absence of sulfide, mercury bonds with an average of 2.4 ± 0.2 sulfur atoms with a bond length typical of mercury-organic thiol ligands (2.35 Å). In the presence of sulfide, mercury showed greater affinity for the C18 resin, and its chromatographic behavior was independent of Hg:DOM ratio. EXAFS analysis showed mercury–sulfur bonds with a longer interatomic distance (2.51–2.53 Å) similar to the mercury–sulfur bond distance in metacinnabar (2.53 Å) regardless of the Hg:DOM ratio. For all samples containing sulfide, the sulfur coordination number was below the ideal four-coordinate structure of metacinnabar. At a low Hg:DOM ratio where strong binding DOM sites may control mercury speciation (1.9 nmol mg–1) mercury was coordinated by 2.3 ± 0.2 sulfur atoms, and the coordination number rose with increasing Hg:DOM ratio. The less-than-ideal coordination numbers indicate metacinnabar-like species on the nanometer scale, and the positive correlation between Hg:DOM ratio and sulfur coordination number suggests progressively increasing particle size or crystalline order with increasing abundance of mercury with respect to DOM. In DOM-containing sulfidic systems nanocolloidal metacinnabar-like species may form, and these species need to be considered when addressing mercury biogeochemistry.

Transformations of DOM in forested catchments: the pathways of DOM from litter and soil to river export

NASA Astrophysics Data System (ADS)

Lajtha, K.; Yano, Y.; Crow, S.; Kaushal, S.

2006-12-01

Although the quality and quantity of DOM ultimately derives from plant detritus and soils in watersheds, three is substantial alteration of DOM as it passes from litter through the terrestrial landscape. As DOM is generated from plant and microbial detritus and processing, different fractions may be lost via respiration, form quasi-stable soil organic matter, or be temporarily sorbed to soil minerals. We followed the fate of DOC and DON from forested plots with experimentally altered detritus loads to determine the relative roles of original plant litter chemistry and soil transformations. Our study site was the DIRT (Detrital Input and Removal Treatment) plots at the H.J. Andrews Experimental Forest in Oregon, where treatments include detrital additions (wood vs. needle litter), litter exclusion, and root exclusions. Fractionation of detritus leachate solutions demonstrated significant differences in DOC chemistry from different detrital sources. Root leachates produced high quantities of hydrophilic neutral DOC, a fraction rich in labile sugars and polysaccharides; young wood extracts produced higher quantities of weak hydrophobic acids and hydrophobic neutrals (longer chain hydrocarbons); older wood had lower quantities of most labile constituents but was rich in strong hydrophobic acids. Although laboratory extracts of different litter types showed differences in DOM chemistry, soil solutions collected just below the forest floor from the differing detrital treatments were remarkably uniform and poor in labile constituents, suggesting microbial equalization of DOM leachate in the field. DOM quality and concentrations changed significantly with passage through soil profiles. DOC concentrations decreased through the soil profile in all plots to a greater degree than did dissolved organic nitrogen (DON), most likely due to preferential sorption of high C:N hydrophobic dissolved organic matter (DOM) in upper horizons. Percent hydrophobic DOM decreased significantly with depth, and the remaining hydrophilic DOM had a much lower and narrower C:N ratio than hydrophobic DOM. We also hypothesize that protein-reactive polyphenols, or tannins, may contribute to the decreased lability of N-rich DOM in soil solutions and thus significantly influence the quality of DOM delivered to streams.

XML schemas for common bioinformatic data types and their application in workflow systems.

PubMed

Seibel, Philipp N; Krüger, Jan; Hartmeier, Sven; Schwarzer, Knut; Löwenthal, Kai; Mersch, Henning; Dandekar, Thomas; Giegerich, Robert

2006-11-06

Today, there is a growing need in bioinformatics to combine available software tools into chains, thus building complex applications from existing single-task tools. To create such workflows, the tools involved have to be able to work with each other's data--therefore, a common set of well-defined data formats is needed. Unfortunately, current bioinformatic tools use a great variety of heterogeneous formats. Acknowledging the need for common formats, the Helmholtz Open BioInformatics Technology network (HOBIT) identified several basic data types used in bioinformatics and developed appropriate format descriptions, formally defined by XML schemas, and incorporated them in a Java library (BioDOM). These schemas currently cover sequence, sequence alignment, RNA secondary structure and RNA secondary structure alignment formats in a form that is independent of any specific program, thus enabling seamless interoperation of different tools. All XML formats are available at http://bioschemas.sourceforge.net, the BioDOM library can be obtained at http://biodom.sourceforge.net. The HOBIT XML schemas and the BioDOM library simplify adding XML support to newly created and existing bioinformatic tools, enabling these tools to interoperate seamlessly in workflow scenarios.

The role of reactive oxygen species in the degradation of lignin derived dissolved organic matter

NASA Astrophysics Data System (ADS)

Waggoner, Derek C.; Wozniak, Andrew S.; Cory, Rose M.; Hatcher, Patrick G.

2017-07-01

Evidence suggests that reactive oxygen species (ROS) are important in transforming the chemical composition of the large pool of terrestrially-derived dissolved organic matter (DOM) exported from land to water annually. However, due to the challenges inherent in isolating the effects of individual ROS on DOM composition, the role of ROS in the photochemical alteration of DOM remains poorly characterized. In this work, terrestrial DOM was independently exposed to singlet oxygen (1O2), and superoxide (O2-rad under controlled laboratory conditions). Using ultra-high resolution mass spectrometry to track molecular level alterations of DOM by ROS, these findings suggest exposure to 1O2 (generated using Rose Bengal and visible light) removed formulas with an O/C > 0.3, and primarily resulted in DOM comprised of formulas with higher oxygen content, while O2-rad exposure (from KO2 in DMSO) removed formulas with O/C < 0.3 and produced aliphatic formulas (H/C > 1.5). Comparison of DOM altered by ROS in this study to riverine and coastal DOM showed that (20-80%) overlap in formulas, providing evidence for the role of ROS in shaping the composition of DOM exported from rivers to oceans.

The effect of source material in determining the photoreactivity of DOM in peatland aquatic systems

NASA Astrophysics Data System (ADS)

Pickard, Amy; Heal, Kate; McLeod, Andy; Dinsmore, Kerry

2016-04-01

Aquatic systems draining peatlands receive a high loading of dissolved organic matter (DOM) from surrounding terrestrial environments. However the fate of aquatic DOM remains poorly constrained, in part due to lack of knowledge regarding the photoreactivity of DOM and how this changes as a function of variability in source material. In this study water samples were collected monthly for a 13-month period from two contrasting aquatic systems in Scotland: a stream draining a peatland with high DOM concentrations (33.3 ± 14.2 mg DOC L-1) and a reservoir draining a peat catchment with low DOM concentrations (4.16 ± 0.91 mg DOC L-1). Controlled UV irradiation laboratory experiments were conducted on samples filtered to 0.2 μm in order to assess the photoreactivity of the DOM, measured as the unit mass of DOC lost upon irradiation. Experiments took place over 8h in temperature controlled conditions, with unirradiated samples used as controls. After exposure, a range of analytical techniques were used to characterise the DOM to yield information about its source material and to determine how this was related to the observed photoreactivity. Lignin phenol analyses indicate considerable contribution of Sphagnum to DOM at the stream site, particularly during summer, as demonstrated by high P-hydroxy/Vanillyl phenol ratios (P/V). Low P/V ratios were correlated with increased photoreactivity, (Pearson's: -0.410; p = 0.15, n = 13), suggesting that DOM from woody lignin sources within the catchment was more photolabile. Photoreactivity was also negatively correlated with Fluorescence Index (FI) values (Pearson's: -0.555; p = 0.055, n = 13), where low FI values are understood to indicate greater contribution of terrestrially derived material to aquatic DOM. Excitation-emission matrices (EEMs) indicate that DOM at the stream site was primarily comprised of a humic-like peak (Ex/Em = 340, 380/460 nm). However, there was also contribution from a protein-like peak (Ex/Em = 290, 320/350 nm), which was present in samples with lower photoreactivity. DOM at the reservoir site was primarily composed of the same identified protein-like peak, which may account for the lower observed photoreactivity of these samples. Although total DOC concentration is the dominant control on photo-induced DOC losses in peatland aquatic systems, these results show that organic matter characterisation can be used to further comprehend changes to DOM photoreactivity. Increased understanding of DOM processing in aquatic freshwater systems will allow the fate of DOM to be more accurately determined.

Investigating the effect of hardness cations on coagulation: The aspect of neutralisation through Al(III)-dissolved organic matter (DOM) binding.

PubMed

Zhou, Yuxuan; Yan, Mingquan; Liu, Ruiping; Wang, Dongsheng; Qu, Jiuhui

2017-05-15

Hardness cations are ubiquitous and abundant in source water, while the effect of hardness on the performance of coagulation for dissolved organic matter (DOM) removal in water treatment remains unclear due to the limitation of methods that can characterise the subtle interactions between DOM, coagulant and hardness cations. This work quantified the competition between coagulant Al 3+ and hardness cations to bind onto DOM using absorbance spectroscopy acquired at different Al 3+ concentrations in the absence and presence of Ca 2+ or Mg 2+ . The results indicate that, in the presence of either Mg 2+ or Ca 2+ , an increasing depression of the binding of Al 3+ -DOM could be observed in the differential spectra of DOM with the increasing of Mg 2+ or Ca 2+ at a level of 10, 100 and 1000 μM, with the observation being more significant at higher pH from 6.5 to 8.5. The results of zeta potentials of DOM indicate that the competition of hardness cations results in the negative DOM being less efficiently neutralised by Al 3+ . This study demonstrates that the removal of DOM by coagulation would significantly deteriorate with the presence of hardness cations, which would compete with coagulant Al 3+ to neutralise the unsaturated sites in DOM. Copyright © 2017 Elsevier Ltd. All rights reserved.

Presentations - Emond, A.M. and others, 2015 | Alaska Division of

Science.gov Websites

: Download below or please see our publication sales page for more information. Quadrangle(s): Big Delta Creek Schist; Bush Prospect; Chicken Metamorphic Complex; Chicken Pluton; DIGHEM-V EM System; Delta

Tectono-metamorphic evolution and magmatic processes in the thermo-metamorphic aureole of the Monte Capanne pluton (Elba Island, Northern Tyrrhenian Sea, Italy).

NASA Astrophysics Data System (ADS)

Morelli, M.; Pandeli, E.; Principi, G.

2003-04-01

Introduction In this work we present new structural and petrographic data collected in the thermo-metamorphic aureole of Monte Capanne (western Elba Island) and its metamorphic evolution. In the western Elba Island the Monte Capanne monzogranitic body (ca. 7 Ma) and its thermo-metamorphic aureole crop out. At least two different tectonic units can be distinguished: the Punta Le Tombe Unit, weak re-crystallized, and the Punta Nera Unit. In the latter one the re-crystallization is strong and a pre-intrusion tectono-metamorphic framework is evident (Morelli et al., 2002). The latter is mainly constituted by thermo-metamorphosed meta-ophiolites and meta-sedimentary successions previously correlated by Barberi et al. (1969) with the un-metamorphic ones (Complex IV and V of Trevisan, 1950) cropping out in the central-eastern Elba. According to Perrin (1975) and Reutter &Spohn (1982) a pre-intrusion tectono-metamorphic framework was recognized into such rocks. As suggested by Daniel &Jolivet (1995) complex relationships between metamorphic evolution and magmatic events are also recognizable. Geological Data The Punta Nera Unit crops out all around the Monte Capanne magmatic body and the primary contact with the underlying granitoid is somewhere preserved. This unit, strongly re-crystallized and locally crosscut by aplitic and porphyritic dikes, is represented by (Coli &Pandeli, 1997; Morelli, 2000) tectonized meta-serpentinites, meta-gabbros with rodingitic dikes, rare meta-basalts and meta-ophicalcites, meta-cherts, marbles, cherty meta-limestones, phyllites and meta-limestones with rare meta-arenites intercalations. A "pre-magmatic" tectono-metamorphic framework of this unit is well evident only in its meta-sedimentary portion. The meta-sediments are deformed by syn-metamorphic isoclinal folds caractherized by N-S trending axes, west dipping axial planes and easternward vergence. A later folding and flattening event clearly post-dated the above said folds and associated main foliation. Both at the meso- and micro-scale few generations of syn-/inter-kinematic and static thermo-metamorphic blasteses (e.g. biotite, wollastonite, garnet, epidote etc.) are evident. Finally weak local folding and faulting affected the Monte Capanne thermo-metamorphic aureole during the uplift of the cooled pluton. Along the coast of Spartaia (north-eastern side of Monte Capanne) the meta-sedimentary upper portion of the Punta Nera Unit crops out and it is represented by alternating marbles and phyllites with rare meta-arenites. Here, the relationships between tectono-metamorphic and thermo-metamorphic structures, and intrusive magmatic bodies are particularly evident. D_1M_1: is recognizable at the meso-scale only as rare relics of intrafolial isoclinal rootless hinges and locally as a transposed foliation (S1). At the microscope a relic fine-spaced foliation, locally preserved by the following re-crystallization and parallel to the original lithological partitions, is evident. The original mineral associations is often replaced by HT/LP mimetic and syn-kinematic or static blasteses. D_2M_2 is the most evident structural fabric pre-dating the thermo-metamorphic events. It is represented by tight to isoclinal folds with N-S trending axes and easternward vergence. At the microscope the S2 foliation deformed the previously S1 and at the fold hinges a variously penetrative discrete crenulation cleavage (S2) is recognizable. M_3 is the first thermo-metamorphic event. It is associated to the intrusions of the Capo Bianco, San Martino and Portoferraio laccoliths (between ca. 8 and 7.2 Ma, Rocchi et alii, 2002) along pre-existing tectonic and lithological discontinuity. The laccoliths clearly crosscut the tectono-metamorphic fabric of the Punta Nera Unit. At this first magmatic event is associated a HT/LP blastesis of static garnet, wollastonite and epidote. Close to the contact between the magmatic intrusive bodies the country rocks are strongly re-crystallized and the original structure is oblitered. D_3M_4: is linked to the intrusion of the Monte Capanne pluton (6.9 Ma). Because of the flattening of the country rocks a penetrative foliation, sub-parallel to the surface of the plutonic body, developed during its intrusion and the uplift. Fluidal structures and discharge folding also developed. This structures affected both the country rocks and the laccoliths intruded in. At the meso-scale are also evident fractures, filled by calcite, cutting the garnet/wollastonite aggregate and later flattened and-or partially transposed. Late felsic products associated with the Monte Capanne pluton partly are deformed by the flattening and partly cut the flattening structures. The contact between the pluton and the country rocks itself is locally deformed by flattening structures. At the microscope the growth of HT/LP minerals, mimetic on the previous associations, or syn-kinematic or static, is evident. M_5: finally, during the last intrusive event (Orano porphyries, 6.8 Ma) a static thermo-metamorphic blastesis locally occurs post-dating the structures previously described. Only gentle folding, veins and fractures formation, and faulting processes followed the tectono-metamorphic and thermo-metamorphic deformation events. Conclusions The Punta Nera Unit represents another important element to understand the relationships between Alps and Apennines. In fact, the evidences of a pre-granitoid polyphased tectono-metamorphic framework in this metamorphic oceanic unit allow to correlate it to the Schistes Lustrés of the Alpine Corsica (e.g. Inzecca Massif, Duran Delga, 1984) and of the Northern Tyrrhenian area (e.g. the outcrops of oceanic metamorphic units in the Gorgona Island, Giglio Island and eastern Elba Island: Bortolotti et al., 2001; Pandeli et alii, 2001; Rossetti et al., 2001; Orti et al., 2002). References Barberi et al. (1969). F.126. Isola d'Elba. Note Ill. Carta Geol. It., 1:100.000. Ser. Geol. d'It. Bortolotti V. et al. (2001), Ofioliti, 26, 2001. Coli &Pandeli, (2001), Ofioliti, 26, 2001. Daniel &Jolivet, (1995), Bull. Soc. Geol. France, 166(4), 341--354. Durand-Delga M. (1984), Mem. Soc. Geol. It., 28, 285--329. Morelli M. et alii, (2002), Proceedings of Eurogranites 2002, 15th--21th Sept. 2002. Orti et alii, (2002), Ofioliti, 27, 2002. Pandeli et alii, (2001), Ofioliti, 26, 2001. Perrin M. (1975), Boll. Soc. Geol. It., 94, pp.1929--1955. Reutter K.J. and Spohn A., (1982), Ofioliti, 7, 467--478. Rocchi et alii, (2002), in Eurogranites 2002 Field Meeting Guide. 15th--21th Sept. 2002 Rossetti et al., (2001), Ofioliti, 26, 2001. Trevisan L., (1950), Mem. Ist. Geol. Univ. Padova, 16, 2--39.

High-frequency measurements reveal spatial and temporal patterns of dissolved organic matter in an urban water conveyance.

PubMed

Mihalevich, Bryce A; Horsburgh, Jeffery S; Melcher, Anthony A

2017-10-30

Stormwater runoff in urban areas can contribute high concentrations of dissolved organic matter (DOM) to receiving waters, potentially causing impairment to the aquatic ecosystem of urban streams and downstream water bodies. Compositional changes in DOM due to storm events in forested, agricultural, and urban landscapes have been well studied, but in situ sensors have not been widely applied to monitor stormwater contributions in urbanized areas, leaving the spatial and temporal characteristics of DOM within these systems poorly understood. We deployed fluorescent DOM (FDOM) sensors at upstream and downstream locations within a study reach to characterize the spatial and temporal changes in DOM quantity and sources within an urban water conveyance that receives stormwater runoff. Baseflow FDOM decreased over the summer season as seasonal flows upstream transported less DOM. FDOM fluctuated diurnally, the amplitude of which also declined as the summer season progressed. During storms, FDOM concentrations were rapidly elevated to values orders of magnitude greater than baseflow measurements, with greater concentrations at the downstream monitoring site, revealing high contributions from stormwater outfalls between the two locations. Observations from custom, in situ fluorometers resembled results obtained using laboratory methods for identifying DOM source material and indicated that DOM transitioned to a more microbially derived composition as the summer season progressed, while stormwater contributions contributed DOM from terrestrial sources. Deployment of a mobile sensing platform during varying flow conditions captured spatial changes in DOM concentration and composition and revealed contributions of DOM from outfalls during stormflows that would have otherwise been unobserved.

Chemical and optical changes in freshwater dissolved organic matter exposed to solar radiation

USGS Publications Warehouse

Osburn, C.L.; Morris, D.P.; Thorn, K.A.; Moeller, R.E.

2001-01-01

We studied the chemical and optical changes in the dissolved organic matter (DOM) from two freshwater lakes and a Sphagnum bog after exposure to solar radiation. Stable carbon isotopes and solid-state 13C-NMR spectra of DOM were used together with optical and chemical data to interpret results from experimental exposures of DOM to sunlight and from seasonal observations of two lakes in northeastern Pennsylvania. Solar photochemical oxidation of humic-rich bog DOM to smaller LMW compounds and to DIC was inferred from losses of UV absorbance, optical indices of molecular weight and changes in DOM chemistry. Experimentally, we observed a 1.2??? enrichment in ??13C and a 47% loss in aromatic C functionality in bog DOM samples exposed to solar UVR. Similar results were observed in the surface waters of both lakes. In late summer hypolimnetic water in humic Lake Lacawac, we observed 3 to 4.5??? enrichments in ??13C and a 30% increase in aromatic C relative to early spring values during spring mixing. These changes coincided with increases in molecular weight and UV absorbance. Anaerobic conditions of the hypolimnion in Lake Lacawac suggest that microbial metabolism may be turning over allochthonous C introduced during spring mixing, as well as autochthonous C. This metabolic activity produces HMW DOM during the summer, which is photochemically labile and isotopically distinct from allochthonous DOM or autochthonous DOM. These results suggest both photooxidation of allochthonous DOM in the epilimnion and autotrophic production of DOM by bacteria in the hypolimnion cause seasonal trends in the UV absorbance of lakes.

Relationships between land cover and dissolved organic matter change along the river to lake transition

USGS Publications Warehouse

Larson, James H.; Frost, Paul C.; Xenopoulos, Marguerite A.; Williams, Clayton J.; Morales-Williams, Ana M.; Vallazza, Jonathan M.; Nelson, J. C.; Richardson, William B.

2014-01-01

Dissolved organic matter (DOM) influences the physical, chemical, and biological properties of aquatic ecosystems. We hypothesized that controls over spatial variation in DOM quantity and composition (measured with DOM optical properties) differ based on the source of DOM to aquatic ecosystems. DOM quantity and composition should be better predicted by land cover in aquatic habitats with allochthonous DOM and related more strongly to nutrients in aquatic habitats with autochthonous DOM. Three habitat types [rivers (R), rivermouths (RM), and the nearshore zone (L)] associated with 23 tributaries of the Laurentian Great Lakes were sampled to test this prediction. Evidence from optical indices suggests that DOM in these habitats generally ranged from allochthonous (R sites) to a mix of allochthonous-like and autochthonous-like (L sites). Contrary to expectations, DOM properties such as the fluorescence index, humification index, and spectral slope ratio were only weakly related to land cover or nutrient data (Bayesian R 2 values were indistinguishable from zero). Strongly supported models in all habitat types linked DOM quantity (that is, dissolved organic carbon concentration [DOC]) to both land cover and nutrients (Bayesian R2 values ranging from 0.55 to 0.72). Strongly supported models predicting DOC changed with habitat type: The most important predictor in R sites was wetlands whereas the most important predictor at L sites was croplands. These results suggest that as the DOM pool becomes more autochthonous-like, croplands become a more important driver of spatial variation in DOC and wetlands become less important.

Distribution, facies, ages, and proposed tectonic associations of regionally metamorphosed rocks in east- and south-central Alaska

USGS Publications Warehouse

Dusel-Bacon, Cynthia; Csejtey, Bela; Foster, Helen L.; Doyle, Elizabeth O.; Nokleberg, Warren J.; Plafker, George

1993-01-01

Most of the exposed bedrock in east- and south-central Alaska has been regionally metamorphosed and deformed during Mesozoic and early Cenozoic time. All the regionally metamorphosed rocks are assigned to metamorphic-facies units on the basis of their temperature and pressure conditions and metamorphic age. North of the McKinley and Denali faults, the crystalline rocks of the Yukon- Tanana upland and central Alaska Range compose a sequence of dynamothermally metamorphosed Paleozoic and older(?) metasedimentary rocks and metamorphosed products of a Devonian and Mississippian continental-margin magmatic arc. This sequence was extensively intruded by postmetamorphic mid-Cretaceous and younger granitoids. Many metamorphic-unit boundaries in the Yukon-Tanana upland are low-angle faults that juxtapose units of differing metamorphic grade, which indicates that metamorphism predated final emplacement of the fault-bounded units. In some places, the relation of metamorphic grade across a fault is best explained by contractional faulting; in other places, it is suggestive of extensional faulting.Near the United States-Canadian border in the central Yukon- Tanana upland, metamorphism, plutonism, and thrusting occurred during a latest Triassic and Early Jurassic event that presumably resulted from the accretion of a terrane that had affinities to the Stikinia terrane onto the continental margin of North America. Elsewhere in the Yukon-Tanana upland, metamorphic rocks give predominantly late Early Cretaceous isotopic ages. These ages are interpreted to date either the timing of a subsequent Early Cretaceous episode of crustal thickening and metamorphism or, assuming that these other areas were also originally heated during the latest Triassic to Early Jurassic and remained buried, the timing of their uplift and cooling. This uplift and cooling may have resulted from extension.South of the McKinley and Denali faults and north of the Border Ranges fault system, medium-grade metamorphism across much of the southern Peninsular and Wrangellia terranes was early to synkinematic with the intrusion of tonalitic and granodioritic plutons of primarily Early and Middle Jurassic age in the Peninsular terrane and Late Jurassic age in the Wrangellia terrane. Areas metamorphosed during the Jurassic episode that crop out near the Border Ranges fault system were subsequently retrograded and deformed in Cretaceous and early Tertiary time during accretion of younger units to the south. North of the Jurassic metamorphic and plutonic complex, low-grade metamorphism affected the rest of the Wrangellia terrane sometime during Jurassic and (or) Cretaceous time.North of the Wrangellia terrane and immediately south of the McKinley and Denali faults, flyschoid rocks, which were deposited within a basin that separated the Wrangellia terrane from the western margin of North America, form a northeastward-tapering wedge. Within the western half of the wedge, flysch and structurally interleaved tectonic fragments were highly deformed and weakly metamorphosed; much of the metamorphism and deformation probably occurred sometime during mid- to Late Cretaceous time. In the eastern half of the wedge, flyschoid rocks form an intermediate-pressure Barrovian sequence (Maclaren metamorphic belt). Metamorphism of the Maclaren metamorphic belt was synkinematic with the Late Cretaceous to earliest Tertiary intrusion of foliated plutons of intermediate composition. Isotopic data suggest metamorphism extended into the early Tertiary and was accompanied by rapid uplift and cooling. Low- to medium-grade metamorphism throughout the wedge was probably associated with the accretion of the outboard Wrangellia terrane, as has been proposed for the Maclaren metamorphic belt.South of the Border Ranges fault system lie variably metamorphosed sequences of oceanic rocks that comprise the successively accreted Chugach, Yakutat, Ghost Rocks, and Prince William terranes. The Chugach terrane consists of three successively accreted sequences of differing metamorphic histories. Metamorphism in all the sequences was associated with north-directed underthrusting beneath either the combined Peninsular-Wrangellia terrane or the older and inner parts of the Chugach terrane. These sequences, from innermost to outermost are: (1) intermediate- to highpressure, transitional greenschist- to blueschist-facies metabasalt and metasedimentary rocks that were metamorphosed during the Early and Middle Jurassic; (2) prehnite-pumpellyite-facies melange that was metamorphosed sometime during the Jurassic and Cretaceous; and (3) low-pressure prehnite-pumpellyite- or greenschist- facies flysch and metavolcanic rocks that were initially metamorphosed during latest Cretaceous to early Tertiary time and, in the eastern Chugach Mountains, were subsequently overprinted by low-pressure amphibolite-facies metamorphism that accompanied widespread intrusion during Eocene time. A similar low-pressure-facies series also developed within melange and flysch of the Yakutat terrane; these rocks are also intruded by Eocene plutons and are correlated with similar rocks of the Chugach terrane.Seaward of the Chugach terrane are the strongly deformed but weakly metamorphosed (prehnite-pumpellyite-facies) deep-sea metasedimentary rocks and oceanic metavolcanic rocks of the Ghost Rocks and Prince William terranes. Metamorphism and deformation occurred during underthrusting of these terranes beneath the Chugach terrane in early Tertiary time and predated, perhaps by very little, intrusion by early Tertiary granitoids.

Tectonic evolution of kid metamorphic complex and the recognition of Najd fault system in South East Sinai, Egypt

NASA Astrophysics Data System (ADS)

Sultan, Yasser M.; El-Shafei, Mohamed K.; Arnous, Mohamed O.

2017-03-01

A low-to medium-grade metamorphic belt of a volcano-sedimentary succession occurs in the eastern side of South Sinai as a part of the northernmost extension of the Arabian-Nubian Shield in Egypt. The belt is known as the Kid metamorphic complex. It is considered as one of the major belt among the other exposed metamorphic belts in South Sinai. Here, we detect and investigate the signature of the Najd Fault system in South Sinai based on detailed structural analysis in field and digital image processing. The enhanced satellite image and the geo-spatial distributions confirm that the Kid belt is essentially composed of nine Precambrian units. Field relations and geometrical analysis of the measured structural data revealed that the study area underwent four successive deformational phases (D1-D4). D1 is an upright tight to isoclinal large-scale folds that caused few F1 small-scale folds and a steeply dipping S1 axial plane foliation. The second deformational event D2 produced dominant of sub-horizontal S2 foliation planes accompanied with recumbent isoclinal folds and NW-SE trending L2 lineations. The main sense during D2 was top-to-the-NW with local reversals to the SE. The third folding generations F3 is recorded as axial plane S3-surfaces and is characterized by open concentric folding that overprinting both F1 and F2 folds and has a flexural-slip mechanism. F3 fold hinges plunge to the west-northwest or east-southeast indicate north-northeast-south-southwest shortening during D3. The fourth deformational event D4 is characterized by NE plunging open concentric folding overprint the pre-existing fold generations and formed under flexural slip mechanism reflecting coaxial deformation and indicating change in the stress regime as a result of the change in shortening from NE-SW to NW-SE. This phase is probably accompanied with the final assembly of east and west Gondwana. The dextral NW-SE shear zone that bounded the southwestern portion of the metamorphic belt is probably related to reactivation of the Najd fault system during Oligo-Miocene in South Sinai.

First known EL5 chondrite - Evidence for dual genetic sequence for enstatite chondrites

NASA Technical Reports Server (NTRS)

Sears, D. W. G.; Weeks, K. S.; Rubin, A. E.

1984-01-01

The compositionally distinct EH and EL groups together with four (3-6) petrologic types which constitute the enstatite chondrites represent increasing degrees of metamorphic alteration. Although bulk composition variations preclude a simple conversion of EH4 into EL6 material, complex models which involve simultaneous bulk composition and petrologic type variations may be implied by other classification schemes in common use. Attention is presently given to the discovery of the first EL5 chondrite, which breaks the EH3,4-EH5-EL6 sequence and indicates that the enstatite chondrites constitute the two discrete, isochemical metamorphic sequences EH3-5 and EL5-6.

P-T-t conditions, Nd and Pb isotopic compositions and detrital zircon geochronology of the Massabesic Gneiss Complex, New Hampshire: isotopic and metamorphic evidence for the identification of Gander basement, central New England

USGS Publications Warehouse

Dorais, Michael J.; Wintsch, Robert P.; Kunk, Michael J.; Aleinikoff, John; Burton, William; Underdown, Christine; Kerwin, Charles M.

2012-01-01

We present new evidence for the assignment of the Neoproterozoic Massabesic Gneiss Complex of New Hampshire to the Gander terrane rather than the Avalon terrane. The majority of Avalonian (sensu stricto) igneous and meta-igneous rocks as defined in Maritime Canada have positive whole-rock ɛNd compared to more negative values for Gander rocks, although there is a region of overlap in ɛNd between the two terranes. Our samples from areas in Connecticut previously thought to be Avalonian and samples from the Willimantic dome have the same isotopic signatures as Maritime Canada Avalon. In contrast, samples from the Clinton dome of southern Connecticut plots exclusively in the Gander field. The majority of the orthogneiss samples from Lyme dome (coastal Connecticut), Pelham dome (central Massachusetts) and Massabesic Gneiss Complex also plot in the Gander field, with a few samples plotting in the overlap zone between Gander and Avalon. U-Pb age distributions of detrital zircon populations from quartzites from the Massabesic Gneiss Complex more closely approximate the data from the Lyme Dome rather than Avalon. Additionally, the similarity of the P-T-t path for the rocks of the Massabesic Gneiss Complex (established by thermobarometry and 40Ar/39Ar dating of amphibole, muscovite, biotite and K-feldspar) with that established in the Ganderian Lyme dome of southern Connecticut strengthens the assignment of these rocks to a single Gander block that docked to Laurentia during the Salinic Orogeny. The identification of Ganderian isotopic signatures for these rocks all of which show evidence for Alleghanian metamorphism, supports the hypothesis that Neoproterozoic Gander lower crustal rocks underlie southern New Hampshire, Massachusetts, and Connecticut, and that all rocks of the overlying Central Maine trough that largely escaped high-grade Alleghanian metamorphism are allochthonous. We suggest that during the Alleghanian, the docking of Gondwana caused Avalon to wedge into Gander, metamorphosing and partially melting the Massabesic Gneiss Complex to the observed P-T-t conditions, with the complex forming an uplifted sheet that was back-thrusted over the Avalonian wedge.

Metal isotope coded profiling of organic ligands by mass spectrometry in aquatic environments

NASA Astrophysics Data System (ADS)

Wichard, Thomas; Deicke, Michael; Frieder Mohr, Jan; Klein, Martin

2017-04-01

Metal isotope coded profiling (MICP) introduces a universal discovery platform for metal chelating natural products that act as metallophores, ion buffers or sequestering agents. The detection of cation and oxoanion complexing ligands is facilitated by the identification of unique isotopic signatures created by the application of isotopically pure metals. We present a targeted analysis of low-molecular-weight organic ligands based on fast UHPLC-ESI-MS measurements. Replacement of, for example, natural iron or molybdenum with isotopically pure 54Fe/58Fe (ratio 1:1) or 95Mo/98Mo (ratio 1:1) causes easily detectable unique isotopic signatures in the mass spectra of potential metal-complexing ligands. This can be achieved under laboratory conditions not only in growth media, but also by spiking directly aqueous samples or solid-phase extracts. Importantly, as the relative affinity of the metallophores for e.g., Mo or Fe is dependent on the pH, all experiments needs to be conducted under pH-controlled conditions. The improved ionization efficiency of some metal complexes helps to enhance the signal-to-noise ratio compared to the free ligand at the same chromatographic conditions. The methodology does not necessarily depend on HR-ESI-MS measurements (e.g., Q-Exactive Orbitrap) and can be applied to any mass spectrometer. With MICP, two birds can be killed with one stone: (i) the identification of metallophores (e.g., siderophores, molybdophores) for metal uptake by any organism and (ii) organic ligands which solely work as metal buffer in dissolved organic matter (DOM). We currently address following two main research lines: First, DOM has often been used as a proxy for bio-productivity in terms of a carbon source; however, the specific impact of DOM as a "metal buffer" for biological processes is still under-investigated. Upon the administration of individual isotopes or isotopic pairs, for example, 54Fe/58Fe, 63Cu/65Cu, 66Zn/68Zn, or 95Mo/98Mo and subsequent measurements by mass spectrometry, organic ligands can be identified that contribute potentially to the regulation of bioavailability and toxicity of metals in the water column. Secondly, metal acquisition by ligand exchange processes is vital for macroalgae-bacteria interactions. Both alga and bacteria contribute to the "soup of organic ligands" which potentially increases the bioavailability of metals due to various ligand exchanges with DOM. In particular, we will outline the analytical process resulting in the identification of ligands in the chemosphere of the marine macroalga Ulva (Chlorophyta) and its associated bacteria. In summary, the identification of metal organic ligands in natural samples will pave the way for understanding the organic ligand-mediated metal acquisition shuttled from DOM to alga. (References: Wichard T. (2016) Front. Mar. Sci. 3:131; Deicke M., Mohr J.M., Wichard T. (2014) Analyst, 139, 6096-6099)

Pan-Arctic Distribution of Bioavailable Dissolved Organic Matter and Linkages With Productivity in Ocean Margins

NASA Astrophysics Data System (ADS)

Shen, Yuan; Benner, Ronald; Kaiser, Karl; Fichot, Cédric G.; Whitledge, Terry E.

2018-02-01

Rapid environmental changes in the Arctic Ocean affect plankton productivity and the bioavailability of dissolved organic matter (DOM) that supports microbial food webs. We report concentrations of dissolved organic carbon (DOC) and yields of amino acids (indicators of labile DOM) in surface waters across major Arctic margins. Concentrations of DOC and bioavailability of DOM showed large pan-Arctic variability that corresponded to varying hydrological conditions and ecosystem productivity, respectively. Widespread hot spots of labile DOM were observed over productive inflow shelves (Chukchi and Barents Seas), in contrast to oligotrophic interior margins (Kara, Laptev, East Siberian, and Beaufort Seas). Amino acid yields in outflow gateways (Canadian Archipelago and Baffin Bay) indicated the prevalence of semilabile DOM in sea ice covered regions and sporadic production of labile DOM in ice-free waters. Comparing these observations with surface circulation patterns indicated varying shelf subsidies of bioavailable DOM to Arctic deep basins.

Influence of Flood and Drought Conditions on Dissolved Organic Matter Distribution in Northern Gulf of Mexico Shelf Waters

NASA Astrophysics Data System (ADS)

Shank, G. C.; Liu, Q.; Patterson, L.; Kowalczuk, P.

2012-12-01

DOC, CDOM, and EEM PARAFAC analyses were used to examine DOM distribution along the Louisiana (LA) and Texas (TX) continental shelves in the northern Gulf of Mexico during cruises in May and August of the 2011 Mississippi basin flood year, and May, June, and August of the 2012 Mississippi basin drought year. For both 2011 and 2012, CDOM and DOC levels were well-correlated with salinity on the LA shelf. However, the mixing curves for each parameter were markedly different between 2011 and 2012 and CDOM:DOC ratios, indicative of terrestrial organic matter inputs, were much higher during 2011 than during 2012. EEM PARAFAC results confirmed a much higher terrestrial DOM signature in LA shelf waters for 2011, but also a higher terrestrial DOM signature for TX waters in 2012 as the drought in the western Gulf region subsided. CDOM:DOC ratios were anomalously high offshore of Atchafalaya Bay and the Breton-Chandeleur Sound complex indicating coastal wetlands augment the terrestrial DOM discharged through the Mississippi and Atchafalaya Rivers. At several sites along the LA and TX shelves during both 2011 and 2012, CDOM was higher near bottom than at mid-depth without concomitant DOC increases, possibly due to microbial processing of settling phytoplankton cells, sedimentary fluxes, and benthic algal activity which was especially prevalent along the TX shelf. Results from simulated solar radiation experiments indicate that shelf water CDOM readily photobleaches with losses of >50% likely in surface waters over the summer, while DOC photooxidation is at least an order of magnitude slower than CDOM photobleaching.;

Insights into the redox components of dissolved organic matters during stabilization process.

PubMed

Yuan, Ying; Xi, Bei-Dou; He, Xiao-Song; Ma, Yan; Zhang, Hui; Li, Dan; Zhao, Xin-Yu

2018-05-01

The changes of dissolved organic matter (DOM) components during stabilization process play significant effects on its redox properties but are little reported. Composting is a stabilization process of DOM, during which both the components and electron transfer capacities (ETCs) of DOM change. The redox components within compost-derived DOM during the stabilization process are investigated in this study. The results show that compost-derived DOM contained protein-like, fulvic-like, and humic-like components. The protein-like component decreases during composting, whereas the fulvic- and humic-like components increase during the process. The electron-donating capacity (EDC), electron-accepting capacity (EAC), and ETC of compost-derived DOM all increase during composting but their correlations with the components presented significant difference. The humic-like components were the main functional component responsible for both EDC and ETC, whereas the protein- and fluvic-like components show negative effects with the EAC, EDC, and ETC, suggesting that the components within DOM have specific redox properties during the stabilization process. These findings are very meaningful for better understanding the geochemical behaviors of DOM in the environment.

Molecular Features of Dissolved Organic Matter Produced by Picophytoplankton

NASA Astrophysics Data System (ADS)

Ma, X.; Coleman, M.; Waldbauer, J.

2016-02-01

Compounds derived from picophytoplankton through exudation, grazing and viral lysis contribute a large proportion of labile DOM to the ocean. This labile DOM is rapidly turned over by and exchanged among microbial communities. However, identifying labile DOM compounds and tracking their sources and sinks in ocean ecosystems is complicated by the presence of non-labile DOM which has a significantly larger reservoir size and longer residence time. This study focuses on investigating labile DOM produced by single-strain cyanobacteria isolates via different modes of release and varied nutrient conditions. DOM compounds are analyzed by high-resolution mass spectrometry. Statistical comparison between intracellular and extracellular molecular data of Synechococcus WH7803 revealed noticeable differences in terms of compound number, size and structure. Incubation experiments using combined whole seawater and diluent of grazer-free or viral-free water at the BATS time-series station in Sargasso Sea yielded complimentary data to be synthesized with data from lab cultures. The compositional features of each type of DOM could serve as future proxies for different modes of DOM production in the oceans.

NACSN, note 67--Application for revision of Articles 36 and 37, Lithodemic units of the North American stratigraphic code

USGS Publications Warehouse

Easton, Robert M.; Edwards, Lucy E.; Orndorff, Randall C.; Duguet, Manuel; Ferrusquia-Villafranca, Ismael

2015-01-01

Currently the North American Stratigraphic Code, (NACSN 2005, Article 37) sets restrictions on the use of the term “complex” for lithodemic units. With exceptions for “volcanic complex” and “structural complex,” a complex must consist of more than one genetic class of rock (i.e., sedimentary, igneous or metamorphic). Thus, the use of the term “complex” to describe masses of intrusive rocks is not allowed. Asimilar restriction is also included in a recent British Geological Survey proposal for using lithodemic units to classify igneous rocks (Gillespie et al. 2008).Currently the North American Stratigraphic Code, (NACSN 2005, Article 37) sets restrictions on the use of the term “complex” for lithodemic units. With exceptions for “volcanic complex” and “structural complex,” a complex must consist of more than one genetic class of rock (i.e., sedimentary, igneous or metamorphic). Thus, the use of the term “complex” to describe masses of intrusive rocks is not allowed. Asimilar restriction is also included in a recent British Geological Survey proposal for using lithodemic units to classify igneous rocks (Gillespie et al. 2008).

The onset of metamorphism in ordinary and carbonaceous chondrites

USGS Publications Warehouse

Grossman, J.N.; Brearley, A.J.

2005-01-01

Ordinary and carbonaceous chondrites of the lowest petrologic types were surveyed by X-ray mapping techniques. A variety of metamorphic effects were noted and subjected to detailed analysis using electron microprobe, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and cathodoluminescence (CL) methods. The distribution of Cr in FeO-rich olivine systematically changes as metamorphism increases between type 3.0 and type 3.2. Igneous zoning patterns are replaced by complex ones and Cr-rich coatings develop on all grains. Cr distributions in olivine are controlled by the exsolution of a Cr-rich phase, probably chromite. Cr in olivine may have been partly present as tetrahedrally coordinated Cr3+. Separation of chromite is nearly complete by petrologic type 3.2. The abundance of chondrules showing an inhomogeneous distribution of alkalis in mesostasis also increases with petrologic type. TEM shows this to be the result of crystallization of albite. Residual glass compositions systematically change during metamorphism, becoming increasingly rich in K. Glass in type I chondrules also gains alkalis during metamorphism. Both types of chondrules were open to an exchange of alkalis with opaque matrix and other chondrules. The matrix in the least metamorphosed chondrites is rich in S and Na. The S is lost from the matrix at the earliest stages of metamorphism due to coalescence of minute grains. Progressive heating also results in the loss of sulfides from chondrule rims and increases sulfide abundances in coarse matrix assemblages as well as inside chondrules. Alkalis initially leave the matrix and enter chondrules during early metamorphism. Feldspar subsequently nucleates in the matrix and Na re-enters from chondrules. These metamorphic trends can be used to refine classification schemes for chondrites. Cr distributions in olivine are a highly effective tool for assigning petrologic types to the most primitive meteorites and can be used to subdivide types 3.0 and 3.1 into types 3.00 through 3.15. On this basis, the most primitive ordinary chondrite known is Semarkona, although even this meteorite has experienced a small amount of metamorphism. Allan Hills (ALH) A77307 is the least metamorphosed CO chondrite and shares many properties with the ungrouped carbonaceous chondrite Acfer 094. Analytical problems are significant for glasses in type II chondrules, as Na is easily lost during microprobe analysis. As a result, existing schemes for chondrule classification that are based on the alkali content of glasses need to be revised. ?? The Meteorological Society, 2005.

Effects of iron on optical properties of dissolved organic matter.

PubMed

Poulin, Brett A; Ryan, Joseph N; Aiken, George R

2014-09-02

Iron is a source of interference in the spectroscopic analysis of dissolved organic matter (DOM); however, its effects on commonly employed ultraviolet and visible (UV-vis) light adsorption and fluorescence measurements are poorly defined. Here, we describe the effects of iron(II) and iron(III) on the UV-vis absorption and fluorescence of solutions containing two DOM fractions and two surface water samples. In each case, regardless of DOM composition, UV-vis absorption increased linearly with increasing iron(III). Correction factors were derived using iron(III) absorption coefficients determined at wavelengths commonly used to characterize DOM. Iron(III) addition increased specific UV absorbances (SUVA) and decreased the absorption ratios (E2:E3) and spectral slope ratios (SR) of DOM samples. Both iron(II) and iron(III) quenched DOM fluorescence at pH 6.7. The degree and region of fluorescence quenching varied with the iron:DOC concentration ratio, DOM composition, and pH. Regions of the fluorescence spectra associated with greater DOM conjugation were more susceptible to iron quenching, and DOM fluorescence indices were sensitive to the presence of both forms of iron. Analyses of the excitation-emission matrices using a 7- and 13-component parallel factor analysis (PARAFAC) model showed low PARAFAC sensitivity to iron addition.

Toxic metals (Ni2+, Pb2+, Hg2+) binding affinity of dissolved organic matter (DOM) derived from different ages municipal landfill leachate

NASA Astrophysics Data System (ADS)

Rikta, S. Y.; Tareq, Shafi M.; Uddin, M. Khabir

2018-03-01

Solid waste production is rapidly increasing in Bangladesh and landfill leachate is the consequence of the decomposition of this waste. These leachates contain heavy metals and significant amount of dissolved organic matter (DOM). DOM is known to have considerable role in heavy metals speciation. Hence, it is important to characterize DOM/leachate and evaluate toxic metals binding affinity of DOM. The objectives of this study were to characterize the DOM in landfill leachate through physico-chemical and optical analyses and to investigate the toxic metals (Ni2+, Pb2+ and Hg2+) binding affinity of three different ages (fresh sample L-1, young sample L-2 and mature sample L-3) DOM samples. Results suggested that leachate is a potential pollutant which contained very high organic pollutant load. Conditional stability constant (Log K) and percentages of fluorophores that correspond to metal binding (% f) values indicated that young DOM sample (L-2) had the highest binding affinity to all the three metals ions. In general, DOM samples showed the following order affinity to the metal ions; Ni2+ binding affinity: L-2 > L-3 > L-1, Pb2+ binding affinity: L-2 > L-3 > L-1 and Hg2+ binding affinity: L-2 > L-1 > L-3.

Effects of iron on optical properties of dissolved organic matter

USGS Publications Warehouse

Poulin, Brett; Ryan, Joseph N.; Aiken, George R.

2014-01-01

Iron is a source of interference in the spectroscopic analysis of dissolved organic matter (DOM); however, its effects on commonly employed ultraviolet and visible (UV–vis) light adsorption and fluorescence measurements are poorly defined. Here, we describe the effects of iron(II) and iron(III) on the UV–vis absorption and fluorescence of solutions containing two DOM fractions and two surface water samples. In each case, regardless of DOM composition, UV–vis absorption increased linearly with increasing iron(III). Correction factors were derived using iron(III) absorption coefficients determined at wavelengths commonly used to characterize DOM. Iron(III) addition increased specific UV absorbances (SUVA) and decreased the absorption ratios (E2:E3) and spectral slope ratios (SR) of DOM samples. Both iron(II) and iron(III) quenched DOM fluorescence at pH 6.7. The degree and region of fluorescence quenching varied with the iron:DOC concentration ratio, DOM composition, and pH. Regions of the fluorescence spectra associated with greater DOM conjugation were more susceptible to iron quenching, and DOM fluorescence indices were sensitive to the presence of both forms of iron. Analyses of the excitation–emission matrices using a 7- and 13-component parallel factor analysis (PARAFAC) model showed low PARAFAC sensitivity to iron addition.

Evaluating Activated Carbon Adsorption of Dissolved Organic Matter and Micropollutants Using Fluorescence Spectroscopy.

PubMed

Shimabuku, Kyle K; Kennedy, Anthony M; Mulhern, Riley E; Summers, R Scott

2017-03-07

Dissolved organic matter (DOM) negatively impacts granular activated carbon (GAC) adsorption of micropollutants and is a disinfection byproduct precursor. DOM from surface waters, wastewater effluent, and 1 kDa size fractions were adsorbed by GAC and characterized using fluorescence spectroscopy, UV-absorption, and size exclusion chromatography (SEC). Fluorescing DOM was preferentially adsorbed relative to UV-absorbing DOM. Humic-like fluorescence (peaks A and C) was selectively adsorbed relative to polyphenol-like fluorescence (peaks T and B) potentially due to size exclusion effects. In the surface waters and size fractions, peak C was preferentially removed relative to peak A, whereas the reverse was found in wastewater effluent, indicating that humic-like fluorescence is associated with different compounds depending on DOM source. Based on specific UV-absorption (SUVA), aromatic DOM was preferentially adsorbed. The fluorescence index (FI), if interpreted as an indicator of aromaticity, indicated the opposite but exhibited a strong relationship with average molecular weight, suggesting that FI might be a better indicator of DOM size than aromaticity. The influence of DOM intermolecular interactions on adsorption were minimal based on SEC analysis. Fluorescence parameters captured the impact of DOM size on the fouling of 2-methylisoborneol and warfarin adsorption and correlated with direct competition and pore blockage indicators.

Bioavailability of atrazine, pyrene and benzo[a]pyrene in European river waters

USGS Publications Warehouse

Akkanen, J.; Penttinen, S.; Haitzer, M.; Kukkonen, J.V.K.

2001-01-01

Thirteen river waters and one humic lake water were characterized. The effects of dissolved organic matter (DOM) on the bioavailability of atrazine, pyrene and benzo[a]pyrene (B[a]P) was evaluated. Binding of the chemicals by DOM was analyzed with the equilibrium dialysis technique. For each of the water samples, 24 h bioconcentration factors (BCFs) of the chemicals were measured in Daphnia magna. The relationship between DOM and other water characteristics (including conductivity, water hardness and pH), and bioavailability of the chemicals was studied by performing several statistical analyses, including multiple regression analyses, to determine how much of the variation of BCF values could be explained by the quantity and quality of DOM. The bioavailability of atrazine was not affected by DOM or any other water characteristics. Although equilibrium dialysis showed binding of pyrene to DOM, the bioavailability of pyrene was not significantly affected by DOM. The bioavailability of B[a]P was significantly affected by both the quality and quantity of DOM. Multiple regression analyses, using the quality (ABS270 and HbA%) and quantity of DOM as variables, explainedup to 70% of the variation in BCF of B[a]P in the waters studied. ?? 2001 Elsevier Science Ltd. All rights reserved.

Stable isotope evidence for hydrologic conditions during regional metamorphism in the Panamint Mountains, California

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bergfeld, D.; Nabelek, P.I.; Labotka, T.C.

1992-01-01

The Kingston Peak Formation forms part of the Panamint Mountains, California, metamorphic core-complex. Peak tremolite-grade metamorphism as exhibited in Wildrose Canyon occurred in the Jurassic; a retrograde thermal event may have occurred in the Cretaceous. The formation consists dominantly of interbedded siliceous limestones and graphitic calcareous schists. Stable isotopic analysis shows two distinct groups of data. delta O-18 values of calcite from the limestones range between 15.3 and 17.3[per thousand], probably reflecting their original Proterozoic depositional values. Likewise the delta C-13 values are also unshifted, ranging from +1% to +3.8%o. In contrast, delta O-18 values of calcite from the schistsmore » are for the most part > 20[per thousand]. These high values could reflect the original depostional conditions; however, they may be due to equilibration with silicate minerals which range from 14.9 to 17.9[per thousand]. Overall, the combined oxygen and carbon isotopic data indicate that most isotopic changes can be explained by closed-system equilibration. Only a limited amount of interaction with externally-derived fluids during metamorphism is evident in the isotopic data. The interaction may have been confined to vicinities of faults and fractures which are common in Wildrose Canyon.« less

Myofiber turnover is used to retrofit frog jaw muscles during metamorphosis.

PubMed

Alley, K E

1989-01-01

Metamorphic reorganization of the head in anuran amphibians entails abrupt restructuring of the jaw complex as larval feeding structures are transformed into their adult configurations. In this morphometric study, light microscopy wa used to analyze the larval maturation and metamorphic transfiguration of the adductor jaw muscles in the leopard frog (Rana pipiens). Larval jaw muscles, first established during embryogenesis, continue to grow by fiber addition until prometamorphosis, stage XII. Thereafter, fiber number remains stable but additional muscle growth continues by hypertrophy of the individual fibers until metamorphic climax. During metamorphic stages XIX-XXIII, a complete involution of all larval myofibers occurs. Simultaneously, within the same muscle beds, a second wave of myogenesis produces myoblasts which are the precursors of adult jaw myofibers. New muscle fibers continue to be added to these muscles well after the completion of metamorphosis; however, the total duration of the postmetamorphic myogenic period has not been defined. These observations provide clear evidence that the entir population of primary myofibers used in larval oral activity disappears from the adductor muscle beds and is replaced by a second wave of myogenesis commencing during climax. These findings indicate that the adductor jaw muscles are prepared for adult feeding by a complicated cellular process that retrofits existing muscle beds with a completely new complement of myofibers.

Numerical model of the transition from continental rifting to oceanization: the case study of the Ligure-Piemontese ocean.

NASA Astrophysics Data System (ADS)

Roda, M.; Marotta, A. M.; Conte, K.; Spalla, M. I.

2015-12-01

The transition from continental rifting to oceanization has been investigated by mean of a 2D thermo-mechanical numerical model in which the formation of oceanic crust by mantle serpentinization, due to the hydration of the uprising peridotite, as been implemented. Model predictions have been compared with natural data related to the Permian-Triassic thinning affecting the continental lithosphere of the Alpine domain, in order to identify which portions of the present Alpine-Apennine system, preserving the imprints of Permian-Triassic high temperature (HT) metamorphism, is compatible, in terms of lithostratigraphy and tectono-metamorphic evolution, with a lithospheric extension preceding the opening of the Ligure-Piemontese oceanic basin. At this purpose age, petrological and structural data from the Alpine and Apennine ophiolite complexes are compared with model predictions from the oceanization stage. Our comparative analysis supports the thesis that the lithospheric extension preceding the opening of the Alpine Tethys did not start on a stable continental lithosphere, but developed by recycling part of the old Variscan collisional suture. The HT Permian-Triassic metamorphic re-equilibration overprints an inherited tectonic and metamorphic setting consequent to the Variscan subduction and collision, making the Alps a key case history to explore mechanisms responsible for the re-activation of orogenic scars.

Modelling the interactions between DOM and bacteria in marine ecosystems: state of the art and future prospective

NASA Astrophysics Data System (ADS)

polimene, Luca

2014-05-01

Marine dissolved organic matter (DOM) is the main source of carbon, nutrients and energy for marine prokaryotes, the most abundant life form in the oceans. Only a fraction of assimilated DOM is used by prokaryotes to synthesise new biomass (particulate organic matter, POM), while the rest is used for respiration or is excreted back into the environment as recalcitrant DOM (RDOM). The relative proportions of assimilated DOM that is distributed either to POM, respiration or RDOM is not constant but highly variable depending on the environmental conditions (e.g. nutrient availability, quality/quantity of DOM, temperature). This metabolic plasticity allows bacteria to shape the biogeochemistry of the surrounding waters by modulating three key carbon/energy fluxes fundamental for the functioning of the marine ecosystem: i) the transition from DOM to POM, ii) the remineralisation of carbon and nutrients, and iii) the transformation of labile DOM into recalcitrant DOM. The explicit representation of these processes (and their relative efficiency) in marine ecosystem models is a crucial (and challenging) issue which cannot be overlooked if we want to properly simulate marine biogeochemical cycles under present and climate changing conditions. This talk will provide an overview of how state of the art marine ecosystem models represent the interactions between DOM and bacteria, highlighting strengths and limits of the approaches currently used. A summary of future developments along with issues still open on the topic will also be presented and discussed.

A Transformational Journey: Compositional Changes in Organic Matter during Desorption from Sediments

NASA Astrophysics Data System (ADS)

Matiasek, S. J.; Pellerin, B. A.; Spencer, R.; Bergamaschi, B. A.; Hernes, P.

2016-12-01

The release of organic matter (OM) from suspended particles via desorption is a critical component of OM cycling since dissolved OM (DOM) fuels aquatic ecosystems and is a precursor for disinfection by-products formation. This study assessed the elemental and molecular composition of DOM desorbed abiotically from sediments and soils of an irrigated agricultural watershed of northern California. Relative to mineral-bound OM, the released DOM was nitrogen-poor (lower carbon:nitrogen ratios) and depleted in amino acids and lignin phenols (lower carbon-normalized yields). Water-extracted DOM appeared substantially more degraded than its parent particulate OM with increased molar contributions of acidic amino acids, non-protein amino acids, and acidic lignin phenols, all molecular indicators of a more extensively processed OM pool. Desorption processes also significantly altered lignin compositional ratios which help distinguish vascular-plant sources of DOM. Specific optical parameters, including spectral slope, specific UV absorbance at 254 nm (SUVA254), and fluorescence index (FI), did not constitute useful proxies for the desorbed DOM pool, while absorption coefficients and fluorescence peak intensities were strongly correlated with extracted DOM concentrations and composition. This study highlights the profound impact of desorption on DOM composition which, if unaccounted for, could lead to misinterpretations of common biomarkers and optical proxies used to predict DOM sources and reactivity. Our findings suggest that sediments contribute a biogeochemically distinct source of DOM to surface waters, with potential impacts on aquatic health and drinking water quality.

Shift in the chemical composition of dissolved organic matter in the Congo River network

NASA Astrophysics Data System (ADS)

Lambert, Thibault; Bouillon, Steven; Darchambeau, François; Massicotte, Philippe; Borges, Alberto V.

2016-09-01

The processing of terrestrially derived dissolved organic matter (DOM) during downstream transport in fluvial networks is poorly understood. Here, we report a dataset of dissolved organic carbon (DOC) concentrations and DOM composition (stable carbon isotope ratios, absorption and fluorescence properties) acquired along a 1700 km transect in the middle reach of the Congo River basin. Samples were collected in the mainstem and its tributaries during high-water (HW) and falling-water (FW) periods. DOC concentrations and DOM composition along the mainstem were found to differ between the two periods because of a reduced lateral mixing between the central water masses of the Congo River and DOM-rich waters from tributaries and also likely because of a greater photodegradation during FW as water residence time (WRT) increased. Although the Cuvette Centrale wetland (one of the world's largest flooded forests) continuously releases highly aromatic DOM in streams and rivers of the Congo Basin, the downstream transport of DOM was found to result in an along-stream gradient from aromatic to aliphatic compounds. The characterization of DOM through parallel factor analysis (PARAFAC) suggests that this transition results from (1) the losses of aromatic compounds by photodegradation and (2) the production of aliphatic compounds by biological reworking of terrestrial DOM. Finally, this study highlights the critical importance of the river-floodplain connectivity in tropical rivers in controlling DOM biogeochemistry at a large spatial scale and suggests that the degree of DOM processing during downstream transport is a function of landscape characteristics and WRT.

Relationships between dissolved organic matter and discharge: New insights from in-situ measurements in a northern forested watershed

NASA Astrophysics Data System (ADS)

Pellerin, B. A.; Shanley, J. B.; Saraceno, J.; Aiken, G.; Sebestyen, S. D.; Bergamaschi, B. A.

2012-12-01

Quantifying the fundamental linkages between hydrology and dissolved organic matter (DOM) dynamics in streams and rivers is critical for understanding carbon loads, ecosystem food webs and metal transport. Accurately assessing this relationship is difficult, however, given that rapid changes in water flow paths and associated DOM sources are often not captured by traditional discrete sampling intervals of weeks to months. We explored DOM - discharge relationships at Sleepers River below a 40.5 hectare USGS research watershed in northern Vermont by making 30 minute chromophoric DOM fluorescence (FDOM) measurements in-situ since October 2008 along with periodic discrete sampling for dissolved organic carbon. There is a tight coupling between the timing of increases in FDOM and discharge at Sleepers during events, but the ratio of FDOM to discharge exhibited considerable variability across seasons and events, as did FDOM-discharge hysteresis (FDOM variously peaked 1-4 hours after streamflow). Discrete DOM quality indicators (spectral slope, fluorescence index, SUVA) indicate DOM was predominantly terrestrial at all but the lowest flows, highlighting the important role of DOM-rich terrestrial flow paths as the primary source of stream DOM. Our results suggest that changes in flow paths are likely to be the primary drivers of future changes in DOM transport from this site rather than changes in DOM quality. Overcoming significant challenges inherent in continuous sensor deployments in watersheds (e.g. ice cover, suspended particles, remote communication and power) will allow for new insights into watershed biogeochemistry.

Variable C : N : P stoichiometry of dissolved organic matter cycling in the Community Earth System Model

DOE PAGES

Letscher, R. T.; Moore, J. K.; Teng, Y. -C.; ...

2014-06-16

Dissolved organic matter (DOM) plays an important role in the ocean's biological carbon pump by providing an advective/mixing pathway for ~ 20% of export production. DOM is known to have a stoichiometry depleted in nitrogen (N) and phosphorus (P) compared to the particulate organic matter pool, a~fact that is often omitted from biogeochemical-ocean general circulation models. However the variable C : N : P stoichiometry of DOM becomes important when quantifying carbon export from the upper ocean and linking the nutrient cycles of N and P with that of carbon. Here we utilize recent advances in DOM observational data coveragemore » and offline tracer-modeling techniques to objectively constrain the variable production and remineralization rates of the DOM C / N / P pools in a simple biogeochemical-ocean model of DOM cycling. The optimized DOM cycling parameters are then incorporated within the Biogeochemical Elemental Cycling (BEC) component of the Community Earth System Model and validated against the compilation of marine DOM observations. The optimized BEC simulation including variable DOM C : N : P cycling was found to better reproduce the observed DOM spatial gradients than simulations that used the canonical Redfield ratio. Global annual average export of dissolved organic C, N, and P below 100 m was found to be 2.28 Pg C yr -1 (143 Tmol C yr -1), 16.4 Tmol N yr -1, and 1 Tmol P yr -1, respectively with an average export C : N : P stoichiometry of 225 : 19 : 1 for the semilabile (degradable) DOM pool. DOC export contributed ~ 25% of the combined organic C export to depths greater than 100 m.« less

Variable C : N : P stoichiometry of dissolved organic matter cycling in the Community Earth System Model

DOE PAGES

Letscher, R. T.; Moore, J. K.; Teng, Y. -C.; ...

2015-01-12

Dissolved organic matter (DOM) plays an important role in the ocean's biological carbon pump by providing an advective/mixing pathway for ~ 20% of export production. DOM is known to have a stoichiometry depleted in nitrogen (N) and phosphorus (P) compared to the particulate organic matter pool, a fact that is often omitted from biogeochemical ocean general circulation models. However the variable C : N : P stoichiometry of DOM becomes important when quantifying carbon export from the upper ocean and linking the nutrient cycles of N and P with that of carbon. Here we utilize recent advances in DOM observationalmore » data coverage and offline tracer-modeling techniques to objectively constrain the variable production and remineralization rates of the DOM C : N : P pools in a simple biogeochemical-ocean model of DOM cycling. The optimized DOM cycling parameters are then incorporated within the Biogeochemical Elemental Cycling (BEC) component of the Community Earth System Model (CESM) and validated against the compilation of marine DOM observations. The optimized BEC simulation including variable DOM C : N : P cycling was found to better reproduce the observed DOM spatial gradients than simulations that used the canonical Redfield ratio. Global annual average export of dissolved organic C, N, and P below 100 m was found to be 2.28 Pg C yr -1 (143 Tmol C yr -1, 16.4 Tmol N yr -1, and 1 Tmol P yr -1, respectively, with an average export C : N : P stoichiometry of 225 : 19 : 1 for the semilabile (degradable) DOM pool. Dissolved organic carbon (DOC) export contributed ~ 25% of the combined organic C export to depths greater than 100 m.« less

Differences in dissolved organic matter lability between alpine glaciers and alpine rock glaciers of the American West

NASA Astrophysics Data System (ADS)

Hall, E.; Fegel, T. S., II; Baron, J.; Boot, C. M.

2015-12-01

While alpine glaciers in montane regions represent the largest flux of dissolved organic matter (DOM) from global ice melt no research has examined the bioavailability of DOM melted out of glacial ice in the western continental United States. Furthermore, rock glaciers are an order of magnitude more abundant than ice glaciers in U.S., yet are not included in budgets for perennial ice carbon stores. Our research aims to understand differences in the bioavailability of carbon from ice glaciers and rock glaciers along the Central Rocky Mountains of Colorado. Identical microbial communities were fed standardized amounts of DOM from four different ice glacier-rock glaciers pairs. Using laboratory incubations, paired with mass spectrometry based metabolomics and 16S gene sequencing; we were able to examine functional definitions of DOM lability in glacial ice. We hypothesized that even though DOM quantities are similar in the outputs of both glacial types in our study area, ice glacial DOM would be more bioavailable than DOM from rock glaciers due to higher proportions of byproducts from microbial metabolism than rock glacier DOM, which has higher amounts of "recalcitrant" plant material. Our results show that DOM from ice glaciers is more labile than DOM from geologically and geographically similar paired rock glaciers. Ice glacier DOM represents an important pool of labile carbon to headwater ecosystems of the Rocky Mountains. Metabolomic analysis shows numerous compounds from varying metabolite pathways, including byproducts of nitrification before and after incubation, meaning that, similar to large maritime glaciers in Alaska and Europe, subglacial environments in the mountain ranges of the United States are hotspots for biological activity and processing of organic carbon.

Molecular Hysteresis of Dissolved Organic Matter in the Connecticut River Watershed

NASA Astrophysics Data System (ADS)

Wagner, S.; Hoyle, J. B.; Matt, S.; Raymond, P. A.; Saiers, J. E.; Dittmar, T.; Stubbins, A.

2017-12-01

Rainfall-runoff processes have emerged as key controllers of the quantity and quality of terrestrial dissolved organic matter (DOM) exported from the landscape to inland waters. Hydrological events result in increased river discharge and a concomitant release of large amounts of DOM into fluvial networks. This study is part of a Macrosystems project which aims to test the Pulse-Shunt Concept: where rivers are converted from active to passive pipes during high discharge events ("pulse"), transporting labile, terrestrial DOM downstream ("shunt"), and relocating biogeochemical hotspots for DOM from the upper to the lower reaches of the watershed. The primary objective of our study was to track hysteretic changes in riverine DOM molecular composition over the course of a storm event. Samples were collected from nested watersheds in the Passumpsic River catchment, a tributary of the Connecticut River (USA). High resolution monitoring (via in-situ sondes) and high frequency collection of discreet samples (for FT-ICR/MS and other analyses) was necessary to capture short-term, hydrologically-driven variations in DOM concentration and composition. At the onset of the discharge event, we observed a unique DOM signature, enriched in aliphatic, and potentially biolabile, DOM. During peak discharge, and along the falling limb of the hydrograph, an aromatic, terrestrial-type DOM signature was more prevalent. These initial findings support the pulse-shunt hypothesis, providing evidence for the release of labile forms of DOM into rivers during the onset of a storm event, which apparently persists across low-to-high stream orders. Insights into the molecular hysteresis of fluvial DOM spotlights the impact of watershed hydrology on biogeochemical cycling in river networks.

Further insight into the roles of the chemical composition of dissolved organic matter (DOM) on ultrafiltration membranes as revealed by multiple advanced DOM characterization tools.

PubMed

Ly, Quang Viet; Hur, Jin

2018-06-01

This study assessed the relative contributions of different constitutes in dissolved organic matter (DOM) with two different sources (i.e., urban river and effluent) to membrane fouling on three types of ultrafiltration (UF) membranes via excitation emission matrix - parallel factor analysis (EEM-PARAFAC), size exclusion chromatography (SEC), and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Two polyethersulfone membranes with different pore sizes and one regenerated cellulose membrane were used as representative hydrophobic (HPO) and hydrophilic (HPI) UF membranes, respectively. Although size exclusion effect was found to be the most prevailing rejection mechanism, the behaviors of individual fluorescent components (one tryptophan-like, one microbial-humic-like, and terrestrial humic-like) and different size fractions upon the UF filtration revealed that chemical interactions (e.g., hydrophobic interactions and hydrogen bonding) between DOM and membrane might play important roles in UF membrane fouling, especially for small sized DOM molecules. Based on the molecular level composition determined by FT-ICR-MS, the CHOS formula group showed a greater removal tendency toward the HPO membrane, while the CHONS group was prone to be removed by the HPI membrane. The changes in the overall molecular composition of DOM upon UF filtration were highly dependent on the sources of DOM. The molecules of more acidic nature tended to remain in the permeate of effluent DOM, while the river DOM was shifted into more nitrogen-enriched composition after filtration. Regardless of the DOM sources, the HPO membrane with a smaller pore size led to the most pronounced changes in the molecular composition of DOM. Copyright © 2018 Elsevier Ltd. All rights reserved.

Urbanization and agriculture increase exports and differentially alter elemental stoichiometry of dissolved organic matter (DOM) from tropical catchments.

PubMed

Gücker, Björn; Silva, Ricky C S; Graeber, Daniel; Monteiro, José A F; Boëchat, Iola G

2016-04-15

Many tropical biomes are threatened by rapid land-use change, but its catchment-wide biogeochemical effects are poorly understood. The few previous studies on DOM in tropical catchments suggest that deforestation and subsequent land use increase stream water dissolved organic carbon (DOC) concentrations, but consistent effects on DOM elemental stoichiometry have not yet been reported. Here, we studied stream water DOC concentrations, catchment DOC exports, and DOM elemental stoichiometry in 20 tropical catchments at the Cerrado-Atlantic rainforest transition, dominated by natural vegetation, pasture, intensive agriculture, and urban land cover. Streams draining pasture could be distinguished from those draining natural catchments by their lower DOC concentrations, with lower DOM C:N and C:P ratios. Catchments with intensive agriculture had higher DOC exports and lower DOM C:P ratios than natural catchments. Finally, with the highest DOC concentrations and exports, as well as the highest DOM C:P and N:P ratios, but the lowest C:N ratios among all land-use types, urbanized catchments had the strongest effects on catchment DOM. Thus, urbanization may have alleviated N limitation of heterotrophic DOM decomposition, but increased P limitation. Land use-especially urbanization-also affected the seasonality of catchment biogeochemistry. While natural catchments exhibited high DOC exports and concentrations, with high DOM C:P ratios in the rainy season only, urbanized catchments had high values in these variables throughout the year. Our results suggest that urbanization and pastoral land use exerted the strongest impacts on DOM biogeochemistry in the investigated tropical catchments and should thus be important targets for management and mitigation efforts. Copyright © 2016 Elsevier B.V. All rights reserved.

Revealing Sources and Distribution Changes of Dissolved Organic Matter (DOM) in Pore Water of Sediment from the Yangtze Estuary

PubMed Central

Wang, Ying; Zhang, Di; Shen, Zhenyao; Feng, Chenghong; Chen, Jing

2013-01-01

Dissolved organic matter (DOM) in sediment pore waters from Yangtze estuary of China based on abundance, UV absorbance, molecular weight distribution and fluorescence were investigated using a combination of various parameters of DOM as well as 3D fluorescence excitation emission matrix spectra (F-EEMS) with the parallel factor and principal component analysis (PARAFAC-PCA). The results indicated that DOM in pore water of Yangtze estuary was very variable which mainly composed of low aromaticity and molecular weight materials. Three humic-like substances (C1, C2, C4) and one protein-like substance (C3) were identified by PARAFAC model. C1, C2 and C4 exhibited same trends and were very similar. The separation of samples on both axes of the PCA showed the difference in DOM properties. C1, C2 and C4 concurrently showed higher positive factor 1 loadings, while C3 showed highly positive factor 2 loadings. The PCA analysis showed a combination contribution of microbial DOM signal and terrestrial DOM signal in the Yangtze estuary. Higher and more variable DOM abundance, aromaticity and molecular weight of surface sediment pore water DOM can be found in the southern nearshore than the other regions primarily due to the influence of frequent and intensive human activities and tributaries inflow in this area. The DOM abundance, aromaticity, molecular weight and fluorescence intensity in core of different depth were relative constant and increased gradually with depth. DOM in core was mainly composed of humic-like material, which was due to higher release of the sedimentary organic material into the porewater during early diagenesis. PMID:24155904

Characterization of spectral responses of dissolved organic matter (DOM) for atrazine binding during the sorption process onto black soil.

PubMed

Wang, Yifan; Zhang, Xinyuan; Zhang, Xing; Meng, Qingjuan; Gao, Fengjie; Zhang, Ying

2017-08-01

This study was aim to investigate the interaction between soil-derived dissolved organic matter (DOM) and atrazine as a kind of pesticides during the sorption process onto black soil. According to the experimental data, the adsorption capacity of Soil + DOM, Soil and DOM were 41.80, 31.45 and 9.35 mg kg -1 , separately, which indicated that DOM significantly enhanced the adsorption efficiency of atrazine by soil. Data implied that the pseudo-second-order kinetic equation could well explain the adsorption process. The adsorption isotherms (R 2  > 0.99) had a satisfactory fit in both Langmuir and Freundlich models. Three-dimensional excitation-emission matrix (3D-EEM), synchronous fluorescence, two-dimensional correlation spectroscopy (2D-COS) and Fourier transform infrared spectroscopy (FT-IR) were selected to analyze the interaction between DOM and atrazine. 3D-EEM showed that humic acid-like substances were the main component of DOM. The fluorescence of DOM samples were gradually quenched with the increased of atrazine concentrations. Synchronous fluorescence spectra showed that static fluorescence quenching was the main quenching process. 2D-COS indicated that the order of the spectral changes were as following: 336 nm > 282 nm. Furthermore, the fluorescence quenching of humic-like fraction occurred earlier than that of protein-like fraction under atrazine surroundings. FT-IR spectra indicated that main compositions of soil DOM include proteins, polysaccharides and humic substances. The findings of this study are significant to reveal DOM played an important role in the environmental fate of pesticides during sorption process onto black soil and also provide more useful information for understanding the interaction between DOM and pesticides by using spectral responses. Copyright © 2017. Published by Elsevier Ltd.

Characterization of binding site heterogeneity for copper within dissolved organic matter fractions using two-dimensional correlation fluorescence spectroscopy.

PubMed

Hur, Jin; Lee, Bo-Mi

2011-06-01

The heterogeneity of copper binding characteristics for dissolved organic matter (DOM) fractions was investigated based on the fluorescence quenching of the synchronous fluorescence spectra upon the addition of copper and two-dimensional correlation spectroscopy (2D-COS). Hydrophobic acid (HoA) and hydrophilic (Hi) fractions of two different DOM (algal and leaf litter DOM) were used for this study. For both DOM, fluorescence quenching occurred at a wider range of wavelengths for the HoA fractions compared to the Hi fractions. The combined information of the synchronous and asynchronous maps derived from 2D-COS provided a clear picture of the heterogeneous distribution of the copper binding sites within each DOM fraction, which was not readily recognized by a simple comparison of the changes in the synchronous fluorescence spectra upon the addition of copper. For the algal DOM, higher stability constants were exhibited for the HoA versus the Hi fractions. The logarithms of the stability constants ranged from 4.8 to 6.1 and from 4.5 to 5.0 for the HoA and the Hi fractions of the algal DOM, respectively, depending on the associated wavelength and the fitted models. In contrast, no distinctive difference in the binding characteristics was found between the two fractions of the leaf litter DOM. This suggests that influences of the structural and chemical properties of DOM on copper binding may differ for DOM from different sources. The relative difference of the calculated stability constants within the DOM fractions were consistent with the sequential orders interpreted from the asynchronous 2D-COS. It is expected that 2D-COS will be widely applied to other DOM studies requiring detailed information on the heterogeneous nature and subsequent effects under a range of environmental conditions. Copyright © 2011 Elsevier Ltd. All rights reserved.

Diurnal variability in riverine dissolved organic matter composition determined by in situ optical measurement in the San Joaquin River (California, USA)

USGS Publications Warehouse

Spencer, R.G.M.; Pellerin, B.A.; Bergamaschi, B.A.; Downing, B.D.; Kraus, T.E.C.; Smart, D.R.; Dahlgren, R.A.; Hernes, P.J.

2007-01-01

Dissolved organic matter (DOM) concentration and composition in riverine and stream systems are known to vary with hydrological and productivity cycles over the annual and interannual time scales. Rivers are commonly perceived as homogeneous with respect to DOM concentration and composition, particularly under steady flow conditions over short time periods. However, few studies have evaluated the impact of short term variability ( < 1 day) on DOM dynamics. This study examined whether diurnal processes measurably altered DOM concentration and composition in the hypereutrophic San Joaquin River (California) during a relatively quiescent period. We evaluated the efficacy of using optical in situ measurements to reveal changes in DOM which may not be evident from bulk dissolved organic carbon (DOC) measurement alone. The in situ optical measurements described in this study clearly showed for the first time diurnal variations in DOM measurements, which have previously been related to both composition and concentration, even though diurnal changes were not well reflected in bulk DOC concentrations. An apparent asynchronous trend of DOM absorbance and chlorophyll-a in comparison to chromophoric dissolved organic matter (CDOM) fluorescence and spectral slope S290-350 suggests that no one specific CDOM spectrophotometric measurement explains absolutely DOM diurnal variation in this system; the measurement of multiple optical parameters is therefore recommended. The observed diurnal changes in DOM composition, measured by in situ optical instrumentation likely reflect both photochemical and biologically-mediated processes. The results of this study highlight that short-term variability in DOM composition may complicate trends for studies aiming to distinguish different DOM sources in riverine systems and emphasizes the importance of sampling specific study sites to be compared at the same time of day. The utilization of in situ optical technology allows short-term variability in DOM dynamics to be monitored and serves to increase our understanding of its processing and fundamental role in the aquatic environment. Copyright ?? 2007 John Wiley & Sons, Ltd.

Understanding microbial/DOM interactions using fluorescence and flow cytometry

NASA Astrophysics Data System (ADS)

Fox, Bethany; Rushworth, Cathy; Attridge, John; Anesio, Alexandre; Cox, Tim; Reynolds, Darren

2015-04-01

The transformation and movement of dissolved organic carbon (DOC) within freshwater aquatic systems is an important factor in the global cycling of carbon. DOC within aquatic systems is known to underpin the microbial food web and therefore plays an essential role in supporting and maintaining the aquatic ecosystem. Despite this the interactions between bacteria and dissolved organic matter (DOM) are not well understood, although the literature indicates that the microbial processing of bioavailable DOM is essential during the production of autochthonous, labile, DOM. DOM can be broadly characterised by its fluorescing properties and Coble et al. (2014) define terrestrially derived DOM as exhibiting "peak C" fluorescence, whilst labile microbially derived DOM is defined as showing "peak T" fluorescence. Our work explores the microbial/DOM interactions by analysing aquatic samples using fluorescence excitation and emission matrices (EEMs) in conjunction with microbial consumption of dissolved oxygen. Environmental and synthetic water samples were subjected to fluorescence characterisation using both fluorescence spectroscopy and in situ fluorescence sensors (Chelsea Technologies Group Ltd.). PARAFAC analysis and peak picking were performed on EEMs and compared with flow cytometry data, used to quantify bacterial numbers present within samples. Synthetic samples were created using glucose, glutamic acid, nutrient-rich water and a standard bacterial seed. Synthetic samples were provided with terrestrially derived DOM via the addition of an aliquot of environmental water. Using a closed system approach, samples were incubated over time (up to a maximum of 20 days) and analysed at pre-defined intervals. The main focus of our work is to improve our understanding of microbial/DOM interactions and how these interactions affect both the DOM characteristics and microbial food web in freshwater aquatic systems. The information gained, in relation to the origin, microbial processing and subsequent production of DOM, will inform the development of a new generation of in situ fluorescence sensors. Ultimately, our aim is develop a novel technology that enables the monitoring of ecosystem health in freshwater aquatic systems.

Photochemical reactivities of dissolved organic matter (DOM) in a sub-alpine lake revealed by EEM-PARAFAC: An insight into the fate of allochthonous DOM in alpine lakes affected by climate change.

PubMed

Du, Yingxun; Zhang, Yuanyuan; Chen, Feizhou; Chang, Yuguang; Liu, Zhengwen

2016-10-15

Due to climate change, tree line advance is occurring in many alpine regions. Within the next 50 to 100years, alpine lake catchments are expected to develop increased vegetation cover similar to that of sub-alpine lake catchments which currently exist below the tree line. Such changes in vegetation could trigger increased allochthonous DOM inputs to alpine lakes. To understand the fate of allochthonous DOM in alpine lakes impacted by climate change, the photochemical reactivity of DOM in sub-alpine Lake Tiancai (located 200m below the tree line) was investigated by excitation emission matrix fluorescence combined with parallel factor analysis (EEM-PARAFAC) and UV-Vis spectra analysis. With photo-exposure, a decrease in apparent DOM molecular weight was observed and 32% DOM was photomineralized to CO2. Interestingly, the aromaticity of DOM increased after photodegradation, as evidenced by increases in both the specific UV absorbance at 254nm (SUVA254) and the humification index (HIX). Five EEM-PARAFAC components were identified, including four terrestrially-derived substances (C1, C2, C3 and C4; allochthonous) and one tryptophan-like substance (C5; autochthonous). Generally, allochthonous DOM represented by C2 and C3 exhibited greater photoreactivity than autochthonous DOM represented by C5. C4 was identified as a possible photoproduct with relatively high aromaticity and photorefractive tendencies and contributed to the observed increase in SUVA254 and HIX. UV light facilitated the photodegradation of DOM and had the greatest effect on the removal of C3. This study provides information on the transformation of EEM-PARAFAC components in a sub-alpine lake, which is important in understanding the fate of increased allochthonous DOM inputs to alpine lakes impacted by climate change. Copyright © 2016 Elsevier B.V. All rights reserved.

Molecular characteristics of continuously released DOM during one year of root and leaf litter decomposition

NASA Astrophysics Data System (ADS)

Altmann, Jens; Jansen, Boris; Kalbitz, Karsten; Filley, Timothy

2013-04-01

Dissolved organic matter (DOM) is one of the most dynamic carbon pools linking the terrestrial with the aquatic carbon cycle. Besides the insecure contribution of terrestrial DOM to the greenhouse effect, DOM also plays an important role for the mobility and availability of heavy metals and organic pollutants in soils. These processes depend very much on the molecular characteristics of the DOM. Surprisingly the processes that determine the molecular composition of DOM are only poorly understood. DOM can originate from various sources, which influence its molecular composition. It has been recognized that DOM formation is not a static process and DOM characteristics vary not only between different carbon sources. However, molecular characteristics of DOM extracts have scarcely been studied continuously over a longer period of time. Due to constant molecular changes of the parent litter material or soil organic matter during microbial degradation, we assumed that also the molecular characteristics of litter derived DOM varies at different stages during root and needle decomposition. For this study we analyzed the chemical composition of root and leaf samples of 6 temperate tree species during one year of litter decomposition in a laboratory incubation. During this long-term experiment we measured continuously carbon and nitrogen contents of the water extracts and the remaining residues, C mineralization rates, and the chemical composition of water extracts and residues by Curie-point pyrolysis mass spectrometry with TMAH We focused on the following questions: (I) How mobile are molecules derived from plant polymers like tannin, lignin, suberin and cutin? (II) How does the composition of root and leaf derived DOM change over time in dependence on the stage of decomposition and species? Litter derived DOM was generally dominated by aromatic compounds. Substituded fatty acids as typically cutin or suberin derived were not detected in the water extracts. Fresh leaf and needle samples released a much higher amount of tannins than fresh root samples. At later litter decomposition stages the influence of tannins decreased and lignin derived phenols dominated the extracts. With ongoing litter degradation the degree of oxidation for the litter material increased, which was also reflected by the water extracted molecules.

Molecular signatures of biogeochemical transformations in dissolved organic matter from ten World Rivers

NASA Astrophysics Data System (ADS)

Riedel, Thomas; Zark, Maren; Vähätalo, Anssi; Niggemann, Jutta; Spencer, Robert; Hernes, Peter; Dittmar, Thorsten

2016-09-01

Rivers carry large amounts of dissolved organic matter (DOM) to the oceans thereby connecting terrestrial and marine element cycles. Photo-degradation in conjunction with microbial turnover is considered a major pathway by which terrigenous DOM is decomposed. To reveal globally relevant patterns behind this process, we performed photo-degradation experiments and year-long bio-assays on DOM from ten of the largest world rivers that collectively account for more than one-third of the fresh water discharge to the global ocean. We furthermore tested the hypothesis that the terrigenous component in deep ocean DOM may be far higher than biomarker studies suggest, because of the selective photochemical destruction of characteristic biomolecules from vascular plants. DOM was molecularly characterized by a combination of non-targeted ultrahigh-resolution mass spectrometry and quantitative molecular tracer analyses. We show that the reactivity of DOM is globally related to broad catchment properties. Basins that are dominated by forest and grassland export more photo-degradable DOM than other rivers. Chromophoric compounds are mainly vascular plant-derived polyphenols, and partially carry a pyrogenic signature from vegetation fires. These forest and grassland dominated rivers lost up to 50% of dissolved organic carbon (DOC) during irradiation, and up to 85% of DOC was lost in total if subsequently bio-incubated for one year. Basins covered by cropland, on the other hand, export DOM with a higher proportion of photo-resistant and bio-available DOM which is enriched in nitrogen. In these rivers, 30% or less of DOC was photodegraded. Consistent with previous studies, we found that riverine DOM resembled marine DOM in its broad molecular composition after extensive degradation, mainly due to almost complete removal of aromatics. More detailed molecular fingerprinting analysis (based on the relative abundance of >4000 DOM molecular formulae), however, revealed clear differences between degraded riverine and deep-sea DOM (molecular Bray-Curtis dissimilarity of 50%). None of our experimental treatments enhanced the molecular similarity between the rivers and the deep ocean. We conclude that terrigenous DOM retains a specific molecular signature during photo-degradation on much longer time scales than previously assumed and that substantial, thus far unknown, molecular transformations occur prior to downward convection into the deep oceanic basins.

Design, fabrication, and testing of nanostructured carbons and composites

NASA Astrophysics Data System (ADS)

Wang, Zhiyong

Many applications, such as catalysis, sensing, separation and energy storage and conversion, will benefit from the miniaturization of materials to nanometer length scales. This dissertation details my study of nanocomposites based on three-dimensionally ordered macroporous (3DOM) carbons and zirconia, and three-dimensionally ordered macroporous/mesoporous (3DOM/m) carbons. The macropores of these materials were produced using colloidal crystal templates while the mesopores were generated using surfactant templates. These solids are composed of close-packed and three-dimensionally interconnected spherical macropores surrounded by nanoscale solid or mesoporous wall skeletons. This unique architecture offers large surface areas, pore volumes, and good access into the bulk via a macroporous network. 3DOM carbons have been demonstrated as promising electrode materials for lithium ion batteries and sensors, but their electrochemical performance still needs to be improved. As a model system for the modification of the electrode, 3DOM C/TiO2 was synthesized by fabricating a conformal coating of TiO2 nanoparticles on the macropore walls of 3DOM C. My research further extended the micro-structural design of monolithic carbon from 3DOM to 3DOM/m. 3DOM/m C monoliths with high surface areas, controllable mesopore sizes, and mesopore ordering, were synthesized by three methods. One of the methods is simpler and more environment benign than previously reported methods. The mesopores in 3DOM/m C-based electrode provide room to accommodate secondary phases, such as graphitic carbon, SnO2 and Si which can improve the conductivity or lithium capacity of the electrode. Owing to this advantage, 3DOM/m C/C and 3DOM/m C/SnO2 exhibited significantly improved rate performance, lithium capacity and cycleability, compared with 3DOM C. To meet the demands of nano-sized functional materials in applications such as nano-device fabrication and drug delivery, mesoporous carbon nanoparticles with cubic, spherical and tetrapod shapes were also synthesized. In addition, new methods were developed to assemble nanocomposites of bifunctional catalyst components. These materials were designed for the potential direct conversion of synthesis gas to clean liquid fuels. Coatings of zeolite and cobalt nanoparticles were fabricated on 3DOM promoted zirconia. The 3DOM zirconia-based nanocomposites were characterized by a wide variety of techniques to illustrate their morphologies, internal structures, chemical compositions, porosity, and crystallographic phases.

Lu-Hf Garnet Geochronology Reveals the Tectonic History of Precambrian Rocks in the Southern Rocky Mountains

NASA Astrophysics Data System (ADS)

Aronoff, R.; Andronicos, C.; Vervoort, J. D.; Hunter, R. A.

2014-12-01

Lu-Hf garnet dating of Proterozoic rocks of the southwestern United States provides constraints on the timing and geographic extent of metamorphism associated with the Yavapai, Mazatzal, and newly recognized Picuris orogenies. Prior work focusing on U-Pb dating of plutons and Ar geochronology has left the timing of prograde metamorphism ambiguous, particularly in northern New Mexico and southern Colorado. Because the Lu-Hf system dates the onset of garnet growth, it can constrain the timing of the prograde P-T path. Garnet schist samples from central and northern New Mexico exhibit garnet growth restricted to the time period between ~1460 and 1400 Ma. In the Picuris and Manzano mountains, the oldest Lu-Hf garnet ages predate the U-Pb ages of ~1.4 Ga plutons located near the dated samples. This implies that garnet growth, and therefore the onset of amphibolite facies metamorphism, cannot be driven by contact metamorphism, as has been previously inferred. Garnet-bearing samples from the Needle and Wet Mountains in southern Colorado display a range of garnet ages between ~1750 and 1470 Ma. A garnet gneiss from the Needle Mountains in southwestern Colorado yields an age of 1748 Ma, which is consistent with the Yavapai orogeny. This Lu-Hf garnet age has not been reset by contact metamorphism associated with the emplacement of the ~1.4 Ga Eolus batholith. Anatectic garnet in an orthogneiss from the northern Wet Mountains yields an age of 1601 Ma and is interpreted to date partial melting at the close of the Mazatzal orogeny. A 1476 Ma garnet age from the aureole of the 1440 Ma Oak Creek pluton is interpreted to date upper amphibolite facies metamorphism. The age distribution of these samples shows that rocks in Colorado underwent a complex, poly-metamorphic history, while rocks in New Mexico underwent a single progressive metamorphic event. This contrast implies that the boundary between rocks deformed and metamorphosed during the ~1800-1600 Ma Yavapai and Mazatzal orogenies and those only deformed and metamorphosed during the ~1460-1400 Ma Picuris orogeny lies in northern New Mexico, along what has previously been considered the Mazatzal front. By using Lu-Hf geochronology to directly date a rock-forming mineral, we are better able to reconstruct the tectonic history of this region.

Diverging Histories of the Liberty Creek and Iceberg Lake Blueschist Bodies, south central Alaska

NASA Astrophysics Data System (ADS)

Day, E. M.; Pavlis, T. L.; Amato, J. M.

2011-12-01

New studies of the Liberty Creek and Iceberg Lake blueschist bodies of south central Alaska indicate that despite structural similarities, these blueschist bodies are derived from a different protolith and were metamorphosed to blueschist facies at distinctly different times. Both blueschists are located just south of the Border Ranges Fault (BRF) within outcrop belts of the McHugh Complex, a low-grade mélange assemblage that is now known from detrital zircon studies to consist of two distinct assemblages: a Jurassic to Earliest Cretaceous assemblage and a Late Cretaceous assemblage. The BRF is a megathrust system that represents the Late Triassic-Early Jurassic initiation of southern Alaskan subduction. Large scale (1:24,000) mapping revealed similar fabric overprint histories, epitomized by a previously undescribed youngest vertical N-S trending crenulation cleavage in both blueschist bodies which implies a structural correlation despite their separation of ~100 kilometers along strike. Despite structural similarities detrital zircon studies show that the Liberty Creek and Iceberg Lake blueschists do not have a similar maximum age of deposition. Thirteen samples from the Iceberg Lake blueschist were processed, none of which produced detrital zircons. Samples from the McHugh Complex greenschists that surround the Iceberg Lake blueschist produced numerous zircons indicating a Late Jurassic (~160 Ma) maximum age of deposition. Three out of sixteen samples from the Liberty creek blueschist produced detrital zircons indicating maximum depositional ages ranging from Late Jurassic (~160.1 Ma, n=64 grains; ~152.25 Ma, n=68 grains) to Early Cretaceous (~137.1 Ma, n=95 grains). The Late Jurassic dates are consistent with maximum depositional ages determined by Amato and Pavlis (2010) for McHugh Complex rocks along Turnagain Arm near Anchorage, AK. Sisson and Onstott (1986) reported a metamorphic cooling age of 185 Ma for the Iceberg Lake blueschist, thus, although no depostitional age constraints were obtained for the Iceberg Lake body, its metamorphic cooling age is far older than the younger depositional ages of the Liberty Creek blueschists indicating these areas record two different blueschist facies metamorphic assemblages. Work in progress on cooling ages from the Liberty Creek rocks should clarify the age of this younger metamorphism. Although these assemblages record different metamorphic events, the similar overprint history may indicate that the Liberty Creek and Iceberg Lake blueschists were subjected to the same, younger deformation series, possibly Cenozoic strike-slip related deformation.

The Relationship Between Dissolved Organic Matter Composition and Organic Matter Optical Properties in Freshwaters

NASA Astrophysics Data System (ADS)

Aiken, G.; Spencer, R. G.; Butler, K.

2010-12-01

Dissolved organic matter (DOM) chemistry and flux are potentially useful, albeit, underutilized, indicators of watershed characteristics, climate influences on watershed hydrology and soils, and changes associated with resource management. Source materials, watershed geochemistry, oxidative processes and hydrology exert strong influences on the nature and reactivity of DOM in aquatic systems. The molecules that comprise DOM, in turn, control a number of environmental processes important for ecosystem function including light penetration and photochemistry, microbial activity, mineral dissolution/precipitation, and the transport and reactivity of hydrophobic compounds and metals (e.g. Hg). In particular, aromatic molecules derived from higher plants exert strong controls on aquatic photochemistry, and on the transport and biogeochemistry of metals. Assessment of DOM composition and transport, therefore, can provide a basis for understanding watershed processes and biogeochemistry of rivers and streams. Here we present results of multi-year studies designed to assess the seasonal and spatial variability of DOM quantity and quality for 57 North American Rivers. DOM concentrations and composition, based on DOM fractionation on XAD resins, ultraviolet (UV)/visible absorption and fluorescence spectroscopic analyses, and specific compound analyses, varied greatly both between sites and seasonally within a given site. DOM in these rivers exhibited a wide range of concentration (<80 to >4000 µM C* L-1) and specific ultra-violet absorbance at 254 nm (SUVA254) (0.6 to 5 L *mg C-1 *m-1), an optical measurement that is an indicator of aromatic carbon content. In almost all systems, UV absorbance measured at specific wavelengths (e.g. 254 nm) correlated strongly with DOM and hydrophobic organic acid (HPOA) content (aquatic humic substances). The relationships between dissolved organic carbon (DOC) concentration and absorbance for the range of systems were quite variable due to variation in the fraction of non-chromophoric DOM. However, the relationship between HPOA content and UV absorbance was stronger and more consistent because the HPOA fraction contains a greater percentage of UV absorbing compounds than other fractions of the DOM. These results demonstrate that optical properties, such as UV absorbance, are excellent proxies for DOC and HPOA concentrations within a given system. For a limited set of samples, we observed that optical measurements were strongly correlated with lignin phenols, a biomarker indicative of higher plant sources of DOM, and with Hg, which interacts strongly with DOM. Optical measurements are relatively inexpensive to obtain, provide critical information related to DOM composition and reactivity, and can be measured in situ. When combined with discharge data, optical measurements allow estimation of both DOM flux and reactivity in streams and rivers. The link between the nature and reactivity of DOM and its optical properties can be exploited to provide powerful monitoring tools to assess the impacts of climate change and management practices on overall water quality, on DOM transport and transformation, and on the transport of other chemical constituents of interest.

Distribution of Aliphatic Amines in CO, CV, and CK Carbonaceous Chondrites and Relation to Mineralogy and Processing History

NASA Technical Reports Server (NTRS)

Aponte, Jose C.; Abreu, Neyda M.; Glavin, Daniel P.; Dworkin, Jason P.; Elsila, Jamie E.

2017-01-01

The analysis of water-soluble organic compounds in meteorites provides valuable insights into the prebiotic synthesis of organic matter and the processes that occurred during the formation of the solar system. We investigated the concentration of aliphatic monoamines present in hot acid water extracts of the unaltered Antarctic carbonaceous chondrites, Dominion Range (DOM) 08006 (CO3) and Miller Range (MIL) 05013 (CO3), and the thermally altered meteorites, Allende (CV3), LAP 02206 (CV3), GRA 06101 (CV3), Allan Hills (ALH) 85002 (CK4), and EET 92002 (CK5). We have also reviewed and assessed the petrologic characteristics of the meteorites studied here to evaluate the effects of asteroidal processing on the abundance and molecular distributions of monoamines. The CO3, CV3, CK4, and CK5 meteorites studied here contain total concentrations of amines ranging from 1.2 to 4.0 nmol/g of meteorite; these amounts are 1-3 orders of magnitude below those observed in carbonaceous chondrites from the CI, CM, and CR groups. The low-amine abundances for CV and CK chondrites may be related to their extensive degree of thermal metamorphism and/or to their low original amine content. Although the CO3 meteorites, DOM 08006 and MIL 05013, do not show signs of thermal and aqueous alteration, their monoamine contents are comparable to those observed in moderately/extensively thermally altered CV3, CK4, and CK5 carbonaceous chondrites. The low content of monoamines in pristine CO carbonaceous chondrites suggests that the initial amounts, and not asteroidal processes, play a dominant role in the content of monoamines in carbonaceous chondrites. The primary monoamines, methylamine, ethylamine, and n-propylamine constitute the most abundant amines in the CO3, CV3, CK4, and CK5 meteorites studied here. Contrary to the predominance of n-x-amino acid isomers in CO3 and thermally altered meteorites, there appears to be no preference for the larger n-amines.

The clumped-isotope geochemistry of exhumed marbles from Naxos, Greece

NASA Astrophysics Data System (ADS)

Ryb, U.; Lloyd, M. K.; Stolper, D. A.; Eiler, J. M.

2017-07-01

Exhumation and accompanying retrograde metamorphism alter the compositions and textures of metamorphic rocks through deformation, mineral-mineral reactions, water-rock reactions, and diffusion-controlled intra- and inter-mineral atomic mobility. Here, we demonstrate that these processes are recorded in the clumped- and single-isotope (δ13 C and δ18 O) compositions of marbles, which can be used to constrain retrograde metamorphic histories. We collected 27 calcite and dolomite marbles along a transect from the rim to the center of the metamorphic core-complex of Naxos (Greece), and analyzed their carbonate single- and clumped-isotope compositions. The majority of Δ47 values of whole-rock samples are consistent with exhumation- controlled cooling of the metamorphic complex. However, the data also reveal that water-rock interaction, deformation driven recrystallization and thermal shock associated with hydrothermal alteration may considerably impact the overall distribution of Δ47 values. We analyzed specific carbonate fabrics influenced by deformation and fluid-rock reaction to study how these processes register in the carbonate clumped-isotope system. Δ47 values of domains drilled from a calcite marble show a bimodal distribution. Low Δ47 values correspond to an apparent temperature of 260 °C and are common in static fabrics; high Δ47 values correspond to an apparent temperature of 200 °C and are common in dynamically recrystallized fabrics. We suggest that the low Δ47 values reflect diffusion-controlled isotopic reordering during cooling, whereas high Δ47 values reflect isotopic reordering driven by dynamic recrystallization. We further studied the mechanism by which dynamic recrystallization may alter Δ47 values by controlled heating experiments. Results show no significant difference between laboratory reactions rates in the static and dynamic fabrics, consistent with a mineral-extrinsic mechanism, in which slip along crystal planes was associated with atomic-scale isotopic reordering in the calcite lattice. An intrinsic mechanism (enhanced isotopic reordering rate in deformed minerals) is contraindicated by these experiments. We suggest that Δ47 values of dynamically recrystallized fabrics that form below the diffusion-controlled blocking-temperature for calcite constrain the temperature of deformation. We find that Δ47-based temperatures of static fabrics from Naxos marbles are ∼60-80 °C higher than commonly observed in slowly cooled metamorphic rocks, and would suggest cooling rates of ∼105 °CMyr-1. A similar thermal history is inferred for dolomite marbles from the core vicinity, which preserve apparent temperatures up to 200 °C higher than a typical blocking temperature (∼300 °C). This finding could be explained by a hydrothermal event driving a brief thermal pulse and locally resetting Δ47 values. Rapid cooling of the core-complex region is consistent with a compilation of published cooling ages and a new apatite U-Th/He age, associating the thermal event with the emplacement of a granodiorite pluton at ∼12 Ma.

Extension Within The Australia-Eurasia Collision: The Metamorphic Rocks Of Central Sulawesi, Indonesia

NASA Astrophysics Data System (ADS)

Watkinson, I. M.; Hall, R.; Hennig, J.; Forster, M.

2012-12-01

Low-angle mylonitic fabrics from the metamorphic basement of central Sulawesi reveal a complex history of extension from the late Miocene to the present-day. Sulawesi is situated in the convergent triple junction between the Australian, Eurasian and Philippine Sea plates. The island is cut by the Palu-Koro and Matano faults, major active strike-slip zones that were initiated no earlier than about 5 Ma and have previously been attributed to collision-related processes. Within, and to the north and east of the strike-slip faults, are a suite of metamorphic complexes that include mica schists, schistose amphibolites, gneisses, migmatites, granulites, eclogites, marbles and ultramafic rocks including garnet peridotites. Mylonitic fabrics are widespread throughout the metamorphic rocks. The orientation of the mylonitic foliation is highly variable but typically dips less than 30°. Kinematic indicators record transport directions dominantly between top-to-the-NW and top-to-the-NE. Medium to high-grade mylonites, particularly in the south and west, are associated with ductile boudinage of eclogite and kyanite-bearing layers, 'snowball' garnet porphyroclasts, dynamic recrystallisation of feldspar and amphibole, and mylonitic deformation was locally synchronous with partial melting. Medium to high-grade mylonites are commonly overprinted by isoclinal asymmetric similar folds. Low grade mylonites are characterised by quartz recrystallisation only. Mica growth during mylonitic deformation is recorded by young 40Ar-39Ar plateaux between 5.05 ± 0.01 Ma and 2.07 ± 0.03 Ma in the west and 11.33 ± 0.02 Ma in the east. Undeformed aplitic dykes of similar composition to the migmatite leucosomes locally cross-cut the migmatitic mylonites and have yielded a biotite 40Ar-39Ar plateau of 3.62 ± 0.02 Ma. In the east the mylonitic fabric is cut by a low-angle detachment surface expressed as anomalously corrugated topography. On the basis of lithologic variation, shear-sense directions, 40Ar-39Ar ages and topographic character it is possible to divide the central Sulawesi metamorphic complexes into a series of low-angle ductile shear zones, cut by an upper brittle detachment in the east which may still be active. Uplift of the metamorphic rocks has been largely in response to sequential unroofing along these structures. The system is bounded in the west by the Palu-Koro Fault, which links to subduction beneath north Sulawesi, and which may flatten at depth into a basal detachment below central Sulawesi. Early extension is synchronous with spreading in the North Banda Sea, and may have been driven by east-directed rollback of the Banda Sea. Later extension (post-5 Ma) was driven by subduction rollback in the north, and much of the extensional deformation in central Sulawesi represents the crustal 'tear' marking the southern limit of the effects of northward extension.

Pre-Alpine evolution of the Seckau Complex (Austroalpine basement/Eastern Alps): Constraints from in-situ LA-ICP-MS Usbnd Pb zircon geochronology

NASA Astrophysics Data System (ADS)

Mandl, Magdalena; Kurz, Walter; Hauzenberger, Christoph; Fritz, Harald; Klötzli, Urs; Schuster, Ralf

2018-01-01

The Variscan European Belt is a complex orogen with its southern margin partly obscured by Alpine tectonics and metamorphism. We present a study of one of the units, the Seckau Complex, that constitute the southern part of the Variscan European Belt in the Eastern Alps in order to clarify its origin, age and lithostratigraphy. The magmatic and geochronological evolution of this Complex in the northwestern part of the Seckau Nappe (as part of the Austroalpine Silvretta-Seckau Nappe System) was investigated by zircon Usbnd Pb dating of paragneisses and metagranitoids coupled with petrological and geochemical data. This reveals the distinction of three newly defined lithostratigraphic/lithodemic sub-units: (1) Glaneck Metamorphic Suite, (2) Hochreichart Plutonic Suite and (3) Hintertal Plutonic Suite. The Glaneck Metamorphic Suite is mainly composed of fine-grained paragneisses that yield Usbnd Pb zircon ages in the range between 2.7 Ga and 2.0 Ga, as well as concordia ages from 572 ± 7 Ma to 559 ± 11 Ma. All of these ages are interpreted as detrital zircon ages originating from an igneous source. The paragneisses are the host rock for the large volumes of metagranitoids of the Hochreichart Plutonic Suite and the Hintertal Plutonic Suite. The Hochreichart Plutonic Suite comprises highly fractionated melts with mainly S-type characteristics and late Cambrian to Early Ordovician Usbnd Pb zircon ages (508 ± 9 Ma to 486 ± 9 Ma), interpreted as magmatic protolith ages. The Hintertal Plutonic Suite is composed of metagranitoids with Late Devonian to early Carboniferous (365 ± 11 Ma and 331 ± 10 Ma) protolith ages, that intruded during an early phase of the Variscan tectonometamorphic event. The metagranitoids of the Hintertal Plutonic Suites define a magmatic fractionation trend, seen in variable Rb/Sr ratios. On this base they can be further subdivided into (a) the Griessstein Pluton characterized by S-type metagranitoids and (b) the Pletzen Pluton distinguished by intermediate to acidic metagranitoids with I-type affinity. The detrital zircon age spectra suggest a Neoproterozoic ancestry of the Glaneck Metamorphic Suite, which was located west of the Arabian Nubian Shield, probably next to the Trans-Saharan Belt. The early Paleozoic evolution of the recent Seckau Complex shows similarities to basement units of the Southalpine Unit, parts of the Austroalpine Unit and the Tatric and Veporic units of the Central Western Carpathians.

Paleoproterozoic high-pressure metamorphism in the northern North China Craton and implications for the Nuna supercontinent

PubMed Central

Wan, Bo; Windley, Brian F.; Xiao, Wenjiao; Feng, Jianyun; Zhang, Ji'en

2015-01-01

The connection between the North China Craton (NCC) and contiguous cratons is important for the configuration of the Nuna supercontinent. Here we document a new Paleoproterozoic high-pressure (HP) complex dominated by garnet websterite on the northern margin of the NCC. The peak metamorphism of the garnet websterite was after ∼1.90 Ga when it was subducted to eclogite facies at ∼2.4 GPa, then exhumed back to granulite facies at ∼0.9 GPa before ∼1.82 Ga. The rock associations with their structural relationships and geochemical affinities are comparable to those of supra-subduction zone ophiolites, and supported by subduction-related signatures of gabbros and basalts. We propose that a ∼1.90 Ga oceanic fragment was subducted and exhumed into an accretionary complex along the northern margin of the NCC. Presence of the coeval Sharyzhalgai complex with comparable HP garnet websterites in the southern Siberian active margin favours juxtaposition against the NCC in the Paleoproterozoic. PMID:26388458

High soil solution carbon and nitrogen concentrations in a drained Atlantic bog are reduced to natural levels by 10 years of rewetting

NASA Astrophysics Data System (ADS)

Frank, S.; Tiemeyer, B.; Gelbrecht, J.; Freibauer, A.

2014-04-01

Anthropogenic drainage of peatlands releases additional greenhouse gases to the atmosphere, and dissolved carbon (C) and nutrients to downstream ecosystems. Rewetting drained peatlands offers a possibility to reduce nitrogen (N) and C losses. In this study, we investigate the impact of drainage and rewetting on the cycling of dissolved C and N as well as on dissolved gases, over a period of 1 year and a period of 4 months. We chose four sites within one Atlantic bog complex: a near-natural site, two drained grasslands with different mean groundwater levels and a former peat cutting area rewetted 10 years ago. Our results clearly indicate that long-term drainage has increased the concentrations of dissolved organic carbon (DOC), ammonium, nitrate and dissolved organic nitrogen (DON) compared to the near-natural site. DON and ammonium contributed the most to the total dissolved nitrogen. Nitrate concentrations below the mean groundwater table were negligible. The concentrations of DOC and N species increased with drainage depth. In the deeply-drained grassland, with a mean annual water table of 45 cm below surface, DOC concentrations were twice as high as in the partially rewetted grassland with a mean annual water table of 28 cm below surface. The deeply drained grassland had some of the highest-ever observed DOC concentrations of 195.8 ± 77.3 mg L-1 with maximum values of >400 mg L-1. In general, dissolved organic matter (DOM) at the drained sites was enriched in aromatic moieties and showed a higher degradation status (lower DOC to DON ratio) compared to the near-natural site. At the drained sites, the C to N ratios of the uppermost peat layer were the same as of DOM in the peat profile. This suggests that the uppermost degraded peat layer is the main source of DOM. Nearly constant DOM quality through the profile furthermore indicated that DOM moving downwards through the drained sites remained largely biogeochemically unchanged. Unlike DOM concentration, DOM quality and dissolved N species distribution were similar in the two grasslands and thus unaffected by the drainage depth. Methane production during the winter months at the drained sites was limited to the subsoil, which was quasi-permanently water saturated. The recovery of the water table in the winter months led to the production of nitrous oxide around mean water table depth at the drained sites. The rewetted and the near-natural site had comparable DOM quantity and quality (DOC to DON ratio and aromaticity). 10 years after rewetting quasi-pristine biogeochemical conditions have been re-established under continuously water logged conditions in the former peat cut area. Only the elevated dissolved methane and ammonium concentrations reflected the former disturbance by drainage and peat extraction. Rewetting via polder technique seems to be an appropriate way to revitalize peatlands on longer timescales and to improve the water quality of downstream water bodies.

Geochemistry and metamorphism of the Mouriscas Complex, Ossa-Morena/Central Iberian zone boundary, Iberian Massif, Central Portugal: Implications for the Cadomian and Variscan orogenies

NASA Astrophysics Data System (ADS)

Henriques, S. B. A.; Neiva, A. M. R.; Tajčmanová, L.; Dunning, G. R.

2018-01-01

The Mouriscas Complex is a deformed and metamorphosed predominantly mafic igneous complex of Ediacaran and Ordovician age and crops out at the Ossa-Morena/Central Iberian zone boundary in the Iberian Massif, Central Portugal. It comprises amphibolite with Neoproterozoic protoliths (ca. 544 Ma), protomylonitic felsic dykes derived from younger trondhjemitic protoliths (ca. 483 Ma) and garnet amphibolite derived of even younger dioritic protoliths (ca. 477 Ma). The protoliths of the Neoproterozoic amphibolites are calc-alkaline magmas of basic to intermediate compositions with intraplate and active continental margin affinities and are considered to represent the final phase of the Cadomian arc magmatism. They are interpreted to have originated as coarse-grained intrusions, likely gabbro or diorite and generated from the partial melting of meta-igneous lower crust and mantle. Their emplacement occurred near the Cadomian metamorphic event dated at ca. 540 Ma (P = 7-8 kbar and T = 640-660 °C) which is interpreted to represent a continental collision. During the Late Cambrian-Early Ordovician an extensional episode occurred in the central-southern Iberian Massif and was also observed in other areas of the Variscan Orogen. It led to mantle upwelling and to the development of an aborted intracratonic rift located at the Ossa-Morena/Central Iberian zone boundary and to the opening of the Rheic Ocean to the south of the area studied in present coordinates (i.e., between the Ossa-Morena and South Portuguese Zones). This event has been dated at ca. 477 Ma and was responsible for the melting of deep ancient mafic crust and mantle with formation of bimodal magmatism in an intra-plate setting, as indicated by the protoliths of the protomylonitic felsic dykes with trondhjemitic composition and of the garnet amphibolite. Subsequent Variscan metamorphism took place under amphibolite facies conditions (P = 4-5.5 kbar; T = 600-625 °C) at lower P-T conditions than the Cadomian metamorphic event. It was followed by greenschist retrogression as suggested by the appearance of actinolite rims and formation of chlorite and epidote.

Extensional faulting in the southern Klamath Mountains, California

USGS Publications Warehouse

Schweickert, R.A.; Irwin, W.P.

1989-01-01

Large northeast striking normal faults in the southern Klamath Mountains may indicate that substantial crustal extension occurred during Tertiary time. Some of these faults form grabens in the Jurassic and older bedrock of the province. The grabens contain continental Oligocene or Miocene deposits (Weaverville Formation), and in two of them the Oligocene or Miocene is underlain by Lower Cretaceous marine formations (Great Valley sequence). At the La Grange gold placer mine the Oligocene or Miocene strata dip northwest into the gently southeast dipping mylonitic footwall surface of the La Grange fault. The large normal displacement required by the relations at the La Grange mine is also suggested by omission of several kilometers of structural thickness of bedrock units across the northeast continuation of the La Grange fault, as well as by significant changes in bedrock across some northeast striking faults elsewhere in the Central Metamorphic and Eastern Klamath belts. The Trinity ultramafic sheet crops out in the Eastern Klamath terrane as part of a broad northeast trending arch that may be structurally analogous to the domed lower plate of metamorphic core complexes found in eastern parts of the Cordillera. The northeast continuation of the La Grange fault bounds the southeastern side of the Trinity arch in the Eastern Klamath terrane and locally cuts out substantial lower parts of adjacent Paleozoic strata of the Redding section. Faults bounding the northwestem side of the Trinity arch generally trend northeast and juxtapose stacked thrust sheets of lower Paleozoic strata of the Yreka terrane against the Trinity ultramafic sheet. Geometric relations suggest that the Tertiary extension of the southern Klamath Mountains was in NW-SE directions and that the Redding section and the southern part of the Central Metamorphic terrane may be a large Tertiary allochthon detached from the Trinity ultramafic sheet. Paleomagnetic data indicate a lack of rotation about a vertical axis during the extension. We propose that the Trinity ultramafic sheet is structurally analogous to a metamorphic core complex; if so, it is the first core complex to be described that involves ultramafic rocks. We infer that Mesozoic terrane accretion produced a large gravitational instability in the crust that spread laterally during Tertiary extension

Effect of photodegradation and biodegradation on the concentration and composition of dissolved organic matter in diverse waterbodies

NASA Astrophysics Data System (ADS)

Manalilkada Sasidharan, S.; Dash, P.; Singh, S.; Lu, Y.

2017-12-01

The objective of this research was to quantify the effects of photodegradation and biodegradation on the dissolved organic matter (DOM) concentration and composition in five distinct waterbodies with diverse types of watershed land use and land cover in the southeastern United States. The water bodies included an agricultural pond, a lake in a predominantly forested watershed, a man-made reservoir, an estuary, and a bay. Two sets of samples were prepared from these water bodies by dispensing filtered water samples to unfiltered samples in 10:1 ratio. The first set was kept in the sunlight during the day (12 hours), and colored dissolved organic matter (CDOM) absorption and fluorescence were measured periodically over a 30-day period for examining the effects of combined photo- and biodegradation. The second set of samples was kept in the dark for examining the effects of biodegradation alone, and CDOM absorption and fluorescence were measured at the same time as the sunlight-exposed samples. Subsequently, spectrometric results in tandem with multivariate statistical analysis were used to interpret the lability vs. composition of DOM. Parallel factor analysis (PARAFAC) revealed the presence of four DOM components (C1-C4). C1 and C4 were microbial tryptophan-like, labile lighter components, while C2 and C3 were terrestrial humic like or fulvic acid type, larger aromatic refractory components. The principal component analysis (PCA) also revealed two distinct groups of DOM - C1 and C4 vs. C2 and C3. The negative PC1 loadings of C2, C3, HIX, a254 and SUVA indicated humic-like or fulvic-like structurally complex refractory aromatic DOM originated from higher plants in forested areas. C1, C4, SR, FI and BI had positive PC1 loadings, which indicated structurally simpler labile DOM were derived from agricultural areas or microbial activity. There was a decrease in dissolved organic carbon (DOC) due to combined photo- and biodegradation, and transformation of components C2, C3 into components C1, C4 was at a much faster rate than only biodegradation. This observation suggests that the presence of sunlight facilitated the degradation of larger, recalcitrant, terrestrial humic-like compounds into smaller, labile microbial components.

P-T paths of ophiolite-related metamorphic rocks from the Dinaride ophiolite zone in Bosnia

NASA Astrophysics Data System (ADS)

Balen, Dražen; Massonne, Hans-Joachim; Koller, Friedrich; Theye, Thomas; Opitz, Joachim; Hrvatović, Hazim; Premužak, Lucija

2017-04-01

The Dinarides, an Alpine mountain chain in south-eastern Europe, is characterized by complex fold, thrust, and imbricate structures. Partially dismembered ophiolites, a regular part of the Inner Dinarides, are considered as separate ultramafic massifs. The large Krivaja-Konjuh ultramafic massif (KKUM) within the Dinaride Ophiolite Zone (DOZ), composed of tectonic spinel lherzolite, occurs as NE-dipping thrust sheet underlain by gradually decreasing, up to 1200 m thick, high- to medium-grade metamorphic rocks. The metamorphic rocks geochemically resemble MORB-like rocks with tholeiitic signature. Such metamorphic rocks, which originated from cumulate gabbro and/or troctolite, are mainly represented by granulite and amphibolite varieties (subordinate eclogite and epidote-amphibolite facies metamafic rocks are also present) with various proportions of amphibole, plagioclase, pyroxenes (diopside and hypersthene), garnet, corundum, sapphirine, spinel and quartz. These rocks vary in textures (granoblastic, porphyroblastic and nematoblastic) and grain size (coarse- to fine-grain varieties). Conventional thermobarometry of garnet- and clinopyroxene-bearing amphibolites directly beneath the contact to the overlying peridotite resulted in peak pressure (P) - temperature (T) conditions of 10-12 kbar (depth of ca. 35-40 km) and 745-830°C. Those amphibolites without clinopyroxene but with garnet experienced peak conditions of 7 kbar and 630°C. Amphibole + plagioclase amphibolite gave temperatures of 670-730 °C and lowermost-grade amphibolites yielded peak temperatures of 550°C. These estimates are thought to reflect the metamorphic conditions during the Late Jurassic obduction of the hot upper mantle part of the KKUM onto the ophiolite mélange. The hot obducted ultramafic fragments acted as a heat source for metamorphism that transformed cumulate gabbroic protolith into high- to medium-grade amphibolites and granulites. P-T pseudosections constructed for various metamorphic rock types in the MnNCFMASHTO system, contoured by mineral isopleths and modes, combined with chemical zonation of garnet (elucidated by X-ray mapping), succession of accessory Ti-minerals (ilmenite -> rutile -> titanite) and textural features (particularly occurrence of complex kelyphite textures around garnet and clinopyroxene) gave us important clues for P-T paths (re)constructions. The petrographic details and mineral chemistry point to composite clockwise P-T paths characterized by high-temperature high-pressure conditions (ca. 20 kbar, 700 °C for garnet- and amphibole-bearing metaperidotite), followed by significant pressure decrease to medium-pressure values accompanied by temperature increase to > 830 °C. Such a composite P-T path can be interpreted in the frame of Late Jurassic to Early Cretaceous regional geodynamic processes that involve collision at the edge of the Adriatic microplate, intra-oceanic NE-dipping subduction and underplating of mafic cumulate rocks under the hot upper mantle part of the KKUM and subsequent erosional events. Processes of the final emplacement of the KKUM metamorphic rocks must have been terminated in Early Cretaceous times as indicated by amphibolite fragments in the adjacent Pogari Formation overlying the ophiolite mélange. Support by the Croatian Science Foundation (IP-2014-09-9541) is acknowledged.

Age mapping and dating of monazite on the electron microprobe: Deconvoluting multistage tectonic histories

NASA Astrophysics Data System (ADS)

Williams, Michael L.; Jercinovic, Michael J.; Terry, Michael P.

1999-11-01

High-resolution X-ray mapping and dating of monazite on the electron microprobe are powerful geochronological tools for structural, metamorphic, and tectonic analysis. X-ray maps commonly show complex Th, U, and Pb zoning that reflects monazite growth and overgrowth events. Age maps constructed from the X-ray maps simplify the zoning and highlight age domains. Microprobe dating offers a rapid, in situ method for estimating ages of mapped domains. Application of these techniques has placed new constraints on the tectonic history of three areas. In western Canada, age mapping has revealed multiphase monazite, with older cores and younger rims, included in syntectonic garnet. Microprobe ages show that tectonism occurred ca. 1.9 Ga, 700 m.y. later than mylonitization in the adjacent Snowbird tectonic zone. In New Mexico, age mapping and dating show that the dominant fabric and triple-point metamorphism occurred during a 1.4 Ga reactivation, not during the 1.7 Ga Yavapai-Mazatzal orogeny. In Norway, monazite inclusions in garnet constrain high-pressure metamorphism to ca. 405 Ma, and older cores indicate a previously unrecognized component of ca. 1.0 Ga monazite. In all three areas, microprobe dating and age mapping have provided a critical textural context for geochronologic data and a better understanding of the complex age spectra of these multistage orogenic belts.

3D-Reconstructions and Virtual 4D-Visualization to Study Metamorphic Brain Development in the Sphinx Moth Manduca Sexta

PubMed Central

Huetteroth, Wolf; el Jundi, Basil; el Jundi, Sirri; Schachtner, Joachim

2009-01-01

During metamorphosis, the transition from the larva to the adult, the insect brain undergoes considerable remodeling: new neurons are integrated while larval neurons are remodeled or eliminated. One well acknowledged model to study metamorphic brain development is the sphinx moth Manduca sexta. To further understand mechanisms involved in the metamorphic transition of the brain we generated a 3D standard brain based on selected brain areas of adult females and 3D reconstructed the same areas during defined stages of pupal development. Selected brain areas include for example mushroom bodies, central complex, antennal- and optic lobes. With this approach we eventually want to quantify developmental changes in neuropilar architecture, but also quantify changes in the neuronal complement and monitor the development of selected neuronal populations. Furthermore, we used a modeling software (Cinema 4D) to create a virtual 4D brain, morphing through its developmental stages. Thus the didactical advantages of 3D visualization are expanded to better comprehend complex processes of neuropil formation and remodeling during development. To obtain datasets of the M. sexta brain areas, we stained whole brains with an antiserum against the synaptic vesicle protein synapsin. Such labeled brains were then scanned with a confocal laser scanning microscope and selected neuropils were reconstructed with the 3D software AMIRA 4.1. PMID:20339481

3D-Reconstructions and Virtual 4D-Visualization to Study Metamorphic Brain Development in the Sphinx Moth Manduca Sexta.

PubMed

Huetteroth, Wolf; El Jundi, Basil; El Jundi, Sirri; Schachtner, Joachim

2010-01-01

DURING METAMORPHOSIS, THE TRANSITION FROM THE LARVA TO THE ADULT, THE INSECT BRAIN UNDERGOES CONSIDERABLE REMODELING: new neurons are integrated while larval neurons are remodeled or eliminated. One well acknowledged model to study metamorphic brain development is the sphinx moth Manduca sexta. To further understand mechanisms involved in the metamorphic transition of the brain we generated a 3D standard brain based on selected brain areas of adult females and 3D reconstructed the same areas during defined stages of pupal development. Selected brain areas include for example mushroom bodies, central complex, antennal- and optic lobes. With this approach we eventually want to quantify developmental changes in neuropilar architecture, but also quantify changes in the neuronal complement and monitor the development of selected neuronal populations. Furthermore, we used a modeling software (Cinema 4D) to create a virtual 4D brain, morphing through its developmental stages. Thus the didactical advantages of 3D visualization are expanded to better comprehend complex processes of neuropil formation and remodeling during development. To obtain datasets of the M. sexta brain areas, we stained whole brains with an antiserum against the synaptic vesicle protein synapsin. Such labeled brains were then scanned with a confocal laser scanning microscope and selected neuropils were reconstructed with the 3D software AMIRA 4.1.

Molecular Phylogeny of Neotropical Anopheles (Nyssorhynchus) albitarsis Species Complex (Diptera: Culicidae)

DTIC Science & Technology

2005-11-01

Insti- tution, National Museum ofNatural History (NMNH) and the Faculdade de Saude Publica, Universidade de Sao Paulo (FSP-USP). DNA voucher...the Albitarsis Complex, was rccenlly recognized as the primary vector of malaria parasites in northeastern Amazonia , Brazil (Conn el aI. 200(2). Other...Museum, Department of7.ool0l(y, Cromwell Rd.• London 5W75Bo. United KinJ(dom. 1 Nlicleo de Pesquisas Taxon&nica e Sistemdtica em Entomologia M~ica

The Effects of Biodegradation and Photodegradation on DOM Optical Properties: Controlled Laboratory Study Using Plant, Soil and Algal Leachates

NASA Astrophysics Data System (ADS)

Hansen, A. M.; Kraus, T. E. C.; Pellerin, B. A.; Fleck, J.

2014-12-01

Many studies use optical properties to infer dissolved organic matter (DOM) composition and origin; however, there are few controlled studies which examine the effects of environmental processing on different DOM sources. Our goal was to better understand the roles DOM plays in wetland environments of the Sacramento-San Joaquin Delta. Therefore, five endmember sources of DOM from this region were selected for use in this study: peat soil (euic, thermic Typic Medisaprists); three aquatic macrophytes (white rice (Oryza sativa); tule (Schoenoplectus acutus); cattail (Typha spp.)); and one diatom (Thalassiosira weissflogii). We measured DOM concentrations (mg C/L) and optical properties (absorbance and fluorescence) of these sources following biological and photochemical degradation over a three month period. DOM concentration decreased by over 90% in plant and algal leachates following 3 months of biodegradation, while photoexposure had negligible effects. The fluorescence index (FI), humic index (HI), specific UV absorbance at 254 nm (SUVA), and carbon-normalized fluorescence of Peaks C and A increased with biodegradation, whereas Peak T decreased. Photoexposure resulted in a decrease of the FI, HI and SUVA values. Our results emphasize the need to better understand how environmental processing affects DOM properties in aquatic environments; the frequently opposing effects of biodegradation and photodegradation, which occur simultaneously in nature, make it challenging to decipher the original DOM source without considering multiple parameters. This dataset can help us better identify which optical properties, either individual or in combination, can provide insight into how biogeochemical processes affect DOM in aquatic environments.

Fluorescence Excitation-Emission Matrix Regional Integration to Quantify Spectra for Dissolved Organic Matter

USGS Publications Warehouse

Chen, W.; Westerhoff, P.; Leenheer, J.A.; Booksh, K.

2003-01-01

Excitation-emission matrix (EEM) fluorescence spectroscopy has been widely used to characterize dissolved organic matter (DOM) in water and soil. However, interpreting the >10,000 wavelength-dependent fluorescence intensity data points represented in EEMs has posed a significant challenge. Fluorescence regional integration, a quantitative technique that integrates the volume beneath an EEM, was developed to analyze EEMs. EEMs were delineated into five excitation-emission regions based on fluorescence of model compounds, DOM fractions, and marine waters or freshwaters. Volumetric integration under the EEM within each region, normalized to the projected excitation-emission area within that region and dissolved organic carbon concentration, resulted in a normalized region-specific EEM volume (??i,n). Solid-state carbon nuclear magnetic resonance (13C NMR), Fourier transform infrared (FTIR) analysis, ultraviolet-visible absorption spectra, and EEMs were obtained for standard Suwannee River fulvic acid and 15 hydrophobic or hydrophilic acid, neutral, and base DOM fractions plus nonfractionated DOM from wastewater effluents and rivers in the southwestern United States. DOM fractions fluoresced in one or more EEM regions. The highest cumulative EEM volume (??T,n = ????i,n) was observed for hydrophobic neutral DOM fractions, followed by lower ??T,n values for hydrophobic acid, base, and hydrophilic acid DOM fractions, respectively. An extracted wastewater biomass DOM sample contained aromatic protein- and humic-like material and was characteristic of bacterial-soluble microbial products. Aromatic carbon and the presence of specific aromatic compounds (as indicated by solid-state 13C NMR and FTIR data) resulted in EEMs that aided in differentiating wastewater effluent DOM from drinking water DOM.

Light limitation plays a central role in regulating DOM reactions in temperate watersheds

NASA Astrophysics Data System (ADS)

Yoon, B.; Hosen, J. D.; Kyzivat, E.; Fair, J. H.; Weber, L.; Aho, K. S.; Stubbins, A.; Lowenthal, R. S.; Raymond, P. A.

2017-12-01

Biological uptake and photochemical oxidation determine how much dissolved organic matter (DOM) can be removed and exported from inland waters. It is thus critical to understand the control on the biological and photochemical oxidation of DOM, and identify potential synergy between these two DOM removal processes. Yet, the variability of biological and photochemical lability, and the prevalence of priming effects between the two removal mechanisms are poorly understood at larger spatiotemporal scale. To address this knowledge gap, we analyzed the lability of 900 samples collected throughout the Connecticut River across two years (n = 510 for biolability, n=394 for photolability). Furthermore, we measured the effect of photochemical priming for biological removal and of biological priming for photochemical removal (n= 151, n=146, respectively). Our results show that photolability is on average 5 times greater than biolability, and that the mass of photolabile DOM can be predicted from UV absorbance at 254 nm. Photochemical DOM removal also led to additional "unlocking" of previously bio-recalcitrant DOM in 80% of the samples, and increased the biological lability by threefold on average. Scaling further, we extrapolate our model to estimate that the DOM fluxes leaving the Connecticut River and the Mississippi River are 49% and 45% photolabile, respectively. The significant photoreactivity observed across the samples and the subsequent increase in biolability demonstrate that sunlight is a more potent agent of DOM removal than the biological reactions. Yet, the photolability of DOM fluxes leaving the Connecticut River and Mississippi River indicates that the full photo-oxidation potential is not achieved due to light limitation.

Comparison of the discriminative stimulus effects of dimethyltryptamine with different classes of psychoactive compounds in rats.

PubMed

Gatch, Michael B; Rutledge, Margaret A; Carbonaro, Theresa; Forster, Michael J

2009-07-01

There has been increased recreational use of dimethyltryptamine (DMT), but little is known of its discriminative stimulus effects. The present study assessed the similarity of the discriminative stimulus effects of DMT to other types of hallucinogens and to psychostimulants. Rats were trained to discriminate DMT from saline. To test the similarity of DMT to known hallucinogens, the ability of (+)-lysergic acid diethylamide (LSD), (-)-2,5-dimethoxy-4-methylamphetamine (DOM), (+)-methamphetamine, or (+/-)3,4-methylenedioxymethyl amphetamine (MDMA) to substitute in DMT-trained rats was tested. The ability of DMT to substitute in rats trained to discriminate each of these compounds was also tested. To assess the degree of similarity in discriminative stimulus effects, each of the compounds was tested for substitution in all of the other training groups. LSD, DOM, and MDMA all fully substituted in DMT-trained rats, whereas DMT fully substituted only in DOM-trained rats. Full cross-substitution occurred between DMT and DOM, LSD and DOM, and (+)-methamphetamine and MDMA. MDMA fully substituted for (+)-methamphetamine, DOM, and DMT, but only partially for LSD. In MDMA-trained rats, LSD and (+)-methamphetamine fully substituted, whereas DMT and DOM did not fully substitute. No cross-substitution was evident between (+)-methamphetamine and DMT, LSD, or DOM. DMT produces discriminative stimulus effects most similar to those of DOM, with some similarity to the discriminative stimulus effects of LSD and MDMA. Like DOM and LSD, DMT seems to produce predominately hallucinogenic-like discriminative stimulus effects and minimal psychostimulant effects, in contrast to MDMA which produced hallucinogen- and psychostimulant-like effects.

Hydrologic Controls on In-Stream Optical Dissolved Organic Matter Characteristics in an Old-Growth Forest of the Oregon Cascades

NASA Astrophysics Data System (ADS)

Lajtha, K.; Lee, B. S.

2015-12-01

Dissolved organic matter (DOM) is a critical component of the carbon cycle linking terrestrial and aquatic ecosystems, yet DOM composition representative of DOM sources at headwater catchments in the western U.S is poorly understood. This study examined the effect of forest management history and hydrologic patterns on DOM chemistry at nine experimental watersheds located in the H.J. Andrews Long Term Ecological Research Experimental Forest of the Oregon Cascades. Stream water samples representing a three-week composite of each watershed were collected between May 2013 and February 2015 (32 events). DOM chemistry was characterized by examining UV and fluorescent properties of stream samples. Specific UV absorbance at 254 nm (SUVA254; Weishaar et al. 2003), generally indicative of aromaticity, showed the lowest value at the high elevation clear-cut site (watershed 6, 1,030 m) and the highest value at the low elevation clear-cut site (watershed 10, 680 m) throughout the study period. DOM fluorescent components, identified by this study using a multivariate statistical model, Parallel Factor Analysis (PARAFAC), did not differ significantly among experimental watersheds with varying forest management history. However, a protein-like DOM component exhibited temporal variations. Correlation analysis between the protein-like DOM and hydrologic patterns indicate that stream water during dry seasons come from protein-rich groundwater sources. This study shows UV and fluorescent spectroscopy DOM characterization is a viable finger printing method to detect DOM sources in pristine headwater streams at the western Cascades of Oregon where characterization of the stream water source with low DOC and DON concentrations is difficult.

Actinide Sorption in Rainier Mesa Tunnel Waters from the Nevada Test Site

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, P; Zavarin, M; Leif, R

2007-12-17

The sorption behavior of americium (Am), plutonium (Pu), neptunium (Np), and uranium (U) in perched Rainier Mesa tunnel water was investigated. Both volcanic zeolitized tuff samples and groundwater samples were collected from Rainier Mesa, Nevada Test Site, NV for a series of batch sorption experiments. Sorption in groundwater with and without the presence of dissolved organic matter (DOM) was investigated. Am(III) and Pu(IV) are more soluble in groundwater that has high concentrations of DOM. The sorption K{sub d} for Am(III) and Pu(IV) on volcanic zeolitized tuff was up to two orders of magnitude lower in samples with high DOM (15more » to 19 mg C/L) compared to samples with DOM removed (< 0.4 mg C/L) or samples with naturally low DOM (0.2 mg C/L). In contrast, Np(V) and U(VI) sorption to zeolitized tuff was much less affected by the presence of DOM. The Np(V) and U(VI) sorption Kds were low under all conditions. Importantly, the DOM was not found to significantly sorb to the zeolitized tuff during these experiment. The concentration of DOM in groundwater affects the transport behavior of actinides in the subsurface. The mobility of Am(III) and Pu(IV) is significantly higher in groundwater with elevated levels of DOM resulting in potentially enhanced transport. To accurately model the transport behavior of actinides in groundwater at Rainier Mesa, the low actinide Kd values measured in groundwater with high DOM concentrations must be incorporated in predictive transport models.« less

DOM composition and transformation in boreal forest soils: The effects of temperature and organic-horizon decomposition state

USGS Publications Warehouse

O’Donnell, Jonathan A.; Aiken, George R.; Butler, Kenna D.; Guillemette, Francois; Podgorski, David C.; Spencer, Robert G. M.

2016-01-01

The boreal region stores large amounts of organic carbon (C) in organic-soil horizons, which are vulnerable to destabilization via warming and disturbance. Decomposition of soil organic matter (SOM) contributes to the production and turnover of dissolved organic matter (DOM). While temperature is a primary control on rates of SOM and DOM cycling, little is known about temperature effects on DOM composition in soil leachate. Here we conducted a 30 day incubation to examine the effects of temperature (20 versus 5°C) and SOM decomposition state (moss versus fibric versus amorphous horizons) on DOM composition in organic soils of interior Alaska. We characterized DOM using bulk dissolved organic C (DOC) concentration, chemical fractionation, optical properties, and ultrahigh-resolution mass spectrometry. We observed an increase in DOC concentration and DOM aromaticity in the 20°C treatment compared to the 5°C treatment. Leachate from fibric horizons had higher DOC concentration than shallow moss or deep amorphous horizons. We also observed chemical shifts in DOM leachate over time, including increases in hydrophobic organic acids, polyphenols, and condensed aromatics and decreases in low-molecular weight hydrophilic compounds and aliphatics. We compared ultrahigh-resolution mass spectrometry and optical data and observed strong correlations between polyphenols, condensed aromatics, SUVA254, and humic-like fluorescence intensities. These findings suggest that biolabile DOM was preferentially mineralized, and the magnitude of this transformation was determined by kinetics (i.e., temperature) and substrate quality (i.e., soil horizon). With future warming, our findings indicate that organic soils may release higher concentrations of aromatic DOM to aquatic ecosystems.

Temporal Dynamics in the Concentration, Flux, and Optical Properties of Tree-Derived Dissolved Organic Matter in an Epiphyte-Laden Oak-Cedar Forest

NASA Astrophysics Data System (ADS)

Van Stan, John T.; Wagner, Sasha; Guillemette, François; Whitetree, Ansley; Lewis, Julius; Silva, Leticia; Stubbins, Aron

2017-11-01

Studies on the fate and transport of dissolved organic matter (DOM) along the rainfall-to-discharge flow pathway typically begin in streams or soils, neglecting the initial enrichment of rainfall with DOM during contact with plant canopies. However, rain water can gather significant amounts of tree-derived DOM (tree-DOM) when it drains from the canopy, as throughfall, and down the stem, as stemflow. We examined the temporal variability of event-scale tree-DOM concentrations, yield, and optical (light absorbance and fluorescence) characteristics from an epiphyte-laden Quercus virginiana-Juniperus virginiana forest on Skidaway Island, Savannah, Georgia (USA). All tree-DOM fluxes were highly enriched in dissolved organic carbon (DOC) compared to rainfall, and epiphytes further increased concentrations. Stemflow DOC concentrations were greater than throughfall across study species, yet larger throughfall water yields produced greater DOC yields versus stemflow. Tree-DOM optical characteristics indicate it is aromatic-rich with fluorescent DOM dominated by humic-like fluorescence, containing 10-20% protein-like (tryptophan-like) fluorescence. Storm size was the only storm condition that strongly correlated with tree-DOM concentration and flux; however, throughfall and stemflow optical characteristics varied little across a wide range of storm conditions (from low magnitude events to intense tropical storms). Annual tree-DOM yields from the study forest (0.8-46 g C m-2 yr-1) were similar to other yields from discrete down-gradient fluxes (litter leachates, soil leachates, and stream discharge) along the rainfall-to-discharge flow path.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schumacher,M.; Christl, I.; Vogt, R.

The chemical composition and carbon isotope signature of aquatic dissolved organic matter (DOM) in five boreal forest catchments in Scandinavia were investigated. The DOM was isolated during spring and fall seasons using a reverse osmosis technique. The DOM samples were analyzed by elemental analysis, FT-IR, solid-state CP-MAS {sup 13}C-NMR, and C-1s NEXAFS spectroscopy. In addition, the relative abundance of carbon isotopes ({sup 12}C, {sup 13}C, {sup 14}C) in the samples was measured. There were no significant differences in the chemical composition or carbon isotope signature of the DOM sampled in spring and fall seasons. Also, differences in DOM composition betweenmore » the five catchments were minor. Compared to reference peat fulvic and humic acids, all DOM samples were richer in O-alkyl carbon and contained less aromatic and phenolic carbon, as shown by FT-IR, {sup 13}C-NMR, and C-1s NEXAFS spectroscopy. The DOM was clearly enriched in {sup 14}C relative to the NBS oxalic acid standard of 1950, indicating that the aquatic DOM contained considerable amounts of organic carbon younger than about 50 years. The weight-based C:N ratios of 31 {+-} 6 and the {delta}{sup 13}Cvalues of -29 {+-} 2{per_thousand}indicate that the isolated DOM is of terrestrial rather than aquatic origin. We conclude that young, hydrophilic carbon compounds of terrestrial origin are predominant in the samples investigated, and that the composition of the aquatic DOM in the studied boreal forest catchments is rather stable during low to intermediate flow conditions.« less

Characterization and Fate of Dissolved Organic Matter in the Lena Delta Region, Siberia

NASA Astrophysics Data System (ADS)

Goncalves-Araujo, R.; Stedmon, C. A.; Heim, B.; Dubinenkov, I.; Kraberg, A.; Moiseev, D.; Bracher, A.

2016-02-01

Connectivity between the terrestrial and marine environment in the Artic is changing as a result of climate change, influencing both freshwater budgets and the supply of carbon to the sea. This study characterizes the optical properties of dissolved organic matter (DOM) within the Lena Delta region and evaluates the behavior of DOM across the fresh water-marine gradient. Six fluorescent components (four humic-like; one marine humic-like; one protein-like) were identified by Parallel Factor Analysis (PARAFAC) with a clear dominance of allochthonous humic-like signals. Colored DOM (CDOM) and dissolved organic carbon (DOC) were highly correlated and had their distribution coupled with hydrographical conditions. Higher DOM concentration and degree of humification were associated with the low salinity waters of the Lena River. Values decreased towards the higher salinity Laptev Sea shelf waters. Results demonstrate different responses of DOM mixing in relation to the vertical structure of the water column, as reflecting the hydrographical dynamics in the region. Two mixing curves for DOM were apparent. In surface waters above the pycnocline there was a sharper decrease in DOM concentration in relation to salinity indicating removal. In the bottom water layer the DOM decrease within salinity was less. We propose there is a removal of DOM occurring primarily at the surface layer, which is likely driven by photodegradation and flocculation.

Spatial and seasonal variations in stream water delta34S-dissolved organic matter in northern Sweden.

PubMed

Giesler, Reiner; Björkvald, Louise; Laudon, Hoalmar; Mörth, Carl-Magnus

2009-01-15

The discharge of terrestrial dissolved organic matter (DOM) by streams is an important cross-system linkage that strongly influences downstream aquatic ecosystems. Isotopic tracers are important tools that can help to unravel the source of DOM from different terrestrial compartments in the landscape. Here we demonstrate the spatial and seasonal variation of delta34S of DOM in 10 boreal streams to test if the tracer could provide new insights into the origin of DOM. We found large spatial and seasonal variations in stream water delta34S-DOM values ranging from -5.2 per thousand to +9.6 per thousand with an average of +4.0 +/- 0.6 (N = 62; average and 95% confidence interval). Large seasonal variations were found in stream water delta34S-DOM values: for example, a shift of more than 10 per thousand during the spring snowmelt in a wetland-dominated stream. Spatial differences were also observed during the winter base flow with higher delta34S-DOM values in the fourth-order Krycklan stream at the outlet of the 68 km2 catchment compared to the small (< 1 km2) headwater streams. Our data clearly show that the delta34S-DOM values have the potential to be used as a tracer to identify and generate new insights about terrestrial DOM sources in the boreal landscape.

Variation of organic matter quantity and quality in streams at Critical Zone Observatory watersheds

USGS Publications Warehouse

Miller, Matthew P.; Boyer, Elizabeth W.; McKnight, Diane M.; Brown, Michael G.; Gabor, Rachel S.; Hunsaker, Carolyn T.; Iavorivska , Lidiia; Inamdar, Shreeram; Kaplan, Louis A.; Johnson, Dale W.; Lin, Henry; McDowell, William H.; Perdrial, Julia N.

2016-01-01

The quantity and chemical composition of dissolved organic matter (DOM) in surface waters influence ecosystem processes and anthropogenic use of freshwater. However, despite the importance of understanding spatial and temporal patterns in DOM, measures of DOM quality are not routinely included as part of large-scale ecosystem monitoring programs and variations in analytical procedures can introduce artifacts. In this study, we used consistent sampling and analytical methods to meet the objective of defining variability in DOM quantity and quality and other measures of water quality in streamflow issuing from small forested watersheds located within five Critical Zone Observatory sites representing contrasting environmental conditions. Results show distinct separations among sites as a function of water quality constituents. Relationships among rates of atmospheric deposition, water quality conditions, and stream DOM quantity and quality are consistent with the notion that areas with relatively high rates of atmospheric nitrogen and sulfur deposition and high concentrations of divalent cations result in selective transport of DOM derived from microbial sources, including in-stream microbial phototrophs. We suggest that the critical zone as a whole strongly influences the origin, composition, and fate of DOM in streams. This study highlights the value of consistent DOM characterization methods included as part of long-term monitoring programs for improving our understanding of interactions among ecosystem processes as controls on DOM biogeochemistry.

Effects of molecular weight on the diffusion coefficient of aquatic dissolved organic matter and humic substances.

PubMed

Balch, J; Guéguen, C

2015-01-01

In situ measurements of labile metal species using diffusive gradients in thin films (DGT) passive samplers are based on the diffusion rates of individual species. Although most studies have dealt with chemically isolated humic substances, the diffusion of dissolved organic matter (DOM) across the hydrogel is not well understood. In this study, the diffusion coefficient (D) and molecular weight (MW) of 11 aquatic DOM and 4 humic substances (HS) were determined. Natural, unaltered aquatic DOM was capable of diffusing across the diffusive gel membrane with D values ranging from 2.48×10(-6) to 5.31×10(-6) cm(2) s(-1). Humic substances had diffusion coefficient values ranging from 3.48×10(-6) to 6.05×10(-6) cm(2) s(-1), congruent with previous studies. Molecular weight of aquatic DOM and HS samples (∼500-1750 Da) measured using asymmetrical flow field-flow fractionation (AF4) strongly influenced D, with larger molecular weight DOM having lower D values. No noticeable changes in DOM size properties were observed during the diffusion process, suggesting that DOM remains intact following diffusion across the diffusive gel. The influence of molecular weight on DOM mobility will assist in further understanding and development of the DGT technique and the uptake and mobility of contaminants associated with DOM in aquatic environments. Copyright © 2014 Elsevier Ltd. All rights reserved.

Spatial and temporal variations in DOM composition in ecosystems: The importance of long-term monitoring of optical properties

Treesearch

R. Jaffe; D. McKnight; N. Maie; R. Cory; W. H. McDowell; J.L. Campbell

2008-01-01

Source, transformation, and preservation mechanisms of dissolved organic matter (DOM) remain elemental questions in contemporary marine and aquatic sciences and represent a missing link in models of global elemental cycles. Although the chemical character of DOM is central to its fate in the global carbon cycle, DOM characterizations in long-term ecological research...

Spatial dependence of reduced sulfur in Everglades dissolved organic matter controlled by sulfate enrichment

USGS Publications Warehouse

Poulin, Brett A.; Ryan, Joseph N.; Nagy, Kathryn L.; Stubbins, Aron; Dittmar, Thorsten; Orem, William H.; Krabbenhoft, David P.; Aiken, George R.

2017-01-01

Sulfate inputs to the Florida Everglades stimulate sulfidic conditions in freshwater wetland sediments that affect ecological and biogeochemical processes. An unexplored implication of sulfate enrichment is alteration of the content and speciation of sulfur in dissolved organic matter (DOM), which influences the reactivity of DOM with trace metals. Here, we describe the vertical and lateral spatial dependence of sulfur chemistry in the hydrophobic organic acid fraction of DOM from unimpacted and sulfate-impacted Everglades wetlands using X-ray absorption spectroscopy and ultrahigh-resolution mass spectrometry. Spatial variation in DOM sulfur content and speciation reflects the degree of sulfate enrichment and resulting sulfide concentrations in sediment pore waters. Sulfur is incorporated into DOM predominantly as highly reduced species in sulfidic pore waters. Sulfur-enriched DOM in sediment pore waters exchanges with overlying surface waters and the sulfur likely undergoes oxidative transformations in the water column. Across all wetland sites and depths, the total sulfur content of DOM correlated with the relative abundance of highly reduced sulfur functionality. The results identify sulfate input as a primary determinant on DOM sulfur chemistry to be considered in the context of wetland restoration and sulfur and trace metal cycling.

Metabolomics Reveal Optimal Grain Preprocessing (Milling) toward Rice Koji Fermentation.

PubMed

Lee, Sunmin; Lee, Da Eun; Singh, Digar; Lee, Choong Hwan

2018-03-21

A time-correlated mass spectrometry (MS)-based metabolic profiling was performed for rice koji made using the substrates with varying degrees of milling (DOM). Overall, 67 primary and secondary metabolites were observed as significantly discriminant among different samples. Notably, a higher abundance of carbohydrate (sugars, sugar alcohols, organic acids, and phenolic acids) and lipid (fatty acids and lysophospholipids) derived metabolites with enhanced hydrolytic enzyme activities were observed for koji made with DOM of 5-7 substrates at 36 h. The antioxidant secondary metabolites (flavonoids and phenolic acid) were relatively higher in koji with DOM of 0 substrates, followed by DOM of 5 > DOM of 7 > DOM of 9 and 11 at 96 h. Hence, we conjecture that the rice substrate preprocessing between DOM of 5 and 7 was potentially optimal toward koji fermentation, with the end product being rich in distinctive organoleptic, nutritional, and functional metabolites. The study rationalizes the substrate preprocessing steps vital for commercial koji making.

Fractions and biodegradability of dissolved organic matter derived from different composts.

PubMed

Wei, Zimin; Zhang, Xu; Wei, Yuquan; Wen, Xin; Shi, Jianhong; Wu, Junqiu; Zhao, Yue; Xi, Beidou

2014-06-01

An experiment was conducted to determine the fractions of molecular weights (MW) and the biodegradability of dissolved organic matter (DOM) in mature composts derived from dairy cattle manure (DCM), kitchen waste (KW), cabbage waste (CW), tomato stem waste (TSW), municipal solid waste (MSW), green waste (GW), chicken manure (CM), sludge (S), and mushroom culture waste (MCW). There were distinct differences in the concentration and MW fractions of DOM, and the two measures were correlated. Fraction MW>5kDa was the major component of DOM in all mature composts. Determined 5day biochemical oxygen demand (BOD5) of DOM was correlated to the concentration of DOM and all MW fractions except MW>5kDa, indicating that the biodegradability of DOM was a function of the content and proportion of fraction MW<5kDa. This study suggests that the amount and distribution of low MW fractions affect DOM biodegradability. Copyright © 2014 Elsevier Ltd. All rights reserved.

Reconnaissance geology of the Jabal Bitran quadrangle, Kingdom of Saudi Arabia

USGS Publications Warehouse

Kahr, Viktor P.; Overstreet, W.C.; Whitlow, J.W.; Ankary, A.O.

1972-01-01

The Jabal Bitten quadrangle covers an area of 2833 sq km in the eastern part of the Precambrian Shield in Saudi Arabia. The rocks in the quadrangle are divided geographically alone arcuate north-trending lines into an eastern area of granite intruded by a swarm of dikes of rhyolite and andesite, and a western area of dominantly pelitic chlorite-sericite schist, separated by the narrow central complex of the Idsas Range. This complex is composed of pyroclastic rocks, lava, conglomerate, marble, and plutonic mafic rocks that have been intricately modified by episodes of metamorphism, igneous intrusion, and faulting. The Idsas Range contains ancient gold and copper mines, and deposits of magnetite, copper, asbestos, and chromite. The rocks in the Jabal Bitten quadrangle are here interpreted to consist of three major sedimentary and volcanic groups, the lowermost of which was deposited unconformably on hornblende-biotite granite gneiss, and all of which are intruded by granite dikes and plutons. From oldest to youngest the layered rocks are called Halaban Group, Bi'r Khountina Group, and Murdama Group, A biotite-hornblende granite is older than uppermost Bi'r Khountina, and peralkalic granite is younger than Murdama. The layered rocks of these groups are generally metamorphosed to the greenschist facies. The metamorphic grade rises abruptly at the Idsas Range to the albite-epidote-amphibolite facies and lower subfacies of the amphibolite facies in parts of the Halaban Group; some skarn east of the range may be in the upper part of the amphibolite facies. Characteristically, the Halaban Group has the highest grade and the greatest range in metamorphic grade, and the Murdama Group has the lowest but most uniformly developed metamorphic grade. The metamorphism of the rocks was caused by three successive pulses of regional dynamothermal metamorphism plus contact metamorphism around the younger bodies of plutonic igneous rocks. Four major structural elements of the quadrangle are reflected in the geography and geologic units. These are a mantled gneiss dome on the east separated from a north-plunging synclinorium in rocks of the Murdama and Bi?r Khountina Groups on the west by a narrow dejective zone of the Halaban and lower Bi?r Khountina. The dejective zone is much modified by impricate overthrusts and accompanying tear faults. These major faults have pushed elements of the Halaban and Bi?r Khountina westward over Bi?r Khountina and Murdama, with the result that very complex fault patterns have evolved. Open geochemical reconnaissance of the area disclosed one positive anomaly for nickel and 40 threshold indications of several elements, principally nickel, chromium, copper, and tungsten. Heavy-mineral and radiometric reconnaissance showed 18 areas containing scheelite and/or powellite and four areas of anomalous radioactivity. Most of these features are in the dejective zone, as are five of the nine ancient workings, the massive and disseminated magnetite, most of the secondary copper minerals, and the traces of asbestos, magnesite, and chromite known in the quadrangle. The mantled gneiss dome and a complex of gabbro and amphibolite on its southwestern flank are the next most mineralized areas. Scant evidence of mineralization is present in the Murdama Group west of the dejective zone. Magnetite deposits at Jabal Idsas have the greatest potential of the mineral deposits in the Jabal Bitran quadrangle. Further study of gold at Fawara and Selib mines is recommended, as is investigation of a positive nickel anomaly that shows threshold cobalt and above background radioactivity. The garnetiferous skarn in the east-central part of the quadrangle should be examined for composition and abrasive character of the garnet and for the remote possibility of tungsten in scheelite and beryllium in helvite.

An enigmatic source of hematitic carbonate beds containing vast amounts of iron oxidizers in a paleozoic metamorphic complex, South Hungary, Geresd-Hills, Ófalu.

NASA Astrophysics Data System (ADS)

Jáger, Viktor; Dabi, Gergely; Menyhárt, Adrienn

2013-04-01

Near the village of Ófalu, in the Geresd Hills, South Hungary, within the "Mecsekalja tectonic belt", low and intermediate grade paleozoic metamorphic complex (phyllite, gneiss) contains vein-like hematitic carbonate beds, up to 30 cm in thickness. The carbonate mineral is calcite. These hematitic carbonate beds cross-cut the foliation of the phyllite, and show no signs of any metamorphic alteration. In the studied section the red carbonate beds are associated with a vein system filled with multiple generations of vein carbonates(Dabi et al., 2011). The red carbonate beds contain a vaste number of twisted stalks of the iron oxidizing taxon of Gallionella. Rarely in some siliceous parts, Leptothrix-like microbial fossils can be found and these beds also contain numerous unidentifiable, hematitic foraminifers. According to ICP-AES measurements, the hematitic carbonate beds contains 8 % Fe, 0.86 % Mn and 0.12 % Ba. XRD and Raman measurements proved that the iron phase is hematite. The SEM observations revealed that the bacterial microfossils and foraminifers are built up of micron-submicron sized pseudohexagonal platy hematite. The bacterial microfossils of the Gallionella iron oxidizer are very well preserved and reaches about 80 µm length and about 2-3 µm width. The above observations raise the following issues: 1. how did these non metamorphic hematitic-carbonatic beds get inside into the metamorphic complex?, 2. what is the age of the formation of these beds?, and 3. what was the source of the iron? If we consider that the hematitic beds contain foraminifers and iron oxidizing bacteria, and no signs of metamorphic alteration nor foliations can be observed in these beds, the only answer for the first question is that the formations are fractures filled with lime-mud, i.e. neptunian dykes, which penetrated into the cracks of the phyllite. The presence of foraminifers and the geotectonic situation of the unit imply marine origin. Considering that these beds are neptunian dykes, their age must be younger than the paleozoic metamorphic event. They must be older than the Early Cretaceous dyke emplacement in the region, based on cross-cutting relation with limonite stained calcite veins, related to the volcanic activity (Dabi et al., 2011) In this region (Tisza-megaunit) continental rift-related alkali basaltic submarine volcanism was widespread during the Early Cretaceous epoch, when hypabyssal basaltic bodies (intrusive pillow basalts) intruded into unconsolidated sediments. Along these magmatic bodies low temperature hydrothermal circulation of seawater hydrolyzed basaltic glass and mafic minerals, and huge amount of Fe(II) was released and got into the lime mud that was saturated with anaerobic water, where iron oxidizing microorganisms thrived (Jáger et al., 2012).We propose a very similar paleoenvironmental model for Ófalu occurence, where low temperature, reductive iron-rich hydrothermal fluids penetrated soft sediments and contributed to the flourishing of iron-oxidizers. Due to subsequent tectonic events, these iron-rich sediments got into the fissures of the Ófalu metamorphic complex. This model is strenghtened by some borehole and outcrops where the Lower Cretaceous interpillow sediments and hyaloclastites rich in iron oxydes and intrusive pillow basalt can be found close to our investigated section. (Hetényi et al., 1976) This study was supported by the Developing Competitiveness of Universities in the South Transdanubian Region (SROP-4.2.1.B-10/2/KONV-2010-0002). Dabi, G., Siklósy, Z., Schubert, F., Bajnóczi, B., M. Tóth, T., 2011. The relevance of vein texture in understanding the past hydraulic behaviour of a crystalline rock mass: reconstruction of the palaeohydrology of the Mecsekalja Zone, South Hungary. Geofluids, 11, 309-327. Hetényi, R., Földi, M., Hámor, G., Nagy, I., Bilik, I., Jantsky, B. 1976. Magyarázó a Mecsek hegység földtani térképéhez 10 000-es sorozat. MÁFI Budapest (in hungarian). Jáger, V., Molnár, F., Buchs, D. & Koděra, P. 2012: The connection between iron ore formations and "mud-shrimp" colonizations around sunken wood debris and hydrothermal sediments in a Lower Cretaceous continental rift basin, Mecsek Mts., Hungary. — Earth-Science Reviews 114/3-4, 250-278.

Spatio-temporal variability of the molecular fingerprint of soil dissolved organic matter in a headwater agricultural catchment

NASA Astrophysics Data System (ADS)

Jeanneau, Laurent; Pierson-Wickmann, Anne-Catherine; Jaffrezic, Anne; Lambert, Thibault; Gruau, Gérard

2013-04-01

Dissolved organic matter (DOM) is implied in (i) ecosystem services such as the support of biodiversity, (ii) the alteration of the drinkable water quality by formation of trihalomethane and (iii) the transfer of micropollutants from soils to rivers. Moreover, since DOM connects soils and oceans that are interacting with the atmosphere, understanding its biogeochemistry will help in investigating the carbon cycle and in creating strategies to mitigate climate change. DOM in headwater stream ecosystems is mainly inherited from allochtonous inputs with different reservoirs being mobilized during storm and interstorm events at the scale of an hydrological year. Those changes in DOM reservoirs, if accompanied by composition and reactivity changes, may impact DOM ecosystem services and drinking water production processes. Elucidating the compositional changes due to changes in the source of DOM in rivers has thus become a important axis of DOM research. The aim of this study is to test the ability of the molecular tools of the organic geochemistry and more specifically the combination of thermochemiolysis and gas chromatography - mass spectrometry (THM-GC-MS) to (i) link the variability of the river DOM composition to different DOM reservoirs in catchment soils and (ii) provide hypothesis on the nature and the mechanisms of formation (microbial growth, litter decomposition) of those reservoirs. This analytical method seems particularly adapted since it allows the differentiation between vegetal and microbial inputs and the determination of the extent of the biodegradation process of biomolecules such as lignin. To test this method, the molecular fingerprint of soil DOM has been investigated in the wetland area of a small (500 ha) agricultural catchment (the so-called Kervidy-Naizin catchment) located in Brittany, western France. The soil DOM was sampled fortnightly at three depths using zero-tension lysimeters during the hydrological year 2010-2011. The samples were freeze-dried and analyzed for their molecular composition using THM-GC-MS. Three chemical classes of compounds were investigated including lignin, polysaccharides and fatty acids. The combination of those results at the molecular scale with the results of investigations on spectroscopic (specific UV absorbance at 254 nm, SUVA) fingerprints, the isotopic (d13C) fingerprint of DOM and the hydrological data (water table depth) has highlighted (i) the correlation between molecular and bulk scales investigated using the SUVA and the proportion of lignin markers and (ii) the evolution of the molecular composition of soil DOM related to the changes of the water table depth, which could be linked to the mobilization of different reservoirs and/or to the succession of different mechanisms of production governed by the changes in hydrological regimes. This study highlights THM-GC-MS as a valuable tool to investigate the molecular composition of DOM. By differentiating the vegetal and the microbial components of DOM, it allows the investigation of the sources and mechanisms of DOM formation. Finally, its application to a catchment with hydrological data emphasizes the hydrological regime as a main driver of the evolution of the molecular composition of DOM.

CL-imaging and ion microprobe dating of single zircons from a high-grade rock from the Central Zone, Limpopo Belt, South Africa: Evidence for a single metamorphic event at ˜2.0 Ga

NASA Astrophysics Data System (ADS)

Mouri, H.; Brandl, G.; Whitehouse, M.; de Waal, S.; Guiraud, M.

2008-02-01

The combination of ion microprobe dating and cathodoluminescence (CL) imaging of zircons from a high-grade rock from the Central Zone of the Limpopo Belt were used to constrain the age of metamorphic events in the area. Zircon grains extracted from an orthopyroxene-gedrite-bearing granulite were prepared for single crystal CL-imaging and ion microprobe dating. The grains display complex zoning when using SEM-based CL-imaging. A common feature in most grains is the presence of a distinct core with a broken oscillatory zoned structure, which clearly appears to be the remnant of an original grain of igneous origin. This core is overgrown by an unzoned thin rim measuring about 10-30 μm in diameter, which is considered as new zircon growth during a single metamorphic event. Selected domains of the zircon grains were analysed for U, Pb and Th isotopic composition using a CAMECA IMS 1270 ion microprobe (Nordsim facility). Most of the grains define a near-concordant cluster with some evidence of Pb loss. The most concordant ages of the cores yielded a weighted mean 207Pb/ 206Pb age of 2689 ± 15 (2 σ) Ma, interpreted as the age of the protolith of an igneous origin. The unzoned overgrowths of the zircon grains yielded a considerably younger weighted mean 207Pb/ 206Pb age of ˜2006.5 ± 8.0 Ma (2 σ), and these data are interpreted to reflect closely the age of the ubiquitous high-grade metamorphic event in the Central Zone. This study shows clearly, based on both the internal structure of the zircons and the data obtained by ion microprobe dating, that only a single metamorphic event is recorded by the studied 2.69 Ga old rocks, and we found no evidence of an earlier metamorphic event at ˜2.5 Ga as postulated earlier by some workers.

A Petrographic History of Martian Meteorite ALH84001: Two Shocks and an Ancient Age

NASA Technical Reports Server (NTRS)

Treiman, Allan H.

1995-01-01

ALH84001 is an igneous meteorite, an orthopyroxenite of martian origin. It contains petrographic evidence of two shock metamorphic events, separated by thermal and chemical events. The evidence for two shock events suggests that ALH84001 is ancient and perhaps a sample of the martian highlands. From petrography and mineral chemistry, the history of ALH84001 must include: crystallization from magma, a first shock (impact) metamorphism, thermal metamorphism, low-temperature chemical alteration, and a second shock (impact) metamorphism. Originally, ALH84001 was igneous, an orthopyroxene-chromite cumulate. In the first shock event, the igneous rock was cut by melt-breccia or cataclastic veinlets, now bands of equigranular fine-grained pyroxene and other minerals (crush zones). Intact fragments of the cumulate were fractured and strained (now converted to polygonized zones). The subsequent thermal metamorphism (possibly related to the first shock) annealed the melt-breccia or cataclastic veinlets to their present granoblastic texture and permitted chemical homogenization of all mineral species present. The temperature of metamorphism was at least 875 C, based on mineral thermometers. Next, Mg-Fe-Ca carbonates and pyrite replaced plagioclase in both clasts and granular bands, producing ellipsoidal carbonate globules with sub-micron scale compositional stratigraphy, repeated identically in all globules, The second shock event produced microfault offsets of carbonate stratigraphy and other mineral contacts, radial fractures around chromite and maskelynite, and strain birefringence in pyroxene. Maskelynite could not have been preserved from the first shock event, because it would have crystallized back to plagioclase. The martian source area for ALH84001 must permit this complex, multiple impact history. Very few craters on young igneous surfaces are on or near earlier impact features. It is more likely that ALH84001 was ejected from an old igneous unit (Hesperian or Noachian age), pocked by numerous impact craters over its long exposure at the martian surface.

Core-size regulated aggregation/disaggregation of citrate-coated gold nanoparticles (5-50 nm) and dissolved organic matter: Extinction, emission, and scattering evidence

NASA Astrophysics Data System (ADS)

Esfahani, Milad Rabbani; Pallem, Vasanta L.; Stretz, Holly A.; Wells, Martha J. M.

2018-01-01

Knowledge of the interactions between gold nanoparticles (GNPs) and dissolved organic matter (DOM) is significant in the development of detection devices for environmental sensing, studies of environmental fate and transport, and advances in antifouling water treatment membranes. The specific objective of this research was to spectroscopically investigate the fundamental interactions between citrate-stabilized gold nanoparticles (CT-GNPs) and DOM. Studies indicated that 30 and 50 nm diameter GNPs promoted disaggregation of the DOM. This result-disaggregation of an environmentally important polyelectrolyte-will be quite useful regarding antifouling properties in water treatment and water-based sensing applications. Furthermore, resonance Rayleigh scattering results showed significant enhancement in the UV range which can be useful to characterize DOM and can be exploited as an analytical tool to better sense and improve our comprehension of nanomaterial interactions with environmental systems. CT-GNPs having core size diameters of 5, 10, 30, and 50 nm were studied in the absence and presence of added DOM at 2 and 8 ppm at low ionic strength and near neutral pH (6.0-6.5) approximating surface water conditions. Interactions were monitored by cross-interpretation among ultraviolet (UV)-visible extinction spectroscopy, excitation-emission matrix (EEM) spectroscopy (emission and Rayleigh scattering), and dynamic light scattering (DLS). This comprehensive combination of spectroscopic analyses lends new insights into the antifouling behavior of GNPs. The CT-GNP-5 and -10 controls emitted light and aggregated. In contrast, the CT-GNP-30 and CT-GNP-50 controls scattered light intensely, but did not aggregate and did not emit light. The presence of any CT-GNP did not affect the extinction spectra of DOM, and the presence of DOM did not affect the extinction spectra of the CT-GNPs. The emission spectra (visible range) differed only slightly between calculated and actual mixtures of CT-GNP-5 or -10 with DOM, whereas emissions for mixtures of CT-GNP-30 or -50 with DOM were enhanced at the surface plasmon resonance (SPR) wavelength. The emission spectra (ultraviolet range) for protein-like constituents of DOM were quenched. Resonance Rayleigh scattering (RRS) was more intense for the CT-GNP-30 and -50 than for the CT-GNP-5 and -10 controls. Intensity-based DLS particle size distributions (PSDs) of DOM controls, CT-GNP-5 and -10 nm controls, and 5- and 10 nm GNP-DOM mixtures exhibited multimodal aggregation. Analyses of CT-GNP-5 and CT-GNP-10 nm mixtures with DOM indicated overcoating of DOM molecules occurred in close proximity (< 10 nm) to GNPs, whereas similar overcoating was not supported for the CT-GNP-30 or -50 mixtures with DOM. These fundamental observations can be exploited to improve our comprehension of nanomaterial interactions with environmental systems.

Unraveling signatures of biogeochemical processes and the depositional setting in the molecular composition of pore water DOM across different marine environments

NASA Astrophysics Data System (ADS)

Schmidt, Frauke; Koch, Boris P.; Goldhammer, Tobias; Elvert, Marcus; Witt, Matthias; Lin, Yu-Shih; Wendt, Jenny; Zabel, Matthias; Heuer, Verena B.; Hinrichs, Kai-Uwe

2017-06-01

Dissolved organic matter (DOM) in marine sediment pore waters derives largely from decomposition of particulate organic matter and its composition is influenced by various biogeochemical and oceanographic processes in yet undetermined ways. Here, we determine the molecular inventory of pore water DOM in marine sediments of contrasting depositional regimes with ultrahigh-resolution mass spectrometry and complementary bulk chemical analyses in order to elucidate the factors that shape DOM composition. Our sample sets from the Mediterranean, Marmara and Black Seas covered different sediment depths, ages and a range of marine environments with different (i) organic matter sources, (ii) balances of organic matter production and preservation, and (iii) geochemical conditions in sediment and water column including anoxic, sulfidic and hypersaline conditions. Pore water DOM had a higher molecular formula richness than overlying water with up to 11,295 vs. 2114 different molecular formulas in the mass range of 299-600 Da and covered a broader range of element ratios (H/C = 0.35-2.19, O/C = 0.03-1.19 vs. H/C = 0.56-2.13, O/C = 0.15-1.14). Formula richness was independent of concentrations of DOC and TOC. Near-surface pore water DOM was more similar to water column DOM than to deep pore water DOM from the same core with respect to formula richness and the molecular composition, suggesting exchange at the sediment-water interface. The DOM composition in the deeper sediments was controlled by organic matter source, selective decomposition of specific DOM fractions and early diagenetic molecule transformations. Compounds in pelagic sediment pore waters were predominantly highly unsaturated and N-bearing formulas, whereas oxygen-rich CHO-formulas and aromatic compounds were more abundant in pore water DOM from terrigenous sediments. The increase of S-bearing molecular formulas in the water column and pore waters of the Black Sea and the Mediterranean Discovery Basin was consistent with elevated HS- concentrations reflecting the incorporation of sulfur into biomolecules during early diagenesis. Sulfurization resulted in an increased average molecular mass of DOM and higher formula richness (up to 5899 formulas per sample). In sediments from the methanogenic zone in the Black Sea, the DOM pool was distinctly more reduced than overlying sediments from the sulfate-reducing zone. Bottom and pore water DOM from the Discovery Basin contained the highest abundances of aliphatic compounds in the entire dataset; a large fraction of abundant N-bearing formulas possibly represented peptide and nucleotide formulas suggesting preservation of these molecules in the life inhibiting environment of the Discovery Basin. Our unique data set provides the basis for a comprehensive understanding of the molecular signatures in pore water DOM and the turnover of sedimentary organic matter in marine sediments.

Inhibition of precipitation and aggregation of metacinnabar (mercuric sulfide) by dissolved organic matter isolated from the Florida Everglades

USGS Publications Warehouse

Ravichandran, M.; Aiken, G.R.; Ryan, J.N.; Reddy, M.M.

1999-01-01

Precipitation and aggregation of metacinnabar (black HgS) was inhibited in the presence of low concentrations (???3 mg C/L) of humic fractions of dissolved organic matter (DOM) isolated from the Florida Everglades. At low Hg concentrations (??? x 10-8 M), DOM prevented the precipitation of metacinnabar. At moderate Hg concentrations (5 x 10-5 M), DOM inhibited the aggregation of colloidal metacinnabar (Hg passed through a 0.1 ??m filter but was removed by centrifugation). At Hg concentrations greater than 5 x 10-4 M, mercury formed solid metacinnabar particles that were removed from solution by a 0.1 ??m filter. Organic matter rich in aromatic moleties was preferentially removed with the solid. Hydrophobic organic acids (humic and fulvic acids) inhibited aggregation better than hydrophilic organic acids. The presence of chloride, acetate, salicylate, EDTA, and cysteine did not inhibit the precipitation or aggregation of metacinnabar. Calcium enhanced metacinnabar aggregation even in the presence of DOM, but the magnitude of the effect was dependent on the concentrations of DOM, Hg, and Ca. Inhibition of metacinnabar precipitation appears to be a result of strong DOM-Hg binding. Prevention of aggregation of colloidal particles appears to be caused by adsorption of DOM and electrostatic repulsion.Precipitation and aggregation of metacinnabar (black HgS) was inhibited in the presence of low concentrations (???3 mg C/L) of humic fractions of dissolved organic matter (DOM) isolated from the Florida Everglades. At low Hg concentrations (???5??10-8 M), DOM prevented the precipitation of metacinnabar. At moderate Hg concentrations (5??10-5 M), DOM inhibited the aggregation of colloidal metacinnabar (Hg passed through a 0.1 ??m filter but was removed by centrifugation). At Hg concentrations greater than 5??10-4 M, mercury formed solid metacinnabar particles that were removed from solution by a 0.1 ??m filter. Organic matter rich in aromatic moieties was preferentially removed with the solid. Hydrophobic organic acids (humic and fulvic acids) inhibited aggregation better than hydrophilic organic acids. The presence of chloride, acetate, salicylate, EDTA, and cysteine did not inhibit the precipitation or aggregation of metacinnabar. Calcium enhanced metacinnabar aggregation even in the presence of DOM, but the magnitude of the effect was dependent on the concentrations of DOM, Hg, and Ca. Inhibition of metacinnabar precipitation appears to be a result of strong DOM-Hg binding. Prevention of aggregation of colloidal particles appears to be caused by adsorption of DOM and electrostatic repulsion.

Spatio-seasonal variability in dissolved organic matter optical properties and its bioavailability in a subalpine lake

NASA Astrophysics Data System (ADS)

Stadler, Masumi; Ejarque, Elisabet; Kainz, Martin J.

2017-04-01

Allochthonous and autochothonous dissolved organic matter (DOM) in lakes mainly originate from terrestrial and aquatic primary production, respectively. Due to their differing biochemical composition the degradability of DOM by microorganisms is expected to vary. The carbon use efficiency of bacteria and DOM biodegradability determine whether the consumed DOM is incorporated into microbial biomass or respired to CO2 and ultimately emitted into the atmosphere. Thus, understanding the interaction of biodegradable DOM and its consumers is crucial to increase our knowledge on the role of lakes in the global carbon cycling. However, interactions of specific aquatic DOM signatures and the microbial population still remain widely debated. The aim of this study was to explore how DOM biodegradability changes along a stream-lake continuum at different seasons of the year. We monitored DOM quantity and its optical properties, inorganic nutrients, CO2 and bacterial growth over 20 days in dark bioassays with water from the inflow, outflow and at three layers of an oligotrophic subalpine lake. Preliminary results reveal highest microbial abundance in the metalimnion in winter and summer (0.7 106 and 2.5 106 cells mL-1, respectively) and the inflow in spring and autumn (1 106 and 1.4 106 cells mL-1, respectively) after 20 days. Surprisingly, with the exception of winter samples final inflow bacterial abundance results high, despite its lowest initial natural cell concentration, providing evidence for effective utilisation of terrestrial DOM, even with its high humic signature as indicated by the humification index (HIX). Nonetheless, after a microbial biomass peak with the inflow yielding mostly highest after three days, at the final experimental stage microbial biomass does only marginally differ between all sites with the exception of autumn samples where outflow and metalimnion turn out most productive. Even though the DOM of all lake sites and the lake outflow were characterised by lower molecular weight (indicated by the slope ratio (SR)) and a higher autochthonous signature (BIX) in all seasons, rapid growth of inflow bacteria highlight the potential of terrestrially-derived DOM to support bacterial growth, and challenge previous ideas that autchthonously-produced DOM would be more labile than DOM of terrestrial origin.

Timing and Mechanisms of Exhumation in West Central Sulawesi, Indonesia

NASA Astrophysics Data System (ADS)

Hennig, J.; Hall, R.; Watkinson, I. M.; Forster, M.

2012-12-01

New U-Pb and 40Ar/39Ar ages from basement and intrusive rocks from NW Sulawesi record Neogene deformation, much younger than expected, and rapid exhumation. The unusual K-shape of Sulawesi reflects a complex tectonic history in the convergent zone between the Australian, Eurasian and Philippine Sea plates. The Neck is only a few tens of kilometres wide but includes mountains up to 2.5 km high, separating the 2 km deep Gorontalo Bay from similar depths of the Makassar Straits. It represents the Mesozoic-Cenozoic Sundaland continental margin and includes numerous granitoid intrusions. Little is known about the basement protoliths, timing of deformation or causes of magmatic activity. New models propose an important role for extension, associated with rollback of the Banda and North Sulawesi subduction zones. The major NNW-trending Palu-Koro strike-slip fault exhumes ultra high-pressure rocks and granitoids and may be related to North Sulawesi subduction. Work in progress on central Sulawesi's granitic basement orthogneisses shows that zircons dated by U-Pb LA-ICPMS contain Proterozoic inherited cores, and Devonian, Permo-Triassic and Jurassic zircon populations, which suggest an Australian-derived terrane. Basement rocks of the Palu Metamorphic Complex (PMC) were also thought to have Permo-Triassic protoliths and were previously suggested to represent the upper plate of a late Mesozoic subduction zone. Schistose rocks of the PMC have a complex history of metamorphism, crystal growth and deformation. Aluminium silicate porphyroblasts were interpreted as the product of contact metamorphism around granitic intrusions. However, pre-kinematic cordierite, andalusite porphyroblasts and muscovite pseudomorphs after staurolite in the complex indicate a regional high temperature-low pressure metamorphic event. The schists are strongly mylonitized, and overprinted by an S-C fabric recording several generations of biotite and some muscovite growth. 40Ar/39Ar thermochronology reveals a Pliocene cooling age. Further dating of biotites, white mica and amphiboles from schists and amphibolite intercalations is ongoing to determine the history of mylonitic deformation. Temperature-age plots using U-Pb zircon dating, and 40Ar/39Ar and (U-Th)/He geochronological techniques on biotites and apatites from granitic rocks, define thermal histories for the intrusions. Granites from the Neck and the mountain range west of the Palu-Koro Fault have approximately Late Miocene crystallisation ages as indicated by LA-ICPMS and 40Ar/39Ar cooling ages of 7.20 ± 0.05 Ma and 6.41 ± 0.06 Ma. Late-stage exhumation started in the Neck during the Pliocene (AHe: 2.9 ± 0.2 Ma). Erosion rates determined by (U-Th)/He ages can help estimate the amount of sediment input into adjacent deep basins. Age-elevation plots and modelling suggest exhumation rates of 0.75 (-0.16/+0.27) mm/a, which results in a calculated amount of c. 2 km of continental crust that has been removed in the last 3 Myr. We suggest magmatism, metamorphic core complex exhumation, and subsidence of Gorontalo Bay are all related to crustal thinning due to extension driven by subduction rollback.

A DOM Odyssey: The Tale of Molecular Transformations in an Aquifer near Bemidji, MN

NASA Astrophysics Data System (ADS)

Podgorski, D. C.; Zito, P.; Smith, D. F.; Cao, X.; Schmidt-Rohr, K.; Wagner, S.; Stubbins, A.; Aiken, G.; Cozzarelli, I.; Bekins, B. A.; Spencer, R. G.

2017-12-01

Analytical methods including fluorescence spectroscopy, NMR spectroscopy, and ultrahigh resolution mass spectrometry have significantly advanced the understanding of compositional controls on dissolved organic matter (DOM) processing and fate. Yet, we still heavily rely on extrapolation of chemical changes identified at the edges of the compositional continuum (i.e., endmembers) to assess DOM reactivity and stability. While extrapolation of chemical transformations is useful for determining relative changes in DOM composition, a comprehensive understanding of the underlying core structures and composition is required to develop advanced biogeochemical models. Studying DOM from natural systems is complicated by many variables associated with an open system including input from multiple sources, simultaneous photo-alteration and microbial processing, and obtaining samples that cover high spatial and temporal resolution. A 38-year biodegradation study at the National Crude Oil Spill Research site near Bemidji, MN provides a unique opportunity to monitor DOM in a relatively closed system. An extensively characterized 1 m thick oil body is confined to a 25 x 75 m2 area at the water table in the aquifer. Oxidized metabolites partition from the oil into the underlying aquifer increase the DOC concentration to > 100 ppm from < 2 ppm up-gradient from the oil body. This newly produced DOM is comprised of aliphatic compounds with high H/C, low O/C and blue-shifted fluorescence, similar in composition to permafrost- and algal-derived DOM. The aliphatic DOM is transported laterally from the oil pool by groundwater, creating a plume that ultimately discharges into the Unnamed Lake 325 m downgradient. More than 10 years later and hundreds of meters downgradient from the oil body, the DOC concentration has decreased to 3-5 ppm and the DOM is compositionally non-distinct. Microbes have left behind degradation products and selectively preserved compounds that exhibit red-shifted fluorescence and molecular formulas with O/C and H/C similar to those associated with the `island of stability'. Samples collected spatially from the DOM plume between these two endmembers provide sufficient temporal resolution to model both DOC concentration and DOM composition as a result of biodegradation.

Catchment scale molecular composition of hydrologically mobilized dissolved organic matter

NASA Astrophysics Data System (ADS)

Raeke, Julia; Lechtenfeld, Oliver J.; Oosterwoud, Marieke R.; Bornmann, Katrin; Tittel, Jörg; Reemtsma, Thorsten

2016-04-01

Increasing concentrations of dissolved organic matter (DOM) in rivers of temperate catchments in Europe and North Amerika impose new technical challenges for drinking water production. The driving factors for this decadal increase in DOM concentration are not conclusive and changes in annual temperatures, precipitation and atmospheric deposition are intensely discussed. It is known that the majority of DOM is released by few but large hydrologic events, mobilizing DOM from riparian wetlands for export by rivers and streams. The mechanisms of this mobilization and the resulting molecular composition of the released DOM may be used to infer long-term changes in the biogeochemistry of the respective catchment. Event-based samples collected over two years from streams in three temperate catchments in the German mid-range mountains were analyzed after solid-phase extraction of DOM for their molecular composition by ultra-high resolution mass spectrometry (FT-ICR MS). Hydrologic conditions, land use and water chemistry parameters were used to complement the molecular analysis. The molecular composition of the riverine DOM was strongly dependent on the magnitude of the hydrologic events, with unsaturated, oxygen-enriched compounds being preferentially mobilized by large events. This pattern is consistent with an increase in dissolved iron and aluminum concentrations. In contrast, the relative proportions of nitrogen and sulfur bearing compounds increased with an increased agricultural land use but were less affected by the mobilization events. Co-precipitation experiments with colloidal aluminum showed that unsaturated and oxygen-rich compounds are preferentially removed from the dissolved phase. The precipitated compounds thus had similar chemical characteristics as compared to the mobilized DOM from heavy rain events. Radiocarbon analyses also indicated that this precipitated fraction of DOM was of comparably young radiocarbon age. DOM radiocarbon from field samples showed that also the event-mobilized DOM had higher radiocarbon content. Overall, hydrology not only controls the quantity of exported carbon from temperate catchments but also strongly influences the molecular composition by mobilizing distinct compound classes in conjunction with dissolved iron and aluminum. From these results future compositional changes in temperate river DOM can be assessed, given an expected increase in the magnitude of hydrologic events, and technical advice for drinking water production may be inferred.

Molecular and optical properties of tree-derived dissolved organic matter in throughfall and stemflow from live oaks and eastern red cedar

NASA Astrophysics Data System (ADS)

Stubbins, Aron; Silva, Leticia M.; Dittmar, Thorsten; Van Stan, John T.

2017-03-01

Studies of dissolved organic matter (DOM) transport through terrestrial aquatic systems usually start at the stream. However, the interception of rainwater by vegetation marks the beginning of the terrestrial hydrological cycle making trees the headwaters of aquatic carbon cycling. Rainwater interacts with trees picking up tree-DOM, which is then exported from the tree in stemflow and throughfall. Stemflow denotes water flowing down the tree trunk, while throughfall is the water that drips through the leaves of the canopy. We report the concentrations, optical properties (light absorbance) and molecular signatures (ultrahigh resolution mass spectrometry) of tree-DOM in throughfall and stemflow from two tree species (live oak and eastern red cedar) with varying epiphyte cover on Skidaway Island, Savannah, Georgia, USA. Both stemflow and throughfall were enriched in DOM compared to rainwater, indicating trees were a significant source of DOM. The optical and molecular properties of tree-DOM were broadly consistent with those of DOM in other aquatic ecosystems. Stemflow was enriched in highly colored DOM compared to throughfall. Elemental formulas identified clustered the samples into three groups: oak stemflow, oak throughfall and cedar. The molecular properties of each cluster are consistent with an autochthonous aromatic-rich source associated with the trees, their epiphytes and the microhabitats they support. Elemental formulas enriched in oak stemflow were more diverse, enriched in aromatic formulas, and of higher molecular mass than for other tree-DOM classes, suggesting greater contributions from fresh and partially modified plant-derived organics. Oak throughfall was enriched in lower molecular weight, aliphatic and sugar formulas, suggesting greater contributions from foliar surfaces. While the optical properties and the majority of the elemental formulas within tree-DOM were consistent with vascular plant-derived organics, condensed aromatic formulas were also identified. As condensed aromatics are generally interpreted as deriving from partially combusted organics, some of the tree-DOM may have derived from the atmospheric deposition of thermogenic and other windblown organics. These initial findings should prove useful as future studies seek to track tree-DOM across the aquatic gradient from canopy roof, through soils and into fluvial networks.

Similarities in Photodegradation of Cyanobacteria-Derived and Marine Fluorescent Dissolved Organic Matter

NASA Astrophysics Data System (ADS)

Ianiri, H. L.; Timko, S.; Gonsior, M.

2016-02-01

Marine dissolved organic matter (DOM) is one of the largest reduced carbon reservoirs on Earth, yet we only have a limited understanding of its production, cycling, degradation, and overall structure. It was previously believed that a significant portion of refractory dissolved organic carbon (RDOC) in the ocean was derived from terrestrial sources, however recent studies indicated that the majority of marine DOM might be produced in situ by marine biota. Previous research has found that terrestrial and microbial DOM fluorescent signatures are similar, complicating the identification of the origins of marine fluorescent DOM (FDOM). However, photodegradation kinetics of terrestrial and microbial-derived DOM are expected to be different due to their assumed different chemical compositions. In this study we analyzed for the first time the photodegradation kinetics of microbial-derived DOM originating from different cyanobacteria strains. Cyanobacterial-derived DOM were exposed to simulated sunlight for a total of 20 hours while recording excitation emission matrix (EEM) fluorescence every twenty minutes to observe the photodegradation of this specific FDOM. Parallel Factor Analysis (PARAFAC) was applied to deconvolute the EEM matrices into six separate components. The photodegradation kinetics was then calculated for each component and compared with previously obtained photodegradation data of marine and terrestrial FDOM. This six component PARAFAC model was similar to those generated from open ocean data and global DOM data sets. The "humic-like" FDOM was also found in cyanobacteria FDOM and showed similar fluorescence intensities and percent fluorescence loss when compared to marine DOM. The degradation kinetics of the "humic-like" component of microbial-derived DOM was faster than that of terrestrial-derived DOM, and marine FDOM samples showed degradation kinetics more similar to microbial-derived FDOM. This indicates marine FDOM is more similar in chemical composition to microbial-derived FDOM than terrestrial-derived FDOM, supporting the hypothesis that the majority of marine FDOM is produced in situ.

Export of pre-aged, labile DOM from a central California coastal upwelling system: Insights from D/L amino acids and Δ14C signatures

NASA Astrophysics Data System (ADS)

Walker, B. D.; Shen, Y.; Benner, R. H.; Druffel, E. R. M.

2014-12-01

Coastal upwelling zones are among the most productive regions in the world and play a major role in global carbon and nitrogen cycles. Recent research suggests that a substantial fraction of newly fixed organic matter is exported offshore in the form of dissolved organic matter (DOM). However, to date only a few studies have examined DOM composition in the context of production and export from upwelling systems. The ultimate fate and geochemical impact of coastal DOM exported to offshore and mesopelagic ecosystems also remains largely unknown. Between 2007-2009 we conducted a high-resolution biogeochemical time series at the Granite Canyon Marine Pollution Studies Lab in part to evaluate the seasonal production and export of DOM from the Central CA coast. Our previous work demonstrated substantial, albeit disparate, seasonal production of dissolved organic carbon and nitrogen (DOC, DON) - with high DON (and low C:N ratios) produced during upwelling and high DOC produced during summer/fall water column stratification (Walker and McCarthy, 2012). Here we present new total dissolved D/L amino acid (TDAA) and UV-oxidizable DOC radiocarbon (Δ14C) data with the goal of determining the relative sources (heterotrophic vs. autotrophic), bioavailability, microbial processing and 14C-ages of C-rich vs. N-rich DOM exported from this upwelling system. Our results suggest that C-rich DOM produced during water column stratification carries a large microbial signature (i.e. high D/L AA ratios and non-protein AA abundance), whereas N-rich DOM produced during upwelling appears to be fresh, autotrophic DOM (i.e. lowest D/L AA ratios and highest TDAA abundance). DOM Δ14C signatures also did not approximate in situ dissolved inorganic carbon (DIC), and instead were far more negative and highly correlated to water mass density. Together our results indicate a previously unrecognized source of highly labile yet pre-aged DOM potentially impacting offshore and mesopelagic ecosystems.

Trials and Tribulations of Fluorescent Dissolved Organic Matter Chemical Interpretations: A case study of polar ice cores

NASA Astrophysics Data System (ADS)

D'Andrilli, J.

2017-12-01

Excitation emission matrix fluorescence spectroscopy is widely applied for rapid dissolved organic matter (DOM) characterization in aquatic systems. Fluorescent DOM surveys are booming, not only as a central focus in aquatic environments, but also as an important addition to interdisciplinary research (e.g., DOM analysis in concert with ice core paleoclimate reconstructions, stream metabolism, hydrologic regimes, agricultural developments, and biological activity), opening new doors, not just for novelty, but also for more challenges with chemical interpretations. Recently, the commonly used protein- versus humic-like classifications of DOM have been ineffective at describing DOM chemistry in various systems (e.g., ice cores, wastewaters, incubations/engineered). Moreover, the oversimplification of such classifications used to describe fluorescing components, without further scrutiny, has become commonplace, ultimately producing vague reporting. For example, West Antarctic ice core DOM was shown to contain fluorescence in the low excitation/emission wavelength region, however resolved fluorophores depicting tyrosine- and tryptophan-like DOM were not observed. At first, as literature suggested, we reported this result as protein-like, and concluded that microbial contributions were dominant in deep ice. That initial interpretation would disintegrate the conservation paradigm of atmospheric composition during deposition, the crux of ice core research, and contradict other lines of evidence. This begged the question, "How can we describe DOM chemistry without distinct fluorophores?" Antarctic ice core DOM was dominated by neither tyrosine- nor tryptophan-like fluorescence, causing "unusual" looking fluorescent components. After further examination, deep ice DOM was reported to contain fluorescent species most similar to monolignols and tannin-like phenols, describing the precursors of lignin from low carbon producing environments, consistent with marine sediment records. Currently, we are working towards more detailed descriptions of fluorescence, thus accepting variation in and around protein- and humic-like regions, and achieving robust chemical interpretations of DOM chemistry, ultimately providing insight to its interwoven nature in the environment.

Different effects of plant-derived dissolved organic matter (DOM) and urea on the priming of soil organic carbon.

PubMed

Qiu, Qingyan; Wu, Lanfang; Ouyang, Zhu; Li, Binbin; Xu, Yanyan

2016-03-01

Soil organic carbon (SOC) mineralization is important for the regulation of the global climate and soil fertility. Decomposition of SOC may be significantly affected by the supply of plant-derived labile carbon (C). To investigate the impact of plant-derived dissolved organic matter (DOM) and urea (N) additions on the decomposition of native SOC as well as to elucidate the underlying mechanisms of priming effects (PEs), a batch of incubation experiments was conducted for 250 days by application of (13)C-labeled plant-derived DOM and urea to soils. The direction of PE induced by the addition of DOM was different from the addition of N, i.e. it switched from negative to positive in DOM-amended soils, whereas in the N-treated soil it switched from positive to negative. Adding DOM alone was favorable for soil C sequestration (59 ± 5 mg C per kg soil), whereas adding N alone or together with DOM accelerated the decomposition of native SOC, causing net C losses (-62 ± 4 and -34 ± 31 mg C per kg soil, respectively). These findings indicate that N addition and its interaction with DOM are not favorable for soil C sequestration. Adding DOM alone increased the level of dissolved organic carbon (DOC), but it did not increase the level of soil mineral N. Changes in the ratio of microbial biomass carbon (MBC) to microbial biomass nitrogen (MBN) and microbial metabolic quotient (qCO2) after the addition of DOM and N suggest that a possible shift in the microbial community composition may occur in the present study. Adding DOM with or without N increased the activities of β-glucosidase and urease. Changes in the direction and magnitude of PE were closely related to changes in soil C and N availability. Soil C and N availability might influence the PE through affecting the microbial biomass and extracellular enzyme activity as well as causing a possible shift in the microbial community composition.

Dissolved organic matter and aluminum oxide nanoparticles synergistically cause cellular responses in freshwater microalgae.

PubMed

Ye, Nan; Wang, Zhuang; Wang, Se; Fang, Hao; Wang, Degao

2018-06-07

This study investigated the impact of dissolved organic matters (DOM) on the ecological toxicity of aluminum oxide nanoparticles (Al 2 O 3 NPs) at a relatively low exposure concentration (1 mg L -1 ). The unicellular green alga Scenedesmus obliquus was exposed to Al 2 O 3 NP suspensions in the presence of DOM (fulvic acid) at various concentrations (1, 10, and 40 mg L -1 ). The results show that the presence of DOM elevated the growth inhibition toxicity of Al 2 O 3 NPs towards S. obliquus in a dose-dependent manner. Moreover, the combination of DOM at 40 mg L -1 and Al 2 O 3 NPs resulted in a synergistic effect. The relative contribution of Al-ions released from Al 2 O 3 NPs to toxicity was lower than 5%, indicating that the presence of the particles instead of the dissolved ions in the suspensions was the major toxicity sources, regardless of the presence of DOM. Furthermore, DOM at 10 and 40 mg L -1 and Al 2 O 3 NPs synergistically induced the upregulation of intercellular reactive oxygen species levels and superoxide dismutase activities. Analysis of the plasma malondialdehyde concentrations and the observation of superficial structures of S. obliquus indicated that the mixtures of DOM and Al 2 O 3 NPs showed no significant effect on membrane lipid peroxidation damage. In addition, the presence of both DOM and Al 2 O 3 NPs contributed to an enhancement in both the mitochondrial membrane potential and the cell membrane permeability (CMP) in S. obliquus. In particular, Al 2 O 3 NPs in the presence of 10 and 40 mg L -1 DOM caused a greater increase in CMP compared to Al 2 O 3 NPs and DOM alone treatments. In conclusion, these findings suggest that DOM at high concentrations and Al 2 O 3 NPs synergistically interrupted cell membrane functions and triggered subsequent growth inhibition toxicity.

Oligotrophic wetland sediments susceptible to shifts in microbiomes and mercury cycling with dissolved organic matter addition

PubMed Central

Gabor, Rachel S.; Schooler, Shon; McKnight, Diane M.; Knelman, Joseph E.

2018-01-01

Recent advances have allowed for greater investigation into microbial regulation of mercury toxicity in the environment. In wetlands in particular, dissolved organic matter (DOM) may influence methylmercury (MeHg) production both through chemical interactions and through substrate effects on microbiomes. We conducted microcosm experiments in two disparate wetland environments (oligotrophic unvegetated and high-C vegetated sediments) to examine the impacts of plant leachate and inorganic mercury loadings (20 mg/L HgCl2) on microbiomes and MeHg production in the St. Louis River Estuary. Our research reveals the greater relative capacity for mercury methylation in vegetated over unvegetated sediments. Further, our work shows how mercury cycling in oligotrophic unvegetated sediments may be susceptible to DOM inputs in the St. Louis River Estuary: unvegetated microcosms receiving leachate produced substantially more MeHg than unamended microcosms. We also demonstrate (1) changes in microbiome structure towards Clostridia, (2) metagenomic shifts toward fermentation, and (3) degradation of complex DOM; all of which coincide with elevated net MeHg production in unvegetated microcosms receiving leachate. Together, our work shows the influence of wetland vegetation in controlling MeHg production in the Great Lakes region and provides evidence that this may be due to both enhanced microbial activity as well as differences in microbiome composition. PMID:29632744

Comparison of the Discriminative Stimulus Effects of Dimethyltryptamine with Different Classes of Psychoactive Compounds in Rats

PubMed Central

Gatch, Michael B.; Rutledge, Margaret A.; Carbonaro, Theresa; Forster, Michael J.

2010-01-01

Rationale There has been increased recreational use of dimethyltryptamine (DMT), but little is known of its discriminative stimulus effects. Objectives The present study assessed the similarity of the discriminative stimulus effects of DMT to other types of hallucinogens and to psychostimulants. Methods Rats were trained to discriminate DMT from saline. To test the similarity of DMT to known hallucinogens, the ability of (+)-lysergic acid diethylamide (LSD), (−)-2,5-dimethoxy-4-methylamphetamine (DOM), (+)-methamphetamine, or (±)3,4-methylenedioxymethyl-amphetamine (MDMA) to substitute in DMT-trained rats was tested. The ability of DMT to substitute in rats trained to discriminate each of these compounds was also tested. To assess the degree of similarity in discriminative stimulus effects, each of the compounds was tested for substitution in all of the other training groups. Results LSD, DOM, and MDMA all fully substituted in DMT-trained rats, whereas DMT fully substituted only in DOM-trained rats. Full cross-substitution occurred between DMT and DOM, LSD and DOM, and (+)-methamphetamine and MDMA. MDMA fully substituted for (+)-methamphetamine, DOM, and DMT, but only partially for LSD. In MDMA-trained rats, LSD and (+)-methamphetamine fully substituted, whereas DMT and DOM did not fully substitute. No cross-substitution was evident between (+)-methamphetamine and DMT, LSD, or DOM. Conclusions DMT produces discriminative stimulus effects most similar to those of DOM, with some similarity to the discriminative stimulus effects of LSD and MDMA. Like DOM and LSD, DMT seems to produce predominately hallucinogenic-like discriminative stimulus effects and minimal psychostimulant effects, in contrast to MDMA which produced hallucinogen- and psychostimulant-like effects. PMID:19288085

Dissolved organic matter (DOM) in pore water of Arctic Ocean sediments: linking DOM molecular composition with microbial community structure

NASA Astrophysics Data System (ADS)

Rossel, P. E.; Bienhold, C.; Boetius, A.; Dittmar, T.

2016-02-01

Marine organic matter (OM) that sinks from surface waters to the seafloor is the energy and carbon source for benthic communities. These communities produce dissolved organic matter (DOM) in the process of remineralization, enriching the sediment porewater with fresh DOM compounds. In the Arctic Ocean, primary production is limited by nutrients and light and is thus strongly influenced by sea ice cover. Ice cover is expected to further decrease due to global warming, which may have important consequences for primary production and the quantity and quality of OM exported to the seafloor. This study focused on: 1) the molecular composition of the DOM in sediment pore waters of the deep Eurasian Arctic basins, 2) whether there is any relation between Arctic Ocean ice cover and DOM composition and 3) whether the DOM composition correlates with microbial community structure. Molecular data, obtained via 15 Tesla Fourier transform ion cyclotron resonance mass spectrometry, were statistically correlated with environmental parameters. The productive ice margin stations showed higher abundances of molecular formulae of peptides, unsaturated aliphatics and saturated fatty acids. This molecular trend is indicative of fresh OM and phytodetritus deposition, compared to the northernmost, ice-covered stations which had stronger aromatic signals. Benthic bacterial community structure, as assessed with the fingerprinting method ARISA, was significantly correlated with DOM molecular composition. Further analyses using Illumina next-generation sequencing will enable the taxonomic identification of specific bacterial groups and their interdependence with DOM compounds. This study contributes to the understanding of the coupling between Arctic Ocean productivity and its depositional regime, and provides first insights into potential links between microbial community structure and DOM molecular composition in Arctic sediments

Assessment of the content, structure, and source of soil dissolved organic matter in the coastal wetlands of Jiaozhou Bay, China

NASA Astrophysics Data System (ADS)

Xi, Min; Zi, Yuanyuan; Wang, Qinggai; Wang, Sen; Cui, Guolu; Kong, Fanlong

2018-02-01

The contents and the spectral analysis of dissolved organic matter (DOM) in four typical wetlands, such as naked tidal, suaeda salsa, reed and spartina, were conducted to investigate the content, structure, and source of DOM in coastal wetland soil. The soil samples were obtained from Jiaozhou Bay in January, April, July, and October of 2014. Results showed that the DOM contents in soil of four typical wetland were in order of spartina wetland > naked tidal > suaeda salsa wetland > reed wetland in horizontal direction, and decreased with the increase of soil depth on vertical section. In addition, the DOM contents changed with the seasons, in order of spring > summer > autumn > winter. The structural characteristics of DOM in Jiaozhou Bay wetland, such as aromaticity, hydrophobicity, molecular weight, polymerization degree of benzene ring carbon frame structure and so on were in order of spartina wetland > naked tidal > suaeda salsa wetland > reed wetland in the horizontal direction. On the vertical direction, they showed a decreasing trend with the increase of soil depth. The results of three dimensional fluorescence spectra and fluorescence spectrum parameters (FI, HIX, and BIX) indicated that the DOM in Jiaozhou Bay was mainly derived from the biological activities. The contents and structure of DOM had certain relevance, but the contents and source as well as the structure and source of DOM had no significant correlation. The external pollution including domestic sewage, industrial wastewater, and aquaculture sewage affected the correlation among the content, structure and source of DOM by influencing the percentage of non-fluorescent substance in DOM and disturbing the determination of protein-like fluorescence.

On the timing of high-pressure metamorphism in Alpine Corsica: the first Lu-Hf garnet and lawsonite ages

NASA Astrophysics Data System (ADS)

Vitale Brovarone, A.; Herwartz, D.; Castelli, D.; Malavieille, J.

2012-04-01

Timing of HP metamorphism in Alpine Corsica is highly debated. Controversial biostratigraphic and radiometric constraints results in a poor understanding of the evolution of Alpine Corsica and its meaning in the Western Mediterranean dynamics. Age estimates provided by means of several techniques (e.g. Ar-Ar, Sa-Nd, U-Pb) vary form Late Cretaceous to Late Eocene. Some authors favor a Late Cretaceous peak metamorphism under HP conditions followed by Late Eocene and Early Oligocene blueschist and greenschist retrogression, respectively. Others favor a Late Eocene peak metamorphism and consider the older estimates as affected by analytical inaccuracy. In order to unravel this debate, we provide new Lu-Hf constraints on garnet and lawsonite from the lawsonite-eclogite and lawsonite-blueschist units of Alpine Corsica, which represent a part of the so-called Schistes Lustrés complex. The two investigated units are interpreted to represent remnants of the former Corsican ocean-continent transition zone [2]. As Lu concentrates in the cores of the selected minerals during the early stages of growth and blocking temperatures are high, this method provides robust insight on the timing of prograde/peak metamorphism [1]. Garnet and lawsonite separated form three lawsonite-eclogite samples yield systematic Late Eocene ages at ~ 34 Ma, while lawsonite from the lawsonite-blueschist unit yields a slightly older age at ~ 37 Ma. These data are in agreement with U-Pb data on zircon from the lawsonite-eclogite unit (~ 34 Ma) [3], but are in contrast with a recent U-Pb estimate on the Corsican continental margin unit metamorphosed under blueschist condition, yielding an age of ~ 55 Ma [4]. These discrepancies indicate a complex paleogeographic setting and a diachronous metamorphic evolution along the Corsican ocean-continent transition zone. The Late Eocene HP metamorphism in the Schistes Lustrés of Alpine Corsica also provides important constraints in the evolution of the Alps-Apennine system and the surrounding Western Mediterranean area. [1] Skora, S., Baumgartner, L.P., Mahlen, N.J., Lapen, T.J., Johnson, C.M., Bussy, F. 2008. Estimation of a maximum Lu diffusion rate in a natural eclogite garnet. Swiss J. Geosci. DOI: 10.1007/s00015-008-1268-y. [2] Vitale Brovarone, A., Beltrando, M., Malavieille, J., Giuntoli, F, Tondella, E, Groppo, C., Beyssac, O. and Compagnoni, R., 2011a. Inherited Ocean-Continent Transition zones in deeply subducted terranes: Insights from Alpine Corsica, Lithos, doi: 10.1016/j.lithos.2011.02.013. [3] Martin., L., Rubatto, D., Vitale Brovarone, A., Hermann, J. 2011. Late Eocene lawsonite-eclogite facies metasomatism of a granulite sliver associated to ophiolites in Alpine Corsica. Lithos, doi:10.1016/j.lithos.2011.03.015 [4] Maggi M, Rossetti F, Theye T, Andersen T, Corfu F, Faccenna C. Sodic Pyroxene Bearing Phyllonites From the East Tenda Shear Zone: Constraining P-T Conditions and Timing of the Ligurian-Piemontese Ocean Overthrusting Onto the Variscan Corsica. Abstract Corsealp 2011. Saint Florent, Corsica, France.

Constraining metamorphic rates through allanite and monazite petrochronology: a case study from the Miyar Valley (High Himalayan Crystalline of Zanskar, NW India)

NASA Astrophysics Data System (ADS)

Robyr, Martin; Goswami-Banerjee, Sriparna

2014-05-01

Dating metamorphic rocks raises specific issues because metamorphism comprises a complex sequence of structural changes and chemical reactions that can be extended over millions or tens of millions of years so that metamorphic rocks cannot in general be said to have "an age". Therefore, an accurate interpretation of radiometric age data from metamorphic rocks requires first to establish the behavior of the isotopic system used for dating relative to the pressure and temperature (P-T) conditions that a metamorphic rock experienced. As the U-Th-Pb system in LREE-accessory phases like monazite and allanite is not easily reset during subsequent temperature increase, allanite and monazite U-Th-Pb ages are collectively interpreted as reflecting crystallization ages. As a consequence, to correctly interpret allanite and monazite crystallization ages, it is essential to accurately determine the physical conditions of their crystallization. A meticulous account of the chemical and textural evolution of monazite and allanite along a well constrained prograde pelitic sequence of the High Himalayan Crystalline of Zanskar (Miyar Valley; e.g. Robyr et al., 2002; 2006; 2014) reveals that: (1) the occurrence of the first metamorphic allanite coincides with the biotite-in isograd and (2) the formation of the first metamorphic monazite occurs at the staurolite-in isograd. The finding of both monazite and allanite as inclusion in staurolite porphyroblasts indicates that the breakdown of allanite and the formation of monazite occurred during staurolite crystallization. Thermobarometry results show that the metamorphic allanites are appeared in the 400-420 °C, while the signature of the first metamorphic monazite is found at ~ 600 °C with staurolite-in isograd. Allanite and monazite U-Th-Pb ages thus constrain the timing when the rocks reached the ~ 420 °C and ~ 600 °C isotherms respectively. In situ LA-ICPMS dating of coexisting allanite and monazite inclusions in garnet porphyroblasts yield respective ages of 33.6 ± 0.9 Ma and 29.5 ± 0.2 Ma, constraining the time elapsed between allanite crystallization (~ 420 °C) and monazite crystallization (~ 600°C). These data indicate that the rock needed ~ 4 Myr to be subducted from the 420 °C isotherm down to the 600°C isotherm, implying a heating rate of ca. 45°C/m.y. References Robyr, M., Epard, J.-L. & El Korh, A., 2014. Structural, metamorphic and geochronological relations between the Zanskar Shear Zone and the Miyar Shear Zone (NW Indian Himalaya): Evidence for two distinct tectonic structures and implications for the evolution of the High Himalayan Crystalline of Zanskar. Journal of Asian Earth Sciences, 79, 1-15. Robyr, M., Hacker, B. R. & Mattinson, J. M., 2006. Doming in compressional orogenic settings: New geochronological constraints from the NW Himalaya. Tectonics, 25. Robyr, M., Vannay, J. C., Epard, J. L. & Steck, A., 2002. Thrusting, extension, and doming during the polyphase tectonometamorphic evolution of the High Himalayan Crystalline Zone in NW India. Journal of Asian Earth Sciences, 21, 221-239.

Thermobarometric and fluid expulsion history of subduction zones

NASA Astrophysics Data System (ADS)

Ernst, W. G.

1990-06-01

Phanerozoic, unmetamorphosed, weathered, and altered lithotectonic complexes subjected to subduction exhibit the prograde metamorphic facies sequence: zeolite → prehnite-pumpellyite → glaucophane schist → eclogite. Parageneses reflect relatively high-P trajectories, accompanied by semicontinuous devolatilization. The thermal evolution of convergent plate junctions results in early production of high-rank blueschists, high-P amphibolites, and eclogues at depth within narrow subduction zones while the hanging wall lithosphere is still hot. Protracted underflow drains heat from the nonsubducted plate and, even at profound depths, generates very low-T/high-P parageneses. Inclusion studies suggest that two-phase immiscible volatiles (liquid H2O, and gaseous high-hydrocarbons, CH4 and CO2) are evolved in turn during progressive metamorphism of the subducted sections. Expulsion of pore fluids and transitions from weathered and altered supracrustal rocks to zeolite facies assemblages release far more fluid than the better understood higher-grade transformations. Many blueschist parageneses, such as those of the internal Western Alps, have been partially overprinted by later greenschist and/or epidote-amphibolite facies assemblages. Alpine-type postblueschist metamorphic paths involved fairly rapid, nearly adiabatic decompression; some terranes even underwent modest continued heating and fluid evolution during early stages of ascent. Uplift probably occurred as a consequence of the underthrusting of low-density island arc or microcontinental crust along the convergent plate junction, resulting in marked deceleration or cessation of lithospheric underflow, decoupling, and nearly isothermal rise of the recrystallized subduction complex. Other, less common blueschist terranes, such as the eastern Franciscan belt of western California, preserve metamorphic aragonite and other high-P minerals, and lack a low-pressure overprint; physical conditions during retrogression approximately retraced the prograde path or, for early formed high-grade blocks, reflect somewhat higher pressures and lower temperatures. Subducted sections constituting portions of the Franciscan-type of metamorphic belt evidently moved slowly back up the inclined lithospheric plate junction during continued convergence and sustained refrigeration. Upward motion due to isostatic forces was produced by tectonic imbrication of fault suces, laminar return flow in melange zones, and lateral extension of the underplated accretionary prism. The ease with which volatiles are expelled from a subduction complex and migrate upward along the plate junction zone is roughly proportional to the sandstone/shale ratio: low-permeability mudstones tend to maintain fluid values approaching lithostatic, lose strength, and deform chaotically (forming melange belts), whereas permeable sandstone-rich sections retain structural/stratigraphic coherence and fail brittlely (forming coherent terranes). Because of substantial updip expulsion of volatiles during prograde recrystallization, only small amounts of H2O and CO2 are available to support hydration and carbonation of the accretionary complex during its return toward the surface; thus limited back reaction takes place and occurs at low Pfluid/Plithostatic ratios, unless an abundance of volatiles is introduced during uplift.

Mineralization related to Alvand pluton in the Hamadan, western Iran

NASA Astrophysics Data System (ADS)

Salehi, M. H.; Doosti, E. A.; Ahadnejad, V.

2009-04-01

The Alvand (Hamadan) plutonic batholith is one of the largest plutonic bodies in the Sanandaj-Sirjan metamorphic belt. This complex is consist of mafic part (gabbro-diorite-tonalite), intermediate (granite-granodiorite porphyroids), and hololeucocratic granitoids. Previous studies have shown that S-type granite-granodiorites are mostly peraluminous and calc-alkaline; the gabbro-diorite-tonalite suite is mostly metaluminous and tholeiitic to calc-alkaline (Sepahi, 2008). High initial 87Sr-86Sr ratios (0.7081 to 0.7115), low epsilon Nd values (-1.0 to -3.3), and peraluminous character reflects a different origin for the granites, possibly crustal sources (Ghalamghash et al, 2007). Aplite-pegmatite dikes are intruded in granitoide rocks, metamorphic rocks and the contact of Alvand granite with metamorphic rocks. The contact of Alvand granite with metamorphic rocks is sharp. By using heavy mineral studies on the alluvium of Alvand complex, it is recognized 28 minerals amongst Scheelite, Cassiterite, Ilmenite, Zircon and Garnet. Different geostatistical studies such as variant, bivariant and multivariant studies have been done on rough data of heavy minerals. They showed normal concentration of gold in studied rocks and low enrichment of tin and tungsten. The index of the ore elements average, frequeney distribution criteria of elements, the ratio of elements index and multielements show that Alvand granite is barren. Mineralography studies did not recognized any tin and tungsten minerals. The grains of gold was recognized in some of the microscopic thin sections. Calcopyrotite is the most important ore mineral that is accompanied with oxides and iron carbonates. The contacts of aplite-pegmatite dikes with granitoide rocks mostly are not prolific. For recognizing Scheelite, some samples of rocks studied by ultraviolet and few Scheelite is recognized in the samples. Some alteration zone observed in this area but they are not accompany with main mineralization. Although the expanded turmalinization has occurred but it is not seen any mineralization. Unless some small part of Alvand complex (i.e. stibnite in the Faghireh area, Maniijou and Aliani, 2000) and based on the main geochemical index, Alvand granitod pluton is classified as a barren type granite. References: Ghalamghash, J., Mirnejad, H., Rashid, H., Mohammadiha, K., Ghahraei-poor, M., Zakeri, M., 2007. Geochemistry of gabbro, granite and mafic enclaves of Alvand batholithe and their origin. 25th conference of geoscinces, Geological Survey of Iran. Maniijou, M., and Aliani, F., 2000. Stibnite mineralization in the Hamedan, west Iran. Mineral Deposits at the Beginning of the 21st Century: Proceedings of the Joint Sixth Biennial SGA-SEG Meeting, Krakow, Poland, 26-29 August 2001 By Adam Piestrzyński, Society for Geology Applied to Mineral Deposits, Society of Economic Geologists (U.S.) Published by Taylor & Francis. ISBN 9026518463, 9789026518461. 1148 pages. Sepahi, Ali A, 2008. Typology and petrogenesis of granitic rocks in the Sanandaj-Sirjan metamorphic belt, Iran: with emphasis on the Alvand plutonic complex. Neues Jahrbuch für Geologie Und Palaeontologie. Abhandlungen, 2008; 247 (3), 295-312.

Solid-state 13C NMR studies of dissolved organic matter in pore waters from different depositional environments

USGS Publications Warehouse

Orem, W.H.; Hatcher, P.G.

1987-01-01

Dissolved organic matter (DOM) in pore waters from sediments of a number of different depositional environments was isolated by ultrafiltration using membranes with a nominal molecular weight cutoff of 500. This > 500 molecular weight DOM represents 70-98% of the total DOM in these pore waters. We determined the gross chemical structure of this material using both solid-state 13C nuclear magnetic resonance spectroscopy and elemental analysis. Our results show that the DOM in these pore waters appears to exist as two major types: one type dominated by carbohydrates and paraffinic structures and the second dominated by paraffinic and aromatic structures. We suggest that the dominance of one or the other structural type of DOM in the pore water depends on the relative oxidizing/reducing nature of the sediments as well as the source of the detrital organic matter. Under dominantly anaerobic conditions carbohydrates in the sediments are degraded by bacteria and accumulate in the pore water as DOM. However, little or no degradation of lignin occurs under these conditions. In contrast, sediments thought to be predominantly aerobic in character have DOM with diminished carbohydrate and enhanced aromatic character. The aromatic structures in the DOM from these sediments are thought to arise from the degradation of lignin. The large amounts of paraffinic structures in both types of DOM may be due to the degradation of unidentified paraffinic materials in algal or bacterial remains. ?? 1987.

Influence of dissolved organic matter and activated carbon pore characteristics on organic micropollutant desorption.

PubMed

Aschermann, Geert; Zietzschmann, Frederik; Jekel, Martin

2018-04-15

By simulating decreasing inflow concentrations, the extent of desorption of organic micropollutants (OMP) from three activated carbons (AC) was examined in laboratory batch tests. The tested AC showed strong differences in pore size distribution and could therefore be characterized as typical micro-, meso- and macroporous AC, respectively. Adsorption and desorption conditions were varied by using drinking water (containing dissolved organic matter (DOM)) and DOM-free pure water as background solutions to examine the influence of DOM on OMP desorption for the different AC. Under ideal conditions (adsorption and desorption in pure water) adsorption of the tested OMP was found to be highly up to completely reversible for all tested AC. Under real conditions (adsorption and desorption in drinking water) additional DOM adsorption affects desorption in different ways depending on the AC pore structure. For the micro- and mesoporous AC, an increased irreversibility of OMP adsorption was found, which shows that DOM adsorption prevents OMP desorption. This could be referred to pore blockage effects that occur during the parallel adsorption of DOM and OMP. For the macroporous AC, DOM adsorption led to an enhanced OMP desorption which could be attributed to displacement processes. These results show that smaller pores tend to be blocked by DOM which hinders OMP from desorption. The overall larger pores of the macroporous AC do not get blocked which could allow (i) OMP to desorb and (ii) DOM to enter and displace OMP. Copyright © 2018 Elsevier Ltd. All rights reserved.

Dominant vs. non-dominant shoulder morphology in volleyball players and associations with shoulder pain and spike speed.

PubMed

Challoumas, Dimitrios; Artemiou, Andreas; Dimitrakakis, Georgios

2017-01-01

The aims of our study were to compare the dominant (DOM) and non-dominant (NDOM) shoulders of high-level volleyball athletes and identify possible associations of shoulder adaptations with spike speed (SS) and shoulder pathology. A total of 22 male volleyball players from two teams participating in the first division of the Cypriot championship underwent clinical shoulder tests and simple measurements around their shoulder girdle joints bilaterally. SS was measured with the use of a sports speed radar. Compared with the NDOM side, the DOM scapula was more lateralised, the DOM dorsal capsule demonstrated greater laxity, the DOM dorsal muscles stretching ability was compromised, and the DOM pectoralis muscle was more lengthened. Players with present or past DOM shoulder pain demonstrated greater laxity in their DOM dorsal capsule, tightening of their DOM inferior capsule, and lower SS compared with those without shoulder pain. Dorsal capsule measurements bilaterally were significant predictors of SS. None of the shoulder measurements was associated with team roles or infraspinatus atrophy, while scapular lateralisation was more pronounced with increasing years of experience, and scapular antetilting was greater with increasing age. Adaptations of the DOM shoulder may be linked to pathology and performance. We describe simple shoulder measurements that may have the potential to predict chronic shoulder injury and become part of injury prevention programmes. Detailed biomechanical and large prospective studies are warranted to assess the validity of our findings and reach more definitive conclusions.

Effects of aeration strategy on the evolution of dissolved organic matter (DOM) and microbial community structure during sludge bio-drying.

PubMed

Zhang, Junya; Cai, Xing; Qi, Lu; Shao, Chunyan; Lin, Yang; Zhang, Jin; Zhang, Yuanli; Shen, Peihong; Wei, Yuansong

2015-09-01

Sludge bio-drying in which sludge is dried by means of the heat generated by the aerobic degradation of its own organic substances has been widely used for sludge treatment. A better understanding of the evolution of dissolved organic matter (DOM) and its degradation drivers during sludge bio-drying could facilitate its control. Aeration is one of the key factors that affect sludge bio-drying performance. In this study, two aeration strategies (pile I-the optimized and pile II-the current) were established to investigate their impacts on the evolution of DOM and the microbial community in a full-scale sludge bio-drying plant. A higher pile temperature in pile I caused pile I to enter the DOM and microbiology stable stage approximately2 days earlier than pile II. The degradation of easily degradable components in the DOM primarily occurred in the thermophilic phase; after that degradation, the DOM components changed a little. Along with the evolution of the DOM, its main degradation driver, the microbial community, changed considerably. Phyla Firmicutes and Proteobacteria were dominant in the thermophilic stage, and genus Ureibacillus, which was the primary thermophilic bacteria, was closely associated with the degradation of the DOM. In the mesophilic stage, the microbial community changed significantly at first and subsequently stabilized, and the genus Parapedobacter, which belongs to Bacteriodetes, became dominant. This study elucidates the interplay between the DOM and microbial community during sludge bio-drying.

Stretching of Hot Lithosphe: A Significant Mode of Crustal Stretching in Southeast Asia

NASA Astrophysics Data System (ADS)

de Montserrat Navarro, A.; Morgan, J. P.; Hall, R.; White, L. T.

2017-12-01

SE Asia roughly covers roughly 15% of the Earth's surface and represents one of the most tectonically active regions in the world, yet its tectonic evolution remains relatively poorly studied and constrained in comparison with other regions. Recent episodes of extension have been associated with sedimentary basin growth and phases of crustal melting, uplift and extremely rapid exhumation of young (<7Ma) metamorphic core complexes. This is recorded by seismic imagery of basins offshore Sulawesi and New Guinea as well as through new field studies of the onshore geology in these regions. A growing body of new geochronological and biostratigraphic data provides some control on the rates of processes. We use two-dimensional numerical models to investigate the evolution of the distinctive extensional basins in SE Asia. Our models suggest that, at the onset of stretching, the lithosphere was considerably hotter than in more typically studied rift settings (e.g. Atlantic opening, East African Rift, Australia-Antarctica opening). High Moho temperatures are key in shaping the architecture of the stretched lithosphere: A) hot and week lower crust fails to transmit the stress and brittle deformation, thus resulting in a strong decoupling between crust and lithospheric mantle; B) the mode of deformation is dominated by the ductile flow and boudinage of lower crust, yielding the exhumation of one-to-several partially molten lower crustal bodies, including metamorphic core complexes; C) continental break-up is often inhibited by the ductile behaviour of the crust, and it is only achieved after considerable cooling of the lithosphere. To better constrain the extension rates in which these basins formed, we compare P-T and cooling paths of lower crustal material in a suite of models with newly available data from the Palu and Malino metamorphic core complexes in Sulawesi, Indonesia.