Preservation of labile organic matter in soils of drained thaw lakes in Northern Alaska

NASA Astrophysics Data System (ADS)

Mueller, Carsten W.; Rethemeyer, Janet; Kao-Kniffin, Jenny; Löppmann, Sebastian; Hinkel, Kenneth; Bockheim, James

2014-05-01

A large number of studies predict changing organic matter (OM) dynamics in arctic soils due to global warming. In contrast to rather slowly altering bulk soil properties, single soil organic matter (SOM) fractions can provide a more detailed picture of the dynamics of differently preserved SOM pools in climate sensitive arctic regions. By the study of the chemical composition of such distinctive SOM fractions using nuclear magnetic resonance spectroscopy (NMR) together with radiocarbon analyses it is possible to evaluate the stability of the major OM pools. Approximately 50-75% of Alaska's Arctic Coastal Plain is covered with thaw lakes and drained thaw lakes that follow a 5,000 yr cycle of development (between creation and final drainage), thus forming a natural soil chronosequence. The drained thaw lakes offer the possibility to study SOM dynamics affected by permafrost processes over millennial timescales. In April 2010 we sampled 16 soil cores (including the active and permanent layer) reaching from young drained lakes (0-50 years since drainage) to ancient drained lakes (3000-5500 years since drainage). Air dried soil samples from soil horizons of the active and permanent layer were subjected to density fractionation in order to differentiate particulate OM and mineral associated OM. The chemical composition of the SOM fractions was analyzed by 13C CPMAS NMR spectroscopy. For a soil core of a young and an ancient drained thaw lake basin we also analyzed the 14C content. For the studied soils we can show that up to over 25 kg OC per square meter are stored mostly as labile, easily degradable organic matter rich in carbohydrates. In contrast only 10 kg OC per square meter were sequestered as presumably more stable mineral associated OC dominated by aliphatic compounds. Comparable to soils of temperate regions, we found small POM (< 20 µm) occluded in aggregated soil structures which differed in the chemical composition from larger organic particles. This was

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.

Microbial control of soil organic matter mineralization responses to labile carbon in subarctic climate change treatments.

PubMed

Rousk, Kathrin; Michelsen, Anders; Rousk, Johannes

2016-12-01

Half the global soil carbon (C) is held in high-latitude systems. Climate change will expose these to warming and a shift towards plant communities with more labile C input. Labile C can also increase the rate of loss of native soil organic matter (SOM); a phenomenon termed 'priming'. We investigated how warming (+1.1 °C over ambient using open top chambers) and litter addition (90 g m -2  yr -1 ) treatments in the subarctic influenced the susceptibility of SOM mineralization to priming, and its microbial underpinnings. Labile C appeared to inhibit the mineralization of C from SOM by up to 60% within hours. In contrast, the mineralization of N from SOM was stimulated by up to 300%. These responses occurred rapidly and were unrelated to microbial successional dynamics, suggesting catabolic responses. Considered separately, the labile C inhibited C mineralization is compatible with previously reported findings termed 'preferential substrate utilization' or 'negative apparent priming', while the stimulated N mineralization responses echo recent reports of 'real priming' of SOM mineralization. However, C and N mineralization responses derived from the same SOM source must be interpreted together: This suggested that the microbial SOM-use decreased in magnitude and shifted to components richer in N. This finding highlights that only considering SOM in terms of C may be simplistic, and will not capture all changes in SOM decomposition. The selective mining for N increased in climate change treatments with higher fungal dominance. In conclusion, labile C appeared to trigger catabolic responses of the resident microbial community that shifted the SOM mining to N-rich components; an effect that increased with higher fungal dominance. Extrapolating from these findings, the predicted shrub expansion in the subarctic could result in an altered microbial use of SOM, selectively mining it for N-rich components, and leading to a reduced total SOM-use. © 2016 John Wiley

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.

Amino Acid Enantiomeric Ratios in Semi-Labile vs. Refractory Dissolved Organic Matter: Implications for a Microbial N Pump

NASA Astrophysics Data System (ADS)

Bour, A. L.; Broek, T.; Gier, E. J.; Mccarthy, M. D.

2016-02-01

Microbes are key moderators in the cycling of marine dissolved organic matter (DOM), most of which remains unidentifiable at the molecular level. A major current question, however, is to what degree heterotrophic bacteria directly mediate C and N sequestration in the deep sea. Amino acids (AA) represent almost all organic N that can be identified at the molecular level, while D-AA enantiomers represent unique source-specific biomarkers for prokaryotes, known to be highly enriched in ocean DOM. If increasing bacterial-sourced material ultimately leads to millennial scale sequestration of refractory DOM (RDOM), then one would expect a clear correlation between bacterial biomarkers and DOM radiocarbon (Δ14C) ages, in particular in the deep sea. Here we directly test this idea for the first time, by measuring D-AA abundance and distribution in isolated Δ14C young vs. old DOM from the central north pacific gyre. We used a coupled ultrafiltration/solid phase extraction approach to isolate semi-labile vs. RDOM, based on known molecular weight and Δ14C age correlations. The Δ14C ages of isolated material ranged from 205-275 ybp for surface semi-labile DOM, to 6680-6740 ybp for deep ocean RDOM. We measured enantiomeric (D/L) AA ratios, as well as AA molar percentages to estimate traditional degradation parameters (DI and RI), in semi-labile vs. RDOM fractions from the surface to deep ocean at HOT, Station ALOHA. We interpret our results in terms of the hypothesis of a microbial N pump, examining the similarity of microbial source signatures (D/L distributions) and calculated organic N contributions from heterotrophic bacteria, in the context of the Δ14C age of each fraction. Finally, we also evaluate these data vs. common AA molar percentage based indices of degradation.

Fraction of organic carbon predicts labile desorption rates of chlorinated organic pollutants in laboratory-spiked geosorbents.

PubMed

Ginsbach, Jake W; Killops, Kato L; Olsen, Robert M; Peterson, Brittney; Dunnivant, Frank M

2010-05-01

The resuspension of large volumes of sediments that are contaminated with chlorinated pollutants continues to threaten environmental quality and human health. Whereas kinetic models are more accurate for estimating the environmental impact of these events, their widespread use is substantially hampered by the need for costly, time-consuming, site-specific kinetics experiments. The present study investigated the development of a predictive model for desorption rates from easily measurable sorbent and pollutant properties by examining the relationship between the fraction of organic carbon (fOC) and labile release rates. Duplicate desorption measurements were performed on 46 unique combinations of pollutants and sorbents with fOC values ranging from 0.001 to 0.150. Labile desorption rate constants indicate that release rates predominantly depend upon the fOC in the geosorbent. Previous theoretical models, such as the macro-mesopore and organic matter (MOM) diffusion model, have predicted such a relationship but could not accurately predict the experimental rate constants collected in the present study. An empirical model was successfully developed to correlate the labile desorption rate constant (krap) to the fraction of organic material where log(krap)=0.291-0.785 . log(fOC). These results provide the first experimental evidence that kinetic pollution releases during resuspension events are governed by the fOC content in natural geosorbents. Copyright (c) 2010 SETAC.

Following The Money: Characterizing the Dynamics of Microbial Ecosystems and Labile Organic Matter in Grassland Soils

NASA Astrophysics Data System (ADS)

Herbert, B. E.; McNeal, K. S.

2006-12-01

The dynamics of soil microbial ecosystems and labile fractions of soil organic matter in grasslands have important implications for the response of these critical ecosystems to perturbations. Organic, inorganic and genetic biomarkers in the solid (e.g. lipids, microbial DNA), liquid (e.g. porewater ions) or gaseous phases (e.g. carbon dioxide) have been used to characterize carbon cycling and soil microbial ecology. These proxies are generally limited in the amount of temporal information that they can provide (i.e., solid-phase proxies) or the amount of specific information they can provide about carbon sources or microbial community processes (e.g. inorganic gases). It is the aim of this research to validate the use of soil volatile organic carbon emissions (VOCs) as useful indicators of subsurface microbial community shifts and processes as a function of ecosystem perturbations. We present results of method validation using laboratory microcosm, where VOC metabolites as characterized by gas chromatography and mass spectrometry (GC-MS), were related to other proxies including carbon dioxide (CO2) via infra-red technology, and microbial community shifts as measured by Biolog© and fatty acid methyl ester (FAME) techniques. Experiments with soil collected from grasslands along the coastal margin region in southern Texas were preformed where environmental factors such as soil water content, soil type, and charcoal content are manipulated. Results indicate that over fifty identifiable VOC metabolites are produced from the soils, where many (~15) can be direct indicators of microbial ecology. Principle component analysis (PCA) evidences these trends through similar cluster patterns for the VOC results, the Biolog© results, and FAME. Regression analysis further shows that VOCs are significant (p < 0.05) indicators of microbial stress. Our results are encouraging that characterizing VOCs production in grassland soils are easy to measure, relatively inexpensive method

Dissolved organic matter in anoxic pore waters from Mangrove Lake, Bermuda

USGS Publications Warehouse

Orem, W.H.; Hatcher, P.G.; Spiker, E. C.; Szeverenyi, N.M.; Maciel, G.E.

1986-01-01

Dissolved organic matter and dissolved inorganic chemical species in anoxic pore water from Mangrove Lake, Bermuda sediments were studied to evaluate the role of pore water in the early diagenesis of organic matter. Dissolved sulphate, titration alkalinity, phosphate, and ammonia concentration versus depth profiles were typical of many nearshore clastic sediments and indicated sulphate reduction in the upper 100 cm of sediment. The dissolved organic matter in the pore water was made up predominantly of large molecules, was concentrated from large quantities of pore water by using ultrafiltration and was extensively tudied by using elemental and stable carbon isotope analysis and high-resolution, solid state 13C nuclear magnetic resonance and infrared spectroscopy. The results indicate that this material has a predominantly polysaccharide-like structure and in addition contains a large amount of oxygen-containing functional groups (e.g., carboxyl groups). The 13C nulcear magnetic resonance spectra of the high-molecular-weight dissolved organic matter resemble those of the organic matter in the surface sediments of Mangrove Lake. We propose that this high-molecular-weight organic matter in pore waters represents the partially degraded, labile organic components of the sedimentary organic matter and that pore waters serve as a conduit for removal of these labile organic components from the sediments. The more refractory components are, thus, selectively preserved in the sediments as humic substances (primarily humin). ?? 1986.

Organic matter degradation in surface sediments of the Changjiang estuary: Evidence from amino acids.

PubMed

Wang, Kui; Chen, Jianfang; Jin, Haiyan; Li, Hongliang; Zhang, Weiyan

2018-05-12

Organic matter degradation is a key component of the processes of carbon preservation and burial in seafloor sediments. The aim of this study was to explore organic matter degradation state within the open-shelf Changjiang Estuary of the East China Sea, using an amino acids-based degradation index (DI) in conjunction with information about organic matter source (marine versus terrestrial), bottom water oxygenation state, and sediment grain size. The relative molar percentages of 17 individual amino acids (characterized using principal component analysis) in surface sediments indicate that organic matter is degraded to varying extents across the estuary seabed. Sediments with DI >0 (relatively labile) were found mostly within a coastal hypoxic area. Sediments of DI less than -1 (relatively refractory) were found near the Changjiang River mouth and the northern and southern parts of the central shelf. We consider DI to be a more reliable indicator of degradation than simple ratios of AAs. DI was inversely correlated with the proportion of terrestrial organic material (F t ) in the sediments, indicating that relatively fresh/labile organic matter was generally associated with marine sources. DI was significantly correlated with F t and bottom water apparent oxygen utilization (AOU bot ) together. The parameter DI and the (labile) amino acid tyrosine were highest in hypoxic areas, suggesting the presence of relatively fresh organic matter, probably due to a combination of marine-source inputs and better preservation of organic matter in the silt and clay sediments of these areas (as compared to sandy sediments). Less degraded organic matter with high amino acids was also favorable to benthic animals. Overall, sedimentary estuarine organic matter was least degraded in areas characterized by marine sources of organic matter, low-oxygen conditions, and fine-grained sediments. Copyright © 2018 Elsevier B.V. All rights reserved.

Mineralization of organic-matter labile fragments in the humus-accumulative horizon of soddy-podzolic soil

NASA Astrophysics Data System (ADS)

Trofimov, S. Ya.; Lazarev, A. S.; Fokin, A. D.

2012-12-01

The mineralization rate of the 14C-labeled organic matter (OM) in the humus-accumulative AE horizon of a soddy-podzolic soil was determined in a laboratory experiment. The labeling was performed in a field experiment when microamounts of 14C-labeled glucose, glycine, and uracil were added to tree waste in sacks embedded in the upper layer of the forest litter. Samples containing 14C were taken from the AE horizon (above which the sacks with the labeled material were placed) 7 and 20 months after the beginning of the experiment. The soil samples were wetted to a water content corresponding to ˜80% of the total water capacity and placed in hermetic vessels containing vials with a periodically renewed alkali solution. The incubation was performed at room temperature for 3.5 months; the alkali solutions in the vials were replaced and titrated 12 times during this period. Mineralization curves were plotted from the amounts of carbon dioxide absorbed by a 0.3 N NaOH solution, which were calculated for each time interval; its 14C content was determined by the scintillation method. The experimental treatments also included the determination of the OM mineralization rate in material from the AE horizon pretreated with a heavy liquid or a heavy liquid and a 0.1 N NaOH solution. The differences between the mineralization rates of the labeled organic matter applied to the soil in the form of glucose, glycine, and uracil under the field conditions after the interaction for 7 and 20 months were revealed. The changes in the mineralization rate after the successive extraction of the labile organic matter with a heavy liquid and a 0.1 N NaOH solution were studied. It was shown that the transformation of the labeled low-molecular-weight organic compounds in the soil over 20 months included their strong inclusion into the humus composition, which was confirmed by the similar values of the mineralization constants of the native and 14C-labeled OM. In addition, the treatments with the

Integrating plant litter quality, soil organic matter stabilization, and the carbon saturation concept

USDA-ARS?s Scientific Manuscript database

Recent research suggests labile plant litters promote the stabilization of soil organic matter (SOM) in physico-chemically protected fractions with relatively slow turnover. However, the effect of litter quality on SOM stabilization is inconsistent. Labile, ‘high quality’ litters characterized by hi...

The Microbial Efficiency-Matrix Stabilization (MEMS) framework integrates plant litter decomposition with soil organic matter stabilization: do labile plant inputs form stable soil organic matter?

PubMed

Cotrufo, M Francesca; Wallenstein, Matthew D; Boot, Claudia M; Denef, Karolien; Paul, Eldor

2013-04-01

The decomposition and transformation of above- and below-ground plant detritus (litter) is the main process by which soil organic matter (SOM) is formed. Yet, research on litter decay and SOM formation has been largely uncoupled, failing to provide an effective nexus between these two fundamental processes for carbon (C) and nitrogen (N) cycling and storage. We present the current understanding of the importance of microbial substrate use efficiency and C and N allocation in controlling the proportion of plant-derived C and N that is incorporated into SOM, and of soil matrix interactions in controlling SOM stabilization. We synthesize this understanding into the Microbial Efficiency-Matrix Stabilization (MEMS) framework. This framework leads to the hypothesis that labile plant constituents are the dominant source of microbial products, relative to input rates, because they are utilized more efficiently by microbes. These microbial products of decomposition would thus become the main precursors of stable SOM by promoting aggregation and through strong chemical bonding to the mineral soil matrix. © 2012 Blackwell Publishing Ltd.

Non-labile Soil Nitrogen Retention beneath Three Tree Species in a Tropical Plantation

Treesearch

Jason P. Kaye; Dan Binkley; Xiaoming Zou

2002-01-01

Soil organic matter is the largest sink for N additions to forests. Species composition may affect soilNretention by altering the amount or proportion of added N stored in non-labile organic pools. We measured 15N tracer retention in labile and non-labile pools of surface (0–20 cm) mineral soils, 7 yr after the tracer was applied to a 9 yr-old Puerto Rican tree...

Effects of composition of labile organic matter on biogenic production of methane in the coastal sediments of the Arabian Sea.

PubMed

Gonsalves, Maria-Judith; Fernandes, Christabelle E G; Fernandes, Sheryl Oliveira; Kirchman, David L; Bharathi, P A Loka

2011-11-01

Coastal regions are potential zones for production of methane which could be governed by ecological/environmental differences or even sediment properties of a niche. In order to test the hypothesis that methanogenesis in most marine sediments could be driven more by proteins than by carbohydrates and lipid content of labile organic matter (LOM), incubation experiments were carried out with sediments from different environmental niches to measure methane production. The methane production rates were examined in relationship to the sediment biochemistry, i.e., carbohydrates, proteins, and lipids. The gas production measured by head space method ranged from 216 ng g( -1) day( -1) in the mangrove sediments to 3.1 μg g( -1) day( -1) in the shallow Arabian Sea. LOM ranged from 1.56 to 2.85 mg g( -1) in the shallow Arabian Sea, from 3.35 to 5.43 mg g( -1) in the mangrove estuary, and from 0.66 to 0.70 mg g( -1) in the sandy sediments with proteins contributing maximum to the LOM pool. Proteins influenced methane production in the clayey sediments of shallow depths of the Arabian Sea (r = 0.933, p < 0.001) and mangrove estuary (r = 0.981, p < 0.001) but in the sandy beach sediments, carbohydrates (r = 0.924, p < 0.001) governed the net methane production. The gas production was more pronounced in shallow and surface sediments and it decreased with depth apparently governed by the decrease in lability index. Thus, the lability index and protein content are important factors that determine methane production rates in these coastal ecosystems.

Rhizosphere Environment and Labile Phosphorus Release from Organic Waste-Amended Soils.

NASA Astrophysics Data System (ADS)

Dao, Thanh H.

2015-04-01

Crop residues and biofertilizers are primary sources of nutrients for organic crop production. However, soils treated with large amounts of nutrient-enriched manure have elevated phosphorus (P) levels in regions of intensive animal agriculture. Surpluses occurred in these amended soils, resulting in large pools of exchangeable inorganic P (Pi) and enzyme-labile organic P (Po) that averaging 30.9 and 68.2 mg kg-1, respectively. Organic acids produced during crop residue decomposition can promote the complexation of counter-ions and decouple and release unbound Pi from metal and alkali metal phosphates. Animal manure and cover crop residues also contain large amounts of soluble organic matter, and likely generate similar ligands. However, a high degree of heterogeneity in P spatial distribution in such amended fields, arising from variances in substrate physical forms ranging from slurries to dried solids, composition, and diverse application methods and equipment. Distinct clusters of Pi and Po were observed, where accumulation of the latter forms was associated with high soil microbial biomass C and reduced phosphomonoesterases' activity. Accurate estimates of plant requirements and lability of soil P pools, and real-time plant and soil P sensing systems are critical considerations to optimally manage manure-derived nutrients in crop production systems. An in situ X-ray fluorescence-based approach to sensing canopy and soil XRFS-P was developed to improve the yield-soil P relationship for optimal nutrient recommendations in addition to allowing in-the-field verification of foliar P status.

Non-labile Soil 15Nitrogen Retention beneath Three Tree Species in a Tropical Plantation

Treesearch

Jason P. Kaye; Dan Binkley; Xiaoming Zou

2002-01-01

Soil organic matter is the largest sink for N additions to forests.Species composition may affect soilNretention by altering the amount or proportion of added N stored in non-labile organic pools. We measured 15N tracer retention in labile and non-labile pools of surface (0–20 cm) mineral soils, 7 yr after the tracer was applied to a 9 yr-old Puerto Rican tree...

Natural organic matter properties in Swedish agricultural streams

NASA Astrophysics Data System (ADS)

Bieroza, Magdalena; Kyllmar, Katarina; Bergström, Lars; Köhler, Stephan

2016-04-01

We have analysed natural organic matter (NOM) properties in 18 agricultural streams in Sweden covering a broad range of environmental (climate, soil type), land use and water quality (nutrient and concentrations, pH, alkalinity) characteristics. Stream water samples collected every two weeks within an ongoing Swedish Monitoring Programme for Agriculture have been analysed for total/dissolved organic carbon, absorbance and fluorescence spectroscopy. A number of quantitative and qualitative spectroscopic parameters was calculated to help to distinguish between terrestrially-derived, refractory organic material and autochthonous, labile material indicative of biogeochemical transformations of terrestrial NOM and recent biological production. The study provides insights into organic matter properties and carbon budgets in agricultural streams and improves understanding of how agricultural catchments transform natural and anthropogenic fluxes of organic matter and nutrients to signals observed in receiving waters.

Interactive priming of biochar and labile organic matter mineralization in a smectite-rich soil.

PubMed

Keith, Alexandra; Singh, Balwant; Singh, Bhupinder Pal

2011-11-15

Biochar is considered as an attractive tool for long-term carbon (C) storage in soil. However, there is limited knowledge about the effect of labile organic matter (LOM) on biochar-C mineralization in soil or the vice versa. An incubation experiment (20 °C) was conducted for 120 days to quantify the interactive priming effects of biochar-C and LOM-C mineralization in a smectitic clayey soil. Sugar cane residue (source of LOM) at a rate of 0, 1, 2, and 4% (w/w) in combination with two wood biochars (450 and 550 °C) at a rate of 2% (w/w) were applied to the soil. The use of biochars (~ -36‰) and LOM (-12.7‰) or soil (-14.3‰) with isotopically distinct δ(13)C values allowed the quantification of C mineralized from biochar and LOM/soil. A small fraction (0.4-1.1%) of the applied biochar-C was mineralized, and the mineralization of biochar-C increased significantly with increasing application rates of LOM, especially during the early stages of incubation. Concurrently, biochar application reduced the mineralization of LOM-C, and the magnitude of this effect increased with increasing rate of LOM addition. Over time, the interactive priming of biochar-C and LOM-C mineralization was stabilized. Biochar application possesses a considerable merit for long-term soil C-sequestration, and it has a stabilizing effect on LOM in soil.

Organic Matter Quality and its Influence on Carbon Turnover and Stabilization in Northern Peatlands

NASA Astrophysics Data System (ADS)

Turetsky, M. R.; Wieder, R. K.

2002-12-01

Peatlands cover 3-5 % of the world's ice-free land area, but store about 33 % of global terrestrial soil carbon. Peat accumulation in northern regions generally is controlled by slow decomposition, which may be limited by cold temperatures and water-logging. Poor organic matter quality also may limit decay, and microbial activity in peatlands likely is regulated by the availability of labile carbon and/or nutrients. Conversely, carbon in recalcitrant soil structures may be chemically protected from microbial decay, particularly in peatlands where carbon can be buried in anaerobic soils. Soil organic matter quality is controlled by plant litter chemical composition and the susceptibility of organic compounds to decomposition through time. There are a number of techniques available for characterizing organic quality, ranging from chemical proximate or elemental analysis to more qualitative methods such as nuclear magenetic resonance, pyrolysis/mass spectroscopy, and Fourier transform infrared spectroscopy. We generally have relied on proximate analysis for quantitative determination of several organic fractions (i.e., water-soluble carbohydrates, soluble nonpolars, water-soluble phenolics, holocellulose, and acid insoluble material). Our approaches to studying organic matter quality in relation to C turnover in peatlands include 1) 14C labelling of peatland vegetation along a latitudinal gradient in North America, allowing us to follow the fate of 14C tracer in belowground organic fractions under varying climates, 2) litter bag studies focusing on the role of individual moss species in litter quality and organic matter decomposition, and 3) laboratory incubations of peat to explore relationships between organic matter quality and decay. These studies suggest that proximate organic fractions vary in lability, but that turnover of organic matter is influenced both by plant species and climate. Across boreal peatlands, measures of soil recalcitrance such as acid

Priming of native soil organic matter by pyrogenic organic matter

NASA Astrophysics Data System (ADS)

DeCiucies, Silene; Dharmakeerthi, Saman; Whitman, Thea; Woolf, Dominic; Lehmann, Johannes

2015-04-01

Priming, in relation to pyrogenic organic matter (PyOM), describes the change in mineralization rate of non-pyrogenic ("native") soil organic matter (nSOM) due to the addition of PyOM. Priming may be 'positive', in that the addition of pyC increases the mineralization rate of native SOM, or 'negative', in that the mineralization rate of nSOM is decreased. Reasons for increased mineralization may include: (i) co-metabolism: microbial decomposition of labile C-additions increases microbial activity, and facilitates additional decomposition of npSOC by active enzymes; (ii) stimulation: substrate additions result in lifted pH, nutrient, oxygen, or water constraints resulting in increased microbial activity. Decreased mineralization may be a result of: (i) inhibition: the opposite of stimulation whereby constraints are aggravated by substrate addition. Substrate addition may also cause inhibition by interfering with enzymes or signaling compounds; (ii) preferential substrate utilization: labile fraction of PyOM additions are preferentially used up by microbes thus causing a decrease in nSOC decomposition; (iii) sorption: organic compounds are adsorbed onto PyOM surfaces, decreasing their rate of mineralization; (iv) stabilization: formation of organo-mineral associations forms stable SOC pools. We have conducted a suite of experiments to investigate these potential interactions. In a seven year long incubation study, PyOM additions increased total OM mineralization for the first 2.5 years, was equal to control after 6.2 years, and was 3% lower after 7.1 years. Cumulative nSOM mineralization was 23% less with the PyOM additions than without, and over 60% of the added PyOM was present in the labile soil fraction after the 7.1 year incubation. Two additional incubation studies, one with and without plants, showed greater nSOM mineralization in the short term and lower nSOM mineralization over the long term. Increased nSOC mineralization due to the presence of plants was

Construction of hierarchically porous metal–organic frameworks through linker labilization

DOE PAGES

Yuan, Shuai; Zou, Lanfang; Qin, Jun-Sheng; ...

2017-05-25

One major goal of metal–organic framework (MOF) research is the expansion of pore size and volume. Although many approaches have been attempted to increase the pore size of MOF materials, it is still a challenge to construct MOFs with precisely customized pore apertures for specific applications. W present a new method, namely linker labilization, to increase the MOF porosity and pore size, giving rise to hierarchical-pore architectures. Microporous MOFs with robust metal nodes and pro-labile linkers were initially synthesized. The mesopores were subsequently created as crystal defects through the splitting of a pro-labile-linker and the removal of the linker fragmentsmore » by acid treatment. We also demonstrate that linker labilization method can create controllable hierarchical porous structures in stable MOFs, which facilitates the diffusion and adsorption process of guest molecules to improve the performances of MOFs in adsorption and catalysis.« less

Construction of hierarchically porous metal-organic frameworks through linker labilization

NASA Astrophysics Data System (ADS)

Yuan, Shuai; Zou, Lanfang; Qin, Jun-Sheng; Li, Jialuo; Huang, Lan; Feng, Liang; Wang, Xuan; Bosch, Mathieu; Alsalme, Ali; Cagin, Tahir; Zhou, Hong-Cai

2017-05-01

A major goal of metal-organic framework (MOF) research is the expansion of pore size and volume. Although many approaches have been attempted to increase the pore size of MOF materials, it is still a challenge to construct MOFs with precisely customized pore apertures for specific applications. Herein, we present a new method, namely linker labilization, to increase the MOF porosity and pore size, giving rise to hierarchical-pore architectures. Microporous MOFs with robust metal nodes and pro-labile linkers were initially synthesized. The mesopores were subsequently created as crystal defects through the splitting of a pro-labile-linker and the removal of the linker fragments by acid treatment. We demonstrate that linker labilization method can create controllable hierarchical porous structures in stable MOFs, which facilitates the diffusion and adsorption process of guest molecules to improve the performances of MOFs in adsorption and catalysis.

Construction of hierarchically porous metal–organic frameworks through linker labilization

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

Yuan, Shuai; Zou, Lanfang; Qin, Jun-Sheng

One major goal of metal–organic framework (MOF) research is the expansion of pore size and volume. Although many approaches have been attempted to increase the pore size of MOF materials, it is still a challenge to construct MOFs with precisely customized pore apertures for specific applications. W present a new method, namely linker labilization, to increase the MOF porosity and pore size, giving rise to hierarchical-pore architectures. Microporous MOFs with robust metal nodes and pro-labile linkers were initially synthesized. The mesopores were subsequently created as crystal defects through the splitting of a pro-labile-linker and the removal of the linker fragmentsmore » by acid treatment. We also demonstrate that linker labilization method can create controllable hierarchical porous structures in stable MOFs, which facilitates the diffusion and adsorption process of guest molecules to improve the performances of MOFs in adsorption and catalysis.« less

Labile dissolved organic carbon supply limits hyporheic denitrification

Treesearch

Jay P. Zarnetske; Roy Haggerty; Steven M. Wondzell; Michelle A. Baker

2012-01-01

We used an in situ steady state 15N-labeled nitrate and acetate well-to-wells injection experiment to determine how the availability of labile dissolved organic carbon as acetate influences microbial denitrification in the hyporheic zone of an upland (third-order) agricultural stream.

Energy Transformations of Soil Organic Matter in a Changing World

NASA Astrophysics Data System (ADS)

Herrmann, A. M.; Coucheney, E.; Grice, S. M.; Ritz, K.; Harris, J.

2011-12-01

The role of soils in governing the terrestrial carbon balance is acknowledged as being important but remains poorly understood within the context of climate change. Soils exchange energy with their surroundings and are therefore open systems thermodynamically, but little is known how energy transformations of decomposition processes are affected by temperature. Soil organic matter and the soil biomass can be conceptualised as analogous to the 'fuel' and 'biological engine' of the earth, respectively, and are pivotal in driving the belowground carbon cycle. Thermodynamic principles of soil organic matter decomposition were evaluated by means of isothermal microcalorimetry (TAM Air, TA Instruments, Sollentuna Sweden: (i) Mineral forest soils from the Flakaliden long-term nitrogen fertilisation experiment (Sweden) were amended with a range of different substrates representing structurally simple to complex, ecologically pertinent organic matter and heat signatures were determined at temperatures between 5 and 25°C. (ii) Thermodynamic and resource-use efficiencies of the biomass were determined in arable soils which received contrasting long-term management regimes with respect to organic matter and nitrogen since 1956. The work showed that (i) structurally labile components have higher activation energy and temperature dependence than structurally more complex organic components. This is, however, in contrast to the thermodynamic argument which suggests the opposite that reactions metabolising structurally complex, aromatic components have higher temperature dependence than reactions metabolising structurally more labile components. (ii) Microbial communities exposed to long-term stress by heavy metal and low pH were less thermodynamic efficient and showed a decrease in resource-use efficiency in comparison with conventional input regimes. Differences in efficiencies were mirrored in both the phenotypic and functional profiles of the communities. We will present our

Temperature-driven decoupling of key phases of organic matter degradation in marine sediments.

PubMed

Weston, Nathaniel B; Joye, Samantha B

2005-11-22

The long-term burial of organic carbon in sediments results in the net accumulation of oxygen in the atmosphere, thereby mediating the redox state of the Earth's biosphere and atmosphere. Sediment microbial activity plays a major role in determining whether particulate organic carbon is recycled or buried. A diverse consortium of microorganisms that hydrolyze, ferment, and terminally oxidize organic compounds mediates anaerobic organic matter mineralization in anoxic sediments. Variable temperature regulation of the sequential processes, leading from the breakdown of complex particulate organic carbon to the production and subsequent consumption of labile, low-molecular weight, dissolved intermediates, could play a key role in controlling rates of overall organic carbon mineralization. We examined sediment organic carbon cycling in a sediment slurry and in flow through bioreactor experiments. The data show a variable temperature response of the microbial functional groups mediating organic matter mineralization in anoxic marine sediments, resulting in the temperature-driven decoupling of the production and consumption of organic intermediates. This temperature-driven decoupling leads to the accumulation of labile, low-molecular weight, dissolved organic carbon at low temperatures and low-molecular weight dissolved organic carbon limitation of terminal metabolism at higher temperatures.

Effects of exotic plantation forests on soil edaphon and organic matter fractions.

PubMed

Xu, Gang; Liu, Yao; Long, Zhijian; Hu, Shanglian; Zhang, Yuanbin; Jiang, Hao

2018-06-01

There is uncertainty and limited knowledge regarding soil microbial properties and organic matter fractions of natural secondary forest accompanying chemical environmental changes of replacement by pure alien plantation forests in a hilly area of southwest of Sichuan province China. The aim of this study was to evaluate the impact of natural secondary forest (NSF) to pure Cryptomeria fortunei forest (CFF) and Cunninghamia lanceolata forest (CLF) on soil organic fractions and microbial communities. The results showed that the soil total phospholipid fatty acids (PLFAs), total bacteria and fungi, microbial carbon pool, organic recalcitrant carbon (C) and (N) fractions, soil microbial quotient and labile and recalcitrant C use efficiencies in each pure plantation were significantly decreased, but their microbial N pool, labile C and N pools, soil carbon dioxide efflux, soil respiratory quotient and recalcitrant N use efficiency were increased. An RDA analysis revealed that soil total PLFAs, total bacteria and fungi and total Gram-positive and Gram-negative bacteria were significantly associated with exchangeable Al 3+ , exchangeable acid, Al 3+ , available P and Mg 2+ and pH, which resulted into microbial functional changes of soil labile and recalcitrant substrate use efficiencies. Modified microbial C- and N-use efficiency due to forest conversion ultimately meets those of rapidly growing trees in plantation forests. Enlarged soil labile fractions and soil respiratory quotients in plantation forests would be a potential positive effect for C source in the future forest management. Altogether, pure plantation practices could provoke regulatory networks and functions of soil microbes and enzyme activities, consequently leading to differentiated utilization of soil organic matter fractions accompanying the change in environmental factors. Copyright © 2018 Elsevier B.V. All rights reserved.

Natural organic matter properties in Swedish agricultural streams

NASA Astrophysics Data System (ADS)

Bieroza, Magdalena; Kyllmar, Katarina; Bergström, Lars; Köhler, Stephan

2017-04-01

The following paper shows natural organic matter (NOM) properties of stream water samples collected from 8 agricultural streams and 12 agricultural observational fields in Sweden. The catchments and observational fields cover a broad range of environmental (climate, soil type), land use and water quality (nutrient and concentrations, pH, alkalinity) characteristics. Stream water samples collected every two weeks within an ongoing Swedish Monitoring Programme for Agriculture have been analysed for total/dissolved organic carbon, absorbance and fluorescence spectroscopy. A number of quantitative and qualitative spectroscopic parameters was calculated to help to distinguish between terrestrially-derived, refractory organic material and autochthonous, labile material indicative of biogeochemical transformations of terrestrial NOM and recent biological production. The study provides insights into organic matter properties and carbon budgets in agricultural streams and improves understanding of how agricultural catchments transform natural and anthropogenic fluxes of organic matter and nutrients. The insights from the grab sampling are supported by high-frequency turbidity, fulvic-like and tryptophan-like fluorescence measurements with in situ optical sensor.

Hypoxia causes preservation of labile organic matter and changes seafloor microbial community composition (Black Sea).

PubMed

Jessen, Gerdhard L; Lichtschlag, Anna; Ramette, Alban; Pantoja, Silvio; Rossel, Pamela E; Schubert, Carsten J; Struck, Ulrich; Boetius, Antje

2017-02-01

Bottom-water oxygen supply is a key factor governing the biogeochemistry and community composition of marine sediments. Whether it also determines carbon burial rates remains controversial. We investigated the effect of varying oxygen concentrations (170 to 0 μM O 2 ) on microbial remineralization of organic matter in seafloor sediments and on community diversity of the northwestern Crimean shelf break. This study shows that 50% more organic matter is preserved in surface sediments exposed to hypoxia compared to oxic bottom waters. Hypoxic conditions inhibit bioturbation and decreased remineralization rates even within short periods of a few days. These conditions led to the accumulation of threefold more phytodetritus pigments within 40 years compared to the oxic zone. Bacterial community structure also differed between oxic, hypoxic, and anoxic zones. Functional groups relevant in the degradation of particulate organic matter, such as Flavobacteriia , Gammaproteobacteria , and Deltaproteobacteria , changed with decreasing oxygenation, and the microbial community of the hypoxic zone took longer to degrade similar amounts of deposited reactive matter. We conclude that hypoxic bottom-water conditions-even on short time scales-substantially increase the preservation potential of organic matter because of the negative effects on benthic fauna and particle mixing and by favoring anaerobic processes, including sulfurization of matter.

Hypoxia causes preservation of labile organic matter and changes seafloor microbial community composition (Black Sea)

PubMed Central

Jessen, Gerdhard L.; Lichtschlag, Anna; Ramette, Alban; Pantoja, Silvio; Rossel, Pamela E.; Schubert, Carsten J.; Struck, Ulrich; Boetius, Antje

2017-01-01

Bottom-water oxygen supply is a key factor governing the biogeochemistry and community composition of marine sediments. Whether it also determines carbon burial rates remains controversial. We investigated the effect of varying oxygen concentrations (170 to 0 μM O2) on microbial remineralization of organic matter in seafloor sediments and on community diversity of the northwestern Crimean shelf break. This study shows that 50% more organic matter is preserved in surface sediments exposed to hypoxia compared to oxic bottom waters. Hypoxic conditions inhibit bioturbation and decreased remineralization rates even within short periods of a few days. These conditions led to the accumulation of threefold more phytodetritus pigments within 40 years compared to the oxic zone. Bacterial community structure also differed between oxic, hypoxic, and anoxic zones. Functional groups relevant in the degradation of particulate organic matter, such as Flavobacteriia, Gammaproteobacteria, and Deltaproteobacteria, changed with decreasing oxygenation, and the microbial community of the hypoxic zone took longer to degrade similar amounts of deposited reactive matter. We conclude that hypoxic bottom-water conditions—even on short time scales—substantially increase the preservation potential of organic matter because of the negative effects on benthic fauna and particle mixing and by favoring anaerobic processes, including sulfurization of matter. PMID:28246637

The temperature sensitivity of soil organic carbon decomposition is not related to labile and recalcitrant carbon.

PubMed

Tang, Jie; Cheng, Hao; Fang, Changming

2017-01-01

The response of resistant soil organic matter to temperature change is crucial for predicting climate change impacts on C cycling in terrestrial ecosystems. However, the response of the decomposition of different soil organic carbon (SOC) fractions to temperature is still under debate. To investigate whether the labile and resistant SOC components have different temperature sensitivities, soil samples were collected from three forest and two grass land sites, along with a gradient of latitude from 18°40'to 43°17'N and elevation from 600 to 3510 m across China, and were incubated under changing temperature (from 12 to 32 oC) for at least 260 days. Soil respiration rates were positively related to the content of soil organic carbon and soil microbial carbon. The temperature sensitivity of soil respiration, presented as Q10 value, varies from 1.93 ± 0.15 to 2.60 ± 0.21. During the incubation, there were no significant differences between the Q10 values of soil samples from different layers of the same site, nor a clear pattern of Q10 values along with the gradient of latitude. The result of this study does not support current opinion that resistant soil carbon decomposition is more sensitive to temperature change than labile soil carbon.

Experimental evidence for an effect of early-diagenetic interaction between labile and refractory marine sedimentary organic matter on nitrogen dynamics

NASA Astrophysics Data System (ADS)

Turnewitsch, Robert; Domeyer, Bettina; Graf, Gerhard

2007-05-01

In most natural sedimentary systems labile and refractory organic material (OM) occur concomitantly. Little, however, is known on how different kinds of OM interact and how such interactions affect early diagenesis in sediments. In a simple sediment experiment, we investigated how interactions of OM substrates of different degradability affect benthic nitrogen (N) dynamics. Temporal evolution of a set of selected biogeochemical parameters was monitored in sandy sediment over 116 days in three experimental set-ups spiked with labile OM (tissue of Mytilus edulis), refractory OM (mostly aged Zostera marina and macroalgae), and a 1:1 mixture of labile and refractory OM. The initial amounts of particulate organic carbon (POC) were identical in the three set-ups. To check for non-linear interactions between labile and refractory OM, the evolution of the mixture system was compared with the evolution of the simple sum of the labile and refractory systems, divided by two. The sum system is the experimental control where labile and refractory OM are virtually combined but not allowed to interact. During the first 30 days there was evidence for net dissolved-inorganic-nitrogen (DIN) production followed by net DIN consumption. (Here 'DIN' is the sum of ammonium, nitrite and nitrate.) After ˜ 30 days a quasi steady state was reached. Non-linear interactions between the two types of OM were reflected by three main differences between the early-diagenetic evolutions of nitrogen dynamics of the mixture and sum (control) systems: (1) In the mixture system the phases of net DIN production and consumption commenced more rapidly and were more intense. (2) The mixture system was shifted towards a more oxidised state of DIN products [as indicated by increased (nitrite + nitrate)/(ammonium) ratios]. (3) There was some evidence that more OM, POC and particulate nitrogen were preserved in the mixture system. That is, in the mixture system more particulate OM was preserved while a higher

Temperature sensitivity of organic-matter decay in tidal marshes

USGS Publications Warehouse

Kirwan, Matthew L.; Guntenspergen, Glenn R.; Langley, J.A.

2014-01-01

Approximately half of marine carbon sequestration takes place in coastal wetlands, including tidal marshes, where organic matter contributes to soil elevation and ecosystem persistence in the face of sea-level rise. The long-term viability of marshes and their carbon pools depends, in part, on how the balance between productivity and decay responds to climate change. Here, we report the sensitivity of labile soil organic-matter decay in tidal marshes to seasonal and latitudinal variations in temperature measured over a 3-year period. We find a moderate increase in decay rate at warmer temperatures (3-6% per °C, Q10 = 1.3-1.5). Despite the profound differences between microbial metabolism in wetlands and uplands, our results indicate a strong conservation of temperature sensitivity. Moreover, simple comparisons with organic-matter production suggest that elevated atmospheric CO2 and warmer temperatures will accelerate carbon accumulation in marsh soils, and potentially enhance their ability to survive sea-level rise.

Microbially driven export of labile organic carbon from the Greenland ice sheet

NASA Astrophysics Data System (ADS)

Musilova, Michaela; Tranter, Martyn; Wadham, Jemma; Telling, Jon; Tedstone, Andrew; Anesio, Alexandre M.

2017-04-01

Glaciers and ice sheets are significant sources of dissolved organic carbon and nutrients to downstream subglacial and marine ecosystems. Climatically driven increases in glacial runoff are expected to intensify the impact of exported nutrients on local and regional downstream environments. However, the origin and bioreactivity of dissolved organic carbon from glacier surfaces are not fully understood. Here, we present simultaneous measurements of gross primary production, community respiration, dissolved organic carbon composition and export from different surface habitats of the Greenland ice sheet, throughout the ablation season. We found that microbial production was significantly correlated with the concentration of labile dissolved organic species in glacier surface meltwater. Further, we determined that freely available organic compounds made up 62% of the dissolved organic carbon exported from the glacier surface through streams. We therefore conclude that microbial communities are the primary driver for labile dissolved organic carbon production and recycling on glacier surfaces, and that glacier dissolved organic carbon export is dependent on active microbial processes during the melt season.

DETERMINATION OF APPARENT QUANTUM YIELD SPECTRA FOR THE FORMATION OF BIOLOGICALLY LABILE PHOTOPRODUCTS

EPA Science Inventory

Quantum yield spectra for the photochemical formation of biologically labile photoproducts from dissolved organic matter (DOM) have not been available previously, although they would greatly facilitate attempts to model photoproduct formation rates across latitudinal, seasonal, a...

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.

Estimating soil labile organic carbon and potential turnover rates using a sequential fumigation–incubation procedure.

Treesearch

X.M. Zoua; H.H. Ruanc; Y. Fua; X.D. Yanga; L.Q. Sha

2005-01-01

Labile carbon is the fraction of soil organic carbon with most rapid turnover times and its oxidation drives the flux of CO2 between soils and atmosphere. Available chemical and physical fractionation methods for estimating soil labile organic carbon are indirect and lack a clear biological definition. We have modified the well-established Jenkinson and Powlson’s...

The role of clay minerals in the preservation of organic matter in sediments of Qinghai Lake, NW China

USGS Publications Warehouse

Yu, Bingsong; Dong, Hailiang; Jiang, Hongchen; Lv, Guo; Eberl, Dennis D.; Li, Shanying; Kim, Jinwook

2009-01-01

The role of saline lake sediments in preserving organic matter has long been recognized. In order to further understand the preservation mechanisms, the role of clay minerals was studied. Three sediment cores, 25, 57, and 500 cm long, were collected from Qinghai Lake, NW China, and dissected into multiple subsamples. Multiple techniques were employed, including density fractionation, X-ray diffraction, scanning and transmission electron microscopy (SEM and TEM), total organic carbon (TOC) and carbon compound analyses, and surface area determination. The sediments were oxic near the water-sediment interface, but became anoxic at depth. The clay mineral content was as much as 36.8%, consisting mostly of illite, chlorite, and halloysite. The TEM observations revealed that organic matter occurred primarily as organic matter-clay mineral aggregates. The TOC and clay mineral abundances are greatest in the mid-density fraction, with a positive correlation between the TOC and mineral surface area. The TOC of the bulk sediments ranges from 1 to 3% with the non-hydrocarbon fraction being predominant, followed by bitumen, saturated hydrocarbon, aromatic hydrocarbons, and chloroform-soluble bitumen. The bimodal distribution of carbon compounds of the saturated hydrocarbon fraction suggests that organic matter in the sediments was derived from two sources: terrestrial plants and microorganisms/algae. Depthrelated systematic changes in the distribution patterns of the carbon compounds suggest that the oxidizing conditions and microbial abundance near the water-sediment interface promote degradation of labile organic matter, probably in adsorbed form. The reducing conditions and small microbial biomass deeper in the sediments favor preservation of organic matter, because of the less labile nature of organic matter, probably occurring within clay mineral-organic matter aggregates that are inaccessible to microorganisms. These results have important implications for our

Enzymatic Regulation of Organic Matter Metabolism in Siberia's Kolyma River Watershed

NASA Astrophysics Data System (ADS)

Mann, P. J.; Sobczak, W. V.; Vonk, J. E.; Davydova, A.; Schade, J. D.; Bulygina, E. B.; Davydov, S.; Zimov, N.; Holmes, R. M.

2011-12-01

Arctic soils contain vast amounts of ancient organic carbon locked up in permafrost. This organic matter can be unlocked via permafrost thaw and bacterial processing. Microbial communities release enzymes into the environment (ectoenzymes) as a means of degrading organic matter and to acquire carbon, nitrogen and phosphorus for assimilation. Limited ectoenzyme production, or unfavourable in-situ conditions (e.g. temperature, oxygen) can limit degradation of permafrost on land. Environmental conditions may become more favourable for bacterial degradation as carbon compounds are released from permafrost into Arctic streams and rivers. We measured the potential activities of a suite of ectoenzymes within surface waters collected from a range of streams and rivers throughout the Kolyma River basin, Siberia. Ectoenzyme activities were additionally measured in Kolyma river waters collected at three distinct periods of the hydrograph (under-ice, freshet and summer conditions). In total, seven enzymes were studied allowing bacterial requirements for a wide range of compounds including lignin, carbohydrates, proteins and cellulose to be assessed. To investigate the lability of the carbon pool within these waters, we measured the biological oxygen demand over 5 days (BOD). Significant correlations were observed between phenol oxidase activity and BOD across all of the study sites, suggesting the rate of phenolic degradation may be a controlling factor in organic carbon metabolism. The activity rate in ectoenzymes that catalyze phosphate, lignin and carbon substrates varied significantly within the Kolyma river over the hydrograph, indicating that seasonal changes in organic matter composition may also shift the limiting resource for bacterial degradation. High activity rates in ectoenzymes that catalyze lignin, chitin, cellulose and proteins were measured in waters draining permafrost ice complexes. These results suggest that organic carbon is continually processed

Evidence for the enhanced lability of dissolved organic matter following permafrost slope disturbance in the Canadian High Arctic

NASA Astrophysics Data System (ADS)

Woods, Gwen C.; Simpson, Myrna J.; Pautler, Brent G.; Lamoureux, Scott F.; Lafrenière, Melissa J.; Simpson, André J.

2011-11-01

Arctic landscapes are believed to be highly sensitive to climate change and accelerated disturbance of permafrost is expected to significantly impact the rate of carbon cycling. While half the global soil organic matter (SOM) is estimated to reside in Arctic soils, projected warmer temperatures and permafrost disturbance will release much of this SOM into waterways in the form of dissolved organic matter (DOM). The spring thaw and subsequent flushing of soils releases the highest contributions of DOM annually but has historically been undersampled due to the difficulties of sampling during this period. In this study, passive samplers were placed throughout paired High Arctic watersheds during the duration of the 2008 spring flush in Nunavut, Canada. The watersheds are very similar with the exception of widespread active layer detachments (ALDs) that occurred within one of the catchments during a period of elevated temperatures in the summer of 2007. DOM samples were analyzed for structural and spectral characteristics via nuclear magnetic resonance (NMR) and fluorescence spectroscopy as well as vulnerability to degradation with simulated solar exposure. Lignin-derived phenols were further assessed utilizing copper(II) oxide (CuO) oxidation and gas chromatography/mass spectrometry (GC/MS). The samples were found to have very low dissolved lignin phenol content (˜0.07% of DOC) and appear to originate from primarily non-woody angiosperm vegetation. The acid/aldehyde ratios for dissolved vanillyl phenols were found to be high (up to 3.6), indicating the presence of highly oxidized lignin. Differences between DOM released from the ALD vs. the undisturbed watershed suggest that these shallow detachment slides have significantly impacted the quality of Arctic DOM. Although material released from the disturbed catchment was found to be highly oxidized, DOM in the lake into which this catchment drained had chemical characteristics indicating high contributions from

Soil organic matter in podzol horizons of the Amazon region: Humification, recalcitrance, and dating.

PubMed

Tadini, Amanda M; Nicolodelli, Gustavo; Senesi, Giorgio S; Ishida, Débora A; Montes, Célia R; Lucas, Yves; Mounier, Stéphane; Guimarães, Francisco E G; Milori, Débora M B P

2018-02-01

Characteristics of soil organic matter (SOM) are important, especially in the Amazon region, which represents one of the world's most relevant carbon reservoirs. In this work, the concentrations of carbon and differences in its composition (humification indexes) were evaluated and compared for several horizons (0 to 390cm) of three typical Amazonian podzol profiles. Fluorescence spectroscopy was used to investigate the humic acid (HA) fractions of SOM isolated from the different samples. Simple and labile carbon structures appeared to be accumulated in surface horizons, while more complex humified compounds were leached and accumulated in intermediate and deeper Bh horizons. The results suggested that the humic acids originated from lignin and its derivatives, and that lignin could accumulate in some Bh horizons. The HA present in deeper Bh horizons appeared to originate from different formation pathways, since these horizons showed different compositions. There were significant compositional changes of HA with depth, with four types of organic matter: recalcitrant, humified, and old dating; labile and young dating; humified and young dating; and little humified and old dating. Therefore, the humification process had no direct relation with the age of the organic matter in the Amazonian podzols. Copyright © 2017 Elsevier B.V. All rights reserved.

Soil organic matter stabilization in grazing highland soils from the Andean Plateau

NASA Astrophysics Data System (ADS)

Muñoz, M. A.; Faz, A.; Zornoza, R.

2012-04-01

Grasslands comprise approximately 40% of the earth's land area and play a critical role in the global carbon cycle. Apolobamba is a grazing highland located in the Andean Plateau where sustainable vicuna (Vicugna vicugna) management programme is carried out. Understanding the soil properties and the organic matter dynamics is fundamental to determine the grazing impacts in the carbon reservoirs. However, the labile and recalcitrant fractions of C have not been widely studied under field conditions, especially in high grasslands. The objectives of this survey were to: (i) achieve a soil characterization through general physico-chemical properties and (ii) study soil organic matter stabilization through recalcitrant and labile carbon budgets in Apolobamba. Regarding the lastly vicuna censuses carried out in the studied area, eight representative zones with different vicuna densities were selected and soil samples were collected. Other characteristics were also considered to select the study zones: (1) alpaca densities, (2) vegetation communities (3) plant cover and (4) landscape and geo-morphological description. Recalcitrant and water soluble organic carbon were determined as well as recalcitrant index. General soil characterization showed strongly acid and no saline soils with high cation exchange capacity and sandy-loam and loam textures. Total nitrogen contents indicated no limitation for the native vegetation growth. In general, no relationships were found among general soil properties, vicuna and alpaca densities; however, zones with highest alpaca density could be prone to soil erosion based on the available P distribution and the texture results. Additionally, a negative alpaca grazing influence in the soil organic carbon stocks was observed. On the other hand, high soil recalcitrant carbon contents (3.7 ± 0.3 kg m-2) and recalcitrance index (0.8 ± 0.1) were found. Likewise, labile C exhibited similar values to those obtained from researchers conducted in

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.

Abiotic Bromination of Soil Organic Matter

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

Leri, Alessandra C.; Ravel, Bruce

Biogeochemical transformations of plant-derived soil organic matter (SOM) involve complex abiotic and microbially mediated reactions. One such reaction is halogenation, which occurs naturally in the soil environment and has been associated with enzymatic activity of decomposer organisms. Building on a recent finding that naturally produced organobromine is ubiquitous in SOM, we hypothesized that inorganic bromide could be subject to abiotic oxidations resulting in bromination of SOM. Through lab-based degradation treatments of plant material and soil humus, we have shown that abiotic bromination of particulate organic matter occurs in the presence of a range of inorganic oxidants, including hydrogen peroxide andmore » assorted forms of ferric iron, producing both aliphatic and aromatic forms of organobromine. Bromination of oak and pine litter is limited primarily by bromide concentration. Fresh plant material is more susceptible to bromination than decayed litter and soil humus, due to a labile pool of mainly aliphatic compounds that break down during early stages of SOM formation. As the first evidence of abiotic bromination of particulate SOM, this study identifies a mechanistic source of the natural organobromine in humic substances and the soil organic horizon. Formation of organobromine through oxidative treatments of plant material also provides insights into the relative stability of aromatic and aliphatic components of SOM.« less

Abiotic Bromination of Soil Organic Matter.

PubMed

Leri, Alessandra C; Ravel, Bruce

2015-11-17

Biogeochemical transformations of plant-derived soil organic matter (SOM) involve complex abiotic and microbially mediated reactions. One such reaction is halogenation, which occurs naturally in the soil environment and has been associated with enzymatic activity of decomposer organisms. Building on a recent finding that naturally produced organobromine is ubiquitous in SOM, we hypothesized that inorganic bromide could be subject to abiotic oxidations resulting in bromination of SOM. Through lab-based degradation treatments of plant material and soil humus, we have shown that abiotic bromination of particulate organic matter occurs in the presence of a range of inorganic oxidants, including hydrogen peroxide and assorted forms of ferric iron, producing both aliphatic and aromatic forms of organobromine. Bromination of oak and pine litter is limited primarily by bromide concentration. Fresh plant material is more susceptible to bromination than decayed litter and soil humus, due to a labile pool of mainly aliphatic compounds that break down during early stages of SOM formation. As the first evidence of abiotic bromination of particulate SOM, this study identifies a mechanistic source of the natural organobromine in humic substances and the soil organic horizon. Formation of organobromine through oxidative treatments of plant material also provides insights into the relative stability of aromatic and aliphatic components of SOM.

Particulate organic matter predicts bacterial productivity in a river dominated estuary

NASA Astrophysics Data System (ADS)

Crump, B. C.

2015-12-01

Estuaries act as coastal filters for organic and inorganic fluvial materials in which microbial, biogeochemical, and ecological processes combine to transform organic matter and nutrients prior to export to the coastal ocean. The function of this estuarine 'bioreactor' is linked to the residence times of those materials and to rates of microbial heterotrophic activity. Our ability to forecast the impact of global change on estuarine bioreactor function requires an understanding of the basic controls on microbial community activity and diversity. In the Columbia River estuary, the microbial community undergoes a dramatic seasonal shift in species composition during which a spring bacterioplankton community, dominated by Flavobacteriaceae and Oceanospirillales, is replaced by a summer community, dominated by Rhodobacteraceae and several common marine taxa. This annual shift occurs in July, following the spring freshet, when river flow and river chlorophyll concentration decrease and when estuarine water residence time increases. Analysis of a large dataset from 17 research cruises (1990-2014) showed that the composition of particulate organic matter in the estuary changes after the freshet with decreasing organic carbon and nitrogen content, and increasing contribution of marine and autochthonous estuarine organic matter (based on PO13C and pigment ratios). Bacterial production rates (measured as leucine or thymidine incorporation rates) in the estuary respond to this change, and correlate strongly with labile particulate nitrogen concentration and temperature during individual sampling campaigns, and with the concentration of chlorophyll in the Columbia River across all seasons. Regression models suggest that the concentration of labile particulate nitrogen and the rate of bacterial production can be predicted from sensor measurements of turbidity, salinity, and temperature in the estuary and chlorophyll in the river. These results suggest that the quality of

Using solid 13C NMR coupled with solution 31P NMR spectroscopy to investigate molecular species and lability of organic carbon and phosphorus from aquatic plants in Tai Lake, China.

PubMed

Liu, Shasha; Zhu, Yuanrong; Wu, Fengchang; Meng, Wei; Wang, Hao; He, Zhongqi; Guo, Wenjing; Song, Fanhao; Giesy, John P

2017-01-01

Forms and labilities of plant-derived organic matters (OMs) including carbon (C) and phosphorus (P) were fundamental for understanding their release, degradation and environmental behaviour in lake ecosystems. Thus, solid 13 C and solution 31 P nuclear magnetic resonance (NMR) spectroscopy were used to characterize biomass of six aquatic plants in Tai Lake, China. The results showed that carbohydrates (61.2% of the total C) were predominant C functional group in the solid 13 C NMR spectra of plant biomass, which may indicate high lability and bioavailability of aquatic plants-derived organic matter in lakes. There was 72.6-103.7% of the total P in aquatic plant biomass extracted by NaOH-EDTA extracts. Solution 31 P NMR analysis of these NaOH-EDTA extracts further identified several molecular species of P including orthophosphate (50.1%), orthophosphate monoesters (46.8%), DNA (1.6%) and pyrophosphate (1.4%). Orthophosphate monoesters included β-glycerophosphate (17.7%), hydrolysis products of RNA (11.7%), α-glycerophosphate (9.2%) and other unknown monoesters (2.1%). Additionally, phytate, the major form of organic P in many lake sediments, was detected in floating plant water poppy. These inorganic P (e.g. orthophosphate and pyrophosphate) and organic P (e.g. diester and its degradation products) identified in plant biomass were all labile and bioavailable P, which would play an important role in recycling of P in lakes. These results increased knowledge of chemical composition and bioavailability of OMs derived from aquatic plants in lakes.

Water repellency and organic matter composition after a wildfire: new insights using thermal analysis

NASA Astrophysics Data System (ADS)

Neris, Jonay; Doerr, Stefan

2014-05-01

Water repellency, a key parameter in the hydrological and ecological behaviour of ecosystems, is one of the main soil properties affected by wildfire through its impact on organic matter (Shakesby and Doerr, 2006). This study examines the link between post-fire organic matter quantity and composition, soil water repellency and related hydrological properties in order to (i) examine the influence of different organic matter pools on soil hydrological properties and (ii) to explore the use of these links as a proxy for soil hydrological impacts of fire. Soil samples from five fire-affected burned and unburned control sites in Andisols terrain in Tenerife, previously studied for water repellency and hydrology-related properties (Neris et al., 2013), were selected and thermogravimetric analysis (TG) carried out to evaluate fire impacts on their organic matter composition. A decrease in the organic matter quantity as well as in the relative amount of the labile organic matter pool and an increase in the recalcitrant and/or refractory pool depending was observed in the burned soils. TG data, using 10 ºC temperature range steps, allowed reasonable prediction of soil properties evaluated, with R2 ranging from 0.4 to 0.8. The labile pool showed a broad and positive influence on most soil properties evaluated, whereas the refractory pool and the dehydration range affected the surface water holding capacity and water repellency. These results, in conjunction with the simplicity of the TG analysis suggest that, following a calibration step to link TG data to the site-specific post-fire soil properties, this method may be a useful tool for rapid and cost-effective soil hydrological response evaluation after the fire. References Neris, J., Tejedor, M., Fuentes, J., Jiménez, C., 2013. Infiltration, runoff and soil loss in Andisols affected by forest fire (Canary Islands, Spain). Hydrological Processes 27(19), 2814-2824. Shakesby, R.A., Doerr, S.H., 2006. Wildfire as a

Oxygen consumption and labile dissolved organic carbon uptake by benthic biofilms

NASA Astrophysics Data System (ADS)

de Falco, Natalie; Boano, Fulvio; Arnon, Shai

2015-04-01

Biogeochemical activity in streams is often magnified at interfaces, such as in the case of biofilm growth near the surface of the stream sediments. The objective of this study was to evaluate the relative importance of surficial biofilms versus the biofilm in the hyporheic zone to the processes of biodegradation of a labile dissolved organic carbon (DOC) and to oxygen consumption. Experiments were conducted in a recirculating flume, equipped with a drainage system that enables the control on losing and gaining fluxes. A surficial biofilm was developed over a sandy streambed with dune-shaped bed forms, by providing labile DOC (sodium benzoate) and nitrate. Homogeneously distributed biofilm was obtained by the same feeding strategy but with mixing the sediments manually on a daily basis. After the biofilm growth period, transformation of the labile DOC under different overlying velocities and losing or gaining fluxes was studied after spiking with sodium benzoate and by monitoring the decrease in DOC concentration in the bulk water over time using an online UV/Vis spectrophotometer. In addition, oxygen profiles across the water-streambed interface were measured at different locations along the bed form using oxygen microelectrodes. Preliminary results showed that the rate of labile DOC degradation increased exponentially with increasing overlying water velocity, regardless of the type of biofilm. Gaining and losing conditions did not play a critical role in the DOC degradation regardless of the type of biofilm, because the labile DOC was quickly utilized close to the surface. Under losing conditions, complete depletion of oxygen was observed within the top 5 millimeters, regardless of the biofilm type. In contrast, oxygen profiles under gaining condition showed an incomplete consumption of oxygen followed by an increase in the concentration of oxygen deeper in the sediments due to the upward flow of oxygenated groundwater. The results suggest that the transformation

Biogeochemical implications of labile phosphorus in forest soils determined by the Hedley fractionation procedure.

PubMed

Johnson, Arthur H; Frizano, Jaqueline; Vann, David R

2003-05-01

Forest ecologists and biogeochemists have used a variety of extraction techniques to assess labile vs. non-labile soil P pools in chronosequences, the balance between biological vs. geochemical control of P transformations across a wide range of soil orders, the role of plants with either N-fixing or mycorrhizal symbionts in controlling soil P fractions, and to make inferences about plant-available P. Currently, variants of the sequential extraction procedure developed by M. J. Hedley and co-workers afford the greatest discrimination among labile and non-labile organic and inorganic P pools. Results of recent studies that used this technique to evaluate P fractions in forest soils indicate the following: (1) in intact, highly weathered forest soils of the humid tropics, Hedley-labile P values are several times larger than extractable P values resulting from mildly acidic extracting solutions which were commonly used in the past 2 decades; (2) pools of Hedley-labile P are several times larger than the annual forest P requirement and P required from the soil annually in both temperate and tropical forests; (3) long-term trends in non-labile P pools during pedogenesis are adequately represented by the Walker and Syers' model of changes in P fractionation during soil development. However, to better represent trends in pools that can supply plant-available P across forest soils of different age and weathering status, the paradigm should be modified; and (4) across a wide range of tropical and temperate forest soils, organic matter content is an important determinant of Hedley-labile P.

INTERACTIONS BETWEEN PHOTOCHEMICAL AND MICROBIAL DECOMPOSITION IN MODIFYING THE BIOLOGICAL AVAILABILITY AND OPTICAL PROPERTIES OF ESTUARINE DISSOLVED ORGANIC MATTER

EPA Science Inventory

Direct photodecomposition and photochemically-mediated bacterial degradation (via photochemical modification of otherwise refractory DOM into biologically labile forms) provide
important pathways for the loss of dissolved organic matter in coastal waters. Here we report
lab...

[Impact of Land Utilization Pattern on Distributing Characters of Labile Organic Carbon in Soil Aggregates in Jinyun Mountain].

PubMed

Li, Rui; Jiang, Chang-sheng; Hao, Qing-ju

2015-09-01

Four land utilization patterns were selected for this study in Jinyun mountain, including subtropical evergreen broad-leaved forest (abbreviation: forest), sloping farmland, orchard and abandoned land. Soil samples were taken every 10 cm in the depth of 60 cm soil and proportions of large macroaggregates (> 2 mm), small macroaggregates (0. 25-2 mm), microaggregates (0. 053 - 0. 25 mm) and silt + clay (<0. 053 mm) were obtained by wet sieving method to measure the content of organic carbon and labile organic carbon in each aggregate fraction and analyze impacts of land uses on organic carbon and labile organic carbon of soil aggregates. LOC content of four soil aggregates were significantly reduced with the increase of soil depth; in layers of 0-60 cm soil depth, our results showed that LOC contents of forest and abandoned land were higher than orchard and sloping farmland. Reserves of labile organic carbon were estimated by the same soil quality, it revealed that forest (3. 68 Mg.hm-2) > abandoned land (1. 73 Mg.hm-2) > orchard (1. 43 Mg.hm-2) >sloping farmland (0.54 Mg.hm-2) in large macroaggregates, abandoned land (7.77, 5. 01 Mg.hm-2) > forest (4. 96, 2.71 Mg.hm-2) > orchard (3. 33, 21. 10 Mg.hm-2) > sloping farmland (1. 68, 1. 35 Mg.hm-2) in small macroaggregates and microaggregates, and abandoned land(4. 32 Mg.hm-2) > orchard(4. 00 Mg.hm-2) > forest(3. 22 Mg.hm-2) > sloping farmland (2.37 Mg.hm-2) in silt + clay, forest and abandoned land were higher than orchard and sloping farmland in other three soil aggregates except silt + clay. It was observed that the level of organic carbon and labile organic carbon were decreased when bringing forest under cultivation to orchard or farmland, and augments on organic carbon and labile organic carbon were found after exchanging farmland to abandoned land. The most reverses of forest and abandoned land emerged in small macroaggregates, orchard and sloping farmland were in microaggregates. That was, during the

Characteristics of labile organic carbon fractions in reclaimed mine soils: Evidence from three reclaimed forests in the Pingshuo opencast coal mine, China.

PubMed

Yuan, Ye; Zhao, Zhongqiu; Li, Xuezhen; Wang, Yangyang; Bai, Zhongke

2018-02-01

The reclamation of discarded spoils has the potential to stimulate carbon (C) sequestration in reclaimed mine soils (RMSs). Nevertheless, to date the temporal dynamics of labile organic C fractions have not been sufficiently elucidated in RMSs. In this study, soil organic carbon (SOC) and labile organic C fractions, including microbial biomass organic C (MBC), easily oxidizable organic C (EOC) and dissolved organic C (DOC), were determined in Robinia pseudoacacia monoculture forests (reclamation periods of 0, 8, 10, 13, 15, 18 and 30years), Pinus tabuliformis forests (reclamation periods of 0, 10, 19, 23 and 25years) and Ulmus pumila forests (reclamation periods of 0, 18, 20 and 22years) situated on RMSs in the Pingshuo opencast coal mine, China. Changes in labile organic C fractions within the soil profiles (0-100cm) were also identified at the 18- or 19-year plots under the three monoculture forests. Our results showed that, SOC and labile organic C fractions, together with soil microbial quotient (SMQ) and C management index (CMI), increased with time since reclamation, indicating that the quality of RMSs improved over time after initial reclamation under the three forest types. R. pseudoacacia significantly increased the accretion of SOC and EOC in the early stage of reclamation while P. tabuliformis accelerated the accumulation of the MBC fraction. Results for U. pumila indicated that this species had a better ability to store C in RMSs 10years or more after reclamation. SOC and labile organic C fractions both had S-shaped distributions within the soil profiles (0-100cm), with the 0-20cm layer recording the highest values (P<0.05). Labile organic C fractions were closely associated and correlated with soil physicochemical properties; our results also showed that nitrogen played an important role in the development of labile organic C fractions. Overall, reclamation accelerated the accretion of both SOC and labile organic C fractions, results of which varied

Temperature and soil organic matter decomposition rates - synthesis of current knowledge and a way forward

Treesearch

Richard T. Conant; Michael Ryan; Goran I. Agren; Hannah E. Birge; Eric A. Davidson; Peter E. Eliasson; Sarah E. Evans; Serita D. Frey; Christian P. Giardina; Francesca M. Hopkins; Riitta Hyvonen; Miko U. F . Kirschbaum; Jocelyn M. Lavallee; Jens Leifeld; William J. Parton; Jessica Megan Steinweg; Matthew D. Wallenstein; J . A. Martin Wetterstedt; Mark A. Bradford

2011-01-01

The response of soil organic matter (OM) decomposition to increasing temperature is a critical aspect of ecosystem responses to global change. The impacts of climate warming on decomposition dynamics have not been resolved due to apparently contradictory results from field and lab experiments, most of which has focused on labile carbon with short turnover times. But...

Biotic and abiotic controls on diurnal fluctuations in labile soil phosphorus of a wet tropical forest.

PubMed

Vandecar, Karen L; Lawrence, Deborah; Wood, Tana; Oberbauer, Steven F; Das, Rishiraj; Tully, Katherine; Schwendenmann, Luitgard

2009-09-01

The productivity of many tropical wet forests is generally limited by bioavailable phosphorus (P). Microbial activity is a key regulator of P availability in that it determines both the supply of P through organic matter decomposition and the depletion of bioavailable P through microbial uptake. Both microbial uptake and mineralization occur rapidly, and their net effect on P availability varies with soil moisture, temperature, and soil organic matter quantity and quality. Exploring the mechanisms driving P availability at fine temporal scales can provide insight into the coupling of carbon, water, and nutrient cycles, and ultimately, the response of tropical forests to climate change. Despite the recognized importance of P cycling to the dynamics of wet tropical forests and their potential sensitivity to short-term fluctuations in bioavailable P, the diurnal pattern of P remains poorly understood. This study quantifies diurnal fluctuations in labile soil P and evaluates the importance of biotic and abiotic factors in driving these patterns. To this end, measurements of labile P were made every other hour in a Costa Rican wet tropical forest oxisol. Spatial and temporal variation in Bray-extractable P were investigated in relation to ecosystem carbon flux, soil CO2 efflux, soil moisture, soil temperature, solar radiation, and sap-flow velocity. Spatially averaged bi-hourly (every two hours) labile P ranged from 0.88 to 2.48 microg/g across days. The amplitude in labile P throughout the day was 0.61-0.82 microg/g (41-54% of mean P concentrations) and was characterized by a bimodal pattern with a decrease at midday. Labile P increased with soil CO2 efflux and soil temperature and declined with increasing sap flow and solar radiation. Together, soil CO2 efflux, soil temperature, and sap flow explained 86% of variation in labile P.

Labile and Non-labile Soil Carbon Fractions Equally Contributed to Carbon Changes under Long-term Fertilization

NASA Astrophysics Data System (ADS)

Liang, F.; Li, J.; Xu, M.; Huang, S.

2017-12-01

Soil organic carbon (SOC) storages are altered under long-term fertilization in croplands, it however remains unclear how fast- to slow-cycling SOC fractions each respond to fertilization practices. Based on five two-decade Chinese long-term fertilization experiments (GZL: Gongzhuling; ZZ: Zhengzhou; CQ: Chongqing; JX: Jinxian; QY: Qiyang) under three fertilization treatments (CK: cropping with no fertilizer input; NPK: chemical nitrogen, phosphorus and potassium fertilizers; and NPKM: NPK with manure input), we quantified very labile, labile, non-labile and total SOC stocks at 0-20cm soil depth. Results showed that SOC stocks varied among sites (GZL, JX, CQ > ZZ, QY) and generally increased with fertilizations (CK-1 at ZZ, GZL, QY, CQ and JX, respectively. The corresponding changes of the sum of very labile and labile SOC fractions were 2.6, 2.0, 1.8, 0.8 and -0.5 Mg ha-1 at ZZ, QY, GZL, CQ and JX, respectively. Also, NPKM increased total SOC stock by 18.3, 16.2, 14.4, 10.5, and 6.5 Mg ha-1 at QY, GZL, ZZ, CQ and JX, respectively. The corresponding changes of the sum of very labile and labile SOC fractions were 8.6, 6.8, 6.6, 3.2 and -1.6 Mg ha-1 at QY, GZL, ZZ, CQ and JX, respectively. These results suggested that about half or more than half SOC stock accretions under fertilization were induced by increase in non-labile SOC fractions. It thus informs the importance of non-labile SOC fractions in contributing to soil C sequestration under long-term fertilizations in Chinese croplands. Future research should improve our mechanistic understanding of biogeochemical transformation of non-labile organic C in soils.

Spectroscopic characteristics and biodegradability of cold and hot water-extractable soil organic matter under different land uses in subarctic Alaska

USDA-ARS?s Scientific Manuscript database

Cold (22 degrees C) and hot water (80 degrees C) extractions have been used to estimate labile organic C and N in soils. The aim of this study was to comparatively assess chemical characteristics and biodegradability of water extractable organic matter (WEOM) at 22 and 80 degrees C in 14 Alaskan soi...

Characterization and source identification of organic matter in view of land uses and heavy rainfall in the Lake Shihwa, Korea.

PubMed

Lee, Yeonjung; Hur, Jin; Shin, Kyung-Hoon

2014-07-15

The characteristics and sources of organic matter in water of the Lake Shihwa, which receives inputs from rural, urban, and industrial areas, were evaluated by examining the biodegradable organic carbon concentration, fluorescence spectra, and carbon and nitrogen isotope ratios, especially during rainy season and dry season. The organic matter transported from rural areas was of refractory nature, while that of industrial origin decomposed rapidly. As compared to the dry season, the organic matter in the rainy season was characterized by a reduced labile fraction. During the dry season, the autochthonous organic matter dominated in the lake, however, the contributions of allochthonous organic sources by industrial and rural areas significantly increased at rainy season. This investigation revealed that the transport of organic matter of anthropogenic origin to the Lake Shihwa was mainly influenced by heavy rainfall. Moreover, each anthropogenic source could differently influence the occurrence of organic matter in water of the Lake Shihwa. Copyright © 2014 Elsevier Ltd. All rights reserved.

Investigating microbial cycling of recalcitrant organic matter in marine sediments using natural isotope respirometry in a novel, carbon-free bioreactor

NASA Astrophysics Data System (ADS)

Mahmoudi, N.; Beaupre, S. R.; Pearson, A.

2016-02-01

Marine sediments harbor complex microbial communities that play a key role in the cycling of carbon and nutrients. Reactions initiated by microbial enzymes at the molecular scale drive the rate and extent of organic matter degradation to CO2 and CH4. Organic matter is comprised of multiple carbon pools with different intrinsic turnover times. It is hypothesized that microbes will degrade younger pools with more labile compounds, while older pools with refractory compounds will remain unutilized. However, many studies have shown that microbes are capable of respiring older, refractory pools of organic matter in a number of environments. In order to better understand microbial carbon cycling and the fate of recalcitrant organic matter, we constructed a novel bioreactor system to measure carbon isotopes during microbial degradation of complex organic matter. This system enables us to measure the natural isotopic signature (δ13C and Δ14C ) of microbially-respired CO2, thereby allowing us to determine the age of the organic matter that is being respired. We investigated microbial carbon utilization in sediments from Falmouth, MA and observed a pattern of successive microbial respiration such that several peaks appear over the course of a 7-day incubation. Δ14C signatures of CO2 fractions collected during incubation ranged from -185 to +70‰ with the majority of CO2 appearing to be modern. This indicates that the microbial community is primarily are respiring labile organic matter from fast cycling pools. Interestingly, the observation of multiple peaks with similar Δ14C signatures suggests that organic matter is degraded in a step-wise manner by a succession of microbial taxa. Illumina sequencing of 16S rRNA genes will identify these successions of bacteria (and archaea), while enzymatic analyses may help determine the metabolic pathways that correspond to each peak. Our study will provide a molecular-level framework for organic matter degradation and provide

Production of Dissolved Organic Matter During Doliolid Feeding

NASA Astrophysics Data System (ADS)

Castellane, N. J.; Paffenhofer, G. A.; Stubbins, A.

2016-02-01

The biological carbon pump (BCP) draws carbon dioxide out of the atmosphere and buries it at the seafloor. The efficiency of the BCP is determined in part by the sinking rates of particulate organic carbon (POC) from ocean surface waters. Zooplankton can package POC into fecal pellets with higher sinking rates than their food source (e.g. phytoplankton), increasing the efficiency of the BCP. However, dissolved organic carbon (DOC) is also produced as zooplankton ingest and egest food, reducing the efficiency of BCP. The pelagic tunicate Dolioletta gegenbauri (doliolid) is a gelatinous zooplankton found at high concentrations in shelf waters, including our study site: the South Atlantic Bight. Doliolids are efficient grazers capable of stripping large quantities of phytoplankton from the water column. To determine the balance between pellet formation and DOC production during feeding, doliolids (6-7 mm gonozooids) were placed in natural seawater amended with a live phytoplankton food source and incubated on a plankton wheel. Dissolved organic matter (DOM) released directly to the water as well as the water soluble fraction of pellet organic matter were quantified and optically characterized. Colored dissolved organic matter (CDOM) absorbance and fluorescence spectra revealed that doliolid feeding produces DOM with optical properties that are commonly indicative of newly produced, highly biolabile DOM of microbial origin. Based upon these optical characteristics, doliolid-produced DOM is expected to be highly bio-labile in the environment and therefore rapidly degraded by surface ocean microbes shunting phytoplankton-derived organic carbon out of the BCP and back to dissolved inorganic carbon.

Labile, dissolved and particulate PAHs and trace metals in wastewater: passive sampling, occurrence, partitioning in treatment plants.

PubMed

Gourlay-Francé, C; Bressy, A; Uher, E; Lorgeoux, C

2011-01-01

The occurrence and the partitioning of polycyclic aromatic hydrocarbons (PAHs) and seven metals (Al, Cd, Cr, Cu, Ni, Pb and Zn) were investigated in activated sludge wastewater treatment plants by means of passive and active sampling. Concentrations total dissolved and particulate contaminants were determined in wastewater at several points across the treatment system by means of grab sampling. Truly dissolved PAHs were sampled by means of semipermeable membrane devices. Labile (inorganic and weakly complexed) dissolved metals were also sampled using the diffusive gradient in thin film technique. This study confirms the robustness and the validity of these two passive sampling techniques in wastewater. All contaminant concentrations decreased in wastewater along the treatment, although dissolved and labile concentrations sometimes increased for substances with less affinity with organic matter. Solid-liquid and dissolved organic matter/water partitioning constants were estimated. The high variability of both partitioning constants for a simple substance and the poor relation between K(D) and K(OW) shows that the binding capacities of particles and organic matter are not uniform within the treatment and that other process than equilibrium sorption affect contaminant repartition and fate in wastewater.

Quantities and qualities of physical and chemical fractions of soil organic matter under a rye cover crop

USDA-ARS?s Scientific Manuscript database

To detect the effects of a rye cover crop on labile soil carbon, the light fraction, large particulate organic matter (POM), small POM, and two NaOH-extractable humic fractions were extracted from three depths of a corn soil in central Iowa having an overwinter rye cover crop treatment and a contro...

Seasonal changes in the chemical quality and biodegradability of dissolved organic matter exported from soils to streams in coastal temperate rainforest watersheds

Treesearch

Jason B. Fellman; Eran Hood; David V. D' Amore; Richard T. Edwards; Dan White

2009-01-01

The composition and biodegradability of streamwater dissolved organic matter (DOM) varies with source material and degree of transformation. We combined PARAFAC modeling of fluorescence excitation-emission spectroscopy and biodegradable dissolved organic carbon (BDOC) incubations to investigate seasonal changes in the lability of DOM along a soil-stream continuum in...

Carbon isotope fractionation of sapropelic organic matter during early diagenesis

USGS Publications Warehouse

Spiker, E. C.; Hatcher, P.G.

1984-01-01

Study of an algal, sapropelic sediment from Mangrove Lake, Bermuda shows that the mass balance of carbon and stable carbon isotopes in the major organic constituents is accounted for by a relatively straightforward model of selective preservation during diagenesis. The loss of 13C-enriched carbohydrates is the principal factor controlling the intermolecular mass balance of 13C in the sapropel. Results indicate that labile components are decomposed leaving as a residual concentrate in the sediment an insoluble humic substance that may be an original biochemical component of algae and associated bacteria. An overall decrease of up to about 4??? in the ?? 13C values of the organic matter is observed as a result of early diagenesis. ?? 1984.

Effect of a seasonal diffuse pollution migration on natural organic matter behavior in a stratified dam reservoir.

PubMed

Yu, Soon Ju; Lee, Jae Yil; Ha, Sung Ryong

2010-01-01

This article aims to describe the influence of diffuse pollution on the temporal and spatial characteristics of natural organic matter (NOM) in a stratified dam reservoir, the Daecheong Dam, on the basis of intensive observation results and the dynamic water quality simulation using CE-QUAL-W2. Turbidity is regarded as a comprehensive representation of allochothonous organic matter from diffuse sources in storm season because the turbidity concentration showed reasonable significance in a statistical correlation with the UV absorbance at 254 nm and total phosphorus. CE-QUAL-W2 simulation results showed good consistency with the observed data in terms of dissolved organic matter (DOM) including refractory dissolved organic carbon (RDOC) and labile DOC and also well explained the internal movement of constituents and stratification phenomenon in the reservoir. Instead turbidity and NOM were related well in the upper region of the reservoir according to flow distance, gradually as changing to dissolved form of organic matter, RDOM affected organic matter concentration of reservoir water quality compared to turbidity. To control the increase of soluble organic matters in the dam reservoir, appropriate dam water discharge gate operation provided effective measurement. Because of the gate operation let avoid the accumulation of organic matter within a dam reservoir by shorten of turbid regime retention time.

Carbohydrates and thermal analysis reflects changes in soil organic matter stability after forest expansion on abandoned grassland

NASA Astrophysics Data System (ADS)

Guidi, Claudia; Vesterdal, Lars; Cannella, David; Leifeld, Jens; Gianelle, Damiano; Rodeghiero, Mirco

2014-05-01

Grassland abandonment, followed by progressive forest expansion, is the dominant land-use change in the Southern Alps, Europe. Land-use change can affect not only the amount of organic matter (OM) in soil but also its composition and stability. Our objective was to investigate changes in organic matter properties after forest expansion on abandoned grasslands, combining analysis of carbohydrates, indicative of labile OM compounds with prevalent plant or microbial origin, with thermal analysis. Thermal analysis was used as a rapid assessment method for the characterization of SOM stability. A land-use gradient was investigated in four land-use types in the subalpine area of Trentino region, Italy: i) managed grassland, mown and fertilized for the past 100 years; ii) grassland abandoned since 10 years, with sparse shrubs and Picea abies saplings; iii) early-stage forest, dominated by P. abies and established on a grassland abandoned around 1970; iv) old forest, dominated by Fagus sylvatica and P. abies. Mineral soil was sampled at three subplots in each land use type with eight soil cores, which were subsequently pooled by depth (0-5 cm, 5-10 cm, 10-20 cm). Sugars were extracted from bulk soil samples through acid hydrolysis with H2SO4 (0.5 M). The analytical composition of sugar monomers was performed with HPAEC technology (Dionex ICS5000), equipped with PAD-detection. Thermal stability was assessed with a differential scanning calorimeter DSC100, heating soil samples up to 600°C at a heating rate of 10°C min-1 in synthetic air. Peak height (W g OC-1) of 1st DSC exotherm, dominated by burning of labile OM compounds, was used as thermal stability index. In the abandoned grassland, carbohydrates compounds accounted for a greater proportion of soil OC than in other land use types. Microbially derived sugars, as rhamnose and galactose, were more abundant in managed and abandoned grasslands compared with early-stage and old forest. The amount of thermally labile sugars

Comparison of metal lability in air-dried and fresh dewatered drinking water treatment residuals.

PubMed

Wang, Changhui; Pei, Yuansheng; Zhao, Yaqian

2015-01-01

In this work, the labilities of Al, As, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Sr, V and Zn in air-dried (for 60 days) and fresh dewatered WTRs were compared using the Toxicity Characteristic Leaching Procedure (TCLP), fractionation, in vitro digestion and a plant enrichment test. The results showed that the air-dried and fresh dewatered WTRs had different properties, e.g., organic matter composition and available nutrients. The air-dried and fresh dewatered WTRs were non-haf zardous according to the TCLP assessment method used in the United States; however, the metals in the two types of WTRs had different lability. Compared with the metals in the fresh dewatered WTRs, those in the air-dried WTRs tended to be in more stable fractions and also exhibited lower bioaccessibility and bioavailability. Therefore, air-drying can decrease the metal lability and thereby reduce the potential metal pollution risk of WTRs.

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

Labile dissolved organic carbon supply limits hyporheic denitrification

NASA Astrophysics Data System (ADS)

Zarnetske, Jay P.; Haggerty, Roy; Wondzell, Steven M.; Baker, Michelle A.

2011-12-01

We used an in situ steady state 15N-labeled nitrate (15NO3-) and acetate (AcO-) well-to-wells injection experiment to determine how the availability of labile dissolved organic carbon (DOC) as AcO-influences microbial denitrification in the hyporheic zone of an upland (third-order) agricultural stream. The experimental wells receiving conservative (Cl- and Br) and reactive (15NO3-) solute tracers had hyporheic median residence times of 7.0 to 13.1 h, nominal flowpath lengths of 0.7 to 3.7 m, and hypoxic conditions (<1.5 mg O2 L-1). All receiving wells demonstrated 15N2 production during ambient conditions, indicating that the hyporheic zone was an environment with active denitrification. The subsequent addition of AcO- stimulated more denitrification as evidenced by significant δ15N2 increases by factors of 2.7 to 26.1 in receiving wells and significant decreases of NO3- and DO in the two wells most hydrologically connected to the injection. The rate of nitrate removal in the hyporheic zone increased from 218 kg ha-1 yr-1 to 521 kg ha-1 yr-1 under elevated AcO- conditions. In all receiving wells, increases of bromide and 15N2 occurred without concurrent increases in AcO-, indicating that 100% of AcO- was retained or lost in the hyporheic zone. These results support the hypothesis that denitrification in anaerobic portions of the hyporheic zone is limited by labile DOC supply.

Submillimeter-scale heterogeneity of labile phosphorus in sediments characterized by diffusive gradients in thin films and spatial analysis.

PubMed

Meng, Yuting; Ding, Shiming; Gong, Mengdan; Chen, Musong; Wang, Yan; Fan, Xianfang; Shi, Lei; Zhang, Chaosheng

2018-03-01

Sediments have a heterogeneous distribution of labile redox-sensitive elements due to a drastic downward transition from oxic to anoxic condition as a result of organic matter degradation. Characterization of the heterogeneous nature of sediments is vital for understanding of small-scale biogeochemical processes. However, there are limited reports on the related specialized methodology. In this study, the monthly distributions of labile phosphorus (P), a redox-sensitive limiting nutrient, were measured in the eutrophic Lake Taihu by Zr-oxide diffusive gradients in thin films (Zr-oxide DGT) on a two-dimensional (2D) submillimeter level. Geographical information system (GIS) techniques were used to visualize the labile P distribution at such a micro-scale, showing that the DGT-labile P was low in winter and high in summer. Spatial analysis methods, including semivariogram and Moran's I, were used to quantify the spatial variation of DGT-labile P. The distribution of DGT-labile P had clear submillimeter-scale spatial patterns with significant spatial autocorrelation during the whole year and displayed seasonal changes. High values of labile P with strong spatial variation were observed in summer, while low values of labile P with relatively uniform spatial patterns were detected in winter, demonstrating the strong influences of temperature on the mobility and spatial distribution of P in sediment profiles. Copyright © 2017 Elsevier Ltd. All rights reserved.

Influence of sediment-organic matter quality on growth and polychlorobiphenyl bioavailability in Echinodermata (Amphiura filiformis)

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

Gunnarsson, J.S.; Granberg, M.E.; Nilsson, H.C.

Sediment total organic carbon (TOC) content is considered to be a primary food source for benthic invertebrates and a major factor influencing the partitioning and bioavailability of sediment-associated organic contaminants. Most studies report that both toxicity and uptake of sediment-associated contaminants by benthic organisms are inversely proportional to sediment TOC content. The aim of this study was to determine the importance of the TOC quality for the bioavailability of sediment-associated organic contaminants and the growth of benthic macrofauna. The common infaunal brittle star Amphiura filiformis was exposed to a base sediment covered by a {sup 14}C-polychlorobipenyl (3,3{prime}4,4{prime}-{sup 14}C-tetrachlorobiphenyl (TCB)) contaminatedmore » top layer (0--2 cm), enriched to the same TOC content with 31 g TOC/m{sup 2} of different quality and origin. The following carbon sources, ranging from labile to refractory, were used: (1) green macroalga (Ulva lactuca), (2) brown macroalga (Ascophyllum nodosum), (3) eelgrass (Zostera Marina), (4) phytoplankton (Ceratium spp.), and (5) lignins of terrestrial origin. Characterization of the organic matter quality was accomplished by measuring the content of amino acids, lipids, C, N, and polyphenolic compounds. The reactivity of the sedimentary organic matter was assessed by means of respiration and dissolved inorganic nitrogen flux measurements. The experiment was carried out in 1-L glass jars, each containing four brittle stars and the contaminated and enriched sediment. The jars were circulated in a flow-through mode with filtered seawater. Somatic growth (regeneration of a precut arm) and bioaccumulation of {sup 14}C-TCB were measured at 10 sampling occasions during 48 d of exposure. Growth rates, TCB uptake rates, and steady-state concentrations differed significantly between treatments and were correlated to the qualities of the organic substrates. The greatest TCB accumulation and growth were observed in

Mineral-associated organic matter: are we now on the right path to accurately measuring and modelling it?

NASA Astrophysics Data System (ADS)

Cotrufo, M. F.

2017-12-01

Mineral-associated organic matter (MAOM) is the largest and most persistent pool of carbon in soil. Understanding and correctly modeling its dynamic is key to suggest management practices that can augment soil carbon storage for climate change mitigation, as well as increase soil organic matter (SOM) stocks to support soil health on the long-term. In the Microbial Efficiency Mineral Stabilization (MEMS) framework we proposed that, contrary to what originally thought, this form of persistent SOM is derived from the labile components of plant inputs, through their efficient microbial processing. I will present results from several experiments using dual isotope labeling of plant inputs that largely confirm this opinion, and point to the key role of dissolved organic matter in MAOM formation, and to the dynamic nature of the outer layer of MAOM. I will also show how we are incorporating this understanding in a new SOM model, which uses physically defined measurable pools rather than turnover-defined pools to forecast C cycling in soil.

Microbial formation of labile organic carbon in Antarctic glacial environments

USGS Publications Warehouse

Smith, H.J.; Foster, R.; McKnight, D.M.; Lisle, John T.; Littmann, S.; Kuypers, M.M.M.; Foreman, C.M.

2017-01-01

Roughly six petagrams of organic carbon are stored within ice worldwide. This organic carbon is thought to be of old age and highly bioavailable. Along with storage of ancient and new atmospherically deposited organic carbon, microorganisms may contribute substantially to the glacial organic carbon pool. Models of glacial microbial carbon cycling vary from net respiration to net carbon fixation. Supraglacial streams have not been considered in models although they are amongst the largest ecosystems on most glaciers and are inhabited by diverse microbial communities. Here we investigate the biogeochemical sequence of organic carbon production and uptake in an Antarctic supraglacial stream in the McMurdo Dry Valleys using nanometre-scale secondary ion mass spectrometry, fluorescence spectroscopy, stable isotope analysis and incubation experiments. We find that heterotrophic production relies on highly labile organic carbon freshly derived from photosynthetic bacteria rather than legacy organic carbon. Exudates from primary production were utilized by heterotrophs within 24 h, and supported bacterial growth demands. The tight coupling of microbially released organic carbon and rapid uptake by heterotrophs suggests a dynamic local carbon cycle. Moreover, as temperatures increase there is the potential for positive feedback between glacial melt and microbial transformations of organic carbon.

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

The Effects of Permafrost Thaw on Organic Matter Quality and Availability Along a Hill Slope in Northeastern Siberia

NASA Astrophysics Data System (ADS)

Connolly, C. T.; Spawn, S.; Ludwig, S.; Schade, J. D.; Natali, S.

2014-12-01

Climate warming and permafrost thaw in northeastern Siberia are expected to change the quantity and quality of organic matter (OM) transported through watersheds, releasing previously frozen carbon (C) to biologically available pool. Hill slopes have shown to influence the distribution of OM, resulting in a downhill accumulation of available C and nutrients relative to uphill. Here we examine how future permafrost thaw will change OM quality and availability along a hill slope in a larch-dominated watershed. We collected soils from the thawed organic and mineral layers, and 1m deep permafrost cores for dissolved organic C (DOC) and total dissolved N (TDN), C composition from measures of colored dissolved organic matter (CDOM), DOC lability from biodegradable DOC (BDOC) incubations, C and nutrient availability from extracellular-enzyme assays (EEA's), and microbial respiration from aerobic soil incubations. Here we show that organic soils (O), in comparison to mineral soils (M) and permafrost (P) are the most abundant source of C (avg O DOC: 51.6mg/L), exhibiting low molecular complexity (avg O SUVA254: 4.05) and high quality. Evidence suggests permafrost OM may be an equally abundant, and more labile source of C than mineral soils (highest P DOC: 16.1 mg/L, lowest P SUVA254: 6.32; median M DOC: 18.5 mg/L, median M SUVA254: 24.0). Furthermore, we demonstrate that there may be a positive relationship in the rate of C mineralization and distance downhill, showing 15-30% greater CO2 production/gC downhill relative to uphill. Evidence also supports a similar relationship in permafrost DOC content and molecular complexity, showing more DOC of a lower complexity further downhill. This indicates DOC transport may have been occurring through the active layer and downhill during ice-rich permafrost formation, and may supply a labile source of carbon to lowland areas and adjacent stream networks upon thaw.

Sedimentary organic matter in two Spitsbergen fjords: Terrestrial and marine contributions based on carbon and nitrogen contents and stable isotopes composition

NASA Astrophysics Data System (ADS)

Koziorowska, Katarzyna; Kuliński, Karol; Pempkowiak, Janusz

2016-02-01

that fresh, labile organic matter is the base of the trophic pyramid. The conclusion regarding a more complex food web in the Horsund, based on larger δ15Ntot values, is further substantiated by the larger proportion of autochthonous, labile organic matter found in the Hornsund's sediments.

Peatland Organic Matter Chemistry Trends Over a Global Latitudinal Gradient

NASA Astrophysics Data System (ADS)

Verbeke, B. A.; Hodgkins, S. B.; Carson, M. A.; Lamit, L. J.; Lilleskov, E.; Chanton, J.

2017-12-01

Peatlands contain a significant amount of the global soil carbon, and the climate feedback of carbon cycling within these peatland systems is still relatively unknown. Organic matter composition of peatlands plays a major role in determining carbon storage, and while high latitude peatlands seem to be the most sensitive to climate change, a global picture of peat organic matter chemistry is required to improve predictions and models of greenhouse gas emissions fueled by peatland decomposition. The objective of this research is to test the hypothesis that carbohydrate content of peatlands near the equator will be lower than high latitude peatlands, while aromatic content will be higher. As a part of the Global Peatland Microbiome Project (GPMP), around 2000 samples of peat from 10 to 70 cm across a latitudinal gradient of 79 N to 53 S were measured with Fourier transform infrared spectroscopy (FTIR) to examine the organic matter functional groups of peat. Carbohydrate and aromatic content, as determined by FTIR, are useful proxies of decomposition potential and recalcitrance, respectively. We found a highly significant relationship between carbohydrate and aromatic content, latitude, and depth. Carbohydrate content of high latitude sites were significantly greater than at sites near the equator, in contrast to aromatic content which showed the opposite trend. It is also clear that carbohydrate content decreases with depth while aromatic content increases with depth. Higher carbohydrate content at higher latitudes indicates a greater potential for lability and resultant mineralization to form the greenhouse gases, carbon dioxide and methane, whereas the composition of low latitude peatlands is consistent with their apparent stability. We speculate that the combination of low carbohydrates and high aromatics at warmer locations near the equator could foreshadow the organic matter composition of high latitude peat transitioning to a more recalcitrant form with a

Effect of warming on the degradation and production of low-molecular-weight labile organic carbon in an Arctic tundra soil

DOE PAGES

Yang, Ziming; Wullschleger, Stan D.; Liang, Liyuan; ...

2016-01-16

The fate of soil organic carbon (SOC) stored in the Arctic permafrost is a key concern as temperatures continue to rise in the northern hemisphere. Studies and conceptual models suggest that SOC degradation is affected by the composition of SOC, but it is unclear exactly what portions of SOC are vulnerable to rapid breakdown and what mechanisms may be controlling SOC degradation upon permafrost thaw. Here, we examine the dynamic consumption and production of labile SOC in an anoxic incubation experiment using soil samples from the active layer at the Barrow Environmental Observatory, Barrow, Alaska, USA. Free-reducing sugars, alcohols, andmore » low-molecular-weight (LMW) organic acids were analyzed during incubation at either –2 or 8 °C for up to 240 days. Results show that simple sugar and alcohol SOC largely account for the initial rapid release of CO 2 and CH 4 through anaerobic fermentation, whereas the fermentation products, acetate and formate, are subsequently utilized as primary substrates for methanogenesis. Iron(III) reduction is correlated to acetate production and methanogenesis, suggesting its important role as an electron acceptor in tundra SOC respiration. These observations are further supported in a glucose addition experiment, in which rapid CO 2 and CH 4 production occurred concurrently with rapid production and consumption of labile organics such as acetate. However, addition of tannic acid, as a more complex organic substrate, showed little influence on the overall production of CO 2 and CH 4 and organic acids. Together our study shows that LMW labile organics in SOC control the initial rapid release of green-house gases upon warming. We thus present a conceptual framework for the labile SOC transformations and their relations to fermentation, iron reduction and methanogenesis, thereby providing the basis for improved model prediction of climate feedbacks in the Arctic.« less

[Effects of understory removal on soil labile organic carbon pool in a Cinnamomum camphora plantation].

PubMed

Wu, Ya-Cong; Li, Zheng-Cai; Cheng, Cai-Fang; Liu, Rong-Jie; Wang, Bin; Geri, Le-Tu

2013-12-01

Taking a 48-year-old Cinnamomum camphora plantation in the eastern area of our subtropics as test object, this paper studied the labile organic carbon contents and their ratios to the total organic carbon (TOC) in 0-60 cm soil layer under effects of understory removal (UR). As compared with no understory removal (CK), the soil TOC and easily-oxidized carbon (EOC) contents under UR decreased, with a decrement of 4.8% - 34.1% and 27.1% - 36.2%, respectively, and the TOC and EOC contents had a significant difference in 0-10 cm and 0-20 cm layers, respectively. The water-soluble organic carbon (WSOC) (except in 0-10 cm and 10-20 cm layers) and light fraction organic matter (LFOM) under UR increaesd, but the difference was not significant. The ratio of soil WSOC to soil TOC in UR stand was higher than that in CK stand, while the ratio of soil EOC to soil TOC showed an opposite trend. In the two stands, soil WSOC, EOC, and LFOM had significant or extremely significant correlations with soil TOC, and the correlation coefficients of soil EOC and LFOM with soil TOC were higher in UR stand than in CK, but the correlation coefficient between soil WSOC and TOC was in opposite. The soil EOC, LFOM, and TOC in the two stands were significantly or extremely significantly correlated with soil nutrients, but the soil WSOC in UR stand had no significant correlations with soil hydrolyzable N, available P, exchangeable Ca, and exchangeable Mg.

[Effects of Chinese prickly ash orchard on soil organic carbon mineralization and labile organic carbon in karst rocky desertification region of Guizhou province].

PubMed

Zhang, Wen-Juan; Liao, Hong-Kai; Long, Jian; Li, Juan; Liu, Ling-Fei

2015-03-01

Taking 5-year-old Chinese prickly ash orchard (PO-5), 17-year-old Chinese prickly ash orchard (PO- 17), 30-year-old Chinese prickly ash orchard (PO-30) and the forest land (FL, about 60 years) in typical demonstration area of desertification control test in southwestern Guizhou as our research objects, the aim of this study using a batch incubation experiment was to research the mineralization characteristics of soil organic carbon and changes of the labile soil organic carbon contents at different depths (0-15 cm, 15-30 cm, and 30-50 cm). The results showed that: the cumulative mineralization amounts of soil organic carbon were in the order of 30-year-old Chinese prickly ash orchard, the forest land, 5-year-old Chinese prickly ash orchard and 17-year-old Chinese prickly ash orchard at corresponding depth. Distribution ratios of CO2-C cumulative mineralization amount to SOC contents were higher in Chinese prickly ash orchards than in forest land at each depth. Cultivation of Chinese prickly ash in long-term enhanced the mineralization of soil organic carbon, and decreased the stability of soil organic carbon. Readily oxidized carbon and particulate organic carbon in forest land soils were significantly more than those in Chinese prickly ash orchards at each depth (P < 0.05). With the increasing times of cultivation of Chinese prickly ash, the contents of readily oxidized carbon and particulate organic carbon first increased and then declined at 0-15 cm and 15-30 cm depth, respectively, but an opposite trend was found at 30-50 cm depth. At 0-15 cm and 15-30 cm, cultivation of Chinese prickly ash could be good for improving the contents of labile soil organic carbon in short term, but it was not conducive in long-term. In this study, we found that cultivation of Chinese prickly ash was beneficial for the accumulation of labile organic carbon at the 30-50 cm depth.

Transformation of soil organic matter in leached chernozems under minimized treatment in the forest-steppe of West Siberia

NASA Astrophysics Data System (ADS)

Sharkov, I. N.; Samokhvalova, L. M.; Mishina, P. V.

2016-07-01

Changes in the contents of total organic carbon and the carbon of easily mineralizable fractions of organic matter (labile humus, detritus, and mortmass) in the layers of 0-10, 10-25, and 0-25 cm were studied in leached chernozems ((Luvic Chernozems (Loamic, Aric)) subjected to deep plowing and surface tillage for nine years. In the layer of 0-25 cm, the content of Corg did not show significant difference between these two treatments and comprised 3.68-3.92% in the case of deep plowing and 3.63-4.08% in the case of surface tillage. Tillage practices greatly affected the distribution of easily mineralizable fractions of organic matter in the layers of 0-10 and 10-25 cm, though the difference between two treatments for the entire layer (0-25 cm) was insignificant. Surface tillage resulted in the increase in the contents of mortmass (by 59%), detritus (by 32%), and labile humus (by 8%) in the layer of 0-10 cm in comparison with deep plowing. At the same time, the contents of these fractions in the layer of 10-25 cm in the surface tillage treatment decreased by 67, 46, and 3%, respectively. The estimate of the nitrogen-mineralizing capacity made according to the data on the uptake of soil nitrogen by oat plants in a special greenhouse experiment confirmed the observed regularities of the redistribution of easily mineralizable organic matter fractions by the soil layers. In case of surface tillage, it increased by 23% in the layer of 0-10 cm; for the layer of 0-25 cm, no significant differences in the uptake of nitrogen by oat plants were found for the two studied treatments.

Enzymatic regulation of organic matter metabolism in Siberia's Kolyma River Watershed

NASA Astrophysics Data System (ADS)

Mann, P. J.; Sobczak, W.; Vonk, J. E.; Davydova, A.; Schade, J.; Bulygina, E.; Davydov, S.; Zimov, N.; Holmes, R. M.

2012-04-01

Arctic soils contain vast amounts of ancient organic carbon stored in permafrost that can be unlocked and remobilised via permafrost thaw and bacterial degradation. The mechanisms regulating the release and fate of this carbon are important to understand if we wish to predict future changes in the global carbon cycle. Microbial communities release enzymes into the environment (ectoenzymes) as a means of degrading organic matter and to acquire carbon, nitrogen and phosphorus for assimilation. We measured potential activities of a suite of ectoenzymes within surface waters collected from a range of streams and rivers throughout the Kolyma River basin, Siberia. Ectoenzyme activities were additionally measured in Kolyma river waters collected at three distinct periods of the hydrograph (under-ice, freshet and summer conditions). Seven enzymes were studied allowing bacterial requirements for a wide range of compounds including lignin, carbohydrates, proteins and cellulose to be assessed. Concurrent measurements of DOC lability were conducted using biological oxygen demand assays conducted over 5 days (BOD). Phenol oxidase activity was found to strongly correlate to BOD (r2=0.68) and stream CO2 concentration (r2=0.76) across all of the study sites, suggesting the rate of phenolic degradation may be a controlling factor in organic carbon metabolism. The activity rate in ectoenzymes that catalyze phosphate, lignin and carbon substrates varied significantly within the Kolyma river over the hydrograph, suggesting that seasonal changes in organic matter composition may also shift the limiting resource for bacterial degradation. Extremely high activity rates in ectoenzymes that catalyze lignin, chitin, cellulose and proteins were measured in waters draining permafrost ice complexes. It is apparent that organic carbon is continually processed throughout the stream network, and that its ultimate fate is linked to organic matter composition. We demonstrate that organic carbon

Bacterial carbon use plasticity, phylogenetic diversity and the priming of soil organic matter.

PubMed

Morrissey, Ember M; Mau, Rebecca L; Schwartz, Egbert; McHugh, Theresa A; Dijkstra, Paul; Koch, Benjamin J; Marks, Jane C; Hungate, Bruce A

2017-08-01

Microorganisms perform most decomposition on Earth, mediating carbon (C) loss from ecosystems, and thereby influencing climate. Yet, how variation in the identity and composition of microbial communities influences ecosystem C balance is far from clear. Using quantitative stable isotope probing of DNA, we show how individual bacterial taxa influence soil C cycling following the addition of labile C (glucose). Specifically, we show that increased decomposition of soil C in response to added glucose (positive priming) occurs as a phylogenetically diverse group of taxa, accounting for a large proportion of the bacterial community, shift toward additional soil C use for growth. Our findings suggest that many microbial taxa exhibit C use plasticity, as most taxa altered their use of glucose and soil organic matter depending upon environmental conditions. In contrast, bacteria that exhibit other responses to glucose (reduced growth or reliance on glucose for additional growth) clustered strongly by phylogeny. These results suggest that positive priming is likely the prototypical response of bacteria to sustained labile C addition, consistent with the widespread occurrence of the positive priming effect in nature.

Biochemical Characteristics of Organic Matter in a Guano Concretion of Late Miocene or Pliocene Age from Manchester Parish in Jamaica

PubMed Central

Spence, Adrian; Hanson, Richard E.; Johnson, Toni; Robinson, Claion; Annells, Richard N.

2013-01-01

The biogeochemical fate of organic matter (OM) entering soils is an important issue that must be examined to better understand its roles in nitrogen cycling and as a natural modulator of soil-atmospheric carbon fluxes. Despite these critical roles, there are uncertainties in estimating the contribution of this feedback mechanism due in part to a lack of molecular-level information regarding the origin and labile and refractory inventories of OM in soils. In this study, we used a multi-analytical approach to determine molecular-level information for the occurrence and stabilization of OM in a bird guano concretion of the Late Miocene or Pliocene age in Jamaica. We determined the specific organic structures persisting in the concretion and the possible contribution of fossil organic matter to the OM pool in modern environments. Our results indicate that aliphatic species, presumably of a highly polymethylenic nature [(CH2)n], may significantly contribute to the stable soil-C pool. Although not as significant, proteins and carbohydrates were also enriched in the sample, further suggesting that fossil organic matter may contribute to carbon and nitrogen pools in present day soil organic matter. PMID:23843688

Biochemical characteristics of organic matter in a guano concretion of late miocene or pliocene age from manchester parish in Jamaica.

PubMed

Spence, Adrian; Hanson, Richard E; Johnson, Toni; Robinson, Claion; Annells, Richard N

2013-01-01

The biogeochemical fate of organic matter (OM) entering soils is an important issue that must be examined to better understand its roles in nitrogen cycling and as a natural modulator of soil-atmospheric carbon fluxes. Despite these critical roles, there are uncertainties in estimating the contribution of this feedback mechanism due in part to a lack of molecular-level information regarding the origin and labile and refractory inventories of OM in soils. In this study, we used a multi-analytical approach to determine molecular-level information for the occurrence and stabilization of OM in a bird guano concretion of the Late Miocene or Pliocene age in Jamaica. We determined the specific organic structures persisting in the concretion and the possible contribution of fossil organic matter to the OM pool in modern environments. Our results indicate that aliphatic species, presumably of a highly polymethylenic nature [(CH2)n], may significantly contribute to the stable soil-C pool. Although not as significant, proteins and carbohydrates were also enriched in the sample, further suggesting that fossil organic matter may contribute to carbon and nitrogen pools in present day soil organic matter.

Detrital Controls on Dissolved Organic Matter in Soils: A Field Experiment

NASA Astrophysics Data System (ADS)

Lajtha, K.; Crow, S.; Yano, Y.; Kaushal, S.; Sulzman, E.; Sollins, P.

2004-12-01

We established a long-term field study in an old growth coniferous forest at the H.J. Andrews Experimental Forest, OR, to address how detrital quality and quantity control soil organic matter accumulation and stabilization. The Detritus Input and Removal Treatments (DIRT) plots consist of treatments that double leaf litter, double woody debris inputs, exclude litter inputs, or remove root inputs via trenching. We measured changes in soil solution chemistry with depth, and conducted long-term incubations of bulk soils and soil density fractions from different treatments in order to elucidate effects of detrital inputs on the relative amounts and lability of different soil C pools. In the field, the effect of adding woody debris was to increase dissolved organic carbon (DOC) concentrations in O-horizon leachate and at 30 cm, but not at 100 cm, compared to control plots, suggesting increased rates of DOC retention with added woody debris. 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; %hydrophobic DOM decreased significantly with depth, and hydrophilic DOM had a much lower and narrower C:N ratio. Although laboratory extracts of different litter types showed differences in DOM chemistry, percent hydrophobic DOM did not differ among detrital treatments in the field, suggesting microbial equalization of DOM leachate in the field. In long-term laboratory incubations, light fraction material did not have higher rates of respiration than heavy fraction or bulk soils, suggesting that physical protection or N availability controls different turnover times of heavy fraction material, rather than differences in chemical lability. Soils from plots that had both above- and below-ground litter inputs excluded had significantly lower DOC loss rates, and a non-significant trend for lower

A simple approach to estimate daily loads of total, refractory, and labile organic carbon from their seasonal loads in a watershed

Treesearch

Ying Ouyang; Johnny M. Grace; Wayne C. Zipperer; Jeff Hatten; Janet Dewey

2018-01-01

Loads of naturally occurring total organic carbons (TOC), refractory organic carbon (ROC), and labile organic carbon (LOC) instreams control the availability of nutrients and the solubility and toxicity of contaminants and affect biological activities throughabsorption of light and complex metals with production of carcinogenic compounds....

Seasonal Dynamics of Soil Labile Organic Carbon and Enzyme Activities in Relation to Vegetation Types in Hangzhou Bay Tidal Flat Wetland

PubMed Central

Shao, Xuexin; Yang, Wenying; Wu, Ming

2015-01-01

Soil labile organic carbon and soil enzymes play important roles in the carbon cycle of coastal wetlands that have high organic carbon accumulation rates. Soils under three vegetations (Phragmites australis, Spartina alterniflora, and Scirpusm mariqueter) as well as bare mudflat in Hangzhou Bay wetland of China were collected seasonally. Seasonal dynamics and correlations of soil labile organic carbon fractions and soil enzyme activities were analyzed. The results showed that there were significant differences among vegetation types in the contents of soil organic carbon (SOC) and dissolved organic carbon (DOC), excepting for that of microbial biomass carbon (MBC). The P. australis soil was with the highest content of both SOC (7.86 g kg-1) and DOC (306 mg kg-1), while the S. mariqueter soil was with the lowest content of SOC (6.83 g kg-1), and the bare mudflat was with the lowest content of DOC (270 mg kg-1). Soil enzyme activities were significantly different among vegetation types except for urease. The P. australis had the highest annual average activity of alkaline phosphomonoesterase (21.4 mg kg-1 h-1), and the S. alterniflora had the highest annual average activities of β-glycosidase (4.10 mg kg-1 h-1) and invertase (9.81mg g-1 24h-1); however, the bare mudflat had the lowest activities of alkaline phosphomonoesterase (16.2 mg kg-1 h-1), β-glycosidase (2.87 mg kg-1 h-1), and invertase (8.02 mg g-1 24h-1). Analysis also showed that the soil labile organic carbon fractions and soil enzyme activities had distinct seasonal dynamics. In addition, the soil MBC content was significantly correlated with the activities of urease and β-glucosidase. The DOC content was significantly correlated with the activities of urease, alkaline phosphomonoesterase, and invertase. The results indicated that vegetation type is an important factor influencing the spatial-temporal variation of soil enzyme activities and labile organic carbon in coastal wetlands. PMID:26560310

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

Organic matter-solid phase interactions are critical for predicting arsenic release and plant uptake in Bangladesh paddy soils.

PubMed

Williams, Paul N; Zhang, Hao; Davison, William; Meharg, Andrew A; Hossain, Mahmud; Norton, Gareth J; Brammer, Hugh; Islam, M Rafiqul

2011-07-15

Agroecological zones within Bangladesh with low levels of arsenic in groundwater and soils produce rice that is high in arsenic with respect to other producing regions of the globe. Little is known about arsenic cycling in these soils and the labile fractions relevant for plant uptake when flooded. Soil porewater dynamics of field soils (n = 39) were recreated under standardized laboratory conditions to investigate the mobility and interplay of arsenic, Fe, Si, C, and other elements, in relation to rice grain element composition, using the dynamic sampling technique diffusive gradients in thin films (DGT). Based on a simple model using only labile DGT measured arsenic and dissolved organic carbon (DOC), concentrations of arsenic in Aman (Monsoon season) rice grain were predicted reliably. DOC was the strongest determinant of arsenic solid-solution phase partitioning, while arsenic release to the soil porewater was shown to be decoupled from that of Fe. This study demonstrates the dual importance of organic matter (OM), in terms of enhancing arsenic release from soils, while reducing bioavailability by sequestering arsenic in solution.

Effect of inorganic and organic copper fertilizers on copper nutrition in Spinacia oleracea and on labile copper in soil.

PubMed

Obrador, Ana; Gonzalez, Demetrio; Alvarez, Jose M

2013-05-22

To ensure an optimal concentration of Cu in food crops, the effectiveness of eight liquid Cu fertilizers was studied in a spinach ( Spinacia oleracea L.) crop grown on Cu-deficient soil under greenhouse conditions. Plant dry matter yields, Cu concentrations in spinach plants (total and morpholino acid (MES)- and ethylenediaminedisuccinic acid (EDDS)-extractable), and Cu uptakes were studied. The behavior of Cu in soil was evaluated by both single and sequential extraction procedures. The highest quantities of Cu in labile forms in the soil, total uptakes, and Cu concentrations in the plants were associated with the application of the two sources that contained Cu chelated by EDTA and/or DTPA. The fertilizers containing these Cu chelates represent a promising approach to achieve high levels of agronomic biofortification. The stronger correlations obtained between low-molecular-weight organic acid-extractable Cu in soil and the Cu concentrations and Cu uptakes by the plants show the suitability of this soil extraction method for predicting Cu available to spinach plants.

Release and microbial degradation of dissolved organic matter (DOM) from the macroalgae Ulva prolifera.

PubMed

Zhang, Tao; Wang, Xuchen

2017-12-15

Release and microbial degradation of dissolved organic matter (DOM) and chromophoric dissolved organic matter (CDOM) from the macroalgae Ulva prolifera were studied in laboratory incubation experiments. The release of DOM and CDOM from Ulva prolifera was a rapid process, and hydrolysis played an important role in the initial leaching of the organic compounds from the algae. Bacterial activity enhanced the release of DOM and CDOM during degradation of the algae and utilization of the released organic compounds. It is calculated that 43±2% of the C and 63±3% of the N from Ulva prolifera's biomass were released during the 20-day incubation, and 65±3% of the released C and 87±4% of the released N were utilized by bacteria. In comparison, only 18±1% of the algae's C and 17±1% of its N were released when bacterial activities were inhibited. The fluorescence characteristics of the CDOM indicate that protein-like DOM was the major organic component released from Ulva prolifera that was highly labile and biodegradable. Bacteria played an important role in regulating the chemical composition and fluorescence characteristics of the DOM. Our study suggests that the release of DOM from Ulva prolifera provides not only major sources of organic C and N, but also important food sources to microbial communities in coastal waters. Copyright © 2017 Elsevier Ltd. All rights reserved.

Nanoscale Structure Of Organic Matter Explain Its Recalcitrance To Degradation

NASA Astrophysics Data System (ADS)

Spagnol, M.; Salati, S.; Papa, G.; Tambone, F.; Adani, F.

2009-04-01

-Joyner-Halenda) equation were applied respectively to measure specific surface area and mesoporosity. Macromolecular composition of OM was investigated by using CP MAS 13NMR and wet chemical analyses. Results obtained showed how OM evolved increasing microporosity and decreasing meso porosity. This was the result of the preservation of recalcitrant OM versus degradation of the more labile fraction, suggesting that the more recalcitrant fraction was characterized by high microporosity. Another confirmation of these results comes from the analysis of the same OM after the removing of the labile fraction by acid hydrolysis to discover the core-OM, which was characterized by a higher microposrosity with respect the bulk OM. In conclusion it can be showed that not only the chemical composition but, also, the physical structure of organic matter defined its recalcitrance. References Adani, F.; Spagnol, M.; Genevini, P. Biogeochemistry 2006, 78, 85-96. Himmel, M.E.; Ding S.Y.; Johnson, D.K.; Adney, W.S.; Nimlos, M.R.; Brady, J.W.; Foust, T.D. Sci. 2007, 315, 804-807. Chesson, A. In Driven by nature Plant Litter Quality and Decomposition. Cadisch, G.; Giller, K.E. Eds.; CAB International: Wallinford, UK 1997, pp 47-66. Zimmerman, A.R.; Goyne, K.W.; Chorover, J, Komarneni, S.; Brantley, S.L. Org Geochem. 2004, 35, 355-375.

soil organic matter fractionation

NASA Astrophysics Data System (ADS)

Osat, Maryam; Heidari, Ahmad

2010-05-01

Carbon is essential for plant growth, due to its effects on other soil properties like aggregation. Knowledge of dynamics of organic matter in different locations in the soil matrix can provide valuable information which affects carbon sequestration and soil the other soil properties. Extraction of soil organic matter (SOM) fractions has been a long standing approach to elucidating the roles of soil organic matter in soil processes. Several kind fractionation methods are used and all provide information on soil organic matter function. Physical fractionation capture the effects on SOM dynamics of the spatial arrangement of primary and secondary organomineral particles in soil while chemical fractionation can not consider the spatial arrangement but their organic fractions are suitable for advanced chemical characterization. Three method of physical separation of soil have been used, sieving, sedimentation and densitometry. The distribution of organic matter within physical fractions of the soil can be assessed by sieving. Sieving separates soil particles based strictly on size. The study area is located on north central Iran, between 35° 41'- 36° 01' N and 50° 42'- 51° 14' E. Mean annual precipitation about 243.8 mm and mean annual air temperature is about 14.95 °C. The soil moisture and temperature regime vary between aridic-thermic in lower altitudes to xeric-mesic in upper altitudes. More than 36 surface soil samples (0-20 cm) were collected according to land-use map units. After preliminary analyzing of samples 10 samples were selected for further analyses in five size fractions and three different time intervals in September, January and April 2008. Fractionation carried out by dry sieving in five classes, 1-2 mm, 0.5-1 mm, 270 μm-0.5mm, 53-270 μm and <53 μm. Organic matter and C/N ratio were determined for all fractions at different time intervals. Chemical fractionation of organic matter also carried out according to Tan (2003), also Mineralogical

Sources, Ages, and Alteration of Organic Matter in Estuaries.

PubMed

Canuel, Elizabeth A; Hardison, Amber K

2016-01-01

Understanding the processes influencing the sources and fate of organic matter (OM) in estuaries is important for quantifying the contributions of carbon from land and rivers to the global carbon budget of the coastal ocean. Estuaries are sites of high OM production and processing, and understanding biogeochemical processes within these regions is key to quantifying organic carbon (Corg) budgets at the land-ocean margin. These regions provide vital ecological services, including nutrient filtration and protection from floods and storm surge, and provide habitat and nursery areas for numerous commercially important species. Human activities have modified estuarine systems over time, resulting in changes in the production, respiration, burial, and export of Corg. Corg in estuaries is derived from aquatic, terrigenous, and anthropogenic sources, with each source exhibiting a spectrum of ages and lability. The complex source and age characteristics of Corg in estuaries complicate our ability to trace OM along the river-estuary-coastal ocean continuum. This review focuses on the application of organic biomarkers and compound-specific isotope analyses to estuarine environments and on how these tools have enhanced our ability to discern natural sources of OM, trace their incorporation into food webs, and enhance understanding of the fate of Corg within estuaries and their adjacent waters.

Labile Dissolved Organic Carbon Availability Controls Hyporheic Denitrification: a 15N Tracer Study

NASA Astrophysics Data System (ADS)

Zarnetske, J. P.; Haggerty, R.; Wondzell, S. M.; Baker, M. A.

2009-12-01

We used an in situ 15N-labeled nitrate (15NO3-) and acetate injection experiment to determine how the availability of labile dissolved organic carbon (DOC) as acetate influences microbial denitrification in the hyporheic zone (HZ) of an upland (3rd-order) agricultural stream. A 48 h steady-state injection of a conservative tracer, chloride, and 15NO3- was used to quantify ambient HZ denitrification via 15N2 production. Following ambient plateau measurements of denitrification during the first 24 h, a second conservative tracer, bromide, and labile DOC source, acetate, were co-injected for an additional 24 h to measure HZ denitrification under increased DOC supply. Conservative tracers were observed at 4 of the 6 down gradient wells. Receiving wells represented HZ median residence times of 7.0 to 13.1 h, nominal flowpath lengths of 0.7 to 3.7 m, and hypoxic conditions (7.5 to 9.3 mg-O2 L-1 deficit). All 4 receiving wells demonstrated 15N2 production during ambient conditions indicating that the HZ was an active denitrification environment. Acetate addition stimulated significant increases in 15N2 production by factors of 2.7 to 26.1 in all receiving wells, and significant decreases of NO3- and DOC aromaticity (via SUVA254) in the two wells most hydrologically connected to the injection. In all receiving wells, increases of bromide and 15N2 production occurred without concurrent increases in acetate indicating that 100% of acetate was retained in the HZ, a portion of which is due to biological consumption. These results support our hypothesis that microbial denitrification in anaerobic portions of the hyporheic zone is limited by labile DOC supply.

Use of photoacoustic mid-infrared spectroscopy to characterize soil properties and soil organic matter stability

NASA Astrophysics Data System (ADS)

Peltre, Clement; Bruun, Sander; Du, Changwen; Stoumann Jensen, Lars

2014-05-01

The persistence of soil organic matter (SOM) is recognized as a major ecosystem property due to its key role in earth carbon cycling, soil quality and ecosystem services. SOM stability is typically studied using biological methods such as measuring CO2-C evolution from microbial decomposition of SOM during laboratory incubation or by physical or chemical fractionation methods, allowing the separation of a labile fraction of SOM. However these methods are time consuming and there is still a need for developing reliable techniques to characterize SOM stability, providing both quantitative measurements and qualitative information, in order to improve our understanding of the mechanisms controlling SOM persistence. Several spectroscopic techniques have been used to characterize and predict SOM stability, such as near infrared reflectance spectroscopy (NIRS) and diffuse reflectance mid-infrared spectroscopy (DRIFT). The latter allows a proper identification of spectral regions corresponding to vibrations of specific molecular or functional groups associated with SOM lability. However, reflectance spectroscopy for soil analyses raises some difficulties related to the low reflectance of soils, and to the high influence of particle size. In the last three decades, the progresses in microphone sensitivity dramatically increased the performance of photoacoustic Fourier transform mid-infrared spectroscopy (FTIR-PAS). This technique offers benefits over reflectance spectroscopy techniques, because particle size and the level of sample reflectance have little effect of on the PAS signal, since FTIR-PAS is a direct absorption technique. Despite its high potential for soil analysis, only a limited number of studies have so far applied FTIR-PAS for soil characterization and its potential for determining SOM degradability still needs to be investigated. The objective of this study was to assess the potential of FTIR-PAS for the characterization of SOM decomposability during

Assessing SOC labile fractions through respiration test, density-size fractionation and thermal analysis - A comparison of methods

NASA Astrophysics Data System (ADS)

Soucemarianadin, Laure; Cécillon, Lauric; Chenu, Claire; Baudin, François; Nicolas, Manuel; Savignac, Florence; Barré, Pierre

2017-04-01

Soil organic matter (SOM) is the biggest terrestrial carbon reservoir, storing 3 to 4 times more carbon than the atmosphere. However, despite its major importance for climate regulation SOM dynamics remains insufficiently understood. For instance, there is still no widely accepted method to assess SOM lability. Soil respiration tests and particulate organic matter (POM) obtained by different fractionation schemes have been used for decades and are now considered as classical estimates of very labile and labile soil organic carbon (SOC), respectively. But the pertinence of these methods to characterize SOM turnover can be questioned. Moreover, they are very time-consuming and their reproducibility might be an issue. Alternate ways of determining the labile SOC component are thus well-needed. Thermal analyses have been used to characterize SOM among which Rock-Eval 6 (RE6) analysis of soil has shown promising results in the determination of SOM biogeochemical stability (Gregorich et al., 2015; Barré et al., 2016). Using a large set of samples of French forest soils representing contrasted pedoclimatic conditions, including deep samples (up to 1 m depth), we compared different techniques used for SOM lability assessment. We explored whether results from soil respiration test (10-week laboratory incubations), SOM size-density fractionation and RE6 thermal analysis were comparable and how they were correlated. A set of 222 (respiration test and RE6), 103 (SOM fractionation and RE6) and 93 (respiration test, SOM fractionation and RE6) forest soils samples were respectively analyzed and compared. The comparison of the three methods (n = 93) using a principal component analysis separated samples from the surface (0-10 cm) and deep (40-80 cm) layers, highlighting a clear effect of depth on the short-term persistence of SOC. A correlation analysis demonstrated that, for these samples, the two classical methods of labile SOC determination (respiration and SOM fractionation

[Variations of soil labile organic carbon along an altitude gradient in Wuyi Mountain].

PubMed

Xu, Xia; Chen, Yue-Qin; Wang, Jia-She; Fang, Yan-Hong; Quan, Wei; Ruan, Hong-Hua; Xu, Zi-Kun

2008-03-01

By using sequential fumigation-incubation method, this paper determined the soil labile organic carbon (LOC) content under evergreen broadleaf forest, coniferous forest, sub-alpine dwarf forest, and alpine meadow along an altitude gradient in Wuyi Mountain National Nature Reserve in Fujian Province of China, with its relations to soil microbial biomass carbon (MBC), total organic carbon (TOC), total nitrogen (TN), and fine root biomass (FRB) analyzed. The results showed that soil LOC occupied 3.40%-7.46% of soil TOC, and soil MBC occupied 26.87%-80.38% of the LOC. The LOC under different forest stands increased significantly with altitude, and decreased with soil depth. Soil LOC had very significant correlations with soil MBC, TOC, TN and FRB, and its content was obviously higher at higher altitudes than at lower altitudes.

Seasonal dynamics of particulate organic matter in the Changjiang Estuary and adjacent coastal waters illustrated by amino acid enantiomers

NASA Astrophysics Data System (ADS)

Wu, Ying; Liu, Zongguang; Hu, Jun; Zhu, Zhuoyi; Liu, Sumei; Zhang, Jing

2016-02-01

Total suspended matter (TSM) was collected in the Changjiang Estuary and adjacent areas of the East China Sea in July, August, and November 2011, to study the composition and fate of particulate organic nitrogen (PON) during an August typhoon event and bottom trawling activities. Concentrations of particulate organic carbon (POC), particulate nitrogen (PN), and hydrolyzable particulate amino acids (PAA, D- and L-enantiomers) were higher during July and August than during November; however, D-arginine and alanine levels were significantly higher in November. Seasonal trends in the composition of PAAs indicate that in situ production is a key factor in their temporal distribution. No significant increase in TSM or decrease in labile organic matter was observed during the transit period following a typhoon event in August. In contrast, higher primary production was observed at this time as a result of the penetration of Changjiang Diluted Water caused by the typhoon event. Trawling effects were studied by comparing the calm season (July) with the bottom-trawling period (November) at similar sampling sites. The effect of trawling on the composition of bottom organic matter was studied by comparing D-amino acids concentrations and C/N ratios in the calm season (July) with the bottom-trawling period (November). A substantial contribution of microbial organic matter during the November cruise was indicated by a decrease in glutamic acid, an increase in TSM and D-alanine, and a lower carbon/nitrogen (C/N) ratio. In shallow coastal regions, anthropogenic activities (bottom trawling) may enhance the transfer of low-nutritional-value particulate organic matter into the benthic food chain.

The Influence of Land-Use Change on Soil and Dissolved Organic Matter Age, Lability, and Chemical Characteristics in Brazilian Oxisols

NASA Astrophysics Data System (ADS)

James, J. N.; Harrison, R. B.; Gross, C. D.; Dwivedi, P.; Myers, T.; Butman, D. E.

2017-12-01

Recent advances in freshwater research indicate that the age of carbon exported from major rivers globally increases with greater human disturbance in the watershed. This implies that human land-use can release old, previously mineral-associated C into solution with subsequent export to groundwater and ultimately freshwater systems where terrestrial organic matter is either mineralized to CO2, stored in aquatic sediments, or exported to the ocean. It is important to understand the mechanisms that cause the release of mineral-bound soil organic matter (SOM) into solution in response to human disturbance and land-use change. To better characterize the response of the total soil organic matter (SOM) pool to disturbance, this study examines the interactions between dissolved and bulk soil pools in response to conversion of Brazilian Cerrado (savannah forest) to Eucalyptus plantations. Water-extractable organic matter (WEOM) was obtained from soil samples down to 150 cm at 4 sites in Sao Paulo State, Brazil. These WEOM samples were characterized using fluorescence and NMR spectroscopy, incubated to assess biolability, and carbon-dated. Simultaneously, bulk mineral soil samples were analyzed for microbial biomass, carbon content and age, and characterized using Fourier Transform Infrared Spectroscopy. FTIR spectra of SOM were obtained by washing subsamples with sodium hypochlorite and subtracting the subsequent mineral matrix spectra from bulk soil spectra. Preliminary results show that microbial biomass decreases much more quickly with depth than WEOM, suggesting that C released into solution from deeper horizons may be less likely to be intercepted, and thus preferentially leached to groundwater. Native Cerrado forests had substantially more roots compared to Eucalyptus, and also released substantially larger quantities of WEOM from their O horizons. Furthermore, the age of WEOM released under Eucalyptus forest was more similar in age to bulk SOM, while Cerrado forest

Peat decomposability in managed organic soils in relation to land use, organic matter composition and temperature

NASA Astrophysics Data System (ADS)

Bader, Cédric; Müller, Moritz; Schulin, Rainer; Leifeld, Jens

2018-02-01

Organic soils comprise a large yet fragile carbon (C) store in the global C cycle. Drainage, necessary for agriculture and forestry, triggers rapid decomposition of soil organic matter (SOM), typically increasing in the order forest < grassland < cropland. However, there is also large variation in decomposition due to differences in hydrological conditions, climate and specific management. Here we studied the role of SOM composition on peat decomposability in a variety of differently managed drained organic soils. We collected a total of 560 samples from 21 organic cropland, grassland and forest soils in Switzerland, monitored their CO2 emission rates in lab incubation experiments over 6 months at two temperatures (10 and 20 °C) and related them to various soil characteristics, including bulk density, pH, soil organic carbon (SOC) content and elemental ratios (C / N, H / C and O / C). CO2 release ranged from 6 to 195 mg CO2-C g-1 SOC at 10 °C and from 12 to 423 mg g-1 at 20 °C. This variation occurring under controlled conditions suggests that besides soil water regime, weather and management, SOM composition may be an underestimated factor that determines CO2 fluxes measured in field experiments. However, correlations between the investigated chemical SOM characteristics and CO2 emissions were weak. The latter also did not show a dependence on land-use type, although peat under forest was decomposed the least. High CO2 emissions in some topsoils were probably related to the accrual of labile crop residues. A comparison with published CO2 rates from incubated mineral soils indicated no difference in SOM decomposability between these soil classes, suggesting that accumulation of recent, labile plant materials that presumably account for most of the evolved CO2 is not systematically different between mineral and organic soils. In our data set, temperature sensitivity of decomposition (Q10 on average 2.57 ± 0.05) was the same for all land uses but lowest below 60

In situ application of a cellulose bag and an ion exchanger for differentiation of labile and inert metal species in aquatic systems.

PubMed

Goveia, Danielle; Rosa, André Henrique; Bellin, Iramaia Corrêa; Lobo, Fabiana Aparecida; Fraceto, Leonardo Fernandes; Roveda, José Arnaldo Frutuoso; Romão, Luciane Pimenta Cruz; Dias Filho, Newton Luiz

2008-02-01

This work involved the development and application of a new analytical procedure for in-situ characterization of the lability of metal species in aquatic systems by using a system equipped with a diffusion membrane and cellulose organomodified with p-aminobenzoic acid groups (DM-Cell-PAB). To this end, the DM-Cell-PAB system was prepared by adding cellulose organomodified with p-aminobenzoic acid groups (Cell-PAB) to pre-purified cellulose bags. After the DM-Cell-PAB system was sealed, it was examined in the laboratory. The in-situ application involved immersing the DM-Cell-PAB system in two different rivers, enabling us to study the relative lability of metal species (Cu, Cd, Fe, Mn, and Ni) as a function of time and quantity of exchanger. The procedure is simple and opens up a new perspective for understanding environmental phenomena relating to the complexation, transport, stability, and lability of metal species in aquatic systems rich in organic matter.

Which fraction of soil organic matter is more vulnerable to rhizosphere priming effect?

NASA Astrophysics Data System (ADS)

Zhu, B.; Cheng, W.

2016-12-01

Rhizosphere priming effect (RPE) is defined as the stimulation or suppression of soil organic matter (SOM) decomposition by living roots. It remains unclear which fraction of SOM is more vulnerable to rhizosphere priming. We conducted two experiments in continuous 13CO2 labeling growth chamber to compare the intensity of RPE for the active (or labile) vs. slow (or recalcitrant) SOM. A sandy loam (Alfisol) was incubated at 20oC and 80% water holding capacity for different periods, which created a gradient in the relative proportion of active vs. slow SOM in the remaining soils. We then grew sunflower (Helianthus annuus) and soybean (Glycine max) in these remaining soils for 50 days under the same environmental conditions to compare the RPE of these two plant species on the decomposition of soils that varied in the lability of SOM. In both experiments, as the incubation proceeded from 1 to 8 to 14 months (in experiment 1) and the soil changed from freshly-sampled soil to two-year-incubated soil (in experiment 2), the intensity of RPE increased significantly even after accounting for the changes in root biomass or root-derived CO2. This result suggests that the slow (or recalcitrant) fraction of SOM is likely more vulnerable to rhizosphere priming compared to the active (or labile) fraction of SOM. Although the underlying mechanisms of this finding await further investigation, our study clearly shows that the main component of SOM (slow or recalcitrant SOM, decadal turnover) is vulnerable to rhizosphere priming. Therefore, the RPE has the potential to substantially regulate both short-term and long-term soil carbon dynamics.

A depocenter of organic matter at 7800 m depth in the SE Pacific Ocean

NASA Astrophysics Data System (ADS)

Danovaro, R.; Della Croce, N.; Dell'Anno, A.; Pusceddu, A.

2003-12-01

The Atacama trench, the deepest ecosystem of the southern Pacific Ocean (ca. 8000 m depth) was investigated during the Atacama Trench International Expedition. Sediments, collected at three bathyal stations (1040-1355 m depth) and at a hadal site (7800 m) were analyzed for organic matter quantity and biochemical composition (in terms of phytopigments, proteins, carbohydrates and lipids), bacterial abundance, biomass and carbon production and extracellular enzymatic activities. Functional chlorophyll- a (18.0±0.10 mg m -2), phytodetritus (322.2 mg m -2) and labile organic carbon (16.9±4.3 g C m -2) deposited on surface sediments at hadal depth (7800 m) reached concentrations similar to those encountered in highly productive shallow coastal areas. High values of bacterial C production and aminopeptidase activity were also measured (at in situ temperature and 1 atm). The chemical analyses of the Atacama hadal sediments indicate that this trench behaves as a deep oceanic trap for organic material. We hypothesize that, despite the extreme physical conditions, benthic microbial processes might be accelerated as a result of the organic enrichment.

Effects of crop rotation and management system on water-extractable organic matter concentration, structure, and bioavailability in a chernozemic agricultural soil.

PubMed

Xu, Na; Wilson, Henry F; Saiers, James E; Entz, Martin

2013-01-01

Water-extractable organic matter (WEOM) in soil affects contaminant mobility and toxicity, heterotrophic production, and nutrient cycling in terrestrial and aquatic ecosystems. This study focuses on the influences of land use history and agricultural management practices on the water extractability of organic matter and nutrients from soils. Water-extractable organic matter was extracted from soils under different crop rotations (an annual rotation of wheat-pea/bean-wheat-flax or a perennial-based rotation of wheat-alfalfa-alfalfa-flax) and management systems (organic or conventional) and examined for its concentration, composition, and biodegradability. The results show that crop rotations including perennial legumes increased the concentration of water-extractable organic carbon (WEOC) and water-extractable organic nitrogen (WEON) and the biodegradability of WEOC in soil but depleted the quantity of water-extractable organic phosphorus (WEOP) and water-extractable reactive phosphorus. The 30-d incubation experiments showed that bioavailable WEOC varied from 12.5% in annual systems to 22% for perennial systems. The value of bioavailable WEOC was found to positively correlate with WEON concentrations and to negatively correlate with C:N ratio and the specific ultraviolet absorbance of WEOM. No significant treatment effect was present with the conventional and organic management practices, which suggested that WEOM, as the relatively labile pool in soil organic matter, is more responsive to the change in crop rotation than to mineral fertilizer application. Our results indicated that agricultural landscapes with contrasting crop rotations are likely to differentially affect rates of microbial cycling of organic matter leached to soil waters. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Thermal and spectroscopic analysis of organic matter degradation and humification during composting of pig slurry in different scenarios.

PubMed

Martín-Mata, J; Lahoz-Ramos, C; Bustamante, M A; Marhuenda-Egea, F C; Moral, R; Santos, A; Sáez, J A; Bernal, M P

2016-09-01

In this work, different analytical techniques (thermal analysis, (13)C cross-polarization magic angle spinning (CPMAS) NMR and Fourier transform infrared (FT-IR) spectroscopy) have been used to study the organic matter changes during the co-composting of pig slurry with cotton gin waste. To ensure the validity of the findings, the composting process was developed in different scenarios: under experimental pilot plant conditions, using the static pile system, and under real conditions on a pig farm, using the turning pile system. Also, the thermal stability index (R1) was determined before and after an extraction with water, to evaluate the effect of eliminating water-soluble inorganic salts on the thermal analysis. The results of the thermal methods showed the degradation of the most labile organic matter during composting; R1 increased during composting in all piles, without any influence of the presence of water-soluble inorganic ions in the sample. The NMR showed a decrease in the abundance of the carbohydrate molecules and an increase in the aliphatic materials during composting, due to a concentration effect. Also, FT-IR spectroscopy was a useful technique to study the trends of polysaccharides and nitrate, as indicators of organic matter transformations during composting.

Stabilization of polar soils organic matter: insights from 13-C NMR and ESR spectroscopy

NASA Astrophysics Data System (ADS)

Abakumov, Evgeny

2017-04-01

Polar soils play a key role in the global carbon balance, as they contain maximum stocks of soil organic matter (SOM) within the whole pedosphere. Low temperature and severe conditions provides the accumulation of large amounts of organic matter in permafrost soils over thousands of years. The quality and composition of organic matter of polar soils is underestimated. In order to better understand the implication of permafrost SOM to greenhouse gas emissions, an accurate knowledge of its spatial distribution, both in terms of quantity and quality (i.e. biodegradability, chemical composition and humification degree) is needed. The chemical composition of SOM determines its decomposability and, therefore, it determines the rate at which carbon may be transferred from soils to the atmosphere under warming conditions. Biodegradability of SOM has been related to humification degree, as more advanced stages in the humification process imply a depletion of the labile molecules, as well as an increase in the bulk aromaticity, which provides a higher stability of the SOM. Soils from Antarctic and different sectors of Arctic biome were investigated by 13-C NMR and electron spin resonance spectroscopy. It was shown, that the characteristic feature of polar soils humic acids is the dominance of aliphatic compounds on the aromatic one. This is related to the humification precursors component composition, namely to dominance of the remnants of lower plants, especially in Antarctic and low period of biological activity, which regulates the humification rate. Humic acids of Antarctic and various Arctic soils show the portion of aromatic components not more than 30 %. ESR spectroscopy shown that the concentration of free radicals is proportional to the humic acids stabilization degree. Less humified organic materials show the highest portion of free radical content, while the most developed soils and buried organic layers show decreased contents of free radicals. The database on

Molecular Insights into Arctic Soil Organic Matter Degradation under Warming

DOE PAGES

Chen, Hongmei; Yang, Ziming; Chu, Rosalie K.; ...

2018-03-23

Molecular composition of the Arctic soil organic carbon (SOC) and its susceptibility to microbial degradation are uncertain due to heterogeneity and unknown SOC compositions. By using ultrahigh-resolution mass spectrometry, we determined the susceptibility and compositional changes of extractable dissolved organic matter (EDOM) in an anoxic warming incubation experiment (up to 122 days) with a tundra soil from Alaska (United States). EDOM was extracted with 10 mM NH 4HCO 3 from both the organic- and mineral-layer soils during incubation at both -2 and 8°C. Based on their O:C and H:C ratios, EDOM molecular formulas were qualitatively grouped into nine biochemical classesmore » of compounds, among which lignin-like compounds dominated both the organic and the mineral soils and were the most stable, whereas amino sugars, peptides, and carbohydrate-like compounds were the most biologically labile. These results corresponded with shifts in EDOM elemental composition in which the ratios of O:C and N:C decreased, while the average C content in EDOM, molecular mass, and aromaticity increased after 122 days of incubation. This research demonstrates that certain EDOM components, such as amino sugars, peptides, and carbohydrate-like compounds, are disproportionately more susceptible to microbial degradation than others in the soil, and these results should be considered in SOC degradation models to improve predictions of Arctic climate feedbacks.« less

Molecular Insights into Arctic Soil Organic Matter Degradation under Warming

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

Chen, Hongmei; Yang, Ziming; Chu, Rosalie K.

Molecular composition of the Arctic soil organic carbon (SOC) and its susceptibility to microbial degradation are uncertain due to heterogeneity and unknown SOC compositions. By using ultrahigh-resolution mass spectrometry, we determined the susceptibility and compositional changes of extractable dissolved organic matter (EDOM) in an anoxic warming incubation experiment (up to 122 days) with a tundra soil from Alaska (United States). EDOM was extracted with 10 mM NH 4HCO 3 from both the organic- and mineral-layer soils during incubation at both -2 and 8°C. Based on their O:C and H:C ratios, EDOM molecular formulas were qualitatively grouped into nine biochemical classesmore » of compounds, among which lignin-like compounds dominated both the organic and the mineral soils and were the most stable, whereas amino sugars, peptides, and carbohydrate-like compounds were the most biologically labile. These results corresponded with shifts in EDOM elemental composition in which the ratios of O:C and N:C decreased, while the average C content in EDOM, molecular mass, and aromaticity increased after 122 days of incubation. This research demonstrates that certain EDOM components, such as amino sugars, peptides, and carbohydrate-like compounds, are disproportionately more susceptible to microbial degradation than others in the soil, and these results should be considered in SOC degradation models to improve predictions of Arctic climate feedbacks.« less

Seasonal Variation in the Quality of Dissolved and Particulate Organic Matter Exchanged Between a Salt Marsh and Its Adjacent Estuary

NASA Astrophysics Data System (ADS)

Osburn, C. L.; Mikan, M.; Etheridge, J. R.; Burchell, M. R.; Birgand, F.

2015-12-01

Salt marshes are transitional ecosystems between terrestrial and marine environments. Along with mangroves and other vegetated coastal habitats, salt marshes rank among the most productive ecosystems on Earth, with critical global importance for the planet's carbon cycle. Fluorescence was used to examine the quality of dissolved and particulate organic matter (DOM and POM) exchanging between a tidal creek in a created salt marsh and its adjacent estuary in eastern North Carolina, USA. Samples from the creek were collected hourly over four tidal cycles in May, July, August, and October of 2011. Absorbance and fluorescence of chromophoric DOM (CDOM) and of base-extracted POM (BEPOM) served as the tracers for organic matter quality while dissolved organic carbon (DOC) and base-extracted particulate organic carbon (BEPOC) were used to compute fluxes. Fluorescence was modeled using parallel factor analysis (PARAFAC) and principle components analysis (PCA) of the PARAFAC results. Of nine PARAFAC components modeled, we used multiple linear regression to identify tracers for recalcitrant DOM; labile soil-derived source DOM; detrital POM; and planktonic POM. Based on mass balance, recalcitrant DOC export was 86 g C m-2 yr-1 and labile DOC export was 49 g C m-2 yr-1. The marsh also exported 41 g C m-2 yr-1 of detrital terrestrial POC, which likely originated from lands adjacent to the North River estuary. Planktonic POC export from the marsh was 6 g C m-2 yr-1. Using the DOM and POM quality results obtained via fluorescence measurements and scaling up to global salt marsh area, we estimated that the potential release of CO2 from the respiration of salt marsh DOC and POC transported to estuaries could be 11 Tg C yr-1, roughly 4% of the recently estimated CO2 release for marshes and estuaries globally.

Particulate Organic Matter Composition in Stream Runoff Following Large Storms: Role of POM Sources, Particle Size, and Event Characteristics

NASA Astrophysics Data System (ADS)

Johnson, Erin R.; Inamdar, Shreeram; Kan, Jinjun; Vargas, Rodrigo

2018-02-01

Large storm events possess significant erosive energy capable of mobilizing large amounts of sediment and particulate organic matter (POM) into fluvial systems. This study investigated how stream POM composition varied as a function of the watershed POM source, particle size, storm event magnitude, and seasonal timing. POM composition was characterized for multiple watershed sources and for stream POM following storms in a second-order forested stream. Carbon (C) and nitrogen (N) amount, C:N ratio and isotopic content (13C and 15N) were determined for solid phase POM, whereas dissolved organic C, total N concentrations, and fluorescence characteristics were determined for solution/extracted POM. Key findings from this study were the following: (1) Composition of POM varied greatly with watershed sources with forest floor litter being C and N rich and labile, while stream banks and bed were C and N poor and recalcitrant. (2) Summer storms mobilized more carbon and nitrogen-rich labile sources, while winter events mobilized more carbon- and nitrogen-poor refractory material from near-stream sources. (3) POM composition varied by size class, with the coarse POM showing more C and N rich and labile properties, while the fine POM displayed more degraded and refractory properties. If climate variability increases the magnitude and intensity of large storm events, our observations suggest that this will not only increase the inputs of POM to aquatic systems but also result in the delivery of coarser, C and N rich, and more bioavailable POM to the stream drainage network.

Sulfur species behavior in soil organic matter during decomposition

USGS Publications Warehouse

Schroth, A.W.; Bostick, B.C.; Graham, M.; Kaste, J.M.; Mitchell, M.J.; Friedland, A.J.

2007-01-01

Soil organic matter (SOM) is a primary re??servoir of terrestrial sulfur (S), but its role in the global S cycle remains poorly understood. We examine S speciation by X-ray absorption near-edge structure (XANES) spectroscopy to describe S species behavior during SOM decomposition. Sulfur species in SOM were best represented by organic sulfide, sulfoxide, sulfonate, and sulfate. The highest fraction of S in litter was organic sulfide, but as decomposition progressed, relative fractions of sulfonate and sulfate generally increased. Over 6-month laboratory incubations, organic sulfide was most reactive, suggesting that a fraction of this species was associated with a highly labile pool of SOM. During humification, relative concentrations of sulfoxide consistently decreased, demonstrating the importance of sulfoxide as a reactive S phase in soil. Sulfonate fractional abundance increased during humification irrespective of litter type, illustrating its relative stability in soils. The proportion of S species did not differ systematically by litter type, but organic sulfide became less abundant in conifer SOM during decomposition, while sulfate fractional abundance increased. Conversely, deciduous SOM exhibited lesser or nonexistent shifts in organic sulfide and sulfate fractions during decomposition, possibly suggesting that S reactivity in deciduous litter is coupled to rapid C mineralization and independent of S speciation. All trends were consistent in soils across study sites. We conclude that S reactivity is related to spqciation in SOM, particularly in conifer forests, and S species fractions in SOM change, during decomposition. Our data highlight the importance of intermediate valence species (sulfoxide and sulfonate) in the pedochemical cycling of organic bound S. Copyright 2007 by the American Geophysical Union.

Nitrogen competition between corn and weeds in soils under organic and conventional management

USDA-ARS?s Scientific Manuscript database

Cropping systems research has shown that organic systems can have comparable yields to conventional systems at higher weed biomass levels. Higher weed tolerance in organic systems could be due to differences in labile soil organic matter and nitrogen (N) mineralization potential. The objective of ou...

Do Variations in Detrital Inputs Influence Stable Soil Organic Matter? - An Experimental Approach

NASA Astrophysics Data System (ADS)

Lajtha, K.; Townsend, K.; Brewer, E.; Caldwell, B.; Kalbitz, K.; Plante, A.

2007-12-01

Recognition of the importance of feedbacks from plants in determining soil nutrient dynamics and C storage led to a large number of litter decomposition studies. Despite growing knowledge of short-term litter dynamics, we know relatively little about the fate of plant litter and its role in determining SOM content and nutrient cycling over time scales ranging from decades and centuries. To address this gap, we established long-term studies of controls on soil organic matter formation in an old-growth forest at the H.J. Andrews Experimental Forest, OR. This study complements a network of recently established similar experiments that pan climatic and soil gradients, as well as the original DIRT experiment established in the Wisconsin Arboretum in 1956 in both grassland and forested sites. The central goal of the DIRT project is to assess how rates and sources of plant litter inputs control the accumulation and dynamics of organic matter and nutrients in forest soils over decadal time scales. Treatment plots include doubled litter (needle) inputs , doubled wood, no above ground litter (screened) inputs, no root inputs (trenched), and no inputs (screened and trenched). For the 50th anniversary of the Wisconsin sites and the 10th anniversary of the H.J. Andrews site, we used sequential density fractionation of soils from all treatments to determine if adding or removing either below- or above-ground litter inputs influenced carbon stabilization as soil organic matter. After 50 years, double litter plots in both prairie and forested soils had higher %C in the 0-10 cm horizon. In the forested site, plots showed increased C content of the lightest fraction, which represents relatively young SOM with a short turnover time. However, the first two heavy fractions also showed increases in C with added aboveground litter, suggesting the importance of aboveground litter inputs to SOM in the forest. No such pattern existed for the prairie soil, and we hypothesize that this is

Effects of lability of metal complex on free ion measurement using DMT.

PubMed

Weng, Liping; Van Riemsdijk, Willem H; Temminghoff, Erwin J M

2010-04-01

Very low concentrations of free metal ion in natural samples can be measured using the Donnan membrane technique (DMT) based on ion transport kinetics. In this paper, the possible effects of slow dissociation of metal complexes on the interpretation of kinetic DMT are investigated both theoretically and experimentally. The expressions of the lability parameter, Lgrangian , were derived for DMT. Analysis of new experimental studies using synthetic solution containing NTA as the ligand and Cu(2+) ions shows that when the ionic strength is low (organic matter (DOM) is the most important source of ligands that complex metals. By comparing the fraction of labile species measured using other dynamic sensors (DGT, GIME) in several freshwaters, it is concluded that in most waters ion transport in DMT is controlled by diffusion in the membrane. Only in very soft waters (<0.7 mM Ca+Mg), the dissociation rate of natural metal complex may influence ion transport in DMT. In this case, neglecting this effect may lead to an underestimation of the free metal ion concentration measured.

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.

Distinguishing the influence of soil organic matter quality from that of environmental constraints in controlling soil heterotrophic respiration along a continental network of sites

NASA Astrophysics Data System (ADS)

Pare, D.; Bernier, P. Y.; Trofymow, J. A.; Moore, T. R.

2011-12-01

The forest soils of Canada contain large amounts of carbon and its dynamics is one of the key areas of uncertainty in the carbon balance of North America. While estimates of total soil carbon stocks are available, the relative role of soil organic matter (SOM) quality from that of environmental conditions in maintaining these C reservoirs is poorly known. Soil organic matter (SOM) quality was evaluated with the use of both acid hydrolysis and lab incubation at several temperatures for 15 sites part of the Fluxnet Canada network that represent the major ecological forest groups in Canada and included as well two peatland sites. The mineralizable fraction of soil total C (TOC) varied fivefold across sites and soil layers (4 to 25%). To the opposite acid hydrolysable C was a constant fraction of total organic C (TOC) representing 23 and 37% of TOC in the forest floor and top mineral soil (0-20cm) respectively. Total soil carbon pools were highly correlated with pools of recalcitrant C but weakly to labile pools, especially in the mineral soils. These results indicated that soils accumulating a thick organic layer, such as black spruce and peatland soils, are also accumulating potentially labile C that could be mineralised given favourable environmental conditions. However, this relationship is barely significant for the mineral soils where greater C accumulation indicated in essence more accumulation into recalcitrant pools. Mineralized C was correlated with cellulose concentration in the forest floor (R=0.68) and not with acid-hydrolizable C in either soil horizons suggesting that this fraction in non-relevant to C dynamics. Estimates soil heterotrophic respiration (Rh-lab) using incubation derived equation and field soil hourly temperatures were compared with the size of the soil potentially mineralizable C pool (labile C). The difference between these two figures was large for soil having a large portion of their C reserves in the organic layer but was small for

What is soil organic matter worth?

PubMed

Sparling, G P; Wheeler, D; Vesely, E-T; Schipper, L A

2006-01-01

The conservation and restoration of soil organic matter are often advocated because of the generally beneficial effects on soil attributes for plant growth and crop production. More recently, organic matter has become important as a terrestrial sink and store for C and N. We have attempted to derive a monetary value of soil organic matter for crop production and storage functions in three contrasting New Zealand soil orders (Gley, Melanic, and Granular Soils). Soil chemical and physical characteristics of real-life examples of three pairs of matched soils with low organic matter contents (after long-term continuous cropping for vegetables or maize) or high organic matter content (continuous pasture) were used as input data for a pasture (grass-clover) production model. The differences in pasture dry matter yields (non-irrigated) were calculated for three climate scenarios (wet, dry, and average years) and the yields converted to an equivalent weight and financial value of milk solids. We also estimated the hypothetical value of the C and N sequestered during the recovery phase of the low organic matter content soils assuming trading with C and N credits. For all three soil orders, and for the three climate scenarios, pasture dry matter yields were decreased in the soils with lower organic matter contents. The extra organic matter in the high C soils was estimated to be worth NZ$27 to NZ$150 ha(-1) yr(-1) in terms of increased milk solids production. The decreased yields from the previously cropped soils were predicted to persist for 36 to 125 yr, but with declining effect as organic matter gradually recovered, giving an accumulated loss in pastoral production worth around NZ$518 to NZ$1239 ha(-1). This was 42 to 73 times lower than the hypothetical value of the organic matter as a sequestering agent for C and N, which varied between NZ$22,963 to NZ$90,849 depending on the soil, region, discount rates, and values used for carbon and nitrogen credits.

Assessment of the labile fractions of copper and zinc in marinas and port areas in Southern Brazil.

PubMed

Costa, Luiza Dy Fonseca; Wallner-Kersanach, Mônica

2013-08-01

The dissolved labile and labile particulate fractions (LPF) of Cu and Zn were analyzed during different seasons and salinity conditions in estuarine waters of marina, port, and shipyard areas in the southern region of the Patos Lagoon (RS, Brazil). The dissolved labile concentration was determined using the diffusive gradients in thin films technique (DGT). DGT devices were deployed in seven locations of the estuary for 72 h and the physicochemical parameters were also measured. The LPF of Cu and Zn was determined by daily filtering of water samples. Seasonal variation of DGT-Cu concentrations was only significant (p < 0.05) at one shipyard area, while DGT-Zn was significant (p < 0.05) in every locations. The LPF of Cu and Zn concentrations demonstrated seasonal and spatial variability in all locations, mainly at shipyard areas during high salinity conditions. In general, except the control location, the sampling locations showed mean variations of 0.11-0.45 μg L(-1) for DGT-Cu, 0.89-9.96 μg L(-1) for DGT-Zn, 0.65-3.69 μg g(-1) for LPF-Cu, and 1.35-10.87 μg g(-1) for LPF-Zn. Shipyard areas demonstrated the most expressive values of labile Cu and Zn in both fractions. Strong relationship between DGT-Zn and LPF-Zn was found suggesting that the DGT-Zn fraction originates from the suspended particulate matter. Water salinity and suspended particulate matter content indicated their importance for the control of the labile concentrations of Cu and Zn in the water column. These parameters must be taken into consideration for comparison among labile metals in estuaries.

Mood lability and psychopathology in youth.

PubMed

Stringaris, A; Goodman, R

2009-08-01

Mood lability is a concept widely used. However, data on its prevalence and morbid associations are scarce. We sought to establish the occurrence and importance of mood lability in a large community sample of children and adolescents by testing a priori hypotheses. Cross-sectional data were taken from a national mental health survey including 5326 subjects aged 8-19 years in the UK. The outcomes were prevalence and characteristics of mood lability and its associations with psychopathology and overall impairment. Mood lability occurred in more than 5% of the population of children and adolescents, both by parent and self-report. Mood lability was strongly associated with a wide range of psychopathology and was linked to significant impairment even in the absence of psychiatric disorders. Mood lability was particularly strongly associated with co-morbidity between internalizing and externalizing disorders, even when adjusting for the association with individual disorders. The pattern of results did not change after excluding youth with bipolar disorder or with episodes of elated mood. Clinically significant mood lability is relatively common in the community. Our findings indicate that mood lability is not a mere consequence of other psychopathology in that it is associated with significant impairment even in the absence of psychiatric diagnoses. Moreover, the pattern of association of mood lability with co-morbidity suggests that it could be a risk factor shared by both internalizing and externalizing disorders. Our data point to the need for greater awareness of mood lability and its implications for treatment.

Metabolic and structural response of hyporheic microbial communities to variations in supply of dissolved organic matter

USGS Publications Warehouse

Findlay, S.E.G.; Sinsabaugh, R. L.; Sobczak, W.V.; Hoostal, M.

2003-01-01

Hyporheic sediment bacterial communities were exposed to dissolved organic matter (DOM) from a variety of sources to assess the interdependence of bacterial metabolism and community composition. Experiments ranged from small-scale core perfusions with defined compounds (glucose, bovine serum albumin) to mesocosms receiving natural leaf leachate or water from different streams. Response variables included bacterial production, oxygen consumption, extracellular enzyme activity, and community similarity as manifest by changes in banding patterns of randomly amplified polymorphic DNA (RAPD). All DOM manipulations generated responses in at least one metabolic variable. Additions of both labile and recalcitrant materials increased either oxygen consumption, production, or both depending on background DOM. Enzyme activities were affected by both types of carbon addition with largest effects from the labile mixture. Cluster analysis of RAPD data showed strong divergence of communities exposed to labile versus recalcitrant DOM. Additions of leaf leachate to mesocosms representing hyporheic flow-paths caused increases in oxygen consumption and some enzyme activities with weaker effects on production. Community structure yeas strongly affected; samples from the leachate-amended mesocosms clustered separately from the control samples. In mesocosms receiving water from streams ranging in DOC (0.5-4.5 mg L-1), there were significant differences in bacterial growth, oxygen consumption, and enzyme activities. RAPD analysis showed strongest clustering of samples by stream type with more subtle effects of position along the flowpaths. Responses in community metabolism were always accompanied by shifts in community composition, suggesting carbon supply affects both functional and structural attributes of hyporheic bacterial communities.

Microphytobenthos and benthic macroalgae determine sediment organic matter composition in shallow photic sediments

NASA Astrophysics Data System (ADS)

Hardison, A. K.; Canuel, E. A.; Anderson, I. C.; Tobias, C. R.; Veuger, B.; Waters, M.

2013-02-01

Benthic macroalgae are a common symptom of eutrophication in shallow coastal bays as a result of increased nutrient loads. Microphytobenthos (MPB) and benthic macroalgae play an important role in system metabolism within shallow coastal bays. However, their independent and interactive influences on sediment organic matter (SOM) are not well understood. We investigated the influence of macroalgae and MPB on SOM quantity and quality in an experimental mesocosm system using bulk and molecular level (total hydrolyzable amino acids, THAA; phospholipid linked fatty acids, PLFA; pigment) analyses. Our experiment used an incomplete factorial design made up of two factors, each with two levels: (1) light (ambient vs. dark) and (2) macroalgae (presence vs. absence of live macroalgae). Over the course of the 42-day experiment, total organic carbon (TOC) and total nitrogen (TN) increased under ambient light by 173 ± 14 and 141 ± 7%, respectively, compared to in the dark (78 ± 29 and 39 ± 22%). THAA comprised a substantial fraction of SOM (∼16% of TOC, 35% of TN) and followed TOC and TN accumulation patterns. Mole percent composition of the THAA pool indicated that SOM was composed of more labile organic material (e.g. L-glutamic acid, phenylalanine) under ambient light conditions while SOM in dark treatments was more degraded, with higher proportions of glycine and D-alanine. PLFA content, which represents viable biomass, made up ∼1% of TOC and contained high levels of algal fatty acids in the light, particularly PLFA derived from diatoms. In the presence of MPB (i.e. light and macroalgae treatments), SOM lability increased, resulting in the observed increases in bacterial PLFA concentrations. Macroalgae, which were added to half of the light treatments, decreased SOM accumulation compared to light treatments without macroalgae, with TOC and TN increasing by only 130 ± 32 and 94 ± 24 %, respectively. This decrease likely resulted from shading by macroalgae, which

Microphytobenthos and benthic macroalgae determine sediment organic matter composition in shallow photic sediments

NASA Astrophysics Data System (ADS)

Hardison, A. K.; Canuel, E. A.; Anderson, I. C.; Tobias, C. R.; Veuger, B.; Waters, M. N.

2013-08-01

Microphytobenthos and benthic macroalgae play an important role in system metabolism within shallow coastal bays. However, their independent and interactive influences on sediment organic matter (SOM) are not well understood. We investigated the influence of macroalgae and microphytobenthos on SOM quantity and quality in an experimental mesocosm system using bulk and molecular level (total hydrolyzable amino acids, THAA; phospholipid linked fatty acids, PLFA; pigment) analyses. Our experiment used an incomplete factorial design made up of two factors, each with two levels: (1) light (ambient vs. dark) and (2) macroalgae (presence vs. absence of live macroalgae). Over the course of the 42-day experiment, total organic carbon (TOC) and total nitrogen (TN) increased under ambient light by 173 ± 14 and 141 ± 7%, respectively, compared to in the dark (78 ± 29 and 39 ± 22%). THAA comprised a substantial fraction of SOM (~ 16% of TOC, 35% of TN) and followed TOC and TN accumulation patterns. Mole percent composition of the THAA pool indicated that SOM was composed of more labile organic material (e.g., L-glutamic acid, phenylalanine) under ambient light conditions while SOM in dark treatments was more degraded, with higher proportions of glycine and D-alanine. PLFA content, which represents viable biomass, made up ~ 1% of TOC and contained high levels of algal fatty acids in the light, particularly PLFA derived from diatoms. In the presence of microphytobenthos (i.e., light and macroalgae treatments), SOM lability increased, resulting in the observed increases in bacterial PLFA concentrations. Macroalgae, which were added to half of the light treatments, decreased SOM accumulation compared to light treatments without macroalgae, with TOC and TN increasing by only 130 ± 32 and 94 ± 24%, respectively. This decrease likely resulted from shading by macroalgae, which reduced production of microphytobenthos. The presence of macroalgae decreased SOM lability as well, which

Sources and reactivities of marine-derived organic matter in coastal sediments as determined by alkaline CuO oxidation

NASA Astrophysics Data System (ADS)

Goñi, Miguel A.; Hedges, John I.

1995-07-01

Alkaline CuO oxidation of ubiquitous biochemicals such as proteins, polysaccharides, and lipids, yields specific products, including fatty acids, diacids, and carboxylated phenols. Oxidation of a variety of marine organisms, including macrophytes, phytoplankton, zooplankton, and bacteria, yields these CuO products in characteristic patterns that can often differentiate these biological sources. Sediments from Skan Bay (Unalaska Island, Alaska) display organic carbon and total nitrogen profiles which are consistent with three kinetically distinct pools of organic matter. The CuO fingerprints of these sediments distinguish these three pools at the molecular level, indicating a highly labile, fatty acid-rich surface organic layer of likely bacterial origin, intermediately reactive kelp debris and a background of phytoplankton remains that predominates at depth. The CuO method, which has been previously applied only to characterize cutin and lignin constituents of vascular land plants, also provides information on other types of abundant biochemicals, including those indicative of marine sources.

Are lake sediments mere archives of degraded organic matter? - evidence of rapid biotic changes tracked in sediments of pre-alpine Lake Lunz, Austria

NASA Astrophysics Data System (ADS)

Hollaus, Lisa-Maria; Khan, Samiullah; Schelker, Jakob; Ejarque, Elisabet; Battin, Tom; Kainz, Martin

2016-04-01

Lake sediments are used as sentinels of changes in organic matter composition and dynamics within lakes and their catchments. In an effort to investigate how past and recent hydrological extreme events have affected organic matter composition in lake sediments, we investigated the biogeochemical composition of sediment cores and settling particles, using sediment traps in the pre-alpine, oligotrophic Lake Lunz, Austria. We assessed annual sedimentation rates using 137Cs and 210Pb, time integrated loads of settling particles, analyze stable carbon (δ13C) and nitrogen (δ15N) isotopes to track changes of carbon sources and trophic compositions, respectively, and use source-specific fatty acids as indicators of allochthonous, bacterial, and algal-derived organic matter. Preliminary results indicate that settling particles of Lake Lunz (33 m depth) contain high algae-derived organic matter, as assessed by long-chain polyunsaturated fatty acids (LC-PUFA), indicating low degradation of such labile organic matter within the water column of this lake. However, LC-PUFA decreased rapidly in sediment cores below the sediment-water interface. Concentrations of phosphorous remained stable throughout the sediment cores (40 cm), suggesting that past changes in climatic forcing did not alter the load of this limiting nutrient in lakes. Ongoing work reveals dramatic biotic changes within the top layers of the sediment cores as evidenced by high numbers of small-bodied cladocerans (e.g., Bosmina) and large-bodied zooplankton (e.g., Daphnia) are only detected at lower sediment layers. Current research on these lake sediments is aimed at investigating how organic matter sources changed during the past century as a result of recorded weather changes.

Organic matter in central California radiation fogs.

PubMed

Herckes, Pierre; Lee, Taehyoung; Trenary, Laurie; Kang, Gongunn; Chang, Hui; Collett, Jeffrey L

2002-11-15

Organic matter was studied in radiation fogs in the San Joaquin Valley of California during the California Regional Particulate Air Quality Study (CRPAQS). Total organic carbon (TOC) concentrations ranged from 2 to 40 ppm of C. While most organic carbon was found in solution as dissolved organic carbon (DOC), 23% on average was not dissolved inside the fog drops. We observe a clear variation of organic matter concentration with droplet size. TOC concentrations in small fog drops (<17 microm) were a factor of 3, on average, higher than TOC concentrations in larger drops. As much as half of the dissolved organic matter was determined to have a molecular weight higher than 500 Da. Deposition fluxes of organic matter in fog drops were high (0.5-4.3 microg of C m(-2) min(-1)), indicating the importance of fog processing as a vector for removal of organic matter from the atmosphere. Deposition velocities of organic matter, however, were usually found to be lower than deposition velocities for fogwater, consistent with the enrichment of the organic matter in smaller fog drops with lower terminal settling velocities.

The role of tree species and soil moisture in soil organic matter stabilization and destabilization

NASA Astrophysics Data System (ADS)

Hatten, J. A.; Dewey, J.; Roberts, S.; McNeal, K.; Shaman, A.

2014-12-01

Inputs of labile organic substrates to soils are commonly associated with elevated soil organic carbon mineralization rates; this process is known as the priming effect. Plant presence and soil conditions (i.e. water regime, nutrient status) are known to be interacting factors governing priming. In this study, we examine the role of differing species, loblolly pine (Pinus taeda L.) and nuttall oak (Quercus texana B.), and moisture regimes (low and high) upon the soil priming effect in a fine textured soil. We explore whether there is depletion of original soil carbon and concurrent replacement through addition of fresh organic matter from the planted tree species. By employing a series of planted and plant-free pots in a greenhouse mesocosm study, we were able to characterize the composition of soil organic matter and its carbon with the use of CuO oxidation products (e.g. lignin, cutin/suberin biomarkers). Carbon was elevated on the low moisture samples relative to all other treatments, and the C:N ratio suggests that newly produced plant carbon replaced original soil carbon. The soil lignin content of the planted treatments was lower than the plant-free treatments suggesting that lignin present in the original soil may have been preferentially degraded by priming and not replaced. We will discuss the utility of CuO oxidation products to explore soil organic carbon dynamics and the implications of understanding the role of species and soil moisture in predicting the response of soil carbon to land use and climate change.

Non-conservative behavior of fluorescent dissolved organic matter (FDOM) within a subterranean estuary

NASA Astrophysics Data System (ADS)

Suryaputra, I. G. N. A.; Santos, I. R.; Huettel, M.; Burnett, W. C.; Dittmar, T.

2015-11-01

The role of submarine groundwater discharge (SGD) in releasing fluorescent dissolved organic matter (FDOM) to the coastal ocean and the possibility of using FDOM as a proxy for dissolved organic carbon (DOC) was investigated in a subterranean estuary in the northeastern Gulf of Mexico (Turkey Point, Florida). FDOM was continuously monitored for three weeks in shallow beach groundwater and in the adjacent coastal ocean. Radon (222Rn) was used as a natural groundwater tracer. FDOM and DOC correlated in groundwater and seawater samples, implying that FDOM may be a proxy of DOC in waters influenced by SGD. A mixing model using salinity as a seawater tracer revealed FDOM production in the high salinity region of the subterranean estuary. This production was probably a result of infiltration and transformation of labile marine organic matter in the beach sediments. The non-conservative FDOM behavior in this subterranean estuary differs from most surface estuaries where FDOM typically behaves conservatively. At the study site, fresh and saline SGD delivered about 1800 mg d-1 of FDOM (quinine equivalents) to the coastal ocean per meter of shoreline. About 11% of this input was related to fresh SGD, while 89% were related to saline SGD resulting from FDOM production within the shallow aquifer. If these fluxes are representative of the Florida Gulf Coast, SGD-derived FDOM fluxes would be equivalent to at least 18% of the potential regional riverine FDOM inputs. To reduce uncertainties related to the scarcity of FDOM data, further investigations of river and groundwater FDOM inputs in Florida and elsewhere are necessary.

The effect of flood events on the partitioning of labile and refractory carbon in the Missouri-Mississippi River system

NASA Astrophysics Data System (ADS)

Roe, K. M.; Rosenheim, B. E.; Kolker, A.; Allison, M. A.; Nittrouer, J. A.; Duncan, D. D.; Nyman, J. A.; Butcher, K. A.; Adamic, J. F.

2009-12-01

The Missouri-Mississippi River system (MMRS) transports over 40% (4.0 x 109 kg) of the United States's annual input of total organic carbon (OC) from land to the marine environment, yet it is challenging to assess the MMRS’s exact role in the global carbon cycle because of the system’s complexity and temporal variability (i.e. high discharge events and low flow regimes). Determining the relative proportion of labile OC to refractory OC entrained in the MMRS during high and mean flow conditions would lend to the understanding of the MMRS’s role in the flux of carbon between the biospheric and atmospheric reservoirs, which is central to determining the role of anthropogenic CO2 in the global carbon cycle and in climate change. In this study, we investigate the relative proportion of labile OC to refractory OC in the lower MMRS during high and near-mean flow conditions in the springs of 2008 and 2009, respectively. The 2008 spring flood discharged 105 km3 of water, the maximum amount of water ever allowed out of the main channel, at a maximum rate of 4.3 x 104 m3s-1. Events of this scale have occurred only nine times in the past 80 years. Additionally, during the spring 2008 flood, bedload sand and large particulate OC transport rates were observed to increase exponentially. The following spring, high discharge rates returned to near-mean values with a peak discharge of 3.6 x 103 m3s-1. Using radiocarbon age and the thermal stability of organic matter (OM) as a proxy for lability, we evaluate the spectra of ages of particulate OM transported in the lower MMRS during these two flow regimes using a programmed-temperature pyrolysis/combustion system (PTP/CS) coupled with 14C determination. The PTP/CS utilizes the differences in thermal stability of acid insoluble particulate organic matter (AIPOM) to separate different components from the bulk. Employing PTP/CS on bulk AIPOM can complement experiments measuring small proportions of total OM such as compound

Fluorescence spectroscopy reveals accompanying occurrence of ammonium with fulvic acid-like organic matter in a fluvio-lacustrine aquifer of Jianhan Plain.

PubMed

Huang, Shuangbing; Wang, Yanxin; Ma, Teng; Wang, Yanyan; Zhao, Long

2016-05-01

This study is the first to investigate the simultaneous presence of NH4 (+) and fluorescent organic matter components (FOCs) from a fluvio-lacustrine aquifer in Central Jianghan Plain. Sediment, groundwater, and surface water samples were collected for the sediment organic matter extraction, 3D fluorescence spectroscopy characterization, and/or hydrochemical analysis. NH4 (+) and dissolved organic carbon was ubiquitous in the groundwater. The fluorescence spectroscopy revealed good relationships between NH4 (+) and fulvic acid-like components (FALCs) in the groundwater and sediment-extracted organic matter (SEOM) solutions. NH4 (+) also exhibited significant positive correlation with protein-like component (PLC) (p < 0.001), with the stronger in the SEOM solutions than that in groundwater. Comparisons of spectroscopic indices [e.g., humification index (HIX), biological index (BIX), spectra slope (S275-295), and specific UV absorbance (SUVA254)] between the groundwater and SEOM solutions revealed more labile properties of SEOM. This result indicates that the decreasing NH4 (+)-FOCs correlations of groundwater relative to sediments may be attributed to microbial degradation. Factor analysis identifies important factors that cause NH4 (+) occurrence in the groundwater. The accompanying increase of FALC (C1) and NH4-N with the mole concentration of the normalized HCO3 (-)/(Ca(2+)+Mg(2+)) and [H(+)] suggests that couple effects of various biodegradations simultaneously occur in the aquifer, promoting the occurrence of NH4-DOMs.

Relationships between soil organic matter pools and nitrous oxide emissions of agroecosystems in the Brazilian Cerrado.

PubMed

de Figueiredo, Cícero Célio; de Oliveira, Alexsandra Duarte; Dos Santos, Isis Lima; Ferreira, Eloisa Aparecida Belleza; Malaquias, Juaci Vitoria; de Sá, Marcos Aurélio Carolino; de Carvalho, Arminda Moreira; Dos Santos, João de Deus Gomes

2018-03-15

In the Brazilian Cerrado, despite the increasing adoption of no-till systems, there are still extended areas under conventional soil management systems that reduce soil carbon (C) and nitrogen (N) stocks and increase the emissions of greenhouse gases, such as nitrous oxide (N 2 O). Conservation agroecosystems, such as no-till, have been proposed as a strategy to mitigate agriculture-induced climatic changes through reductions in N 2 O emissions. However, the relationship between organic matter and N 2 O emissions from soils under different agroecosystems is not yet clear. This study hypothesized that agroecosystems under no-till promote an accumulation of labile and stable SOM fractions along with a reduction of N 2 O emissions. This study evaluated the effects of crop-rotation agroecosystems: i) on C and N pools and labile and stable SOM fractions; ii) on cumulative N 2 O emissions; and iii) on the relationships between SOM fractions and N 2 O emissions. The agricultural systems consisted of: (I) soybean followed by sorghum under no-tillage (NT1); (II) maize followed by pigeon pea under no-tillage (NT2); (III) soybean under conventional tillage followed by fallow soil (CT); (IV) and native Cerrado (CER). After CT for 18years, following the replacement of CER, the soil C stock in the 0-20cm layer was reduced by 0.64tha -1 year -1 . The no-till systems were more efficient in accumulating labile and stable C fractions with values close to those observed under CER, and were directly related to lower soil N 2 O emissions. The cumulative pattern of N 2 O emissions was inverse to that of the following SOM fractions: microbial biomass carbon, permanganate-oxidizable carbon, particulate organic carbon, inert carbon, and humic substances. Based on principal component analysis, the CT was generally separated from the other land use systems. This separation was strongly influenced by the low C contents in the different SOM fractions and higher N 2 O emissions promoted by the

Characterizing Dissolved Organic Matter (DOM) Isolated From Specific Allochthonous and Autochthonous Sources in a North-Temperate Stream Ecosystem

NASA Astrophysics Data System (ADS)

Wong, J. C.; Williams, D.

2009-05-01

Detrital energy in temperate headwater streams is mainly derived from the annual input of leaf litter from the surrounding landscape. Presumably, its decomposition and other sources of autochthonous organic matter will change dissolved organic carbon (DOC) concentrations and dissolved organic matter (DOM) quality. To investigate this, DOM was leached from two allochthonous sources: white birch (Betula papyrifera) and white cedar (Thuja occidentalis); and one autochthonous source, streambed biofilm, for a period of 7 days on 3 separate occasions in fall 2007. As a second treatment, microorganisms from the water column were filtered out. Deciduous leaf litter was responsible for high, short-term increases to DOC concentrations whereas the amounts leached from conifer needles were relatively constant in each month. Using UV spectroscopy, changes to DOM characteristics like aromaticity, spectral slopes, and molecular weight were mainly determined by source and indicated a preferential use of the labile DOM pool by the microorganisms. Excitation-emission matrices (EEMs) collected using fluorescence spectroscopy suggested that cedar litter was an important source of protein-like fluorescence and that the nature of the fluorescing DOM components changed in the presence of microorganisms. This study demonstrates that simultaneous examination of DOC concentrations and DOM quality will allow a better understanding of the carbon dynamics that connect terrestrial with aquatic ecosystems.

Accelerated removal of pyrene and benzo[a]pyrene in freshwater sediments with amendment of cyanobacteria-derived organic matter.

PubMed

Yan, Zaisheng; Jiang, Helong; Li, Xiaohong; Shi, Yuan

2014-05-15

The removal of pyrene and benzo[a]pyrene (BaP) were investigated in freshwater sediments with amendment of seven different organic matters including cyanobacteria-derived organic matter (COM), plant-derived organic matter (POM), and humic substances (HS). During the 210 days of experiments, the amendment of COM or HS enhanced significantly the removal of pyrene and BaP in sediments, especially with fresh COM (FCOM) treatment much superior to HS. On the contrary, degradation of these polycyclic aromatic hydrocarbons (PAHs) was not significantly improved and even inhibited in POM-amended sediments. The first-order rate constants of pyrene and BaP degradation in the FCOM-amended sediments reached 0.00540±0.00017d(-1) and 0.00517±0.00057d(-1), respectively, and were about three and five folds of those in the control treatment. The enhanced PAHs degradation in FCOM-amended sediments was related to higher PAH-degrading bacteria number and bioavailability with a result of biostimulation and priming effect by labile carbon and high-value nutrition in FCOM. Thus, this study improved our understanding about effects of settled biomass from cyanobacterial blooms, which occurred frequently in eutrophic aquatic ecosystems, on the natural attenuation of PAHs in sediments. Furthermore, this study would also help develop a new promising approach to remediate PAH-contaminated sediments through utilization of cyanobacterial bloom biomass. Copyright © 2014 Elsevier B.V. All rights reserved.

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.

Particulate organic matter fluxes and hydrodynamics at the Tisler cold-water coral reef

NASA Astrophysics Data System (ADS)

Wagner, Hannes; Purser, Autun; Thomsen, Laurenz; Jesus, Carlos César; Lundälv, Tomas

2011-03-01

Cold-water coral reefs occur in many regions of the world's oceans. Fundamental questions regarding their functioning remain unanswered. These include the biogeochemical influence of reefs on their environment ("reef effects") and the influence of hydrodynamic processes on reef nutrition. In a succession of field campaigns in 2007 and 2008, these questions were addressed at the Tisler cold-water coral reef, which is centered on a sill peak in the Norwegian Skagerrak. A variety of methodological approaches were used. These consisted of the collection of CTD and chlorophyll profiles, current measurements, sampling of particulate organic matter (POM) in the benthic boundary layer (BBL) across the reef with subsequent chemical analyses, and the chemical analysis of freshly released Lophelia pertusa mucus. CTD and chlorophyll profiles indicated that downstream of the sill crest, downwelling delivered warmer, fresher and chlorophyll richer water masses down to the BBL. Both sides of the reef received downwelling nutrition delivery, as flow direction over the reef reversed periodically. Several chemical composition indicators revealed that suspended POM was significantly fresher on the downstream side of the reef than on the upstream side. L. pertusa mucus from the Tisler Reef was labile in composition, as indicated by a low C/N ratio and a high amino acid degradation index (DI) value. Particulate organic carbon (POC) content in the BBL was significantly depleted across the reef. Lateral depositional fluxes were calculated to be 18-1485 mg POC m -2 d -1, with a mean of 459 mg POC m -2 d -1. We propose that the combination of fresh, downwelling POM with mucus released from the reef was the cause of the greater lability of the downstream POM. Our data on POC depletion across the reef suggest that cold-water coral reefs could play an important role in carbon cycling along continental margins.

Bacteria and fluorescent organic matter: processing and production.

NASA Astrophysics Data System (ADS)

Fox, B. G.; Thorn, R. M. S.; Reynolds, D. M.

2017-12-01

There is a need for a greater understanding of the importance of aquatic organic matter (OM) within global biogeochemical cycling. This need has prompted characterisation of OM using fluorescence spectroscopy. The origin, transformation and fate of fluorescent organic matter (FOM) is not fully understood within freshwater systems. This work demonstrates the importance of microbial processing in the creation and transformation of FOM, highlighting the dynamics of microbial-FOM interactions, using a model system. The FOM signature of different bacterial species common to surface freshwaters were analysed using a non-fluorescent media; Escherichia coli, Bacillus subtilis and Pseudomonas aeruginosa. By undertaking bacterial growth curves, alongside fluorescence spectroscopy, we have been able to determine FOM development in relation to population growth. Within this, we have identified that FOM peaks are associated with different species and driven by bacterial processes, such as cell multiplication or as metabolic by-products. The intracellular and extracellular fluorescence signature of each species has also been analysed to better understand how the microbial community structure may impact the FOM signal in aquatic systems. For example, Peak T develops within the growth curves of all the cultured species and has been identified as both intracellular and extracellular FOM. Whilst Peak T has been termed `microbially-derived' previously, other fluorescence peaks associated with terrestrial high molecular weight compounds, e.g. Peak C, have also been shown to be produced by bacteria throughout growth stages. Additionally, the notion that cell lysis is responsible for the presence of larger FOM compounds was also explored. Our work highlights the capacity of bacteria to not only utilise and process OM but to actively be a source of both labile and recalcitrant OM in situ. The bacteria fluorescence signatures seen are complex with comparable fluorescence peaks to those

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.

Soft X-Ray Photoionizing Organic Matter from Comet Wild 2: Evidence for the Production of Organic Matter by Impact Processes

NASA Technical Reports Server (NTRS)

Zolensky, Michael E.; Wirick, S.; Flynn, G. J.; Jacobsen, C.; Na

2011-01-01

The Stardust mission collected both mineral and organic matter from Comet Wild 2 [1,2,3,4]. The organic matter discovered in Comet Wild 2 ranges from aromatic hydrocarbons to simple aliphatic chains and is as diverse and complex as organic matter found in carbonaceous chondrites and interplanetary dust particles.[3,5,6,7,8,9]. Compared to insoluble organic matter from carbonaceous chondrites the organic matter in Comet Wild 2 more closely resembles organic matter found in the IDPS both hydrous and anhydrous. Common processes for the formation of organic matter in space include: Fischer-Tropsch, included with this aqueous large body and moderate heating alterations; UV irradiation of ices; and; plasma formation and collisions. The Fischer-Tropsch could only occur on large bodies processes, and the production of organic matter by UV radiation is limited by the penetration depth of UV photons, on the order of a few microns or less for most organic matter, so once organic matter coats the ices it is formed from, the organic production process would stop. Also, the organic matter formed by UV irradiation would, by the nature of the process, be in-sensitive to photodissocation from UV light. The energy of soft X-rays, 280-300 eV occur within the range of extreme ultraviolet photons. During the preliminary examination period we found a particle that nearly completely photoionized when exposed to photons in the energy range 280-310eV. This particle experienced a long exposure time to the soft x-ray beam which caused almost complete mass loss so little chemical information was obtain. During the analysis of our second allocation we have discovered another particle that photoionized at these energies but the exposure time was limited and more chemical information was obtained.

Reduction in the exchange of coastal dissolved organic matter and microgels by inputs of extra riverine organic matter.

PubMed

Shiu, Ruei-Feng; Lee, Chon-Lin; Chin, Wei-Chun

2017-12-15

Rivers drive large amounts of terrestrial and riverine organic matter into oceans. These organic materials may alter the self-assembly of marine dissolved organic matter (DOM) polymers into microgels and can even affect the behavior of existing natural microgels. We used Suwannee River humic acid, fulvic acid, and natural organic matter as a model of riverine organic matter (ROM) to investigate the impacts of ROM input on DOM polymer and microgel conversion. Our results indicated that the release of extra ROM, even at low concentrations (0.1-10 mg L -1 ), into the marine organic matter pool decreased the size of self-assembled DOM polymers (from 4-5 μm to < 1 μm) and dispersed the existing natural microgels into smaller particles (from 4-5 μm to 2-3 μm). The particle size of the microgel phase was also less sensitive than that of the DOM polymers to external changes (addition of ROM). This size reduction in DOM aggregation and existing microgels may be closely tied to the surface chemistry of the organic matter, such as negative surface charge stabilization and Ca 2+ cross-linking bridges. These findings reveal that ROM inputs may therefore impede the self-assembly of DOM polymers into particulate organic matter and reduce the sedimentation flux of organic carbon and other elements from surface water to the deep ocean, thereby disturbing the biological pump, the downward transportation of nutrients, and the marine organic carbon cycle. Copyright © 2017 Elsevier Ltd. All rights reserved.

The contentious nature of soil organic matter.

PubMed

Lehmann, Johannes; Kleber, Markus

2015-12-03

The exchange of nutrients, energy and carbon between soil organic matter, the soil environment, aquatic systems and the atmosphere is important for agricultural productivity, water quality and climate. Long-standing theory suggests that soil organic matter is composed of inherently stable and chemically unique compounds. Here we argue that the available evidence does not support the formation of large-molecular-size and persistent 'humic substances' in soils. Instead, soil organic matter is a continuum of progressively decomposing organic compounds. We discuss implications of this view of the nature of soil organic matter for aquatic health, soil carbon-climate interactions and land management.

Coupled cycling of dissolved organic nitrogen and carbon in a forest stream

Treesearch

E.N. Jack Brookshire; H. Maurice Valett; Steven A. Thomas; Jackson R. Webster

2005-01-01

Dissolved organic nitrogen (DON) is an abundant but poorly understood pool of N in many ecosystems. We assessed DON cycling in a N-limited headwater forest stream via whole-ecosystem additions of dissolved inorganic nitrogen (DIN) and labile dissolved organic matter (DOM), hydrologic transport and biogeochemical modeling, and laboratory experiments with native...

Impact of pyrogenic organic matter decomposition and induced priming effect on soil C budget.

NASA Astrophysics Data System (ADS)

Maestrini, Bernardo; Abiven, Samuel

2014-05-01

decomposition: positive on the short term and negative on the long term. The meta-analysis showed that that positive priming effect is induced mostly on the native soil organic matter on the short term and by PyOM characterised by a low C content. This result was not confirmed on the freshly added organic matter. We believe that the presence of a labile fraction in PyOM may induce positive priming effect on the short term by mean of co-metabolism. We conclude that PyOM chemical composition and feedstock play an important role in predicting PyOM mineralization rate, and that on the short term PyOM may induce a positive priming effect therefore decreasing the abatement potential of PyOM as a C-sink.

Integrating plant litter quality, soil organic matter stabilization, and the carbon saturation concept.

PubMed

Castellano, Michael J; Mueller, Kevin E; Olk, Daniel C; Sawyer, John E; Six, Johan

2015-09-01

Labile, 'high-quality', plant litters are hypothesized to promote soil organic matter (SOM) stabilization in mineral soil fractions that are physicochemically protected from rapid mineralization. However, the effect of litter quality on SOM stabilization is inconsistent. High-quality litters, characterized by high N concentrations, low C/N ratios, and low phenol/lignin concentrations, are not consistently stabilized in SOM with greater efficiency than 'low-quality' litters characterized by low N concentrations, high C/N ratios, and high phenol/lignin concentrations. Here, we attempt to resolve these inconsistent results by developing a new conceptual model that links litter quality to the soil C saturation concept. Our model builds on the Microbial Efficiency-Matrix Stabilization framework (Cotrufo et al., 2013) by suggesting the effect of litter quality on SOM stabilization is modulated by the extent of soil C saturation such that high-quality litters are not always stabilized in SOM with greater efficiency than low-quality litters. © 2015 John Wiley & Sons Ltd.

Interstellar organic matter in meteorites

NASA Technical Reports Server (NTRS)

Yang, J.; Epstein, S.

1983-01-01

Deuterium-enriched hydrogen is present in organic matter in such meteorites as noncarbonaceous chondrites. The majority of the unequilibrated primitive meteorites contain hydrogen whose D/H ratios are greater than 0.0003, requiring enrichment (relative to cosmic hydrogen) by isotope exchange reactions taking place below 150 K. The D/H values presented are the lower limits for the organic compounds derived from interstellar molecules, since all processes subsequent to their formation, including terrestrial contamination, decrease their D/H ratios. In contrast, the D/H ratios of hydrogen associated with hydrated silicates are relatively uniform for the meteorites analyzed. The C-13/C-12 ratios of organic matter, irrespective of D/H ratio, lie well within those observed for the earth. Present findings suggest that other interstellar material, in addition to organic matter, is preserved and is present in high D/H ratio meteorites.

Application of TAM III to study sensitivity of soil organic matter degradation to temperature

NASA Astrophysics Data System (ADS)

Vikegard, Peter; Barros, Nieves; Piñeiro, Verónica

2014-05-01

Traditionally, studies of soil biodegradation are based on CO2 dissipation rates. CO2 is a product of aerobic degradation of labile organic substrates like carbohydrates. That limits the biodegradation concept to just one of the soil organic matter fractions. This feature is responsible for some problems to settle the concept of soil organic matter (SOM) recalcitrance and for controversial results defining sensitivity of SOM to temperature. SOM consists of highly complex macromolecules constituted by fractions with different chemical nature and redox state affecting the chemical nature of biodegradation processes. Biodegradation of fractions more reduced than carbohydrates take place through metabolic pathways that dissipate less CO2 than carbohydrate respiration, that may not dissipate CO2, or that even may uptake CO2. These compounds can be considered more recalcitrant and with lower turnover times than labile SOM just because they are degraded at lower CO2 rates that may be just a consequence of the metabolic path. Nevertheless, decomposition of every kind of organic substrate always releases heat. For this reason, the measurement of the heat rate by calorimetry yields a more realistic measurement of the biodegradation of the SOM continuum. TAM III is one of the most recent calorimeters designed for directly measuring in real time the heat rate associated with any degradation process. It is designed as a multichannel system allowing the concomitant measurement of to up 24 samples at isothermal conditions or through a temperature scanning mode from 18 to 100ºC, allowing the continous measure of any sample at controlled non-isothermal conditions. The temperature scanning mode was tested in several soil samples collected at different depths to study their sensitivity to temperature changes from 18 to 35 ºC calculating the Q10 and the activation energy (EA) by the Arrhenius equation. It was attempted to associate the obtained EA values with the soil thermal

Distribution and biodegradability of water soluble organic carbon and nitrogen in subarctic Alaskan soils under three different land uses

USDA-ARS?s Scientific Manuscript database

Water-extractable organic matter (WEOM) contains labile organic carbon (C) and nitrogen (N) and is sensitive to soil management. However, knowledge about quantitative changes of water soluble organic C (WSOC) and N (WSON) impacted by land use conversion is still limited. In this chapter, the level a...

Controls on the molecular and carbon isotopic composition of organic matter deposited in a Kimmeridgian euxinic shelf sea: evidence for preservation of carbohydrates through sulfurisation

NASA Astrophysics Data System (ADS)

Van Kaam-Peters, Heidy M. E.; Schouten, Stefan; Köster, Jörgen; Sinninghe Damstè, Jaap S.

1998-10-01

Thirteen samples from the Kimmeridge Clay Formation (KCF) in Dorset, covering all different lithologies, were studied using bulk and molecular geochemical and microscopical techniques. Our data show that the positive correlation between TOC and δ 13C TOC reported for shales (Huc et al., 1992) also holds for other lithologies (e.g., limestones) if we correct for dilution by carbonate (TOC∗). Despite the wide range of δ 13C TOC values (-26.7 to -20.7‰), the δ 13C values of individual biomarkers of algal and green sulfur bacterial origin and of kerogen pyrolysis products (i.e., n-alkanes) show in general only small changes (<2‰). This indicates that changes in the concentration of dissolved inorganic carbon (DIC) or δ 13C of DIC (δ 13C DIC) in the palaeowater column cannot account for the 6‰ difference in δ 13C TOC. Kerogen pyrolysates indicated that with increasing TOC∗, and thus increasing δ 13C TOC, carbon isotopically heavy C 1-C 3 alkylated thiophenes with a linear carbon skeleton become increasingly abundant; in the case of the Blackstone Band kerogen (TOC∗ = 63%) they dominate the pyrolysate. These thiophenes are probably derived from sulfur-bound carbohydrates in the kerogen. Algal carbohydrates are typically 5-10‰ heavier than algal lipids and differences in preservation of labile carbohydrate carbon through sulfurisation may thus explain the range in δ 13C TOC values without the need to invoke any change in water column conditions. The increasing dominance of thiophenes in the kerogen pyrolysate with increasing TOC∗ is consistent with the increasing Sulfur Index (mg S org/g TOC), the decreasing S PYRITE/S TOT ratio, and the increasing dominance of orange amorphous organic matter produced by natural sulfurisation. The organic matter of all sediments was deposited under euxinic conditions as revealed by the occurrence of isorenieratene derivatives indicating (periodic) photic zone euxinia. At times of reduced run-off from the hinterland

Chromophoric Dissolved Organic Matter across a Marine Distributed Biological Observatory in the Pacific Arctic Region

NASA Astrophysics Data System (ADS)

Berman, S. L.; Frey, K. E.; Shake, K. L.; Cooper, L. W.; Grebmeier, J. M.

2014-12-01

Dissolved organic matter (DOM) plays an important role in marine ecosystems as both a carbon source for the microbial food web (and thus a source of CO2 to the atmosphere) and as a light inhibitor in marine environments. The presence of chromophoric dissolved organic matter (CDOM; the optically active portion of total DOM) can have significant controlling effects on transmittance of sunlight through the water column and therefore on primary production as well as the heat balance of the upper ocean. However, CDOM is also susceptible to photochemical degradation, which decreases the flux of solar radiation that is absorbed. Knowledge of the current spatial and temporal distribution of CDOM in marine environments is thus critical for understanding how ongoing and future changes in climate may impact these biological, biogeochemical, and physical processes. We describe the quantity and quality of CDOM along five key productive transects across a developing Distributed Biological Observatory (DBO) in the Pacific Arctic region. The samples were collected onboard the CCGS Sir Wilfred Laurier in July 2013 and 2014. Monitoring of the variability of CDOM along transects of high productivity can provide important insights into biological and biogeochemical cycling across the region. Our analyses include overall concentrations of CDOM, as well as proxy information such as molecular weight, lability, and source (i.e., autochthonous vs. allochthonous) of organic matter. We utilize these field observations to compare with satellite-derived CDOM concentrations determined from the Aqua MODIS satellite platform, which ultimately provides a spatially and temporally continuous synoptic view of CDOM concentrations throughout the region. Examining the current relationships among CDOM, sea ice variability, biological productivity, and biogeochemical cycling in the Pacific Arctic region will likely provide key insights for how ecosystems throughout the region will respond in future

The use of amino acid indices for assessing organic matter quality and microbial abundance in deep-sea Antarctic sediments of IODP Expedition 318

USGS Publications Warehouse

Carr, Stephanie A; Mills, Christopher T.; Mandernack, Kevin W

2016-01-01

The Adélie Basin, located offshore of the Wilkes Land margin, experiences unusually high sedimentation rates (~ 2 cm yr− 1) for the Antarctic coast. This study sought to compare depthwise changes in organic matter (OM) quantity and quality with changes in microbial biomass with depth at this high-deposition site and an offshore continental margin site. Sediments from both sites were collected during the International Ocean Drilling (IODP) Program Expedition 318. Viable microbial biomass was estimated from concentrations of bacterial-derived phospholipid fatty acids, while OM quality was assessed using four different amino acid degradation proxies. Concentrations of total hydrolysable amino acids (THAA) measured from the continental margin suggest an oligotrophic environment, with THAA concentrations representing only 2% of total organic carbon with relative proportions of non-protein amino acids β-alanine and γ-aminobutyric acid as high as 40%. In contrast, THAA concentrations from the near-shore Adélie Basin represent 40%–60% of total organic carbon. Concentrations of β-alanine and γ-aminobutyric acid were often below the detection limit and suggest that the OM of the basin as labile. DI values in surface sediments at the Adélie and margin sites were measured to be + 0.78 and − 0.76, reflecting labile and more recalcitrant OM, respectively. Greater DI values in deeper and more anoxic portions of both cores correlated positively with increased relative concentrations of phenylalanine plus tyrosine and may represent a change of redox conditions, rather than OM quality. This suggests that DI values calculated along chemical profiles should be interpreted with caution. THAA concentrations, the percentage of organic carbon (CAA%) and total nitrogen (NAA%) represented by amino acids at both sites demonstrated a significant positive correlation with bacterial abundance estimates. These data suggest that the selective degradation of amino acids, as

Dissolved and labile concentrations of Cd, Cu, Pb, and Zn in the South Fork Coeur d'Alene River, Idaho: Comparisons among chemical equilibrium models and implications for biotic ligand models

USGS Publications Warehouse

Balistrieri, L.S.; Blank, R.G.

2008-01-01

In order to evaluate thermodynamic speciation calculations inherent in biotic ligand models, the speciation of dissolved Cd, Cu, Pb, and Zn in aquatic systems influenced by historical mining activities is examined using equilibrium computer models and the diffusive gradients in thin films (DGT) technique. Several metal/organic-matter complexation models, including WHAM VI, NICA-Donnan, and Stockholm Humic model (SHM), are used in combination with inorganic speciation models to calculate the thermodynamic speciation of dissolved metals and concentrations of metal associated with biotic ligands (e.g., fish gills). Maximum dynamic metal concentrations, determined from total dissolved metal concentrations and thermodynamic speciation calculations, are compared with labile metal concentrations measured by DGT to assess which metal/organic-matter complexation model best describes metal speciation and, thereby, biotic ligand speciation, in the studied systems. Results indicate that the choice of model that defines metal/organic-matter interactions does not affect calculated concentrations of Cd and Zn associated with biotic ligands for geochemical conditions in the study area, whereas concentrations of Cu and Pb associated with biotic ligands depend on whether the speciation calculations use WHAM VI, NICA-Donnan, or SHM. Agreement between labile metal concentrations and dynamic metal concentrations occurs when WHAM VI is used to calculate Cu speciation and SHM is used to calculate Pb speciation. Additional work in systems that contain wide ranges in concentrations of multiple metals should incorporate analytical speciation methods, such as DGT, to constrain the speciation component of biotic ligand models. ?? 2008 Elsevier Ltd.

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.

Permafrost and land cover as controlling factors for light fraction organic matter on the southern Qinghai-Tibetan plateau.

PubMed

Wu, Xiaodong; Zhao, Lin; Hu, Guojie; Liu, Guimin; Li, Wangping; Ding, Yongjian

2018-02-01

Permafrost degradation can stimulate the decomposition of organic soil matter and cause a large amount of greenhouse gas emissions into the atmosphere. The light fraction organic matter (LFOM) is a labile substrate for microbial decomposition and probably plays an important role in future permafrost carbon cycles. However, little is known about the distribution of LFOM and its relationship with permafrost and environmental factors. Here, we investigated the light fraction carbon (LFC) and nitrogen (LFN) contents and stocks under meadows and wet meadows with different permafrost conditions on the southern Qinghai-Tibetan Plateau. Our results showed that LFC and LFN were mainly distributed in the upper 30cm of soils, and the sites with permafrost had significantly higher contents of LFC and LFN than those from the sites without existing permafrost. The LFC and LFN decreased sharply with depth, suggesting that the soil organic matter (SOM) in this area was highly decomposed in deep soils. Soil moisture and bulk density explained approximately 50% of the variances in LFC and LFN for all the sampling sites, while soil moisture explained approximately 30% of the variance in permafrost sites. Both the C:N ratios and LFC:LFN ratios in the sites with permafrost were higher than those in the sites without permafrost. The results suggested that the permafrost and land cover types are the main factors controlling LFOM content and stock, and that permafrost degradation would lead to a decrease of LFOM and soil C:N ratios, thus accelerating the decomposition of SOM. Copyright © 2017 Elsevier B.V. All rights reserved.

Organic matter dynamics in Technosols created with metalliferous mine residues, biochar and marble waste

NASA Astrophysics Data System (ADS)

Moreno-Barriga, Fabián; Acosta, José A.; Ángeles Muñoz, M.; Faz, Ángel; Zornoza, Raúl

2017-04-01

Creation of Technosols by use of different materials can be a sustainable strategy to reclaim mine tailings spread on the environment. A proper selection of materials is critical to efficiently contribute to soil creation, with development of soil structure, organic matter stabilization and stimulation of microbial growth. For this purpose, a short-term incubation experiment was designed with biochars derived from different feedstocks, added to tailings alone or in combination with marble waste (MaW). We aimed to assess the effects of the different materials on the evolution of C and N contents and pools, greenhouse gas (GHG) emissions, aggregate stability, and microbial biomass and activity. Results showed that carbonates provided by MaW increased pH around the target value of 8, with significant decrease in salinity by precipitation of soluble salts. Organic C and total N remained stable during the incubation, with high recalcitrant indices. Labile and soluble C and N pools were low in Technosols, with no differences with unamended tailings at the end of incubation. All biochars increased aggregate stability with regard to control by 40%, with no effect of addition of MaW. Biochars significantly increased microbial biomass C during the first 7 days of incubation; however, from this date, there were no significant differences with unamended tailings. The β-glucosidase activity was below detection limit in all samples, while arylesterase activity increased in biochar-amended samples favored by increases in pH. CO2 emissions were not significantly affected by any amendment, while N2O emissions increased with the addition of biochars with lower recalcitrance. CH4 emissions decreased in all Technosols receiving biochar. Thus, the combined use of biochar and MaW contributed to soil C sequestration and improved soil structure. However, labile sources of organic compounds would be needed to stimulate microbial populations in the Technosols. Acknowledgements This work

Features of distribution and quality of organic matter in the bottom sediments of the Great Peter Bay (Sea of Japan)

NASA Astrophysics Data System (ADS)

Nesterova, Olga; Tregubova, Valentina; Semal, Victoria; Vasenev, Ivan

2017-04-01

The nature and distribution of organic carbon in marine waters depends on: 1) biological productivity and revenue of the autochthonous organic matter to the bottom; 2) sediment grain-size composition and conditions of dumping, which in turn depends of hydrothermic regime, topography, speed River mist and received major erosion products; 3) living conditions of the benthos (the quantity consumed of OM, gas regime of habitats, physiological capacity of heterotrophs). Autochthonous OM of phytoplankton plays a dominant role in the processes of formation of humus in aquatic conditions. Bottom sediments at different distance from the shoreline to depths from 0.5 up to 480 m of the Sea of Japan, which are formed in various conditions of facies, were selected as the objects of study. There is no clear relationships to the amount of organic matter in bottom sediments on the characteristics of the distribution and nature of living matter in the oceans and seas. This is because the process of sedimentation and fossilization of organic matter on the seabed and the ocean floor depends on many factors (currents, depth). Humus of studied bottom sediments in composition can be attributed mainly to the humic type. Nonhydrolyzing rest is 70-90%. This is characteristic of bottom sediments formed in facial types of small bays, internal coastal shelf bights and the underwater slope. At a fraction of the carbon of humic acids in organic matter, ranging from 4 to 80% of the amount of humic and fulvic acids. Fulvic acids content is much less. This is due to more favourable conservation situation of humic acids in precipitation with high content of organic matter, whereas fulvic acids in aquatic environments are more labile and almost not dumped. Despite the fact humic acids are not the most stable component (s), however, with increased content of humic acids, the mobility of organic matter and removing it from the bottom sediments are reduced. Internal shelf facies of the Great Peter Bay

The Role of Priming in the Development of Stable and Radioactive Carbon Isotope Profiles of Soil Organic Matter

NASA Astrophysics Data System (ADS)

Serach, L.; Breecker, D.

2017-12-01

The stability of soil carbon (C) is one of the largest sources of uncertainty in global C cycle models and is central to identifying potential feedbacks to a warming climate. The role that more stable soil organic matter (SOM) pools could have in these feedbacks is highly uncertain. Stable C isotope (δ13C) and radiocarbon (14C) SOM profiles are used to understand the processes involved in soil C stabilization. In this study, we use a 1-dimensional, 3 pool soil C model to simulate the development of SOM δ13C and 14C profiles in a well-drained forest soil. Under the simplest model scenario where decomposition rate constants for each SOM pool remain fixed, model runs exhibit a buildup of slowly degrading C in the shallow subsurface (0-5cm) where fresh, labile C typically dominates in natural soils. Additionally, magnitudes of trends in SOM δ13C and 14C profiles were inconsistent with those observed in natural profiles, suggesting a deficiency in this version of the model. We hypothesize that the observed disparity between modeled and natural profiles is due to the absence of priming in the model. Priming effects presume a change in decomposition rate constants for recalcitrant C pools upon the addition of labile C to the soil. As such, priming effects were simulated in the model by making decomposition rate constants a function of labile C input (e.g., root C and leaf litter). The incorporation of priming into the model yields larger, more realistic shifts in SOM δ13C profiles and trends in 14C profiles that vary based on the sensitivity of recalcitrant pools to labile C addition. So far, the results from this study support the hypothesis that SOM δ13C and 14C profiles cannot be explained without priming. These results highlight the importance of priming to our understanding of the persistence of stable C in the soil and our ability to use SOM δ13C and 14C trends as a means to quantify C stability.

Characteristics of dissolved organic matter in the Upper Klamath River, Lost River, and Klamath Straits Drain, Oregon and California

USGS Publications Warehouse

Goldman, Jami H.; Sullivan, Annett B.

2017-12-11

Concentrations of particulate organic carbon (POC) and dissolved organic carbon (DOC), which together comprise total organic carbon, were measured in this reconnaissance study at sampling sites in the Upper Klamath River, Lost River, and Klamath Straits Drain in 2013–16. Optical absorbance and fluorescence properties of dissolved organic matter (DOM), which contains DOC, also were analyzed. Parallel factor analysis was used to decompose the optical fluorescence data into five key components for all samples. Principal component analysis (PCA) was used to investigate differences in DOM source and processing among sites.At all sites in this study, average DOC concentrations were higher than average POC concentrations. The highest DOC concentrations were at sites in the Klamath Straits Drain and at Pump Plant D. Evaluation of optical properties indicated that Klamath Straits Drain DOM had a refractory, terrestrial source, likely extracted from the interaction of this water with wetland peats and irrigated soils. Pump Plant D DOM exhibited more labile characteristics, which could, for instance, indicate contributions from algal or microbial exudates. The samples from Klamath River also had more microbial or algal derived material, as indicated by PCA analysis of the optical properties. Most sites, except Pump Plant D, showed a linear relation between fluorescent dissolved organic matter (fDOM) and DOC concentration, indicating these measurements are highly correlated (R2=0.84), and thus a continuous fDOM probe could be used to estimate DOC loads from these sites.

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.

Subcritical water extraction of organic matter from sedimentary rocks.

PubMed

Luong, Duy; Sephton, Mark A; Watson, Jonathan S

2015-06-16

Subcritical water extraction of organic matter containing sedimentary rocks at 300°C and 1500 psi produces extracts comparable to conventional solvent extraction. Subcritical water extraction of previously solvent extracted samples confirms that high molecular weight organic matter (kerogen) degradation is not occurring and that only low molecular weight organic matter (free compounds) are being accessed in analogy to solvent extraction procedures. The sedimentary rocks chosen for extraction span the classic geochemical organic matter types. A type I organic matter-containing sedimentary rock produces n-alkanes and isoprenoidal hydrocarbons at 300°C and 1500 psi that indicate an algal source for the organic matter. Extraction of a rock containing type II organic matter at the same temperature and pressure produces aliphatic hydrocarbons but also aromatic compounds reflecting the increased contributions from terrestrial organic matter in this sample. A type III organic matter-containing sample produces a range of non-polar and polar compounds including polycyclic aromatic hydrocarbons and oxygenated aromatic compounds at 300°C and 1500 psi reflecting a dominantly terrestrial origin for the organic materials. Although extraction at 300°C and 1500 psi produces extracts that are comparable to solvent extraction, lower temperature steps display differences related to organic solubility. The type I organic matter produces no products below 300°C and 1500 psi, reflecting its dominantly aliphatic character, while type II and type III organic matter contribute some polar components to the lower temperature steps, reflecting the chemical heterogeneity of their organic inventory. The separation of polar and non-polar organic compounds by using different temperatures provides the potential for selective extraction that may obviate the need for subsequent preparative chromatography steps. Our results indicate that subcritical water extraction can act as a suitable

Seasonal variation in the quality of dissolved and particulate organic matter exchanged between a salt marsh and its adjacent estuary

NASA Astrophysics Data System (ADS)

Osburn, Christopher L.; Mikan, Molly P.; Etheridge, J. Randall; Burchell, Michael R.; Birgand, François

2015-07-01

Fluorescence was used to examine the quality of dissolved and particulate organic matter (DOM and POM) exchanging between a tidal creek in a created salt marsh and its adjacent estuary in eastern North Carolina, USA. Samples from the creek were collected hourly over four tidal cycles in May, July, August, and October 2011. Absorbance and fluorescence of chromophoric DOM (CDOM) and of base-extracted POM (BEPOM) served as the tracers for organic matter quality while dissolved organic carbon (DOC) and base-extracted particulate organic carbon (BEPOC) were used to compute fluxes. Fluorescence was modeled using parallel factor analysis (PARAFAC) and principle components analysis (PCA) of the PARAFAC results. Of nine PARAFAC components (C) modeled, C3 represented recalcitrant DOM and C4 represented fresher soil-derived source DOM. Component 1 represented detrital POM, and C6 represented planktonic POM. Based on mass balance, recalcitrant DOC export was 86 g C m-2 yr-1 and labile DOC export was 49 g C m-2 yr-1; no planktonic DOC was exported. The marsh also exported 41 g C m-2 yr-1 of detrital terrestrial POC, which likely originated from lands adjacent to the North River estuary. Planktonic POC export from the marsh was 6 g C m-2 yr-1. Assuming the exported organic matter was oxidized to CO2 and scaled up to global salt marsh area, respiration of salt marsh DOC and POC transported to estuaries could amount to a global CO2 flux of 11 Tg C yr-1, roughly 4% of the recently estimated CO2 release for marshes and estuaries globally.

Coupled biotic-abiotic oxidation of organic matter by biogenic MnO_{2}

NASA Astrophysics Data System (ADS)

Gonzalez, Julia; Peña, Jasquelin

2016-04-01

Some reactive soil minerals are strongly implicated in stabilising organic matter. However, others can play an active role in the oxidation of organic molecules. In natural systems, layer-type manganese oxide minerals (MnO2) typically occur as biomineral assemblages consisting of mineral particles and microbial biomass. Both the mineral and biological fractions of the assemblage can be powerful oxidants of organic C. The biological compartment relies on a set of enzymes to drive oxidative transformations of reduced C-substrates, whereas MnO2 minerals are strong, less specific abiotic oxidants that are assumed to rely on interfacial interactions between C-substrates and the mineral surface. This project aims to understand the coupling between microbial C mineralization and abiotic C oxidation mediated by MnO2 in bacterial-MnO2 assemblages. Specifically, under conditions of high C turnover, microbial respiration can significantly alter local pH, dissolved oxygen and pool of available reductants, which may modify rates and mechanism of C oxidation by biotic and abiotic components. We first investigated changes in the solution chemistry of Pseudomonas putida suspensions exposed to varying concentrations of glucose, chosen to represent readily bioavailable substrates in soils. Glucose concentrations tested ranged between 0 and 5.5mM and changes in pH, dissolved oxygen and dissolved organic and inorganic carbon were tracked over 48h. We then combined literature review and wet-chemical experiments to compile the pH dependence of rates of organic substrate oxidation by MnO2, including glucose. Our results demonstrate a strong pH dependence for these abiotic reactions. In assemblages of P. putida - MnO2, kinetic limitations for abiotic C oxidation by MnO2 are overcome by changes in biogeochemical conditions that result from bacterial C metabolism. When extrapolated to a soil solution confronted to an input of fresh dissolved organic matter, bacterial C metabolism of the

Study of Organic Matter in Soils of the Amazon Region Employing Laser Induced Fluorescence Spectroscopy

NASA Astrophysics Data System (ADS)

Tadini, Amanda Maria; Nicolodelli, Gustavo; Mounier, Stéphane; Montes, Célia Regina; Marcondes Bastos Pereira Milori, Débora

2014-05-01

were a discontinuity in the accumulation of humified organic matter in the progress of depth. A hypothesis for occurrence of this behavior might be due to texture sandy and aggregate stability present in these soils, which can be difficulty the degradation of labile chains organic matter, thus promoting carbon sequestration in the long time in these soils. References [1]-Milori, D. M. B. P.; Galeti, H. V .A.; Martin-Neto, L.; Dieckow, J.; González-Pérez, M.; Bayer, C.; Salton, J. Organic matter study of whole soil samples using laser-induced fluorescense spectroscopy. Soil Science Society of America Journal, 70, 57-63, 2006. [2]-Martins, T.; Saab, S. C.; Milori, D. M. B. P.; Brinatti, A. M.; Rosa, J. A.; Cassaro, F. A. M.; Pires, L. F. Soil organic matter humification under diferente tillage managements evaluated by Laser Induced Fluorescence (LIF) and C/N ratio. Soil & Tillage Research, 111, 231-235, 2011. [3]-Milori, D. M. B. P.; Segnini, A.; Silva, W. T. L.; Posadas, A.; Mares, V.; Quiroz, R.; Martin-Neto, L. Emerging techniques for soil carbon measurements. Research Program on Climate Change, Agriculture and Food Security, nº 2, 2011. [4]-Senesi, N.; Plaza, C.; Brunetti, G.; Polo, A. A comparative survey of recente results on humic-like fractions in organic amendments and effects on native soil humic substances. Soil Biology & Biochemistry, 39, 1244-1262, 2007.

FTIR-PAS: a powerful tool for characterising the chemical composition and predicting the labile C fraction of various organic waste products.

PubMed

Bekiaris, Georgios; Bruun, Sander; Peltre, Clément; Houot, Sabine; Jensen, Lars S

2015-05-01

Fourier transform infrared (FT-IR) spectroscopy has been used for several years as a fast, low-cost, reliable technique for characterising a large variety of materials. However, the strong influence of sample particle size and the inability to measure the absorption of very dark and opaque samples have made FTIR unsuitable for many waste materials. FTIR-photoacoustic spectroscopy (FTIR-PAS) can eliminate some of the shortcomings of traditional FTIR caused by scattering effects and reflection issues, and recent advances in PAS technology have made commercial instruments available. In this study, FTIR-PAS was used to characterise a wide range of organic waste products and predict their labile carbon fraction, which is normally determined from time-consuming assays. FTIR-PAS was found to be capable of predicting the labile fraction of carbon as efficiently as near infrared spectroscopy (NIR) and furthermore of identifying the compounds that are correlated with the predicted parameter, thus facilitating a more mechanistic interpretation. Copyright © 2015 Elsevier Ltd. All rights reserved.

Organic matters: investigating the sources, transport, and fate of organic matter in Fanno Creek, Oregon

USGS Publications Warehouse

Sobieszczyk, Steven; Keith, Mackenzie K.; Goldman, Jami H.; Rounds, Stewart A.

2015-01-01

The U.S. Geological Survey (USGS), in cooperation with Clean Water Services, recently completed an investigation into the sources, transport, and fate of organic matter in the Fanno Creek watershed. The information provided by this investigation will help resource managers to implement strategies aimed at decreasing the excess supply of organic matter that contributes to low dissolved-oxygen levels in Fanno Creek and downstream in the Tualatin River during summer. This fact sheet summarizes the findings of the investigation.

The effects of organic matter-mineral interactions and organic matter chemistry on diuron sorption across a diverse range of soils.

PubMed

Smernik, Ronald J; Kookana, Rai S

2015-01-01

Sorption of non-ionic organic compounds to soil is usually expressed as the carbon-normalized partition coefficient (KOC), because it is assumed that the main factor that influences the amount sorbed is the organic carbon content of the soil. However, KOC can vary by a factor of at least ten across a range of soils. We investigated two potential causes of variation in diuron KOC - organic matter-mineral interactions and organic matter chemistry - for a diverse set of 34 soils from Sri Lanka, representing a wide range of soil types. Treatment with hydrofluoric acid (HF-treatment) was used to concentrate soil organic matter. HF-treatment increased KOC for the majority of soils (average factor 2.4). We attribute this increase to the blocking of organic matter sorption sites in the whole soils by minerals. There was no significant correlation between KOC for the whole soils and KOC for the HF-treated soils, indicating that the importance of organic matter-mineral interactions varied greatly amongst these soils. There was as much variation in KOC across the HF-treated soils as there was across the whole soils, indicating that the nature of soil organic matter is also an important contributor to KOC variability. Organic matter chemistry, determined by solid-state (13)C nuclear magnetic resonance (NMR) spectroscopy, was correlated with KOC for the HF-treated soils. In particular, KOC increased with the aromatic C content (R=0.64, p=1×10(-6)), and decreased with O-alkyl C (R=-0.32, p=0.03) and alkyl C (R=-0.41, p=0.004) content. Copyright © 2014 Elsevier Ltd. All rights reserved.

Trace metal mobilization by organic soil amendments: insights gained from analyses of solid and solution phase complexation of cadmium, nickel and zinc.

PubMed

Welikala, Dharshika; Hucker, Cameron; Hartland, Adam; Robinson, Brett H; Lehto, Niklas J

2018-05-01

The accumulation of Cd in soils worldwide has increased the demand for methods to reduce the metal's plant bioavailability. Organic matter rich soil amendments have been shown to be effective in achieving this. However, it is not known how long these amendments can retain the Cd, and whether dissolved organic matter (DOM) released from them can enhance the metal's mobility in the environment. In this study we sought to test the Cd binding capacity of various organic soil amendments, and evaluate differences in characteristics of the DOM released to see if they can explain the lability of the Cd-DOM complexes. We collected ten organic soil amendments from around New Zealand: five different composts, biosolids from two sources, two types of peat and spent coffee grounds. We characterised the amendments' elemental composition and their ability to bind the Cd. We then selected two composts and two peats for further tests, where we measured the sorption of Ni or Zn by the amendments. We analysed the quality of the extracted DOM from the four amendments using 3D Excitation Emission Matrix analysis, and tested the lability of the metal-DOM complexes using an adapted diffusive gradients in thin-films (DGT) method. We found that composts bound the most Cd and that the emergent Cd-DOM complexes were less labile than those from the peats. Ni-DOM complexes were the least labile. The aromaticity of the extracted DOM appears to be an important factor in determining the lability of Ni complexes, but less so for Zn and Cd. Copyright © 2018 Elsevier Ltd. All rights reserved.

Direct and indirect controls on organic matter decomposition in four coastal wetland communities along a landscape salinity gradient

USGS Publications Warehouse

Stagg, Camille L.; Baustian, Melissa M.; Perry, Carey L.; Carruthers, Tim J.B.; Hall, Courtney T.

2018-01-01

Coastal wetlands store more carbon than most ecosystems globally. As sea level rises, changes in flooding and salinity will potentially impact ecological functions, such as organic matter decomposition, that influence carbon storage. However, little is known about the mechanisms that control organic matter loss in coastal wetlands at the landscape scale. As sea level rises, how will the shift from fresh to salt-tolerant plant communities impact organic matter decomposition? Do long-term, plant-mediated, effects of sea-level rise differ from direct effects of elevated salinity and flooding?We identified internal and external factors that regulated indirect and direct pathways of sea-level rise impacts, respectively, along a landscape-scale salinity gradient that incorporated changes in wetland type (fresh, oligohaline, mesohaline and polyhaline marshes). We found that indirect and direct impacts of sea-level rise had opposing effects on organic matter decomposition.Salinity had an indirect effect on litter decomposition that was mediated through litter quality. Despite significant variation in environmental conditions along the landscape gradient, the best predictors of above- and below-ground litter decomposition were internal drivers, initial litter nitrogen content and initial litter lignin content respectively. Litter decay constants were greatest in the oligohaline marsh and declined with increasing salinity, and the fraction of litter remaining (asymptote) was greatest in the mesohaline marsh. In contrast, direct effects of salinity and flooding were positive. External drivers, salinity and flooding, stimulated cellulytic activity, which was highest in the polyhaline marsh.Synthesis. Our results indicate that as sea level rises, initial direct effects of salinity will stimulate decay of labile carbon, but over time as plant communities shift from fresh to polyhaline marsh, litter decay will decline, yielding greater potential for long-term carbon storage

Sample storage-induced changes in the quantity and quality of soil labile organic carbon

PubMed Central

Sun, Shou-Qin; Cai, Hui-Ying; Chang, Scott X.; Bhatti, Jagtar S.

2015-01-01

Effects of sample storage methods on the quantity and quality of labile soil organic carbon are not fully understood even though their effects on basic soil properties have been extensively studied. We studied the effects of air-drying and frozen storage on cold and hot water soluble organic carbon (WSOC). Cold- and hot-WSOC in air-dried and frozen-stored soils were linearly correlated with those in fresh soils, indicating that storage proportionally altered the extractability of soil organic carbon. Air-drying but not frozen storage increased the concentrations of cold-WSOC and carbohydrate in cold-WSOC, while both increased polyphenol concentrations. In contrast, only polyphenol concentration in hot-WSOC was increased by air-drying and frozen storage, suggesting that hot-WSOC was less affected by sample storage. The biodegradability of cold- but not hot-WSOC was increased by air-drying, while both air-drying and frozen storage increased humification index and changed specific UV absorbance of both cold- and hot-WSOC, indicating shifts in the quality of soil WSOC. Our results suggest that storage methods affect the quantity and quality of WSOC but not comparisons between samples, frozen storage is better than air-drying if samples have to be stored, and storage should be avoided whenever possible when studying the quantity and quality of both cold- and hot-WSOC. PMID:26617054

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.

Molybdenum isotope fractionation during adsorption to organic matter

USGS Publications Warehouse

King, Elizabeth K.; Perakis, Steven; Pett-Ridge, Julie C.

2018-01-01

Organic matter is of emerging interest as a control on molybdenum (Mo) biogeochemistry, and information on isotope fractionation during adsorption to organic matter can improve interpretations of Mo isotope variations in natural settings. Molybdenum isotope fractionation was investigated during adsorption onto insolubilized humic acid (IHA), a surrogate for organic matter, as a function of time (2–170 h) and pH (2–7). For the time series experiment performed at pH 4.2, the average Mo isotope fractionation between the solution and the IHA (Δ98Mosolution-IHA) was 1.39‰ (± 0.16‰, 2σ, based on 98Mo/95Mo relative to the NIST 3134 standard) at steady state. For the pH series experiment, Mo adsorption decreased as pH increased from 2.0 to 6.9, and the Δ98Mosolution-IHA increased from 0.82‰ to 1.79‰. We also evaluated natural Mo isotope patterns in precipitation, foliage, organic horizon, surface mineral soil, and bedrock from 12 forested sites in the Oregon Coast Range. The average Mo isotope offset observed between precipitation and organic (O) horizon soil was 2.1‰, with light Mo isotopes adsorbing preferentially to organic matter. Fractionation during adsorption to organic matter is similar in magnitude and direction to prior observations of Mo fractionation during adsorption to Fe- and Mn- (oxyhydr)oxides. Our finding that organic matter influences Mo isotope composition has important implications for the role of organic matter as a driver of trace metal retention and isotopic fractionation.

Molybdenum isotope fractionation during adsorption to organic matter

NASA Astrophysics Data System (ADS)

King, E. K.; Perakis, S. S.; Pett-Ridge, J. C.

2018-02-01

Organic matter is of emerging interest as a control on molybdenum (Mo) biogeochemistry, and information on isotope fractionation during adsorption to organic matter can improve interpretations of Mo isotope variations in natural settings. Molybdenum isotope fractionation was investigated during adsorption onto insolubilized humic acid (IHA), a surrogate for organic matter, as a function of time (2-170 h) and pH (2-7). For the time series experiment performed at pH 4.2, the average Mo isotope fractionation between the solution and the IHA (Δ98Mosolution-IHA) was 1.39‰ (±0.16‰, 2σ, based on 98Mo/95Mo relative to the NIST 3134 standard) at steady state. For the pH series experiment, Mo adsorption decreased as pH increased from 2.0 to 6.9, and the Δ98Mosolution-IHA increased from 0.82‰ to 1.79‰. We also evaluated natural Mo isotope patterns in precipitation, foliage, organic horizon, surface mineral soil, and bedrock from 12 forested sites in the Oregon Coast Range. The average Mo isotope offset observed between precipitation and organic (O) horizon soil was 2.1‰, with light Mo isotopes adsorbing preferentially to organic matter. Fractionation during adsorption to organic matter is similar in magnitude and direction to prior observations of Mo fractionation during adsorption to Fe- and Mn- (oxyhydr)oxides. Our finding that organic matter influences Mo isotope composition has important implications for the role of organic matter as a driver of trace metal retention and isotopic fractionation.

An original data treatment for infrared spectra of organic matter, application to extracted soil organic matter

NASA Astrophysics Data System (ADS)

Gomes Rossin, Bruna; Redon, Roland; Raynaud, Michel; Nascimento, Nadia Regina; Mounier, Stéphane

2017-04-01

Infrared spectra of extracted organic matter are easy and rapid to do, but generally hard to interpreted over the presence or not of certain organic functions. Indeed, the organic matter is a complex mixture of molecules often having absorption overlapping and it is also difficult to have a well calibrated or normalised spectra due to the difficulty to have a well known solid content or homogeneity for a sample (Monakhova et al. 2015, Tadini et al. 2015, Bardy et al. 2008). In this work, the IRTF (InfraRed Fourier Transform) spectra were treated by an original algorithm developed to obtain the principal components of the IRTF spectra and their contributions for each sample. This bilinear decomposition used a PCA initialisation and the principal components were estimated from vectors calculated by PCA and linearly combined to provide non-negative signals minimizing a criterion based on cross-correlation. Hence, using this decomposition, it is possible to define IRTF signal of organic matter fractions like humic acid or fulvic acid depending on their origin like surface of depth of soil profiles. The method was used on a set of sample from Upper Negro River Basin (Amazon, Brazil) (Bueno,2009), where three soils sequences from surface to two meter depth containing 10 slices each. The sequences were sampled on a podzol well drain, a hydromorphic podzol and a cryptopodzol. From the IRTF data five representative component spectra were defined for all the extracted organic matter , and using other chemical composition information, a mechanism of organic matter fate is proposed to explain the observed results. Bardy, M., E. Fritsch, S. Derenne, T. Allard, N. R. do Nascimento, and G. T. Bueno. 2008. "Micromorphology and Spectroscopic Characteristics of Organic Matter in Waterlogged Podzols of the Upper Amazon Basin." Geoderma 145 (3-4): 222-30. Bueno, G.T. Appauvrissement et podzolisation des latérites du baissin du Rio Negro et gênese dês Podzols dans le haut bassin

Temperature responses of individual soil organic matter components

NASA Astrophysics Data System (ADS)

Feng, Xiaojuan; Simpson, Myrna J.

2008-09-01

Temperature responses of soil organic matter (SOM) remain unclear partly due to its chemical and compositional heterogeneity. In this study, the decomposition of SOM from two grassland soils was investigated in a 1-year laboratory incubation at six different temperatures. SOM was separated into solvent extractable compounds, suberin- and cutin-derived compounds, and lignin-derived monomers by solvent extraction, base hydrolysis, and CuO oxidation, respectively. These SOM components have distinct chemical structures and stabilities and their decomposition patterns over the course of the experiment were fitted with a two-pool exponential decay model. The stability of SOM components was also assessed using geochemical parameters and kinetic parameters derived from model fitting. Compared with the solvent extractable compounds, a low percentage of lignin monomers partitioned into the labile SOM pool. Suberin- and cutin-derived compounds were poorly fitted by the decay model, and their recalcitrance was shown by the geochemical degradation parameter (ω - C16/∑C16), which was observed to stabilize during the incubation. The temperature sensitivity of decomposition, expressed as Q10, was derived from the relationship between temperature and SOM decay rates. SOM components exhibited varying temperature responses and the decomposition of lignin monomers exhibited higher Q10 values than the decomposition of solvent extractable compounds. Our study shows that Q10 values derived from soil respiration measurements may not be reliable indicators of temperature responses of individual SOM components.

Controls on the distribution of arsenic in lake sediments impacted by 65 years of gold ore processing in subarctic Canada: the role of organic matter

NASA Astrophysics Data System (ADS)

Galloway, Jennifer; Palmer, Michael; Swindles, Graeme T.; Sanei, Hamed; Jamieson, Heather E.; Parsons, Michael; Macumber, Andrew L.; Patterson, Tim; Falck, Hendrik

2017-04-01

Gold mines in the Yellowknife region of the Northwest Territories, Canada, operated from 1938 to 2003 and released approximately 20,000 tonnes of arsenic trioxide to the environment through stack emissions. This release resulted in highly elevated arsenic concentrations in lake surface waters and sediments relative to Canadian drinking water standards and guidelines for the protection of aquatic life. High northern latitudes are experiencing substantial impacts, including changes in bio-physico-chemical processes, due to climate change. Determining the affect of warming climate on contamination is complicated by the fact that little is known of climate change controls on As mobility and bioavailability. Further, while the role of dissolved organic matter in As cycling is relatively well characterized in soils and wetland sediments, few studies have investigated the role of solid organic matter in lacustrine systems. We use a meta-analytical approach to better understand controls on sedimentary arsenic distribution in lakes within a 50 km2 area of historic mineral processing activities. Arsenic concentrations in near surface sediments of the 100 lakes studied range from 5 mg/kg to over 10,000 mg/kg (median 81 mg/kg). Distance from the historical Giant Mine roaster stack and the amount of labile organic matter (S1 carbon as determined by Rock Eval pyrolysis) in lake sediments are the variables most strongly correlated with sedimentary As concentrations (Spearman's rank correlation As:distance from historic roaster rs=-0.57, p<0.05; As:S1 rs=0.55, p<0.05). The S1 fraction, volatile hydrocarbons derived from readily degradable geolipids and pigments predominantly originating from authochthonous organic matter, represents a small portion of the overall total organic carbon in the sedimentary material analyzed (median 2.33 wt.%). However, this fraction of organic matter has large potential to influence element concentrations in lake sediments through coating of pre

Shape-preserving transformations of organic matter and compositions thereof

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

Kaehr, Bryan J.; Meyer, Kristin; Townson, Jason L.

The present invention relates to methods of transforming organic matter into organic-inorganic composites, inorganic replicas, or conductive replicas. Organic matter, such as biological cells and tissue and organs, can be converted into such composites and replicas using the methods described herein. In particular, such methods transform organic matter (into inorganic, organic-inorganic, or conductive constructs), while simultaneously preserving microscopic and/or macroscopic structural detail.

Dynamics of organic matter and microbial populations in amended soil: a multidisciplinary approach

NASA Astrophysics Data System (ADS)

Gigliotti, Giovanni; Pezzolla, Daniela; Zadra, Claudia; Albertini, Emidio; Marconi, Gianpiero; Turchetti, Benedetta; Buzzini, Pietro

2013-04-01

The application of organic amendments to soils, such as pig slurry, sewage sludge and compost is considered a tool for improving soil fertility and enhancing C stock. The addition of these different organic materials allows a good supply of nutrients for plants but also contributes to C sequestration, affects the microbial activity and the transformation of soil organic matter (SOM). Moreover, the addition of organic amendment has gained importance as a source of greenhouse gas (GHG) emissions and then as a cause of the "Global Warming". Therefore, it is important to investigate the factors controlling the SOM mineralization in order to improve soil C sequestration and decreasing at the same time the GHG emissions. The quality of organic matter added to the soil will play an important role in these dynamics, affecting the microbial activity and the changes in microbial community structure. A laboratory, multidisciplinary experiment was carried out to test the effect of the amendment by anaerobic digested livestock-derived organic materials on labile organic matter evolution and on dynamics of microbial population, this latter both in terms of consistence of microbial biomass, as well as in terms of microbial biodiversity. Different approaches were used to study the microbial community structure: chemical (CO2 fluxes, WEOC, C-biomass, PLFA), microbiological (microbial enumeration) and molecular (DNA extraction and Roche 454, Next Generation Sequencing, NGS). The application of fresh digestate, derived from the anaerobic treatment of animal wastes, affected the short-term dynamics of microbial community, as reflected by the increase of CO2 emissions immediately after the amendment compared to the control soil. This is probably due to the addition of easily available C added with the digestate, demonstrating that this organic material was only partially stabilized by the anaerobic process. In fact, the digestate contained a high amounts of available C, which led to

Spectral mapping of soil organic matter

NASA Technical Reports Server (NTRS)

Kristof, S. J.; Baumgardner, M. F.; Johannsen, C. J.

1974-01-01

Multispectral remote sensing data were examined for use in the mapping of soil organic matter content. Computer-implemented pattern recognition techniques were used to analyze data collected in May 1969 and May 1970 by an airborne multispectral scanner over a 40-km flightline. Two fields within the flightline were selected for intensive study. Approximately 400 surface soil samples from these fields were obtained for organic matter analysis. The analytical data were used as training sets for computer-implemented analysis of the spectral data. It was found that within the geographical limitations included in this study, multispectral data and automatic data processing techniques could be used very effectively to delineate and map surface soils areas containing different levels of soil organic matter.

Organic matter control on the distribution of arsenic in lake sediments impacted by ~65years of gold ore processing in subarctic Canada.

PubMed

Galloway, Jennifer M; Swindles, Graeme T; Jamieson, Heather E; Palmer, Michael; Parsons, Michael B; Sanei, Hamed; Macumber, Andrew L; Timothy Patterson, R; Falck, Hendrik

2018-05-01

Climate change is profoundly affecting seasonality, biological productivity, and hydrology in high northern latitudes. In sensitive subarctic environments exploitation of mineral resources led to contamination and it is not known how cumulative effects of resource extraction and climate warming will impact ecosystems. Gold mines near Yellowknife, Northwest Territories, subarctic Canada, operated from 1938 to 2004 and released >20,000t of arsenic trioxide (As 2 O 3 ) to the environment through stack emissions. This release resulted in elevated arsenic concentrations in lake surface waters and sediments relative to Canadian drinking water standards and guidelines for the protection of aquatic life. A meta-analytical approach is used to better understand controls on As distribution in lake sediments within a 30-km radius of historic mineral processing activities. Arsenic concentrations in the near-surface sediments range from 5mg·kg -1 to over 10,000mg·kg -1 (median 81mg·kg -1 ; n=105). Distance and direction from the historic roaster stack are significantly (p<0.05) related to sedimentary As concentration, with highest As concentrations in sediments within 11km and lakes located downwind. Synchrotron-based μXRF and μXRD confirm the persistence of As 2 O 3 in near surface sediments of two lakes. Labile organic matter (S1) is significantly (p<0.05) related to As and S concentrations in sediments and this relationship is greatest in lakes within 11km from the mine. These relations are interpreted to reflect labile organic matter acting as a substrate for microbial growth and mediation of authigenic precipitation of As-sulphides in lakes close to the historic mine where As concentrations are highest. Continued climate warming is expected to lead to increased biological productivity and changes in organic geochemistry of lake sediments that are likely to play an important role in the mobility and fate of As in aquatic ecosystems. Copyright © 2017 Elsevier B.V. All

Light and heavy fractions of soil organic matter in response to climate warming and increased precipitation in a temperate steppe.

PubMed

Song, Bing; Niu, Shuli; Zhang, Zhe; Yang, Haijun; Li, Linghao; Wan, Shiqiang

2012-01-01

Soil is one of the most important carbon (C) and nitrogen (N) pools and plays a crucial role in ecosystem C and N cycling. Climate change profoundly affects soil C and N storage via changing C and N inputs and outputs. However, the influences of climate warming and changing precipitation regime on labile and recalcitrant fractions of soil organic C and N remain unclear. Here, we investigated soil labile and recalcitrant C and N under 6 years' treatments of experimental warming and increased precipitation in a temperate steppe in Northern China. We measured soil light fraction C (LFC) and N (LFN), microbial biomass C (MBC) and N (MBN), dissolved organic C (DOC) and heavy fraction C (HFC) and N (HFN). The results showed that increased precipitation significantly stimulated soil LFC and LFN by 16.1% and 18.5%, respectively, and increased LFC:HFC ratio and LFN:HFN ratio, suggesting that increased precipitation transferred more soil organic carbon into the quick-decayed carbon pool. Experimental warming reduced soil labile C (LFC, MBC, and DOC). In contrast, soil heavy fraction C and N, and total C and N were not significantly impacted by increased precipitation or warming. Soil labile C significantly correlated with gross ecosystem productivity, ecosystem respiration and soil respiration, but not with soil moisture and temperature, suggesting that biotic processes rather than abiotic factors determine variations in soil labile C. Our results indicate that certain soil carbon fraction is sensitive to climate change in the temperate steppe, which may in turn impact ecosystem carbon fluxes in response and feedback to climate change.

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.

Particulate Organic Matter Affects Soil Nitrogen Mineralization under Two Crop Rotation Systems

PubMed Central

Bu, Rongyan; Lu, Jianwei; Ren, Tao; Liu, Bo; Li, Xiaokun; Cong, Rihuan

2015-01-01

Changes in the quantity and/or quality of soil labile organic matter between and after different types of cultivation system could play a dominant role in soil nitrogen (N) mineralization. The quantity and quality of particulate organic matter (POM) and potentially mineralizable-N (PMN) contents were measured in soils from 16 paired rice-rapeseed (RR)/cotton-rapeseed (CR) rotations sites in Hubei province, central China. Then four paired soils encompassing low (10th percentile), intermediate (25th and 75th percentiles), and high (90th percentile) levels of soil PMN were selected to further study the effects of POM on soil N mineralization by quantifying the net N mineralization in original soils and soils from which POM was removed. Both soil POM carbon (POM-C) and N (POM-N) contents were 45.8% and 55.8% higher under the RR rotation compared to the CR rotation, respectively. The PMN contents were highly correlated with the POM contents. The PMN and microbial biomass N (MBN) contents concurrently and significantly decreased when POM was removed. The reduction rate of PMN was positively correlated with changes in MBN after the removal of POM. The reduction rates of PMN and MBN after POM removal are lower under RR rotations (38.0% and 16.3%, respectively) than CR rotations (45.6% and 19.5%, respectively). Furthermore, infrared spectroscopy indicated that compounds with low-bioavailability accumulated (e.g., aromatic recalcitrant materials) in the soil POM fraction under the RR rotation but not under the CR rotation. The results of the present study demonstrated that POM plays a vital role in soil N mineralization under different rotation systems. The discrepancy between POM content and composition resulting from different crop rotation systems caused differences in N mineralization in soils. PMID:26647157

Particulate Organic Matter Affects Soil Nitrogen Mineralization under Two Crop Rotation Systems.

PubMed

Bu, Rongyan; Lu, Jianwei; Ren, Tao; Liu, Bo; Li, Xiaokun; Cong, Rihuan

2015-01-01

Changes in the quantity and/or quality of soil labile organic matter between and after different types of cultivation system could play a dominant role in soil nitrogen (N) mineralization. The quantity and quality of particulate organic matter (POM) and potentially mineralizable-N (PMN) contents were measured in soils from 16 paired rice-rapeseed (RR)/cotton-rapeseed (CR) rotations sites in Hubei province, central China. Then four paired soils encompassing low (10th percentile), intermediate (25th and 75th percentiles), and high (90th percentile) levels of soil PMN were selected to further study the effects of POM on soil N mineralization by quantifying the net N mineralization in original soils and soils from which POM was removed. Both soil POM carbon (POM-C) and N (POM-N) contents were 45.8% and 55.8% higher under the RR rotation compared to the CR rotation, respectively. The PMN contents were highly correlated with the POM contents. The PMN and microbial biomass N (MBN) contents concurrently and significantly decreased when POM was removed. The reduction rate of PMN was positively correlated with changes in MBN after the removal of POM. The reduction rates of PMN and MBN after POM removal are lower under RR rotations (38.0% and 16.3%, respectively) than CR rotations (45.6% and 19.5%, respectively). Furthermore, infrared spectroscopy indicated that compounds with low-bioavailability accumulated (e.g., aromatic recalcitrant materials) in the soil POM fraction under the RR rotation but not under the CR rotation. The results of the present study demonstrated that POM plays a vital role in soil N mineralization under different rotation systems. The discrepancy between POM content and composition resulting from different crop rotation systems caused differences in N mineralization in soils.

Light availability affects sex lability in a gynodioecious plant.

PubMed

Varga, Sandra; Kytöviita, Minna-Maarit

2016-11-01

Sex lability (i.e., gender diphasy) in plants is classically linked to the larger resource needs associated with the female sexual function (i.e., seed production) compared to the male function (i.e., pollen production). Sex lability in response to the environment is extensively documented in dioecious species, but has been largely overlooked in gynodioecious plants. Here, we tested whether environmental conditions induce sex lability in the gynodioecious Geranium sylvaticum. We conducted a transplantation experiment in the field where plants with different sex expression were reciprocally transplanted between high light and low light habitats. We measured plants' reproductive output and sex expression over four years. Our results show that sex expression was labile over the study period. The light level at the destination habitat had a significant effect on sexual expression and reproductive output, because plants decreased their reproductive output when transplanted to the low light habitat. Transplantation origin did not affect any parameter measured. This study shows that sex expression in Geranium sylvaticum is labile and related to light availability. Sexually labile plants did not produce more seeds or pollen, and thus, there was no apparent fitness gain in sexually labile individuals. Sex lability in gynodioecious plants may be more common than previously believed because detection of sex lability necessitates data on the same individuals over time, which is rare in sexually dimorphic herbaceous plants. © 2016 Botanical Society of America.

Investigating the distribution and sources of organic matter in surface sediment of Coombabah Lake (Australia) using elemental, isotopic and fatty acid biomarkers

NASA Astrophysics Data System (ADS)

Dunn, R. J. K.; Welsh, D. T.; Teasdale, P. R.; Lee, S. Y.; Lemckert, C. J.; Meziane, T.

2008-10-01

contribution of organic matter from shoreline mangroves was confirmed by the presence of LCFAs and 18:2 ω6 and 18:3 ω3, which are markers for mangroves in this ecosystem. BAFAs were identified in increased proportions in sediments adjacent to urban developments and dominated by mud. Grain size was identified as a dominant factor in the fatty acid compositions and contributing values to FAME pool. Spatial patterns of C/N ratios, δ13C and δ15N values, and fatty acid biomarker contributions illustrated that there is a greater contribution of autochthonous and labile organic matter to the sedimentary organic matter pool in the northern (marine entrance) sediments compared to the more allochthonous sourced organic matter of the southern region of the lake. This study details the distribution and sources of organic matter within Coombabah Lake and illustrates the usefulness of a multiple biomarker approach in discriminating organic matter sources within estuarine environments.

The response of soil carbon storage and microbially mediated carbon turnover to simulated climatic disturbance in a northern peatland forest. Revisiting the concept of soil organic matter recalcitrance

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

Kostka, Joel

The goal of this project was to investigate changes in the structure of dissolved and solid phase organic matter, the production of CO 2 and CH 4, and the composition of decomposer microbial communities in response to the climatic forcing of environmental processes that determine the balance between carbon gas production versus storage and sequestration in peatlands. Cutting-edge analytical chemistry and next generation sequencing of microbial genes were been applied to habitats at the Marcell Experimental Forest (MEF), where the US DOE’s Oak Ridge National Laboratory and the USDA Forest Service are constructing a large-scale ecosystem study entitled, “Spruce andmore » Peatland Responses Under Climatic and Environmental Change”(SPRUCE). Our study represented a comprehensive characterization of the sources, transformation, and decomposition of organic matter in the S1 bog at MEF. Multiple lines of evidence point to distinct, vertical zones of organic matter transformation: 1) the acrotelm consisting of living mosses, root material, and newly formed litter (0-30 cm), 2) the mesotelm, a mid-depth transition zone (30-75 cm) characterized by labile organic C compounds and intense decomposition, and 3) the underlying catotelm (below 75cm) characterized by refractory organic compounds as well as relatively low decomposition rates. These zones are in part defined by physical changes in hydraulic conductivity and water table depth. O-alkyl-C, which represents the carbohydrate fraction in the peat, was shown to be an excellent proxy for soil decomposition rates. The carbon cycle in deep peat was shown to be fueled by modern carbon sources further indicating that hydrology and surface vegetation play a role in belowground carbon cycling. We provide the first metagenomic study of an ombrotrophic peat bog, with novel insights into microbial specialization and functions in this unique terrestrial ecosystem. Vertical structuring of microbial communities closely paralleled

Deformation behaviors of peat with influence of organic matter.

PubMed

Yang, Min; Liu, Kan

2016-01-01

Peat is a kind of special material rich in organic matter. Because of the high content of organic matter, it shows different deformation behaviors from conventional geotechnical materials. Peat grain has a non-negligible compressibility due to the presence of organic matter. Biogas can generate from peat and can be trapped in form of gas bubbles. Considering the natural properties of peat, a special three-phase composition of peat is described which indicates the existence of organic matter and gas bubbles in peat. A stress-strain-time model is proposed for the compression of organic matter, and the surface tension effect is considered in the compression model of gas bubbles. Finally, a mathematical model has been developed to simulate the deformation behavior of peat considering the compressibility of organic matter and entrapped gas bubbles. The deformation process is the coupling of volume variation of organic matter, gas bubbles and water drainage. The proposed model is used to simulate a series of peat laboratory oedometer tests, and the model can well capture the test results with reasonable model parameters. Effects of model parameters on deformation of peat are also analyzed.

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.

Isolation and chemical characterization of dissolved and colloidal organic matter

USGS Publications Warehouse

Aiken, G.; Leenheer, J.

1993-01-01

Commonly used techniques for the concentration and isolation of organic matter from water, such as preparative chromatography, ultrafiltration and reverse osmosis, and the methods used to analyze the organic matter obtained by these methods are reviewed. The development of methods to obtain organic matter that is associated with fractions of the dissolved organic carbon other than humic substances, such as organic bases, hydrophilic organic acids and colloidal organic matter are discussed. Methods specifically used to study dissolved organic nitrogen and dissolved organic phosphorous are also discussed. -from Authors

Organic matter composition and substrate diversity under elevated CO2 in the Mojave Desert

NASA Astrophysics Data System (ADS)

Tfaily, M. M.; Hess, N. J.; Koyama, A.; Evans, R. D.

2016-12-01

Little is known about how rising atmospheric CO2 concentration will impact long-term plant biomass or the dynamics of soil organic matter (SOM) in arid ecosystems. In this study, we investigated the change in the molecular composition of SOM by high resolution mass spectrometry after 10 years exposure to elevated atmospheric CO2 concentrations at the Nevada Desert FACE Facility. Samples were collected from soil profiles from 0 to 1m in 0.2m increments under the dominant evergreen shrub (Larrea tridentata). The differences in the composition of SOM were more evident in soils close to the surface and consistent with higher bulk soil organic carbon (C) and total nitrogen (N) concentrations under elevated than ambient CO2, reflecting increased net productivity of shrubs under elevated CO2, which could be attributed to increased litter input from above-ground biomass and/or shallow roots, root exudation and/or microbial residues. This was further supported by the significant increase in the abundance of amino sugars-, protein- and carbohydrate-like compounds. These compounds are involved in diverse pathways ranging from sugars and amino-acid metabolism to lipid biosynthesis. This indicates increased activity and metabolism under elevated CO2 and suggests that elevated CO2 have altered microbial C use patterns, reflecting changes in the quality and quantity of soil C inputs. A significant increase in the mineral-bound soil organic C was also observed in the surface soils under elevated CO2. This was accompanied by increased microbial residues as identified by mass spectrometry that supports microbial lipid analysis, and reflecting accelerated microbial turnover under elevated CO2. Fungal neutral lipid fatty acids (NLFA) abundance doubled under elevated CO2. When provided with excess labile compounds, such as root exudates, and with limited supply of nutrients, fungi assimilate the excess labile C and store it as NLFA likely contributing to increased total N

Microbial Community Response to Terrestrially Derived Dissolved Organic Matter in the Coastal Arctic

PubMed Central

Sipler, Rachel E.; Kellogg, Colleen T. E.; Connelly, Tara L.; Roberts, Quinn N.; Yager, Patricia L.; Bronk, Deborah A.

2017-01-01

Warming at nearly twice the global rate, higher than average air temperatures are the new ‘normal’ for Arctic ecosystems. This rise in temperature has triggered hydrological and geochemical changes that increasingly release carbon-rich water into the coastal ocean via increased riverine discharge, coastal erosion, and the thawing of the semi-permanent permafrost ubiquitous in the region. To determine the biogeochemical impacts of terrestrially derived dissolved organic matter (tDOM) on marine ecosystems we compared the nutrient stocks and bacterial communities present under ice-covered and ice-free conditions, assessed the lability of Arctic tDOM to coastal microbial communities from the Chukchi Sea, and identified bacterial taxa that respond to rapid increases in tDOM. Once thought to be predominantly refractory, we found that ∼7% of dissolved organic carbon and ∼38% of dissolved organic nitrogen from tDOM was bioavailable to receiving marine microbial communities on short 4 – 6 day time scales. The addition of tDOM shifted bacterial community structure toward more copiotrophic taxa and away from more oligotrophic taxa. Although no single order was found to respond universally (positively or negatively) to the tDOM addition, this study identified 20 indicator species as possible sentinels for increased tDOM. These data suggest the true ecological impact of tDOM will be widespread across many bacterial taxa and that shifts in coastal microbial community composition should be anticipated. PMID:28649233

Microbial Community Response to Terrestrially Derived Dissolved Organic Matter in the Coastal Arctic.

PubMed

Sipler, Rachel E; Kellogg, Colleen T E; Connelly, Tara L; Roberts, Quinn N; Yager, Patricia L; Bronk, Deborah A

2017-01-01

Warming at nearly twice the global rate, higher than average air temperatures are the new 'normal' for Arctic ecosystems. This rise in temperature has triggered hydrological and geochemical changes that increasingly release carbon-rich water into the coastal ocean via increased riverine discharge, coastal erosion, and the thawing of the semi-permanent permafrost ubiquitous in the region. To determine the biogeochemical impacts of terrestrially derived dissolved organic matter (tDOM) on marine ecosystems we compared the nutrient stocks and bacterial communities present under ice-covered and ice-free conditions, assessed the lability of Arctic tDOM to coastal microbial communities from the Chukchi Sea, and identified bacterial taxa that respond to rapid increases in tDOM. Once thought to be predominantly refractory, we found that ∼7% of dissolved organic carbon and ∼38% of dissolved organic nitrogen from tDOM was bioavailable to receiving marine microbial communities on short 4 - 6 day time scales. The addition of tDOM shifted bacterial community structure toward more copiotrophic taxa and away from more oligotrophic taxa. Although no single order was found to respond universally (positively or negatively) to the tDOM addition, this study identified 20 indicator species as possible sentinels for increased tDOM. These data suggest the true ecological impact of tDOM will be widespread across many bacterial taxa and that shifts in coastal microbial community composition should be anticipated.

The role of labile sulfur compounds in thermochemical sulfate reduction

USGS Publications Warehouse

Amrani, A.; Zhang, T.; Ma, Q.; Ellis, G.S.; Tang, Y.

2008-01-01

The reduction of sulfate to sulfide coupled with the oxidation of hydrocarbons to carbon dioxide, commonly referred to as thermochemical sulfate reduction (TSR), is an important abiotic alteration process that most commonly occurs in hot carbonate petroleum reservoirs. In the present study we focus on the role that organic labile sulfur compounds play in increasing the rate of TSR. A series of gold-tube hydrous pyrolysis experiments were conducted with n-octane and CaSO4 in the presence of reduced sulfur (e.g. H2S, S??, organic S) at temperatures of 330 and 356 ??C under a constant confining pressure. The in-situ pH was buffered to 3.5 (???6.3 at room temperature) with talc and silica. For comparison, three types of oil with different total S and labile S contents were reacted under similar conditions. The results show that the initial presence of organic or inorganic sulfur compounds increases the rate of TSR. However, organic sulfur compounds, such as 1-pentanethiol or diethyldisulfide, were significantly more effective in increasing the rate of TSR than H2S or elemental sulfur (on a mole S basis). The increase in rate is achieved at relatively low concentrations of 1-pentanethiol, less than 1 wt% of the total n-octane, which is comparable to the concentration of organic S that is common in many oils (???0.3 wt%). We examined several potential reaction mechanisms to explain the observed reactivity of organic LSC. First, the release of H2S from the thermal degradation of thiols was discounted as an important mechanism due to the significantly greater reactivity of thiol compared to an equivalent amount of H2S. Second, we considered the generation of olefines in association with the elimination of H2S during thermal degradation of thiols because olefines are much more reactive than n-alkanes during TSR. In our experiments, olefines increased the rate of TSR, but were less effective than 1-pentanethiol and other organic LSC. Third, the thermal decomposition of

The role of labile sulfur compounds in thermochemical sulfate reduction

NASA Astrophysics Data System (ADS)

Amrani, Alon; Zhang, Tongwei; Ma, Qisheng; Ellis, Geoffrey S.; Tang, Yongchun

2008-06-01

The reduction of sulfate to sulfide coupled with the oxidation of hydrocarbons to carbon dioxide, commonly referred to as thermochemical sulfate reduction (TSR), is an important abiotic alteration process that most commonly occurs in hot carbonate petroleum reservoirs. In the present study we focus on the role that organic labile sulfur compounds play in increasing the rate of TSR. A series of gold-tube hydrous pyrolysis experiments were conducted with n-octane and CaSO4 in the presence of reduced sulfur (e.g. H2S, S°, organic S) at temperatures of 330 and 356 °C under a constant confining pressure. The in-situ pH was buffered to 3.5 (∼6.3 at room temperature) with talc and silica. For comparison, three types of oil with different total S and labile S contents were reacted under similar conditions. The results show that the initial presence of organic or inorganic sulfur compounds increases the rate of TSR. However, organic sulfur compounds, such as 1-pentanethiol or diethyldisulfide, were significantly more effective in increasing the rate of TSR than H2S or elemental sulfur (on a mole S basis). The increase in rate is achieved at relatively low concentrations of 1-pentanethiol, less than 1 wt% of the total n-octane, which is comparable to the concentration of organic S that is common in many oils (∼0.3 wt%). We examined several potential reaction mechanisms to explain the observed reactivity of organic LSC. First, the release of H2S from the thermal degradation of thiols was discounted as an important mechanism due to the significantly greater reactivity of thiol compared to an equivalent amount of H2S. Second, we considered the generation of olefines in association with the elimination of H2S during thermal degradation of thiols because olefines are much more reactive than n-alkanes during TSR. In our experiments, olefines increased the rate of TSR, but were less effective than 1-pentanethiol and other organic LSC. Third, the thermal decomposition of

Light and Heavy Fractions of Soil Organic Matter in Response to Climate Warming and Increased Precipitation in a Temperate Steppe

PubMed Central

Song, Bing; Niu, Shuli; Zhang, Zhe; Yang, Haijun; Li, Linghao; Wan, Shiqiang

2012-01-01

Soil is one of the most important carbon (C) and nitrogen (N) pools and plays a crucial role in ecosystem C and N cycling. Climate change profoundly affects soil C and N storage via changing C and N inputs and outputs. However, the influences of climate warming and changing precipitation regime on labile and recalcitrant fractions of soil organic C and N remain unclear. Here, we investigated soil labile and recalcitrant C and N under 6 years' treatments of experimental warming and increased precipitation in a temperate steppe in Northern China. We measured soil light fraction C (LFC) and N (LFN), microbial biomass C (MBC) and N (MBN), dissolved organic C (DOC) and heavy fraction C (HFC) and N (HFN). The results showed that increased precipitation significantly stimulated soil LFC and LFN by 16.1% and 18.5%, respectively, and increased LFC∶HFC ratio and LFN∶HFN ratio, suggesting that increased precipitation transferred more soil organic carbon into the quick-decayed carbon pool. Experimental warming reduced soil labile C (LFC, MBC, and DOC). In contrast, soil heavy fraction C and N, and total C and N were not significantly impacted by increased precipitation or warming. Soil labile C significantly correlated with gross ecosystem productivity, ecosystem respiration and soil respiration, but not with soil moisture and temperature, suggesting that biotic processes rather than abiotic factors determine variations in soil labile C. Our results indicate that certain soil carbon fraction is sensitive to climate change in the temperate steppe, which may in turn impact ecosystem carbon fluxes in response and feedback to climate change. PMID:22479373

Metal Ion Speciation and Dissolved Organic Matter Composition in Soil Solutions

NASA Astrophysics Data System (ADS)

Benedetti, M. F.; Ren, Z. L.; Bravin, M.; Tella, M.; Dai, J.

2014-12-01

Knowledge of the speciation of heavy metals and the role of dissolved organic matter (DOM) in soil solution is a key to understand metal mobility and ecotoxicity. In this study, soil column-Donnan membrane technique (SC-DMT) was used to measure metal speciation of Cd, Cu, Ni, Pb, and Zn in eighteen soil solutions, covering a wide range of metal sources and concentrations. DOM composition in these soil solutions was also determined. Our results show that in soil solution Pb and Cu are dominant in complex form, whereas Cd, Ni and Zn mainly exist as free ions; for the whole range of soil solutions, only 26.2% of DOM is reactive and consists mainly of fulvic acid (FA). The metal speciation measured by SC-DMT was compared to the predicted ones obtained via the NICA-Donnan model using the measured FA concentrations. The free ion concentrations predicted by speciation modelling were in good agreement with the measurements. Diffusive gradients in thin-films gels (DGT) were also performed to quantify the labile metal species in the fluxes from solid phase to solution in fourteen soils. The concentrations of metal species detected by DGT were compared with the free ion concentrations measured by DMT and the maximum concentrations calculated based on the predicted metal speciation in SC-DMT soil solutions. It is concluded that both inorganic species and a fraction of FA bound species account for the amount of labile metals measured by DGT, consistent with the dynamic features of this technique. The comparisons between measurements using analytical techniques and mechanistic model predictions provided mutual validation in their performance. Moreover, we show that to make accurate modelling of metal speciation in soil solutions, the knowledge of DOM composition is the crucial information, especially for Cu; like in previous studies the modelling of Pb speciation is not optimal and an updated of Pb generic binding parameters is required to reduce model prediction uncertainties.

Protective Effect of Active Immunization with Purified Escherichia coli Heat-Labile Enterotoxin in Rats

PubMed Central

Klipstein, Frederick A.; Engert, Richard F.

1979-01-01

The protective effect of active immunization by different routes with a purified preparation of the polymyxin-release form of Escherichia coli heat-labile toxin was evaluated in rats. Immunized animals were challenged by placing toxin into ligated ileal loops at dosages which produced either 50% or the maximum secretory response in unimmunized rats. Immunization exclusively by the parenteral route yielded significant protection. Rats were also protected when parenteral priming was followed by boosting given either directly into the duodenum or perorally 2 h after intragastric cimetidine, but not when the peroral boosts were given with bicarbonate. Immunization administered entirely by the peroral route with cimetidine yielded protection but only when the immunizing dosage was fivefold greater than that found effective in the parenteral-peroral approach. Rats immunized exclusively by the parenteral route and those boosted perorally with cimetidine were also tested, and found to be protected, against challenge with viable organisms of strains that produce either heat-labile toxin alone or both heat-labile and heat-stable toxin, but they were not protected against a strain which produces just heat-stable toxin. Geometric mean serum antibody titers were increased by 16-fold or more over control values in those groups of rats in which protection was achieved, with the exception of those immunized exclusively by the peroral route. These observations demonstrate that (i) active immunization with purified E. coli heat-labile toxin results in significant protection against both this toxin as well as viable organisms which produce it, but not against viable strains which produce heat-stable toxin only, and (ii) concomitant ablation of gastric secretion by the use of cimetidine renders the peroral route of immunization effective. They suggest that prophylactic immunization against diarrheal disease caused by heat-labile toxin-producing strains of E. coli may be feasible in

Biologically Active Organic Matter in Soils of European Russia

NASA Astrophysics Data System (ADS)

Semenov, V. M.; Kogut, B. M.; Zinyakova, N. B.; Masyutenko, N. P.; Malyukova, L. S.; Lebedeva, T. N.; Tulina, A. S.

2018-04-01

Experimental and literature data on the contents and stocks of active organic matter in 200 soil samples from the forest-tundra, southern-taiga, deciduous-forest, forest-steppe, dry-steppe, semidesert, and subtropical zones have been generalized. Natural lands, agrocenoses, treatments of long-term field experiments (bare fallow, unfertilized and fertilized crop rotations, perennial plantations), and different layers of soil profile are presented. Sphagnum peat and humus-peat soil in the tundra and forest-tundra zones are characterized by a very high content of active organic matter (300-600 mg C/100 g). Among the zonal soils, the content of active organic matter increases from the medium (75-150 mg C/100 g) to the high (150-300 mg C/100 g) level when going from soddy-podzolic soil to gray forest and dark-gray forest soils and then to leached chernozem. In the series from typical chernozem to ordinary and southern chernozem and chestnut and brown semidesert soils, a decrease in the content of active organic matter to the low (35-75 mg C/100 g) and very low (<35 mg C/100 g) levels is observed. Acid brown forest soil in the subtropical zone is characterized by a medium supply with active organic matter. Most arable soils are mainly characterized by low or very low contents of active organic matter. In the upper layers of soils, active organic matter makes up 1.2-11.1% of total Corg. The profile distribution of active organic matter in the studied soils coincides with that of Corg: their contents appreciably decrease with depth, except for brown semidesert soil. The stocks of active organic matter vary from 0.4 to 5.4 t/ha in the layer of 0-20 cm and from 1.0 to 12.4/ha in the layer of 0-50 cm of different soil types.

Testing the root-priming of soil organic matter decomposition using the isotopic signature of fossil fuel CO2

NASA Astrophysics Data System (ADS)

Bradley, Robert; Paterson, Eric; Chapman, Steve; Thornton, Barry; Sim, Allan

2013-04-01

Plant roots provide various forms of soil labile carbon (i.e., rhizodeposition), which stimulate the growth of heterotrophic bacteria in the rhizosphere. This, in turn, provides a food source for phagotrophic protozoa and other bacterivores, whose carbon:nutrient ratios are generally higher than those of their food source. In order to maintain their stoichiometric composition, bacterivores release their extra nutrients into the rhizosphere, where they may be absorbed by plant roots. Thus, rhizodeposition should reduce carbon limitation, but increase nutrient demand, of the soil microbial biomass. We hypothesized that this shift towards nutrient deficiency would stimulate the production of microbial enzymes that depolymerise soil organic matter into microbial available forms. In other words, roots should stimulate the decomposition of soil organic matter. We report on experiment where we tested such a "root-priming" effect using 3 contrasting plant species (Achillea millefolium, Lolium perenne, Trifolium repens). An agricultural soil, with a delta-13C value of approximately -14 ‰ , was transferred into 30 pots and planted with seeds of each species. A ring was inserted in the middle of each pot, and no seeds were planted within the ring. Plants were grown in a growth chamber designed to deliver 13C-depleted air. The resulting plant biomass had a delta-13C value of approximately -52 ‰ . On 7 occasions during the growth trial, pots were sampled for the flux and delta-13C value of soil CO2. Using similar data from control pots without plants, we compared the expected vs. observed contributions of CO2 from roots and soil organic matter. Results from this study revealed a negative root-priming effect for all three species. We discuss the experimental conditions that could have led to this observation, as well as the novelty and potential of our experimental protocol.

Non-Destructive High-Resolution Organic Matter Record on Lake Sediment using Steady-State Solid Phase Fluorescence: Organic Matter Quality and Quantity Assessment.

NASA Astrophysics Data System (ADS)

Quiers, M.; Perrette, Y.; Etienne, D.; Develle, A. L.; Jacq, K.

2017-12-01

The use of organic proxies increases in paleoenvironmental reconstructions from natural archives. Major advances have been achieved by the development of new highly informative molecular proxies usually linked to specific compounds. While studies focused on targeted compounds, offering a high information degree, advances on bulk organic matter are limited. However, this bulk is the main contributor to carbon cycle and has been shown to be a driver of many mineral or organic compounds transfer and record. Development of target proxies need complementary information on bulk organic matter to understand biases link to controlling factors or analytical methods, and provide a robust interpretation. Fluorescence methods have often been employed to characterize and quantify organic matter. However, these technics are mainly developed for liquid samples, inducing material and resolution loss when working on natural archives (either stalagmite or sediments). High-resolution solid phase fluorescence (SPF) was developed on speleothems. This method allows now to analyse organic matter quality and quantity if procedure to constrain the optical density are adopted. In fact, a calibration method using liquid phase fluorescence (LPF) was developed for speleothem, allowing to quantify organic carbon at high-resolution. We report here an application of such a procedure SPF/LPF measurements on lake sediments. In order to avoid sediment matrix effects on the fluorescence signal, a calibration using LPF measurements was realised. First results using this method provided organic matter quality record of different organic matter compounds (humic-like, protein-like and chlorophylle-like compounds) at high resolution for the sediment core. High resolution organic matter fluxes are obtained in a second time, applying pragmatic chemometrics model (non linear models, partial least square models) on high resolution fluorescence data. SPF method can be considered as a promising tool for high

Native soil organic matter conditions the response of microbial communities to organic inputs with different stability

NASA Astrophysics Data System (ADS)

Yanardaǧ, Ibrahim H.; Zornoza, Raúl; Bastida, Felipe; Büyükkiliç-Yanardaǧ, Asuman; Acosta, Jose A.; García, Carlos; Faz, Ángel; Mermut, Ahmet R.

2017-04-01

The response of soil microbial communities from soils with different soil organic matter (SOM) content to organic inputs with different stability is still poorly understood. Thus, an incubation experiment was designed to study how the addition of pig slurry (PS), its manure (M) and its biochar (BC) affect soil microbial community and activity in three soils differing in SOM content (Regosol, Luvisol and Kastanozem). The evolution of different C and N fractions, microbial biomass C and N, enzyme activities and microbial community structure by the use of phospholipid fatty acid (PLFA) analysis was assessed for 60 days. Results showed that the different amendments had different effect on microbial properties depending on the soil type. The addition of M caused the highest increase in all microbial properties in the three soils, followed by PS. These changes were more intense in the soil with the lowest SOM (Regosol). The addition of M and PS caused changes in the microbial community structure in all soils, which were more related to the presence of available sources of N than to the labile fractions of C. The addition of BC was followed by increases in the proportions of fungi and Gram positive bacteria in the Regosol, while enhanced the proportion of actinobacteria in all soil types, related to increments in pH and soil C recalcitrance. Thus, native SOM determined the response of microbial communities to external inputs with different stability, soils with low SOM being more prone to increase microbial biomass and activity and change microbial community structure.

Organic matter in hydrothermal metal ores and hydrothermal fluids

USGS Publications Warehouse

Orem, W.H.; Spiker, E. C.; Kotra, R.K.

1990-01-01

Massive polymetallic sulfides are currently being deposited around active submarine hydrothermal vents associated with spreading centers. Chemoautolithotrophic bacteria are responsible for the high production of organic matter also associated with modern submarine hydrothermal activity. Thus, there is a significant potential for organic matter/metal interactions in these systems. We have studied modern and ancient hydrothermal metal ores and modern hydrothermal fluids in order to establish the amounts and origin of the organic matter associated with the metal ores. Twenty-six samples from modern and ancient hydrothermal systems were surveyed for their total organic C contents. Organic C values ranged from 0.01% to nearly 4.0% in these samples. Metal ores from modern and ancient sediment-covered hydrothermal systems had higher organic C values than those from modern and ancient hydrothermal systems lacking appreciable sedimentary cover. One massive pyrite sample from the Galapagos spreading center (3% organic C) had stable isotope values of -27.4% (??13C) and 2.1% (??15N), similar to those in benthic siphonophors from active vents and distinct from seep sea sedimentary organic matter. This result coupled with other analyses (e.g. 13C NMR, pyrolysis/GC, SEM) of this and other samples suggests that much of the organic matter may originate from chemoautolithotrophic bacteria at the vents. However, the organic matter in hydrothermal metal ores from sediment covered vents probably arises from complex sedimentary organic matter by hydrothermal pyrolysis. The dissolved organic C concentrations of hydrothermal fluids from one site (Juan de Fuca Ridge) were found to be the same as that of background seawater. This result may indicate that dissolved organic C is effectively scavenged from hydrothermal fluids by biological activity or by co-precipitation with metal ores. ?? 1990.

Characterization of labile organic carbon in coastal wetland soils of the Mississippi River deltaic plain: relationships to carbon functionalities.

PubMed

Dodla, Syam K; Wang, Jim J; Delaune, Ronald D

2012-10-01

Adequate characterization of labile organic carbon (LOC) is essential to the understanding of C cycling in soil. There has been very little evaluation about the nature of LOC characterizations in coastal wetlands, where soils are constantly influenced by different redox fluctuations and salt water intrusions. In this study, we characterized and compared LOC fractions in coastal wetland soils of the Mississippi River deltaic plain using four different methods including 1) aerobically mineralizable C (AMC), 2) cold water extractable C (CWEC), 3) hot water extractable C (HWEC), and 4) salt extractable C (SEC), as well as acid hydrolysable C (AHC) which includes both labile and slowly degradable organic C. Molecular organic C functional groups of these wetland soils were characterized by (13)C solid-state nuclear magnetic resonance (NMR). The LOC and AHC increased with soil organic C (SOC) regardless of wetland soil type. The LOC estimates by four different methods were positively and significantly linearly related to each other (R(2)=0.62-0.84) and with AHC (R(2)=0.47-0.71). The various LOC fractions accounted for ≤4.3% of SOC whereas AHC fraction represented 16-49% of SOC. AMC was influenced positively by O/N-alkyl and carboxyl C but negatively by alkyl C, whereas CWEC and SEC fractions were influenced only positively by carboxyl C but negatively by alkyl C in SOC. On the other hand, HWEC fraction was found to be only influenced positively by carbonyl C, and AHC positively by O/N-alkyl and alkyl C but negatively by aromatic C groups in SOC. Overall these relations suggested different contributions of various molecular organic C moieties to LOC in these wetlands from those often found for upland soils. The presence of more than 50% non-acid hydrolysable C suggested the dominance of relatively stable SOC pool that would be sequestered in these Mississippi River deltaic plain coastal wetland soils. The results have important implications to the understanding of the

Interspecific variations in mangrove leaf litter decomposition are related to labile nitrogenous compounds

NASA Astrophysics Data System (ADS)

Nordhaus, Inga; Salewski, Tabea; Jennerjahn, Tim C.

2017-06-01

Mangrove leaves form a large pool of carbon, nitrogen and energy that is a major driver of element cycles and detrital food webs inside mangrove forests as well as in adjacent coastal waters. However, there are large gaps in knowledge on the transformation pathways and ultimate fate of leaf nitrogen. Therefore, the main objective of this study was to determine the amount and composition of nitrogenous organic matter and possible species-specific differences during the decomposition of mangrove leaf litter. For that purpose a three month decomposition experiment with litterbags was conducted using leaves of Aegiceras corniculatum, Avicennia alba, Ceriops decandra, Rhizophora apiculata, and Sonneratia caseolaris in the mangrove forest of the Segara Anakan Lagoon, Java, Indonesia. Detrital leaves were analyzed for bulk carbon and total nitrogen (N), stable carbon and nitrogen isotope composition (δ13C, δ15N), total hydrolyzable amino acids (THAA) and total hydrolyzable hexosamines (THHA). Decomposition rates (k d-1) were highest and tM50 values (when 50% of the original mass had been degraded) lowest in S. caseolaris (k = 0.0382 d-1; tM50 = 18 days), followed by A. alba, C. decandra, A. corniculatum, and R. apiculata (k = 0.0098 d-1; tM50 = 71 days). The biochemical composition of detrital leaves differed significantly among species and over time. S. caseolaris and A. alba had higher concentrations of N, THAA and THHA and a lower C/N ratio than the other three species. For most of the species concentrations of N, THAA and THHA increased during decomposition. The hexosamine galactosamine, indicative of bacterial cell walls, was first found in leaves after 5-7 days of decomposition and increased afterwards. Our findings suggest an increasing, but species-specific varying, portion of labile nitrogenous OM and total N in decomposing leaves over time that is partly related to the activity of leaf-colonizing bacteria. Despite a higher relative nitrogen content in the

The influence of algal organic matter produced by Microcystis aeruginosa on coagulation-ultrafiltration treatment of natural organic matter.

PubMed

Xu, Jie; Zhao, Yanxia; Gao, Baoyu; Han, Songlin; Zhao, Qian; Liu, Xiaoli

2018-04-01

Cyanobacterial bloom causes the release of algal organic matter (AOM), which inevitably affects the treatment processes of natural organic matter (NOM). This study works on treating micro-polluted surface water (SW) by emerging coagulant, namely titanium sulfate (Ti(SO 4 ) 2 ), followed by Low Pressure Ultrafiltration (LPUF) technology. In particular, we explored the respective influence of extracellular organic matter (EOM) and intracellular organic matter (IOM) on synergetic EOM-NOM/IOM-NOM removal, functional mechanisms and subsequent filtration performance. Results show that the IOM inclusion in surface water body facilitated synergic IOM-NOM composite pollutants removal by Ti(SO 4 ) 2 , wherein loosely-aggregated flocs were produced, resulting in floc cake layer with rich porosity and permeability during LPUF. On the contrary, the surface water invaded by EOM pollutants increased Ti(SO 4 ) 2 coagulation burden, with substantially deteriorated both UV 254 -represented and dissolved organic matter (DOC) removal. Corresponded with the weak Ti(SO 4 ) 2 coagulation for EOM-NOM removal was the resultant serious membrane fouling during LPUF procedure, wherein dense cake layer was formed due to the compact structure of flocs. Although the IOM enhanced NOM removal with reduced Ti(SO 4 ) 2 dose and yielded mitigated membrane fouling, larger percentage of irreversible fouling was seen than NOM and EOM-NOM cases, which was most likely due to the substances with small molecular weight, such as microcystin, adhering in membrane pores. This research would provide theoretical basis for dose selection and process design during AOM-NOM water treatment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Influence of Soil Organic Matter Stabilization Mechanisms on Temperature Sensitivity of Soil Respiration

NASA Astrophysics Data System (ADS)

Gillabel, J.; de Gryze, S.; Six, J.; Merckx, R.

2007-12-01

Knowledge on the sensitivity of soil organic matter (SOM) respiration to changes in temperature is crucial for predicting future impacts of climate change on soil C stocks. Temperature sensitivity of respiration is determined by the chemical structure of the compound to be decomposed and by the availability of the organic matter for decomposers. Biochemically recalcitrant SOM has a higher temperature sensitivity than biochemically labile SOM. However, it is hypothesized that the stabilization of SOM by interaction with the soil matrix could be an important attenuating control on temperature sensitivity. We investigated the effect of different SOM stabilization mechanisms on temperature sensitivity of SOM respiration. Two main mechanisms were considered: chemical interactions of SOM with clay and silt particles, and physical protection inside aggregates. Soil samples from an agricultural silt loam soil were fractionated by wet-sieving into macroaggregates, microaggregates and silt+clay fractions. SOM stabilization in the silt+clay fraction occurs mainly chemically, whereas in aggregates physical protection of SOM is more important. Samples of each fraction and of bulk soil were incubated at two temperatures (20°C and 30°C) for one month. After 2% of total soil carbon was respired, temperature sensitivity was determined for respiration of the next 0.5% of total soil carbon. This was done by calculating a Q10 value as the ratio of the times needed at each temperature to respire that fraction of the soil C. This method allows determination of temperature sensitivity independent of C quality. Calculated Q10 values decreased in the order bulk soil > macroaggregates > microaggregates > silt+clay, with the difference between macroaggregate Q10 and silt+clay Q10 being the only significant difference. These results indicate that protection of SOM attenuates temperature sensitivity, with chemical protection (silt+clay) having a larger effect than physical protection

Self-organization of dissolved organic matter to micelle-like microparticles in river water.

PubMed

Kerner, Martin; Hohenberg, Heinz; Ertl, Siegmund; Reckermann, Marcus; Spitzy, Alejandro

2003-03-13

In aquatic systems, the concept of the 'microbial loop' is invoked to describe the conversion of dissolved organic matter to particulate organic matter by bacteria. This process mediates the transfer of energy and matter from dissolved organic matter to higher trophic levels, and therefore controls (together with primary production) the productivity of aquatic systems. Here we report experiments on laboratory incubations of sterile filtered river water in which we find that up to 25% of the dissolved organic carbon (DOC) aggregates abiotically to particles of diameter 0.4-0.8 micrometres, at rates similar to bacterial growth. Diffusion drives aggregation of low- to high-molecular-mass DOC and further to larger micelle-like microparticles. The chemical composition of these microparticles suggests their potential use as food by planktonic bacterivores. This pathway is apparent from differences in the stable carbon isotope compositions of picoplankton and the microparticles. A large fraction of dissolved organic matter might therefore be channelled through microparticles directly to higher trophic levels--bypassing the microbial loop--suggesting that current concepts of carbon conversion in aquatic systems require revision.

Performance of sulphate- and selenium-reducing biochemical reactors using different ratios of labile to recalcitrant organic materials.

PubMed

Mirjafari, Parissa; Baldwin, Susan A

2015-01-01

Successful operation of sulphate-reducing bioreactors using complex organic materials depends on providing a balance between more easily degrading material that achieves reasonable kinetics and low hydraulic retention times, and more slowly decomposing material that sustains performance in the long term. In this study, two organic mixtures containing the same ingredients typical of bioreactors used at mine sites (woodchips, hay and cow manure) but with different ratios of wood (recalcitrant) to hay (labile) were tested in six continuous flow bioreactors treating synthetic mine-affected water containing 600 mg/L of sulphate and 15 μg/L of selenium. The reactors were operated for short (5-6 months) and long (435-450 days) periods of time at the same hydraulic retention time of 15 days. There were no differences in the performance of the bioreactors in terms of sulphate-reduction over the short term, but the wood-rich bioreactors experienced variable and sometimes unreliable sulphate-reduction over the long term. Presence of more hay in the organic mixture was able to better sustain reliable performance. Production of dissolved organic compounds due to biodegradation within the bioreactors was detected for the first 175-230 days, after which their depletion coincided with a crash phase observed in the wood-rich bioreactors only.

Understanding groundwater, surface water, and hyporheic zone biogeochemical processes in a Chalk catchment using fluorescence properties of dissolved and colloidal organic matter

NASA Astrophysics Data System (ADS)

Lapworth, D. J.; Gooddy, D. C.; Allen, D.; Old, G. H.

2009-09-01

Understanding groundwater-surface water (GW-SW) interaction in Chalk catchments is complicated by the degree of geological heterogeneity. At this study site, in southern United Kingdom, alluvial deposits in the riparian zone can be considered as a patchwork of varying grades and types with an equally varied lateral connectivity. Some display good connection with the river system and others good connection with the groundwater system and, by definition, poorer connectivity with the surface water. By coupling tangential flow fractionation (TFF) with fluorescence analysis we were able to characterize the organic matter in the river and hyporheic zone. There is a significant proportion of particulate and colloidal fluorescent organic matter (FOM) within the river system and at depth within the gravels beneath the river channel. At depth in the hyporheic zone, the surface water inputs are dampened by mixing with deeper groundwater FOM. The shallow (0-0.5 m below river bed) hyporheic zone is highly dynamic as a result of changing surface water inputs from upstream processes. Labile C in the form of protein-like FOM appears to be attenuated preferentially compared to fulvic-like fluorescence in the hyporheic zone compared to the adjacent gravel and sand deposits. These preliminary findings have important implications for understanding nutrient and trace element mobility and attenuation within the groundwater, surface water, and hyporheic zone of permeable Chalk catchments. Fluorescence analysis of dissolved organic matter has been shown to be a useful environmental tracer that can be used in conjunction with other methods to understand GW-SW processes within a permeable Chalk catchment.

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.

Matrix protected organic matter in a river dominated margin: A possible mechanism to sequester terrestrial organic matter?

NASA Astrophysics Data System (ADS)

Mead, Ralph N.; Goñi, Miguel A.

2008-06-01

The provenance of organic matter in surface sediments from the northern Gulf of Mexico was investigated by analyzing the compositions of lipid biomarkers ( n-alkanes, fatty acids, sterols) liberated after a series of chemical treatments designed to remove different organo-mineral matrix associations (i.e. freely extractable, base-hydrolyzable, unhydrolyzable). Bulk analyses of the organic matter (carbon content, carbon:nitrogen ratios, stable and radiocarbon isotopic analyses) were also performed on the intact sediments and their non-hydrolyzable, demineralized residue. We found recognizable lipids from distinct sources, including terrestrial vascular plants, bacteria and marine algae and zooplankton, within each of the isolated fractions. Based on the lipid signatures and bulk compositions, the organic matter within the unhydrolyzable fractions appeared to be the most diagenetically altered, was the oldest in age, and had the highest abundance of terrigenous lipids. In contrast, the base-hydrolyzable fraction was the most diagentically unaltered, had the youngest ages and was most enriched in N and marine lipids. Our results indicate that fresh, autochthonous organic matter is the most important contributor to base-hydrolyzable lipids, whereas highly altered allochthonous sources appear to be predominant source of unhydrolyzable lipids in the surface sediments from the Atchafalaya River shelf. Overall, the lipid biomarker signatures of intact sediments were biased towards the autochthonous source because many of the organic compounds indicative of degraded, terrigenous sources were protected from extraction and saponification by organo-mineral matrices. It is only after these protective matrices were removed by treatment with HCl and HF that these compounds became evident.

Measuring organic matter in Everglades wetlands and the Everglades Agricultural Area

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

Wright, Alan L.; Hanlon, Edward A.

Here, organic matter is a complex material that represents the long-term decay products from plants and other organisms in the soil. When organic matter is allowed to build up in a soil, the soil color at the surface usually turns a darker color, often with a red or brown hue. Typically in Florida mineral soils, organic matter content is quite low, within the range of 1 to 5%. However, in some soils that remain flooded for most of the year, organic matter can build up with time and actually become the soil. Such is the case for the organic soils,more » or histosols, found in southern Florida. These organic soils comprise much of the Water Conservation Areas, Everglades National Park (ENP), Big Cypress Basin, and the Everglades Agricultural Area (EAA). It is important to document organic matter accumulation in the Everglades to gauge the effectiveness of wetland creation and succession. For the EAA, the drained soils lose organic matter due to oxidation, so measurement of the organic matter content of these soils over the course of time indicates the oxidation potential and mineral incorporation from bedrock. Due to the wide diversity of soil types and methods of measuring soil organic matter, there is a need to devise a more universal method applicable to many types of histosols in south Florida. The intent of this publication is: 1.To describe a simple laboratory method for determining the organic matter content of the organic soils of southern Florida and demonstrate the importance of using this new procedure for improved accuracy and precision; 2.To utilize this updated laboratory procedure for field sites across Everglades wetlands and the EAA; and 3. To recommend this procedure be used by growers, state and federal agencies, and university and agency researchers dealing with the management of organic soils in southern Florida. Growers can use this improvement to organic matter measurement to keep lab testing costs low while getting a better, more

Mercury dilution by autochthonous organic matter in a fertilized mangrove wetland.

PubMed

Machado, Wilson; Sanders, Christian J; Santos, Isaac R; Sanders, Luciana M; Silva-Filho, Emmanoel V; Luiz-Silva, Wanilson

2016-06-01

A dated sediment core from a highly-fertilized mangrove wetland located in Cubatão (SE Brazil) presented a negative correlation between mercury (Hg) and organic carbon contents. This is an unusual result for a metal with well-known affinity to organic matter. A dilution of Hg concentrations by autochthonous organic matter explained this observation, as revealed by carbon stable isotopes signatures (δ(13)C). Mercury dilution by the predominant mangrove-derived organic matter counterbalanced the positive influences of algal-derived organic matter and clay contents on Hg levels, suggesting that deleterious effects of Hg may be attenuated. Considering the current paradigm on the positive effect of organic matter on Hg concentrations in coastal sediments and the expected increase in mangrove organic matter burial due to natural and anthropogenic stimulations of primary production, predictions on the influences of organic matter on Hg accumulation in mangrove wetlands deserve caution. Copyright © 2016 Elsevier Ltd. All rights reserved.

Transformations in soil organic matter and aggregate stability after conversion of Mediterranean forest to agriculture

NASA Astrophysics Data System (ADS)

Recio Vázquez, Lorena; Almendros, Gonzalo; Carral, Pilar; Knicker, Heike; González Pérez, José Antonio; González Vila, Francisco Javier

2013-04-01

Conversion of forest ecosystems into croplands often leads to severe decrease of the soil organic matter (SOM) levels with the concomitant deterioration of soil structure. The present research focuses on the effects of cultivation on the stability of soil macroaggregates, as well as on the total quantity and quality of SOM. Three representative soils from central Spain (i.e., Petric Calcisol, Cutanic Luvisol and Calcic Vertisol) were sampled. Each site had natural vegetation (NV) dominated either by characteristic Mediterranean forest (dehesa) or cereal crops (CC) under conventional tillage. For each site, three spatial replicates of the NV and CC were sampled. Soil aggregate stability was measured by the wet sieving method. The structural stability index was then calculated as the mass of aggregated soil (>250 μm) remaining after wet sieving, as a percent of total aggregate weight. The analytical characterization of the SOM was carried out after chemical fractionation for quantifying the different organic pools: free organic matter (FOM), humic acids (HA), fulvic acids (FA) and humin (H). Furthermore, whole soil samples pretreated with 10 % HF solution were analyzed by CP-MAS 13C NMR and the purified HA fraction was characterized by elementary analysis, visible and infrared spectroscopies and Py-GC/MS. A marked reduction in the proportion of stable aggregates when the natural ecosystem was converted to agriculture was observed. Values of the structural stability index (%) changed over from 96.2 to 38.1, 95.1 to 83.7 and 98.5 to 60.6 for the Calcisol, Luvisol and Vertisol respectively. Comparatively higher contents of SOM were found in the soils under NV (11.69 to 0.93, 3.29 to 2.72 and 9.51 to 0.79 g C100 g-1soil) even though a quantitative rearrangement of the SOM pools was noticed. In all sites, the relative contribution of the labile C (FOM) to the total SOM content decreased when the forest soils were converted into croplands, whereas the proportion of both

High molecular weight dissolved organic matter enrichment selects for methylotrophs in dilution to extinction cultures

PubMed Central

Sosa, Oscar A; Gifford, Scott M; Repeta, Daniel J; DeLong, Edward F

2015-01-01

The role of bacterioplankton in the cycling of marine dissolved organic matter (DOM) is central to the carbon and energy balance in the ocean, yet there are few model organisms available to investigate the genes, metabolic pathways, and biochemical mechanisms involved in the degradation of this globally important carbon pool. To obtain microbial isolates capable of degrading semi-labile DOM for growth, we conducted dilution to extinction cultivation experiments using seawater enriched with high molecular weight (HMW) DOM. In total, 93 isolates were obtained. Amendments using HMW DOM to increase the dissolved organic carbon concentration 4x (280 μM) or 10x (700 μM) the ocean surface water concentrations yielded positive growth in 4–6% of replicate dilutions, whereas <1% scored positive for growth in non-DOM-amended controls. The majority (71%) of isolates displayed a distinct increase in cell yields when grown in increasing concentrations of HMW DOM. Whole-genome sequencing was used to screen the culture collection for purity and to determine the phylogenetic identity of the isolates. Eleven percent of the isolates belonged to the gammaproteobacteria including Alteromonadales (the SAR92 clade) and Vibrio. Surprisingly, 85% of isolates belonged to the methylotrophic OM43 clade of betaproteobacteria, bacteria thought to metabolically specialize in degrading C1 compounds. Growth of these isolates on methanol confirmed their methylotrophic phenotype. Our results indicate that dilution to extinction cultivation enriched with natural sources of organic substrates has a potential to reveal the previously unsuspected relationships between naturally occurring organic nutrients and the microorganisms that consume them. PMID:25978545

Monitoring changes in soil organic carbon pools, nitrogen, phosphorus, and sulfur under different agricultural management practices in the tropics.

PubMed

Verma, Bibhash C; Datta, Siba Prasad; Rattan, Raj K; Singh, Anil K

2010-12-01

Soil organic matter not only affects sustainability of agricultural ecosystems, but also extremely important in maintaining overall quality of environment as soil contains a significant part of global carbon stock. Hence, we attempted to assess the influence of different tillage and nutrient management practices on various stabilized and active soil organic carbon pools, and their contribution to the extractable nitrogen phosphorus and sulfur. Our study confined to the assessment of impact of agricultural management practices on the soil organic carbon pools and extractable nutrients under three important cropping systems, viz. soybean-wheat, maize-wheat, and rice-wheat. Results indicated that there was marginal improvement in Walkley and Black content in soil under integrated and organic nutrient management treatments in soybean-wheat, maize-wheat, and rice-wheat after completion of four cropping cycles. Improvement in stabilized pools of soil organic carbon (SOC) was not proportional to the applied amount of organic manures. While, labile pools of SOC were increased with the increase in amount of added manures. Apparently, green manure (Sesbania) was more effective in enhancing the lability of SOC as compared to farmyard manure and crop residues. The KMnO(4)-oxidizable SOC proved to be more sensitive and consistent as an index of labile pool of SOC compared to microbial biomass carbon. Under different cropping sequences, labile fractions of soil organic carbon exerted consistent positive effect on the extractable nitrogen, phosphorus, and sulfur in soil.

GROUNDWATER TRANSPORT OF HYDROPHOBIC ORGANIC COMPOUNDS IN THE PRESENCE OF DISSOLVED ORGANIC MATTER

EPA Science Inventory

The effects of dissolved organic matter (DOM) on the transport of hydrophobic organic compounds in soil columns were investigated. Three compounds (naphthalene, phenanthrene and DDT) that spanned three orders of magnitude in water solubility were used. Instead of humic matter, mo...

Organic matter dynamics in a karstic watershed: Example from Santa Fe River, Florida, USA

NASA Astrophysics Data System (ADS)

Jin, J.; Khadka, M. B.; Martin, J. B.; Zimmerman, A. R.

2011-12-01

Organic matter (OM) dynamics in karstic watersheds can involve a range of interactions between organic and inorganic phases of carbon. These interactions include OM remineralization, which will changes its lability, increase dissolved inorganic carbon (DIC) concentrations, reduce pH, and enhance carbonate mineral dissolution. Dissolved organic carbon (DOC) concentrations are elevated in black-water rivers of northern Florida from both allochthonous and autochthonous sources and these rivers flow into and interact with the karstic Floridan Aquifer. One such river, the Santa Fe River, is split into upper confined and lower unconfined watersheds by the Cody Scarp, which represent the erosional edge of a regional confining unit. Water samples were collected from 8 sites across the entire Santa Fe River watershed (SFRW) during 9 sampling trips from December 2009 to May 2011 at flow conditions that ranged from 27 to 39 m3/s, with the highest flow about 45% higher than baseflow. At sites above the Cody Scarp, the river has elevated DOC concentrations, which decrease downstream, while dissolved inorganic carbon (DIC) and δ13C-DIC show opposite trends. At high flow, DOC concentrations progressively decrease downstream from dilution by low-DOC water discharging from the Floridan Aquifer. At low flow, the water chemistry varies little from upstream to downstream, largely because the composition of upstream water becomes similar to that of downstream water. DOC is inversely and linearly correlated with DIC and δ13C-DIC, but the slope of the correlations vary with discharge, with low flow having more negative slopes than high flow. The OM becomes more labile with distance downstream as assessed using two fluorescence indices, biological/autochthonous index (BIX) and humification index (HIX). This increase in lability suggests that DOC is produced in the river, and this production is reflected in a downstream increase in DOC flux regardless of dilution by the influx of low

Opposing effects of different soil organic matter fractions on crop yields.

PubMed

Wood, Stephen A; Sokol, Noah; Bell, Colin W; Bradford, Mark A; Naeem, Shahid; Wallenstein, Matthew D; Palm, Cheryl A

2016-10-01

Soil organic matter is critical to sustainable agriculture because it provides nutrients to crops as it decomposes and increases nutrient- and water-holding capacity when built up. Fast- and slow-cycling fractions of soil organic matter can have different impacts on crop production because fast-cycling fractions rapidly release nutrients for short-term plant growth and slow-cycling fractions bind nutrients that mineralize slowly and build up water-holding capacity. We explored the controls on these fractions in a tropical agroecosystem and their relationship to crop yields. We performed physical fractionation of soil organic matter from 48 farms and plots in western Kenya. We found that fast-cycling, particulate organic matter was positively related to crop yields, but did not have a strong effect, while slower-cycling, mineral-associated organic matter was negatively related to yields. Our finding that slower-cycling organic matter was negatively related to yield points to a need to revise the view that stabilization of organic matter positively impacts food security. Our results support a new paradigm that different soil organic matter fractions are controlled by different mechanisms, potentially leading to different relationships with management outcomes, like crop yield. Effectively managing soils for sustainable agriculture requires quantifying the effects of specific organic matter fractions on these outcomes. © 2016 by the Ecological Society of America.

Quantification of Labile Soil Mercury by Stable Isotope Dilution Techniques

NASA Astrophysics Data System (ADS)

Shetaya, Waleed; Huang, Jen-How; Osterwalder, Stefan; Alewell, Christine

2016-04-01

been applied to estimate the labile pool of mercury in contaminated soils. We performed a series of soil incubations spiked with 196Hg2+aiming at measuring and modelling the progressive assimilation of Hg ions into less labile forms. Soils with a wide range of characteristics are taken for our research purpose, inclusive of Hg concentrations ranging from 0.1 to 390 mg kg-1, pH between 3.5 - 7.5 and total organic carbon (TOC) between 2.5 - 8 %. In parallel, the labile pool of Hg estimated using ID will be compared with that determined using conventional extraction methods, e.g. sequential extraction procedures. These altogether allows us to answer (1) how the E-value of Hg in soils is comparable to those estimated based on selective extraction methods, (2) how the labile Hg correlates with the total soil Hg, soil pH and TOC, and (3) how the solubility of added Hg (e.g. via rainfall) decreased in soils of different properties during aging. The obtained results fills the knowledge gap concerning Hg biogeochemistry in the terrestrial environment and serves as a basis for estimating (and predicting) the risk of soil Hg diffusion from a point source to the adjacent environments.

Defining organic matter quality in sediment systems: a suggested classification scheme

NASA Astrophysics Data System (ADS)

Alderson, Danielle; Evans, Martin; Rothwell, James; Boult, Stephen

2015-04-01

The quantity and quality of the mineral component of sediments is a core focus of sedimentological investigation in terrestrial systems. This is not to say that the organic component of collected sediments is simply ignored; the organic component is often scrutinised, but in some fields in a restricted manner, limited to basic characteristics such as the ratio of organic to mineral content derived from loss on ignition. There is no doubt that this information is useful; however, these types of analysis indicate the quantity of organic matter relative to a particular temporal scale or volume, rather than treating the organic fraction as a separate entity worthy of substantial investigation. The quality of the organic component is being increasingly considered in a number of fields, with molecular, thermal, spectroscopic and bulk methods being used. However, models and theories on organic matter processing in a variety of environmental systems, have been developed without clearly defining organic matter quality, because most results do not depend on an outright measure of quality (Bosatta and Agren, 1999). With approaches and techniques varying between fields, there is a need to consider a more systematic approach to the analysis and definition of organic matter quality. The disparities in the definition of the quality of organic matter, and thus how it may be measured have vital implications for the study of carbon cycling, biogeochemical processing, and ultimately ecosystem structure and function. The quality and quantity of organic matter have an influence on the chemistry and biology of systems and may reveal a wealth of past or contemporary environmental information. In this paper we provide a classification of organic matter quality and examples of potential applications and suitable techniques for the analysis of the main classes of organic matter character. A more consistent approach to organic matter characterisation has the potential to aid understanding of

Correlated microanalysis of cometary organic grains returned by Stardust

NASA Astrophysics Data System (ADS)

de Gregorio, Bradley T.; Stroud, Rhonda M.; Cody, George D.; Nittler, Larry R.; David Kilcoyne, A. L.; Wirick, Sue

2011-09-01

Abstract- Carbonaceous matter in Stardust samples returned from comet 81P/Wild 2 is observed to contain a wide variety of organic functional chemistry. However, some of this chemical variety may be due to contamination or alteration during particle capture in aerogel. We investigated six carbonaceous Stardust samples that had been previously analyzed and six new samples from Stardust Track 80 using correlated transmission electron microscopy (TEM), X-ray absorption near-edge structure spectroscopy (XANES), and secondary ion mass spectroscopy (SIMS). TEM revealed that samples from Track 35 containing abundant aliphatic XANES signatures were predominantly composed of cometary organic matter infilling densified silica aerogel. Aliphatic organic matter from Track 16 was also observed to be soluble in the epoxy embedding medium. The nitrogen-rich samples in this study (from Track 22 and Track 80) both contained metal oxide nanoparticles, and are likely contaminants. Only two types of cometary organic matter appear to be relatively unaltered during particle capture. These are (1) polyaromatic carbonyl-containing organic matter, similar to that observed in insoluble organic matter (IOM) from primitive meteorites, interplanetary dust particles (IDPs), and in other carbonaceous Stardust samples, and (2) highly aromatic refractory organic matter, which primarily constitutes nanoglobule-like features. Anomalous isotopic compositions in some of these samples also confirm their cometary heritage. There also appears to be a significant labile aliphatic component of Wild 2 organic matter, but this material could not be clearly distinguished from carbonaceous contaminants known to be present in the Stardust aerogel collector.

Emotional Lability and Affective Synchrony in Borderline Personality Disorder

PubMed Central

Schoenleber, Michelle; Berghoff, Christopher R.; Tull, Matthew T.; DiLillo, David; Messman-Moore, Terri; Gratz, Kim L.

2015-01-01

Extant research on emotional lability in borderline personality disorder (BPD) has focused almost exclusively on lability of individual emotions or emotion types, with limited research considering how different types of emotions shift together over time. Thus, this study examined the temporal dynamics of emotion in BPD at the level of both individual emotions (i.e., self-conscious emotions [SCE], anger, and anxiety) and mixed emotions (i.e., synchrony between emotions). One hundred forty-four women from the community completed a diagnostic interview and laboratory study involving five emotion induction tasks (each of which was preceded and followed by a 5-min resting period or neutral task). State ratings of SCE, anger, and anxiety were provided at 14 time points (before and after each laboratory task and resting period). Hierarchical linear modeling results indicate that women with BPD reported greater mean levels of SCE and Anxiety (but not Anger), and greater lability of Anxiety. Women with BPD also exhibited greater variability in lability of all three emotions (suggestive of within-group differences in the relevance of lability to BPD). Results also revealed synchrony (i.e., positive relations) between each possible pair of emotions, regardless of BPD status. Follow-up regression analyses suggest the importance of accounting for lability when examining the role of synchrony in BPD, as the relation of SCE-Anger synchrony to BPD symptom severity was moderated by Anger and SCE lability. Specifically, synchronous changes in SCE and Anger were associated with greater BPD symptom severity when large shifts in SCE were paired with minor shifts in Anger. PMID:27362623

Extensive processing of sediment pore water dissolved organic matter during anoxic incubation as observed by high-field mass spectrometry (FTICR-MS).

PubMed

Valle, Juliana; Gonsior, Michael; Harir, Mourad; Enrich-Prast, Alex; Schmitt-Kopplin, Philippe; Bastviken, David; Conrad, Ralf; Hertkorn, Norbert

2018-02-01

Dissolved organic matter (DOM) contained in lake sediments is a carbon source for many microbial degradation processes, including aerobic and anaerobic mineralization. During anaerobic degradation, DOM is partially consumed and transformed into new molecules while the greenhouse gases methane (CH 4 ) and carbon dioxide (CO 2 ) are produced. In this study, we used ultrahigh resolution mass spectrometry to trace differences in the composition of solid-phase extractable (PPL resin) pore water DOM (SPE-DOM) isolated from surface sediments of three boreal lakes before and after 40 days of anoxic incubation, with concomitant determination of CH 4 and CO 2 evolution. CH 4 and CO 2 production detected by gas chromatography varied considerably among replicates and accounted for fractions of ∼2-4 × 10 -4 of sedimentary organic carbon for CO 2 and ∼0.8-2.4 × 10 -5 for CH 4 . In contrast, the relative changes of key bulk parameters during incubation, such as relative proportions of molecular series, elemental ratios, average mass and unsaturation, were regularly in the percent range (1-3% for compounds decreasing and 4-10% for compounds increasing), i.e. several orders of magnitude higher than mineralization alone. Computation of the average carbon oxidation state in CHO molecules of lake pore water DOM revealed rather non-selective large scale transformations of organic matter during incubation, with depletion of highly oxidized and highly reduced CHO molecules, and formation of rather non-labile fulvic acid type molecules. In general, proportions of CHO compounds slightly decreased. Nearly saturated CHO and CHOS lipid-like substances declined during incubation: these rather commonplace molecules were less specific indicators of lake sediment alteration than the particular compounds, such as certain oxygenated aromatics and carboxyl-rich alicyclic acids (CRAM) found more abundant after incubation. There was a remarkable general increase in many CHNO compounds during

Influence of anoxic pore water dissolved organic matter on the fate and transport of hydrophobic organic pollutants

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

Hunchak-Kariouk, K.

1992-01-01

Pore water dissolved organic matter is an overlooked pool of organic matter important to the environmental fate of hydrophobic organic pollutants. The association of polychlorinated biphenyls, polyaromatic hydrocarbons and chlorinated pesticides with pore water dissolved organic matter influences their distribution and mobility within the bottom sediment environment. Steep physical, biological and chemical gradients at the sediment/water interface isolate the pore water and create unique conditions within the sediment. This study indicates that any disturbance of this environment will alter the distribution and mobility of organic pollutants by changing their association to the pore water dissolved organic matter. A small volumemore » closed equilibration method was developed to measure the solubility enhancement of 2,2' 4,4'-tetrachlorobiphenyl (TeCB) by natural dissolved organic matter. Chemical coated micro-glass beads were equilibrated with anoxic and laboratory aerated (oxic) pore water samples in flame sealed ampules. The TeCB enhanced solubilities were used to determine the pore water dissolved organic matter partition coefficient, K[sub pwdom]. The measured TeCB solubility and K[sub pwdom] were much smaller for anoxic than oxic pore waters. The dissolved organic matter sorptive capacity for the TeCB increased as the water was aerated. This change is attributed to coagulative fractionation and structural changes of the pore water dissolved organic matter during aeration and was characterized by differences in the dissolved organic matter concentration, UV absorption at 254 nm, interfacial surface tension, and sorption capacity of molecular weight fractions of anoxic and oxic pore water dissolved organic matter. The increase in partitioning indicates that there will be an increase in the mobility of the TeCB as an anoxic bottom sediment environment is disturbed and aerated.« less

Use of an exchange method to estimate the association and dissociation rate constants of cadmium complexes formed with low-molecular-weight organic acids commonly exuded by plant roots.

PubMed

Schneider, André; Nguyen, Christophe

2011-01-01

Organic acids released from plant roots can form complexes with cadmium (Cd) in the soil solution and influence metal bioavailability not only due to the nature and concentration of the complexes but also due to their lability. The lability of a complex influences its ability to buffer changes in the concentration of free ions (Cd); it depends on the association (, m mol s) and dissociation (, s) rate constants. A resin exchange method was used to estimate and (m mol s), which is the conditional estimate of depending on the calcium (Ca) concentration in solution. The constants were estimated for oxalate, citrate, and malate, three low-molecular-weight organic acids commonly exuded by plant roots and expected to strongly influence Cd uptake by plants. For all three organic acids, the and estimates were around 2.5 10 m mol s and 1.3 × 10 s, respectively. Based on the literature, these values indicate that the Cd- low-molecular-weight organic acids complexes formed between Cd and low-molecular-weight organic acids may be less labile than complexes formed with soil soluble organic matter but more labile than those formed with aminopolycarboxylic chelates. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

High dimensional reflectance analysis of soil organic matter

NASA Technical Reports Server (NTRS)

Henderson, T. L.; Baumgardner, M. F.; Franzmeier, D. P.; Stott, D. E.; Coster, D. C.

1992-01-01

Recent breakthroughs in remote-sensing technology have led to the development of high spectral resolution imaging sensors for observation of earth surface features. This research was conducted to evaluate the effects of organic matter content and composition on narrowband soil reflectance across the visible and reflective infrared spectral ranges. Organic matter from four Indiana agricultural soils, ranging in organic C content from 0.99 to 1.72 percent, was extracted, fractionated, and purified. Six components of each soil were isolated and prepared for spectral analysis. Reflectance was measured in 210 narrow bands in the 400- to 2500-nm wavelength range. Statistical analysis of reflectance values indicated the potential of high dimensional reflectance data in specific visible, near-infrared, and middle-infrared bands to provide information about soil organic C content, but not organic matter composition. These bands also responded significantly to Fe- and Mn-oxide content.

How do natural, uncultivated microbes interact with organic matter? Insights from single cell genomics and metagenomics

NASA Astrophysics Data System (ADS)

Lloyd, K. G.; Bird, J.; Schreiber, L.; Petersen, D.; Kjeldsen, K.; Schramm, A.; Stepanauskas, R.; Jørgensen, B. B.

2013-12-01

Since most of the microbes in marine sediments remain uncultured, little is known about the mechanisms by which these natural communities degrade organic matter (OM). Likewise, little is known about the make-up of labile OM in marine sediments beyond general functional classes such as proteins, carbohydrates, and lipids, measured as monomers. However, microbes have complex interactions with specific polymers within these functional classes, which can be indicated by a microbe's enzymatic toolkit. We found that four single cell genomes of archaea have very different peptidase compositions than four single cells of bacteria, suggesting that archaea and bacteria may play different roles in OM degradation. We also found that predicted extracellular cysteine peptidases, which require chemically reducing conditions, were common in IMG database metagenomes from marine sediments, and absent in those from seawater. This suggests that the pathways, and not just the rates, of OM degradation may differ between seawater and sediments. By comparing enzyme classes in different organisms, or in different types of marine environments, we present an emerging view of the microbial potential for specific carbon remineralization pathways in marine sediments. In addition, the methods we present hold promise for characterizing OM degradation in any environment where genomic information is available.

Adsorption of natural dissolved organic matter at the oxide/water interface

USGS Publications Warehouse

Davis, James A.

1982-01-01

Natural organic matter is readily adsorbed by alumina and kaolinite in the pH range of natural waters. Adsorption occurs by complex formation between surface hydroxyls and the acidic functional groups of the organic matter. Oxides with relatively acidic surface hydroxyls, e.g. silica, do not react strongly with the organic matter. Under conditions typical for natural waters, almost complete surface coverage by adsorbed organic matter may be expected for alumina, hydrous iron oxides and the edge sites of aluminosilicates. Potentiometric titration and electrophoresis indicate that most of the acidic functional groups of the adsorbed organic matter are neutralized by protons from solution. The organic coating is expected to have a great influence on subsequent adsorption of inorganic cations and anions.

Is litter decomposition 'primed' by primary producer-release of labile carbon in terrestrial and aquatic experimental systems?

NASA Astrophysics Data System (ADS)

Soares, A. Margarida P. M.; Kritzberg, Emma S.; Rousk, Johannes

2015-04-01

It is possible that recalcitrant organic matter (ROM) can be 'activated' by inputs of labile organic matter (LOM) through the priming effect (PE). Investigating the PE is of major importance to fully understand the microbial use of ROM and its role on carbon (C) and nutrient cycling in both aquatic and terrestrial ecosystems. In aquatic ecosystems it is thought that the PE is triggered by periphytic algae release of LOM. Analogously, in terrestrial systems it is hypothesized that the LOM released in plant rhizospheres, or from the green crusts on the surface of agricultural soils, stimulate the activity and growth of ROM decomposers. Most previous studies on PE have utilised pulse additions of single substrates at high concentrations. However, to achieve an assessment of the true importance of the PE, it is important to simulate a realistic delivery of LOM. We investigated, in a series of 2-week laboratory experiments, how primary producer (PP)-release of LOM influence litter degradation in terrestrial and aquatic experimental systems. We used soil (terrestrial) and pond water (aquatic) microbial communities to which litter was added under light and dark conditions. In addition, glucose was added at PP delivery rates in dark treatments to test if the putative PE in light systems could be reproduced. We observed an initial peak of bacterial growth rate followed by an overall decrease over time with no treatment differences. In light treatments, periphytic algae growth and increased fungal production was stimulated when bacterial growth declined. In contrast, both fungal growth and algal production were negligible in dark treatments. This reveals a direct positive influence of photosynthesis on fungal growth. To investigate if PP LOM supplements, and the associated fungal growth, translate into a modulated litter decomposition, we are using stable isotopes to track the use of litter and algal-derived carbon by determining the δ13C in produced CO2. Fungi and bacteria

Soil aggregates, organic matter turnover and carbon balance in a Mediterranean eroded vineyard

NASA Astrophysics Data System (ADS)

Novara, Agata; Lo Papa, Giuseppe; Dazzi, Carmelo; Gristina, Luciano; Cerdà, Artemi

2014-05-01

The carbon cycle is being affected by the human impacts (Novara et al., 2011; Yan-Gui et al., 2013), and one of those is the intensification in the soil erosion in agriculture land (Cerdà et al., 2009; García Orenes et al., 2009). Vineyards also are affected by the human activities (Fernández Calviño, 2012). Vineyards in Sicily are cultivated on 110.000 ha, 10% of which on >10% slope. Deficiencies of soil organic matter are typical of the semi arid Mediterranean environment especially where traditional intensive cropping practices are adopted (Novara et al., 2012; 2013). These practices in vineyards could lead soil to intensive erosion processes (Novara et al., 2011). The fate of SOC under erosion processes is difficult to understand because of the influence of the erosion impact on SOC pathway, which depends on the different features of the process involved (detachment, transport and/or deposition). Soil erosion must be considered a net C source (Lal, 2003), as eroded soils have lower net primary productivity (NPP) (Dick and Gregorich, 2004) caused by reduction in the effective rooting depth and all in all determining decline in soil quality. Breakdown of aggregates and soil dispersion expose SOM to microbial/enzymatic processes and chemical soil properties (Dimoyiannis, 2012; Kocyigit and Demirci, 2012). Moreover the light fraction, transported by runoff, is labile and easily mineralized determining CO2 emission in the atmosphere (Jacinthe and Lal, 2004). Therefore, the carbon pool is lower in eroded than in un-eroded soil scapes and the rate of mineralization of soil organic matter is higher in sediments than in original soil. In this survey we show a research conducted on a slope sequence of three soil profiles in an irrigated vineyard located in Sambuca di Sicilia, Italy (UTM33-WGS84: 4169367N; 325011E). The SOC content was measured at depth intervals of 10 cm up to a depth of 60 cm in each pedon. Wet aggregate-size fractions with no prior chemical

Characterization of plasma labile heme in hemolytic conditions

PubMed Central

Gouveia, Zélia; Carlos, Ana R.; Yuan, Xiaojing; Aires-da-Silva, Frederico; Stocker, Roland; Maghzal, Ghassan J.; Leal, Sónia S.; Gomes, Cláudio M.; Todorovic, Smilja; Iranzo, Olga; Ramos, Susana; Santos, Ana C.; Hamza, Iqbal; Gonçalves, João; Soares, Miguel P.

2018-01-01

Extracellular hemoglobin, a byproduct of hemolysis, can release its prosthetic heme groups upon oxidation. This produces metabolically active heme that is exchangeable between acceptor proteins, macromolecules and low molecular weight ligands, termed here labile heme. As it accumulates in plasma labile heme acts in a pro-oxidant manner and regulates cellular metabolism while exerting pro-inflammatory and cytotoxic effects that foster the pathogenesis of hemolytic diseases. Here, we developed and characterized a panel of heme-specific single domain antibodies (sdAbs) that together with a cellular-based heme reporter assay, allow for quantification and characterization of labile heme in plasma during hemolytic conditions. Using these approaches, we demonstrate that when generated during hemolytic conditions labile heme is bound to plasma molecules with an affinity higher than 10−7 m and that 2–8% (∼ 2–5 μm) of the total amount of heme detected in plasma can be internalized by bystander cells, termed here bioavailable heme. Acute, but not chronic, hemolysis is associated with transient reduction of plasma heme-binding capacity, that is, the ability of plasma molecules to bind labile heme with an affinity higher than 10−7 m. The heme-specific sdAbs neutralize the pro-oxidant activity of soluble heme in vitro, suggesting that these maybe used to counter the pathologic effects of labile heme during hemolytic conditions. Finally, we show that heme-specific sdAbs can be used to visualize cellular heme. In conclusion, we describe a panel of heme-specific sdAbs that when used with other approaches provide novel insights to the pathophysiology of heme. PMID:28783254

Advanced solid-state NMR spectroscopy of natural organic matter.

PubMed

Mao, Jingdong; Cao, Xiaoyan; Olk, Dan C; Chu, Wenying; Schmidt-Rohr, Klaus

2017-05-01

Solid-state NMR is essential for the characterization of natural organic matter (NOM) and is gaining importance in geosciences and environmental sciences. This review is intended to highlight advanced solid-state NMR techniques, especially a systematic approach to NOM characterization, and their applications to the study of NOM. We discuss some basics of how to acquire high-quality and quantitative solid-state 13 C NMR spectra, and address some common technical mistakes that lead to unreliable spectra of NOM. The identification of specific functional groups in NOM, primarily based on 13 C spectral-editing techniques, is described and the theoretical background of some recently-developed spectral-editing techniques is provided. Applications of solid-state NMR to investigating nitrogen (N) in NOM are described, focusing on limitations of the widely used 15 N CP/MAS experiment and the potential of improved advanced NMR techniques for characterizing N forms in NOM. Then techniques used for identifying proximities, heterogeneities and domains are reviewed, and some examples provided. In addition, NMR techniques for studying segmental dynamics in NOM are reviewed. We also briefly discuss applications of solid-state NMR to NOM from various sources, including soil organic matter, aquatic organic matter, organic matter in atmospheric particulate matter, carbonaceous meteoritic organic matter, and fossil fuels. Finally, examples of NMR-based structural models and an outlook are provided. Copyright © 2016 Elsevier B.V. All rights reserved.

The Case Against Charge Transfer Interactions in Dissolved Organic Matter Photophysics.

PubMed

McKay, Garrett; Korak, Julie A; Erickson, Paul R; Latch, Douglas E; McNeill, Kristopher; Rosario-Ortiz, Fernando L

2018-01-16

The optical properties of dissolved organic matter influence chemical and biological processes in all aquatic ecosystems. Dissolved organic matter optical properties have been attributed to a charge-transfer model in which donor-acceptor complexes play a primary role. This model was evaluated by measuring the absorbance and fluorescence response of organic matter isolates to changes in solvent temperature, viscosity, and polarity, which affect the position and intensity of spectra for known donor-acceptor complexes of organic molecules. Absorbance and fluorescence spectral shape were largely unaffected by these changes, indicating that the distribution of absorbing and emitting species was unchanged. Overall, these results call into question the wide applicability of the charge-transfer model for explaining organic matter optical properties and suggest that future research should explore other models for dissolved organic matter photophysics.

Influence of biochar and plant growth on organic matter dynamics in a reclaimed mine residue

NASA Astrophysics Data System (ADS)

Moreno-Barriga, Fabián; Díaz, Vicente; Alberto, Jose; Faz, Ángel; Zornoza, Raúl

2016-04-01

treatments with plant. Arylestarase showed significant correlations with pH and organic carbon, while β-glucosidase was related to total and soluble organic carbon. Thus, the high recalcitrance of biochar increased the total organic carbon, but decreased soluble carbon, likely by adsorption, and was not able to activate microbial populations. A labile source of organic matter should be added together with the proposed amendments to promote the activation of microbial communities and likely the formation of stable aggregates, since root exudates were not enough for this purpose. Acknowledgement : This work has been funded by Fundación Séneca (Agency of Science and Technology of the Region of Murcia, Spain) by the project 18920/JLI/13

Assessment of soil organic matter persistence under different land uses applying a physical fractionation procedure

NASA Astrophysics Data System (ADS)

Giannetta, Beatrice; Plaza, César; López-de-Sá, Esther G.; Vischetti, Costantino; Zaccone, Claudio

2017-04-01

The understanding of the mechanisms involved in the build-up of soil organic matter (SOM) pools with long residence time is tightly linked to the comprehension of C dynamics. Organo-mineral associations are known to be strongly correlated with the accumulation of selective preserved C forms. Adsorption to minerals, as well as occlusion within aggregates, may affect SOM protection in different ways depending on its molecular structure and pedo-climatic conditions. In this research, we investigated changes in quantity and quality of SOM pools characterized by different protection mechanisms in coniferous and broadleaved forest soils, grassland soils, technosols and an agricultural soil with different organic amendments, in order to evaluate the influence of both land use and organic matter nature on physical and/or chemical stabilization of SOM. In particular, free (FR), intra-macroaggregate (MA), intra-microaggregate (MI), and mineral-associated (Min) fractions were separated in order to define physical and chemical mechanisms responsible for the SOM protection against degradation. All these SOM fractions were analyzed for organic C and total N concentration, and their stability assessed by thermogravimetric analysis (TD-TGA). Preliminary data show that, for all land uses, most of the organic C (40-60%) is found in the Min pool, followed by FR (20-40%)>MI MA. With the only exception of the FR, no significant correlations were found between the C/N ratio and a thermal stability index (H550-400/400-250) of each fraction; at the same time, a highly significant and positive correlation was found between these two parameters in all fractions isolated from agricultural soils. In particular, the thermal stability index measured in all Min fractions may be related to the more marked presence of labile compounds in this pool relative to recalcitrant compounds. Conversely, FR OM could not always represent a fresh and readily decomposable fraction.Furthermore, OM associated

Changes in the dissolved organic matter leaching from soil under severe temperature and N-deposition.

PubMed

Nguyen, Hang Vo-Minh; Choi, Jung Hyun

2015-06-01

In this study, we conducted growth chamber experiments using three types of soil (wetland, rice paddy, and forest) under the conditions of a severe increase in the temperature and N-deposition in order to investigate how extreme weather influences the characteristics of the dissolved organic matter (DOM) leaching from different soil types. This leachate controls the quantity and quality of DOM in surface water systems. After 5 months of incubation, the dissolved organic carbon (DOC) concentrations decreased in the range of 21.1 to 88.9 %, while the specific UV absorption (SUVA) values increased substantially in the range of 19.9 to 319.9 % for all of the samples. Higher increases in the SUVA values were observed at higher temperatures, whereas the opposite trend was observed for samples with N-addition. The parallel factor analysis (PARAFAC) results showed that four fluorescence components: terrestrial humic-like (component 1 (C1)), microbial humic-like (component 2 (C2)), protein-like (component 3 (C3)), and anthropogenic humic-like (component 4 (C4)) constituted the fluorescence matrices of soil samples. During the experiment, labile DOM from the soils was consumed and transformed into resistant aromatic carbon structures and less biodegradable components via microbial processes. The principle component analysis (PCA) results indicated that severe temperatures and N-deposition could enhance the contribution of the aromatic carbon compounds and humic-like components in the soil samples.

The characteristics of dissolved organic matter (DOM) and chromophoric dissolved organic matter (CDOM) in Antarctic sea ice

NASA Astrophysics Data System (ADS)

Norman, Louiza; Thomas, David N.; Stedmon, Colin A.; Granskog, Mats A.; Papadimitriou, Stathys; Krapp, Rupert H.; Meiners, Klaus M.; Lannuzel, Delphine; van der Merwe, Pier; Dieckmann, Gerhard S.

2011-05-01

An investigation of coloured dissolved organic matter (CDOM) and its relationships to physical and biogeochemical parameters in Antarctic sea ice and oceanic water have indicated that ice melt may both alter the spectral characteristics of CDOM in Antarctic surface waters and serve as a likely source of fresh autochthonous CDOM and labile DOC. Samples were collected from melted bulk sea ice, sea ice brines, surface gap layer waters, and seawater during three expeditions: one during the spring to summer and two during the winter to spring transition period. Variability in both physical (temperature and salinity) and biogeochemical parameters (dissolved and particulate organic carbon and nitrogen, as well as chlorophyll a) was observed during and between studies, but CDOM absorption coefficients measured at 375 nm (a 375) did not differ significantly. Distinct peaked absorption spectra were consistently observed for bulk ice, brine, and gap water, but were absent in the seawater samples. Correlation with the measured physical and biogeochemical parameters could not resolve the source of these peaks, but the shoulders and peaks observed between 260 and 280 nm and between 320 to 330 nm respectively, particularly in the samples taken from high light-exposed gap layer environment, suggest a possible link to aromatic and mycosporine-like amino acids. Sea ice CDOM susceptibility to photo-bleaching was demonstrated in an in situ 120 hour exposure, during which we observed a loss in CDOM absorption of 53% at 280 nm, 58% at 330 nm, and 30% at 375 nm. No overall coincidental loss of DOC or DON was measured during the experimental period. A relationship between the spectral slope (S) and carbon-specific absorption (a *375) indicated that the characteristics of CDOM can be described by the mixing of two broad end-members; and aged material, present in brine and seawater samples characterised by high S values and low a *375; and a fresh material, due to elevated in situ

Pharmacological ascorbate and ionizing radiation (IR) increase labile iron in pancreatic cancer☆

PubMed Central

Moser, Justin C.; Rawal, Malvika; Wagner, Brett A.; Du, Juan; Cullen, Joseph J.; Buettner, Garry R.

2013-01-01

Labile iron, i.e. iron that is weakly bound and is relatively unrestricted in its redox activity, has been implicated in both the pathogenesis as well as treatment of cancer. Two cancer treatments where labile iron may contribute to their mechanism of action are pharmacological ascorbate and ionizing radiation (IR). Pharmacological ascorbate has been shown to have tumor-specific toxic effects due to the formation of hydrogen peroxide. By catalyzing the oxidation of ascorbate, labile iron can enhance the rate of formation of hydrogen peroxide; labile iron can also react with hydrogen peroxide. Here we have investigated the magnitude of the labile iron pool in tumor and normal tissue. We also examined the ability of pharmacological ascorbate and IR to change the size of the labile iron pool. Although a significant amount of labile iron was seen in tumors (MIA PaCa-2 cells in athymic nude mice), higher levels were seen in murine tissues that were not susceptible to pharmacological ascorbate. Pharmacological ascorbate and irradiation were shown to increase the labile iron in tumor homogenates from this murine model of pancreatic cancer. As both IR and pharmacological ascorbate may rely on labile iron for their effects on tumor tissues, our data suggest that pharmacological ascorbate could be used as a radio-sensitizing agent for some radio-resistant tumors. PMID:24396727

Characterization of extractable soil organic matter pools from African Dark Earths (AfDE): A case study in historical biochar and organic waste amendments

NASA Astrophysics Data System (ADS)

Fujiu, Manna; Plante, Alain; Ohno, Tsutomu; Solomon, Dawit; Lehmann, Johannes; Fraser, James; Leach, Melissa; Fairhead, James

2014-05-01

Anthropogenic Dark Earths are soils generated through long-term human inputs of organic and pyrogenic materials. These soils were originally discovered in the Amazon, and have since been found in Australia and in this case in Africa. African Dark Earths (AfDE) are black, highly fertile and carbon-rich soils that were formed from the original highly-weathered infertile yellowish to red Oxisols and Ultisols through an extant but hitherto overlooked climate-smart sustainable soil management system that has long been an important feature of the indigenous West African agricultural repertoire. Studies have demonstrated that ADE soils in general have significantly different organic matter properties compared to adjacent non-DE soils, largely attributable to the presence of high concentrations of ash-derived carbon. Quantification and characterization of bulk soil organic matter of several (n=11) AfDE and non-AfDE pairs of surface (0-15 cm) soils using thermal analysis techniques (TG-DSC-EGA) confirmed substantial differences in SOM composition and the presence of pyrogenic C. Such pyrogenic organic matter is generally considered recalcitrant or relatively stable, but the goal of the current study was to characterize the presumably labile, more rapidly cycling, pools of C in AfDEs through the characterization of hot water- and pyrophosphate-extractable fractions, referred to as HWEOC and PyroC respectively. Extracts were analyzed for carbon content, as well as composition using fluorescence (EEM/PARAFAC) and high resolution mass spectrometry (FTICR-MS). The amount of extractable C as a proportion of total soil C was relatively low: less than ~0.8% for HWEOC and 2.8% for PyroC. The proportion of HWEOC did not differ (P = 0.18, paired t-test) between the AfDE and the non-AfDE soils, while the proportions of PyroC were significantly larger (P = 0.001) in the AfDE soils compared to the non-AfDE soils. Preliminary analysis of the EEM/PARAFAC data suggests that AfDE samples had

Enhancement of the natural organic matter removal from drinking water by nanofiltration.

PubMed

Matilainen, A; Liikanen, R; Nyström, M; Lindqvist, N; Tuhkanen, T

2004-03-01

Finnish surface waters are abundant in natural organic matter. Natural organic matter can be removed from drinking water in a water treatment process by coagulation and filtration. The standard treatment operations are not able to remove the smallest molar mass fraction of organic matter and the intermediate molar mass matter is only partly removed. The removal of residual natural organic matter from drinking water by nanofiltration was evalueted in this study. Three different nanofiltration membranes were compared in filtering six pre-treated surface waters. The total organic carbon content of the feed waters varied from 2.0 to 4.2 mg l(-1). Other water quality parameters measured were conductivity, alkalinity, hardness, UV-absorbance, SUVA, E2/E3 value and molecular size distribution by high-performance size-exclusion chromatography. The natural organic matter removal efficiencies of the membranes were good and varied between 100% and 49%, and between 85% and 47% according to molecular size distribution and total organic carbon measurements, respectively. Removal of different molecular size fractions varied from 100% to 56%, 100% to 54% and 88% to 19%, regarding high molar mass, intermediate molar mass and low molar mass organic matter, respectively. The Desal-5 DL membrane produced the highest natural organic matter removals.

Analysis of the Organic Matter in Interplanetary Dust Particles: Clues to the Organic Matter in Comets, Asteroids, and Interstellar Grains

NASA Technical Reports Server (NTRS)

Flynn, G. J.; Keller, L. P.

2003-01-01

Reflection spectroscopy suggests the C- , P-, and D-types of asteroids contain abundant carbon, but these Vis-nearIR spectra are featureless, providing no information on the type(s) of carbonaceous matter. Infrared spectroscopy demonstrates that organic carbon is a significant component in comets and as grains or grain coatings in the interstellar medium. Most of the interplanetary dust particles (IDPs) recovered from the Earth s stratosphere are believed to be fragments from asteroids or comets, thus characterization of the carbon in IDPs provides the opportunity to determine the type(s) and abundance of organic matter in asteroids and comets. Some IDPs exhibit isotopic excesses of D and N-15, indicating the presence of interstellar material. The characterization of the carbon in these IDPs, and particularly any carbon spatially associated with the isotopic anomalies, provides the opportunity to characterize interstellar organic matter.

Controls on the distribution of fluorescent dissolved organic matter during an under-ice algal bloom in the western Arctic Ocean

NASA Astrophysics Data System (ADS)

Mendoza, Wilson G.; Weiss, Elliot L.; Schieber, Brian; Greg Mitchell, B.

2017-07-01

In this study we used fluorescence excitation and emission matrix spectroscopy, hydrographic data, and a self-organizing map (SOM) analysis to assess the spatial distribution of labile and refractory fluorescent dissolved organic matter (FDOM) for the Chukchi and Beaufort Seas at the time of a massive under-ice phytoplankton bloom during early summer 2011. Biogeochemical properties were assessed through decomposition of water property classes and sample classification that employed a SOM neural network-based analysis which classified 10 clusters from 269 samples and 17 variables. The terrestrial, humic-like component FDOM (ArC1, 4.98 ± 1.54 Quinine Sulfate Units (QSU)) and protein-like component FDOM (ArC3, 1.63 ± 0.88 QSU) were found to have elevated fluorescence in the Lower Polar Mixed Layer (LPML) (salinity 29.56 ± 0.76). In the LPML water mass, the observed contribution of meteoric water fraction was 17%, relative to a 12% contribution from the sea ice melt fraction. The labile ArC3-protein-like component (2.01 ± 1.92 QSU) was also observed to be elevated in the Pacific Winter Waters mass, where the under-ice algal bloom was observed ( 40-50 m). We interpreted these relationships to indicate that the accumulation and variable distribution of the protein-like component on the shelf could be influenced directly by sea ice melt, transport, and mixing processes and indirectly by the in situ algal bloom and microbial activity. ArC5, corresponding to what is commonly considered marine humic FDOM, indicated a bimodal distribution with high values in both the freshest and saltiest waters. The association of ArC5 with deep, dense salty water is consistent with this component as refractory humic-like FDOM, whereas our evidence of a terrestrial origin challenges this classic paradigm for this component.

The Case Against Charge Transfer Interactions in Dissolved Organic Matter Optical Properties

NASA Astrophysics Data System (ADS)

McKay, G.; Korak, J.; Erickson, P. R.; Latch, D. E.; McNeill, K.; Rosario-Ortiz, F.

2017-12-01

The optical properties of dissolved organic matter influence chemical and biological processes in all aquatic ecosystems. Organic matter optical properties have been used by scientists and engineers for decades for remote sensing, in situ monitoring, and characterizing laboratory samples to track dissolved organic carbon concentration and character. However, there is still a lack of understanding of the origin of organic matter optical properties, which could conflict with other empirical fluorescence interpretation methods (e.g. PARAFAC). Organic matter optical properties have been attributed to a charge-transfer model in which donor-acceptor complexes play a primary role. This model was evaluated by measuring the absorbance and fluorescence response of organic matter isolates to perturbations in solvent temperature, viscosity, and polarity, which affect the position and intensity of spectra for known donor-acceptor complexes of organic molecules. Absorbance and fluorescence spectral shape were unaffected by these perturbations, indicating that the distribution of absorbing and emitting species was unchanged. These results call into question the wide applicability of the charge-transfer model for explaining organic matter optical properties and suggest that future research should explore other models for organic matter photophysics.

Soil organic matter decomposition and temperature sensitivity after forest fire in permafrost regions in Canada

NASA Astrophysics Data System (ADS)

Aaltonen, Heidi; Palviainen, Marjo; Köster, Kajar; Berninger, Frank; Pumpanen, Jukka

2017-04-01

On the Northern Hemisphere, 24% of soils are underlain by permafrost. These soils contain 50% of the global soil carbon pool. The Northern Hemisphere is also the region which is predicted to be most affected by climate warming and this causes uncertainties over the future of the permafrost. It has been estimated that 25% of permafrost might thaw by 2100, exposing previously frozen carbon pools to decomposition. In addition, global warming is expected to cause increase in the frequency of wild fires, which further increase permafrost melting by removing the insulating organic surface layer. The amount of released soil carbon from permafrost soils after forest fire is affected by degradability and temperature sensitivity of the soil organic matter, as well as soil depth and the stage of succession. Yet the common effect of these factors remains unclear. We studied how soil respiration and its temperature sensitivity (Q10) vary in different depths and within time by taking soil samples from different fire chronosequence areas (burned 3, 25, 46 and 100 years ago) from permafrost region in Northern Canada (Yukon and Northwest Territories, along Dempster Highway). The samples from three different depths (5, 10 and 30 cm) were incubated in four different temperatures (1, 7, 13 and 19°C) over 24h. Our results showed that the CO2 fluxes followed the stages of succession, with recently burned sites having lowest rates. The organic matter at 5 cm depth proved to be more labile and temperature sensitive than in deeper depths. The Q10 values, however, did not differ between sites, excluding 30 cm at the most recently burned site that had a significantly higher Q10 value than the other sites. The results implicate that heterotrophic soil respiration decreases on permafrost regions during the first stages after forest fire. At the same time the temperature sensitivity in deeper soil layers may increase.

Chemical and spectroscopic analyses of organic matter transformation in warming tundra soils

NASA Astrophysics Data System (ADS)

Herndon, E.; Roy Chowdhury, T.; Mann, B. F.; Graham, D. E.; Bargar, J.; Gu, B.; Liang, L.

2013-12-01

Many tundra soils are currently major carbon sinks; however, an increase in temperature may shift these systems to C sources and create a positive feedback for warming. In order to predict future C release from tundra soils, it is necessary to quantify rates of SOM degradation and to identify the reactants and products of microbial decomposition reactions. In this study, multiple spectroscopic techniques are used to investigate SOM during laboratory incubations of tundra soils. We aim to characterize the chemical transformation of organic matter during decomposition as a function of temperature and geochemistry. Frozen soil cores were obtained from the Barrow Environmental Observatory (BEO) in northern Alaska as part of the Next Generation Ecosystem Experiment Arctic project. To investigate the influence of temperature on organic matter degradation and compositional changes, soil horizons from each core were homogenized and soil material was incubated at -2°C, +4°C, or +8°C. Samples were sacrificed periodically over 100 days, and chemical and physical extractions were used to separate SOM into operationally-defined pools, including light (density < 1.6 g cm-2) and mineral-bound, and water-, acid-, base-, and non-soluble fractions. A suite of wet-chemical and spectroscopic analyses was used to measure CO2 and CH4 formation and soil C compositional changes, including techniques such as Fourier transform infrared spectroscopy, high performance liquid chromatography (HPLC), high resolution mass spectrometry, and X-ray absorption spectroscopy. Detailed chemical and spectroscopic analyses reveal significant differences amongst extracts and with depth in the soil. In general, more organic C was extracted in the base than in the acid and water fractions, and mineral-bound organic C increased with depth. The water-soluble C fraction showed the lowest molar absorptivity of the three extracts and consisted of mostly lower-molecular weight organics. Acid-soluble C increased

Ectomycorrhizal fungi contribute to soil organic matter cycling in sub-boreal forests.

PubMed

Phillips, Lori A; Ward, Valerie; Jones, Melanie D

2014-03-01

Soils of northern temperate and boreal forests represent a large terrestrial carbon (C) sink. The fate of this C under elevated atmospheric CO2 and climate change is still uncertain. A fundamental knowledge gap is the extent to which ectomycorrhizal fungi (EMF) and saprotrophic fungi contribute to C cycling in the systems by soil organic matter (SOM) decomposition. In this study, we used a novel approach to generate and compare enzymatically active EMF hyphae-dominated and saprotrophic hyphae-enriched communities under field conditions. Fermentation-humus (FH)-filled mesh bags, surrounded by a sand barrier, effectively trapped EMF hyphae with a community structure comparable to that found in the surrounding FH layer, at both trophic and taxonomic levels. In contrast, over half the sequences from mesh bags with no sand barrier were identified as belonging to saprotrophic fungi. The EMF hyphae-dominated systems exhibited levels of hydrolytic and oxidative enzyme activities that were comparable to or higher than saprotroph-enriched systems. The enzymes assayed included those associated with both labile and recalcitrant SOM degradation. Our study shows that EMF hyphae are likely important contributors to current SOM turnover in sub-boreal systems. Our results also suggest that any increased EMF biomass that might result from higher below-ground C allocation by trees would not suppress C fluxes from sub-boreal soils.

Ectomycorrhizal fungi contribute to soil organic matter cycling in sub-boreal forests

PubMed Central

Phillips, Lori A; Ward, Valerie; Jones, Melanie D

2014-01-01

Soils of northern temperate and boreal forests represent a large terrestrial carbon (C) sink. The fate of this C under elevated atmospheric CO2 and climate change is still uncertain. A fundamental knowledge gap is the extent to which ectomycorrhizal fungi (EMF) and saprotrophic fungi contribute to C cycling in the systems by soil organic matter (SOM) decomposition. In this study, we used a novel approach to generate and compare enzymatically active EMF hyphae-dominated and saprotrophic hyphae-enriched communities under field conditions. Fermentation-humus (FH)-filled mesh bags, surrounded by a sand barrier, effectively trapped EMF hyphae with a community structure comparable to that found in the surrounding FH layer, at both trophic and taxonomic levels. In contrast, over half the sequences from mesh bags with no sand barrier were identified as belonging to saprotrophic fungi. The EMF hyphae-dominated systems exhibited levels of hydrolytic and oxidative enzyme activities that were comparable to or higher than saprotroph-enriched systems. The enzymes assayed included those associated with both labile and recalcitrant SOM degradation. Our study shows that EMF hyphae are likely important contributors to current SOM turnover in sub-boreal systems. Our results also suggest that any increased EMF biomass that might result from higher below-ground C allocation by trees would not suppress C fluxes from sub-boreal soils. PMID:24173458

Coupled mobilization of dissolved organic matter and metals (Cu and Zn) in soil columns

NASA Astrophysics Data System (ADS)

Zhao, Lu Y. L.; Schulin, Rainer; Weng, Liping; Nowack, Bernd

2007-07-01

Dissolved organic carbon (DOC) is a key component involved in metal displacement in soils. In this study, we investigated the concentration profiles of soil-borne DOC, Cu and Zn at various irrigation rates with synthetic rain water under quasi steady-state conditions, using repacked soil columns with a metal-polluted topsoil and two unpolluted subsoils. Soil solution was collected using suction cups installed at centimeter intervals over depth. In the topsoil the concentrations of DOC, dissolved metals (Zn and Cu), major cations (Ca 2+ and Mg 2+) and anions ( NO3- and SO42-) increased with depth. In the subsoil, the Cu and Zn concentrations dropped to background levels within 2 cm. All compounds were much faster mobilized in the first 4 cm than in the rest of the topsoil. DOC and Cu concentrations were higher at higher flow rates for a given depth, whereas the concentrations of the other ions decreased with increasing flow rate. The decomposition of soil organic matter resulted in the formation of DOC, SO42-, and NO3- and was the main driver of the system. Regression analysis indicated that Cu mobilization was governed by DOC, whereas Zn mobilization was primarily determined by Ca and to a lesser extent by DOC. Labile Zn and Cu 2+ concentrations were well predicted by the NICA-Donnan model. The results highlight the value of high-resolution in-situ measurements of DOC and metal mobilization in soil profiles.

Impact of natural (storm) and anthropogenic (trawling) sediment resuspension on particulate organic matter in coastal environments

NASA Astrophysics Data System (ADS)

Pusceddu, A.; Grémare, A.; Escoubeyrou, K.; Amouroux, J. M.; Fiordelmondo, C.; Danovaro, R.

2005-12-01

In order to assess the impact of natural and anthropogenic sediment resuspension on quantity, biochemical composition and bioavailability of particulate organic matter (POM), two field investigations were carried out in two shallow coastal areas of the Mediterranean Sea. In the Gulf of Lions, we investigated the impact of a storm resuspension of sediment, whereas in the Thermaikos Gulf we investigated the impact of bottom trawling. Resuspension in the Gulf of Lions determined the increase of sedimentation rates, modified the composition of the organic fraction of settling particles and decreased the labile fraction of POM, as indicated by a drop in the enzymatically hydrolysable amino acid fraction. The increase in the refractory fraction, following short-term storm-induced resuspension, increased also the contribution of glycine and decreased the contribution of aspartic acid contents to the total amino acid pools. Trawling activities in Thermaikos Gulf determined a significant increase in suspended POM concentrations and important changes in its biochemical composition. After trawling, the protein to carbohydrate ratio decreased (as a result of a major input of sedimentary carbohydrates at the water-sediment interface) and the fraction of enzymatically hydrolysable biopolymeric C decreased by ≈30%, thus reducing the bioavailability of resuspended organic particles. Results of the present study indicate that changes in suspended POM, induced by storms and trawling activities, can have similar consequences on benthic systems and on food webs. In fact, the potential benefit of increased organic particle concentration for suspension feeders, is depressed by the shift of suspended food particles towards a more refractory composition.

Transient acidosis while retrieving a fear-related memory enhances its lability

PubMed Central

Du, Jianyang; Price, Margaret P; Taugher, Rebecca J; Grigsby, Daniel; Ash, Jamison J; Stark, Austin C; Hossain Saad, Md Zubayer; Singh, Kritika; Mandal, Juthika; Wemmie, John A; Welsh, Michael J

2017-01-01

Attenuating the strength of fearful memories could benefit people disabled by memories of past trauma. Pavlovian conditioning experiments indicate that a retrieval cue can return a conditioned aversive memory to a labile state. However, means to enhance retrieval and render a memory more labile are unknown. We hypothesized that augmenting synaptic signaling during retrieval would increase memory lability. To enhance synaptic transmission, mice inhaled CO2 to induce an acidosis and activate acid sensing ion channels. Transient acidification increased the retrieval-induced lability of an aversive memory. The labile memory could then be weakened by an extinction protocol or strengthened by reconditioning. Coupling CO2 inhalation to retrieval increased activation of amygdala neurons bearing the memory trace and increased the synaptic exchange from Ca2+-impermeable to Ca2+-permeable AMPA receptors. The results suggest that transient acidosis during retrieval renders the memory of an aversive event more labile and suggest a strategy to modify debilitating memories. DOI: http://dx.doi.org/10.7554/eLife.22564.001 PMID:28650315

Soil organic matter and the extracellular microbial matrix show contrasting responses to C and N availability

PubMed Central

Redmile-Gordon, M.A.; Evershed, R.P.; Hirsch, P.R.; White, R.P.; Goulding, K.W.T.

2015-01-01

An emerging paradigm in soil science suggests microbes can perform ‘N mining’ from recalcitrant soil organic matter (SOM) in conditions of low N availability. However, this requires the production of extracellular structures rich in N (including enzymes and structural components) and thus defies stoichiometric expectation. We set out to extract newly synthesised peptides from the extracellular matrix in soil and compare the amino acid (AA) profiles, N incorporation and AA dynamics in response to labile inputs of contrasting C/N ratio. Glycerol was added both with and without an inorganic source of N (10% 15N labelled NH4NO3) to a soil already containing a large pool of refractory SOM and incubated for 10 days. The resulting total soil peptide (TSP) and extracellular pools were compared using colorimetric methods, gas chromatography, and isotope ratio mass spectrometry. N isotope compositions showed that the extracellular polymeric substance (EPS) contained a greater proportion of products formed de novo than did TSP, with hydrophobic EPS-AAs (leucine, isoleucine, phenylalanine, hydroxyproline and tyrosine) deriving substantially more N from the inorganic source provided. Quantitative comparison between extracts showed that the EPS contained greater relative proportions of alanine, glycine, proline, phenylalanine and tyrosine. The greatest increases in EPS-peptide and EPS-polysaccharide concentrations occurred at the highest C/N ratios. All EPS-AAs responded similarly to treatment whereas the responses of TSP were more complex. The results suggest that extracellular investment of N (as EPS peptides) is a microbial survival mechanism in conditions of low N/high C which, from an evolutionary perspective, must ultimately lead to the tendency for increased N returns to the microbial biomass. A conceptual model is proposed that describes the dynamics of the extracellular matrix in response to the C/N ratio of labile inputs. PMID:26339106

Supramolecular chemistry: from molecular information towards self-organization and complex matter

NASA Astrophysics Data System (ADS)

Lehn, Jean-Marie

2004-03-01

supramolecular polymers and liquid crystals, and provide an original approach to nanoscience and nanotechnology. In particular, the spontaneous but controlled generation of well-defined, functional supramolecular architectures of nanometric size through self-organization represents a means of performing programmed engineering and processing of nanomaterials. Supramolecular chemistry is intrinsically a dynamic chemistry, in view of the lability of the interactions connecting the molecular components of a supramolecular entity and the resulting ability of supramolecular species to exchange their constituents. The same holds for molecular chemistry when a molecular entity contains covalent bonds that may form and break reversibly, so as to make possible a continuous change in constitution and structure by reorganization and exchange of building blocks. This behaviour defines a constitutional dynamic chemistry that allows self-organization by selection as well as by design at both the molecular and supramolecular levels. Whereas self-organization by design strives to achieve full control over the output molecular or supramolecular entity by explicit programming, self-organization by selection operates on dynamic constitutional diversity in response to either internal or external factors to achieve adaptation in a Darwinistic fashion. The merging of the features, information and programmability, dynamics and reversibility, constitution and structural diversity, points towards the emergence of adaptative and evolutionary chemistry. Together with the corresponding fields of physics and biology, it constitutes a science of informed matter, of organized, adaptative complex matter. This article was originally published in 2003 by the Israel Academy of Sciences and Humanities in the framework of its Albert Einstein Memorial Lectures series. Reprinted by permission of the Israel Academy of Sciences and Humanities.

Interstellar chemistry recorded in organic matter from primitive meteorites.

PubMed

Busemann, Henner; Young, Andrea F; Alexander, Conel M O'd; Hoppe, Peter; Mukhopadhyay, Sujoy; Nittler, Larry R

2006-05-05

Organic matter in extraterrestrial materials has isotopic anomalies in hydrogen and nitrogen that suggest an origin in the presolar molecular cloud or perhaps in the protoplanetary disk. Interplanetary dust particles are generally regarded as the most primitive solar system matter available, in part because until recently they exhibited the most extreme isotope anomalies. However, we show that hydrogen and nitrogen isotopic compositions in carbonaceous chondrite organic matter reach and even exceed those found in interplanetary dust particles. Hence, both meteorites (originating from the asteroid belt) and interplanetary dust particles (possibly from comets) preserve primitive organics that were a component of the original building blocks of the solar system.

Upregulation of transferrin receptor-1 induces cholangiocarcinoma progression via induction of labile iron pool.

PubMed

Jamnongkan, Wassana; Thanan, Raynoo; Techasen, Anchalee; Namwat, Nisana; Loilome, Watcharin; Intarawichian, Piyapharom; Titapun, Attapol; Yongvanit, Puangrat

2017-07-01

Labile iron pool is a cellular source of ions available for Fenton reactions resulting in oxidative stress. Living organisms avoid an excess of free irons by a tight control of iron homeostasis. We investigated the altered expression of iron regulatory proteins and iron discrimination in the development of liver fluke-associated cholangiocarcinoma. Additionally, the levels of labile iron pool and the functions of transferrin receptor-1 on cholangiocarcinoma development were also identified. Iron deposition was determined using the Prussian blue staining method in human cholangiocarcinoma tissues. We investigated the alteration of iron regulatory proteins including transferrin, transferrin receptor-1, ferritin, ferroportin, hepcidin, and divalent metal transporter-1 in cholangiocarcinoma tissues using immunohistochemistry. The clinicopathological data of cholangiocarcinoma patients and the expressions of proteins were analyzed. Moreover, the level of intracellular labile iron pool in cholangiocarcinoma cell lines was identified by the RhoNox-1 staining method. We further demonstrated transferrin receptor-1 functions on cell proliferation and migration upon small interfering RNA for human transferrin receptor 1 transfection. Results show that Iron was strongly stained in tumor tissues, whereas negative staining was observed in normal bile ducts of healthy donors. Interestingly, high iron accumulation was significantly correlated with poor prognosis of cholangiocarcinoma patients. The expressions of iron regulatory proteins in human cholangiocarcinoma tissues and normal liver from cadaveric donors revealed that transferrin receptor-1 expression was increased in the cancer cells of cholangiocarcinoma tissues when compared with the adjacent normal bile ducts and was significantly correlated with cholangiocarcinoma metastasis. Labile iron pool level and transferrin receptor-1 expression were significantly increased in KKU-214 and KKU-213 when compared with cholangiocyte

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.

Do soils loose phosphorus with dissolved organic matter?

NASA Astrophysics Data System (ADS)

Kaiser, K.; Brödlin, D.; Hagedorn, F.

2014-12-01

During ecosystem development and soil formation, primary mineral sources of phosphorus are becoming increasingly depleted. Inorganic phosphorus forms tend to be bound strongly to or within secondary minerals, thus, are hardly available to plants and are not leached from soil. What about organic forms of phosphorus? Since rarely studied, little is known on the composition, mobility, and bioavailability of dissolved organic phosphorus. There is some evidence that plant-derived compounds, such as phytate, bind strongly to minerals as well, while microbial compounds, such as nucleotides and nucleic acids, may represent more mobile fractions of soil phosphorus. In some weakly developed, shallow soils, leaching losses of phosphorus seem to be governed by mobile organic forms. Consequently, much of the phosphorus losses observed during initial stages of ecosystem development may be due to the leaching of dissolved organic matter. However, the potentially mobile microbial compounds are enzymatically hydrolysable. Forest ecosystems on developed soils already depleted in easily available inorganic phosphorus are characterized by rapid recycling of organic phosphors. That can reduce the production of soluble forms of organic phosphorus as well as increase the enzymatic hydrolysis and subsequent plant uptake of phosphorus bound within dissolved organic matter. This work aims at giving an outlook to the potential role of dissolved organic matter in the cycling of phosphorus within developing forest ecosystems, based on literature evidence and first results of ongoing research.

Anthropogenic aerosols as a source of ancient dissolved organic matter in glaciers

USGS Publications Warehouse

Stubbins, Aron; Hood, Eran; Raymond, Peter A.; Aiken, George R.; Sleighter, Rachel L.; Hernes, Peter J.; Butman, David; Hatcher, Patrick G.; Striegl, Robert G.; Schuster, Paul F.; Abdulla, Hussain A.N.; Vermilyea, Andrew W.; Scott, Durelle T.; Spencer, Robert G.M.

2012-01-01

Glacier-derived dissolved organic matter represents a quantitatively significant source of ancient, yet highly bioavailable carbon to downstream ecosystems. This finding runs counter to logical perceptions of age–reactivity relationships, in which the least reactive material withstands degradation the longest and is therefore the oldest. The remnants of ancient peatlands and forests overrun by glaciers have been invoked as the source of this organic matter. Here, we examine the radiocarbon age and chemical composition of dissolved organic matter in snow, glacier surface water, ice and glacier outflow samples from Alaska to determine the origin of the organic matter. Low levels of compounds derived from vascular plants indicate that the organic matter does not originate from forests or peatlands. Instead, we show that the organic matter on the surface of the glaciers is radiocarbon depleted, consistent with an anthropogenic aerosol source. Fluorescence spectrophotometry measurements reveal the presence of protein-like compounds of microbial or aerosol origin. In addition, ultrahigh-resolution mass spectrometry measurements document the presence of combustion products found in anthropogenic aerosols. Based on the presence of these compounds, we suggest that aerosols derived from fossil fuel burning are a source of pre-aged organic matter to glacier surfaces. Furthermore, we show that the molecular signature of the organic matter is conserved in snow, glacier water and outflow, suggesting that the anthropogenic carbon is exported relatively unchanged in glacier outflows.

Organic geochemical analysis of sedimentary organic matter associated with uranium

USGS Publications Warehouse

Leventhal, J.S.; Daws, T.A.; Frye, J.S.

1986-01-01

Samples of sedimentary organic matter from several geologic environments and ages which are enriched in uranium (56 ppm to 12%) have been characterized. The three analytical techniqyes used to study the samples were Rock-Eval pyrolysis, pyrolysis-gas chromatography-mass spectrometry, and solid-state C-13 nuclear magnetic resonance (NMR) spectroscopy. In samples with low uranium content, the pyrolysis-gas chromatography products contain oxygenated functional groups (as hydroxyl) and molecules with both aliphatic and aromatic carbon atoms. These samples with low uranium content give measurable Rock-Eval hydrocarbon and organic-CO2 yields, and C-13 NMR values of > 30% aliphatic carbon. In contrast, uranium-rich samples have few hydrocarbon pyrolysis products, increased Rock-Eval organic-CO2 contents and > 70% aromatic carbon contents from C-13 NMR. The increase in aromaticity and decrease in hydrocarbon pyrolysis yield are related to the amount of uranium and the age of the uranium minerals, which correspond to the degree of radiation damage. The three analytical techniques give complementary results. Increase in Rock-Eval organic-CO2 yield correlates with uranium content for samples from the Grants uranium region. Calculations show that the amount of organic-CO2 corresponds to the quantity of uranium chemically reduced by the organic matter for the Grants uranium region samples. ?? 1986.

Warming-Induced Changes to the Molecular Composition of Soil Organic Matter

NASA Astrophysics Data System (ADS)

Feng, X.; Simpson, M. J.; Simpson, A. J.; Wilson, K. P.; Williams, D.

2007-12-01

Soil organic matter (SOM) contains two times more carbon than the atmosphere and the potential changes to SOM quantity and quality with global warming are a major concern. It is commonly believed that global warming will accelerate the decomposition of labile SOM compounds while refractory SOM constituents will remain stable. However, experimental evidence of molecular-level changes to SOM composition with global warming is currently lacking. Here we employ SOM biomarkers and nuclear magnetic resonance (NMR) spectroscopy to study SOM composition and degradation in a soil warming experiment in southern Ontario, Canada. The soil warming experiment consisted of a control and a treatment plot in a mixed forest that had a temperature difference of about 5 degrees C for 14 months. Before soil warming the control and treatment plots had the same organic carbon (OC) content and SOM composition. Soil warming significantly increased soil OC content and the abundance of cutin-derived carbon originating from leaf tissues and decreased carbohydrates that are regarded as easily degradable. Lignin components, which are believed to be part of the stable and slowly-cycling SOM, were observed to be in an advanced stage of degradation. This observation is corroborated by increases in fungal biomass in the warmed soil because fungi are considered the primary decomposer of lignin in the soil environment. An NMR study of SOM in the warmed and control plots indicates that alkyl carbon, mainly originating from plant cuticles in the soil, increased in the warmed soil while O-alkyl carbon, primarily occurring in carbohydrates, decreased. Aromatic and phenolic carbon regions, which include the main structures found in lignin, decreased in the warmed soil. These data collectively suggest that there is a great potential for lignin degradation with soil warming, and that the refractory (aromatic) soil carbon storage may be reduced as a result of increased fungal growth in a warmer climate.

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.

Optical Characterization and Bioavailability of Dissolved Organic Matter of Leaf Leachates from Restored and Forested Delmarva Bay Catchments

NASA Astrophysics Data System (ADS)

Reed, E.; Armstrong, A.

2016-12-01

The optical properties and lability of fresh leaf and litter leachates obtained from Delmarva wetlands were analyzed to gain a further understanding of the carbon inputs and outputs of that wetland system. Carbon entering the wetland system may be digested by microbes and then given off as either carbon dioxide or methane, both of which enter the atmosphere as greenhouse gases. Delmarva Bays are often considered geographically isolated and only have surface water present in certain times of year. The vegetation around the wetlands are assumed to be a major input of the dissolved organic matter (DOM) in the wetland surface water. An understanding of the sources and lability of wetland water DOM can lead to further insight into the connections between vegetation, wetland management, and carbon cycling. Two paired wetland sites were sampled in this study, each included a forested catchment and a prior-converted agricultural wetland that had undergone hydrological ecosystem restoration. Leaf samples of Liquidambar styraciflua, Acer rubrum, Nyssa sylvatica, Polygonum, and Typha were taken directly from the living plant or from surrounding ground as litter. Spectral properties of the leachates were determined from fluorescence and absorbance, including PARAFAC components, fluorescence index (FI), humification index (HI), and the specific ultraviolet absorbance (SUVA). Leachates were also incubated with microbes taken from Tuckahoe Creek, a stream to which all sampled sites eventually drain, to determine the bioavailability of the carbon. There were measurable differences found between samples obtained from leaves and litter, as well as a difference between the herbaceous and tree samples. The results obtained from this study can help create more accurate models of how carbon cycles through these wetlands, both in forested and restored environments.

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.

Crop residue management and fertilization effects on soil organic matter and associated biological properties.

PubMed

Zhao, Bingzi; Zhang, Jiabao; Yu, Yueyue; Karlen, Douglas L; Hao, Xiying

2016-09-01

Returning crop residue may result in nutrient reduction in soil in the first few years. A two-year field experiment was conducted to assess whether this negative effect is alleviated by improved crop residue management (CRM). Nine treatments (3 CRM and 3 N fertilizer rates) were used. The CRM treatments were (1) R0: 100 % of the N using mineral fertilizer with no crop residues return; (2) R: crop residue plus mineral fertilizer as for the R0; and (3) Rc: crop residue plus 83 % of the N using mineral and 17 % manure fertilizer. Each CRM received N fertilizer rates at 270, 360, and 450 kg N ha(-1) year(-1). At the end of the experiment, soil NO3-N was reduced by 33 % from the R relative to the R0 treatment, while the Rc treatment resulted in a 21 to 44 % increase in occluded particulate organic C and N, and 80 °C extracted dissolved organic N, 19 to 32 % increase in microbial biomass C and protease activity, and higher monounsaturated phospholipid fatty acid (PLFA):saturated PLFA ratio from stimulating growth of indigenous bacteria when compared with the R treatment. Principal component analysis showed that the Biolog and PLFA profiles in the three CRM treatments were different from each other. Overall, these properties were not influenced by the used N fertilizer rates. Our results indicated that application of 17 % of the total N using manure in a field with crop residues return was effective for improving potential plant N availability and labile soil organic matter, primarily due to a shift in the dominant microorganisms.

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

Distribution of dissolved and labile particulate trace metals in the overlying bottom water in the Vistula River plume (southern Baltic Sea).

PubMed

Sokolowski, A; Wolowicz, M; Hummel, H

2001-10-01

Overlying bottom water samples were collected in the Vistula River plume, southern Baltic Sea, (Poland) and analysed for dissolved and labile particulate (1 M HCl extractable) Cu, Pb, Zn, Mn, Fe and Ni, hydrological parameters being measured simultaneously. Particulate organic matter (POM), chlorophyll a and dissolved oxygen are key factors governing the chemical behaviour of the measured metal fractions. For the dissolved Cu, Pb, Zn, Fe and Ni two maxima, in the shallow and in the deeper part of the river plume, were found. In the shallow zone desorption from seaward fluxing metal-rich riverine particles account for markedly increased metal concentrations, as confirmed also by high particulate metal contents. For Pb, atmospheric inputs were also considered to have contributed to the elevated concentrations of dissolved Pb adjacent to the river mouth. In the deep zone desorption from detrital and/or resuspended particles by aerobic decomposition of organic material may be the main mechanism responsible for enrichment of particle-reactive metals (Cu, Pb, Zn) in the overyling bottom waters. The increased concentrations of dissolved Fe may have been due to reductive dissolution of Fe oxyhydroxides within the deep sediments by which dissolved Ni was released to the water. The distribution of Mn was related to dissolved oxygen concentrations, indicating that Mn is released to the water column under oxygen reduced conditions. However, Mn transfer to the dissolved phase from anoxic sediments in deeper part of the Vistula plume was hardly evidenced suggesting that benthic flux of Mn occurs under more severe reductive regime than is consistent with mobilization of Fe. Behaviour of Mn in a shallower part has been presumably affected by release from porewaters and by oxidization into less soluble species resulting in seasonal removal of this metal (e.g. in April) from the dissolved phase. The particulate fractions represented from about 6% (Ni) and 33% (Mn, Zn, Cu) to 80% (Fe

Characterization of organic matter in lake sediments from Minnesota and Yellowstone National Park

USGS Publications Warehouse

Dean, Walter E.

2006-01-01

Samples of sediment from lakes in Minnesota and Yellowstone National Park (YNP) were analyzed for organic carbon (OC), hydrogen richness by Rock-Eval pyrolysis, and stable carbon- and nitrogen-isotope composition of bulk organic matter. Values of delta 13C of lake plankton tend to be around -28 to -32 parts per thousand (0/00). Organic matter with values of delta 13C in the high negative 20s overlap with those of organic matter derived from C3 higher terrestrial plants but are at least 10 0/00 more depleted in 13C than organic matter derived from C4 terrestrial plants. If the organic matter is produced mainly by photosynthetic plankton and is not oxidized in the water column, there may be a negative correlation between H-richness (Rock-Eval pyrolysis H-index) and delta 13C, with more H-rich, algal organic matter having lower values of delta 13C. However, if aquatic organic matter is oxidized in the water column, or if the organic matter is a mixture of terrestrial and aquatic organic matter, then there may be no correlation between H-richness and carbon-isotopic composition. Values of delta 13C lower than about -28 0/00 probably indicate a contribution of bacterial biomass produced in the hypolimnion by chemoautotrophy or methanotrophy. In highly eutrophic lakes in which large amounts of 13C-depleted organic matter is continually removed from the epilimnion by photosynthesis throughout the growing season, the entire carbon reservoir in the epilimnion may become severely 13C-enriched so that 13C-enriched photosynthetic organic matter may overprint 13C-depleted chemosynthetic bacterial organic matter produced in the hypolimnon. Most processes involved with the nitrogen cycle in lakes, such as production of ammonia and nitrate, tend to produce 15N-enriched values of delta 15N. Most Minnesota lake sediments are 15N-enriched. However, some of the more OC-rich sediments have delta 15N values close to zero (delta 15N of air), suggesting that organic matter production is

Organic matter variations in transgressive and regressive shales

USGS Publications Warehouse

Pasley, M.A.; Gregory, W.A.; Hart, G.F.

1991-01-01

Organic matter in the Upper Cretaceous Mancos Shale adjacent to the Tocito Sandstone in the San Juan Basin of New Mexico was characterized using organic petrology and organic geochemistry. Differences in the organic matter found in these regressive and transgressive offshore marine sediments have been documented and assessed within a sequence stratigraphic framework. The regressive Lower Mancos Shale below the Tocito Sandstone contains abundant well preserved phytoclasts and correspondingly low hydrogen indices. Total organic carbon values for the regressive shale are low. Sediments from the transgressive systems tract (Tocito Sandstone and overlying Upper Mancos Shale) contain less terrestrially derived organic matter, more amorphous non-structured protistoclasts, higher hydrogen indices and more total organic carbon. Advanced stages of degradation are characteristic of the phytoclasts found in the transgressive shale. Amorphous material in the transgressive shale fluoresces strongly while that found in the regressive shale is typically non-fluorescent. Data from pyrolysis-gas chromatography confirm these observations. These differences are apparently related to the contrasting depositional styles that were active on the shelf during regression and subsequent transgression. It is suggested that data from organic petrology and organic geochemistry provide greater resolution in sedimentologic and stratigraphic interpretations, particularly when working with basinward, fine-grained sediments. Petroleum source potential for the regressive Lower Mancos Shale below the Tocito Sandstone is poor. Based on abundant fluorescent amorphous material, high hydrogen indices, and high total organic carbon, the transgressive Upper Mancos Shale above the Tocito Sandstone possesses excellent source potential. This suggests that appreciable source potential can be found in offshore, fine-grained sediments of the transgressive systems tract below the condensed section and associated

Quantifying the degradation of organic matter in marine sediments: A review and synthesis

NASA Astrophysics Data System (ADS)

Arndt, Sandra; Jørgensen, B. B.; LaRowe, D. E.; Middelburg, J. J.; Pancost, R. D.; Regnier, P.

2013-08-01

Quantifying the rates of biogeochemical processes in marine sediments is essential for understanding global element cycles and climate change. Because organic matter degradation is the engine behind benthic dynamics, deciphering the impact that various forces have on this process is central to determining the evolution of the Earth system. Therefore, recent developments in the quantitative modeling of organic matter degradation in marine sediments are critically reviewed. The first part of the review synthesizes the main chemical, biological and physical factors that control organic matter degradation in sediments while the second part provides a general review of the mathematical formulations used to model these processes and the third part evaluates their application over different spatial and temporal scales. Key transport mechanisms in sedimentary environments are summarized and the mathematical formulation of the organic matter degradation rate law is described in detail. The roles of enzyme kinetics, bioenergetics, temperature and biomass growth in particular are highlighted. Alternative model approaches that quantify the degradation rate constant are also critically compared. In the third part of the review, the capability of different model approaches to extrapolate organic matter degradation rates over a broad range of temporal and spatial scales is assessed. In addition, the structure, functions and parameterization of more than 250 published models of organic matter degradation in marine sediments are analyzed. The large range of published model parameters illustrates the complex nature of organic matter dynamics, and, thus, the limited transferability of these parameters from one site to another. Compiled model parameters do not reveal a statistically significant correlation with single environmental characteristics such as water depth, deposition rate or organic matter flux. The lack of a generic framework that allows for model parameters to be

Characteristics of the surface chemistry of linden pyrochar after removal of labile organic matter

NASA Astrophysics Data System (ADS)

Valeeva, A. A.; Smirnova, E. V.; Giniyatullin, K. G.; Vorobev, V. V.; Biktasheva, L. R.; Grachev, A. N.

2018-01-01

The changes of chemical properties of the pyrochar surface were studied in the laboratory experiment that simulated pedogenic transformation of pyrochar under the influence of soil biota. The native pyrochar samples were obtained by pyrolysis of linden wood residues at the temperature of 250°C, 450°C and 650°C. Their modified samples were obtained by removing an easily degradable pool of organic substances that can be used by microorganisms during the first months after application to the soil. In low-temperature linden pyrochar (250°C and 450°C) dominated carboxylic and phenolic surface groups, in high-temperature (650°C) - lactonic groups. After removal of readily decomposable organic substances the acidity of the phenolic and lactonic groups in pyrochar of low-temperature pyrolysis sharply decreased. Characteristic feature of all studied samples is the presence in IR spectra of absorption bands of gyroxyl, carbonyl, methylene groups and organosilicon polymers. The feature of IR spectra of linden pyrochar (250°C and 450°C) is the presence of absorption bands of the stretching vibrations of the tertiary alcohols and phenols C-O group.

Origin and fate of particulate and dissolved organic matter in a naturally iron-fertilized region of the Southern Ocean

NASA Astrophysics Data System (ADS)

Tremblay, L.; Caparros, J.; Leblanc, K.; Obernosterer, I.

2015-01-01

Natural iron fertilization of high-nutrient low-chlorophyll (HNLC) waters induces annually occurring spring phytoplankton blooms off the Kerguelen Islands (Southern Ocean). To examine the origin and fate of particulate and dissolved organic matter (POM and DOM), D- and L-amino acids (AA) were quantified at bloom and HNLC stations. Total hydrolyzable AA accounted for 21-25% of surface particulate organic carbon (%POCAA) at the bloom sites, but for 10% at the HNLC site. A marked decrease in %POCAA with depth was observed at the most productive stations leading to values between 3 and 5% below 300 m depth. AA contributed to only 0.9-4.4% of dissolved organic carbon (%DOCAA) at all stations. The only consistent vertical trend was observed at the most productive station (A3-2) where %DOCAA decreased from ~ 2% in the surface waters to 0.9% near 300 m. These AA yields revealed that POM and DOM were more rapidly altered or mineralized at the bloom sites compared to the HNLC site. Alteration state was also assessed by trends in C / N ratio, %D-AA and degradation index. Different molecular markers indicated that POM mostly originated from diatoms and bacteria. The estimated average proportion of POM from intact phytoplankton cells in surface waters was 45% at the bloom station A3-2, but 14% at the HNLC site. Estimates based on D-AA yields indicated that ~ 15% of POM and ~ 30% of DOM was of bacterial origin (cells and cell fragments) at all stations. Surprisingly, the DOM in HNLC waters appeared less altered than the DOM from the bloom, had slightly higher dissolved AA concentrations, and showed no sign of alteration within the water column. Unfavorable conditions for bacterial degradation in HNLC regions can explain these findings. In contrast, large inputs of labile organic molecules and iron likely stimulate the degradation of organic matter (priming effect) and the production of more recalcitrant DOM (microbial carbon pump) during iron-fertilized blooms.

Origin and fate of particulate and dissolved organic matter in a naturally iron-fertilized region of the Southern Ocean

NASA Astrophysics Data System (ADS)

Tremblay, L.; Caparros, J.; Leblanc, K.; Obernosterer, I.

2014-10-01

Natural iron fertilization of high-nutrient low-chlorophyll (HNLC) waters induces annually occurring spring phytoplankton blooms off Kerguelen Islands (Southern Ocean). To examine the origin and fate of particulate and dissolved organic matter (POM and DOM), D- and L-amino acids (AA) were quantified at bloom and HNLC stations. Total hydrolysable AA accounted for 21-25% of surface particulate organic carbon (%POCAA) at the bloom sites, but for 10% at the HNLC site. A marked decrease in %POCAA with depth was observed at the most productive stations leading to values between 3 and 5% below 300 m depth. AA contributed to only 0.9-4.4% of dissolved organic carbon (%DOCAA) at all stations. The only consistent vertical trend was observed at the most productive station (A3-2) where %DOCAA decreased from ∼2% in the surface waters to 0.9% near 300 m. These AA yields and other markers revealed that POM and DOM were more rapidly altered or mineralized at the bloom sites compared to the HNLC site. Different molecular markers indicated that POM mostly originated from diatoms and bacteria. The estimated average proportion of POM from intact phytoplankton cells in surface waters was 45% at the bloom station A3-2, but 14% at the HNLC site. Estimates based on D-AA yields indicated that ∼15% of POM and ∼30% of DOM was of bacterial origin (cells and cell fragments) at all stations. Surprisingly, the DOM in HNLC waters appeared less altered than the DOM from the bloom, had slightly higher dissolved AA concentrations, and showed no sign of alteration within the water column. Unfavorable conditions for bacterial degradation in HNLC regions can explain these findings. In contrast, large inputs of labile organic molecules and iron, likely stimulate the degradation of organic matter (priming effect) and the production of more recalcitrant DOM (microbial carbon pump) during iron-fertilized blooms.

Repeated Labilization-Reconsolidation Processes Strengthen Declarative Memory in Humans

PubMed Central

Forcato, Cecilia; Rodríguez, María L. C.; Pedreira, María E.

2011-01-01

The idea that memories are immutable after consolidation has been challenged. Several reports have shown that after the presentation of a specific reminder, reactivated old memories become labile and again susceptible to amnesic agents. Such vulnerability diminishes with the progress of time and implies a re-stabilization phase, usually referred to as reconsolidation. To date, the main findings describe the mechanisms associated with the labilization-reconsolidation process, but little is known about its functionality from a biological standpoint. Indeed, two functions have been proposed. One suggests that destabilization of the original memory after the reminder allows the integration of new information into the background of the original memory (memory updating), and the other suggests that the labilization-reconsolidation process strengthens the original memory (memory strengthening). We have previously reported the reconsolidation of human declarative memories, demonstrating memory updating in the framework of reconsolidation. Here we deal with the strengthening function attributed to the reconsolidation process. We triggered labilization-reconsolidation processes successively by repeated presentations of the proper reminder. Participants learned an association between five cue-syllables and their respective response-syllables. Twenty-four hours later, the paired-associate verbal memory was labilized by exposing the subjects to one, two or four reminders. The List-memory was evaluated on Day 3 showing that the memory was improved when at least a second reminder was presented in the time window of the first labilization-reconsolidation process prompted by the earlier reminder. However, the improvement effect was revealed on Day 3, only when at least two reminders were presented on Day2 and not as a consequence of only retrieval. Therefore, we propose central concepts for the reconsolidation process, emphasizing its biological role and the parametrical constrains

Spectral band selection for classification of soil organic matter content

NASA Technical Reports Server (NTRS)

Henderson, Tracey L.; Szilagyi, Andrea; Baumgardner, Marion F.; Chen, Chih-Chien Thomas; Landgrebe, David A.

1989-01-01

This paper describes the spectral-band-selection (SBS) algorithm of Chen and Landgrebe (1987, 1988, and 1989) and uses the algorithm to classify the organic matter content in the earth's surface soil. The effectiveness of the algorithm was evaluated comparing the results of classification of the soil organic matter using SBS bands with those obtained using Landsat MSS bands and TM bands, showing that the algorithm was successful in finding important spectral bands for classification of organic matter content. Using the calculated bands, the probabilities of correct classification for climate-stratified data were found to range from 0.910 to 0.980.

Microbiological Insights of the Cycling of Chloroperoxidase-Reacted Organic Matter

NASA Astrophysics Data System (ADS)

Krzmarzick, M. J.; Boothe, M.; Lim, M. L.; Wang, X.; Brooks, M.

2016-12-01

Chloroperoxidase (CPO) enzymes from fungi are one mechanism in which organic matter is halogenated in terrestrial soils. In microcosm experiments, 17 groups of bacteria were found to substantially become enriched upon CPO-reacted organic matter amendment (CPO-OM). Though some enriched groups were organohalide-respiring bacteria, most were not related to any cultured isolates of bacteria and were either loosely linked to organohalide-degrading cultures or not at all. The large diversity of uncultured bacteria that is enriched from this substrate raises new questions regarding the pathways and mechanisms of the turnover of natural organochlorides. Upon changes in organic matter source material, salinity, temperature, and fermentable substrate, large changes in the CPO-OM enrichment culture occurred due to salinity, temperature, and fermentable substrate, though organic matter source material had a minimal effect. Thus, changes in geophysical conditions, not organic matter (pine forest vs oak forest), dominate the selection of bacteria implicated in the turnover of natural organochlorides. In related experiments, the CPO-OM enrichment culture expresses increased activity towards the dechlorination of chlorinated ethenes, indicating a direct connection between natural organochloride turnover and anthropogenic organochloride degradation and bioremediation, and could partly explain the heterogeneity of natural bioremediation potential at contaminated sites.

Old and stable soil organic matter is not necessarily chemically recalcitrant: Implications for modeling concepts and temperature sensitivity

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

Kleber, M.; Nico, P.S.; Plante, A.

2010-03-01

Soil carbon turnover models generally divide soil carbon into pools with varying intrinsic decomposition rates. Although these decomposition rates are modified by factors such as temperature, texture, and moisture, they are rationalized by assuming chemical structure is a primary controller of decomposition. In the current work, we use near edge X-ray absorption fine structure (NEXAFS) spectroscopy in combination with differential scanning calorimetry (DSC) and alkaline cupric oxide (CuO) oxidation to explore this assumption. Specifically, we examined material from the 2.3-2.6 kg L{sup -1} density fraction of three soils of different type (Oxisol, Alfisol, Inceptisol). The density fraction with the youngestmore » {sup 14}C age (Oxisol, 107 years) showed the highest relative abundance of aromatic groups and the lowest O-alkyl C/aromatic C ratio as determined by NEXAFS. Conversely, the fraction with the oldest C (Inceptisol, 680 years) had the lowest relative abundance of aromatic groups and highest O-alkyl C/aromatic C ratio. This sample also had the highest proportion of thermally labile materials as measured by DSC, and the highest ratio of substituted fatty acids to lignin phenols as indicated by CuO oxidation. Therefore, the organic matter of the Inceptisol sample, with a {sup 14}C age associated with 'passive' pools of carbon (680 years), had the largest proportion of easily metabolizable organic molecules with low thermodynamic stability, whereas the organic matter of the much younger Oxisol sample (107 years) had the highest proportion of supposedly stable organic structures considered more difficult to metabolize. Our results demonstrate that C age is not necessarily related to molecular structure or thermodynamic stability, and we suggest that soil carbon models would benefit from viewing turnover rate as codetermined by the interaction between substrates, microbial actors, and abiotic driving variables. Furthermore, assuming that old carbon is composed

Evolution of soil organic matter changes using pyrolysis and metabolic indices: a comparison between organic and mineral fertilization.

PubMed

Marinari, S; Masciandaro, G; Ceccanti, B; Grego, S

2007-09-01

The aim of this study was to evaluate chemical and biochemical changes of organic matter in fertilized (ammonium nitrate) and amended (vermicompost and manure) soils using pyrolysis and metabolic indices. The metabolic potential [dehydrogenase (DH-ase)/water soluble organic carbon (WSOC)], the metabolic quotient (qCO2) and the microbial quotient (Cmic:Corg) were calculated as indices of soil organic matter evolution. Pyrolysis-gas chromatography (Py-GC) was used to study structural changes in the organic matter. Carbon forms and microbial biomass have been measured by dichromate oxidation and fumigation-extraction methods, respectively. Dehydrogenase activity has been tested using INT (p-Iodonitrotetrazolium violet) as substrate. The results showed that organic amendment increased soil microbial biomass and its activity which were strictly related to pyrolytic mineralization and humification indices (N/O, B/E3). Mineral fertilization caused a greater alteration of native soil organic matter than the organic amendments, in that a high release of WSOC and relatively large amounts of aliphatic pyrolytic products, were observed. Therefore, the pyrolysis and metabolic indices provided similar and complementary information on soil organic matter changes after mineral and organic fertilization.

Response of organic matter quality in permafrost soils to warming

NASA Astrophysics Data System (ADS)

Plaza, C.; Pegoraro, E.; Schuur, E.

2016-12-01

Global warming is predicted to thaw large quantities of the perennially frozen organic matter stored in northern permafrost soils. Upon thaw, this organic matter will be exposed to lateral export to water bodies and to microbial decomposition, which may exacerbate climate change by releasing significant amounts of greenhouse gases. To gain an insight into these processes, we investigated how the quality of permafrost soil organic matter responded to five years of warming. In particular, we sampled control and experimentally warmed soils in 2009 and 2013 from an experiment established in 2008 in a moist acidic tundra ecosystem in Healy, Alaska. We examined surface organic (0 to 15 cm), deep organic (15 to 35 cm), and mineral soil layers (35 to 55 cm) separately by means of stable isotope analysis (δ13C and δ15N) and solid-state 13C nuclear magnetic resonance. Compared to the control, the experimental warming did not affect the isotopic and molecular composition of soil organic matter across the depth profile. However, we did find significant changes with time. In particular, in the surface organic layer, δ13C decreased and alkyl/O-alkyl ratio increased from 2009 to 2013, which indicated variations in soil organic sources (e.g., changes in vegetation) and accelerated decomposition. In the deep organic layer, we found a slight increase in δ15N with time. In the mineral layer, δ13C values decreased slightly, whereas alkyl C/O-alkyl ratio increased, suggesting a preferential loss of relatively more degraded organic matter fractions probably by lateral transport by water flowing through the soil. Acknowledgements: This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 654132. Web site: http://vulcan.comule.com

A comparison of soil organic matter physical fractionation methods

NASA Astrophysics Data System (ADS)

Duddigan, Sarah; Alexander, Paul; Shaw, Liz; Collins, Chris

2017-04-01

Selecting a suitable physical fractionation to investigate soil organic matter dynamics from the plethora that are available is a difficult task. An initial investigation of four different physical fractionation methods was conducted (i) Six et al. (2002); (ii) Zimmermann et al. (2007); (iii) Sohi et al. (2001); and (iv) Plaza et al. (2013). Soils used for this were from a long-term organic matter field plot study where a sandy loam soil was subjected to the following treatments: Peat (Pt), Horse Manure (H), Garden Compost (GCf), Garden Compost at half rate (GCh), and a bare plot control (BP). Although each of these methods involved the isolation of unique fractions, in the interest of comparison, each fraction was categorised as either being (i) physically protected (i.e. in aggregates); (ii) chemically protected (such as in organo-mineral complexes); or (iii) unprotected by either of these mechanisms (so-called 'free' organic matter). Regardless of the fractionation method used, a large amount of the variation in total C contents of the different treated soils is accounted for by the differences in unprotected particulate organic matter. When comparing the methods to one another there were no consistent differences in carbon content in the physically protected, chemically protected, or unprotected fractions as operationally defined across all the five organic matter treatments. Therefore fractionation method selection, for this research, was primarily driven by the practicalities of conducting each method in the lab. All of the methods tested had their limitations, for use in this research. This is not a criticism of the methods themselves but largely a result of the lack of suitability for these particular samples. For example, samples that contain a lot of gravel can lead to problems for methods that use size distribution for fractionation. Problems can also be encountered when free particulate organic matter contributes a large proportion of the sample

Non-labile silver species in biosolids remain stable throughout ...

EPA Pesticide Factsheets

Increasing commercial use of nanosilver has focussed attention on the fate of silver (Ag) in the wastewater release pathway. This paper reports the speciation and lability of Ag in archived, stockpiled, and contemporary biosolids from the UK, USA and Australia, and indicates that biosolids Ag concentrations have decreased significantly over recent decades. XANES revealed the importance of reduced-sulfur binding environments for Ag speciation in materials ranging from freshly produced sludge to biosolids weathered under ambient environmental conditions for more than 50 years. Isotopic dilution with 110mAg showed that Ag was predominantly non-labile in both fresh and aged biosolids (13.7% mean lability), with E-values ranging from 0.3 to 60 mg/kg and 5 mM CaNO3 extractable Ag from 1.2 to 609 µg/kg (0.002 - 3.4% of the total Ag). This study indicates that at the time of soil application, biosolids Ag will be predominantly Ag-sulfides and characterised by low isotopic lability. This paper presents an overview of biosolids Ag chemistry in historic and contemporary biosolids sourced from the UK, USA and Australia from the 1950s until today by drawing on a unique collection of archived, stockpiled and contemporary biosolids samples. Characteristics of biosolids Ag chemistry determined in this study included total Ag measurement by neutron activation analysis (NAA); the assessment of Ag lability by 110mAg isotopic dilution (E-values); and Ag speciation by X-ray Absorp

Use of stable isotopes of carbon and nitrogen to identify sources of organic matter to bed sediments of the Tualatin River, Oregon

USGS Publications Warehouse

Bonn, Bernadine A.; Rounds, Stewart A.

2010-01-01

presence of more labile organic matter in these areas. Results from this study indicate that strategies to improve oxygen conditions in the Tualatin River are likely to be more successful if they target sources of soil, leaf litter, and other terrestrially derived organic materials to the river rather than the instream growth of algae.

Partial coupling and differential regulation of biologically and photo-chemically labile dissolved organic carbon across boreal aquatic networks

NASA Astrophysics Data System (ADS)

Lapierre, J.-F.; del Giorgio, P. A.

2014-05-01

Despite the rapidly increasing volume of research on the biological and photochemical degradation of DOC in aquatic environments, little is known on the large-scale patterns in biologically and photo-chemically degradable DOC (Bd-DOC and Pd-DOC, respectively) in continental watersheds, and on the links that exist between these two key properties that greatly influence the flow of carbon from continents to oceans. Here we explore the patterns of Bd- and Pd-DOC across hundreds of boreal lakes, rivers and wetlands spanning a large range of system trophy and terrestrial influence, and compared the drivers of these two reactive pools of DOC at the landscape level. Using standardized incubations of natural waters, we found that the concentrations of Bd- and Pd-DOC co-varied across all systems studied but were nevertheless related to different pools of dissolved organic matter (DOM, identified by fluorescence analyses) in ambient waters. A combination of nutrients and protein-like DOM explained nearly half of the variation in Bd-DOC, whereas Pd-DOC was exclusively predicted by DOM optical properties, consistent with the photochemical degradability of specific fluorescent DOM (FDOM) pools that we experimentally determined. The concentrations of colored DOM (CDOM), a proxy of terrestrial influence, almost entirely accounted for the observed relationship between FDOM and the concentrations of both Bd- and Pd-DOC. The concentrations of CDOM and of the putative bio-labile fluorescence component shifted from complete decoupling in clear-water environments to strong coupling in browner streams and wetlands. This suggests a baseline autochthonous Bd-DOC pool fuelled by internal production that is gradually overwhelmed by land-derived Bd-DOC as terrestrial influence increases across landscape gradients. The importance of land as a major source of both biologically and photo-chemically degradable DOC for continental watersheds resulted in a partial coupling of those carbon pools in

Organic matter content of soil after logging of fir and redwood forests

Treesearch

Philip B. Durgin

1980-01-01

Organic matter in soil controls a variety of soil properties. A study in Humboldt County, California, evaluated changes in percentages of organic matter in soil as a function of time after timber harvest and soil depth in fir and redwood forests. To assess organic matter content, samples were taken from cutblocks of various ages in soil to depths of 1.33 m. Results...

Soil Organic Matter Content Effects on Dermal Pesticide ...

EPA Pesticide Factsheets

Agricultural landscapes serve as active amphibian breeding grounds despite their seemingly poor habitat value. Activity of adults and dispersal of metamorphs to and from agricultural ponds occurs in most species from spring through late summer or early fall, a time that coincides with pesticide applications on farm fields and crops. In terrestrial landscapes, dermal contact with contaminated soil and plant matter may lead to bioconcentration as well as lethal and sublethal effects in amphibians.Although the physiological structure of the amphibian dermis may facilitate pesticide uptake, soil properties may ultimately dictate bioavailability of pesticides in terrestrial habitats. The organic matter fraction of soil readily binds to pesticides, potentially decreasing the availability of pesticides adhering to biological matter. Soil partition coefficient organic carbon content and soil-specific Koc values may be important to indicating pesticide bioavailability and potential bioconcentration in amphibians. Our study was designed to evaluate dermal uptake of five pesticide active ingredients on either high or low organic matter soils. We predicted that amphibian body burdens would be a function of soil carbon content or Koc. with greater bioconcentration in individuals exposed to pesticides on sa

Soil organic matter as sole indicator of soil degradation.

PubMed

Obalum, S E; Chibuike, G U; Peth, S; Ouyang, Y

2017-04-01

Soil organic matter (SOM) is known to play vital roles in the maintenance and improvement of many soil properties and processes. These roles, which largely influence soil functions, are a pool of specific contributions of different components of SOM. The soil functions, in turn, normally define the level of soil degradation, viewed as quantifiable temporal changes in a soil that impairs its quality. This paper aims at providing a generalized assessment of the current state of knowledge on the usefulness of SOM in monitoring soil degradation, based on its influence on the physical, chemical and biological properties and processes of soils. Emphasis is placed particularly on the effect of SOM on soil structure and availability of plant nutrients. Although these properties are discussed separately, the soil system is of dynamic and interactive nature, and changes in one property will likely affect other soil properties as well. Thus, functions of SOM almost always affect various soil properties and processes and engage in multiple reactions. In view of its role in soil aggregation and erosion control, in availability of plant nutrients and in ameliorating other forms of soil degradation than erosion, SOM has proven to be an important indicator of soil degradation. It has been suggested, however, that rather than the absolute amount, temporal change and potential amount of SOM be considered in its use as indicator of soil degradation, and that SOM may not be an all-purpose indicator. Whilst SOM remains a candidate without substitute as long as a one-parameter indicator of soil degradation is needed, narrowing down to the use of its labile and microbial components could be more appropriate, since early detection is important in the control and management of soil degradation.

Bacterial biomarkers thermally released from dissolved organic matter

USGS Publications Warehouse

Greenwood, P.F.; Leenheer, J.A.; McIntyre, C.; Berwick, L.; Franzmann, P.D.

2006-01-01

Hopane biomarker products were detected using microscale sealed vessel (MSSV) pyrolysis gas chromatography-mass spectrometry (GC-MS) analysis of dissolved organic matter from natural aquatic systems colonised by bacterial populations. MSSV pyrolysis can reduce the polyhydroxylated alkyl side chain of bacteriohopanepolyols, yielding saturated hopane products which are more amenable to GC-MS detection than their functionalised precursors. This example demonstrates how the thermal conditions of MSSV pyrolysis can reduce the biologically-inherited structural functionality of naturally occurring organic matter such that additional structural fragments can be detected using GC methods. This approach complements traditional analytical pyrolysis methods by providing additional speciation information useful for establishing the structures and source inputs of recent or extant organic material. ?? 2006.

Influence of dissolved organic carbon content on modelling natural organic matter acid-base properties.

PubMed

Garnier, Cédric; Mounier, Stéphane; Benaïm, Jean Yves

2004-10-01

Natural organic matter (NOM) behaviour towards proton is an important parameter to understand NOM fate in the environment. Moreover, it is necessary to determine NOM acid-base properties before investigating trace metals complexation by natural organic matter. This work focuses on the possibility to determine these acid-base properties by accurate and simple titrations, even at low organic matter concentrations. So, the experiments were conducted on concentrated and diluted solutions of extracted humic and fulvic acid from Laurentian River, on concentrated and diluted model solutions of well-known simple molecules (acetic and phenolic acids), and on natural samples from the Seine river (France) which are not pre-concentrated. Titration experiments were modelled by a 6 acidic-sites discrete model, except for the model solutions. The modelling software used, called PROSECE (Programme d'Optimisation et de SpEciation Chimique dans l'Environnement), has been developed in our laboratory, is based on the mass balance equilibrium resolution. The results obtained on extracted organic matter and model solutions point out a threshold value for a confident determination of the studied organic matter acid-base properties. They also show an aberrant decreasing carboxylic/phenolic ratio with increasing sample dilution. This shift is neither due to any conformational effect, since it is also observed on model solutions, nor to ionic strength variations which is controlled during all experiments. On the other hand, it could be the result of an electrode troubleshooting occurring at basic pH values, which effect is amplified at low total concentration of acidic sites. So, in our conditions, the limit for a correct modelling of NOM acid-base properties is defined as 0.04 meq of total analysed acidic sites concentration. As for the analysed natural samples, due to their high acidic sites content, it is possible to model their behaviour despite the low organic carbon concentration.

THE INFLUENCE OF ORGANIC MATTER QUALITY ON THE TOXICITY AND PARTIONING OF SEDIMENT-ASSOCIATED FLUORANTHENE

EPA Science Inventory

Organic matter in sediment is derived from many sources, including dead plants and animals, fecal matter, and flocculated colloidal organic matter. hemical partitioning and toxicity of nonpolar organic contaminants is strongly affected by the quantity of sediment organic matter. ...

Perchlorate-induced combustion of organic matter with variable molecular weights: Implications for Mars missions

NASA Astrophysics Data System (ADS)

Sephton, Mark A.; Lewis, James M. T.; Watson, Jonathan S.; Montgomery, Wren; Garnier, Carole

2014-11-01

Instruments on the Viking landers and Curiosity rover analyzed samples of Mars and detected carbon dioxide and organic compounds of uncertain origin. Mineral-assisted reactions are leading to uncertainty, particularly those involving perchlorate minerals which thermally decompose to produce chlorine and oxygen which can then react with organic matter to generate organochlorine compounds and carbon dioxide. Although generally considered a problem for interpretation, the release profiles of generated gases can indicate the type of organic matter present. We have performed a set of experiments with perchlorate and organic matter of variable molecular weights. Results indicate that organic susceptibility to thermal degradation and mineral-assisted reactions is related to molecular weight. Low molecular weight organic matter reacts at lower temperatures than its high molecular weight counterparts. The natural occurrence and association of organic matter with differing molecular weights helps to discriminate between contamination (usually low molecular weight organic matter only) and indigenous carbon (commonly low and high molecular weight organic matter together). Our results can be used to provide insights into data returning from Mars.

Molecular imaging of labile iron(II) pools in living cells with a turn-on fluorescent probe.

PubMed

Au-Yeung, Ho Yu; Chan, Jefferson; Chantarojsiri, Teera; Chang, Christopher J

2013-10-09

Iron is an essential metal for living organisms, but misregulation of its homeostasis at the cellular level can trigger detrimental oxidative and/or nitrosative stress and damage events. Motivated to help study the physiological and pathological consequences of biological iron regulation, we now report a reaction-based strategy for monitoring labile Fe(2+) pools in aqueous solution and living cells. Iron Probe 1 (IP1) exploits a bioinspired, iron-mediated oxidative C-O bond cleavage reaction to achieve a selective turn-on response to Fe(2+) over a range of cellular metal ions in their bioavailable forms. We show that this first-generation chemical tool for fluorescence Fe(2+) detection can visualize changes in exchangeable iron stores in living cells upon iron supplementation or depletion, including labile iron pools at endogenous, basal levels. Moreover, IP1 can be used to identify reversible expansion of labile iron pools by stimulation with vitamin C or the iron regulatory hormone hepcidin, providing a starting point for further investigations of iron signaling and stress events in living systems as well as future probe development.

Insights in groundwater organic matter from Liquid Chromatography-Organic Carbon Detection

NASA Astrophysics Data System (ADS)

Rutlidge, H.; Oudone, P.; McDonough, L.; Andersen, M. S.; Baker, A.; Meredith, K.; O'Carroll, D. M.

2017-12-01

Understanding the processes that control the concentration and characteristics of organic matter in groundwater has important implications for the terrestrial global carbon budget. Liquid Chromatography - Organic Carbon Detection (LC-OCD) is a size-exclusion based chromatography technique that separates the organic carbon into molecular weight size fractions of biopolymers, humic substances, building blocks (degradation products of humic substances), low molecular weight acids and low molecular weight neutrals. Groundwater and surface water samples were collected from a range of locations in Australia representing different surface soil, land cover, recharge type and hydrological properties. At one site hyporheic zone samples were also collected from beneath a stream. The results showed a general decrease in the aromaticity and molecular weight indices going from surface water, hyporheic downwelling and groundwater samples. The aquifer substrate also affected the organic composition. For example, groundwater samples collected from a zone of fractured rock showed a relative decrease in the proportion of humic substances, suggestive of sorption or degradation of humic substances. This work demonstrates the potential for using LC-OCD in elucidating the processes that control the concentration and characteristics of organic matter in groundwater.

Organic matter controls of iron incorporation in growing sea ice

NASA Astrophysics Data System (ADS)

Janssens, Julie; Meiners, Klaus M.; Townsend, Ashley T.; Lannuzel, Delphine

2018-03-01

This study presents the first laboratory-controlled sea-ice growth experiment conducted under trace metal clean conditions. The role played by organic matter, in the incorporation of iron (Fe) into sea ice was investigated by means of laboratory ice-growth experiments using a titanium cold-finger apparatus. Experiments were also conducted to understand the role of extracellular polymeric substances (EPS) in the enrichment of ammonium in sea ice. Sea ice was grown from several seawater solutions containing different quantities and qualities of particulate Fe (PFe), dissolved Fe (DFe) and organic matter. Sea ice and seawater were analyzed for particulate organic carbon and nitrogen, macro-nutrients, extracellular EPS, PFe and DFe, and particulate aluminium. The experiments showed that biogenic PFe is preferentially incorporated into sea ice compared to lithogenic PFe. Furthermore, sea ice grown from ultra-violet (UV) and non-UV treated seawaters exhibits contrasting incorporation rates of organic matter and Fe. Whereas the effects of UV-treatments were not always significant, we do find indications that the type or organic matter controls the enrichment of Fe in forming sea ice.. Specifically, we come to the conclusion that the incorporation of DFe is favored by the presence of organic ligands in the source solution.

Soil Water Content Sensor Response to Organic Matter Content under Laboratory Conditions

PubMed Central

Fares, Ali; Awal, Ripendra; Bayabil, Haimanote K.

2016-01-01

Studies show that the performance of soil water content monitoring (SWCM) sensors is affected by soil physical and chemical properties. However, the effect of organic matter on SWCM sensor responses remains less understood. Therefore, the objectives of this study are to (i) assess the effect of organic matter on the accuracy and precision of SWCM sensors using a commercially available soil water content monitoring sensor; and (ii) account for the organic matter effect on the sensor’s accuracy. Sand columns with seven rates of oven-dried sawdust (2%, 4%, 6%, 8%, 10%, 12% and 18% v/v, used as an organic matter amendment), thoroughly mixed with quartz sand, and a control without sawdust were prepared by packing quartz sand in two-liter glass containers. Sand was purposely chosen because of the absence of any organic matter or salinity, and also because sand has a relatively low cation exchange capacity that will not interfere with the treatment effect of the current work. Sensor readings (raw counts) were monitored at seven water content levels (0, 0.02, 0.04, 0.08, 0.12, 0.18, 0.24, and 0.30 cm3 cm−3) by uniformly adding the corresponding volumes of deionized water in addition to the oven-dry one. Sensor readings were significantly (p < 0.05) affected by the organic matter level and water content. Sensor readings were strongly correlated with the organic matter level (R2 = 0.92). In addition, the default calibration equation underestimated the water content readings at the lower water content range (<0.05 cm3 cm−3), while it overestimated the water content at the higher water content range (>0.05 cm3 cm−3). A new polynomial calibration equation that uses raw count and organic matter content as covariates improved the accuracy of the sensor (RMSE = 0.01 cm3 cm−3). Overall, findings of this study highlight the need to account for the effect of soil organic matter content to improve the accuracy and precision of the tested sensor under different soils and

Soil Water Content Sensor Response to Organic Matter Content under Laboratory Conditions.

PubMed

Fares, Ali; Awal, Ripendra; Bayabil, Haimanote K

2016-08-05

Studies show that the performance of soil water content monitoring (SWCM) sensors is affected by soil physical and chemical properties. However, the effect of organic matter on SWCM sensor responses remains less understood. Therefore, the objectives of this study are to (i) assess the effect of organic matter on the accuracy and precision of SWCM sensors using a commercially available soil water content monitoring sensor; and (ii) account for the organic matter effect on the sensor's accuracy. Sand columns with seven rates of oven-dried sawdust (2%, 4%, 6%, 8%, 10%, 12% and 18% v/v, used as an organic matter amendment), thoroughly mixed with quartz sand, and a control without sawdust were prepared by packing quartz sand in two-liter glass containers. Sand was purposely chosen because of the absence of any organic matter or salinity, and also because sand has a relatively low cation exchange capacity that will not interfere with the treatment effect of the current work. Sensor readings (raw counts) were monitored at seven water content levels (0, 0.02, 0.04, 0.08, 0.12, 0.18, 0.24, and 0.30 cm³ cm(-3)) by uniformly adding the corresponding volumes of deionized water in addition to the oven-dry one. Sensor readings were significantly (p < 0.05) affected by the organic matter level and water content. Sensor readings were strongly correlated with the organic matter level (R² = 0.92). In addition, the default calibration equation underestimated the water content readings at the lower water content range (<0.05 cm³ cm(-3)), while it overestimated the water content at the higher water content range (>0.05 cm³ cm(-3)). A new polynomial calibration equation that uses raw count and organic matter content as covariates improved the accuracy of the sensor (RMSE = 0.01 cm³ cm(-3)). Overall, findings of this study highlight the need to account for the effect of soil organic matter content to improve the accuracy and precision of the tested sensor under different soils and

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

The importance of organic matter distribution and extract soil:solution ratio on the desorption of heavy metals from soils.

PubMed

Yin, Yujun; Impellitteri, Christopher A; You, Sun-Jae; Allen, Herbert E

2002-03-15

The lability (mobility and bioavailability) of metals varies significantly with soil properties for similar total soil metal concentrations. We studied desorption of Cu, Ni and Zn, from 15 diverse, unamended soils. These studies included evaluation of the effects of soil:solution extraction ratio and the roles of soil properties on metal desorption. Dcsorption was examined for each metal by computing distribution coefficients (Kd) for each metal in each soil where Kd = [M]soil/[M]solution, Results from soil:solution ratio studies demonstrated that Kd values for the metals tended to increase with increasing soil:solution ratio. This result also held true for distribution of soil organic matter (SOM). Because the soil:solution ratio has a significant effect on measured metal distributions, we selected a high soil:solution ratio to more closely approach natural soil conditions. Copper showed strong affinity to operationally defined dissolved organic matter (DOM). In this study, DOM was operationally defined based on the total organic carbon (TOC) content in 0.45-microm or 0.22-microm filtrates of the extracts. The Kd of Cu correlated linearly (r2 = 0.91) with the Kd of organic matter (Kd-om) where the Kd-om is equal to SOM as measured by Walkley-Black wet combustion and converted to total carbon (TC) by a factor of 0.59. These values representing solid phase TC were then divided by soluble organic carbon as measured by TOC analysis (DOM). The conversion factor of 0.59 was employed in order to construct Kd-om values based on solid phase carbon and solution phase carbon. SOM plays a significant role in the fate of Cu in soil systems. Soil-solution distribution of Ni and Zn, as well as the activity of free Cu2+, were closely related to SOM, but not to DOM. Kd values for Ni, Zn and free Cu2+ in a particular soil were divided by the SOM content in the same soil. This normalization of the Kd values for Ni, Zn, and free Cu2+ to the SOM content resulted in significant

Phenanthrene sorption with heterogeneous organic matter in a landfill aquifer material

USGS Publications Warehouse

Karapanagioti, H.K.; Sabatini, D.A.; Kleineidam, S.; Grathwohl, P.; Ligouis, B.

1999-01-01

Phenanthrene was used as a model chemical to study the sorption properties of Canadian River Alluvium aquifer material. Both equilibrium and kinetic sorption processes were evaluated through batch studies. The bulk sample was divided into subsamples with varying properties such as particle size, organic content, equilibration time, etc. in order to determine the effect of these properties on resulting sorption parameters. The data have been interpreted and the effect of experimental variables was quantified using the Freundlich isotherm model and a numerical solution of Fick's 2nd law in porous media. Microscopic organic matter characterization proved to be a valuable tool for explaining the results. Different organic matter properties and sorption mechanisms were observed for each soil subsample. Samples containing coal particles presented high Koc values. Samples with organic matter dominated by organic coatings on quartz grains presented low Koc values and contained a high percentage of fast sorption sites. The numerical solution of Fick's 2ndlaw requires the addition of two terms (fast and slow) in order to fit the kinetics of these heterogeneous samples properly. These results thus demonstrate the need for soil organic matter characterization in order to predict and explain the sorption properties of a soil sample containing heterogeneous organic matter and also the difficulty and complexity of modeling sorption in such samples.

Insights into the nature of cometary organic matter from terrestrial analogues

NASA Astrophysics Data System (ADS)

Court, Richard W.; Sephton, Mark A.

2012-04-01

The nature of cometary organic matter is of great interest to investigations involving the formation and distribution of organic matter relevant to the origin of life. We have used pyrolysis-Fourier transform infrared (FTIR) spectroscopy to investigate the chemical effects of the irradiation of naturally occurring bitumens, and to relate their products of pyrolysis to their parent assemblages. The information acquired has then been applied to the complex organic matter present in cometary nuclei and comae. Amalgamating the FTIR data presented here with data from published studies enables the inference of other comprehensive trends within hydrocarbon mixtures as they are progressively irradiated in a cometary environment, namely the polymerization of lower molecular weight compounds; an increased abundance of polycyclic aromatic hydrocarbon structures; enrichment in 13C; reduction in atomic H/C ratio; elevation of atomic O/C ratio and increase in the temperature required for thermal degradation. The dark carbonaceous surface of a cometary nucleus will display extreme levels of these features, relative to the nucleus interior, while material in the coma will reflect the degree of irradiation experienced by its source location in the nucleus. Cometary comae with high methane/water ratios indicate a nucleus enriched in methane, favouring the formation of complex organic matter via radiation-induced polymerization of simple precursors. In contrast, production of complex organic matter is hindered in a nucleus possessing a low methane/water ration, with the complex organic matter that does form possessing more oxygen-containing species, such as alcohol, carbonyl and carboxylic acid functional groups, resulting from reactions with hydroxyl radicals formed by the radiolysis of the more abundant water. These insights into the properties of complex cometary organic matter should be of particular interest to both remote observation and space missions involving in situ

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.

Fate and lability of silver in soils: Effect of ageing

EPA Science Inventory

The fate and lability of added soluble Ag in soils over time was examined by measurement of labile metal (E-value) by isotopic dilution using the ^110mAg radioactive isotope and the solid-phase speciation of Ag by X-ray absorption near edge structure (XANES) spectrosco...

Soil Organic Matter (SOM): Molecular Simulations

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

Andersen, Amity

Molecular simulation is a powerful tool used to gain an atomistic, molecular, and nanoscale level understanding of the structure, dynamics, and interactions from adsorption on minerals and assembly in aggregates of soil organic matter (SOM). Given the importance of SOM fate and persistence in soils and the current knowledge gaps, applications of atomistic scale simulations to study the complex compounds in SOM and their interactions in self-assembled aggregates composed of different organic matter compounds and with mineral surfaces of different types common in soils are few and far between. Here, we describe various molecular simulation methods that are currently inmore » use in various areas and applicable to SOM research, followed by a brief survey of specific applications to SOM research and an illustration with our own recent efforts in this area. We conclude with an outlook and the challenges for future research in this area.« less

Hot regions of labile and stable soil organic carbon in Germany - Spatial variability and driving factors

NASA Astrophysics Data System (ADS)

Vos, Cora; Jaconi, Angélica; Jacobs, Anna; Don, Axel

2018-06-01

Atmospheric carbon dioxide levels can be mitigated by sequestering carbon in the soil. Sequestration can be facilitated by agricultural management, but its influence is not the same on all soil carbon pools, as labile pools with a high turnover may be accumulated much faster but are also more vulnerable to losses. The aims of this study were to (1) assess how soil organic carbon (SOC) is distributed among SOC fractions on a national scale in Germany, (2) identify factors influencing this distribution and (3) identify regions with high vulnerability to SOC losses. The SOC content and proportion of two different SOC fractions were estimated for more than 2500 mineral topsoils (< 87 g kg-1 SOC) covering Germany, using near-infrared reflectance spectroscopy. Drivers of the spatial variability in SOC fractions were determined using the machine learning algorithm cforest. The SOC content and proportions of fractions were predicted with good accuracy (SOC content: R2 = 0.87-0.90; SOC proportions: R2 = 0.83; ratio of performance to deviation (RPD): 2.4-3.2). The main explanatory variables for the distribution of SOC among the fractions were soil texture, bulk soil C / N ratio, total SOC content and pH. For some regions, the drivers were linked to the land-use history of the sites. Arable topsoils in central and southern Germany were found to contain the highest proportions and contents of stable SOC fractions, and therefore have the lowest vulnerability to SOC losses. North-western Germany contains an area of sandy soils with unusually high SOC contents and high proportions of light SOC fractions, which are commonly regarded as representing a labile carbon pool. This is true for the former peat soils in this area, which have already lost and are at high risk of losing high proportions of their SOC stocks. Those black sands can, however, also contain high amounts of stable SOC due to former heathland vegetation and need to be treated and discussed separately from non

Pre-biotic organic matter from comets and asteroids

NASA Technical Reports Server (NTRS)

Anders, Edward

1989-01-01

Only meteoritic fragments small enough to be gently decelerated by the atmosphere (10 to the -12th g to 10 to the -6th g) can deliver organic matter intact. The amount of such 'soft-landed' organic carbon can be estimated from data for the infall rate of meteoritic matter. At present rates, only about 0.0006 g/sq cm intact organic carbon would accumulate in 100 million years, but at the higher rates of about four billion yr ago, about 20 g/sq cm may have accumulated in the few hundred million years between the last cataclysmic impact and the beginning of life. It may have included some biologically important compounds that did not form by abiotic synthesis on earth.

Mapping forest soil organic matter on New Jersey's coastal plain

Treesearch

Brian J. Clough; Edwin J. Green; Richard B. Lathrop

2012-01-01

Managing forest soil organic matter (SOM) stocks is a vital strategy for reducing the impact of anthropogenic carbon dioxide emissions. However, the SOM pool is highly variable, and developing accurate estimates to guide management decisions has remained a difficult task. We present the results of a spatial model designed to map soil organic matter for all forested...

Simplified method to assess soil organic matter in landscape and carbon sequestration studies

NASA Astrophysics Data System (ADS)

Pallasser, Robert; Minasny, Budiman; McBratney, Alex; de Bruyn, Hank

2010-05-01

Soil organic matter (SOM) is composed of a variety of carbon bearing forms which are variably susceptible to degradation, itself a function of soil conditions (moisture, permeability, pH, Eh). Stability and residence time have become key questions relevant to soil carbon storage. Interestingly, organic matter types also differ in terms of their refractory stabilities making thermal analysis potentially an ideal way to resolve and analyse SOM. Elemental analyses of soils are routinely used to provide accurate total carbon determinations for the subsamples in question but cannot yield information about the relative amounts of labile to more stable carbon without involved chemical pre-treatment. Thermogravimetric analyses (TGA) have been commonly used to characterise chemical decomposition and to provide distinctive fingerprints (due to discrete mass changes) for mineral and organic materials. Such discrete changes in mass appear as peaks when registered on a DTGA (differential TGA) plot and correspond with dehydration, denaturing or oxidation events. Soil being a more complex continuum of organic and inorganic substances, many from fermentation reactions and microbial waste, does not have one particular fingerprint. Nonetheless, a number of relevant organic substances have characteristically different but consistent ignition temperatures (Lopez-Capel et. al., 2006; Laird et al., 2008; Xie et. al., 2009) allowing carbon pools to be distinguished thermally. In our studies, oxidative DTGA analyses of soils using a TA 2590 were typified by a bimodal distribution in SOM representing one less stable and one more stable group, a pattern similarly described by Siewert (2004). Current experiments indicate that the relative proportions of these SOM pulses are fairly reproducible but vary depending on soils and sampling depth (i.e. conditions) enabling it as a diagnostic parameter when considering SOM dynamics and humification. In order to compare this property numerically

The Response of Heterotrophic Prokaryote and Viral Communities to Labile Organic Carbon Inputs Is Controlled by the Predator Food Chain Structure.

PubMed

Sandaa, Ruth-Anne; Pree, Bernadette; Larsen, Aud; Våge, Selina; Töpper, Birte; Töpper, Joachim P; Thyrhaug, Runar; Thingstad, Tron Frede

2017-08-23

Factors controlling the community composition of marine heterotrophic prokaryotes include organic-C, mineral nutrients, predation, and viral lysis. Two mesocosm experiments, performed at an Arctic location and bottom-up manipulated with organic-C, had very different results in community composition for both prokaryotes and viruses. Previously, we showed how a simple mathematical model could reproduce food web level dynamics observed in these mesocosms, demonstrating strong top-down control through the predator chain from copepods via ciliates and heterotrophic nanoflagellates. Here, we use a steady-state analysis to connect ciliate biomass to bacterial carbon demand. This gives a coupling of top-down and bottom-up factors whereby low initial densities of ciliates are associated with mineral nutrient-limited heterotrophic prokaryotes that do not respond to external supply of labile organic-C. In contrast, high initial densities of ciliates give carbon-limited growth and high responsiveness to organic-C. The differences observed in ciliate abundance, and in prokaryote abundance and community composition in the two experiments were in accordance with these predictions. Responsiveness in the viral community followed a pattern similar to that of prokaryotes. Our study provides a unique link between the structure of the predator chain in the microbial food web and viral abundance and diversity.

Priming effects on labile and stable soil organic carbon decomposition: Pulse dynamics over two years

PubMed Central

Han, Xiaozeng; Yu, Wantai; Wang, Peng; Cheng, Weixin

2017-01-01

Soil organic carbon (SOC) is a major component in the global carbon cycle. Yet how input of plant litter may influence the loss of SOC through a phenomenon called priming effect remains highly uncertain. Most published results about the priming effect came from short-term investigations for a few weeks or at the most for a few months in duration. The priming effect has not been studied at the annual time scale. In this study for 815 days, we investigated the priming effect of added maize leaves on SOC decomposition of two soil types and two treatments (bare fallow for 23 years, and adjacent old-field, represent stable and relatively labile SOC, respectively) of SOC stabilities within each soil type, using a natural 13C-isotope method. Results showed that the variation of the priming effect through time had three distinctive phases for all soils: (1) a strong negative priming phase during the first period (≈0–90 days); (2) a pulse of positive priming phase in the middle (≈70–160 and 140–350 days for soils from Hailun and Shenyang stations, respectively); and (3) a relatively stabilized phase of priming during the last stage of the incubation (>160 days and >350 days for soils from Hailun and Shenyang stations, respectively). Because of major differences in soil properties, the two soil types produced different cumulative priming effects at the end of the experiment, a positive priming effect of 3–7% for the Mollisol and a negative priming effect of 4–8% for the Alfisol. Although soil types and measurement times modulated most of the variability of the priming effect, relative SOC stabilities also influenced the priming effect for a particular soil type and at a particular dynamic phase. The stable SOC from the bare fallow treatment tended to produce a narrower variability during the first phase of negative priming and also during the second phase of positive priming. Averaged over the entire experiment, the stable SOC (i.e., the bare fallow) was at

Effects of ozonation pretreatment on natural organic matter and wastewater derived organic matter - Possible implications on the formation of ozonation by-products.

PubMed

Papageorgiou, Alexandros; Stylianou, Stylianos K; Kaffes, Pavlos; Zouboulis, Anastasios I; Voutsa, Dimitra

2017-03-01

The aim of this study was to investigate possible implications of natural and wastewater derived organic matter in river water that is subsequently used following treatment for drinking purposes. River water was subjected to lab-scale ozonation experiments under different ozone doses (0.1, 0.4, 0.8, 1.0 and 2.0 mgO 3 /mgC) and contact times (1, 3, 5, 8 and 10 min). Mixtures of river water with humic acids or wastewaters (sewage wastewater and secondary effluents) at different proportions were also ozonated. Dissolved organic carbon and biodegradable dissolved organic carbon concentrations as well as spectroscopic characteristics (UV absorbance and fluorescence intensities) of different types of dissolved organic matter and possible changes due to the ozonation treatment are presented. River water, humic substances and wastewater exhibited distinct spectroscopic characteristics that could serve for pollution source tracing. Wastewater impacted surface water results in higher formation of carbonyl compounds. However, the formation yield (μg/mgC) of wastewaters was lower than that of surface water possibly due to different composition of wastewater derived organic matter and the presence of scavengers, which may limit the oxidative efficiency of ozone. Copyright © 2016 Elsevier Ltd. All rights reserved.

The role of autochthonous organic matter in radioactive cesium accumulation to riverine fine sediments.

PubMed

Fujii, Manabu; Ono, Keisuke; Yoshimura, Chihiro; Miyamoto, Manami

2018-06-15

Anthropogenically released radioactive cesium (RCs) poses serious ecological and environmental concerns given its persistency in the environment. Although accumulation of RCs in aqueous and sedimentary environments is often reported to associate with organic matter (OM), the mechanisms responsible remain unclear. Here, we investigated RCs in fine sediments along the Abukuma River, the largest river near the Fukushima Daiichi Nuclear Power Plant, 1.5-4 years after the accident. Measuring the density-separated sediment fractions with a broad range of OM content (%) indicated that the RCs concentration (Bq·kg -1 ) is positively correlated with OM content for intermediate-density fractions in which OM is primarily characterized by autochthonous origin. This relationship, however, did not hold for light-density fractions containing a high proportion of large-size allochthonous OM. Furthermore, H 2 O 2 -assisted OM digestion and amorphous material dissolution treatments resulted in only a minor reduction in sedimentary RCs. These results along with the fact that sediments with high autochthonous OM content showed high specific surface area indicated that RCs is tightly associated with finer-grained and chemically non-labile inorganic fractions concurrently resident with autochthonous OM. Overall, our findings highlight that autochthonous OM exerts a significant control on the accumulation, transport, and fate of RCs in aqueous and sedimentary environments. Copyright © 2018 Elsevier Ltd. All rights reserved.

Controls on the distribution of fluorescent dissolved organic matter during an under‐ice algal bloom in the western Arctic Ocean

PubMed Central

Weiss, Elliot L.; Schieber, Brian; Greg Mitchell, B.

2017-01-01

Abstract In this study we used fluorescence excitation and emission matrix spectroscopy, hydrographic data, and a self‐organizing map (SOM) analysis to assess the spatial distribution of labile and refractory fluorescent dissolved organic matter (FDOM) for the Chukchi and Beaufort Seas at the time of a massive under‐ice phytoplankton bloom during early summer 2011. Biogeochemical properties were assessed through decomposition of water property classes and sample classification that employed a SOM neural network‐based analysis which classified 10 clusters from 269 samples and 17 variables. The terrestrial, humic‐like component FDOM (ArC1, 4.98 ± 1.54 Quinine Sulfate Units (QSU)) and protein‐like component FDOM (ArC3, 1.63 ± 0.88 QSU) were found to have elevated fluorescence in the Lower Polar Mixed Layer (LPML) (salinity ~29.56 ± 0.76). In the LPML water mass, the observed contribution of meteoric water fraction was 17%, relative to a 12% contribution from the sea ice melt fraction. The labile ArC3‐protein‐like component (2.01 ± 1.92 QSU) was also observed to be elevated in the Pacific Winter Waters mass, where the under‐ice algal bloom was observed (~40–50 m). We interpreted these relationships to indicate that the accumulation and variable distribution of the protein‐like component on the shelf could be influenced directly by sea ice melt, transport, and mixing processes and indirectly by the in situ algal bloom and microbial activity. ArC5, corresponding to what is commonly considered marine humic FDOM, indicated a bimodal distribution with high values in both the freshest and saltiest waters. The association of ArC5 with deep, dense salty water is consistent with this component as refractory humic‐like FDOM, whereas our evidence of a terrestrial origin challenges this classic paradigm for this component. PMID:28989231

Controls on the distribution of fluorescent dissolved organic matter during an under-ice algal bloom in the western Arctic Ocean.

PubMed

Mendoza, Wilson G; Weiss, Elliot L; Schieber, Brian; Greg Mitchell, B

2017-07-01

In this study we used fluorescence excitation and emission matrix spectroscopy, hydrographic data, and a self-organizing map (SOM) analysis to assess the spatial distribution of labile and refractory fluorescent dissolved organic matter (FDOM) for the Chukchi and Beaufort Seas at the time of a massive under-ice phytoplankton bloom during early summer 2011. Biogeochemical properties were assessed through decomposition of water property classes and sample classification that employed a SOM neural network-based analysis which classified 10 clusters from 269 samples and 17 variables. The terrestrial, humic-like component FDOM (ArC1, 4.98 ± 1.54 Quinine Sulfate Units (QSU)) and protein-like component FDOM (ArC3, 1.63 ± 0.88 QSU) were found to have elevated fluorescence in the Lower Polar Mixed Layer (LPML) (salinity ~29.56 ± 0.76). In the LPML water mass, the observed contribution of meteoric water fraction was 17%, relative to a 12% contribution from the sea ice melt fraction. The labile ArC3-protein-like component (2.01 ± 1.92 QSU) was also observed to be elevated in the Pacific Winter Waters mass, where the under-ice algal bloom was observed (~40-50 m). We interpreted these relationships to indicate that the accumulation and variable distribution of the protein-like component on the shelf could be influenced directly by sea ice melt, transport, and mixing processes and indirectly by the in situ algal bloom and microbial activity. ArC5, corresponding to what is commonly considered marine humic FDOM, indicated a bimodal distribution with high values in both the freshest and saltiest waters. The association of ArC5 with deep, dense salty water is consistent with this component as refractory humic-like FDOM, whereas our evidence of a terrestrial origin challenges this classic paradigm for this component.

Biodegradability of algal-derived organic matter in a large artificial lake by using stable isotope tracers.

PubMed

Lee, Yeonjung; Lee, Bomi; Hur, Jin; Min, Jun-Oh; Ha, Sun-Yong; Ra, Kongtae; Kim, Kyung-Tae; Shin, Kyung-Hoon

2016-05-01

In order to understand the biodegradability of algal-derived organic matter, biodegradation experiments were conducted with (13)C and (15)N-labeled natural phytoplankton and periphytic algal populations in experimental conditions for 60 days. Qualitative changes in the dissolved organic matter were also determined using parallel factor analysis and the stable carbon isotopic composition of the hydrophobic dissolved organic matter through the experimental period. Although algal-derived organic matter is considered to be easily biodegradable, the initial amounts of total organic carbon newly produced by phytoplankton and periphytic algae remained approximately 16 and 44 % after 60 days, respectively, and about 22 and 43 % of newly produced particulate nitrogen remained. Further, the dissolved organic carbon derived from both algal populations increased significantly after 60 days. Although the dissolved organic matter gradually became refractory, the contributions of the algal-derived organic matter to the dissolved organic matter and hydrophobic dissolved organic matter increased. Our laboratory experimental results suggest that algal-derived organic matter produced by phytoplankton and periphytic algae could contribute significantly to the non-biodegradable organic matter through microbial transformations.

Memory expression is independent of memory labilization/reconsolidation.

PubMed

Barreiro, Karina A; Suárez, Luis D; Lynch, Victoria M; Molina, Víctor A; Delorenzi, Alejandro

2013-11-01

There is growing evidence that certain reactivation conditions restrict the onset of both the destabilization phase and the restabilization process or reconsolidation. However, it is not yet clear how changes in memory expression during the retrieval experience can influence the emergence of the labilization/reconsolidation process. To address this issue, we used the context-signal memory model of Chasmagnathus. In this paradigm a short reminder that does not include reinforcement allows us to evaluate memory labilization and reconsolidation, whereas a short but reinforced reminder restricts the onset of such a process. The current study investigated the effects of the glutamate antagonists, APV (0.6 or 1.5 μg/g) and CNQX (1 μg/g), prior to the reminder session on both behavioral expression and the reconsolidation process. Under conditions where the reminder does not initiate the labilization/reconsolidation process, APV prevented memory expression without affecting long-term memory retention. In contrast, APV induced amnesic effects in the long-term when administered before a reminder session that triggers reconsolidation. Under the present parametric conditions, the administration of CNQX prior to the reminder that allows memory to enter reconsolidation impairs this process without disrupting memory expression. Overall, the present findings suggest that memory reactivation--but not memory expression--is necessary for labilization and reconsolidation. Retrieval and memory expression therefore appear not to be interchangeable concepts. Copyright © 2013 Elsevier Inc. All rights reserved.

Interstellar and Solar System Organic Matter Preserved in Interplanetary Dust

NASA Technical Reports Server (NTRS)

Messenger, Scott; Nakamura-Messenger, Keiko

2015-01-01

Interplanetary dust particles (IDPs) collected in the Earth's stratosphere derive from collisions among asteroids and by the disruption and outgassing of short-period comets. Chondritic porous (CP) IDPs are among the most primitive Solar System materials. CP-IDPs have been linked to cometary parent bodies by their mineralogy, textures, C-content, and dynamical histories. CP-IDPs are fragile, fine-grained (less than um) assemblages of anhydrous amorphous and crystalline silicates, oxides and sulfides bound together by abundant carbonaceous material. Ancient silicate, oxide, and SiC stardust grains exhibiting highly anomalous isotopic compositions are abundant in CP-IDPs, constituting 0.01 - 1 % of the mass of the particles. The organic matter in CP-IDPs is isotopically anomalous, with enrichments in D/H reaching 50x the terrestrial SMOW value and 15N/14N ratios up to 3x terrestrial standard compositions. These anomalies are indicative of low T (10-100 K) mass fractionation in cold molecular cloud or the outermost reaches of the protosolar disk. The organic matter shows distinct morphologies, including sub-um globules, bubbly textures, featureless, and with mineral inclusions. Infrared spectroscopy and mass spectrometry studies of organic matter in IDPs reveals diverse species including aliphatic and aromatic compounds. The organic matter with the highest isotopic anomalies appears to be richer in aliphatic compounds. These materials also bear similarities and differences with primitive, isotopically anomalous organic matter in carbonaceous chondrite meteorites. The diversity of the organic chemistry, morphology, and isotopic properties in IDPs and meteorites reflects variable preservation of interstellar/primordial components and Solar System processing. One unifying feature is the presence of sub-um isotopically anomalous organic globules among all primitive materials, including IDPs, meteorites, and comet Wild-2 samples returned by the Stardust mission.

Caracterisation of anthropogenic contribution to the coastal fluorescent organic matter

NASA Astrophysics Data System (ADS)

El Nahhal, Ibrahim; Nouhi, Ayoub; Mounier, Stéphane

2015-04-01

It is known that most of the coastal fluorescent organic matter is of a terrestrial origin (Parlanti, 2000; Tedetti, Guigue, & Goutx, 2010). However, the contribution of the anthropogenic organic matter to this pool is not well defined and evaluated. In this work the monitoring of little bay (Toulon Bay, France) was done in the way to determine the organic fluorescent response during a winter period. The sampling campaign consisted of different days during the month of December, 2014 ( 12th, 15th, 17th, 19th) on 21 different sampling sites for the fluorescence measurements (without any filtering of the samples) and the whole month of December for the bacterial and the turbidity measurements. Excitation Emission Matrices (EEMs) of fluorescence (from 200 to 400 nm and 220 to 420 nm excitation and emission range) were treated by parallel factor analysis (PARAFAC).The parafac analysis of the EEM datasets was conducted using PROGMEEF software in Matlab langage. On the same time that the turbidity and bacterial measurement (particularly the E.Coli concentration) were determined. The results gives in a short time range, information on the the contribution of the anthropogenic inputs to the coastal fluorescent organic matter. In addition, the effect of salinity on the photochemical degradation of the anthropogenic organic matter (especially those from wastewater treatment plants) will be studied to investigate their fate in the water end member by the way of laboratory experiments. Parlanti, E. (2000). Dissolved organic matter fluorescence spectroscopy as a tool to estimate biological activity in a coastal zone submitted to anthropogenic inputs. Organic Geochemistry, 31(12), 1765-1781. doi:10.1016/S0146-6380(00)00124-8 Tedetti, M., Guigue, C., & Goutx, M. (2010). Utilization of a submersible UV fluorometer for monitoring anthropogenic inputs in the Mediterranean coastal waters. Marine Pollution Bulletin, 60(3), 350-62. doi:10.1016/j.marpolbul.2009.10.018

Temperature response of litter and soil organic matter decomposition is determined by chemical composition of organic material.

PubMed

Erhagen, Björn; Öquist, Mats; Sparrman, Tobias; Haei, Mahsa; Ilstedt, Ulrik; Hedenström, Mattias; Schleucher, Jürgen; Nilsson, Mats B

2013-12-01

The global soil carbon pool is approximately three times larger than the contemporary atmospheric pool, therefore even minor changes to its integrity may have major implications for atmospheric CO2 concentrations. While theory predicts that the chemical composition of organic matter should constitute a master control on the temperature response of its decomposition, this relationship has not yet been fully demonstrated. We used laboratory incubations of forest soil organic matter (SOM) and fresh litter material together with NMR spectroscopy to make this connection between organic chemical composition and temperature sensitivity of decomposition. Temperature response of decomposition in both fresh litter and SOM was directly related to the chemical composition of the constituent organic matter, explaining 90% and 70% of the variance in Q10 in litter and SOM, respectively. The Q10 of litter decreased with increasing proportions of aromatic and O-aromatic compounds, and increased with increased contents of alkyl- and O-alkyl carbons. In contrast, in SOM, decomposition was affected only by carbonyl compounds. To reveal why a certain group of organic chemical compounds affected the temperature sensitivity of organic matter decomposition in litter and SOM, a more detailed characterization of the (13) C aromatic region using Heteronuclear Single Quantum Coherence (HSQC) was conducted. The results revealed considerable differences in the aromatic region between litter and SOM. This suggests that the correlation between chemical composition of organic matter and the temperature response of decomposition differed between litter and SOM. The temperature response of soil decomposition processes can thus be described by the chemical composition of its constituent organic matter, this paves the way for improved ecosystem modeling of biosphere feedbacks under a changing climate. © 2013 John Wiley & Sons Ltd.

Mapping Soil Organic Matter with Hyperspectral Imaging

NASA Astrophysics Data System (ADS)

Moni, Christophe; Burud, Ingunn; Flø, Andreas; Rasse, Daniel

2014-05-01

Soil organic matter (SOM) plays a central role for both food security and the global environment. Soil organic matter is the 'glue' that binds soil particles together, leading to positive effects on soil water and nutrient availability for plant growth and helping to counteract the effects of erosion, runoff, compaction and crusting. Hyperspectral measurements of samples of soil profiles have been conducted with the aim of mapping soil organic matter on a macroscopic scale (millimeters and centimeters). Two soil profiles have been selected from the same experimental site, one from a plot amended with biochar and another one from a control plot, with the specific objective to quantify and map the distribution of biochar in the amended profile. The soil profiles were of size (30 x 10 x 10) cm3 and were scanned with two pushbroomtype hyperspectral cameras, one which is sensitive in the visible wavelength region (400 - 1000 nm) and one in the near infrared region (1000 - 2500 nm). The images from the two detectors were merged together into one full dataset covering the whole wavelength region. Layers of 15 mm were removed from the 10 cm high sample such that a total of 7 hyperspectral images were obtained from the samples. Each layer was analyzed with multivariate statistical techniques in order to map the different components in the soil profile. Moreover, a 3-dimensional visalization of the components through the depth of the sample was also obtained by combining the hyperspectral images from all the layers. Mid-infrared spectroscopy of selected samples of the measured soil profiles was conducted in order to correlate the chemical constituents with the hyperspectral results. The results show that hyperspectral imaging is a fast, non-destructive technique, well suited to characterize soil profiles on a macroscopic scale and hence to map elements and different organic matter quality present in a complete pedon. As such, we were able to map and quantify biochar in our

Effect of mismanagement at the state of organic matter in soil

NASA Astrophysics Data System (ADS)

Hladký, Jan; Elbl, Jakub; Kynický, Jindřich; Dvořáčková, Helena; Juřička, David; Pecina, Václav; Brtnický, Martin

2017-04-01

Organic matter is an essential part of the soil. It affects the physical, chemical, and biological properties of the soil. It is therefore necessary to maintain organic matter in the soil and its quality as the prevention of soil degradation. Loss of organic matter is in the Czech Republic threatened up to 45% of arable soil. The most important reason for the loss of organic matter in the soil is poor management, especially improper crop rotation, cultivation of erosion-prone crops where erosion takes away valuable topsoil with nutrients and organic matter. The aim of our study was to verify the influence of inappropriate management on selected 5 plots in southern Moravia in the Czech Republic. It is the region with the highest incidence of water erosion in the Czech Republic. Were selected plots with significantly sloping, where corn was grown. Samples were taken in the autumn after the harvest, each of topsoil. The sampling sites were placed in positions on the slope where soil was not damaged by erosion, as well as the place greatest damage and the place where washed soil was accumulated. Soil average humus content was for undamaged position on the slope 1.93% and 0.84 quality, the most heavily damaged part of the slope humus content dropped to 1.35% and its quality at only 0.56. In the case of position of accumulated soils was found the average amount of humus 1.70% and 0.90 quality. Humus content and its quality is statistically significantly influenced by water erosion (α = 0.05). The study showed that bad management, when there is not crop rotation adapted to the given conditions and not subjected to any suitable soil-protecting technologies, there is significant damage to soils, which shows mainly organic matter decline and a decline in its quality. Continuation of our study will verify the possibility of stabilization of soil organic matter and draft appropriate technologies.

Optical properties and molecular diversity of dissolved organic matter in the Bering Strait and Chukchi Sea

NASA Astrophysics Data System (ADS)

Gonsior, Michael; Luek, Jenna; Schmitt-Kopplin, Philippe; Grebmeier, Jacqueline M.; Cooper, Lee W.

2017-10-01

Changes in the molecular composition of dissolved organic matter (DOM) and its light absorbing chromophoric component (CDOM) are of particular interest in the Arctic region because of climate change effects that lead to warmer sea surface temperatures and longer exposure to sunlight. We used continuous UV-vis (UV-vis) spectroscopy, excitation emission matrix fluorescence and ultrahigh resolution mass spectrometry during a transect from the Aleutian Islands in the Bering Sea to the Chukchi Sea ice edge through Bering Strait to determine the variability of DOM and CDOM. These data were combined with discrete sampling for stable oxygen isotopes of seawater, in order to evaluate the contributions of melted sea ice versus runoff to the DOM and CDOM components. This study demonstrated that high geographical resolution of optical properties in conjunction with stable oxygen ratios and non-targeted ultrahigh resolution mass spectrometry was able to distinguish between different DOM sources in the Arctic, including identification of labile DOM sources in Bering Strait associated with high algal blooms and sampling locations influenced by terrestrially-derived DOM, such as the terrestrial DOM signal originating from Arctic rivers and dirty/anchor sea ice. Results of this study also revealed the overall variability and chemodiversity of Arctic DOM present in the Bering and Chukchi Seas.

Fungal–bacterial dynamics and their contribution to terrigenous carbon turnover in relation to organic matter quality

PubMed Central

Fabian, Jenny; Zlatanovic, Sanja; Mutz, Michael; Premke, Katrin

2017-01-01

Ecological functions of fungal and bacterial decomposers vary with environmental conditions. However, the response of these decomposers to particulate organic matter (POM) quality, which varies widely in aquatic ecosystems, remains poorly understood. Here we investigated how POM pools of substrates of different qualities determine the relative contributions of aquatic fungi and bacteria to terrigenous carbon (C) turnover. To this end, surface sediments were incubated with different POM pools of algae and/or leaf litter. 13C stable-isotope measurements of C mineralization were combined with phospholipid analysis to link the metabolic activities and substrate preferences of fungal and bacterial heterotrophs to dynamics in their abundance. We found that the presence of labile POM greatly affected the dominance of bacteria over fungi within the degrader communities and stimulated the decomposition of beech litter primarily through an increase in metabolic activity. Our data indicated that fungi primarily contribute to terrigenous C turnover by providing litter C for the microbial loop, whereas bacteria determine whether the supplied C substrate is assimilated into biomass or recycled back into the atmosphere in relation to phosphate availability. Thus, this study provides a better understanding of the role of fungi and bacteria in terrestrial–aquatic C cycling in relation to environmental conditions. PMID:27983721

Impact of Labile Zinc on Heart Function: From Physiology to Pathophysiology

PubMed Central

Turan, Belma; Tuncay, Erkan

2017-01-01

Zinc plays an important role in biological systems as bound and histochemically reactive labile Zn2+. Although Zn2+ concentration is in the nM range in cardiomyocytes at rest and increases dramatically under stimulation, very little is known about precise mechanisms controlling the intracellular distribution of Zn2+ and its variations during cardiac function. Recent studies are focused on molecular and cellular aspects of labile Zn2+ and its homeostasis in mammalian cells and growing evidence clarified the molecular mechanisms underlying Zn2+-diverse functions in the heart, leading to the discovery of novel physiological functions of labile Zn2+ in parallel to the discovery of subcellular localization of Zn2+-transporters in cardiomyocytes. Additionally, important experimental data suggest a central role of intracellular labile Zn2+ in excitation-contraction coupling in cardiomyocytes by shaping Ca2+ dynamics. Cellular labile Zn2+ is tightly regulated against its adverse effects through either Zn2+-transporters, Zn2+-binding molecules or Zn2+-sensors, and, therefore plays a critical role in cellular signaling pathways. The present review summarizes the current understanding of the physiological role of cellular labile Zn2+ distribution in cardiomyocytes and how a remodeling of cellular Zn2+-homeostasis can be important in proper cell function with Zn2+-transporters under hyperglycemia. We also emphasize the recent investigations on Zn2+-transporter functions from the standpoint of human heart health to diseases together with their clinical interest as target proteins in the heart under pathological condition, such as diabetes. PMID:29137144

Impact of Labile Zinc on Heart Function: From Physiology to Pathophysiology.

PubMed

Turan, Belma; Tuncay, Erkan

2017-11-12

Zinc plays an important role in biological systems as bound and histochemically reactive labile Zn 2+ . Although Zn 2+ concentration is in the nM range in cardiomyocytes at rest and increases dramatically under stimulation, very little is known about precise mechanisms controlling the intracellular distribution of Zn 2+ and its variations during cardiac function. Recent studies are focused on molecular and cellular aspects of labile Zn 2+ and its homeostasis in mammalian cells and growing evidence clarified the molecular mechanisms underlying Zn 2+ -diverse functions in the heart, leading to the discovery of novel physiological functions of labile Zn 2+ in parallel to the discovery of subcellular localization of Zn 2+ -transporters in cardiomyocytes. Additionally, important experimental data suggest a central role of intracellular labile Zn 2+ in excitation-contraction coupling in cardiomyocytes by shaping Ca 2+ dynamics. Cellular labile Zn 2+ is tightly regulated against its adverse effects through either Zn 2+ -transporters, Zn 2+ -binding molecules or Zn 2+ -sensors, and, therefore plays a critical role in cellular signaling pathways. The present review summarizes the current understanding of the physiological role of cellular labile Zn 2+ distribution in cardiomyocytes and how a remodeling of cellular Zn 2+ -homeostasis can be important in proper cell function with Zn 2+ -transporters under hyperglycemia. We also emphasize the recent investigations on Zn 2+ -transporter functions from the standpoint of human heart health to diseases together with their clinical interest as target proteins in the heart under pathological condition, such as diabetes.

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.

A stoichiometric organic matter decomposition model in a chemostat culture.

PubMed

Kong, Jude D; Salceanu, Paul; Wang, Hao

2018-02-01

Biodegradation, the disintegration of organic matter by microorganism, is essential for the cycling of environmental organic matter. Understanding and predicting the dynamics of this biodegradation have increasingly gained attention from the industries and government regulators. Since changes in environmental organic matter are strenuous to measure, mathematical models are essential in understanding and predicting the dynamics of organic matters. Empirical evidence suggests that grazers' preying activity on microorganism helps to facilitate biodegradation. In this paper, we formulate and investigate a stoichiometry-based organic matter decomposition model in a chemostat culture that incorporates the dynamics of grazers. We determine the criteria for the uniform persistence and extinction of the species and chemicals. Our results show that (1) if at the unique internal steady state, the per capita growth rate of bacteria is greater than the sum of the bacteria's death and dilution rates, then the bacteria will persist uniformly; (2) if in addition to this, (a) the grazers' per capita growth rate is greater than the sum of the dilution rate and grazers' death rate, and (b) the death rate of bacteria is less than some threshold, then the grazers will persist uniformly. These conditions can be achieved simultaneously if there are sufficient resources in the feed bottle. As opposed to the microcosm decomposition models' results, in a chemostat culture, chemicals always persist. Besides the transcritical bifurcation observed in microcosm models, our chemostat model exhibits Hopf bifurcation and Rosenzweig's paradox of enrichment phenomenon. Our sensitivity analysis suggests that the most effective way to facilitate degradation is to decrease the dilution rate.

Elucidating Microbial Species-Specific Effects on Organic Matter Transformation in Marine Sediments

NASA Astrophysics Data System (ADS)

Mahmoudi, N.; Enke, T. N.; Beaupre, S. R.; Teske, A.; Cordero, O. X.; Pearson, A.

2017-12-01

Microbial transformation and decomposition of organic matter in sediments constitutes one of the largest fluxes of carbon in marine environments. Mineralization of sedimentary organic matter by microorganisms results in selective degradation such that bioavailable or accessible compounds are rapidly metabolized while more recalcitrant, complex compounds are preserved and buried in sediment. Recent studies have found that the ability to use different carbon sources appears to vary among microorganisms, suggesting that the availability of certain pools of carbon can be specific to the taxa that utilize the pool. This implies that organic matter mineralization in marine environments may depend on the metabolic potential of the microbial populations that are present and active. The goal of our study was to investigate the extent to which organic matter availability and transformation may be species-specific using sediment from Guaymas Basin (Gulf of California). We carried out time-series incubations using bacterial isolates and sterilized sediment in the IsoCaRB system which allowed us to measure the production rates and natural isotopic signatures (δ13C and Δ14C) of microbially-respired CO2. Separate incubations using two different marine bacterial isolates (Vibrio sp. and Pseudoalteromonas sp.) and sterilized Guaymas Basin sediment under oxic conditions showed that the rate and total quantity of organic matter metabolized by these two species differs. Approximately twice as much CO2 was collected during the Vibrio sp. incubation compared to the Pseudoalteromonas sp. incubation. Moreover, the rate at which organic matter was metabolized by the Vibrio sp. was much higher than the Pseudoalteromonas sp. indicating the intrinsic availability of organic matter in sediments may depend on the species that is present and active. Isotopic analyses of microbially respired CO2 will be used to constrain the type and age of organic matter that is accessible to each species

New Approaches in Soil Organic Matter Fluorescence; A Solid Phase Fluorescence Approach

NASA Astrophysics Data System (ADS)

Bowman, M. M.; Sanclements, M.; McKnight, D. M.

2017-12-01

Fluorescence spectroscopy is a well-established technique to investigate the composition of organic matter in aquatic systems and is increasingly applied to soil organic matter (SOM). Current methods require that SOM be extracted into a liquid prior to analysis by fluorescence spectroscopy. Soil extractions introduce an additional layer of complexity as the composition of the organic matter dissolved into solution varies based upon the selected extractant. Water is one of the most commonly used extractant, but only extracts the water-soluble fraction of the SOM with the insoluble soil organic matter fluorescence remaining in the soil matrix. We propose the use of solid phase fluorescence on whole soils as a potential tool to look at the composition of organic matter without the extraction bias and gain a more complete understand of the potential for fluorescence as a tool in terrestrial studies. To date, the limited applications of solid phase fluorescence have ranged from food and agriculture to pharmaceutical with no clearly defined methods and limitations available. We are aware of no other studies that use solid phase fluorescence and thus no clear methods to look at SOM across a diverse set of soil types and ecosystems. With this new approach to fluorescence spectroscopy there are new challenges, such as blank correction, inner filter effect corrections, and sample preparation. This work outlines a novel method for analyzing soil organic matter using solid phase fluorescence across a wide range of soils collected from the National Ecological Observatory Network (NEON) eco-domains. This method has shown that organic matter content in soils must be diluted to 2% to reduce backscattering and oversaturation of the detector in forested soils. In mineral horizons (A) there is observed quenching of the humic-like organic matter, which is likely a result of organo-mineral complexation. Finally, we present preliminary comparisons between solid and liquid phase

Organic matter preserved in 3-billion-year-old mudstones at Gale crater, Mars

NASA Astrophysics Data System (ADS)

Eigenbrode, Jennifer L.; Summons, Roger E.; Steele, Andrew; Freissinet, Caroline; Millan, Maëva; Navarro-González, Rafael; Sutter, Brad; McAdam, Amy C.; Franz, Heather B.; Glavin, Daniel P.; Archer, Paul D.; Mahaffy, Paul R.; Conrad, Pamela G.; Hurowitz, Joel A.; Grotzinger, John P.; Gupta, Sanjeev; Ming, Doug W.; Sumner, Dawn Y.; Szopa, Cyril; Malespin, Charles; Buch, Arnaud; Coll, Patrice

2018-06-01

Establishing the presence and state of organic matter, including its possible biosignatures, in martian materials has been an elusive quest, despite limited reports of the existence of organic matter on Mars. We report the in situ detection of organic matter preserved in lacustrine mudstones at the base of the ~3.5-billion-year-old Murray formation at Pahrump Hills, Gale crater, by the Sample Analysis at Mars instrument suite onboard the Curiosity rover. Diverse pyrolysis products, including thiophenic, aromatic, and aliphatic compounds released at high temperatures (500° to 820°C), were directly detected by evolved gas analysis. Thiophenes were also observed by gas chromatography–mass spectrometry. Their presence suggests that sulfurization aided organic matter preservation. At least 50 nanomoles of organic carbon persists, probably as macromolecules containing 5% carbon as organic sulfur molecules.

DNA lability induced by nimustine and ramustine in rat glioma cells.

PubMed Central

Mineura, K; Fushimi, S; Itoh, Y; Kowada, M

1988-01-01

The DNA labile sites induced by two nitrosoureas, nimustine (ACNU) and ramustine (MCNU) synthesised in Japan, have been examined in highly reiterated DNA sequences of rat glioma cells. Reiterated fragments of 167 and 203 base pairs (bp), obtained after Hind III and Hae III restriction endonuclease digestion of rat glioma cells DNA, were used as target DNA sequences to determine the labile sites. In vitro reaction with ACNU and MCNU resulted in scission products corresponding to the locations of guanine. Subsequent piperidine hydrolysis produced more frequent breaks of the phosphodiester bonds at guanine positions, thus forming alkali-labile sites. Images PMID:3236017

Organic nitrogen storage in mineral soil: Implications for policy and management.

PubMed

Bingham, Andrew H; Cotrufo, M Francesca

2016-05-01

Nitrogen is one of the most important ecosystem nutrients and often its availability limits net primary production as well as stabilization of soil organic matter. The long-term storage of nitrogen-containing organic matter in soils was classically attributed to chemical complexity of plant and microbial residues that retarded microbial degradation. Recent advances have revised this framework, with the understanding that persistent soil organic matter consists largely of chemically labile, microbially processed organic compounds. Chemical bonding to minerals and physical protection in aggregates are more important to long-term (i.e., centuries to millennia) preservation of these organic compounds that contain the bulk of soil nitrogen rather than molecular complexity, with the exception of nitrogen in pyrogenic organic matter. This review examines for the first time the factors and mechanisms at each stage of movement into long-term storage that influence the sequestration of organic nitrogen in the mineral soil of natural temperate ecosystems. Because the factors which govern persistence are different under this newly accepted paradigm we examine the policy and management implications that are altered, such as critical load considerations, nitrogen saturation and mitigation consequences. Finally, it emphasizes how essential it is for this important but underappreciated pool to be better quantified and incorporated into policy and management decisions, especially given the lack of evidence for many soils having a finite capacity to sequester nitrogen. Published by Elsevier B.V.

Measuring the decomposition of organic carbon sequestered by salt marsh sediment

NASA Astrophysics Data System (ADS)

Light, T.; Mctigue, N.; Currin, C.

2016-12-01

As atmospheric carbon dioxide concentrations continue to rise, salt marshes are increasingly being recognized as a natural carbon sink, for large amounts of organic carbon are sequestered by salt marsh sediments. However, little is known regarding the fate of this "blue carbon" after salt marsh sediment is disturbed via erosion or lost due to sea level rise. This investigation explored novel methodologies for determining the lability of carbon sequestered by salt marsh sediment. Sediment cores were collected from a Spartina alterniflora-dominated marsh in Camp Lejeune, NC, and elemental analysis revealed that the upper 76 cm of sediment at the site contains a total carbon stock of 28.4 kg /m2. Sediment ranging from 251-545 years old, as determined through radiocarbon dating, was incubated under sub-aerial and aqueous conditions for 18 days and 25 days respectively. Carbon dioxide flux measurements revealed that shallower sediment organic matter decomposed more rapidly than deeper sediment in sub-aerial incubations, but decomposition was fairly slow in both treatments. No significant organic matter decomposition was observed in the aqueous incubations, as revealed by analyses of organic carbon remaining after the incubation period. The aqueous incubation included a treatment that had been "primed" with highly labile yeast extract, but no significant priming effect was observed over 25 days. While further investigation on the fate of this sediment carbon is needed, these preliminary findings indicate that salt marshes facilitate long-term carbon sequestration even after disturbances. This in turn supports the argument for mitigating anthropogenic carbon dioxide emissions through salt marsh restoration, and supports a policy of preserving and conserving coastal wetlands for this valuable ecosystem service.

Impacts of heterogeneous organic matter on phenanthrene sorption--Equilibrium and kinetic studies with aquifer material

USGS Publications Warehouse

Karapanagioti, Hrissi K.; Kleineidam, Sybille; Sabatini, David A.; Grathwohl, Peter; Ligouis, Bertrand

2000-01-01

Sediment organic matter heterogeneity in sediments is shown to impact the sorption behavior of contaminants. We investigated the sorptive properties as well as the composition of organic matter in different subsamples (mainly grain size fractions) of the Canadian River Alluvium (CRA). Organic petrography was used as a new tool to describe and characterize the organic matter in the subsamples. The samples studied contained many different types of organic matter including bituminous coal particles. Differences in sorption behavior were explained based on these various types of organic matter. Subsamples containing predominately coaly, particulate organic matter showed the highest Koc, the highest nonlinearity of sorption isotherms and the slowest sorption kinetics. Soil subsamples with organic matter present as organic coatings around the quartz grains evidenced the lowest Koc, the most linear sorption isotherms and the fastest sorption kinetics, which was not limited by slow intraparticle diffusion. Due to the high sorption capacity of the coaly particles even when it is present as only a small fraction of the composite organic content (<3%) causes Koc values which are much higher than expected for soil organic matter (e.g. Koc − Kow relationships). The results show that the identification and quantification of the coaly particles within a sediment or soil sample is a prerequisite in order to understand or predict sorption behavior of organic pollutants.

SOM quality and phosphorus fractionation to evaluate degradation organic matter: implications for the restoration of soils after fire

NASA Astrophysics Data System (ADS)

Merino, Agustin; Fonturbel, Maria T.; Omil, Beatriz; Chávez-Vergara, Bruno; Fernandez, Cristina; Garcia-Oliva, Felipe; Vega, Jose A.

2016-04-01

The design of emergency treatment for the rehabilitation of fire-affected soils requires a quick diagnosis to assess the degree of degradation. For its implication in the erosion and subsequent evolution, the quality of soil organic matter (OM) plays a particularly important role. This paper presents a methodology that combines the visual recognition of the severity of soil burning with the use of simple analytical techniques to assess the degree of degradation of OM. The content and quality of the OM was evaluated in litter and mineral soils using thermogravimetry-differential scanning calorimetry (DSC-TG) spectroscopy, and the results were contrasted with 13C CP-MAS NMR. The types of methodologies were texted to assess the thermal analysis: a) the direct calculation of the Q areas related to three degrees of thermal stabilities: Q1 (200-375 °C; labil OM); Q2 (375-475 °C, recalcitrant OM); and Q3 (475-550 °C). b) deconvolution of DSC curves and calculation of each peak was expressed as a fraction of the total DSC curve area. Additionally, a P fractionation was done following the Hedley sequential extraction method. The severity levels visually showed different degrees of SOM degradation. Although the fire caused important SOM losses in moderate severities, changes in the quality of OM only occurred at higher severities. Besides, the labile organic P fraction decreased and the occluded inorganic P fraction increased in the high severity soils. These changes affect the OM processes such as hydrophobicity and erosion largely responsible for soil degradation post-fire. The strong correlations between the thermal parameters and NMR regions and derived measurements such as hydrophobicity and aromaticity show the usefulness of this technique as rapid diagnosis to assess the soil degradation.The marked loss of polysaccharide and transition to highly thermic-resistant compounds, visible in deconvoluted thermograms, which would explain the changes in microbial activity

In vivo bioluminescence imaging of labile iron accumulation in a murine model of Acinetobacter baumannii infection.

PubMed

Aron, Allegra T; Heffern, Marie C; Lonergan, Zachery R; Vander Wal, Mark N; Blank, Brian R; Spangler, Benjamin; Zhang, Yaofang; Park, Hyo Min; Stahl, Andreas; Renslo, Adam R; Skaar, Eric P; Chang, Christopher J

2017-11-28

Iron is an essential metal for all organisms, yet disruption of its homeostasis, particularly in labile forms that can contribute to oxidative stress, is connected to diseases ranging from infection to cancer to neurodegeneration. Iron deficiency is also among the most common nutritional deficiencies worldwide. To advance studies of iron in healthy and disease states, we now report the synthesis and characterization of iron-caged luciferin-1 (ICL-1), a bioluminescent probe that enables longitudinal monitoring of labile iron pools (LIPs) in living animals. ICL-1 utilizes a bioinspired endoperoxide trigger to release d-aminoluciferin for selective reactivity-based detection of Fe 2+ with metal and oxidation state specificity. The probe can detect physiological changes in labile Fe 2+ levels in live cells and mice experiencing iron deficiency or overload. Application of ICL-1 in a model of systemic bacterial infection reveals increased iron accumulation in infected tissues that accompany transcriptional changes consistent with elevations in both iron acquisition and retention. The ability to assess iron status in living animals provides a powerful technology for studying the contributions of iron metabolism to physiology and pathology.

Linking measurements of biodegradability, thermal stability and chemical composition to evaluate the effects of management on soil organic matter

NASA Astrophysics Data System (ADS)

Gregorich, Ed; Gillespie, Adam; Beare, Mike; Curtin, Denis; Sanei, Hamed; Yanni, Sandra

2015-04-01

The stability of soil organic matter (SOM) as it relates to resistance to microbial degradation has important implications for nutrient cycling, emission of greenhouse gases, and C sequestration. Hence, there is interest in developing new ways to accurately quantify and characterise the labile and stable forms of soil organic C. Our objectives in this study were to evaluate and describe relationships among the biodegradability, thermal stability and chemistry of SOM in soil under widely contrasting management regimes. Samples from the same soil under permanent pasture, an arable cropping rotation, and chemical fallow were fractionated (sand: 2000-50 μm; silt: 50-5 μm, and clay: < 5 μm). Biodegradability of the SOM in size fractions and whole soils was assessed in a laboratory mineralization study. The chemical composition of SOM was characterized by X-ray absorption near-edge structure (XANES) spectroscopy at the K-edge and its thermal stability was determined by analytical pyrolysis using a Rock-Eval pyrolyser. The mineralization bioassay showed that whole soils and soil fractions under fallow were less susceptible to biodegradation than other managements and that sand-associated organic matter was significantly more susceptible than that in the silt or clay fractions. Analysis by XANES showed accumulation of carboxylates and strong depletion of amides (protein) and aromatics in the fallow whole soil. Moreover, protein depletion was most significant in the sand fraction of the fallow soil. Sand fractions in fallow and cropped soils were, however, enriched in plant-derived phenols, aromatics and carboxylates compared to the sand fraction of pasture soils. In contrast, ketones, which have been identified as products of microbially-processed organic matter, were slightly enriched in the silt fraction of the pasture soil. These data suggest reduced inputs and cropping restrict the decomposition of plant residues and, without supplemental N additions, protein-N in

Marine methane paradox explained by bacterial degradation of dissolved organic matter

NASA Astrophysics Data System (ADS)

Repeta, Daniel J.; Ferrón, Sara; Sosa, Oscar A.; Johnson, Carl G.; Repeta, Lucas D.; Acker, Marianne; Delong, Edward F.; Karl, David M.

2016-12-01

Biogenic methane is widely thought to be a product of archaeal methanogenesis, an anaerobic process that is inhibited or outcompeted by the presence of oxygen and sulfate. Yet a large fraction of marine methane delivered to the atmosphere is produced in high-sulfate, fully oxygenated surface waters that have methane concentrations above atmospheric equilibrium values, an unexplained phenomenon referred to as the marine methane paradox. Here we use nuclear magnetic resonance spectroscopy to show that polysaccharide esters of three phosphonic acids are important constituents of dissolved organic matter in seawater from the North Pacific. In seawater and pure culture incubations, bacterial degradation of these dissolved organic matter phosphonates in the presence of oxygen releases methane, ethylene and propylene gas. Moreover, we found that in mutants of a methane-producing marine bacterium, Pseudomonas stutzeri, disrupted in the C-P lyase phosphonate degradation pathway, methanogenesis was also disabled, indicating that the C-P lyase pathway can catalyse methane production from marine dissolved organic matter. Finally, the carbon stable isotope ratio of methane emitted during our incubations agrees well with anomalous isotopic characteristics of seawater methane. We estimate that daily cycling of only about 0.25% of the organic matter phosphonate inventory would support the entire atmospheric methane flux at our study site. We conclude that aerobic bacterial degradation of phosphonate esters in dissolved organic matter may explain the marine methane paradox.

Temperature Responses of Soil Organic Matter Components With Varying Recalcitrance

NASA Astrophysics Data System (ADS)

Simpson, M. J.; Feng, X.

2007-12-01

The response of soil organic matter (SOM) to global warming remains unclear partly due to the chemical heterogeneity of SOM composition. In this study, the decomposition of SOM from two grassland soils was investigated in a one-year laboratory incubation at six different temperatures. SOM was separated into solvent- extractable compounds, suberin- and cutin-derived compounds, and lignin monomers by solvent extraction, base hydrolysis, and CuO oxidation, respectively. These SOM components had distinct chemical structures and recalcitrance, and their decomposition was fitted by a two-pool exponential decay model. The stability of SOM components was assessed using geochemical parameters and kinetic parameters derived from model fitting. Lignin monomers exhibited much lower decay rates than solvent-extractable compounds and a relatively low percentage of lignin monomers partitioned into the labile SOM pool, which confirmed the generally accepted recalcitrance of lignin compounds. Suberin- and cutin-derived compounds had a poor fitting for the exponential decay model, and their recalcitrance was shown by the geochemical degradation parameter which stabilized during the incubation. The aliphatic components of suberin degraded faster than cutin-derived compounds, suggesting that cutin-derived compounds in the soil may be at a higher stage of degradation than suberin- derived compounds. The temperature sensitivity of decomposition, expressed as Q10, was derived from the relationship between temperature and SOM decay rates. SOM components exhibited varying temperature responses and the decomposition of the recalcitrant lignin monomers had much higher Q10 values than soil respiration or the solvent-extractable compounds decomposition. Our study shows that the decomposition of recalcitrant SOM is highly sensitive to temperature, more so than bulk soil mineralization. This observation suggests a potential acceleration in the degradation of the recalcitrant SOM pool with global

Test procedure for determining organic matter content in soils : UV-VIS method.

DOT National Transportation Integrated Search

2010-11-01

The Texas Department of Transportation has been having problems with organic matter in soils that they : stabilize for use as subgrade layers in road construction. The organic matter reduces the effectiveness of : common soil additives (lime/cement) ...

Particulate Organic Matter Distribution along the Lower Amazon River: Addressing Aquatic Ecology Concepts Using Fatty Acids

PubMed Central

Mortillaro, Jean-Michel; Rigal, François; Rybarczyk, Hervé; Bernardes, Marcelo; Abril, Gwenaël; Meziane, Tarik

2012-01-01

One of the greatest challenges in understanding the Amazon basin functioning is to ascertain the role played by floodplains in the organic matter (OM) cycle, crucial for a large spectrum of ecological mechanisms. Fatty acids (FAs) were combined with environmental descriptors and analyzed through multivariate and spatial tools (asymmetric eigenvector maps, AEM and principal coordinates of neighbor matrices, PCNM). This challenge allowed investigating the distribution of suspended particulate organic matter (SPOM), in order to trace its seasonal origin and quality, along a 800 km section of the Amazon river-floodplain system. Statistical analysis confirmed that large amounts of saturated FAs (15:0, 18:0, 24:0, 25:0 and 26:0), an indication of refractory OM, were concomitantly recorded with high pCO2 in rivers, during the high water season (HW). Contrastingly, FAs marker which may be attributed in this ecosystem to aquatic plants (18:2ω6 and 18:3ω3) and cyanobacteria (16:1ω7), were correlated with higher O2, chlorophyll a and pheopigments in floodplains, due to a high primary production during low waters (LW). Decreasing concentrations of unsaturated FAs, that characterize labile OM, were recorded during HW, from upstream to downstream. Furthermore, using PCNM and AEM spatial methods, FAs compositions of SPOM displayed an upstream-downstream gradient during HW, which was attributed to OM retention and the extent of flooded forest in floodplains. Discrimination of OM quality between the Amazon River and floodplains corroborate higher autotrophic production in the latter and transfer of OM to rivers at LW season. Together, these gradients demonstrate the validity of FAs as predictors of spatial and temporal changes in OM quality. These spatial and temporal trends are explained by 1) downstream change in landscape morphology as predicted by the River Continuum Concept; 2) enhanced primary production during LW when the water level decreased and its residence time

Tracing organic matter sources in a tropical lagoon of the Caribbean Sea

NASA Astrophysics Data System (ADS)

Alonso-Hernández, Carlos M.; Garcia-Moya, Alejandro; Tolosa, Imma; Diaz-Asencio, Misael; Corcho-Alvarado, Jose Antonio; Morera-Gomez, Yasser; Fanelli, Emanuela

2017-09-01

The natural protected lagoon of Guanaroca, located between Cienfuegos Bay and the Arimao River, Cuba, has been heavily impacted by human-induced environmental changes over the past century. Sources of organic matter in the Guanaroca lagoon and concentrations of radioisotopes (210Pb, 226Ra, 137Cs and 239,240Pu), as tracers of anthropogenic impacts, were investigated in a 78 cm sediment core. Variations in total organic carbon (TOC), total nitrogen (TN), stable isotopic composition (δ13C and δ15N) and ratio of total organic carbon to total nitrogen (C/N) were analysed. On such a basis, environmental changes in the lagoon were revealed. Down core variation patterns of the parameters representing sources of organic matter were predominantly related to the impacts of human activities. Up to the nineteenth century, the principal sources of organic matter to sediments (more than 80%) were a mixing of terrestrial vascular plants ( 48%) and freshwater phytoplankton ( 8%), with minimal contribution from the marine component ( 16%). In the period 1900-1980, due to the strong influence of human activities in the catchment area, the water exchange capacity of the lagoon declined substantially, as indicated by the relatively high proportion of organic matter originated from human activities (58%). Since 1980, as a result of management actions in the protected area, the lagoon has regained gradually its capability to exchange freshwater, showing sources of organic matter similar to the natural conditions recorded previous to 1900, although an indication of human impact (treated sewage contributed for 26% to the organic matter in sediments) was still observed and further management measures would be required.

Soil organic matter content effects on dermal pesticide bioconcentration in American toads (Bufo americanus).

PubMed

Van Meter, Robin J; Glinski, Donna A; Henderson, W Matthew; Purucker, S Thomas

2016-11-01

Pesticides have been implicated as a major factor in global amphibian declines and may pose great risk to terrestrial phase amphibians moving to and from breeding ponds on agricultural landscapes. Dermal uptake from soil is known to occur in amphibians, but predicting pesticide availability and bioconcentration across soil types is not well understood. The present study was designed to compare uptake of 5 current-use pesticides (imidacloprid, atrazine, triadimefon, fipronil, and pendimethalin) in American toads (Bufo americanus) from exposure on soils with significant organic matter content differences (14.1% = high organic matter and 3.1% = low organic matter). We placed toads on high- or low-organic matter soil after applying individual current-use pesticides on the soil surface for an 8-h exposure duration. Whole body tissue homogenates and soils were extracted and analyzed using liquid chromatography-mass spectrometry to determine pesticide tissue and soil concentration, as well as bioconcentration factor in toads. Tissue concentrations were greater on the low-organic matter soil than the high-organic matter soil across all pesticides (average ± standard error; 1.23 ± 0.35 ppm and 0.78 ± 0.23 ppm, respectively), and bioconcentration was significantly higher for toads on the low-organic matter soil (analysis of covariance p = 0.002). Soil organic matter is known to play a significant role in the mobility of pesticides and bioavailability to living organisms. Agricultural soils typically have relatively lower organic matter content and serve as a functional habitat for amphibians. The potential for pesticide accumulation in amphibians moving throughout agricultural landscapes may be greater and should be considered in conservation and policy efforts. Environ Toxicol Chem 2016;35:2734-2741. © 2016 SETAC. © 2016 SETAC.

Differences in fluorescence characteristics and bioavailability of water-soluble organic matter (WSOM) in sediments and suspended solids in Lihu Lake, China.

PubMed

Wang, Wenwen; Wang, Shuhang; Jiang, Xia; Zheng, Binghui; Zhao, Li; Zhang, Bo; Chen, Junyi

2018-05-01

The spectral characteristics, spatial distribution, and bioavailability of water-soluble organic matter (WSOM) in suspended solids and surface sediments of Lihu Lake, China, were investigated through excitation-emission matrix spectra and parallel factor analysis. The average content of dissolved organic carbon (DOC) in the sediments reached 643.28 ± 58.34 mg C/kg and that in suspended solids was 714.87 ± 69.24 mg C/kg. The fluorescence intensity of WSOM totaled 90.87 ± 5.65 and 115.42 ± 8.02 RU/g for the sediments and suspended solids, respectively. The DOC and fluorescence intensity of the WSOM showed an increasing trend moving from the west to the east of the lake. The WSOM in sediments and suspended solids contained two humic-like (C1 and C2) and one tryptophan-like (C3) components. These components had different fluorescent peaks and relative proportions. In the sediments, the relative proportions of C1, C2, and C3 were 33.71% ± 0.71, 26.83% ± 0.68, and 39.50% ± 0.71%, respectively. Meanwhile, C1 (35.77 ± 0.84%), C2 (34.07 ± 0.61%), and C3 (30.16 ± 0.75%) had similar relative percentages in suspended solids. The sediments had a lower humification index (3.02 ± 0.08) than the suspended solids (4.04 ± 0.15). Exchangeable nitrogen for the sediments and suspended solids was dominated by exchangeable ammonium nitrogen and soluble organic nitrogen, respectively. WSOM plays an important role in migration and transformation of nitrogen in sediments and suspended solids. The sediment-derived WSOM exhibited higher lability and biological activity than did the suspended solid-derived WSOM. The relative ratio of the intensity of protein-like fluorescent component to that of the humic-like one can be used as a reference index to evaluate the lability and biological activity of WSOM in sediments and suspended solids.

The origin of organic matter in the Martian meteorite ALH84001.

PubMed

Becker, L; Popp, B; Rust, T; Bada, J L

1999-01-01

Stable carbon isotope measurements of the organic matter associated with the carbonate globules and the bulk matrix material in the ALH84001 Martian meteorite indicate that two distinct sources are present in the sample. The delta 13C values for the organic matter associated with the carbonate globules averaged -26% and is attributed to terrestrial contamination. In contrast, the delta 13C values for the organic matter associated with the bulk matrix material yielded a value of -15%. The only common carbon sources on the Earth that yield similar delta 13C values, other then some diagenetically altered marine carbonates, are C4 plants. A delta 13C value of -15%, on the other hand, is consistent with a kerogen-like component, the most ubiquitous form of organic matter found in carbonaceous chondrites such as the Murchison meteorite. Examination of the carbonate globules and bulk matrix material using laser desorption mass spectrometry (LDMS) indicates the presence of a high molecular weight organic component which appears to be extraterrestrial in origin, possibly derived from the exogenous delivery of meteoritic or cometary debris to the surface of Mars.

The origin of organic matter in the Martian meteorite ALH84001.

PubMed

Becker, L; Popp, B; Rust, T; Bada, J L

1999-03-30

Stable carbon isotope measurements of the organic matter associated with the carbonate globules and the bulk matrix material in the ALH84001 Martian meteorite indicate that two distinct sources are present in the sample. The delta 13C values for the organic matter associated with the carbonate globules averaged -26% and is attributed to terrestrial contamination. In contrast, the delta 13C values for the organic matter associated with the bulk matrix material yielded a value of -15%. The only common sources of carbon on the Earth that yield similar delta 13C values, other then some diagenetically altered marine carbonates, are C4 plants. A delta 13C value of -15%, on the other hand, is consistent with a kerogen-like component, the most ubiquitous form of organic matter found in carbonaceous chondrites such as the Murchison meteorite. Examination of the carbonate globules and bulk matrix material using laser desorption mass spectrometry (LDMS) indicates the presence of a high molecular weight organic component which appears to be extraterrestrial in origin, possibly derived from the exogenous delivery, of meteoritic or cometary debris to the surface of Mars.

Organic matter and the geotechnical properties of submarine sediments

NASA Astrophysics Data System (ADS)

Keller, George H.

1982-09-01

Continental slope deposits off Peru and Oregon where coastal upwelling is a pronounced oceanographic process possess significant concentrations of organic carbon. Geotechnical properties are altered to varying degrees by the organic matter. Organic matter absorbs water and causes clay-size particles to aggregate forming an open fabric. This causes unusually high water contents and plasticity and exceptionally low wet bulk densities. Some of these deposits show notable increases in shear strength, sensitivity and degree of apparent overconsolidation. Owing to the unique geotechnical properties, sediment stability characteristics are considered to be poor in situations of excess pore pressures. Failure appears to take the form of a fluidized flow somewhat similar to the quick clays of Scandinavia.

The evolution of organic matter along the lower Amazon River continuum - Óbidos to the ocean

NASA Astrophysics Data System (ADS)

Ward, N. D.; Keil, R. G.; Medeiros, P. M.; Brito, D.; Cunha, A.; Sawakuchi, H. O.; Moura, J. S.; Yager, P. L.; Krusche, A. V.; Richey, J. E.

2013-12-01

The influence of the Amazon River on global hydrologic and biogeochemical cycling is well recognized. The Amazon River provides roughly 16% of the global freshwater supply to the ocean and is a significant source of CO2 to the atmosphere, outgassing 0.5 Pg C y-1 to the atmosphere--a flux roughly equivalent to the amount of carbon 'sequestered' by the Amazon rainforest (Field et al, 1998; Richey et al., 2002; Malhi et al., 2008). However, much of our understanding of the flux of matter from the Amazon River into the Atlantic Ocean (and atmosphere) is limited to measurements made at and upstream of Óbidos, 900 km upstream from the actual river mouth. Further, there are few to no observations documenting the transformation of organic matter in a parcel of water as it travels downstream of Óbidos into the ocean. Here we explore the hydrological and biogeochemical evolution of the lower Amazon River continuum, from Óbidos to the Atlantic Ocean. A suite of dissolved and particulate organic matter (OM) parameters were measured during a series of five river expeditions with stations at Óbidos, the Tapajós tributary, the mouth of the Lago Grande de Curuai floodplain lake, both the north and south channels of the Amazon River mouth near Macapá, and the confluence of the Amazon and Tocantins Rivers near Belém. In addition to bulk carbon isotopic signatures, a suite of biomarkers including dissolved and particulate lignin-derived phenols were measured to trace the sources and degradation history of terrestrial vascular plant derived OM throughout the continuum. Dissolved and particulate lignin phenol concentrations both correlated positively with river discharge in the Amazon River mainstem, with variable export patterns from the tributaries and floodplains. As organic matter travels along the continuum it is degraded by microbial composition, fuelling gross respiration and CO2 outgassing. The flux of organic carbon to the ocean is chemically recalcitrant as a result of

Riverine transport of terrestrial organic matter to the North Catalan margin, NW Mediterranean Sea

NASA Astrophysics Data System (ADS)

Sanchez-Vidal, Anna; Higueras, Marina; Martí, Eugènia; Liquete, Camino; Calafat, Antoni; Kerhervé, Philippe; Canals, Miquel

2013-11-01

Rivers are the primary pathway for organic matter transport from the terrestrial to the marine environment and, thus, river fluxes are critical in regulating the quantity of terrestrial organic matter that reaches the coastal ecosystems. Hydrodynamic processes typical of the coastal zone can lead to the transport of terrestrial organic matter across the continental shelf and beyond. Such organic matter can eventually reach the deep margin and basin ecosystems. Riverine inputs of organic matter to the sea can be a significant food source to marine ecosystems contributing to carbon cycling in these ecosystems. In order to assess the marine carbon cycle it is essential to know the biogeochemical characteristics and temporal dynamics of the fluvial organic matter input discharged by rivers to the coastal zone. In this study we present a one and a half year long (November 2008 to May 2010) assessment on organic carbon (OC) and nitrogen (N) inputs from the three main rivers discharging into the North Catalan margin (Tordera, Ter and Fluvià, from south to north). Furthermore, we investigate the characteristics of the particulate organic matter discharged by these rivers by means of stable isotopic (δ13C and δ15N) and grain size analyses. We found that the hydrological regime of the rivers is a relevant factor in regulating the quantity and mediating the quality of organic matter inputs to the North Catalan margin. Overall, the three main rivers discharging into the study area deliver 1266 and 159 tonnes of terrestrial OC and N per year, respectively, to the coastal zone. Most of the OC and N load is transported during floods, which indicates that the Mediterranean climate of the area, with a strong seasonal contrast in precipitation, determines the timing of the main inputs of OC and N to the sea. Therefore, the annual OC and N load experiences a high temporal variability associated to the number and magnitude of floods with in each hydrological year. In addition, we

Repeated applications of compost and manure mainly affect the size and chemical nature of particulate organic matter in a loamy soil after 8 years

NASA Astrophysics Data System (ADS)

Peltre, Clement; Dignac, Marie-France; Doublet, Jeremy; Plante, Alain; Houot, Sabine

2013-04-01

Land application of exogenous organic matter (EOM) of residual origin can help to maintain or increase soil organic carbon (SOC) stocks. However, it remains necessary to quantify and predict the soil C accumulation and to determine under which form the C accumulates. Changes to the chemical composition of soil organic matter (SOM) after repeated applications of composts and farmyard manure were investigated in a field experiment (Qualiagro experiment, Ile-de-France) after 8 years of applications of green waste and sludge compost (GWS), municipal solid waste compost (MSW), biowaste compost (BIOW) or farmyard manure (FYM). The soil was fractionated into particulate organic matter >50 µm (POM), a heavy fraction >50 µm and a 0-50 µm fraction demineralized with hydrofluoric acid (HF). Repeated EOM applications significantly increased total SOC stocks, the C amount in the POM fraction and to a less extent in the 0-50 µm fraction compared to the reference treatment. Compost applications accumulated C preferentially under the form of coarse organic matter of size >50 µm, whereas the FYM accumulated similar C proportions of size >50 µm and 0-50 µm, which was attributed to the presence in the FYM of a fraction of labile C stimulating microbial activity and producing humified by-products together with a fraction of stabilized C directly alimenting the humified fraction of SOC. Pyrolysis-GC/MS and DRIFT spectroscopy revealed enrichment in lignin in the POM fractions of amended soils with GWS, BIOW and FYM. In the soil receiving MSW compost, the pyrolysate of the POM fraction revealed the presence of plastics originating from the MSW compost. A lower C mineralization during laboratory incubation was found for the POM fractions of amended soils compared with the POM from reference soil. This feature was related to a lower ratio of (furfural+acetic acid) / pyrole pyrolysis products in POM of amended vs. reference plots, indicating a higher degree of recalcitrance.. The POM

Effect of organic matter on CO(2) hydrate phase equilibrium in phyllosilicate suspensions.

PubMed

Park, Taehyung; Kyung, Daeseung; Lee, Woojin

2014-06-17

In this study, we examined various CO2 hydrate phase equilibria under diverse, heterogeneous conditions, to provide basic knowledge for successful ocean CO2 sequestration in offshore marine sediments. We investigated the effect of geochemical factors on CO2 hydrate phase equilibrium. The three-phase (liquid-hydrate-vapor) equilibrium of CO2 hydrate in the presence of (i) organic matter (glycine, glucose, and urea), (ii) phyllosilicates [illite, kaolinite, and Na-montmorillonite (Na-MMT)], and (iii) mixtures of them was measured in the ranges of 274.5-277.0 K and 14-22 bar. Organic matter inhibited the phase equilibrium of CO2 hydrate by association with water molecules. The inhibition effect decreased in the order: urea < glycine < glucose. Illite and kaolinite (unexpandable clays) barely affected the CO2 hydrate phase equilibrium, while Na-MMT (expandable clay) affected the phase equilibrium because of its interlayer cations. The CO2 hydrate equilibrium conditions, in the illite and kaolinite suspensions with organic matter, were very similar to those in the aqueous organic matter solutions. However, the equilibrium condition in the Na-MMT suspension with organic matter changed because of reduction of its inhibition effect by intercalated organic matter associated with cations in the Na-MMT interlayer.

Maternal emotion socialization differentially predicts third-grade children's emotion regulation and lability.

PubMed

Rogers, Megan L; Halberstadt, Amy G; Castro, Vanessa L; MacCormack, Jennifer K; Garrett-Peters, Patricia

2016-03-01

Numerous parental emotion socialization factors have been implicated as direct and indirect contributors to the development of children's emotional competence. To date, however, no study has combined parents' emotion-related beliefs, behaviors, and regulation strategies in one model to assess their cumulative-as well as unique-contributions to children's emotion regulation. We considered the 2 components that have recently been distinguished: emotion regulation and emotional lability. We predicted that mothers' beliefs about the value of and contempt for children's emotions, mothers' supportive and nonsupportive reactions to their children's emotions, as well as mothers' use of cognitive reappraisal and suppression of their own emotions would each contribute unique variance to their children's emotion regulation and lability, as assessed by children's teachers. The study sample consisted of an ethnically and socioeconomically diverse group of 165 mothers and their third-grade children. Different patterns emerged for regulation and lability: Controlling for family income, child gender, and ethnicity, only mothers' lack of suppression as a regulatory strategy predicted greater emotion regulation in children, whereas mothers' valuing of children's emotions, mothers' lack of contempt for children's emotions, mothers' use of cognitive reappraisal to reinterpret events, and mothers' lack of emotional suppression predicted less lability in children. These findings support the divergence of emotion regulation and lability as constructs and indicate that, during middle childhood, children's lability may be substantially and uniquely affected by multiple forms of parental socialization. (c) 2016 APA, all rights reserved).

Non-invasive localization of organic matter in soil aggregates using SR-μCT

NASA Astrophysics Data System (ADS)

Peth, Stephan; Mordhorst, Anneka; Chenu, Claire; Uteau Puschmann, Daniel; Garnier, Patricia; Nunan, Naoise; Pot, Valerie; Beckmann, Felix; Ogurreck, Malte

2014-05-01

Knowledge of the location of soil organic matter (SOM) and its spatial association to soil structure is an important step in improving modeling approaches for simulating organic matter turnover processes. Advanced models for carbon mineralization are able to account for the 3D distribution of SOM which is assumed to influence mineralisation. However, their application is still limited by the fact that no method exists to non-invasively determine the 3D spatial distribution of SOM in structured soils. SR-based X-ray microtomography (SR-µCT) is an advanced and promising tool in gaining knowledge on the 3-dimensional organization of soil phases (minerals, organic matter, water, air) which on a voxel level could be implemented into spatially explicit models. However, since the contrast of linear attenuation coefficients of soil organic matter on the one hand and mineral components and water on the other hand are relatively low, especially when materials are finely dispersed, organic matter within the soil pore space is often not resolved in ordinary X-ray absorption contrast imaging. To circumvent this problem we have developed a staining procedure for organic matter using Osmium-tetroxide since Osmium is an element with an absorption edge at a higher X-ray energy level. Osmium is known from transmission electron microscopy analysis (TEM) to stain organic matter specifically and irreversibly while having an absorption edge at approximately 74 keV. We report on the application of a novel Osmium vapor staining method to analyze differences in organic matter content and identify small scale spatial distribution of SOM in soil aggregates. To achieve this we have taken soil aggregate samples (6-8 mm across) obtained from arable soils differing in soil management. Aggregate samples were investigated by synchrotron-based X-ray microtomography (SR-µCT) after staining the sample with Osmium-tetroxide (OsO4) vapor. We utilized the monochromatic X-ray beam to locate osmium

Evidence for Changes in 81PIWild 2 Organic Matter Since Collection and Comparison of 82PIWild 2 and IDP Organic Matter to Access the Thermal Effects of Aerogel Capture

NASA Technical Reports Server (NTRS)

Wirick, S.; Flynn, G. J.; Keller, L.; Messenger, Nakamura; Sandford, S. A.; Zolensky, M. E.; Peltzer, C.; Jacobsen, C.

2009-01-01

NASA s Stardust spacecraft collected cometary material during its passage through the dust coma of comet 81P/Wild 2 on January 2nd, 2004 and delivered this material to Earth on January 15th 2006. The first fragment we analyzed during the preliminary examination was partially vaporized by the X-ray beam. The carbonaceous material that survived was re-analysis approx.2 months later and the carbon spectrum for this material had significantly changed from what we first observed.. We have observed similar changes to the carbonaceous matter in some interplanetary dust particles ( IDPs). Some of the 81P/Wild 2 organic matter volatilized upon impact with the aerogel as observed using IR spectroscopy where IR spectra were collected several mms away from sample tracks [1]. The time-temperature profile experienced by any particular 81P/Wild 2 grain during aerogel capture is not known, although Brownlee, et al. suggest that fine-grained materials, <1 micron in size, fragmented and then partially vaporized during collection, while particles much larger then 1 micron in size were captured intact [2]. Nearly all organic matter is subject to thermal alteration. To assess the heating and alteration experienced by the 81P/Wild 2 organic matter during capture we are comparing 81P/Wild2 organic matter with IDP organic matter where we have evidence of heating in the IDP [3,4].

Influence of soil organic matter composition on the partition of organic compounds

USGS Publications Warehouse

Rutherford, D.W.; Chiou, C.T.; Klle, D.E.

1992-01-01

The sorption at room temperature of benzene and carbon tetrachloride from water on three high-organic-content soils (muck, peat, and extracted peat) and on cellulose was determined in order to evaluate the effect of sorbent polarity on the solute partition coefficients. The isotherms are highly linear for both solutes on all the organic matter samples, which is consistent with a partition model. For both solutes, the extracted peat shows the greatest sorption capacity while the cellulose shows the lowest capacity; the difference correlates with the polar-to-nonpolar group ratio [(O + N)/C] of the sorbent samples. The relative increase of solute partition coefficient (Kom) with a decrease of sample polar content is similar for both solutes, and the limiting sorption capacity on a given organic matter sample is comparable between the solutes. This observation suggests that one can estimate the polarity effect of a sample of soil organic matter (SOM) on Kom of various nonpolar solutes by determining the partition coefficient of single nonpolar solute when compositional analysis of the SOM is not available. The observed dependence of Kom on sample polarity is used to account for the variation of Kom values of individual compounds on different soils that results from change in the polar group content of SOM. On the assumption that the carbon content of SOM in "ordinary soils" is 53-63%, the calculated variation of Kom is a factor of ???3. This value is in agreement with the limit of variation of most Kom data with soils of relatively high SOM contents.

Effect of organic matter properties, clay mineral type and thermal maturity on gas adsorption in organic-rich shale systems