Importance of clay size minerals for Fe(III) respiration in a petroleum-contaminated aquifer

USGS Publications Warehouse

Shelobolina, Evgenya S.; Anderson, Robert T.; Vodyanitskii, Yury N.; Sivtsov, Anatolii V.; Yuretich, Richard; Lovely, Derek R.

2004-01-01

The availability of Fe(III)-bearing minerals for dissimilatory Fe(III) reduction was evaluated in sediments from a petroleum-contaminated sandy aquifer near Bemidji, Minnesota (USA). First, the sediments from a contaminated area of the aquifer, in which Fe(III) reduction was the predominant terminal electron accepting process, were compared with sediments from a nearby, uncontaminated site. Data from 0.5 m HCl extraction of different size fractions of the sediments revealed that the clay size fraction contributed a significant portion of the ‘bio-available’ Fe(III) in the background sediment and was the most depleted in ‘bio-available’ Fe(III) in the iron-reducing sediment. Analytical transmission electron microscopy (TEM) revealed the disappearance of thermodynamically unstable Fe(III) and Mn(IV) hydroxides (ferrihydrite and Fe vernadite), as well as a decrease in the abundance of goethite and lepidocrocite in the clay size fraction from the contaminated sediment. TEM observations and X-ray diffraction examination did not provide strong evidence of Fe(III)-reduction-related changes within another potential source of ‘bio-available’ Fe(III) in the clay size fraction – ferruginous phyllosilicates. However, further testing in the laboratory with sediments from the methanogenic portion of the aquifer that were depleted in microbially reducible Fe(III) revealed the potential for microbial reduction of Fe(III) associated with phyllosilicates. Addition of a clay size fraction from the uncontaminated sediment, as well as Fe(III)-coated kaolin and ferruginous nontronite SWa-1, as sources of poorly crystalline Fe(III) hydroxides and structural iron of phyllosilicates respectively, lowered steady-state hydrogen concentrations consistent with a stimulation of Fe(III) reduction in laboratory incubations of methanogenic sediments. There was no change in hydrogen concentration when non-ferruginous clays or no minerals were added. This demonstrated that Fe(III)-bearing clay size minerals were essential for microbial Fe(III) reduction and suggested that both potential sources of ‘bio-available’ Fe(III) in the clay size fraction, poorly crystalline Fe(III) hydroxides and structural Fe(III) of phyllosilicates, were important sources of electron acceptor for indigenous iron-reducing microorganisms in this aquifer.

Biogeochemical factors influencing net mercury methylation in contaminated freshwater sediments from the St. Lawrence River in Cornwall, Ontario, Canada.

PubMed

Avramescu, Mary-Luyza; Yumvihoze, Emmanuel; Hintelmann, Holger; Ridal, Jeff; Fortin, Danielle; Lean, David R S

2011-02-01

The activity of various anaerobic microbes, including sulfate reducers (SRB), iron reducers (FeRP) and methanogens (MPA) has been linked to mercury methylation in aquatic systems, although the relative importance of each microbial group in the overall process is poorly understood in natural sediments. The present study focused on the biogeochemical factors (i.e. the relative importance of various groups of anaerobic microbes (FeRP, SRB, and MPA) that affect net monomethylmercury (MMHg) formation in contaminated sediments of the St. Lawrence River (SRL) near Cornwall (Zone 1), Ontario, Canada. Methylation and demethylation potentials were measured separately by using isotope-enriched mercury species ((200)Hg(2+) and MM(199)Hg(+)) in sediment microcosms treated with specific microbial inhibitors. Sediments were sampled and incubated in the dark at room temperature in an anaerobic chamber for 96h. The potential methylation rate constants (K(m)) and demethylation rates (K(d)) were found to differ significantly between microcosms. The MPA-inhibited microcosm had the highest potential methylation rate constant (0.016d(-1)), whereas the two SRB-inhibited microcosms had comparable potential methylation rate constants (0.003d(-1) and 0.002d(-1), respectively). The inhibition of methanogens stimulated net methylation by inhibiting demethylationand by stimulating methylation along with SRB activity. The inhibition of both methanogens and SRB was found to enhance the iron reduction rates but did not completely stop MMHg production. The strong positive correlation between K(m) and Sulfate Reduction Rates (SRR) and between K(d) and Methane Production Rates (MPR) supports the involvement of SRB in Hg methylation and MPA in MMHg demethylation in the sediments. In contrast, the strong negative correlation between K(d) and Iron Reduction Rates (FeRR) shows that the increase in FeRR corresponds to a decrease in demethylation, indicating that iron reduction may influence net methylation in the SLR sediments by decreasing demethylation rather than favouring methylation. Copyright © 2010 Elsevier B.V. All rights reserved.

Manganese inhibition of microbial iron reduction in anaerobic sediments

USGS Publications Warehouse

Lovley, D.R.; Phillips, E.J.P.

1988-01-01

Potential mechanisms for the lack of Fe(II) accumulation in Mn(IV)-containing anaerobic sediments were investigated. The addition of Mn(IV) to sediments in which Fe(II) reduction was the terminal electron-accepting process removed all the pore-water Fe(II), completely inhibited net Fe(III) reduction, and stimulated Mn(IV) reduction. Results demonstrate that preferential reduction of Mn(IV) by FE(III)-reducing bacteria cannot completely explain the lack of Fe(II) accumulation in anaerobic, Mn(IV)-containing sediments, and indicate that Mn(IV) oxidation of Fe(II) is the mechanism that ultimately prevents Fe(II) accumulation. -Authors

Phosphorus losses from agricultural land to natural waters are reduced by immobilization in iron-rich sediments of drainage ditches.

PubMed

Baken, Stijn; Verbeeck, Mieke; Verheyen, Dries; Diels, Jan; Smolders, Erik

2015-03-15

Redox reactions involving iron (Fe) strongly affect the mobility of phosphorus (P) and its migration from agricultural land to freshwater. We studied the transfer of P from groundwater to open drainage ditches in an area where, due to Fe(II) rich groundwater, the sediments of these ditches contain accumulated Fe oxyhydroxides. The average P concentrations in the groundwater feeding two out of three studied drainage ditches exceeded environmental limits for freshwaters by factors 11 and 16, but after passing through the Fe-rich sediments, the P concentrations in the ditch water were below these limits. In order to identify the processes which govern Fe and P mobility in these systems, we used diffusive equilibration in thin films (DET) to measure the vertical concentration profiles of P and Fe in the sediment pore water and in the ditchwater. The Fe concentrations in the sediment pore water ranged between 10 and 200 mg L(-1) and exceeded those in the inflowing groundwater by approximately one order of magnitude, due to reductive dissolution of Fe oxyhydroxides in the sediment. The dissolved P concentrations only marginally increased between groundwater and sediment pore water. In the poorly mixed ditchwater, the dissolved Fe concentrations decreased towards the water surface due to oxidative precipitation of fresh Fe oxyhydroxides, and the P concentrations decreased more sharply than those of Fe. These observations support the view that the dynamics of Fe and P are governed by reduction reactions in the sediment and by oxidation reactions in the ditchwater. In the sediment, reductive dissolution of P-containing Fe oxyhydroxides causes more efficient solubilization of Fe than of P, likely because P is buffered by adsorption on residual Fe oxyhydroxides. Conversely, in the ditchwater, oxidative precipitation causes more efficient immobilization of P than of Fe, due to ferric phosphate formation. The combination of these processes yields a natural and highly efficient sink for P. It is concluded that, in Fe-rich systems, the fate of P at the sediment-water interface is determined by reduction and oxidation of Fe. Copyright © 2015 Elsevier Ltd. All rights reserved.

Availability of ferric iron for microbial reduction in bottom sediments of the freshwater tidal Potomac River

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

Lovley, D.R.; Phillips, E.J.P.

1986-10-01

The distribution of Fe(III), its availability for microbial reduction, and factors controlling Fe(III) availability were investigated in sediments from a freshwater site in the Potomac River Estuary. Fe(III) reduction in sediments incubated under anaerobic conditions and depth profiles of oxalate-extractable Fe(III) indicated that Fe(III) reduction was limited to depths of 4 cm or less, with the most intense Fe(III) reduction in the top 1 cm. In incubations of the upper 4 cm of the sediments, Fe(III) reduction was as important as methane production as a pathway for anaerobic electron flow because of the high rates of Fe(III) reduction in themore » 0- 0.5-cm interval. Most of the oxalate-extractable Fe(III) in the sediments was not reduced and persisted to a depth of at least 20 cm. The incomplete reduction was not the result of a lack of suitable electron donors. The oxalate-extractable Fe(III) that was preserved in the sediments was considered to be in a form other than amorphous Fe(III) oxyhydroxide, since synthetic amorphous Fe(III) oxyhydroxide, amorphous Fe(III) oxyhydroxide adsorbed onto clay, and amorphous Fe(III) oxyhydroxide saturated with adsorbed phosphate or fulvic acids were all readily reduced. Fe/sub 3/O/sub 4/ and the mixed Fe(III)-Fe(II) compound(s) that were produced during the reduction of amorphous Fe(III) oxyhydroxide in an enrichment culture were oxalate extractable but were not reduced, suggesting that mixed Fe(III)-Fe(II) compounds might account for the persistence of oxalate-extractable Fe(III) in the sediments.« less

Microbial production of isotopically light iron(II) in a modern chemically precipitated sediment and implications for isotopic variations in ancient rocks

USGS Publications Warehouse

Tangalos, G.E.; Beard, B.L.; Johnson, C.M.; Alpers, Charles N.; Shelobolina, E.S.; Xu, H.; Konishi, H.; Roden, E.E.

2012-01-01

The inventories and Fe isotope composition of aqueous Fe(II) and solid-phase Fe compounds were quantified in neutral-pH, chemically precipitated sediments downstream of the Iron Mountain acid mine drainage site in northern California, USA. The sediments contain high concentrations of amorphous Fe(III) oxyhydroxides [Fe(III)am] that allow dissimilatory iron reduction (DIR) to predominate over Fe–S interactions in Fe redox transformation, as indicated by the very low abundance of Cr(II)-extractable reduced inorganic sulfur compared with dilute HCl-extractable Fe. δ56Fe values for bulk HCl- and HF-extractable Fe were ≈ 0. These near-zero bulk δ56Fe values, together with the very low abundance of dissolved Fe in the overlying water column, suggest that the pyrite Fe source had near-zero δ56Fe values, and that complete oxidation of Fe(II) took place prior to deposition of the Fe(III) oxide-rich sediment. Sediment core analyses and incubation experiments demonstrated the production of millimolar quantities of isotopically light (δ56Fe ≈ -1.5 to -0.5‰) aqueous Fe(II) coupled to partial reduction of Fe(III)am by DIR. Trends in the Fe isotope composition of solid-associated Fe(II) and residual Fe(III)am are consistent with experiments with synthetic Fe(III) oxides, and collectively suggest an equilibrium Fe isotope fractionation between aqueous Fe(II) and Fe(III)am of approximately -2‰. These Fe(III) oxide-rich sediments provide a model for early diagenetic processes that are likely to have taken place in Archean and Paleoproterozoic marine sediments that served as precursors for banded iron formations. Our results suggest pathways whereby DIR could have led to the formation of large quantities of low-δ56Fe minerals during BIF genesis.

Geophysical Interpretations of the Southern Espanola Basin, New Mexico, That Contribute to Understanding Its Hydrogeologic Framework

USGS Publications Warehouse

Grauch, V.J.S.; Phillips, Jeffrey D.; Koning, Daniel J.; Johnson, Peggy S.; Bankey, Viki

2009-01-01

The southern Espanola basin consists of a westward- and northward-thickening wedge of rift fill, composed primarily of Santa Fe Group sediments, that serves as an important aquifer for the city of Santa Fe and surrounding areas. Detailed aeromagnetic surveys were flown to better understand ground-water resources in this aquifer. This report presents a synthesis of these data with gravity data and other constraints. The interpretations were accomplished using qualitative interpretation, state-of-art data analysis techniques, and two- and three-dimensional modeling. The results depict the presence of and depth to many geologic features that have hydrogeologic significance, including shallow faults, different types of igneous units, and basement rocks. The results are presented as map interpretations, geophysical profile models, and a digital surface that represents the base and thickness of Santa Fe Group sediments, as well as vector files of some volcanic features and faults.

Depth-dependent geochemical and microbiological gradients in Fe(III) deposits resulting from coal mine-derived acid mine drainage

PubMed Central

Brantner, Justin S.; Haake, Zachary J.; Burwick, John E.; Menge, Christopher M.; Hotchkiss, Shane T.; Senko, John M.

2014-01-01

We evaluated the depth-dependent geochemistry and microbiology of sediments that have developed via the microbially-mediated oxidation of Fe(II) dissolved in acid mine drainage (AMD), giving rise to a 8–10 cm deep “iron mound” that is composed primarily of Fe(III) (hydr)oxide phases. Chemical analyses of iron mound sediments indicated a zone of maximal Fe(III) reducing bacterial activity at a depth of approximately 2.5 cm despite the availability of dissolved O2 at this depth. Subsequently, Fe(II) was depleted at depths within the iron mound sediments that did not contain abundant O2. Evaluations of microbial communities at 1 cm depth intervals within the iron mound sediments using “next generation” nucleic acid sequencing approaches revealed an abundance of phylotypes attributable to acidophilic Fe(II) oxidizing Betaproteobacteria and the chloroplasts of photosynthetic microeukaryotic organisms in the upper 4 cm of the iron mound sediments. While we observed a depth-dependent transition in microbial community structure within the iron mound sediments, phylotypes attributable to Gammaproteobacterial lineages capable of both Fe(II) oxidation and Fe(III) reduction were abundant in sequence libraries (comprising ≥20% of sequences) from all depths. Similarly, abundances of total cells and culturable Fe(II) oxidizing bacteria were uniform throughout the iron mound sediments. Our results indicate that O2 and Fe(III) reduction co-occur in AMD-induced iron mound sediments, but that Fe(II)-oxidizing activity may be sustained in regions of the sediments that are depleted in O2. PMID:24860562

Molecular comparison of bacterial communities within iron-containing flocculent mats associated with submarine volcanoes along the Kermadec Arc.

PubMed

Hodges, Tyler W; Olson, Julie B

2009-03-01

Iron oxide sheaths and filaments are commonly found in hydrothermal environments and have been shown to have a biogenic origin. These structures were seen in the flocculent material associated with two submarine volcanoes along the Kermadec Arc north of New Zealand. Molecular characterization of the bacterial communities associated with the flocculent samples indicated that no known Fe-oxidizing bacteria dominated the recovered clone libraries. However, clones related to the recently described Fe-oxidizing bacterium Mariprofundus ferrooxydans were obtained from both the iron-containing flocculent (Fe-floc) and sediment samples, and peaks corresponding to Mariprofundus ferrooxydans, as well as the related clones, were observed in several of our terminal restriction fragment length polymorphism profiles. A large group of epsilonproteobacterial sequences, for which there is no cultured representative, dominated clones from the Fe-floc libraries and were less prevalent in the sediment sample. Phylogenetic analyses indicated that several operational taxonomic units appeared to be site specific, and statistical analyses of the clone libraries found that all samples were significantly different from each other. Thus, the bacterial communities in the Fe-floc samples were not more closely related to each other than to the sediment communities.

Assessment of trace metals contamination in the coastal sediments of the Egyptian Mediterranean coast

NASA Astrophysics Data System (ADS)

El Baz, Sherif M.; Khalil, Mohamed M.

2018-07-01

Trace metals contamination has been recently increased in the Egyptian Mediterranean coast owing to the nearby anthropological activities. This investigation aimed to detect the concentrations of six different trace metals (Fe, Mn, Cu, Cd, Pb and Zn) in surface sediments from the central part of the Egyptian Mediterranean coast, and to assess their state of contamination from different indices and risk factor calculations. Mean concentrations of Cu, Pb and Zn were lower and the mean concentration of Cd was higher compared to the background values. The assessment of pollution was mainly based on the contamination indices. Based on the contamination factor, Pb was the most enriched element followed by Cd, Mn, Zn and Cu. Most of the sites show low contamination with respect to Pb, Mn, Cd, Fe, Zn and Cu. The pollution load index also suggests that all the coastal sediments are unpolluted. According to the geoaccumulation index, the sediments were classified into unpolluted with Mn, Cd, Fe and Pb, and unpolluted to moderately polluted with Pb. Risk evaluation revealed that Cd had the greatest ecological risk, followed by Pb, Cu, Mn, while Zn had the lowest risk. With the aid of statistical methods, the origin of metals is classified into two clusters (A and B). Group A consists of Fe, Mn and Cu, whereas group B contains Zn, Pb and Cd. In the first cluster Fe and Mn are joined to each other at a positive and significant similarity (0.68). Fe is recognized as an indicator of lithogenous origin, therefore, its higher similarity with Mn may be indicative of the similar origin for Manganese. In the second cluster Pb and Zn are joined to each other at a positive and significant similarity (0.80). Pb is recognized as an indicator of anthropogenic origin, therefore, its higher similarity with Zn may be indicative of the similar origin for Zinc.

Biogeochemical transformation of Fe minerals in a petroleum-contaminated aquifer

USGS Publications Warehouse

Zachara, John M.; Kukkadapu, Ravi K.; Glassman, Paul L.; Dohnalkova, Alice; Fredrickson, Jim K.; Anderson, Todd

2004-01-01

The Bemidji aquifer in Minnesota, USA is a well-studied site of subsurface petroleum contamination. The site contains an anoxic groundwater plume where soluble petroleum constituents serve as an energy source for a region of methanogenesis near the source and bacterial Fe(III) reduction further down gradient. Methanogenesis apparently begins when bioavailable Fe(III) is exhausted within the sediment. Past studies indicate that Geobacter species and Geothrix fermentens-like organisms are the primary dissimilatory Fe-reducing bacteria at this site. The Fe mineralogy of the pristine aquifer sediments and samples from the methanogenic (source) and Fe(III) reducing zones were characterized in this study to identify microbiologic changes to Fe valence and mineral distribution, and to identify whether new biogenic mineral phases had formed. Methods applied included X-ray diffraction; X-ray fluorescence (XRF); and chemical extraction; optical, transmission, and scanning electron microscopy; and Mössbauer spectroscopy.All of the sediments were low in total Fe content (≈ 1%) and exhibited complex Fe-mineralogy. The bulk pristine sediment and its sand, silt, and clay-sized fractions were studied in detail. The pristine sediments contained Fe(II) and Fe(III) mineral phases. Ferrous iron represented approximately 50% of FeTOT. The relative Fe(II) concentration increased in the sand fraction, and its primary mineralogic residence was clinochlore with minor concentrations found as a ferroan calcite grain cement in carbonate lithic fragments. Fe(III) existed in silicates (epidote, clinochlore, muscovite) and Fe(III) oxides of detrital and authigenic origin. The detrital Fe(III) oxides included hematite and goethite in the form of mm-sized nodular concretions and smaller-sized dispersed crystallites, and euhedral magnetite grains. Authigenic Fe(III) oxides increased in concentration with decreasing particle size through the silt and clay fraction. Chemical extraction and Mössbauer analysis indicated that this was a ferrihydrite like-phase. Quantitative mineralogic and Fe(II/III) ratio comparisons between the pristine and contaminated sediments were not possible because of textural differences. However, comparisons between the texturally-similar source (where bioavailable Fe(III) had been exhausted) and Fe(III) reducing zone sediments (where bioavailable Fe(III) remained) indicated that dispersed detrital, crystalline Fe(III) oxides and a portion of the authigenic, poorly crystalline Fe(III) oxide fraction had been depleted from the source zone sediment by microbiologic activity. Little or no effect of microbiologic activity was observed on silicate Fe(III). The presence of residual “ferrihydrite” in the most bioreduced, anoxic plume sediment (source) implied that a portion of the authigenic Fe(III) oxides were biologically inaccessible in weathered, lithic fragment interiors. Little evidence was found for the modern biogenesis of authigenic ferrous-containing mineral phases, perhaps with the exception of thin siderite or ferroan calcite surface precipitates on carbonate lithic fragments within source zone sediments.

Geologic map of the La Mesita Negra SE Quadrangle, Bernalillo County, New Mexico

USGS Publications Warehouse

Shroba, Ralph R.; Thompson, Ren A.; Schmidt, Dwight L.; Personius, Stephen F.; Maldonado, Florian; Brandt, Theodore R.

2003-01-01

Geologic mapping, in support of the USGS Middle Rio Grande Basin Geologic Mapping Project, shows the spatial distribution of artificial-fill, alluvial, colluvial, and eolian deposits, lava flows and related sediments of the Albuquerque volcanoes, and upper Santa Fe Group sediments. These deposits are on, beneath, and along the West Mesa (Llano de Albuquerque) just west of Albuquerque, New Mexico. Artificial fill deposits are mapped chiefly beneath and near segments of Interstate 40, in an inactive landfill (or dump) north of Interstate 40 near the eastern boundary of the map area, and in the active Cerro Colorado landfill near the southwestern corner of the map area. Alluvial deposits are mapped in stream channels, beneath treads of terraces, and on hill slopes. They include alluvium in stream channels and beneath treads of low terraces, terrace alluvium, sheetwash deposits, gravelly alluvium, and old alluvium and calcic soils of the Llano de Albuquerque. Alluvial and colluvial deposits are mapped on hill slopes. They include young alluvial-slope deposits, alluvium and colluvium, undivided, and old alluvial-slope deposits. Colluvial deposits are also mapped on hill slopes. They include colluvial deposits, undivided, as well as alluvial deposits, eolian sand, and calcic soils associated with fault scarps. Eolian deposits as well as eolian and alluvial deposits mantle gently slopping surfaces on the Llano de Albuquerque. They include active eolian sand, active and inactive eolian sand and sheetwash deposits, undivided, and inactive eolian sand and sheetwash deposits, undivided. Lava flows and related sediments of the Albuquerque volcanoes were mapped near the southeast corner of the map area. They include five young lava flows, two young cinder deposits, and old lava flows. Upper Santa Fe Group sediments are well exposed and mapped in the western part of the map area. They include a gravel unit, a pebbly sand unit, and a mud and sand unit. Undivided upper Santa Fe Group sediments were mapped in the eastern part of the map area. Sediments and lava flows in the map area record alluvial, eolian, colluvial, and volcanic processes of the past several million years. The surficial deposits (post-Santa Fe Group sediments) on the map are known or estimated to be at least 1 m thick; most deposits are poorly exposed. Thin (< 50 cm), discontinuous deposits of eolian sand and sheetwash (Qea, Qes, and Qsw) locally are present on gently sloping map units older than the alluvium in stream channels and low terraces (Qa). These thin eolian and sheetwash deposits are not mapped, but they are widespread on the gravel unit of the upper Santa Fe Group sediments (Tg) on the eastern flank of the Llano de Albuquerque, near the eastern boundary of the map area (quadrangle). Small deposits of artificial fill (af) less than about 25 m wide are not mapped. Fractional map symbols (for example, Qsw/Qby1) are used where sheetwash deposits mantle lava flows. These fractional units are not described here; instead refer to descriptions of individual units.

Assessment of Available Phosphorus in the Lake Sediments Using an Innovative Composite Membrane

NASA Astrophysics Data System (ADS)

Huang, Qinghui; Wang, Zijian; Wang, Donghong

2010-11-01

An innovative iron oxide embedded cellulose acetate membrane (FeO/CAM) was synthesized and used to study available phosphorus in Chinese lake sediments. The kinetics of available P release was investigated by FeO/CAM for different types of sediments ranging in Olsen-P from 19.1 to 170.6 mg/kg. The results showed that the average kd values (0.094 h-1) of the Taihu sediments were comparable to those of the soils with similar texture estimated by iron oxide impregnated filter paper (FeO paper) though they were generally lower than those of sandy soils. It is indicated that the FeO/CAM can be used as an infinite P sink to estimate available P (FeO-P). The concentrations of FeO-P were significantly correlated with those of extractable P forms, e.g. Olsen-P (R2 = 0.962, p<0.01) in lake sediments. This synthetic membrane excelled FeO paper in the endurance and the stain resistance to soil particles. Therefore, the FeO/CAM is useful to assess phosphorus bioavailability of the sediments.

Enzymatic versus nonenzymatic mechanisms for Fe(III) reduction in aquatic sediments

USGS Publications Warehouse

Lovley, D.R.; Phillips, E.J.P.; Lonergan, D.J.

1991-01-01

The potential for nonenzymatic reduction of Fe(III) either by organic compounds or by the development of a low redox potential during microbial metabolism was compared with direct, enzymatic Fe(III) reduction by Fe(III)-reducing microorganisms. At circumneutral pH, very few organic compounds nonenzymatically reduced Fe(III). In contrast, in the presence of the appropriate Fe(IH)-reducing microorganisms, most of the organic compounds examined could be completely oxidized to carbon dioxide with the reduction of Fe(III). Even for those organic compounds that could nonenzymatically reduce Fe(III), microbial Fe(III) reduction was much more extensive. The development of a low redox potential during microbial fermentation did not result in nonenzymatic Fe(III) reduction. Model organic compounds were readily oxidized in Fe(III)-reducing aquifer sediments, but not in sterilized sediments. These results suggest that microorganisms enzymatically catalyze most of the Fe(III) reduction in the Fe(III) reduction zone of aquatic sediments and aquifers.

Impacts of flocculation on the distribution and diagenesis of iron in boreal estuarine sediments

NASA Astrophysics Data System (ADS)

Jilbert, Tom; Asmala, Eero; Schröder, Christian; Tiihonen, Rosa; Myllykangas, Jukka-Pekka; Virtasalo, Joonas J.; Kotilainen, Aarno; Peltola, Pasi; Ekholm, Päivi; Hietanen, Susanna

2018-03-01

Iron (Fe) plays a key role in sedimentary diagenetic processes in coastal systems, participating in various redox reactions and influencing the burial of organic carbon. Large amounts of Fe enter the marine environment from boreal river catchments associated with dissolved organic matter (DOM) and as colloidal Fe oxyhydroxides, principally ferrihydrite. However, the fate of this Fe pool in estuarine sediments has not been extensively studied. Here we show that flocculation processes along a salinity gradient in an estuary of the northern Baltic Sea efficiently transfer Fe and OM from the dissolved phase into particulate material that accumulates in the sediments. Flocculation of Fe and OM is partially decoupled. This is likely due to the presence of discrete colloidal ferrihydrite in the freshwater Fe pool, which responds differently from DOM to estuarine mixing. Further decoupling of Fe from OM occurs during sedimentation. While we observe a clear decline with distance offshore in the proportion of terrestrial material in the sedimentary particulate organic matter (POM) pool, the distribution of flocculated Fe in sediments is modulated by focusing effects. Labile Fe phases are most abundant at a deep site in the inner basin of the estuary, consistent with input from flocculation and subsequent focusing. The majority of the labile Fe pool is present as Fe (II), including both acid-volatile sulfur (AVS)-bound Fe and unsulfidized phases. The ubiquitous presence of unsulfidized Fe (II) throughout the sediment column suggests Fe (II)-OM complexes derived from reduction of flocculated Fe (III)-OM, while other Fe (II) phases are likely derived from the reduction of flocculated ferrihydrite. Depth-integrated rates of Fe (II) accumulation (AVS-Fe + unsulfidized Fe (II) + pyrite) for the period 1970-2015 are greater in the inner basin of the estuary with respect to a site further offshore, confirming higher rates of Fe reduction in near-shore areas. Mössbauer 57Fe spectroscopy shows that refractory Fe is composed largely of superparamagnetic Fe (III), high-spin Fe (II) in silicates, and, at one station, also oxide minerals derived from past industrial activities. Our results highlight that the cycling of Fe in boreal estuarine environments is complex, and that the partial decoupling of Fe from OM during flocculation and sedimentation is key to understanding the role of Fe in sedimentary diagenetic processes in coastal areas.

Microbial Iron(II) Oxidation in Littoral Freshwater Lake Sediment: The Potential for Competition between Phototrophic vs. Nitrate-Reducing Iron(II)-Oxidizers

PubMed Central

Melton, E. D.; Schmidt, C.; Kappler, A.

2012-01-01

The distribution of neutrophilic microbial iron oxidation is mainly determined by local gradients of oxygen, light, nitrate and ferrous iron. In the anoxic top part of littoral freshwater lake sediment, nitrate-reducing and phototrophic Fe(II)-oxidizers compete for the same e− donor; reduced iron. It is not yet understood how these microbes co-exist in the sediment and what role they play in the Fe cycle. We show that both metabolic types of anaerobic Fe(II)-oxidizing microorganisms are present in the same sediment layer directly beneath the oxic-anoxic sediment interface. The photoferrotrophic most probable number counted 3.4·105 cells·g−1 and the autotrophic and mixotrophic nitrate-reducing Fe(II)-oxidizers totaled 1.8·104 and 4.5·104 cells·g−1 dry weight sediment, respectively. To distinguish between the two microbial Fe(II) oxidation processes and assess their individual contribution to the sedimentary Fe cycle, littoral lake sediment was incubated in microcosm experiments. Nitrate-reducing Fe(II)-oxidizing bacteria exhibited a higher maximum Fe(II) oxidation rate per cell, in both pure cultures and microcosms, than photoferrotrophs. In microcosms, photoferrotrophs instantly started oxidizing Fe(II), whilst nitrate-reducing Fe(II)-oxidizers showed a significant lag-phase during which they probably use organics as e− donor before initiating Fe(II) oxidation. This suggests that they will be outcompeted by phototrophic Fe(II)-oxidizers during optimal light conditions; as phototrophs deplete Fe(II) before nitrate-reducing Fe(II)-oxidizers start Fe(II) oxidation. Thus, the co-existence of the two anaerobic Fe(II)-oxidizers may be possible due to a niche space separation in time by the day-night cycle, where nitrate-reducing Fe(II)-oxidizers oxidize Fe(II) during darkness and phototrophs play a dominant role in Fe(II) oxidation during daylight. Furthermore, metabolic flexibility of Fe(II)-oxidizing microbes may play a paramount role in the conservation of the sedimentary Fe cycle. PMID:22666221

Reactive iron and manganese in estuarine sediments of the Baltic Sea: Impacts of flocculation and redox shuttling

NASA Astrophysics Data System (ADS)

Jilbert, Tom; Tiihonen, Rosa; Myllykangas, Jukka-Pekka; Asmala, Eero; Hietanen, Susanna

2016-04-01

Iron (Fe) and manganese (Mn) play important roles in sedimentary carbon cycling in both freshwater and marine systems. Dissimilatory reduction of Fe and Mn oxides is known to be a major pathway of suboxic organic matter remineralization in surface sediments, while recent studies have shown that Fe and Mn oxides may be involved in the anaerobic oxidation of methane deeper in the sediment column (e.g., Egger et al., 2015). Estuaries are transitional environments, characterized by gradients of salinity and redox conditions which impact on the mobility of Fe and Mn. In turn, the distribution of Fe and Mn in estuarine sediments, and the role of the two metals in carbon cycling, is expected to be spatially heterogeneous. However, few studies have attempted to describe the sedimentary distribution of Fe and Mn in the context of processes occurring in the estuarine water column. In particular, salinity-driven flocculation and redox shuttling are two key processes whose relative impacts on sedimentary Fe and Mn have not been clearly demonstrated. In this study we investigated the coupled water column and sedimentary cycling of Fe and Mn along a 60km non-tidal estuarine transect in the Gulf of Finland, Baltic Sea. We show that riverine Fe entering the estuary as colloidal oxides associated with dissolved organic matter (DOM) is quickly flocculated and sedimented within 5 km of the river mouth, despite the shallow lateral salinity gradient. Sediments within this range are enriched in Fe (up to twice the regional average), principally in the form of crystalline Fe oxides as determined by sequential extractions. The high crystallinity implies relative maturity of the oxide mineralogy, likely due to sustained oxic conditions and long residence time in the river catchment. Despite the reducing conditions below the sediment-water interface, Fe is largely retained in the sediments close to the river mouth. In contrast, sedimentary Mn concentrations are highest in a deep silled basin more than 10km downstream. Throughout the estuary, Mn oxides are reductively dissolved shallower in the sediment column than Fe oxides, resulting in strong effluxes of dissolved Mn from the sediments. Subsequent oxidation of bottom water dissolved Mn to particulate oxides and lateral transport ("redox shuttling") account for the sedimentary Mn enrichments in the deep silled basin. Porewater data suggest that the heterogeneity of Fe and Mn availability in the estuarine sediments may influence the relative importance of the two metals for anaerobic oxidation of methane. Egger, M. et al., Environmental Science and Technology 49(1), 277-283, 2015.

Co-diagenesis of iron and phosphorus in hydrothermal sediments from the southern East Pacific Rise: Implications for the evaluation of paleoseawater phosphate concentrations

NASA Astrophysics Data System (ADS)

Poulton, Simon W.; Canfield, Donald E.

2006-12-01

We present a detailed study of the co-diagenesis of Fe and P in hydrothermal plume fallout sediments from ˜19°S on the southern East Pacific Rise. Three distal sediment cores from 340-1130 km from the ridge crest, collected during DSDP Leg 92, were analysed for solid phase Fe and P associations using sequential chemical extraction techniques. The sediments at all sites are enriched in hydrothermal Fe (oxyhydr)oxides, but during diagenesis a large proportion of the primary ferrihydrite precipitates are transformed to the more stable mineral form of goethite and to a lesser extent to clay minerals, resulting in the release to solution of scavenged P. However, a significant proportion of this P is retained within the sediment, by incorporation into secondary goethite, by precipitation as authigenic apatite, and by readsorption to Fe (oxyhydr)oxides. Molar P/Fe ratios for these sediments are significantly lower than those measured in plume particles from more northern localities along the southern East Pacific Rise, and show a distinct downcore decrease to a depth of ˜12 m. Molar P/Fe ratios are then relatively constant to a depth of ˜35 m. The Fe and P speciation data indicate that diagenetic modification of the sediments is largely complete by a depth of 2.5 m, and thus depth trends in molar P/Fe ratios can not solely be explained by losses of P from the sediment by diffusion to the overlying water column during early diagenesis. Instead, these sediments are likely recording changes in dissolved P concentrations off the SEPR, possibly as a result of redistribution of nutrients in response to changes in oceanic circulation over the last 10 million years. Furthermore, the relatively low molar P/Fe ratios observed throughout these sediments are not necessarily solely due to losses of scavenged P by diffusion to the overlying water column during diagenesis, but may also reflect post-depositional oxidation of pyrite originating from the volatile-rich vents of the southern East Pacific Rise. This study suggests that the molar P/Fe ratio of oxic Fe-rich sediments may serve as a proxy of relative changes in paleoseawater phosphate concentrations, particularly if Fe sulfide minerals are not an important component during transport and deposition.

Are iron-phosphate minerals a sink for phosphorus in anoxic Black Sea sediments?

PubMed

Dijkstra, Nikki; Kraal, Peter; Kuypers, Marcel M M; Schnetger, Bernhard; Slomp, Caroline P

2014-01-01

Phosphorus (P) is a key nutrient for marine organisms. The only long-term removal pathway for P in the marine realm is burial in sediments. Iron (Fe) bound P accounts for a significant proportion of this burial at the global scale. In sediments underlying anoxic bottom waters, burial of Fe-bound P is generally assumed to be negligible because of reductive dissolution of Fe(III) (oxyhydr)oxides and release of the associated P. However, recent work suggests that Fe-bound P is an important burial phase in euxinic (i.e. anoxic and sulfidic) basin sediments in the Baltic Sea. In this study, we investigate the role of Fe-bound P as a potential sink for P in Black Sea sediments overlain by oxic and euxinic bottom waters. Sequential P extractions performed on sediments from six multicores along two shelf-to-basin transects provide evidence for the burial of Fe-bound P at all sites, including those in the euxinic deep basin. In the latter sediments, Fe-bound P accounts for more than 20% of the total sedimentary P pool. We suggest that this P is present in the form of reduced Fe-P minerals. We hypothesize that these minerals may be formed as inclusions in sulfur-disproportionating Deltaproteobacteria. Further research is required to elucidate the exact mineral form and formation mechanism of this P burial phase, as well as its role as a sink for P in sulfide-rich marine sediments.

Hydrothermal sediments are a source of water column Fe and Mn in the Bransfield Strait, Antarctica

NASA Astrophysics Data System (ADS)

Aquilina, Alfred; Homoky, William B.; Hawkes, Jeffrey A.; Lyons, Timothy W.; Mills, Rachel A.

2014-07-01

Short sediment cores were collected from ∼1100 m water depth at the top of Hook Ridge, a submarine volcanic edifice in the Central Basin of the Bransfield Strait, Antarctica, to assess Fe and Mn supply to the water column. Low-temperature hydrothermal fluids advect through these sediments and, in places, subsurface H2S is present at high enough concentrations to support abundant Sclerolinum sp., an infaunal tubeworm that hosts symbiotic thiotrophic bacteria. The water column is fully oxic, and oxygen penetration depths at all sites are 2-5 cmbsf. Pore water Fe and Mn content is high within the subsurface ferruginous zone (max. 565 μmol Fe L-1, >3-7 cmbsf)-14-18 times higher than values measured at a nearby, background site of equivalent water depth. Diffusion and advection of pore waters supply significant Fe and Mn to the surface sediment. Sequential extraction of the sediment demonstrates that there is a significant enrichment in a suite of reactive, authigenic Fe minerals in the upper 0-5 cm of sediment at one site characterised by weathered crusts at the seafloor. At a site with only minor authigenic mineral surface enrichment we infer that leakage of pore water Fe and Mn from the sediment leads to enriched total dissolvable Fe and Mn in bottom waters. An Eh sensor mounted on a towed package mapped a distinct Eh signature above this coring site which is dispersed over several km at the depth of Hook Ridge. We hypothesise that the main mechanism for Fe and Mn efflux from the sediment is breach of the surface oxic layer by the abundant Sclerolinum sp., along with episodic enhancements by physical mixing and resuspension of sediment in this dynamic volcanic environment. We propose that Hook Ridge sediments are an important source of Fe and Mn to the deep waters of the Central Basin in the Bransfield Strait, where concentrations are sustained by the benthic flux, and Fe is stabilised in the water column as either colloidal phases or ligand-bound dissolved species. Entrainment of this water mass into the Drake Passage and thereby the Antarctic Circumpolar Current could provide a significant metal source to this HNLC region of the Southern Ocean if mixing and upwelling occurs before removal of this metal pool to underlying sediments. Sediment-covered volcanic ridges are common within rifted margins and may play a previously overlooked role in the global Fe cycle.

Characterizing phosphorus speciation of Chesapeake Bay sediments using chemical extraction, 31P NMR, and X-ray absorption fine structure spectroscopy.

PubMed

Li, Wei; Joshi, Sunendra R; Hou, Guangjin; Burdige, David J; Sparks, Donald L; Jaisi, Deb P

2015-01-06

Nutrient contamination has been one of the lingering issues in the Chesapeake Bay because the bay restoration is complicated by temporally and seasonally variable nutrient sources and complex interaction between imported and regenerated nutrients. Differential reactivity of sedimentary phosphorus (P) pools in response to imposed biogeochemical conditions can record past sediment history and therefore a detailed sediment P speciation may provide information on P cycling particularly the stability of a P pool and the formation of one pool at the expense of another. This study examined sediment P speciation from three sites in the Chesapeake Bay: (i) a North site in the upstream bay, (ii) a middle site in the central bay dominated by seasonally hypoxic bottom water, and (iii) a South site at the bay-ocean boundary using a combination of sequential P extraction (SEDEX) and spectroscopic techniques, including (31)P NMR, P X-ray absorption near edge structure spectroscopy (XANES), and Fe extended X-ray absorption fine structure (EXAFS). Results from sequential P extraction reveal that sediment P is composed predominantly of ferric Fe-bound P and authigenic P, which was further confirmed by solid-state (31)P NMR, XANES, and EXAFS analyses. Additionally, solution (31)P NMR results show that the sediments from the middle site contain high amounts of organic P such as monoesters and diesters, compared to the other two sites, but that these compounds rapidly decrease with sediment depth indicating remineralized P could have precipitated as authigenic P. Fe EXAFS enabled to identify the changes in Fe mineral composition and P sinks in response to imposed redox condition in the middle site sediments. The presence of lepidocrocite, vermiculite, and Fe smectite in the middle site sediments indicates that some ferric Fe minerals can still be present along with pyrite and vivianite, and that ferric Fe-bound P pool can be a major P sink in anoxic sediments. These results provide improved insights into sediment P dynamics, particularly the rapid remineralization of organic P and the stability of Fe minerals and the ferric Fe-bound P pool in anoxic sediments in the Chesapeake Bay.

Influence of sea level rise on iron diagenesis in an east Florida subterranean estuary

USGS Publications Warehouse

Roy, M.; Martin, J.B.; Cherrier, J.; Cable, J.E.; Smith, C.G.

2010-01-01

Subterranean estuary occupies the transition zone between hypoxic fresh groundwater and oxic seawater, and between terrestrial and marine sediment deposits. Consequently, we hypothesize, in a subterranean estuary, biogeochemical reactions of Fe respond to submarine groundwater discharge (SGD) and sea level rise. Porewater and sediment samples were collected across a 30-m wide freshwater discharge zone of the Indian River Lagoon (Florida, USA) subterranean estuary, and at a site 250. m offshore. Porewater Fe concentrations range from 0.5 ??M at the shoreline and 250. m offshore to about 286 ??M at the freshwater-saltwater boundary. Sediment sulfur and porewater sulfide maxima occur in near-surface OC-rich black sediments of marine origin, and dissolved Fe maxima occur in underlying OC-poor orange sediments of terrestrial origin. Freshwater SGD flow rates decrease offshore from around 1 to 0.1. cm/day, while bioirrigation exchange deepens with distance from about 10. cm at the shoreline to about 40. cm at the freshwater-saltwater boundary. DOC concentrations increase from around 75 ??M at the shoreline to as much as 700 ??M at the freshwater-saltwater boundary as a result of labile marine carbon inputs from marine SGD. This labile DOC reduces Fe-oxides, which in conjunction with slow discharge of SGD at the boundary, allows dissolved Fe to accumulate. Upward advection of fresh SGD carries dissolved Fe from the Fe-oxide reduction zone to the sulfate reduction zone, where dissolved Fe precipitates as Fe-sulfides. Saturation models of Fe-sulfides indicate some fractions of these Fe-sulfides get dissolved near the sediment-water interface, where bioirrigation exchanges oxic surface water. The estimated dissolved Fe flux is approximately 0.84 ??M Fe/day per meter of shoreline to lagoon surface waters. Accelerated sea level rise predictions are thus likely to increase the Fe flux to surface waters and local primary productivity, particularly along coastlines where groundwater discharges through sediments. ?? 2010 Elsevier Ltd.

Iron Cycling in Marine Sediments - New Insights from Isotope Analysis on Sequentially Extracted Fe Fractions

NASA Astrophysics Data System (ADS)

Henkel, S.; Kasten, S.; Poulton, S.; Hartmann, J.; Staubwasser, M.

2014-12-01

Reactive Fe (oxyhydr)oxides preferentially undergo early diagenetic cycling and may cause a diffusive flux of dissolved Fe2+ from sediments towards the sediment-water interface. The partitioning of Fe in sediments has traditionally been studied by applying sequential extractions based on reductive dissolution of Fe minerals. We complemented the sequential leaching method by Poulton and Canfield [1] in order to be able to gain δ56Fe data for specific Fe fractions, as such data are potentially useful to study Fe cycling in marine environments. The specific mineral fractions are Fe-carbonates, ferrihydrite + lepidocrocite, goethite + hematite, and magnetite. Leaching was performed with acetic acid, hydroxylamine-HCl, Na-dithionite and oxalic acid. The processing of leachates for δ56Fe analysis involved boiling the samples in HCl/HNO3/H2O2, Fe precipitation and anion exchange column chromatography. The new method was applied to short sediment cores from the North Sea and a bay of King George Island (South Shetland Islands, Antarctica). Downcore mineral-specific variations in δ56Fe revealed differing contributions of Fe (oxyhydr)oxides to redox cycling. A slight decrease in easily reducible Fe oxides correlating with a slight increase in δ56Fe for this fraction with depth, which is in line with progessive dissimilatory iron reduction [2,3], is visible in the top 10 cm of the North Sea core, but not in the antarctic sediments. Less reactive (dithionite and oxalate leachable) fractions did not reveal isotopic trends. The acetic acid-soluble fraction displayed pronounced δ56Fe trends at both sites that cannot be explained by acid volatile sulfides that are also extracted by acetic acid [1]. We suggest that low δ56Fe values in this fraction relative to the pool of easily reducible Fe oxides result from adsorbed Fe(II) that was open to isotopic exchange with oxide surfaces, affirming the experimental results of Crosby el al. [2]. Hence, δ56Fe analyses on marine sediments appear to be particularly useful when targeting specific Fe pools, rather than the total highly reactive Fe fraction, since isotopic trends may be masked within the latter pool. [1] Poulton and Canfield (2005), Chemical Geology 214, 209-221. [2] Crosby et al., Geobiology 5 (2007), 169-189. [3] Staubwasser et al., Geology 34 (2006), 629-632.

A mass balance approach to investigate arsenic cycling in a petroleum plume.

PubMed

Ziegler, Brady A; Schreiber, Madeline E; Cozzarelli, Isabelle M; Crystal Ng, G-H

2017-12-01

Natural attenuation of organic contaminants in groundwater can give rise to a series of complex biogeochemical reactions that release secondary contaminants to groundwater. In a crude oil contaminated aquifer, biodegradation of petroleum hydrocarbons is coupled with the reduction of ferric iron (Fe(III)) hydroxides in aquifer sediments. As a result, naturally occurring arsenic (As) adsorbed to Fe(III) hydroxides in the aquifer sediment is mobilized from sediment into groundwater. However, Fe(III) in sediment of other zones of the aquifer has the capacity to attenuate dissolved As via resorption. In order to better evaluate how long-term biodegradation coupled with Fe-reduction and As mobilization can redistribute As mass in contaminated aquifer, we quantified mass partitioning of Fe and As in the aquifer based on field observation data. Results show that Fe and As are spatially correlated in both groundwater and aquifer sediments. Mass partitioning calculations demonstrate that 99.9% of Fe and 99.5% of As are associated with aquifer sediment. The sediments act as both sources and sinks for As, depending on the redox conditions in the aquifer. Calculations reveal that at least 78% of the original As in sediment near the oil has been mobilized into groundwater over the 35-year lifespan of the plume. However, the calculations also show that only a small percentage of As (∼0.5%) remains in groundwater, due to resorption onto sediment. At the leading edge of the plume, where groundwater is suboxic, sediments sequester Fe and As, causing As to accumulate to concentrations 5.6 times greater than background concentrations. Current As sinks can serve as future sources of As as the plume evolves over time. The mass balance approach used in this study can be applied to As cycling in other aquifers where groundwater As results from biodegradation of an organic carbon point source coupled with Fe reduction. Copyright © 2017 Elsevier Ltd. All rights reserved.

A mass balance approach to investigate arsenic cycling in a petroleum plume

USGS Publications Warehouse

Ziegler, Brady A.; Schreiber, Madeline E.; Cozzarelli, Isabelle M.; Ng. G.-H. Crystal,

2017-01-01

Natural attenuation of organic contaminants in groundwater can give rise to a series of complex biogeochemical reactions that release secondary contaminants to groundwater. In a crude oil contaminated aquifer, biodegradation of petroleum hydrocarbons is coupled with the reduction of ferric iron (Fe(III)) hydroxides in aquifer sediments. As a result, naturally occurring arsenic (As) adsorbed to Fe(III) hydroxides in the aquifer sediment is mobilized from sediment into groundwater. However, Fe(III) in sediment of other zones of the aquifer has the capacity to attenuate dissolved As via resorption. In order to better evaluate how long-term biodegradation coupled with Fe-reduction and As mobilization can redistribute As mass in contaminated aquifer, we quantified mass partitioning of Fe and As in the aquifer based on field observation data. Results show that Fe and As are spatially correlated in both groundwater and aquifer sediments. Mass partitioning calculations demonstrate that 99.9% of Fe and 99.5% of As are associated with aquifer sediment. The sediments act as both sources and sinks for As, depending on the redox conditions in the aquifer. Calculations reveal that at least 78% of the original As in sediment near the oil has been mobilized into groundwater over the 35-year lifespan of the plume. However, the calculations also show that only a small percentage of As (∼0.5%) remains in groundwater, due to resorption onto sediment. At the leading edge of the plume, where groundwater is suboxic, sediments sequester Fe and As, causing As to accumulate to concentrations 5.6 times greater than background concentrations. Current As sinks can serve as future sources of As as the plume evolves over time. The mass balance approach used in this study can be applied to As cycling in other aquifers where groundwater As results from biodegradation of an organic carbon point source coupled with Fe reduction.

Combined Fe/P and Fe/S ratios as a practicable index for estimating the release potential of internal-P in freshwater sediment.

PubMed

Wang, Jingfu; Chen, Jingan; Guo, Jianyang; Sun, Qingqing; Yang, Haiquan

2018-04-01

Release of phosphorus (P) from sediment is a major source of P in many freshwater lakes. Currently, assessing the ability of sediment to release P, which is valuable to the management of water eutrophication, remains a challenge. Thus, the purpose of this study was to find effective indexes for predicting the release potential of internal-P. In this study, high-resolution diffusive gradients in thin films (DGT) and conventional sequential extraction were used to characterize the distribution and speciation of P, iron (Fe), and sulfur (S) in the surface sediment of a mildly eutrophic reservoir in southwestern China. Sediment samples exhibited large variations in Fe, S, and P, thereby providing favorable conditions for investigating the effects of Fe and S on sediment P mobilization. In contrast to traditional knowledge, our results show that total P (TP) and redox-sensitive P(BD-P) are poorly correlated with releasable P(DGT-P). This implies that high levels of sedimentary TP and BD-P do not necessarily result in an elevated release of internal-P under anaerobic conditions. Sedimentary P release was greatly suppressed at ratios of Fe/P > 30 and Fe/S > 6. Significant positive correlations between DGT-P and DGT-Fe or DGT-S suggest that Fe and S play an important role in governing the mobility of sedimentary P. These results support the combined Fe/P and Fe/S ratios as an effective and practicable index for assessing the ability of sediment to release P. Thus, our study provides a new and simple method for assessing sedimentary P pollution in freshwater ecosystems.

Effects of electron acceptors on soluble reactive phosphorus in the overlying water during algal decomposition.

PubMed

Wang, Jinzhi; Jiang, Xia; Zheng, Binghui; Niu, Yuan; Wang, Kun; Wang, Wenwen; Kardol, Paul

2015-12-01

Endogenous phosphorus (P) release from sediments is an important factor to cause eutrophication and, hence, algal bloom in lakes in China. Algal decomposition depletes dissolved oxygen (DO) and causes anaerobic conditions and therefore increases P release from sediments. As sediment P release is dependent on the iron (Fe) cycle, electron acceptors (e.g., NO3 (-), SO4 (2-), and Mn(4+)) can be utilized to suppress the reduction of Fe(3+) under anaerobic conditions and, as such, have the potential to impair the release of sediment P. Here, we used a laboratory experiment to test the effects of FeCl3, MnO2, and KNO3 on soluble reactive phosphorus (SRP) concentration and related chemical variables in the overlying water column during algal decomposition at different algal densities. Results showed that algal decomposition significantly depleted DO and thereby increased sediment Fe-bound P release. Compared with the control, addition of FeCl3 significantly decreased water SRP concentration through inhibiting sediment P release. Compared with FeCl3, addition of MnO2 has less potential to suppress sediment P release during algal decomposition. Algal decomposition has the potential for NO3 (-) removal from aquatic ecosystem through denitrification and by that alleviates the suppressing role of NO3 (-) on sediment P release. Our results indicated that FeCl3 and MnO2 could be efficient in reducing sediment P release during algal decomposition, with the strongest effect found for FeCl3; large amounts of NO3 (-) were removed from the aquatic ecosystem through denitrification during algal decomposition. Moreover, the amounts of NO3 (-) removal increased with increasing algal density.

Naphthalene and benzene degradation under Fe(III)-reducing conditions in petroleum-contaminated aquifers

USGS Publications Warehouse

Anderson, Robert T.; Lovely, Derek R.

1999-01-01

Naphthalene was oxidized anaerobically to CO2 in sediments collected from a petroleum-contaminated aquifer in Bemidji, Minnesota in which Fe(III) reduction was the terminal electron-accepting process. Naphthalene was not oxidized in sediments from the methanogenic zone at Bemidji or in sediments from the Fe(III)-reducing zone of other petroleum-contaminated aquifers studied. In a profile across the Fe(III)-reducing zone of the Bemidji aquifer, rates of naphthalene oxidation were fastest in sediments with the highest proportion of Fe(III), which was also the zone of the most rapid degradation of benzene, toluene, and acetate. The comparative studies attempted to elucidate factors that might account for the fact that unsubstituted aromatic hydrocarbons such as benzene and naphthalene were degraded under Fe(III)-reducing conditions at Bemidji, but not at the other aquifers examined. These studies indicated that the ability of Fe(III)-reducing microorganisms to degrade benzene and naphthalene at the Bemidji site cannot be attributed to groundwater components that make Fe(III) more available for reduction or other potential factors that were evaluated. However, unlike the other aquifers evaluated, uncontaminated sediments at the Bemidji site could be adapted for anaerobic benzene degradation merely with the addition of benzene. These findings indicate that Bemidji sediments naturally contain Fe(III) reducers capable of degradation of unsubstituted aromatic hydrocarbons.

Disturbances to metal partitioning during toxicity testing of iron(II)-rich estuarine pore waters and whole sediments.

PubMed

Simpson, Stuart L; Batley, Graeme E

2003-02-01

Metal partitioning is altered when suboxic estuarine sediments containing Fe(II)-rich pore waters are disturbed during collection, preparation, and toxicity testing. Experiments with model Fe(II)-rich pore waters demonstrated the rates at which adsorptive losses of Cd, Cu, Ni, Mn, Pb, and Zn occur upon exposure to air. Experiments with Zn-contaminated estuarine sediments demonstrated large and often unpredictable changes to metal partitioning during sediment storage, removal of organisms, and homogenization before testing. Small modifications to conditions, such as aeration of overlying waters, caused large changes to the metal partitioning. Disturbances caused by sediment collection required many weeks for reestablishment of equilibrium. Bioturbation by benthic organisms led to oxidation of pore-water Fe(II) and lower Zn fluxes because of the formation of Fe hydroxide precipitates that adsorb pore-water Zn. For five weeks after the addition of organisms to sediments, Zn fluxes increased slowly as the organisms established themselves in the sediments, indicating that the establishment of equilibrium was not rapid. The results are discussed in terms of the dynamic nature of suboxic, Fe(II)-rich estuarine sediments, how organisms perturb their environment, and the importance of understanding chemistry in toxicity testing with whole sediments or pore water. Recommendations are provided for the handling of sediments for toxicity testing.

Geologic Map of The Volcanoes Quadrangle, Bernalillo and Sandoval Counties, New Mexico

USGS Publications Warehouse

Thompson, Ren A.; Shroba, Ralph R.; Menges, Christopher M.; Schmidt, Dwight L.; Personius, Stephen F.; Brandt, Theodore R.

2009-01-01

This geologic map, in support of the U.S. Geological Survey Middle Rio Grande Basin Geologic Mapping Project, shows the spatial distribution of surficial deposits, lava flows, and related sediments of the Albuquerque volcanoes, upper Santa Fe Group sediments, faults, and fault-related structural features. These deposits are on, along, and beneath the Llano de Albuquerque (West Mesa) west of Albuquerque, New Mexico. Some of these deposits are in the western part of Petroglyph National Monument. Artificial fill deposits are mapped chiefly beneath and near the City of Albuquerque Soil Amendment Facility and the Double Eagle II Airport. Alluvial deposits were mapped in and along stream channels, beneath terrace surfaces, and on the Llano de Albuquerque and its adjacent hill slopes. Deposits composed of alluvium and colluvium are also mapped on hill slopes. Wedge-shaped deposits composed chiefly of sandy sheetwash deposits, eolian sand, and intercalated calcic soils have formed on the downthrown-sides of faults. Deposits of active and inactive eolian sand and sandy sheetwash deposits mantle the Llano de Albuquerque. Lava flows and related sediments of the Albuquerque volcanoes were mapped near the southeast corner of the map area. They include eleven young lava flow units and, where discernable, associated vent and near-vent pyroclastic deposits associated with cinder cones. Upper Santa Fe Group sediments are chiefly fluvial in origin, and are well exposed near the western boundary of the map area. From youngest to oldest they include a gravel unit, pebbly sand unit, tan sand and mud unit, tan sand unit, tan sand and clay unit, and silty sand unit. Undivided upper Santa Fe Group sediments are mapped in the eastern part of the map area. Faults were identified on the basis of surface expression determined from field mapping and interpretation of aeromagnetic data where concealed beneath surficial deposits. Fault-related structural features are exposed and were mapped near the western boundary of the map area.

Application of a Depositional Facies Model to an Acid Mine Drainage Site▿ †

PubMed Central

Brown, Juliana F.; Jones, Daniel S.; Mills, Daniel B.; Macalady, Jennifer L.; Burgos, William D.

2011-01-01

Lower Red Eyes is an acid mine drainage site in Pennsylvania where low-pH Fe(II) oxidation has created a large, terraced iron mound downstream of an anoxic, acidic, metal-rich spring. Aqueous chemistry, mineral precipitates, microbial communities, and laboratory-based Fe(II) oxidation rates for this site were analyzed in the context of a depositional facies model. Depositional facies were defined as pools, terraces, or microterracettes based on cm-scale sediment morphology, irrespective of the distance downstream from the spring. The sediments were composed entirely of Fe precipitates and cemented organic matter. The Fe precipitates were identified as schwertmannite at all locations, regardless of facies. Microbial composition was studied with fluorescence in situ hybridization (FISH) and transitioned from a microaerophilic, Euglena-dominated community at the spring, to a Betaproteobacteria (primarily Ferrovum spp.)-dominated community at the upstream end of the iron mound, to a Gammaproteobacteria (primarily Acidithiobacillus)-dominated community at the downstream end of the iron mound. Microbial community structure was more strongly correlated with pH and geochemical conditions than depositional facies. Intact pieces of terrace and pool sediments from upstream and downstream locations were used in flowthrough laboratory reactors to measure the rate and extent of low-pH Fe(II) oxidation. No change in Fe(II) concentration was observed with 60Co-irradiated sediments or with no-sediment controls, indicating that abiotic Fe(II) oxidation was negligible. Upstream sediments attained lower effluent Fe(II) concentrations compared to downstream sediments, regardless of depositional facies. PMID:21097582

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

Wu, Tao; Kukkadapu, Ravi K.; Griffin, Aron M.

Fe(III)-oxides and Fe(III)-bearing phyllosilicates are the two major iron sources utilized as electron acceptors by dissimilatory iron-reducing bacteria (DIRB) in anoxic soils and sediments. Although there have been many studies of microbial Fe(III)-oxide and Fe(III)-phyllosilicate reduction with both natural and specimen materials, no controlled experimental information is available on the interaction between these two phases when both are available for microbial reduction. In this study, the model DIRB Geobacter sulfurreducens was used to examine the pathways of Fe(III) reduction in Fe(III)-oxide stripped subsurface sediment that was coated with different amounts of synthetic high surface area goethite. Cryogenic (12K) 57Fe Mössbauermore » spectroscopy was used to determine changes in the relative abundances of Fe(III)-oxide, Fe(III)-phyllosilicate, and phyllosilicate-associated Fe(II) (Fe(II)-phyllosilicate) in bioreduced samples. Analogous Mössbauer analyses were performed on samples from abiotic Fe(II) sorption experiments in which sediments were exposed to a quantity of exogenous soluble Fe(II) (FeCl22H2O) comparable to the amount of Fe(II) produced during microbial reduction. A Fe partitioning model was developed to analyze the fate of Fe(II) and assess the potential for abiotic Fe(II)-catalyzed reduction of Fe(III)-phyllosilicatesilicates. The microbial reduction experiments indicated that although reduction of Fe(III)-oxide accounted for virtually all of the observed bulk Fe(III) reduction activity, there was no significant abiotic electron transfer between oxide-derived Fe(II) and Fe(III)-phyllosilicatesilicates, with 26-87% of biogenic Fe(II) appearing as sorbed Fe(II) in the Fe(II)-phyllosilicate pool. In contrast, the abiotic Fe(II) sorption experiments showed that 41 and 24% of the added Fe(II) engaged in electron transfer to Fe(III)-phyllosilicate surfaces in synthetic goethite-coated and uncoated sediment. Differences in the rate of Fe(II) addition and system redox potential may account for the microbial and abiotic reaction systems. Our experiments provide new insight into pathways for Fe(III) reduction in mixed Fe(III)-oxide/Fe(III)-phyllosilicate assemblages, and provide key mechanistic insight for interpreting microbial reduction experiments and field data from complex natural soils and sediments.« less

Arsenic release from shallow aquifers of the Hetao basin, Inner Mongolia: evidence from bacterial community in aquifer sediments and groundwater.

PubMed

Li, Yuan; Guo, Huaming; Hao, Chunbo

2014-12-01

Indigenous microbes play crucial roles in arsenic mobilization in high arsenic groundwater systems. Databases concerning the presence and the activity of microbial communities are very useful in evaluating the potential of microbe-mediated arsenic mobilization in shallow aquifers hosting high arsenic groundwater. This study characterized microbial communities in groundwaters at different depths with different arsenic concentrations by DGGE and one sediment by 16S rRNA gene clone library, and evaluated arsenic mobilization in microcosm batches with the presence of indigenous bacteria. DGGE fingerprints revealed that the community structure changed substantially with depth at the same location. It indicated that a relatively higher bacterial diversity was present in the groundwater sample with lower arsenic concentration. Sequence analysis of 16S rRNA gene demonstrated that the sediment bacteria mainly belonged to Pseudomonas, Dietzia and Rhodococcus, which have been widely found in aquifer systems. Additionally, NO3(-)-reducing bacteria Pseudomonas sp. was the largest group, followed by Fe(III)-reducing, SO4(2-)-reducing and As(V)-reducing bacteria in the sediment sample. These anaerobic bacteria used the specific oxyanions as electron acceptor and played a significant role in reductive dissolution of Fe oxide minerals, reduction of As(V), and release of arsenic from sediments into groundwater. Microcosm experiments, using intact aquifer sediments, showed that arsenic release and Fe(III) reduction were microbially mediated in the presence of indigenous bacteria. High arsenic concentration was also observed in the batch without amendment of organic carbon, demonstrating that the natural organic matter in sediments was the potential electron donor for microbially mediated arsenic release from these aquifer sediments.

Impact of sedimentary provenance and weathering on arsenic distribution in aquifers of the Datong basin, China: Constraints from elemental geochemistry

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

Xie, Xianjun; Wang, Yanxin; Ellis, Andre

Arsenic (As)-contaminated aquifer sediments from Datong basin, China have been analyzed to infer the provenance and depositional environment related to As distribution in the aquifer sediments. The As content in the sediments ranged from 2.45 to 27.38 mg/kg with an average value of 9.54 mg/kg, which is comparable to the average value in modern unconsolidated sediments. However, minor variation in As concentration with depth has been observed in the core. There was a significant correlation between Fe, and Al and As, which was attributed to the adsorption or co-precipitation of As onto/with Fe oxides/hydroxides and/or Fe-coated clay minerals. Post-Archean Australianmore » Shale (PAAS)-normalized REEs patterns of sediment samples along the borehole were constant, and the sediments had a notably restricted range of La-N/Yb-N ratios from 0.7 to 1.0. These results suggested that the provenance of the Datong basin remained similar throughout the whole depositional period. The analysis of major geochemical compositions confirmed that all core sediments were from the same sedimentary source and experienced significant sedimentary recycling. The co-variation of As, V/Al, Ni/Al and chemical index of alteration (CIA) values in the sediments along the borehole suggested that As distribution in the sediments was primarily controlled by weathering processes. The calculated CIA values of the sediments along the borehole indicate that a relative strong chemical weathering occurred during the deposition of sediments at depths of similar to 35 to 88 m, which was corresponding to the depth at which high As groundwater was observed at the site. Strong chemical weathering favored the deposition of Fe-bearing minerals including poorly crystalline and crystalline Fe oxide mineral phases and concomitant co-precipitation of As with these minerals in the sediments. Subsequent reductive dissolution of As-bearing poorly crystalline and crystalline Fe oxides would result in the enrichment of As in groundwater. In general, the chemical weathering during the deposition of the sediments governed the co-accumulation of Fe oxides and As in the aquifer sediments. And then, the reductive dissolution of Fe oxides/hydroxides is the mechanism of As enrichment in the groundwater in the Datong basin« less

Anaerobic Redox Cycling of Iron by Freshwater Sediment Microorganisms

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

Weber, Karrie A.; Urrutia, Matilde M.; Churchill, Perry F.

2006-01-01

The potential for microbially-mediated anaerobic redox cycling of iron (Fe) was examined in a first-generation enrichment culture of freshwater wetland sediment microorganisms. MPN enumerations revealed the presence of significant populations of Fe(III)-reducing (ca. 108 cells mL-1) and Fe(II)-oxidizing, nitrate-reducing organisms (ca. 105 cells mL-1) in the sediment used to inoculate the enrichment cultures. Nitrate reduction commenced immediately following inoculation of acetate-containing (ca. 1 mM) medium with a small quantity (1% vol/vol) of wetland sediment, and resulted in the transient accumulation of NO2- and production of a mixture of end-products including NH4+. Fe(III) oxide (high surface area goethite) reduction took placemore » - after NO3- was depleted and continued until all the acetate was utilized. Addition of NO3 after Fe(III) reduction ceased resulted in the immediate oxidation of Fe(II) coupled to reduction of + NO3-to NH4 . No significant NO2- accumulation was observed during nitrate-dependent Fe(II) oxidation. No Fe(II) oxidation occurred in pasteurized controls. Microbial community structure in the enrichment was monitored by DGGE analysis of PCR amplified 16s rDNA and RT-PCR amplified 16S rRNA, as well as by construction of 16S rDNA clone libraries for four different time points during the experiment. Strong similarities in dominant members of the microbial community were observed in the Fe(III) reduction and nitrate-dependent Fe(II) oxidation phases of the experiment, specifically the common presence of organisms closely related (= 95% sequence similarity) to the genera Geobacter and Dechloromonas. These results indicate that the wetland sediments contained organisms such as Geobacter sp. which are capable of both + dissimilatory Fe(III) reduction and oxidation of Fe(II) with reduction of NO3-reduction to NH4 . Our findings suggest that microbially-catalyzed nitrate-dependent Fe(II) oxidation has the potential to contribute to a dynamic anaerobic Fe redox cycle in freshwater sediments.« less

Sedimentary Phosphorus Dynamics in a Coastal Louisiana Prograding Delta

NASA Astrophysics Data System (ADS)

Upreti, K.; Maiti, K.; Rivera-Monroy, V. H.

2016-02-01

A number of studies have quantified phosphorus (P) concentration and sediment-water column exchange undergoing changes in redox condition in the Louisiana delta plain. However, there is not information on the potential role of bacteria in P transformations in Louisiana coastal wetlands. The main objective of this work was to evaluate sedimentary P dynamics by identifying dominant forms of P in sediments and determine the magnitude of P mobilization during bacterially mediated redox reactions. Sediment samples were collected from three sites (ridge, interior, and channel) characterized by variation in the vegetation and elevation in the currently prograding Wax Lake Delta. Sediments were incubated with and without the bacterium Shewanella putrefaciencs CN32 (Sp-CN32), which is an iron reducing bacteria that consumes dissolved oxygen and leads to reduction of Fe III to Fe II thereby releasing PO43- bound to Fe III oxide. Our results revealed that P release in sediments spiked with Sp-CN32 was significantly higher in all sediments when compared to sediments in natural condition. P release from sediment spiked with Sp-CN32 significantly increased from 0.064 to 1.460 umoles/g in the sediment sampled at high elevation (ridge) and from 0.079 to 2.407 moles/g in the medium elevation area (interior) of the island. This increase in P release was significantly correlated with an increase in Fe (II) concentrations. The extent of P release was proportionally higher than the Fe (II) measured in all sediments. The P/Fe ratio steadily increased for the first 24 h followed by a rapid decrease. This temporal trend suggests a lag in Fe (III) reduction and an initial bacterial uptake and release of loosely sorbed NaHCO3-P pool when Sp-CN32 respired on O2 as the terminal electron acceptor. This study contributes to our understanding of the release mechanism of P during bacterial mediated redox reaction in wetland soils undergoing pulsing sediment deposition.

Successful control of internal phosphorus loading after sediment dredging for 6years: A field assessment using high-resolution sampling techniques.

PubMed

Chen, Musong; Cui, Jingzhen; Lin, Juan; Ding, Shiming; Gong, Mengdan; Ren, Mingyi; Tsang, Daniel C W

2018-03-01

The effectiveness of sediment dredging for the control of internal phosphorus (P) loading, was investigated seasonally in the eutrophic Lake Taihu. The high-resolution dialysis (HR-Peeper) and diffusive gradients in thin films (DGT) techniques were used to measure the concentrations of soluble Fe(II) and soluble reactive P (SRP) as well as DGT-labile Fe/P in the non-dredging and post-dredging sediments. The P resupply kinetics from sediment solids were interpreted using DGT Induced Fluxes in Sediments (DIFS) modeling. The results showed no obvious improvement in water and sediment quality after dredging for 6years, due to their geographical proximity (a line distance of approximately 9km). However, dredging significantly decreased the concentrations of soluble Fe(II)/SRP and DGT-labile Fe/P in sediments, with effects varying at different depths below the sediment-water interface; More pronounced effects appeared in January and April. The diffusive flux of pore water SRP from sediments decreased from 0.746, 4.08 and 0.353mg/m 2 /d to 0.174, 1.58 and 0.048mg/m 2 /d in April, July and January, respectively. DIFS modeling indicated that the P retention capability of sediment solids was improved in April in post-dredging site. Positive correlations between pore water soluble Fe(II) and SRP as well as between DGT-labile Fe and P, reflect the key role of Fe redox cycling in regulating dredging effectiveness. This effect is especially important in winter and spring, while in summer and autumn, the decomposition of algae promoted the release of P from sediments and suppressed dredging effectiveness. Overall, the high-resolution HR-Peeper and DGT measurements indicated a successful control of internal P loading by dredging, and the post-dredging effectiveness was suppressed by algal bloom. Copyright © 2017 Elsevier B.V. All rights reserved.

Formation of ferric iron crusts in Quaternary sediments of Lake Baikal, Russia, and implications for paleoclimate

USGS Publications Warehouse

Deike, R.G.; Granina, L.; Callender, E.; McGee, J.J.

1997-01-01

Phosphate-bearing, ferric iron and siliceous crusts ranging in age from Recent to approximately 65,000 yr B.P. are observed in sediments of Lake Baikal. In younger sediments the crusts are at the base of a spectrum of secondary iron and manganese oxides that accumulate near the sediment/water interface in the zone of positive oxidation potential beneath an oxygenated water column. In areas where the average Quaternary sedimentation rates have been slow (e.g. 0.026 mm/yr), the crusts are more common, and span a wider range of ages. No crusts have been found where the Quaternary sedimentation mode has been deltaic and rapid (0.15 mm/yr). Independent core correlation based on magnetic properties of the sediment suggests that crusts can be correlated over most of Academician Ridge, an area that is particularly sensitive to climatic events affecting the concentration of suspended sediment. These crusts may be indicative of periods of low suspended sediment concentration, which occur during sustained transitions from glacial periods of high detrital input, to interglacial periods of high diatom sedimentation. The crusts are dominated by iron-rich and siliceous amorphous mineral phases, with an FeO:SiO2 by weight of 3:1. Regardless of age or location in the lake the Fe phase always includes Ca, P and Mn. Extensive microprobe data for these four elements recast as normalized elemental weight percent reveal linear trends of Ca:P and Fe:P. With increasing P, Ca also increases such that the two elements maintain a linear relationship passing very close to the origin and with a mean molar Ca:P=0.3 (too low for well-characterized apatite). Conversely, with increasing P, Fe decreases (mean molar Fe:P=3.4). There is no correlation between Mn and P. Molar Fe:P ratios for vivianite (an Fe(II) phosphate mineral observed in sediments closely below some crusts) are clustered around a stoichiometric composition. The covariant increase in Ca:P and the corresponding decrease in Fe:P may be explained by: (1) coupled adsorption of aqueous Ca and P by a colloidal ferric hydrous oxide; (2) loss of Fe from a Ca-P-Fe phase; or (3) oxidation of vivianite to a metastable mineral phase that gradually loses Ca and gains Fe. The first explanation is favored, because there is no petrographic evidence for either the existence of an originating Ca-P-Fe phase, or, for the oxidation of vivianite. Further, it is suggested that by continually equalizing surface charge, Ca allows more phosphate to be adsorbed leading to thicker crusts and longer preservation after burial.

Sources and distribution of yttrium and rare earth elements in surface sediments from Tagus estuary, Portugal.

PubMed

Brito, Pedro; Prego, Ricardo; Mil-Homens, Mário; Caçador, Isabel; Caetano, Miguel

2018-04-15

The distribution and sources of yttrium and rare-earth elements (YREE) in surface sediments were studied on 78 samples collected in the Tagus estuary (SW Portugal, SW Europe). Yttrium and total REE contents ranged from 2.4 to 32mg·kg -1 and 18 to 210mg·kg -1 , respectively, and exhibited significant correlations with sediment grain-size, Al, Fe, Mg and Mn, suggesting a preferential association to fine-grained material (e.g. aluminosilicates but also Al hydroxides and Fe oxyhydroxides). The PAAS (Post-Archean Australian Shale) normalized patterns display three distinct YREE fractionation pattern groups along the Tagus estuary: a first group, characterized by medium to coarse-grained material, a depleted and almost flat PAAS-normalized pattern, with a positive anomaly of Eu, representing one of the lithogenic components; a second group, characterized mainly by fine-grained sediment, with higher shale-normalized ratios and an enrichment of LREE relative to HREE, associated with waste water treatment plant (WWTP) outfalls, located in the northern margin; and, a third group, of fine-grained material, marked by a significant enrichment of Y, a depletion of Ce and an enrichment of HREE over LREE, located near an inactive chemical-industrial complex (e.g. pyrite roast plant, chemical and phosphorous fertilizer industries), in the southern margin. The data allow the quantification of the YREE contents and its spatial distribution in the surface sediments of the Tagus estuary, identifying the main potential sources and confirming the use of rare earth elements as tracers of anthropogenic activities in highly hydrodynamic estuaries. Copyright © 2017 Elsevier B.V. All rights reserved.

Reactive Fe(II) layers in deep-sea sediments

NASA Astrophysics Data System (ADS)

König, Iris; Haeckel, Matthias; Drodt, Matthias; Suess, Erwin; Trautwein, Alfred X.

1999-05-01

The percentage of the structural Fe(II) in clay minerals that is readily oxidized to Fe(III) upon contact with atmospheric oxygen was determined across the downcore tan-green color change in Peru Basin sediments. This latent fraction of reactive Fe(II) was only found in the green strata, where it proved to be large enough to constitute a deep reaction layer with respect to the pore water O 2 and NO 3-. Large variations were detected in the proportion of the reactive Fe(II) concentration to the organic matter content along core profiles. Hence, the commonly observed tan-green color change in marine sediments marks the top of a reactive Fe(II) layer, which may represent the major barrier to the movement of oxidation fronts in pelagic subsurface sediments. This is also demonstrated by numerical model simulations. The findings imply that geochemical barriers to pore water oxidation fronts form diagenetically in the sea floor wherever the stage of iron reduction is reached, provided that the sediments contain a significant amount of structural iron in clay minerals.

Metals in sediments and fish from Sea Lots and Point Lisas harbors, Trinidad and Tobago

USGS Publications Warehouse

Mohammed, Azad; May, Thomas; Echols, Kathy; Walther, Mike; Manoo, Anton; Maraj, Dexter; Agard, John; Orazio, Carl

2012-01-01

Concentrations of heavy metals were determined in nearshore marine sediments and fish tissue from Sea Lots area on the west coast, at Caroni Lagoon National Park, and in the Point Lisas harbor, Trinidad. The most dominant metals found in sediments were Al, Fe and Zn with mean concentrations highest at Sea Lots (Al-39420 μg/g; Fe-45640 μg/g; Zn-245 μg/g), when compared to sediments from Point Lisas (Al-11936 μg/g; Fe-30171 μg/g; Zn-69 μg/g) and Caroni (Al-0400 μg/g; Fe-19000 μg/g; Zn-32 μg/g), High concentration of Cu, Al, Fe and Zn were also detected in fish tissue from Point Lisas and Caroni. Metal concentrations in fish tissue showed significant correlation with sediment metals concentration, which suggests that tissue levels are influenced by sediment concentration. Of the metals, only Zn, Hg and Cu had a bioaccumulation factor (BAF) greater than one, which suggests a high bioaccumulation potential for these metals.

Mineral-Association and Activity of Bacteria and Archaea in the Deep Subsurface South Pacific Gyre Sediment

NASA Astrophysics Data System (ADS)

Steele, J. A.; Dekas, A. E.; Harrison, B. K.; Morono, Y.; Inagaki, F.; Ziebis, W.; Orphan, V. J.

2012-12-01

Although the subsurface biosphere is now recognized as an important reservoir of life on our planet, until recently the microbial community beneath open-ocean oligotrophic gyres (making up the majority of the seafloor) has just begun to be studied in detail. IODP Expedition 329 and the KNOX-022RR site survey cruise have taken some of the first steps at characterizing the microbial community beneath the South Pacific Gyre, a region with low organic carbon burial rates (10-8 and 10-10 moles C cm-1 yr-1), deep oxygen penetration (sediments are oxidized to the basement), and low prokaryotic cell counts (106 cells cm-3 to <103 cells cm-3). In these sediments, the dominant fraction of organic carbon may be aggregated or adsorbed to minerals, suggesting that microbes that are able to grow on the minerals may create potential "hotspots" of activity. In this study, we performed magnetic separation on oligotrophic sediment samples and examined the bacterial and archaeal communities using 16S rRNA tag sequencing. To determine if the mineral-associated cells were autotrophic and/or utilizing nitrate, we performed long-term (20 month) incubations with 13CO2 and 15NO3- from sediment taken at depths ~2-70 mbsf beneath the oligotrophic gyre and outside of the oligotrophic gyre (IODP Exp. 329 stations U1368-U1371). Subsequently we used the DNA stain SYBR Green I, and CARD-FISH-NanoSIMS to identify cells which were actively taking up the isotopic label. We then used SEM-EDS to identify the mineral particle composition. Preliminary results found the magnetic fraction in oligotrophic sediment (KNOX-022RR station SPG-5) from 1.2-2.6 mbsf showed a greater diversity of both bacteria and archaea. OTUs from Chloroflexi groups SO85 and SAR202 were dominant in the magnetic fraction. Firmicutes, Bacteroidetes, δ-Proteobacteria, Verrucomicrobia, Deferribacteres, WS3, OP10, and OP1 OTUs were found only in the magnetic fraction. Crenarchaeal OTUs from Marine Benthic Group B and Marine Group I (Thaumarchaea) and Euryarchaeal OTUs from Methanomicrobia and Thermococcus groups were found in the magnetic fraction with Marine Group I Crenarchaea showing the highest archaeal abundance. The higher diversity in the magnetic fraction suggests that bacteria and archaea associated with Fe-rich or Mn-rich minerals may be able to exploit a wider array of niches. Comparing sediment from within and outside the gyre, the more productive sediments had greater total cell numbers; however, we observed an increase in attached cells in the relatively Fe and P-rich samples (the heavy fraction) in the oligotrophic sediments (IODP Exp. 329 station U1368 and KNOX-022RR station SPG-6), suggesting a possible preference for attachment to Fe and P-rich particles.

Nanoscale Titanium Dioxide (nTiO2) Transport in Water-Saturated Natural Sediments: Influence of Soil Organic Matter and Fe/Al Oxyhydroxides

NASA Astrophysics Data System (ADS)

Fisher-Power, L.; Cheng, T.

2017-12-01

Transport of engineered nanoparticles (ENP) in subsurface environments has important implications to water quality and soil contamination. Although extensive research has been conducted to understand the effects of water chemistry on ENP transport, less attention has been paid to influences from the transport medium/matrix. The objective of this research is to investigate the effects of natural organic matter (NOM) and Fe/Al oxyhydroxides in a natural sediment on ENP transport. A sediment was collected and separated into four portions, one of which was unmodified, and the others treated to remove specific components (organic matter, Fe/Al oxyhydroxides, or both organic matter and Fe/Al oxyhydroxides). Transport of nanoscale titanium dioxide (nTiO2) in columns packed with quartz sand and each of the four types of the sediment under water-saturated conditions was studied. Our results showed that nTiO2 transport was strongly influenced by pH and sediment composition. When influent pH = 5, nTiO2 transport in all the sediments was low, as positively-charged nTiO2 was attracted to negatively charged NOM, quartz, and other minerals. nTiO2 transport was slightly enhanced in columns packed with untreated sediment or Fe/Al oxyhydroxides removed sediment due to dissolved organic matter generated by the partial dissolution of NOM, which adsorbed onto nTiO2 surface and reversed its zeta potential to negative. When influent pH = 9, nTiO2 transport was generally high since negatively-charged nTiO2 was repelled by negatively charged transport medium. However, in columns packed with the organic matter removed sediment or the Fe/Al oxyhydroxides removed sediment, nTiO2 transport was low. This was attributable to pH buffering by the sediment, which decreased pore water pH in the column, resulting in zeta potential change and electrostatic attraction between Fe/Al oxyhydroxides and nTiO2. This research demonstrates that electrostatic forces between nTiO2 and mineral/organic components in natural sediments is a key factor that controls nTiO2 retention and transport, and that both NOM and Fe/Al oxyhydroxides may substantially influence nTiO2 transport.

Monitoring Tc dynamics in a bioreduced sediment: an investigation with gamma camera imaging of (99m)Tc-pertechnetate and (99m)Tc-DTPA.

PubMed

Vandehey, Nicholas T; O'Neil, James P; Slowey, Aaron J; Boutchko, Rostyslav; Druhan, Jennifer L; Moses, William W; Nico, Peter S

2012-11-20

We demonstrate the utility of nuclear medical imaging technologies and a readily available radiotracer, [(99m)Tc]TcO(4)(-), for the noninvasive monitoring of Fe(II) production in acetate-stimulated sediments from Old Rifle, CO, USA. Microcosms consisting of sediment in artificial groundwater media amended with acetate were probed by repeated injection of radiotracer over three weeks. Gamma camera imaging was used to noninvasively quantify the rate and extent of [(99m)Tc]TcO(4)(-) partitioning from solution to sediment. Aqueous Fe(II) and sediment-associated Fe(II) were also measured and correlated with the observed tracer behavior. For each injection of tracer, curves of (99m)Tc concentration in solution vs time were fitted to an analytic function that accounts for both the observed rate of sedimentation as well as the rate of (99m)Tc association with the sediment. The rate and extent of (99m)Tc association with the biostimulated sediment correlated well with the production of Fe(II), and a mechanism of [(99m)Tc]TcO(4)(-) reduction via reaction with surface-bound Fe(II) to form an immobile Tc(IV) species was inferred. After three weeks of bioreduction, a subset of microcosms was aerated in order to reoxidize the Fe(II) to Fe(III), which also destroyed the affinity of the [(99m)Tc]TcO(4)(-) for the sediments. However, within 3 days postoxidation, the rate of Tc(VII) reduction was faster than immediately before oxidation implying a rapid return to more extensive bioreduction. Furthermore, aeration soon after a tracer injection showed that sediment-bound Tc(IV) is rapidly resolubilized to Tc(VII). In contrast to the [(99m)Tc]TcO(4)(-), a second commercially available tracer, (99m)Tc-DTPA (diethylenetriaminepentaacetic acid), had minimal association with sediment in both controls and biostimulated sediments. These experiments show the promise of [(99m)Tc]TcO(4)(-) and (99m)Tc-DTPA as noninvasive imaging probes for a redox-sensitive radiotracer and a conservative flow tracer, respectively.

Mössbauer spectroscopic studies on the iron forms of deep-sea sediments

NASA Astrophysics Data System (ADS)

Drodt, M.; Trautwein, A. X.; König, I.; Suess, E.; Koch, C. Bender

Mössbauer spectroscopy was applied to characterize the valence states Fe(II) and Fe(III) in sedimentary minerals from a core of the Peru Basin. The procedure in unraveling this information includes temperature-dependent measurements from 275 K to very low temperature (300 mK) in zero-field and also at 4.2 K in an applied field (up to 6.2 T) and by mathematical procedures (least-squares fits and spectral simulations) in order to resolve individual spectral components. The depth distribution of the amount of Fe(II) is about 11% of the total Fe to a depth of 19 cm with a subsequent steep increase (within 3 cm) to about 37%, after which it remains constant to the lower end of the sediment core (at about 40 cm). The steep increase of the amount of Fe(II) defines a redox boundary which coincides with the position where the tan/green color transition of the sediment occurs. The isomer shifts and quadrupole splittings of Fe(II) and Fe(III) in the sediment are consistent with hexacoordination by oxygen or hydroxide ligands as in oxide and silicate minerals. Goethite and traces of hematite are observed only above the redox boundary, with a linear gradient extending from about 20% of the total Fe close to the sediment surface to about zero at the redox boundary. The superparamagnetic relaxation behavior allows to estimate the order of magnitude for the size of the largest goethite and hematite particles within the particle-site distribution, e.g. 170 Å and 50 Å, respectively. The composition of the sediment spectra recorded at 300 mK in zero-field, apart from the contributions due to goethite and hematite, resembles that of the sheet silicates smectite, illite and chlorite, which have been identified as major constituents of the sediment in the <2 μm fraction by X-ray diffraction. The specific ``ferromagnetic'' type of magnetic ordering in the sediment, as detected at 4.2 K in an applied field, also resembles that observed in sheet silicates and indicates that both Fe(II) and Fe(III) are involved in magnetic ordering. This ``ferromagnetic'' behavior is probably due to the double-exchange mechanism known from other mixed-valence Fe(II)-Fe(III) systems. A significant part of the clay-mineral iron is redox sensitive. It is proposed that the color change of the sediment at the redox boundary from tan to green is related to the increase of Fe(II)-Fe(III) pairs in the layer silicates, because of the intervalence electron transfer bands which are caused by such pairs.

Geochemistry and Mineralogy of Western Australian Salt Lake Sediments: Implications for Meridiani Planum on Mars.

PubMed

Ruecker, A; Schröder, C; Byrne, J; Weigold, P; Behrens, S; Kappler, A

2016-07-01

Hypersaline lakes are characteristic for Western Australia and display a rare combination of geochemical and mineralogical properties that make these lakes potential analogues for past conditions on Mars. In our study, we focused on the geochemistry and mineralogy of Lake Orr and Lake Whurr. While both lakes are poor in organic carbon (<1%), the sediments' pH values differ and range from 3.8 to 4.8 in Lake Orr and from 5.4 to 6.3 in Lake Whurr sediments. Lake Whurr sediments were dominated by orange and red sediment zones in which the main Fe minerals were identified as hematite, goethite, and tentatively jarosite and pyrite. Lake Orr was dominated by brownish and blackish sediments where the main Fe minerals were goethite and another paramagnetic Fe(III)-phase that could not be identified. Furthermore, a likely secondary Fe(II)-phase was observed in Lake Orr sediments. The mineralogy of these two salt lakes in the sampling area is strongly influenced by events such as flooding, evaporation, and desiccation, processes that explain at least to some extent the observed differences between Lake Orr and Lake Whurr. The iron mineralogy of Lake Whurr sediments and the high salinity make this lake a suitable analogue for Meridiani Planum on Mars, and in particular the tentative identification of pyrite in Lake Whurr sediments has implications for the interpretation of the Fe mineralogy of Meridiani Planum sediments. Western Australia-Salt lakes-Jarosite-Hematite-Pyrite-Mars analogue. Astrobiology 16, 525-538.

Iron isotope constraints on arsenic release from Mekong Delta sediments, Cambodia

NASA Astrophysics Data System (ADS)

Matsumoto, T.; Yamaguchi, K. E.; Hirata, T.; Yamagata, Y.; Yamaguchi, A.; Abe, G.

2017-12-01

Arsenic-contaminated groundwater is a world-wide environmental problem and threatens more than 100 million people living in delta areas of South, SE and East Asia. It is typically associated with reducing aquifers with organic-rich alluvial sediments, little thermal gradients, low sulfate concentrations, and slow flushing rates. Such conditions are typical for low-lying countries in Asian deltas; however, compared to Bangladesh, Cambodia has received far less attention. Upon reductive dissolution of Fe-(oxyhydr)oxides that adsorbed As, Fe and As are released into solution as dissolved Fe2+ and arsenate, respectively. Following the oxidation of dissolved Fe2+, newly-formed Fe-(oxyhydr)oxides adsorb As again. Thus, in anoxic waters, concentrations of As correlate with those of dissolved Fe2+. Fluctuating redox conditions in the aquifer are control As release, although inhibition of adsorption of arsenate and arsenite onto the Fe-(oxyhydr)oxides occurs when the concentrations of phosphate, bicarbonate, silicate, and/or organic matter become sufficiently high. Biogeochemical redox reactions of Fe result in significant isotope fractionation (e.g., Johnson et al., 2008). We hypothesized that magnitude of isotope fractionation of Fe in the aquifer sediments, reflecting repeated (incomplete) redox reactions of Fe, may be proportional to the amount of total As release. We aim to calibrate the As release from aquifer sediment by Fe isotope analysis. As a preliminary study, series of sediment samples were collected from the Mekong Delta, Cambodia, in September 2016. Based on measurements by XRF, ICP-AES and ICP-MS, concentrations of As varied significantly covering the range from 4.5 to 15.5 µg/g with a median value of 11 µg/g (higher than the average crustal value of 5 µg/g), and those of Fe is from 2.6 to 9.7 wt.% with a median value of 7.1 wt.%. Concentrations of As and Fe show positive correlation (R2 = 0.72), indicating an effective redox cycling of Fe and As as stated above. Sediment incubation experiment to explore various pathways of As release would show time-series correlated changes in the Fe isotope compositions and As concentrations. The data obtained here are essential in investigating the mechanism of As release.

Role of microbial Fe(III) reduction and solution chemistry in aggregation and settling of suspended particles in the Mississippi River Delta plain, Louisiana, USA

USGS Publications Warehouse

Jaisi, Deb P.; Ji, Shanshan; Dong, Hailiang; Blake, Ruth E.; Eberl, Dennis D.; Kim, Jinwook

2008-01-01

River-dominated delta areas are primary sites of active biogeochemical cycling, with productivity enhanced by terrestrial inputs of nutrients. Particle aggregation in these areas primarily controls the deposition of suspended particles, yet factors that control particle aggregation and resulting sedimentation in these environments are poorly understood. This study was designed to investigate the role of microbial Fe(III) reduction and solution chemistry in aggregation of suspended particles in the Mississippi Delta. Three representative sites along the salinity gradient were selected and sediments were collected from the sediment-water interface. Based on quantitative mineralogical analyses 88–89 wt.% of all minerals in the sediments are clays, mainly smectite and illite. Consumption of SO42− and the formation of H2S and pyrite during microbial Fe(III) reduction of the non-sterile sediments by Shewanella putrefaciens CN32 in artificial pore water (APW) media suggest simultaneous sulfate and Fe(III) reduction activity. The pHPZNPC of the sediments was ≤3.5 and their zeta potentials at the sediment-water interface pH (6.9–7.3) varied from −35 to −45 mV, suggesting that both edges and faces of clay particles have negative surface charge. Therefore, high concentrations of cations in pore water are expected to be a predominant factor in particle aggregation consistent with the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Experiments on aggregation of different types of sediments in the same APW composition revealed that the sediment with low zeta potential had a high rate of aggregation. Similarly, addition of external Fe(II) (i.e. not derived from sediments) was normally found to enhance particle aggregation and deposition in all sediments, probably resulting from a decrease in surface potential of particles due to specific Fe(II) sorption. Scanning and transmission electron microscopy (SEM, TEM) images showed predominant face-to-face clay aggregation in native sediments and composite mixtures of biopolymer, bacteria, and clay minerals in the bioreduced sediments. However, a clear need remains for additional information on the conditions, if any, that favor the development of anoxia in deep- and bottom-water bodies supporting Fe(III) reduction and resulting in particle aggregation and sedimentation.

Geophysical constraints on Rio Grande rift structure and stratigraphy from magnetotelluric models and borehole resistivity logs, northern New Mexico

USGS Publications Warehouse

Rodriguez, Brian D.; Sawyer, David A.; Hudson, Mark R.; Grauch, V.J.S.

2013-01-01

Two- and three-dimensional electrical resistivity models derived from the magnetotelluric method were interpreted to provide more accurate hydrogeologic parameters for the Albuquerque and Española Basins. Analysis and interpretation of the resistivity models are aided by regional borehole resistivity data. Examination of the magnetotelluric response of hypothetical stratigraphic cases using resistivity characterizations from the borehole data elucidates two scenarios where the magnetotelluric method provides the strongest constraints. In the first scenario, the magnetotelluric method constrains the thickness of extensive volcanic cover, the underlying thickness of coarser-grained facies of buried Santa Fe Group sediments, and the depth to Precambrian basement or overlying Pennsylvanian limestones. In the second scenario, in the absence of volcanic cover, the magnetotelluric method constrains the thickness of coarser-grained facies of buried Santa Fe Group sediments and the depth to Precambrian basement or overlying Pennsylvanian limestones. Magnetotelluric surveys provide additional constraints on the relative positions of basement rocks and the thicknesses of Paleozoic, Mesozoic, and Tertiary sedimentary rocks in the region of the Albuquerque and Española Basins. The northern extent of a basement high beneath the Cerros del Rio volcanic field is delineated. Our results also reveal that the largest offset of the Hubbell Spring fault zone is located 5 km west of the exposed scarp. By correlating our resistivity models with surface geology and the deeper stratigraphic horizons using deep well log data, we are able to identify which of the resistivity variations in the upper 2 km belong to the upper Santa Fe Group sediment

Evaluation of Fe(II) oxidation at an acid mine drainage site using laboratory-scale reactors

NASA Astrophysics Data System (ADS)

Brown, Juliana; Burgos, William

2010-05-01

Acid mine drainage (AMD) is a severe environmental threat to the Appalachian region of the Eastern United States. The Susquehanna and Potomac River basins of Pennsylvania drain to the Chesapeake Bay, which is heavily polluted by acidity and metals from AMD. This study attempted to unravel the complex relationships between AMD geochemistry, microbial communities, hydrodynamic conditions, and the mineral precipitates for low-pH Fe mounds formed downstream of deep mine discharges, such as Lower Red Eyes in Somerset County, PA, USA. This site is contaminated with high concentrations of Fe (550 mg/L), Mn (115 mg/L), and other trace metals. At the site 95% of dissolved Fe(II) and 56% of total dissolved Fe is removed without treatment, across the mound, but there is no change in the concentration of trace metals. Fe(III) oxides were collected across the Red Eyes Fe mound and precipitates were analyzed by X-ray diffraction, electron microscopy and elemental analysis. Schwertmannite was the dominant mineral phase with traces of goethite. The precipitates also contained minor amounts of Al2O3, MgO,and P2O5. Laboratory flow-through reactors were constructed to quantify Fe(II) oxidation and Fe removal over time at terrace and pool depositional facies. Conditions such as residence time, number of reactors in sequence and water column height were varied to determine optimal conditions for Fe removal. Reactors with sediments collected from an upstream terrace oxidized more than 50% of dissolved Fe(II) at a ten hour residence time, while upstream pool sediments only oxidized 40% of dissolved Fe(II). Downstream terrace and pool sediments were only capable of oxidizing 25% and 20% of Fe(II), respectively. Fe(II) oxidation rates measured in the reactors were determined to be between 3.99 x 10-8and 1.94 x 10-7mol L-1s-1. The sediments were not as efficient for total dissolved Fe removal and only 25% was removed under optimal conditions. The removal efficiency for all sediments decreased as residence time decreased and as water column depth increased. Control reactors with Co-60 irradiated sediments showed an increase in Fe concentration as a result of dissolution of the sediments; thus, it was concluded that Fe(II) oxidation in the reactors was a result of biological processes and not abiotic oxidation. It was also concluded that Fe(II) oxidation and removal rates were dependent upon geochemical gradients (pH, Fe(II) concentration) rather than depositional facies. Fluorescent in situ hybridization was also performed on field and reactor samples to determine which microbial communities were responsible for the highest Fe(II) oxidation rates.

Isolation and Characterization of Microbes Mediating Thermodynamically Favorable Coupling of Anaerobic Oxidation of Methane and Metal Reduction

NASA Astrophysics Data System (ADS)

Glass, J. B.; Reed, B. C.; Sarode, N. D.; Kretz, C. B.; Bray, M. S.; DiChristina, T. J.; Stewart, F. J.; Fowle, D. A.; Crowe, S.

2014-12-01

Methane is the third most reduced environmentally relevant electron donor for microbial metabolisms after organic carbon and hydrogen. In anoxic ecosystems, the major sink for methane is anaerobic oxidation of methane (AOM) mediated by syntrophic microbial consortia that couple AOM to reduction of an oxidized electron acceptor to yield free energy. In marine sediments, AOM is generally coupled to reduction of sulfate despite an extremely small amount of free energy yield because sulfate is the most abundant electron acceptor in seawater. While AOM coupled to Fe(III) and Mn(IV) reduction (Fe- and Mn-AOM) is 10-30x more thermodynamically favorable than sulfate-AOM, and geochemical data suggests that it occurs in diverse environments, the microorganisms mediating Fe- and Mn-AOM remain unknown. Lake Matano, Indonesia is an ideal ecosystem to enrich for Fe- and Mn-AOM microbes because its anoxic ferruginous deep waters and sediments contain abundant Fe(III), Mn(IV) and methane, and extremely low sulfate and nitrate. Our research aims to isolate and characterize the microbes mediating Fe- and Mn-AOM from three layers of Lake Matano sediments through serial enrichment cultures in minimal media lacking nitrate and sulfate. 16S rRNA amplicon sequencing of sediment inoculum revealed the presence of the Fe(III)-reducing bacterium Geobacter (5-10% total microbial community in shallow sediment and 35-60% in deeper sediment) as well as 1-2% Euryarchaeota implicated in methane cycling, including ANME-1 and 2d and Methanosarcinales. After 90 days of primary enrichment, all three sediment layers showed high levels of Fe(III) reduction (60-90 μM Fe(II) d-1) in the presence of methane compared to no methane and heat-killed controls. Treatments with added Fe(III) as goethite contained higher abundances of Geobacter than the inoculum (60-80% in all layers), suggesting that Geobacter may be mediating Fe(III) reduction in these enrichments. Quantification of AOM rates is underway, and will be used to estimate the plausibility of metal-AOM as a thermodynamically favorable methane sink in anoxic ecosystems of both the modern and ancient Earth.

Sulfur diagenesis in marine sediments

NASA Technical Reports Server (NTRS)

Goldhaber, M.

1985-01-01

Bacterial sulfate reduction occurs in all marine sediments that contain organic matter. Aqueous sulfide (HS-, H2S), one of the initial products of bacterial sulfide reduction, is extremely reactive with iron bearing minerals: sulfur is fixed into sediments as iron sulfide (first FeS and then Fe2S2). A working definition is given of sulfur diagenesis in marine sediments. Controls and consequences of sulfate reduction rates in marine sediments are examined.

Geochemical normalization of magnetic susceptibility - a simple tool for distinction the sediment provenance and post-depositional processes in floodplain sediments

NASA Astrophysics Data System (ADS)

Famera, Martin; Matys Grygar, Tomas; Elznicova, Jitka

2017-04-01

Magnetic susceptibility is highly appreciated in sedimentary and environmental geology. It may also reflect provenance of the sediment and post-depositional changes therein, including soil-forming processes. We studied the applicability of Fe-normalization of mass-specific magnetic susceptibility (MS) and Ti-normalization of Fe concentrations in description of fluvial sediments from five different catchments. We dealt with two catchments with some "mafic" source rocks (Fe-rich rocks) and three almost purely "felsic" catchments (source rocks with dominant quartz and feldspars). The fine-grained floodplain sediments (from clayey silts to fine sands) were obtained by drill coring and analysed for Fe and Ti concentrations using X-ray fluorescence spectroscopy (EDXRF) and MS using kappabridge. To correct MS for the sedimentological grain-size effects and possible magnetic enrichment, we used background functions constructed in the same way like for heavy metals. The representative profiles downward the floodplain sediments demonstrate the following MS stratigraphy: (1) 15-50 cm thick top stratum A, usually with MS and heavy metal enrichment, (2) underlying stratum B with stable values of MS, MS/Fe and Fe/Ti and (3) the lowermost stratum C with variable Fe concentrations and MS and high-chroma reductimorphic features due to micro-accumulations of Fe and Mn oxides in discoloured matrix, or grey colour due to permanently removed Fe(III) oxide pigment. The boundary between strata B and C can be at a depth of several decimetres to more than 1 metre depending on the thickness of floodplain fines, site-specific river incision and water table fluctuation. For the construction of MS background functions we used Fe concentrations as an independent variable (a predictor). It allows for calculation of MS of sediments as it would not be affected by post-depositional changes and pollution. Pristine MS is than predicted for any sample using formula MS_PRISTINE = const·cFe + const', where cFe is concentration of Fe. Background functions must be obtained empirically from collection of samples of stratum B that needs qualified sampling strategy and informed data evaluation. Local enrichment factor of MS is then defined as LEF MS = MS/MS_PRISTINE. LEF MS is useful for study of MS depth profiles in both strata A and C. Floodplain sediments in river systems with catchment with "mafic" rock outcrops have MSPRISTINE by up to two orders of magnitude larger in comparison to systems with "felsic" source rocks. The carriers of magnetic signal in the "mafic" rock-derived sediments are affected by soil-forming processes, which gradually decrease their original MS, in particular in strata B and C. Post-depositional processes including pedogenesis, in particular reductimorphic processes, may thus alter MS/Fe. The reductimorphic processes in floodplain sediments may be revealed by "erratic" variations or a permanent increase of the Fe/Ti ratio. The advantage of using geochemical normalization of MS is that chemical analyses are currently nearly routinely performed in geochemical and pollution mapping studies and thus Fe concentrations are thus available for data processing. The combination of the mentioned handy proxies (MS and element composition) would definitely deserve broader use in environmental geology and monitoring.

Fe-C-S systematics in Bengal Fan sediments

NASA Astrophysics Data System (ADS)

Volvoikar, S. P.; Mazumdar, A.; Goswami, H.; Pujari, S.; Peketi, A.

2017-12-01

Global biogeochemical cycles of iron, carbon and sulfur (Fe-C-S) are interrelated. Sulfate reduction in marine sediments is the major factor controlling the cycling and burial of carbon, sulfur and iron. Organoclastic sulfate reduction and anaerobic oxidation of methane (AOM) are the two main processes responsible for sulfate reduction in marine sediments. The amount and reactivity of organic matter, iron minerals and concentrations of dissolved sulfide in pore water control the burial of iron sulfide and organic bound sulfur in marine sediments. Here we investigate the sulfidization process in a sediment core from the western part of upper Bay of Bengal fan characterized by efficient burial of organic matter with siliclastic load. A 30 m long sediment core (MD 161/29, Lat. 170 18.04' N, Long. 870 22.56' E, water depth: 2434m) was collected onboard Marion Dufresne (May, 2007) and studied for Fe-S speciation and organic matter characterization. Buffered dithionite extractable iron (FeD) varies from 0.71 to 1.43 wt % (Avg. 0.79 wt %). FeD represents Fe oxides and oxyhydroxides mainly, ferrihydrite, lepidocrocite, goethite and hematite. Acid volatile sulfur (AVS) varies from 0.0015 to 0.63 wt % (avg: 0.058 wt %), while chromium reducible sulfur (CRS) varies from 0.00047 to 0.29 wt % (avg. 0.054 wt %). Based on the vertical distribution patterns of FeD, AVS and CRS, the core is divided into three zones, the lower (3000 to 1833 cm), middle (1833 to 398 cm) and upper (398 cm to surface) zones. FeD shows higher concentration in the lower zone. FeTR (FeOx + FeD + FeCRS + FeAVS) also exhibit higher concentration in this zone, suggesting higher availability of reactive iron for iron sulfide precipitation. AVS, elemental sulfur, spikes of CRS and gradual enrichment of δ34SAVS and δ34SCRS with sharp peaks in-between is noted in the lower zone. The gradual enrichment of δ34SAVS and δ34SCRS is the outcome of late diagenetic pyritization with higher availability of sulfide (HS- and H2S) from AOM.

Spatio-temporal Distribution and Chemical Speciation of Iron and Manganese in Sediments from Lake Aha, China

NASA Astrophysics Data System (ADS)

Liu, Feng; Hu, Jiwei; Qin, Fanxin; Jiang, Cuihong; Huang, Xianfei; Deng, Jiajun; Li, Cunxiong

2010-11-01

This paper reports an investigation on pollution and potential risk on elements of iron (Fe) and manganese (Mn) in sediments from Lake Aha, which is a drinking-water source for Guiyang City, the capital of Guizhou Province in southwestern China. In the present research, chemical speciation of Fe and Mn in sediments from the lake was studied based on the sequential extraction procedure developed by Tessier et al.. The results obtained from the study are as follows. The average values of total Fe were 47617 mg/kg and 70325 mg/kg in sediments from the lake in summer and winter respectively, and its speciation consisted mainly of residual and Fe-Mn oxides fractions. The amounts of total Fe and the distribution of its speciation in the sediments should be affected by effluents from a large quantity of deserted coal mines in the lake basin in summer and winter. The average values of total Mn were 7996 mg/kg and 1753 mg/kg in summer and winter respectively, and its speciation is primarily comprised of carbonate and Fe-Mn oxides fractions. The amounts of total Mn and its distribution in different fractions in the sediments were believed to be primarily influenced by effluents from those deserted coal mines in summer and by the condition of redox interface in winter.

Hydrothermal Alteration Promotes Humic Acid Formation in Sediments: A Case Study of the Central Indian Ocean Basin

NASA Astrophysics Data System (ADS)

Sarma, Nittala S.; Kiran, Rayaprolu; Rama Reddy, M.; Iyer, Sridhar D.; Peketi, A.; Borole, D. V.; Krishna, M. S.

2018-01-01

Anomalously high concentrations of humic-rich dissolved organic matter (DOM) in extant submarine hydrothermal vent plumes traveled far from source are increasingly being reported. This DOM, able to mobilize trace metals (e.g., Fe2+) has been hypothesized as originating from organic matter produced by thermogenic bacteria. To eliminate a possible abiogenic origin of this DOM, study is required of well-preserved organic compounds that can be attributed to thermogenic bacteria. The Central Indian Ocean Basin (CIOB) is part of a diffuse plate boundary and an intraplate deformation zone. Coarse fraction (>63 µ) characteristics, mineralogy, magnetic susceptibility, and geochemistry were examined in sediments of a core raised close to a north-south fracture zone near the Equator. Two horizons of distinctly brown-colored sediments were shown as hydrothermally altered from their charred fragments and geochemistry (CaCO3, Corg, Ti/Al, Al/(Al + Fe + Mn), Sr/Ba, Mg/Li, Mn micronodules, Fe/Mn). We examined whether humic substances were preserved in these sediments, and if so whether their carbon isotope distribution would support their hydrothermal origin. Alkali extraction of sediments afforded humic acids (HA) in yields up to 1.2% in the brown sediments. The remaining portions of the core had nil or low concentrations of HA. The carbon of hydrothermal HA is isotopically heavier (average δ13C, ˜ -16.3‰) compared to nonhydrothermal HA (-18.1‰), suggesting that they were probably formed from organic matter that remained after elimination of lighter carbon enriched functional groups during diagenesis. The results provide compelling evidence of HA formation from lipids originating from thermogenic bacteria.

Geochemical control on the reduction of U(VI) to mononuclear U(IV) species in lacustrine sediments

NASA Astrophysics Data System (ADS)

Stetten, L.; Mangeret, A.; Brest, J.; Seder-Colomina, M.; Le Pape, P.; Ikogou, M.; Zeyen, N.; Thouvenot, A.; Julien, A.; Alcalde, G.; Reyss, J. L.; Bombled, B.; Rabouille, C.; Olivi, L.; Proux, O.; Cazala, C.; Morin, G.

2018-02-01

Contaminated systems in which uranium (U) concentrations slightly exceed the geochemical background are of particular interest to identify natural processes governing U trapping and accumulation in Earth's surface environments. For this purpose, we examined the role of early diagenesis on the evolution of U speciation and mobility in sediments from an artificial lake located downstream from a former mining site. Sediment and pore water chemistry together with U and Fe solid state speciation were analyzed in sediment cores sampled down to 50 cm depth at four locations in the lake. These organic-rich sediments (∼12% organic C) exhibited U concentrations in the 40-80 mg kg-1 range. The sediment columns were anoxic 2-3 mm below the sediment-water interface and pore waters pH was circumneutral. Pore water chemistry profiles showed that organic carbon mineralization was associated with Fe and Mn reduction and was correlated with a decrease in dissolved U concentration with depth. Immobilization of U in the sediment was correlated with the reduction of U(VI) to U(IV) at depth, as shown by U LIII-edge XANES spectroscopic analysis. XANES and EXAFS spectroscopy at the Fe K-edge showed the reduction of structural Fe(III) to Fe(II) in phyllosilicate minerals with depth, coincident with U(VI) to U(IV) reduction. Thermodynamic modeling suggests that Fe(II) could act as a major reducing agent for U(VI) during early diagenesis of these sediments, leading to complete U reduction below ∼30 cm depth. Shell-by-shell and Cauchy-Wavelet analysis of U LIII-EXAFS spectra indicates that U(VI) and U(IV) are mainly present as mononuclear species bound to C, P or Si ligands. Chemical extractions confirmed that ∼60-80% of U was present as non-crystalline species, which emphasizes that such species should be considered when evaluating the fate of U in lacustrine environments and the efficiency of sediment remediation strategies.

New Insights into Phosphorus Mobilisation from Sulphur-Rich Sediments: Time-Dependent Effects of Salinisation

PubMed Central

van Diggelen, Josepha M. H.; Lamers, Leon P. M.; van Dijk, Gijs; Schaafsma, Maarten J.; Roelofs, Jan G. M.; Smolders, Alfons J. P.

2014-01-01

Internal phosphorus (P) mobilisation from aquatic sediments is an important process adding to eutrophication problems in wetlands. Salinisation, a fast growing global problem, is thought to affect P behaviour. Although several studies have addressed the effects of salinisation, interactions between salinity changes and nutrient cycling in freshwater systems are not fully understood. To tackle eutrophication, a clear understanding of the interacting effects of sediment characteristics and surface water quality is vital. In the present study, P release from two eutrophic sediments, both characterized by high pore water P and very low pore water iron (Fe2+) concentrations, was studied in a long-term aquarium experiment, using three salinity levels. Sediment P release was expected to be mainly driven by diffusion, due to the eutrophic conditions and low iron availability. Unexpectedly, this only seemed to be the driving mechanism in the short term (0–10 weeks). In the long term (>80 weeks), P mobilisation was absent in most treatments. This can most likely be explained by the oxidation of the sediment-water interface where Fe2+ immobilises P, even though it is commonly assumed that free Fe2+ concentrations need to be higher for this. Therefore, a controlling mechanism is suggested in which the partial oxidation of iron-sulphides in the sediment plays a key role, releasing extra Fe2+ at the sediment-water interface. Although salinisation was shown to lower short-term P mobilisation as a result of increased calcium concentrations, it may increase long-term P mobilisation by the interactions between sulphate reduction and oxygen availability. Our study showed time-dependent responses of sediment P mobilisation in relation to salinity, suggesting that sulphur plays an important role in the release of P from FeSx-rich sediments, its biogeochemical effect depending on the availability of Fe2+ and O2. PMID:25369128

Fate of corrosion products released from stainless steel in marine sediments and seawater. Part 2. Sequim Bay clayey silt

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

Schmidt, R.L.

1982-04-01

This report describes laboratory experiments in which neutron-activated 347 stainless steel specimens were exposed to clayey silt from Sequim Bay, Washington. The properties and trace metal geochemistry of the sediment and the amounts of corrosion products that were released under oxic and reduced conditions and their distribution among different chemical fractions of the sediment are discussed. The distributions of Cr, Mn, Fe, Ni and Cu among different chemical forms in the Sequim Bay sediment show that DTPA removed <10% of extractable Cr, Fe and Mn, approx. 20% of extractable Ni and approx. 30% of extractable Cu. The inorganic fraction (materialmore » soluble in 2.5% acetic acid) accounted for approx. 30% of total extractable Mn and approx. 10% or less of Cr, Fe, Ni and Cu. Major portions of Cr and Cu, and a large amount of Fe were in the organic fraction. Extractable Mn, Fe and Ni were associated with hydrous oxides likely as coatings on the mineral substrate of the sediment. No Co was detectable in any of the extracts. (PSB)« less

Chemical forms and ecological risk of arsenic in the sediment of the Daliao River System in China.

PubMed

Wang, Shiliang; Wang, Ping; Men, Bin; Lin, Chunye; He, Mengchang

2012-04-01

The chemical forms and ecological risk of As were characterized in the sediment of the Daliao River System (DRS), which has been affected by long-term intensive industrial, urban, and agricultural activities. Twenty-seven samples of surface sediment were collected and analyzed for total As content and that of its chemical forms. The results indicated that the average total As content in the sediment was 9.83 mg kg(- 1) but that the levels ranged from 1.57 to 83.09 mg kg(- 1). At the sites near cities, mining sites, and the estuary of the DRS, it is likely that adverse effects on aquatic organisms occur, due to As levels in the sediment that are often higher than the threshold effect level and occasionally higher than the probable effect level. A selectively sequential extraction indicated that the majority of As in the sediment was bound to Fe oxides (62.1%), with moderate proportions of residual As (19.8%), specifically adsorbed As (17.9%), and a low proportion of non-specifically adsorbed As (1.1%). In addition, the content of Fe in the sediment was positively and significantly correlated with the contents of amorphous and crystalline Fe oxide-bound As, confirming the crucial role of Fe oxides in immobilizing high amounts of As in superficial environments. The average molar ratio of As to Fe was 1.18 × 10(- 4) in the surface sediment of the DRS, similar to that of natural Fe oxides, but much lower than that of synthesized Schwertmannite. Therefore, the release of As under reduced and low pH conditions can cause serious problems for water resources and for living organisms.

Sedimentology and geochemistry of surface sediments, outer continental shelf, southern Bering Sea

USGS Publications Warehouse

Gardner, J.V.; Dean, W.E.; Vallier, T.L.

1980-01-01

Present-day sediment dynamics, combined with lowerings of sea level during the Pleistocene, have created a mixture of sediments on the outer continental shelf of the southern Bering Sea that was derived from the Alaskan Mainland, the Aleutian Islands, and the Pribilof ridge. Concentrations of finer-grained, higher-organic sediments in the region of the St. George basin have further modified regional distribution patterns of sediment composition. Q-mode factor analysis of 58 variables related to sediment size and composition - including content of major, minor, and trace elements, heavy and light minerals, and clay minerals - reveals three dominant associations of sediment: 1. (1) The most significant contribution, forming a coarse-grained sediment scattered over most of the shelf consists of felsic sediment derived from the generally quartz-rich rocks of the Alaskan mainland. This sediment contains relatively high concentrations of Si, Ba, Rb, quartz, garnet, epidote, metamorphic rock fragments, potassium feldspar, and illite. 2. (2) The next most important group, superimposed on the felsic group consists of andesitic sediment derived from the Aleutian Islands. This more mafic sediment contains relatively high concentrations of Na, Ca, Ti, Sr, V, Mn, Cu, Fe, Al, Co, Zn, Y, Yb, Ga, volcanic rock fragments, glass, clinopyroxene, smectite, and vermiculite. 3. (3) A local group of basaltic sediment, derived from rocks of the Pribilof Islands, is a subgroup of the Aleutian andesite group. Accumulation of fine-grained sediment in St. George basin has created a sediment group containing relatively high concentrations of C, S, U, Li, B, Zr, Ga, Hg, silt, and clay. Sediment of the Aleutian andesite group exhibits a strong gradient, or "plume", with concentrations decreasing away from Unimak Pass and toward St. George basin. The absence of present-day currents sufficient to move even clay-size material as well as the presence of Bering submarine canyon between the Aleutian Islands and the outer continental shelf and slope, indicates that Holocene sediment dynamics cannot be used to explain the observed distribution of surface sediment derived from the Aleutian Islands. We suggest that this pattern is relict and resulted from sediment dynamics during lower sea levels of the Pleistocene. ?? 1980.

Linking Specific Heterotrophic Bacterial Populations to Bioreduction of Uranium and Nitrate in Contaminated Subsurface Sediments by Using Stable Isotope Probing▿†

PubMed Central

Akob, Denise M.; Kerkhof, Lee; Küsel, Kirsten; Watson, David B.; Palumbo, Anthony V.; Kostka, Joel E.

2011-01-01

Shifts in terminal electron-accepting processes during biostimulation of uranium-contaminated sediments were linked to the composition of stimulated microbial populations using DNA-based stable isotope probing. Nitrate reduction preceded U(VI) and Fe(III) reduction in [13C]ethanol-amended microcosms. The predominant, active denitrifying microbial groups were identified as members of the Betaproteobacteria, whereas Actinobacteria dominated under metal-reducing conditions. PMID:21948831

Evidence for Microbial Fe(III) Reduction in Anoxic, Mining-Impacted Lake Sediments (Lake Coeur d'Alene, Idaho)

PubMed Central

Cummings, David E.; March, Anthony W.; Bostick, Benjamin; Spring, Stefan; Caccavo, Frank; Fendorf, Scott; Rosenzweig, R. Frank

2000-01-01

Mining-impacted sediments of Lake Coeur d'Alene, Idaho, contain more than 10% metals on a dry weight basis, approximately 80% of which is iron. Since iron (hydr)oxides adsorb toxic, ore-associated elements, such as arsenic, iron (hydr)oxide reduction may in part control the mobility and bioavailability of these elements. Geochemical and microbiological data were collected to examine the ecological role of dissimilatory Fe(III)-reducing bacteria in this habitat. The concentration of mild-acid-extractable Fe(II) increased with sediment depth up to 50 g kg−1, suggesting that iron reduction has occurred recently. The maximum concentrations of dissolved Fe(II) in interstitial water (41 mg liter−1) occurred 10 to 15 cm beneath the sediment-water interface, suggesting that sulfidogenesis may not be the predominant terminal electron-accepting process in this environment and that dissolved Fe(II) arises from biological reductive dissolution of iron (hydr)oxides. The concentration of sedimentary magnetite (Fe3O4), a common product of bacterial Fe(III) hydroxide reduction, was as much as 15.5 g kg−1. Most-probable-number enrichment cultures revealed that the mean density of Fe(III)-reducing bacteria was 8.3 × 105 cells g (dry weight) of sediment−1. Two new strains of dissimilatory Fe(III)-reducing bacteria were isolated from surface sediments. Collectively, the results of this study support the hypothesis that dissimilatory reduction of iron has been and continues to be an important biogeochemical process in the environment examined. PMID:10618217

Anaerobic degradation of methyl tert-butyl ether (MTBE) and tert-butyl alcohol (TBA).

PubMed

Finneran, K T; Lovley, D R

2001-05-01

The potential for anaerobic degradation of methyl tert-butyl ether (MTBE) and tert-butyl alcohol (TBA) was investigated in laboratory incubations of sediments from a petroleum-contaminated aquifer and in aquatic sediments. The addition of humic substances (HS) stimulated the anaerobic degradation of MTBE in aquifer sediments in which Fe(III) was available as an electron acceptor. This is attributed to the fact that HS and other extracellular quinones can stimulate the activity of Fe(III)-reducing microorganisms by acting as an electron shuttle between Fe(III)-reducing microorganisms and insoluble Fe(III) oxides. MTBE was not degraded in aquifer sediments without Fe(III) and HS. [14C]-MTBE added to aquatic sediments adapted for anaerobic MTBE degradation was converted to 14CO2 in the presence or absence of HS or the HS analog, anthraquione-2,6-disulfonate. Unamended aquatic sediments produced 14CH4 as well as 14CO2 from [14C]-MTBE. The aquatic sediments also rapidly consumed TBA under anaerobic conditions and converted [14C]-TBA to 14CH4 and 14CO2. An adaptation period of ca. 250-300 days was required prior to the most rapid anaerobic MTBE degradation in both sediment types, whereas TBA was metabolized in the aquatic sediments without a lag. These results demonstrate that, under the appropriate conditions, MTBE and TBA can be degraded in the absence of oxygen. This suggests that it may be possible to design strategies for the anaerobic remediation of MTBE in petroleum-contaminated subsurface environments.

Iron oxides in eroded sediments from two representative catchments form South Spain: an example of its environmental implications

NASA Astrophysics Data System (ADS)

Diaz, I.; del Campillo, M. C.; Barrón, V.; Delgado, A.

2012-04-01

Iron (Fe) oxides accounts for one of the most important sorbent compounds in soil and sediments. Nutrients such as P and organic and inorganic pollutants can be retained in soils through its adsorption on these compounds. Particles of Fe oxides can act as a source of sorbed pollutants when these particles are eroded and transported into the bottom of lakes or water as a result of desorption of sorbed compounds or after reduction of Fe oxides under anaerobic conditions. The main target of this work was to study Fe oxides in sediments eroded from two representative catchments from South Spain and how the content and type of oxides in sediments can be affected by the soil properties. One catchment had an extension of 60 ha and soils were mainly classified as Vertisols, with 44-50 % clay in the upper horizon and pH ranging from 7.4 to 7.9. Soils in the other catchment, with an extension of 25 ha, were mainly Alfisols, with 6-33 % clay in the upper horizon and pH between 7.4 and 8.0. Phosphorus and Fe fractions in soil (18 and 10 sampling points in the Vertisol and Alfisols catchment, respectively) and sediments in runoff samples (taken during two consecutive agricultural years, 2000-2002) were studied by means of a sequential fractionation method involving extraction with: NaOH, citrate-bicarbonate (CB), citrate (C), citrate-ascorbate (CA), citrate-bicarbonate-dithionite (CBD), acetate, and HCl. Iron extraction involved sequential extraction with of CB, C, CA and CBD. The two formers step in the Fe fractionation dissolve the poorly crystalline and crystalline Fe oxides, respectively. The concentrations of all the Fe and P fractions were similar in sediments (sum of fractions were 11.5 g Fe/kg and 509 mg P/kg) and soil (sum of fractions were 10.5 g Fe/kg and 586 mg P/kg) from the Vertisol catchment. In this highly calcareous soil, the relevance of Fe oxides in the dynamics of applied P fertilizer was secondary when compared with the precipitation of poorly soluble Ca phosphates, as revealed by the significance of citrate extractable P. In the Alfisols catchment, however, the total free Fe (sum of fractions) was much higher in the sediments (19 g/kg) than in the soil (7.9 g/kg) which explains the increased amounts of P fractions related to oxides (NaOH, CB, CA, and CBD) in sediments (425 mg/kg) when compared with soils (183 mg/kg). Also, the ratio of CA to CBD extractable Fe was higher in sediments (0.22) than in soils (0.15). It can be concluded that in the Alfisol catchment, the content of sorbent surfaces sensitive to reductant conditions are increased in the sediments eroded when compared with soils, and thus, the potential release of pollutants (in this case P) adsorbed or occluded in them. In contrast, in the Vertisol catchment, where P dynamics is dominated by precipitation of Ca phosphates, these forms accounts for the dominant one in soils and sediments, without an increase in the proportion of sorbent surfaces or P forms sensitive to redox conditions.

Early Diagenesis of Trace Elements in Modern Fjord Sediments of the High Arctic

NASA Astrophysics Data System (ADS)

Herbert, L.; Riedinger, N.; Aller, R. C.; Jørgensen, B. B.; Wehrmann, L.

2017-12-01

Marine sediments are critical repositories for elements that are only available at trace concentrations in seawater, such as Fe, Mn, Co, Ni, As, Mo, and U. The behavior of these trace elements in the sediment is governed by a dynamic interplay of diagenetic reactions involving organic carbon, Fe and Mn oxides, and sulfur phases. In the Arctic fjords of Svalbard, glacial meltwater delivers large amounts of reactive Fe and Mn oxides to the sediment, while organic carbon is deposited episodically and diluted by lithogenic material. These conditions result in pronounced Fe and Mn cycling, which in turn drives other diagenetic processes such as rapid sulfide oxidation. These conditions make the Svalbard fjords ideal sites for investigating trace element diagenesis because they allow resolution of the interconnections between Fe and Mn dynamics and trace element cycling. In August 2016, we collected sediment cores from three Svalbard fjords and analyzed trace elements in the pore water and solid sediment over the top meter. Initial results reveal the dynamic nature of these fjords, which are dominated by non-steady state processes and episodic events such as meltwater pulses and phytoplankton blooms. Within this system, the distribution of As appears to be strongly linked to the Fe cycle, while Co and Ni follow Mn; thus, these three elements may be released from the sediment through diffusion and bioturbation along with Fe and Mn. The pore water profiles of U and Mo indicate removal processes that are independent from Fe or Mn, and which are rather unexpected given the apparent diagenetic conditions. Our results will help elucidate the processes controlling trace element cycling in a dynamic, glacially impacted environment and will ultimately contribute to our understanding of the role of fjords in the biogeochemical cycling of trace elements in a rapidly changing Arctic Ocean.

The role of alluvial aquifer sediments in attenuating a dissolved arsenic plume

USGS Publications Warehouse

Ziegler, Brady A.; Schreiber, Madeline E.; Cozzarelli, Isabelle M.

2017-01-01

In a crude-oil-contaminated sandy aquifer at the Bemidji site in northern Minnesota, biodegradation of petroleum hydrocarbons has resulted in release of naturally occurring As to groundwater under Fe-reducing conditions. This study used chemical extractions of aquifer sediments collected in 1993 and 2011–2014 to evaluate the relationship between Fe and As in different redox zones (oxic, methanogenic, Fe-reducing, anoxic-suboxic transition) of the contaminated aquifer over a twenty-year period. Results show that 1) the aquifer has the capacity to naturally attenuate the plume of dissolved As, primarily through sorption; 2) Fe and As are linearly correlated in sediment across all redox zones, and a regression analysis between Fe and As reasonably predicted As concentrations in sediment from 1993 using only Fe concentrations; 3) an As-rich “iron curtain,” associated with the anoxic-suboxic transition zone, migrated 30 m downgradient between 1993 and 2013 as a result of the hydrocarbon plume evolution; and 4) silt lenses in the aquifer preferentially sequester dissolved As, though As is remobilized into groundwater from sediment after reducing conditions are established. Using results of this study coupled with historical data, we develop a conceptual model which summarizes the natural attenuation of As and Fe over time and space that can be applied to other sites that experience As mobilization due to an influx of bioavailable organic matter.

The role of alluvial aquifer sediments in attenuating a dissolved arsenic plume.

PubMed

Ziegler, Brady A; Schreiber, Madeline E; Cozzarelli, Isabelle M

2017-09-01

In a crude-oil-contaminated sandy aquifer at the Bemidji site in northern Minnesota, biodegradation of petroleum hydrocarbons has resulted in release of naturally occurring As to groundwater under Fe-reducing conditions. This study used chemical extractions of aquifer sediments collected in 1993 and 2011-2014 to evaluate the relationship between Fe and As in different redox zones (oxic, methanogenic, Fe-reducing, anoxic-suboxic transition) of the contaminated aquifer over a twenty-year period. Results show that 1) the aquifer has the capacity to naturally attenuate the plume of dissolved As, primarily through sorption; 2) Fe and As are linearly correlated in sediment across all redox zones, and a regression analysis between Fe and As reasonably predicted As concentrations in sediment from 1993 using only Fe concentrations; 3) an As-rich "iron curtain," associated with the anoxic-suboxic transition zone, migrated 30m downgradient between 1993 and 2013 as a result of the hydrocarbon plume evolution; and 4) silt lenses in the aquifer preferentially sequester dissolved As, though As is remobilized into groundwater from sediment after reducing conditions are established. Using results of this study coupled with historical data, we develop a conceptual model which summarizes the natural attenuation of As and Fe over time and space that can be applied to other sites that experience As mobilization due to an influx of bioavailable organic matter. Copyright © 2017 Elsevier B.V. All rights reserved.

Microbial reduction of Fe(III) in acidic sediments: isolation of Acidiphilium cryptum JF-5 capable of coupling the reduction of Fe(III) to the oxidation of glucose.

PubMed

Küsel, K; Dorsch, T; Acker, G; Stackebrandt, E

1999-08-01

To evaluate the microbial populations involved in the reduction of Fe(III) in an acidic, iron-rich sediment, the anaerobic flow of supplemental carbon and reductant was evaluated in sediment microcosms at the in situ temperature of 12 degrees C. Supplemental glucose and cellobiose stimulated the formation of Fe(II); 42 and 21% of the reducing equivalents that were theoretically obtained from glucose and cellobiose, respectively, were recovered in Fe(II). Likewise, supplemental H(2) was consumed by acidic sediments and yielded additional amounts of Fe(II) in a ratio of approximately 1:2. In contrast, supplemental lactate did not stimulate the formation of Fe(II). Supplemental acetate was not consumed and inhibited the formation of Fe(II). Most-probable-number estimates demonstrated that glucose-utilizing acidophilic Fe(III)-reducing bacteria approximated to 1% of the total direct counts of 4', 6-diamidino-2-phenylindole-stained bacteria. From the highest growth-positive dilution of the most-probable-number series at pH 2. 3 supplemented with glucose, an isolate, JF-5, that could dissimilate Fe(III) was obtained. JF-5 was an acidophilic, gram-negative, facultative anaerobe that completely oxidized the following substrates via the dissimilation of Fe(III): glucose, fructose, xylose, ethanol, glycerol, malate, glutamate, fumarate, citrate, succinate, and H(2). Growth and the reduction of Fe(III) did not occur in the presence of acetate. Cells of JF-5 grown under Fe(III)-reducing conditions formed blebs, i.e., protrusions that were still in contact with the cytoplasmic membrane. Analysis of the 16S rRNA gene sequence of JF-5 demonstrated that it was closely related to an Australian isolate of Acidiphilium cryptum (99.6% sequence similarity), an organism not previously shown to couple the complete oxidation of sugars to the reduction of Fe(III). These collective results indicate that the in situ reduction of Fe(III) in acidic sediments can be mediated by heterotrophic Acidiphilium species that are capable of coupling the reduction of Fe(III) to the complete oxidation of a large variety of substrates including glucose and H(2).

Authigenesis of trace metals in energetic tropical shelf environments

USGS Publications Warehouse

Breckel, E.J.; Emerson, S.; Balistrieri, L.S.

2005-01-01

We evaluated authigenic changes of Fe, Mn, V, U, Mo, Cd and Re in suboxic, periodically remobilized, tropical shelf sediments from the Amazon continental shelf and the Gulf of Papua. The Cd/Al, Mo/Al, and U/Al ratios in Amazon shelf sediments were 82%, 37%, and 16% less than those in Amazon River suspended sediments, respectively. Very large depletions of U previously reported in this environment were not observed. The Cd/Al ratios in Gulf of Papua sediments were 76% lower than measurements made on several Papua New Guinea rivers, whereas U/Al ratios in the shelf sediments were enriched by approximately 20%. Other metal/Al ratios in the Papua New Guinea river suspended sediments and continental shelf sediments were not distinguishably different. Comparison of metal/Al ratios to grain size distributions in Gulf of Papua samples indicates that our observations cannot be attributed to differences in grain size between the river suspended sediments and continental shelf sediments. These two shelves constitute a source of dissolved Cd to the world ocean equal to 29-100% of the dissolved Cd input from rivers, but only 3% of the dissolved Mo input and 4% of the dissolved U input. Release of Cd, Mo, and U in tropical shelf sediments is likely a result of intense Fe and Mn oxide reduction in pore waters and resuspension of the sediments. Since we do not observe depletions of particulate Fe and Mn in the shelf sediments most of these dissolved metals must reoxidize in the overlying waters and reprecipitate. As Cd exhibits the largest losses on these tropical shelves, we examined the ability of newly formed Fe and Mn oxides to adsorb dissolved Cd using a geochemical diffuse double-layer surface complexation model and found the oxide surfaces are relatively ineffective at readsorbing Cd in seawater due to surface-site competition by Mg and Ca. If the remobilization and reoxidation of Fe and Mn occurs frequently enough before sediment is buried significant amounts of Cd may be removed from the oxide surfaces. Because a much greater percentage of Mn than Fe becomes remobilized in these shelf sediments, metals closely associated with Mn oxides (like Cd) are more likely to show losses during deposition. ?? 2005 Elsevier Ltd. All rights reserved.

Physical and chemical characteristics including total and geochemical forms of phosphorus in sediment from the top 30 centimeters of cores collected in October 2006 at 26 sites in Upper Klamath Lake, Oregon

USGS Publications Warehouse

Simon, Nancy S.; Ingle, Sarah N.

2011-01-01

μThis study of phosphorus (P) cycling in eutrophic Upper Klamath Lake (UKL), Oregon, was conducted by the U.S. Geological Survey in cooperation with the U.S. Bureau of Reclamation. Lakebed sediments from the upper 30 centimeters (cm) of cores collected from 26 sites were characterized. Cores were sampled at 0.5, 1.5, 2.5, 3.5, 4.5, 10, 15, 20, 25, and 30 cm. Prior to freezing, water content and sediment pH were determined. After being freeze-dried, all samples were separated into greater than 63-micron (μm) particle-size (coarse) and less than 63-μm particle-size (fine) fractions. In the surface samples (0.5 to 4.5 cm below the sediment water interface), approximately three-fourths of the particles were larger than 63-μm. The ratios of the coarse particle-size fraction (>63 μm) and the fine particle-size fraction (<63 μm) were approximately equal in samples at depths greater than 10 cm below the sediment water interface. Chemical analyses included both size fractions of freeze-dried samples. Chemical analyses included determination of total concentrations of aluminum (Al), calcium (Ca), carbon (C), iron (Fe), poorly crystalline Fe, nitrogen (N), P, and titanium (Ti). Total Fe concentrations were the largest in sediment from the northern portion of UKL, Howard Bay, and the southern portion of the lake. Concentrations of total Al, Ca, and Ti were largest in sediment from the northern, central, and southernmost portions of the lake and in sediment from Howard Bay. Concentrations of total C and N were largest in sediment from the embayments and in sediment from the northern arm and southern portion of the lake in the general region of Buck Island. Concentrations of total C were larger in the greater than 63-μm particle-size fraction than in the less than 63-μm particle-size fraction. Sediments were sequentially extracted to determine concentrations of inorganic forms of P, including loosely sorbed P, P associated with poorly crystalline Fe oxides, and P associated with mineral phases. The difference between the concentration of total P and sum of the concentrations of inorganic forms of P is referred to as residual P. Residual P was the largest fraction of P in all of the sediment samples. In UKL, the correlation between concentrations of total P and total Fe in sediment is poor (R2<0.1). The correlation between the concentrations of total P and P associated with poorly crystalline Fe oxides is good (R2=0.43) in surface sediment (0.5-4.5 cm below the sediment water interface) but poor (R2<0.1) in sediments at depths between 10 cm and 30 cm. Phosphorus associated with poorly crystalline Fe oxides is considered bioavailable because it is released when sediment conditions change from oxidizing to reducing, which causes dissolution of Fe oxides.

Coastal eutrophication thresholds: a matter of sediment microbial processes.

PubMed

Lehtoranta, Jouni; Ekholm, Petri; Pitkänen, Heikki

2009-09-01

In marine sediments, the major anaerobic mineralization processes are Fe(III) oxide reduction and sulfate reduction. In this article, we propose that the two alternative microbial mineralization pathways in sediments exert decisively different impacts on aquatic ecosystems. In systems where iron reduction dominates in the recently deposited sediment layers, the fraction of Fe(III) oxides that is dissolved to Fe(II) upon reduction will ultimately be transported to the oxic layer, where it will be reoxidized. Phosphorus, which is released from Fe(III) oxides and decomposing organic matter from the sediment, will be largely trapped by this newly formed Fe(III) oxide layer. Consequently, there are low concentrations of phosphorus in near-bottom and productive water layers and primary production tends to be limited by phosphorus (State 1). By contrast, in systems where sulfate reduction dominates, Fe(III) oxides are reduced by sulfides. This chemical reduction leads to the formation and permanent burial of iron as solid iron sulfides that are unable to capture phosphorus. In addition, the cycling of iron is blocked, and phosphorus is released to overlying water. Owing to the enrichment of phosphorus in water, the nitrogen : phosphorus ratio is lowered and nitrogen tends to limit algal growth, giving an advantage to nitrogen-fixing blue-green algae (State 2). A major factor causing a shift from State 1 to State 2 is an increase in the flux of labile organic carbon to the bottom sediments; upon accelerating eutrophication a critical point will be reached when the availability of Fe(III) oxides in sediments will be exhausted and sulfate reduction will become dominant. Because the reserves of Fe(III) oxides are replenished only slowly, reversal to State 1 may markedly exceed the time needed to reduce the flux of organic carbon to the sediment. A key factor affecting the sensitivity of a coastal system to such a regime shift is formed by the hydrodynamic alterations that decrease the transport of O2 to the near-bottom water, e.g., due to variations in salinity and temperature stratification.

Estimating production and consumption of solid reactive Fe phases in marine sediments from concentration profiles

EPA Science Inventory

1D diffusion models may be used to estimate rates of production and consumption of dissolved metabolites in marine sediments, but are applied less often to the solid phase. Here we used a numerical inverse method to estimate solid phase Fe(III) and Fe(II) consumption and product...

Reductive reactivity of iron(III) oxides in the east china sea sediments: characterization by selective extraction and kinetic dissolution.

PubMed

Chen, Liang-Jin; Zhu, Mao-Xu; Yang, Gui-Peng; Huang, Xiang-Li

2013-01-01

Reactive Fe(III) oxides in gravity-core sediments collected from the East China Sea inner shelf were quantified by using three selective extractions (acidic hydroxylamine, acidic oxalate, bicarbonate-citrate buffered sodium dithionite). Also the reactivity of Fe(III) oxides in the sediments was characterized by kinetic dissolution using ascorbic acid as reductant at pH 3.0 and 7.5 in combination with the reactive continuum model. Three parameters derived from the kinetic method: m 0 (theoretical initial amount of ascorbate-reducible Fe(III) oxides), k' (rate constant) and γ (heterogeneity of reactivity), enable a quantitative characterization of Fe(III) oxide reactivity in a standardized way. Amorphous Fe(III) oxides quantified by acidic hydroxylamine extraction were quickly consumed in the uppermost layer during early diagenesis but were not depleted over the upper 100 cm depth. The total amounts of amorphous and poorly crystalline Fe(III) oxides are highly available for efficient buffering of dissolved sulfide. As indicated by the m 0, k' and γ, the surface sediments always have the maximum content, reactivity and heterogeneity of reactive Fe(III) oxides, while the three parameters simultaneously downcore decrease, much more quickly in the upper layer than at depth. Albeit being within a small range (within one order of magnitude) of the initial rates among sediments at different depths, incongruent dissolution could result in huge discrepancies of the later dissolution rates due to differentiating heterogeneity, which cannot be revealed by selective extraction. A strong linear correlation of the m 0 at pH 3.0 with the dithionite-extractable Fe(III) suggests that the m 0 may represent Fe(III) oxide assemblages spanning amorphous and crystalline Fe(III) oxides. Maximum microbially available Fe(III) predicted by the m 0 at pH 7.5 may include both amorphous and a fraction of other less reactive Fe(III) phases.

Reductive Reactivity of Iron(III) Oxides in the East China Sea Sediments: Characterization by Selective Extraction and Kinetic Dissolution

PubMed Central

Chen, Liang-Jin; Zhu, Mao-Xu; Yang, Gui-Peng; Huang, Xiang-Li

2013-01-01

Reactive Fe(III) oxides in gravity-core sediments collected from the East China Sea inner shelf were quantified by using three selective extractions (acidic hydroxylamine, acidic oxalate, bicarbonate-citrate buffered sodium dithionite). Also the reactivity of Fe(III) oxides in the sediments was characterized by kinetic dissolution using ascorbic acid as reductant at pH 3.0 and 7.5 in combination with the reactive continuum model. Three parameters derived from the kinetic method: m 0 (theoretical initial amount of ascorbate-reducible Fe(III) oxides), k′ (rate constant) and γ (heterogeneity of reactivity), enable a quantitative characterization of Fe(III) oxide reactivity in a standardized way. Amorphous Fe(III) oxides quantified by acidic hydroxylamine extraction were quickly consumed in the uppermost layer during early diagenesis but were not depleted over the upper 100 cm depth. The total amounts of amorphous and poorly crystalline Fe(III) oxides are highly available for efficient buffering of dissolved sulfide. As indicated by the m 0, k′ and γ, the surface sediments always have the maximum content, reactivity and heterogeneity of reactive Fe(III) oxides, while the three parameters simultaneously downcore decrease, much more quickly in the upper layer than at depth. Albeit being within a small range (within one order of magnitude) of the initial rates among sediments at different depths, incongruent dissolution could result in huge discrepancies of the later dissolution rates due to differentiating heterogeneity, which cannot be revealed by selective extraction. A strong linear correlation of the m 0 at pH 3.0 with the dithionite-extractable Fe(III) suggests that the m 0 may represent Fe(III) oxide assemblages spanning amorphous and crystalline Fe(III) oxides. Maximum microbially available Fe(III) predicted by the m 0 at pH 7.5 may include both amorphous and a fraction of other less reactive Fe(III) phases. PMID:24260377

Validation of a continuous flow method for the determination of soluble iron in atmospheric dust and volcanic ash.

PubMed

Simonella, Lucio E; Gaiero, Diego M; Palomeque, Miriam E

2014-10-01

Iron is an essential micronutrient for phytoplankton growth and is supplied to the remote areas of the ocean mainly through atmospheric dust/ash. The amount of soluble Fe in dust/ash is a major source of uncertainty in modeling-Fe dissolution and deposition to the surface ocean. Currently in the literature, there exist almost as many different methods to estimate fractional solubility as researchers in the field, making it difficult to compare results between research groups. Also, an important constraint to evaluate Fe solubility in atmospheric dust is the limited mass of sample which is usually only available in micrograms to milligrams amounts. A continuous flow (CF) method that can be run with low mass of sediments (<10mg) was tested against a standard method which require about 1g of sediments (BCR of the European Union). For validation of the CF experiment, we run both methods using South American surface sediment and deposited volcanic ash. Both materials tested are easy eroded by wind and are representative of atmospheric dust/ash exported from this region. The uncertainty of the CF method was obtained from seven replicates of one surface sediment sample, and shows very good reproducibility. The replication was conducted on different days in a span of two years and ranged between 8 and 22% (i.e., the uncertainty for the standard method was 6-19%). Compared to other standardized methods, the CF method allows studies of dissolution kinetic of metals and consumes less reagents and time (<3h). The method validated here is suggested to be used as a standardized method for Fe solubility studies on dust/ash. Copyright © 2014 Elsevier B.V. All rights reserved.

Oxidative dissolution potential of biogenic and abiogenic TcO 2 in subsurface sediments

NASA Astrophysics Data System (ADS)

Fredrickson, James K.; Zachara, John M.; Plymale, Andrew E.; Heald, Steve M.; McKinley, James P.; Kennedy, David W.; Liu, Chongxuan; Nachimuthu, Ponnusamy

2009-04-01

Technetium-99 (Tc) is an important fission product contaminant associated with sites of nuclear fuels reprocessing and geologic nuclear waste disposal. Tc is highly mobile in its most oxidized state [Tc(VII)O4-] and less mobile in the reduced form [Tc(IV)O 2· nH 2O]. Here we investigate the potential for oxidation of Tc(IV) that was heterogeneously reduced by reaction with biogenic Fe(II) in two sediments differing in mineralogy and aggregation state; unconsolidated Pliocene-age fluvial sediment from the upper Ringold (RG) Formation at the Hanford Site and a clay-rich saprolite from the Field Research Center (FRC) background site on the Oak Ridge Site. Both sediments contained Fe(III) and Mn(III/IV) as redox active phases, but FRC also contained mass-dominant Fe-phyllosilicates of different types. Shewanella putrefaciens CN32 reduced Mn(III/IV) oxides and generated Fe(II) that was reactive with Tc(VII) in heat-killed, bioreduced sediment. After bioreduction and heat-killing, biogenic Fe(II) in the FRC exceeded that in RG by a factor of two. More rapid reduction rates were observed in the RG that had lower biogenic Fe(II), and less particle aggregation. EXAFS measurements indicated that the primary reduction product was a TcO 2-like phase in both sediments. The biogenic redox product Tc(IV) oxidized rapidly and completely in RG when contacted with air. Oxidation, in contrast, was slow and incomplete in the FRC, in spite of similar molecular scale speciation of Tc compared to RG. X-ray microprobe, electron microprobe, X-ray absorption spectroscopy, and micro X-ray diffraction were applied to the whole sediment and isolated Tc-containing particles. These analyses revealed that non-oxidizable Tc(IV) in the FRC existed as complexes with octahedral Fe(III) within intra-grain domains of 50-100 μm-sized, Fe-containing micas presumptively identified as celadonite. The markedly slower oxidation rates in FRC as compared to RG were attributed to mass-transfer-limited migration of O 2 into intra-aggregate and intraparticle domains where Tc(IV) existed; and the formation of unique, oxidation-resistant, intragrain Tc(IV)-Fe(III) molecular species.

Fe(II)- and sulfide-facilitated reduction of 99Tc(VII)O4- in microbially reduced hyporheic zone sediments

NASA Astrophysics Data System (ADS)

Lee, Ji-Hoon; Zachara, John M.; Fredrickson, James K.; Heald, Steve M.; McKinley, James P.; Plymale, Andrew E.; Resch, Charles T.; Moore, Dean A.

2014-07-01

Redox-reactive, biogeochemical phases generated by reductive microbial activity in hyporheic zone sediments from a dynamic groundwater-river interaction zone were evaluated for their ability to reduce soluble pertechnetate [99Tc(VII)O4-] to less soluble Tc(IV). The sediments were bioreduced by indigenous microorganisms that were stimulated by organic substrate addition in synthetic groundwater with or without sulfate. In most treatments, 20 μmol L-1 initial aqueous Tc(VII) was reduced to near or below detection (3.82 × 10-9 mol L-1) over periods of days to months in suspensions of variable solids concentrations. Native sediments containing significant lithogenic Fe(II) in various phases were, in contrast, unreactive with Tc(VII). The reduction rates in the bioreduced sediments increased with increases in sediment mass, in proportion to weak acid-extractable Fe(II) and sediment-associated sulfide (AVS). The rate of Tc(VII) reduction was first order with respect to both aqueous Tc(VII) concentration and sediment mass, but correlations between specific reductant concentrations and reaction rate were not found. X-ray microprobe measurements revealed a strong correlation between Tc hot spots and Fe-containing mineral particles in the sediment. However, only a portion of Fe-containing particles were Tc-hosts. The Tc-hot spots displayed a chemical signature (by EDXRF) similar to pyroxene. The application of autoradiography and electron microprobe allowed further isolation of Tc-containing particles that were invariably found to be ca 100 μm aggregates of primary mineral material embedded within a fine-grained phyllosilicate matrix. EXAFS spectroscopy revealed that the Tc(IV) within these were a combination of a Tc(IV)O2-like phase and Tc(IV)-Fe surface clusters, with a significant fraction of a TcSx-like phase in sediments incubated with SO42-. AVS was implicated as a more selective reductant at low solids concentration even though its concentration was below that required for stoichiometric reduction of Tc(VII). These results demonstrate that composite mineral aggregates may be redox reaction centers in coarse-textured hyporheic zone sediments regardless of the dominant anoxic biogeochemical processes.

Fe(II)- and Sulfide-Facilitated Reduction of 99Tc(VII)O4- in Microbially Reduced Hyporheic Zone Sediments

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

Lee, Ji-Hoon; Zachara, John M.; Fredrickson, Jim K.

Redox-reactive, biogeochemical phases generated by reductive microbial activity in hyporheic zone sediments from a dynamic groundwater-river interaction zone were evaluated for their ability to reduce soluble pertechnetate [99Tc(VII)O4-] to less soluble Tc(IV). The sediments were bioreduced by indigenous microorganisms that were stimulated by organic substrate addition in synthetic groundwater with or without sulfate. In most treatments, 20 µmol L-1 initial aqueous Tc(VII) was reduced to near or below detection (3.82×10-9 mol L-1) over periods of days to months in suspensions of variable solids concentrations. Native sediments containing significant lithogenic Fe(II) in various phases were, in contrast, unreactive with Tc(VII). Themore » reduction rates in the bioreduced sediments increased with increases in sediment mass, in proportion to weak acid-extractable Fe(II) and sediment-associated sulfide (AVS). The rate of Tc(VII) reduction was first order with respect to both aqueous Tc(VII) concentration and sediment mass, but correlations between specific reductant concentrations and reaction rate were not found. X-ray microprobe measurements revealed a strong correlation between Tc hot spots and Fe-containing mineral particles in the sediment. However, only a portion of Fe-containing particles were Tc-hosts. The Tc-hot spots displayed a chemical signature (by EDXRF) similar to pyroxene. The application of autoradiography and electron microprobe allowed further isolation of Tc-containing particles that were invariably found to be ca 100 µm aggregates of primary mineral material embedded within a fine-grained phyllosilicate matrix. EXAFS spectroscopy revealed that the Tc(IV) within these were a combination of a Tc(IV)O2-like phase and Tc(IV)-Fe surface clusters, with a significant fraction of a TcSx-like phase in sediments incubated with SO42-. AVS was implicated as a more selective reductant at low solids concentration even though its concentration was below that required for stoichiometric reduction of Tc(VII). These results demonstrate that composite mineral aggregates may be redox reaction centers in coarse-textured hyporheic zone sediments regardless of the dominant anoxic biogeochemical processes.« less

A baseline record of trace elements concentration along the beach placer mining areas of Kanyakumari coast, South India.

PubMed

Simon Peter, T; Chandrasekar, N; John Wilson, J S; Selvakumar, S; Krishnakumar, S; Magesh, N S

2017-06-15

Trace element concentration in the beach placer mining areas of Kanyakumari coast, South India was assessed. Sewage and contaminated sediments from mining sites has contaminated the surface sediments. Enrichment factor indicates moderately severe enrichment for Pb, minor enrichment for Mn, Zn, Ni, Fe and no enrichment for Cr and Cu. The Igeo values show higher concentration of Pb ranging in the scale of 3-4, which shows strong contamination due to high anthropogenic activity such as mining and terrestrial influences into the coastal regions. Correlation coefficient shows that most of the elements are associated with each other except Ni and Pb. Factor analysis reveals that Mn, Zn, Fe, Cr, Pb and Cu are having a significant loading and it indicates that these elements are mainly derived from similar origin. The cluster analysis clearly indicated that the mining areas are grouped under cluster 2 and non-mining areas are clustered under group 1. Copyright © 2017 Elsevier Ltd. All rights reserved.

Sediment pollution characteristics and in situ control in a deep drinking water reservoir.

PubMed

Zhou, Zizhen; Huang, Tinglin; Li, Yang; Ma, Weixing; Zhou, Shilei; Long, Shenghai

2017-02-01

Sediment pollution characteristics, in situ sediment release potential, and in situ inhibition of sediment release were investigated in a drinking water reservoir. Results showed that organic carbon (OC), total nitrogen (TN), and total phosphorus (TP) in sediments increased from the reservoir mouth to the main reservoir. Fraction analysis indicated that nitrogen in ion exchangeable form and NaOH-extractable P (Fe/Al-P) accounted for 43% and 26% of TN and TP in sediments of the main reservoir. The Risk Assessment Code for metal elements showed that Fe and Mn posed high to very high risk. The results of the in situ reactor experiment in the main reservoir showed the same trends as those observed in the natural state of the reservoir in 2011 and 2012; the maximum concentrations of total OC, TN, TP, Fe, and Mn reached 4.42mg/L, 3.33mg/L, 0.22mg/L, 2.56mg/L, and 0.61mg/L, respectively. An in situ sediment release inhibition technology, the water-lifting aerator, was utilized in the reservoir. The results of operating the water-lifting aerator indicated that sediment release was successfully inhibited and that OC, TN, TP, Fe, and Mn in surface sediment could be reduced by 13.25%, 15.23%, 14.10%, 5.32%, and 3.94%, respectively. Copyright © 2016. Published by Elsevier B.V.

Nitrogenase of Klebsiella pneumoniae. Interaction of the component proteins studied by ultracentrifugation

PubMed Central

Eady, Robert R.

1973-01-01

Sedimentation-velocity analyses of mixtures of the component proteins of nitrogenase of Klebsiella pneumoniae at a 1:1 molar ratio, showed a single peak of sedimentation coefficient (12.4S) considerably greater than that obtained for the larger (Fe+Mo-containing) protein centrifuged alone (10.4S). When the ratio exceeded 1:1 (the smaller Fe-containing protein in excess) an additional peak corresponding in sedimentation coefficient (about 4.5S) to free Fe-containing protein appeared. When proteins, which had been inactivated by exposure to air were used, no interaction occurred. Na2S2O4 at 2mm both reversed and prevented interaction between the two proteins; sedimentation coefficients corresponded to those of the proteins when centrifuged alone. These results demonstrate the formation of a complex between the nitrogenase proteins, and, together with data of activity titration curves, are consistent with the formulation of the nitrogenase complex of K. pneumoniae as (Fe-containing protein)–(Fe+Mo-containing protein). ImagesFig. 1. PMID:4589392

Evaluation of elemental enrichments in surface sediments off southwestern Taiwan

NASA Astrophysics Data System (ADS)

Chen, Chen-Tung; Kandasamy, Selvaraj

2008-05-01

Surface slices of 20 sediment cores, off southwestern Taiwan, and bed sediment of River Kaoping were measured for major and trace elements (Al, As, Ca, Cd, Cl, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb, S, Si, Ti, V, and Zn) to evaluate the geochemical processes responsible for their distribution, including elemental contamination. Major element/Al ratio and mean grain size indicate quartz-dominated, coarse grained sediments that likely derived from sedimentary rocks of Taiwan and upper crust of Yangtze Craton. Bi-plot of SiO2 versus Fe2O{3/T} suggests the possible iron enrichment in sediments of slag dumping sites. Highest concentrations of Cr, Mn, P, S, and Zn found in sediments of dumping sites support this. Correlation analysis shows dual associations, detrital and organic carbon, for Cr, P, S, and V with the latter association typical for sediments in dumping sites. Normalization of trace elements to Al indicates high enrichment factors (>2) for As, Cd, Pb, and Zn, revealing contamination. Factor analysis extracted four geochemical associations with the principal factor accounted for 25.1% of the total variance and identifies the combined effects of dumped iron and steel slag-induced C-S-Fe relationship owing to authigenic precipitation of Fe-Mn oxyhydroxides and/or metal sulfides, and organic matter complexation of Fe, Mn, Ca, Cr, P, and V. Factors 2, 3, and 4 reveal detrital association (Ti, Al, Ni, Pb, Cu, and V), effect of sea salt (Cl, Mg, Na, and K) and anthropogenic component (As and Zn)-carbonate link, respectively, in the investigated sediments.

Distribution and Phase Association of Some Major and Trace Elements in the Arabian Gulf Sediments

NASA Astrophysics Data System (ADS)

Basaham, A. S.; El-Sayed, M. A.

1998-02-01

Twenty-four sediment samples were collected from the Arabian Gulf (ROPME Sea) and analysed for their grain size distribution and carbonate contents as well as the major elements Ca, Mg, Fe and Al and macro and trace elements Mn, Sr, Ba, Zn, Cu, Cr, V, Ni and Hg. Concentration of trace elements are found comparable to previous data published for samples taken before and after the Gulf War, and reflect the natural background level. Grain size analyses, aluminium and carbonate measurements support the presence of two major sediment types: (1) a terrigenous, fine-grained and Al rich type predominating along the Iranian side; and (2) a coarse-grained and carbonate rich type predominating along the Arabian side of the Gulf. Investigation of the correlation of the elements analysed with the sediment type indicates that they could be grouped under two distinct associations: (1) carbonate association including Ca and Sr; and (2) terrigenous association comprising Al, Fe, Mg, Ba, Mn, Zn, Cu, Cr, V, Ni and Hg. Element/Al ratios calculated for the mud non-carbonate fraction indicate that the Euphrates and Tigris rivers have minor importance as sediment sources to the Gulf. Most of the elements have exceptionally high aluminium ratios in sediments containing more than 85-90% carbonate. These sediments are restricted to the southern and south-eastern part of the area where depth is shallow and temperature and salinity are high. Both biological accumulation and chemical and biochemical coprecipitation could be responsible for this anomaly.

[Transport and sources of runoff pollution from urban area with combined sewer system].

PubMed

Li, Li-Qing; Yin, Cheng-Qing

2009-02-15

Sampling and monitoring of runoff and sewage water in Wuhan urban area with combined sewer system were carried out during the period from 2003 to 2006, to study the transport and sources of runoff pollution at the catchment scale coupled with environmental geochemistry method. The results showed a change in quality between the runoff entering the sewer network and the combined storm water flow at the sewer's outlet. A significant increase was observed in the concentrations of total suspended solids (TSS), volatile suspended solids (VSS), COD, TN, and TP, and in the proportion of COD linked to particles. During the runoff production and transport, the concentrations of TSS and COD increased from 18.7 mg/L and 37.0 mg/L in roof runoff, to 225.3 mg/L and 176.5 mg/L in street runoff, and to 449.7 mg/L and 359.9 mg/L in combined storm water flow, respectively. The proportion of COD linked to particles was increased by 18%. In addition, the total phosphorus (P) and iron (Fe) contents in urban ground dust, storm drain sediment, sewage sewer sediment and combined sewer sediment were measured to identify the potential sources of suspended solids in the combined flow. The urban ground dust andstorm drain sediment wererich in Fe, whereas the sewage sewer sediment was rich in P. The P/Fe ratios in these groups were significantly distinct and able to differentiate them. A calculation of the two storm events based on the P/Fe rations showed that 56% +/- 26% of suspended solids in combined flow came from urban ground and storm drain. The rest wer e originated from the sewage sewer sediments which deposited in combined sewer on the dry weather days and were eroded on the wet weather days. The combined sewer network not only acts as a transport system, but also constitutes a physicochemical reactor that degrades the quality of urban water. Reducing the in-sewer pollution stocks would effectively control urban runoff pollution.

CATALYTIC DECHLORINATION OF 2-CL BP IN SEDIMENTS AND WATER-SOLVENT SYSTEMS BY FE/PD BIMETAL

EPA Science Inventory

Polychlorinated biphenyls (PCBs) are one group of persistent organic pollutants (POPs) of international concern because of global distribution, persistence, and toxicity. Removal of these compounds from the environment presents a very tough challenge because they are highly hydro...

Dynamic characteristics of sulfur, iron and phosphorus in coastal polluted sediments, north China.

PubMed

Sun, Qiyao; Sheng, Yanqing; Yang, Jian; Di Bonito, Marcello; Mortimer, Robert J G

2016-12-01

The cycling of sulfur (S), iron (Fe) and phosphorus (P) in sediments and pore water can impact the water quality of overlying water. In a heavily polluted river estuary (Yantai, China), vertical profiles of fluxes of dissolved sulfide, Fe 2+ and dissolved reactive phosphorus (DRP) in sediment pore water were investigated by the Diffusive Gradients in Thin films technique (DGT). Vertical fluxes of S, Fe, P in intertidal sediment showed the availability of DRP increased while the sulfide decreased with depth in surface sediment, indicating that sulfide accumulation could enhance P release in anoxic sediment. In sites with contrasting salinity, the relative dominance of iron and sulfate reduction was different, with iron reduction dominant over sulfate reduction in the upper sediment at an intertidal site but the reverse true in a freshwater site, with the other process dominating at depth in each case. Phosphate release was largely controlled by iron reduction. Copyright © 2016 Elsevier Ltd. All rights reserved.

Trace metal concentrations in tropical mangrove sediments, NE Brazil.

PubMed

Miola, Brígida; Morais, Jáder Onofre de; Pinheiro, Lidriana de Souza

2016-01-15

Sediment cores were taken from the mangroves of the Coreaú River estuary off the northeast coast of Brazil. They were analyzed for grain size, CaCO3, organic matter, and trace metal (Cd, Pb, Zn, Cu, Al, and Fe) contents. Mud texture was the predominant texture. Levels of trace metals in surface sediments indicated strong influence of anthropogenic processes, and diagenetic processes controlled the trace metal enrichment of core sediments of this estuary. The positive relationships between trace metals and Al and Fe indicate that Cu, Zn, Pb, and Cd concentrations are associated mainly with Al and Fe oxy-hydroxides and have natural sources. Copyright © 2015 Elsevier Ltd. All rights reserved.

Natural and anthropogenic controls on sediment composition of an arid coastal environment: Sharm Obhur, Red Sea, Saudi Arabia.

PubMed

Ghandour, I M; Basaham, A S; Basaham, S; Al-Washmi, H A; Al-Washmi, A; Masuda, H

2014-03-01

The present study investigated the natural and anthropogenic processes that control the composition of the bottom sediments of Sharm Obhur, Red Sea. Mineralogical analysis using XRD indicated that the sediments consist of carbonate and non-carbonate minerals. Elemental interrelationships allowed differentiating two groups of elements of different sources and origin. Elements that are in the same group are positively correlated, while they correlate negatively with elements of the other group. The first group includes silicon, Al, Fe, Mn, Mg, vanadium (V), chromium (Cr), Co, Ni, Cu, and Zn, whereas the other group includes Ca, Sr, and CaCO3. The highest concentration levels of the first group and the highest content of non-carbonate minerals were obtained from the sediments near the head of the sharm (zone A), whereas the sediments near the mouth of the sharm (zone B) yielded high concentrations of second group and carbonate minerals. Metal enrichment and contamination factors and pollution load index were calculated. The values of these indices differentiate two groups of metals: lithogenic and non-lithogenic. Except for lead (Pb) at one sampling site, metals in zone A sediments are of lithogenic source, supplied to the sharm either naturally by aeolian transportation and through Wadi Al-Kuraa'a during rare but major floods or by human activities such as dumping and shore protection. Non-lithogenic Cr, Pb, V, and Mn were documented from some sampling sites in zone B, and their occurrences are related to waste disposal and fossil fuel combustion.

Alkaline Fe(III) reduction by a novel alkali-tolerant Serratia sp. isolated from surface sediments close to Sellafield nuclear facility, UK.

PubMed

Thorpe, Clare L; Morris, Katherine; Boothman, Christopher; Lloyd, Jonathan R

2012-02-01

Extensive denitrification resulted in a dramatic increase in pH (from 6.8 to 9.5) in nitrate-impacted, acetate-amended sediment microcosms containing sediment representative of the Sellafield nuclear facility, UK. Denitrification was followed by Fe(III) reduction, indicating the presence of alkali-tolerant, metal-reducing bacteria. A close relative (99% 16S rRNA gene sequence homology) to Serratia liquefaciens dominated progressive enrichment cultures containing Fe(III)-citrate as the sole electron acceptor at pH 9 and was isolated aerobically using solid media. The optimum growth conditions for this facultatively anaerobic Serratia species were investigated, and it was capable of metabolizing a wide range of electron acceptors including oxygen, nitrate, FeGel, Fe-NTA and Fe-citrate and electron donors including acetate, lactate, formate, ethanol, glucose, glycerol and yeast extract at an optimum pH of c. 6.5 at 20 °C. The alkali tolerance of this strain extends the pH range of highly adaptable Fe(III)-reducing Serratia species from mildly acidic pH values associated with acid mine drainage conditions to alkali conditions representative of subsurface sediments stimulated for extensive denitrification and metal reduction. © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Temperature and Cyanobacterial Bloom Biomass Influence Phosphorous Cycling in Eutrophic Lake Sediments

PubMed Central

Chen, Mo; Ye, Tian-Ran; Krumholz, Lee R.; Jiang, He-Long

2014-01-01

Cyanobacterial blooms frequently occur in freshwater lakes, subsequently, substantial amounts of decaying cyanobacterial bloom biomass (CBB) settles onto the lake sediments where anaerobic mineralization reactions prevail. Coupled Fe/S cycling processes can influence the mobilization of phosphorus (P) in sediments, with high releases often resulting in eutrophication. To better understand eutrophication in Lake Taihu (PRC), we investigated the effects of CBB and temperature on phosphorus cycling in lake sediments. Results indicated that added CBB not only enhanced sedimentary iron reduction, but also resulted in a change from net sulfur oxidation to sulfate reduction, which jointly resulted in a spike of soluble Fe(II) and the formation of FeS/FeS2. Phosphate release was also enhanced with CBB amendment along with increases in reduced sulfur. Further release of phosphate was associated with increases in incubation temperature. In addition, CBB amendment resulted in a shift in P from the Fe-adsorbed P and the relatively unreactive Residual-P pools to the more reactive Al-adsorbed P, Ca-bound P and organic-P pools. Phosphorus cycling rates increased on addition of CBB and were higher at elevated temperatures, resulting in increased phosphorus release from sediments. These findings suggest that settling of CBB into sediments will likely increase the extent of eutrophication in aquatic environments and these processes will be magnified at higher temperatures. PMID:24682039

Fractionation and risk assessment of Fe and Mn in surface sediments from coastal sites of Sonora, Mexico (Gulf of California).

PubMed

Jara-Marini, Martín E; García-Camarena, Raúl; Gómez-Álvarez, Agustín; García-Rico, Leticia

2015-07-01

The aim of this study was to evaluate Fe and Mn distribution in geochemical fractions of the surface sediment of four oyster culture sites in the Sonora coast, Mexico. A selective fractionation scheme to obtain five fractions was adapted for the microwave system. Surface sediments were analyzed for carbonates, organic matter contents, and Fe and Mn in geochemical fractions. The bulk concentrations of Fe ranged from 10,506 to 21,918 mg/kg (dry weight, dry wt), and the bulk concentrations of Mn ranged from 185.1 to 315.9 mg/kg (dry wt) in sediments, which was low and considered as non-polluted in all of the sites. The fractionation study indicated that the major geochemical phases for the metals were the residual, as well as the Fe and Mn oxide fractions. The concentrations of metals in the geochemical fractions had the following order: residual > Fe and Mn oxides > organic matter > carbonates > interchangeable. Most of the Fe and Mn were linked to the residual fraction. Among non-residual fractions, high percentages of Fe and Mn were linked to Fe and Mn oxides. The enrichment factors (EFs) for the two metals were similar in the four studied coasts, and the levels of Fe and Mn are interpreted as non-enrichment (EF < 1) because the metals concentrations were within the baseline concentrations. According to the environmental risk assessment codes, Fe and Mn posed no risk and low risk, respectively. Although the concentrations of Fe and Mn were linked to the residual fraction, the levels in non-residual fractions may significantly result in the transference of other metals, depending on several physico-chemical and biological factors.

Benthic iron and phosphorus release from river dominated shelf sediments under varying bottom water O2 concentrations.

NASA Astrophysics Data System (ADS)

Ghaisas, N. A.; Maiti, K.; White, J. R.

2017-12-01

Phosphorus (P) cycling in coastal ocean is predominantly controlled by river discharge and biogeochemistry of the sediments. In coastal Louisiana, sediment biogeochemistry is strongly influenced by seasonally fluctuating bottom water O2, which, in turn transitions the shelf sediments from being a sink to source of P. Sediment P-fluxes were 9.73 ± 0.76 mg / m2 /d and 0.67±0.16 mg/m2/d under anaerobic and aerobic conditions respectively, indicating a 14 times higher P-efflux from oxygen deprived sediments. A high sedimentary oxygen consumption rate of 889 ± 33.6 mg/m2/d was due to organic matter re-mineralization and resulted in progressively decreasing the water column dissolved O2 , coincident with a P-flux of 7.2 ± 5.5 mg/m2/d from the sediment. Corresponding water column flux of Fe total was 19.7 ± 7.80 mg/m2/d and the sediment-TP decreased from 545 mg/Kg to 513 mg/Kg. A simultaneous increase in pore water Fe and P concentrations in tandem with a 34.6% loss in sedimentary Fe-bound P underscores the importance of O2 on coupled Fe- P biogeochemistry. This study suggests that from a 14,025 sq. km hypoxia area, Louisiana shelf sediments can supply 1.33x105 kg P/day into the water column compared to 0.094 x 105 kg P/day during the fully aerobic water column conditions.

Redox processes as revealed by voltammetry in the surface sediments of the Gotland Basin, Baltic Sea

NASA Astrophysics Data System (ADS)

Yücel, Mustafa; Dale, Andy; Sommer, Stefan; Pfannkuche, Olaf

2014-05-01

Sulfur cycling in marine sediments undergoes dramatic changes with changing redox conditions of the overlying waters. The upper sediments of the anoxic Gotland Basin, central Baltic Sea represent a dynamic redox environment with extensive mats of sulfide oxidizing bacteria covering the seafloor beneath the chemocline. In order to investigate sulfur redox cycling at the sediment-water interface, sediment cores were sampled over a transect covering 65 - 174 m water depth in August-September 2013. High resolution (0.25 mm minimum) vertical microprofiles of electroactive redox species including dissolved sulfide and iron were obtained with solid state Au-Hg voltammetric microelectrodes. This approach enabled a fine-scale comparison of porewater profiles across the basin. The steepest sulfide gradients (i.e. the highest sulfide consumption) occurred within the upper 10 mm in sediments covered by surficial mats (2.10 to 3.08 mmol m-2 day-1). In sediments under permanently anoxic waters (>140m), voltammetric signals for Fe(II) and aqueous FeS were detected below a subsurface maximum in dissolved sulfide, indicating a Fe flux originating from older, deeper sedimentary layers. Our results point to a unique sulfur cycling in the Gotland basin seafloor where sulfide accumulation is moderated by sulfide oxidation at the sediment surface and by FeS precipitation in deeper sediment layers. These processes may play an important role in minimizing benthic sulfide fluxes to bottom waters around the major basins of the Baltic Sea.

Intense molybdenum accumulation in sediments underneath a nitrogenous water column and implications for the reconstruction of paleo-redox conditions based on molybdenum isotopes

NASA Astrophysics Data System (ADS)

Scholz, Florian; Siebert, Christopher; Dale, Andrew W.; Frank, Martin

2017-09-01

The concentration and isotope composition of molybdenum (Mo) in sediments and sedimentary rocks are widely used proxies for anoxic conditions in the water column of paleo-marine systems. While the mechanisms leading to Mo fixation in modern restricted basins with anoxic and sulfidic (euxinic) conditions are reasonably well constrained, few studies have focused on Mo cycling in the context of open-marine anoxia. Here we present Mo data for water column particulate matter, modern surface sediments and a paleo-record covering the last 140,000 years from the Peruvian continental margin. Mo concentrations in late Holocene and Eemian (penultimate interglacial) shelf sediments off Peru range from ∼70 to 100 μg g-1, an extent of Mo enrichment that is thought to be indicative of (and limited to) euxinic systems. To investigate if this putative anomaly could be related to the occasional occurrence of sulfidic conditions in the water column overlying the Peruvian shelf, we compared trace metal (Mo, vanadium, uranium) enrichments in particulate matter from oxic, nitrate-reducing (nitrogenous) and sulfidic water masses. Coincident enrichments of iron (Fe) (oxyhydr)oxides and Mo in the nitrogenous water column as well as co-variation of dissolved Fe and Mo in the sediment pore water suggest that Mo is delivered to the sediment surface by Fe (oxyhydr)oxides. Most of these precipitate in the anoxic-nitrogenous water column due to oxidation of sediment-derived dissolved Fe with nitrate as a terminal electron acceptor. Upon reductive dissolution in the surface sediment, a fraction of the Fe and Mo is re-precipitated through interaction with pore water sulfide. The Fe- and nitrate-dependent mechanism of Mo accumulation proposed here is supported by the sedimentary Mo isotope composition, which is consistent with Mo adsorption onto Fe (oxyhydr)oxides. Trace metal co-variation patterns as well as Mo and nitrogen isotope systematics suggest that the same mechanism of Mo delivery caused the 'anomalously' high interglacial Mo accumulation rates in the paleo-record. Our findings suggest that Fe- and nitrate-dependent Mo shuttling under nitrogenous conditions needs to be considered a possible reason for sedimentary Mo enrichments during past periods of widespread anoxia in the open ocean.

A gel probe equilibrium sampler for measuring arsenic porewater profiles and sorption gradients in sediments: II. Field application to Haiwee reservoir sediment

USGS Publications Warehouse

Campbell, K.M.; Root, R.; O'Day, P. A.; Hering, J.G.

2008-01-01

Arsenic (As) geochemistry and sorption behavior were measured in As- and iron (Fe)-rich sediments of Haiwee Reservoir by deploying undoped (clear) polyacrylamide gels and hydrous ferric oxide (HFO)-doped gels in a gel probe equilibrium sampler, which is a novel technique for directly measuring the effects of porewater composition on As adsorption to Fe oxides phases in situ. Arsenic is deposited at the sediment surface as As(V) and is reduced to As(III) in the upper layers of the sediment (0-8 cm), but the reduction of As(V) does not cause mobilization into the porewater. Dissolved As and Fe concentrations increased at depth in the sediment column driven by the reductive dissolution of amorphous Fe(III) oxyhydroxides and conversion to a mixed Fe(II, III) green rust-type phase. Adsorption of As and phosphorous (P) onto HFO-doped gels was inhibited at intermediate depths (10-20 cm), possibly due to dissolved organic or inorganic carbon, indicating that dissolved As concentrations were at least partially controlled by porewater composition rather than surface site availability. In sediments that had been recently exposed to air, the region of sorption inhibition was not observed, suggesting that prior exposure to air affected the extent of reductive dissolution, porewater chemistry, and As adsorption behavior. Arsenic adsorption onto the HFO-doped gels increased at depths >20 cm, and the extent of adsorption was most likely controlled by the competitive effects of dissolved phosphate. Sediment As adsorption capacity appeared to be controlled by changes in porewater composition and competitive effects at shallower depths, and by reductive dissolution and availability of sorption sites at greater burial depths. ?? 2008 American Chemical Society.

Element remobilization, "internal P-loading," and sediment-P reactivity researched by DGT (diffusive gradients in thin films) technique.

PubMed

Wu, Zhihao; Wang, Shengrui; He, Mengchang; Zhang, Li; Jiao, Lixin

2015-10-01

Labile P, Fe, and sulfide with the high spatial resolution in sediment porewater of five sites (A-E) of Dianchi Lake (China) were measured at same locations using AgI/Chelex-100, Chelex-100, and ferrihydrite DGT (diffusive gradients in thin films) probes. DGT derived P/Fe/S concentrations in sediment porewater on millimeter or sub-millimeter scale in order to reveal the element remobilization process and the mechanism of "internal P-loading" of sediments in Dianchi Lake. Decomposition of alga biomass in the uppermost sediment layer and the reductive dissolution of Fe-bound P in the anoxic sediment were the two main processes causing P release. A dynamic numerical model-DIFS (DGT-induced flux in sediments) was used to assess sediment-P reactivity (capacity of solid pool and rate of transfer) and P release risk by kinetic parameter-T C (1089∼20,450 s), distribution coefficient-K d (167.09∼502.0 cm(3) g(-1)), resupply parameter-R (from 0.242 to 0.518), and changes of dissolved/sorbed concentration, R and M at the microzone of DGT/porewater/sediment.

Biodegradation of organic matter and anodic microbial communities analysis in sediment microbial fuel cells with/without Fe(III) oxide addition.

PubMed

Xu, Xun; Zhao, Qingliang; Wu, Mingsong; Ding, Jing; Zhang, Weixian

2017-02-01

To enhance the biodegradation of organic matter in sediment microbial fuel cell (SMFC), Fe(III) oxide, as an alternative electron acceptor, was added into the sediment. Results showed that the SMFC with Fe(III) oxide addition obtained higher removal efficiencies for organics than the SMFC without Fe(III) oxide addition and open circuit bioreactor, and produced a maximum power density (P max ) of 87.85mW/m 2 with a corresponding maximum voltage (V max ) of 0.664V. The alteration of UV-254 and specific ultraviolet absorbance (SUVA) also demonstrated the organic matter in sediments can be effectively removed. High-throughput sequencing of anodic microbial communities indicated that bacteria from the genus Geobacter were predominantly detected (21.23%) in the biofilm formed on the anode of SMFCs, while Pseudomonas was the most predominant genus (18.12%) in the presence of Fe(III) oxide. Additionally, compared with the open circuit bioreactor, more electrogenic bacteria attached to the biofilm of anode in SMFCs. Copyright © 2016 Elsevier Ltd. All rights reserved.

Geochemical and microbiological responses to oxidant introduction into reduced subsurface sediment from the Hanford 300 Area, Washington.

PubMed

Percak-Dennett, Elizabeth M; Roden, Eric E

2014-08-19

Pliocene-aged reduced lacustrine sediment from below a subsurface redox transition zone at the 300 Area of the Hanford site (southeastern Washington) was used in a study of the geochemical response to introduction of oxygen or nitrate in the presence or absence of microbial activity. The sediments contained large quantities of reduced Fe in the form of Fe(II)-bearing phyllosilicates, together with smaller quantities of siderite and pyrite. A loss of ca. 50% of 0.5 M HCl-extractable Fe(II) [5-10 mmol Fe(II) L(-1)] and detectable generation of sulfate (ca. 0.2 mM, equivalent to 10% of the reduced inorganic sulfur pool) occurred in sterile aerobic reactors. In contrast, no systematic loss of Fe(II) or production of sulfate was observed in any of the other oxidant-amended sediment suspensions. Detectable Fe(II) accumulation and sulfate consumption occurred in non-sterile oxidant-free reactors. Together, these results indicate the potential for heterotrophic carbon metabolism in the reduced sediments, consistent with the proliferation of known heterotrophic taxa (e.g., Pseudomonadaceae, Burkholderiaceae, and Clostridiaceae) inferred from 16S rRNA gene pyrosequencing. Microbial carbon oxidation by heterotrophic communities is likely to play an important role in maintaining the redox boundary in situ, i.e., by modulating the impact of downward oxidant transport on Fe/S redox speciation. Diffusion-reaction simulations of oxygen and nitrate consumption coupled to solid-phase organic carbon oxidation indicate that heterotrophic consumption of oxidants could maintain the redox boundary at its current position over millennial time scales.

Reactive-transport modeling of iron diagenesis and associated organic carbon remineralization in a Florida (USA) subterranean estuary

USGS Publications Warehouse

Roy, Moutusi; Martin, Jonathan B.; Smith, Christopher G.; Cable, Jaye E.

2011-01-01

Iron oxides are important terminal electron acceptors for organic carbon (OC) remineralization in subterranean estuaries, particularly where oxygen and nitrate concentrations are low. In Indian River Lagoon, Florida, USA, terrestrial Fe-oxides dissolve at the seaward edge of the seepage face and flow upward into overlying marine sediments where they precipitate as Fe-sulfides. The dissolved Fe concentrations vary by over three orders of magnitude, but Fe-oxide dissolution rates are similar across the 25-m wide seepage face, averaging around 0.21 mg/cm2/yr. The constant dissolution rate, but differing concentrations, indicate Fe dissolution is controlled by a combination of increasing lability of dissolved organic carbon (DOC) and slower porewater flow velocities with distance offshore. In contrast, the average rate constants of Fe-sulfide precipitation decrease from 21.9 × 10-8 s-1 to 0.64 × 10-8 s-1 from the shoreline to the seaward edge of the seepage face as more oxygenated surface water circulates through the sediment. The amount of OC remineralized by Fe-oxides varies little across the seepage face, averaging 5.34 × 10-2 mg/cm2/yr. These rates suggest about 3.4 kg of marine DOC was remineralized in a 1-m wide, shore-perpendicular strip of the seepage face as the terrestrial sediments were transgressed over the past 280 years. During this time, about 10 times more marine solid organic carbon (SOC) accumulated in marine sediments than were removed from the underlying terrestrial sediments. Indian River Lagoon thus appears to be a net sink for marine OC.

Arsenic associations in sediments from shallow aquifers of northwestern Hetao Basin, Inner Mongolia

USGS Publications Warehouse

Deng, Y.; Wang, Y.; Ma, T.; Yang, H.; He, J.

2011-01-01

Understanding the mechanism of arsenic mobilization from sediments to groundwater is important for water quality management in areas of endemic arsenic poisoning, such as the Hetao Basin in Inner Mongolia, northern China. Aquifer geochemistry was characterized at three field sites (SH, HF, TYS) in Hangjinhouqi County of northwestern Hetao Basin. The results of bulk geochemistry analysis of sediment samples indicated that total As concentrations have a range of 6. 8-58. 5 mg/kg, with a median of 14. 4 mg/kg. The highest As concentrations were found at 15-25 m depth. In the meanwhile, the range of As concentration in the sediments from background borehole is 3-21. 8 mg/kg, with a median value of 9 mg/kg. The As sediments concentrations with depth from the SH borehole were correlated with the contents of Fe, Sb, B, V, total C and total S. Generally, the abundance of elements varied with grain size, with higher concentrations in finer fractions of the sediments. Distinct lithology profile and different geochemical characteristics of aquifer sediments indicate the sediments are associated with different sources and diverse sedimentary environments. Up to one third of arsenic in the sediments could be extracted by ammonium oxalate, suggesting that Fe oxyhydroxides may be the major sink of As in the aquifer. Sequential extraction results indicate that arsenic occurs as strongly adsorbed on and/or co-precipitated with amorphous Fe oxyhydroxides in sediments accounting for 35 and 20%, respectively, of the total contents of arsenic. The release of As into groundwater may occur by desorption from the mineral surface driven by reductive dissolution of the Fe oxide minerals. Furthermore, small proportions of As associated with iron sulfides occur in the reductive sediments. ?? 2011 Springer-Verlag.

Solid-phase arsenic speciation in aquifer sediments: A micro-X-ray absorption spectroscopy approach for quantifying trace-level speciation

USGS Publications Warehouse

Nicholas, Sarah L.; Erickson, Melinda L.; Woodruff, Laurel G.; Knaeble, Alan R.; Marcus, Matthew A.; Lynch, Joshua K.; Toner, Brandy M.

2017-01-01

e of this research is to identify the solid-phase sources and geochemical mechanisms of release of As in aquifers of the Des Moines Lobe glacial advance. The overarching concept is that conditions present at the aquifer-aquitard interfaces promote a suite of geochemical reactions leading to mineral alteration and release of As to groundwater. A microprobe X-ray absorption spectroscopy (lXAS) approach is developed and applied to rotosonic drill core samples to identify the solid-phase speciation of As in aquifer, aquitard, and aquifer-aquitard interface sediments. This approach addresses the low solid-phase As concentrations, as well as the fine-scale physical and chemical heterogeneity of the sediments. The spectroscopy data are analyzed using novel cosine-distance and correlation-distance hierarchical clustering for Fe 1s and As 1s lXAS datasets. The solid-phase Fe and As speciation is then interpreted using sediment and well-water chemical data to propose solid-phase As reservoirs and release mechanisms. The results confirm that in two of the three locations studied, the glacial sediment forming the aquitard is the source of As to the aquifer sediments. The results are consistent with three different As release mechanisms: (1) desorption from Fe (oxyhydr)oxides, (2) reductive dissolution of Fe (oxyhydr)oxides, and (3) oxidative dissolution of Fe sulfides. The findings confirm that glacial sediments at the interface between aquifer and aquitard are geochemically active zones for As. The diversity of As release mechanisms is consistent with the geographic heterogeneity observed in the distribution of elevated-As wells.

The Dart estuary, Devon, UK: a case study of chemical dynamics and pollutant mobility

NASA Astrophysics Data System (ADS)

Schuwerack, P.-M. M.; Neal, M.; Neal, C.

2007-01-01

Water, sediments and gill and digestive gland tissues of adult common shore crab (Carcinus maenas), collected at Noss Marina, Sandquay (Britannia Royal Naval College), the Dartmouth Pier, Warfleet Cove and Sugary Cove in the Dart estuary, Devon, UK, were analysed for major, minor and trace elements in spring 2004. Total acid-available measurements analysed included the truly dissolved component and acid-available sediments. Trace metal concentrations are associated largely with particulate and micro-particulate/colloidal phases, the latter being able to pass through standard filter papers. Wide ranges of chemical concentrations were found in the water, sediments and tissues at all the locations. In the water column, 48% of the variance is linked to the sea-salt component (Cl, Na, K, Ca, Mg, B, Li and Sr) and the sediment-associated acid-available fractions are linked to Fe-rich lithogenous materials (Ba, Co, Cu, Fe, Mn, V and Zn). In the sediments, trace elements of Cd, Co, Cr, Fe, Pb, Mn, Ni and V are correlated with the sea salts and associated with the fraction of fine sediments within the total sediment. In the gills and the digestive gland tissues of crabs, high concentrations of Al, Cu and Fe are found and there are correlations between acid-available trace metals of Cu, Cr, Fe, Mn, Ni, Sr and Zn. The relationships between trace metal contaminants, their site-specific concentrations, their temporal and spatial variability and the effects of human activities, such as moorland/agriculture with historic mining and recreational activities in the lower Dart estuary, are discussed.

Arsenic in Holocene aquifers of the Red River floodplain, Vietnam: Effects of sediment-water interactions, sediment burial age and groundwater residence time

NASA Astrophysics Data System (ADS)

Sø, Helle Ugilt; Postma, Dieke; , Mai Lan, Vi; Pham, Thi Kim Trang; Kazmierczak, Jolanta; Dao, Viet Nga; Pi, Kunfu; Koch, Christian Bender; Pham, Hung Viet; Jakobsen, Rasmus

2018-03-01

Water-sediment interactions were investigated in arsenic contaminated Holocene aquifers of the Red River floodplain, Vietnam, in order to elucidate the origin of the spatial variability in the groundwater arsenic concentration. The investigated aquifers are spread over an 8 × 13 km field area with sediments that varied in burial age from <1 kyr to 11 kyr. The groundwater age ranged from less than 2 yr, up to a maximum near 90 yr. Groundwater As concentrations are between 0 and 6.5 μM and there are no simple correlations between the As concentration and groundwater age or aquifer sediment burial age. The aquifers are anoxic with up to 2 mM CH4 and up to 0.5 mM DOC. The downward advective DOC flux is too small to support both methanogenesis and the reduction of As-containing Fe-oxides and sedimentary carbon is therefore considered the main carbon source for the redox processes. The groundwater H2 concentration ranged between 0.1 and 4 nM. These values are intermediate between ranges characteristic for Fe-oxide reduction and methanogenesis and suggest that both processes take place simultaneously. The groundwater pe was calculated from the H2/H+ and CH4/CO2 redox couples, giving almost similar results that apparently reflects the pe of the bulk groundwater. The pe calculated for the As(III)/As(V) redox couple was found in disequilibrium with the other redox couples. Using the pe calculated from the CH4/CO2 redox couple we show that the groundwater has a reducing potential towards Fe-oxides ranging from ferrihydrite to poorly crystalline goethite, but not for well crystalline goethite or hematite. Hematite and poorly crystalline goethite were identified as the Fe-oxides present in the sediments. Reductive dissolution experiments identify two phases releasing Fe(II); one rapidly dissolving that also contains As and a second releasing Fe(II) more slowly but without As. The initial release of Fe and As occurs at a near constant As/Fe ratio that varied from site to site between 1.2 and 0.1 mmol As/mol Fe. Siderite (FeCO3) is the main sink for Fe(II), based on saturation calculations as well as the identification of siderite in the sediment. Most of the carbonate incorporated in siderite originates from the dissolution of sedimentary CaCO3. Over time the CaCO3 content of the sediments diminishes and FeCO3 appears instead. No specific secondary phases that incorporate arsenite could be identified. Alternatively, the amount of arsenic mobilized during the dissolution of reactive phases can be contained in the pool of adsorbed arsenite. Combining groundwater age with aquifer sediment age allows the calculation of the total number of pore volumes flushed through the aquifer. Comparison with groundwater chemistry shows the highest arsenic concentration to be present within the first 200 pore volumes flushed through the aquifer. These results agree with reactive transport modeling combining a kinetic description of reductive dissolution of As-containing Fe-oxide with adsorption and desorption of arsenite. Understanding variability in groundwater arsenic concentration requires appreciating the coupling of the chemical processes to both sedimentary and hydrogeological cycling.

In situ removal of copper from sediments by a galvanic cell.

PubMed

Yuan, Songhu; Wu, Chan; Wan, Jinzhong; Lu, Xiaohua

2009-01-01

This study dealt with in situ removal of copper from sediments through an electrokinetic (EK) process driven by a galvanic cell. Iron (Fe) and carbon (C) were placed separately and connected with a conductive wire. Polluted sediments were put between them and water was filled above the sediments. The galvanic cell was thus formed due to the different electrode potentials of Fe and C. The cell could remove the pollutants in the sediments by electromigration and/or electroosmosis. Results showed that a weak voltage less than 1V was formed by the galvanic cell. The voltage decreased with the increase of time. A slight increase of sediment pH from the anode (Fe) to the cathode (C) was observed. The presence of supernatant water inhibited the variation of sediment pH because H(+) and OH(-) could diffuse into the water. The removal of copper was affected by the sediment pH and the distribution of electrolyte in sediment and supernatant water. Lower pH led to higher removal efficiency. More electrolyte in the sediment and/or less electrolyte in the supernatant water favored the removal of copper. The major removal mechanism was proposed on the basis of the desorption of copper from sediment to pore solution and the subsequent electromigration of copper from the anode to the cathode. The diffusion of copper from sediment to supernatant water was negligible.

Metal Oxides in Surface Sediment Control Nickel Bioavailability to Benthic Macroinvertebrates.

PubMed

Mendonca, Raissa M; Daley, Jennifer M; Hudson, Michelle L; Schlekat, Christian E; Burton, G Allen; Costello, David M

2017-11-21

In aquatic ecosystems, the cycling and toxicity of nickel (Ni) are coupled to other elemental cycles that can limit its bioavailability. Current sediment risk assessment approaches consider acid-volatile sulfide (AVS) as the major binding phase for Ni, but have not yet incorporated ligands that are present in oxic sediments. Our study aimed to assess how metal oxides play a role in Ni bioavailability in surficial sediments exposed to effluent from two mine sites. We coupled spatially explicit sediment geochemistry (i.e., separate oxic and suboxic) to the indigenous macroinvertebrate community structure. Effluent-exposed sites contained high concentrations of sediment Ni and AVS, though roughly 80% less AVS was observed in surface sediments. Iron (Fe) oxide mineral concentrations were elevated in surface sediments and bound a substantial proportion of Ni. Redundancy analysis of the invertebrate community showed surface sediment geochemistry significantly explained shifts in community abundances. Relative abundance of the dominant mayfly (Ephemeridae) was reduced in sites with greater bioavailable Ni, but accounting for Fe oxide-bound Ni greatly decreased variation in effect thresholds between the two mine sites. Our results provide field-based evidence that solid-phase ligands in oxic sediment, most notably Fe oxides, may have a critical role in controlling nickel bioavailability.

Heavy metals in water, sediments, plants and fish of Kali Nadi U. P. (India)

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

Ajmal, M.; Uddin, R.; Khan, A.U.

1988-01-01

The distribution of heavy metals viz., Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn in the water, sediments, plants and fish samples collected from the Kali Nadi (India) have been determined. The studies have shown that there was considerable variation in the concentration of heavy metals from one sampling station to the other which may be due to the variation in the quality of industrial and sewage wastes being added to the river at different places. The orders of the concentration of heavy metals in water, sediments, plants (Eicchornia crassipes) and fish (Heteropnuestes fossilis) were Fe > Znmore » > Cu > Mn > Cr > Ni > Pb > Co > Cd; Fe > Zn > Mn > Ni > Cr > Co > Cu > Pb > Cd; Fe > Mn > Zn > Cu > Ni > Co > Pb > Cr > Cd and Fe > Zn > Mn > Ni > Pb >Co > Cr > Cu > Cd, respectively.« less

Salton Sea 1/sup 0/ x 2/sup 0/ NTMS area California and Arizona: data report (abbreviated)

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

Heffner, J.D.

1980-09-01

Surface sediment samples were collected at 997 sites. Ground water samples were collected at 76 sites. Neutron activation analysis results are given for uranium and 16 other elements in sediments, and for uranium and 9 other elements in ground water. Mass spectrometry results are given for helium in ground water. Data from ground water sites include (1) water chemistry measurements (pH, conductivity, and alkalinity) (2) physical measurements (water temperature, well description where applicable, and scintillometer reading) and (3) elemental analyses (U, Al, Br, Cl, Dy, F, He, Mg, Mn, Na and V). Data from sediment sites include (1) stream watermore » chemistry measurements from sites where water was available and (2) elemental analyses (U, Th, Hf, Al, Ce, Dy, Eu, Fe, La, Lu, Mn, Sc, Sm, Na, Ti, V, and Yb). Sample site descriptors are given. Areal distribution maps, histograms, and cumulative frequency plots for the elements listed above; U/Th and U/Hf ratios; and scintillometer readings at sediment sample sites are included. Analyses of the sediment fraction finer than 149..mu..m show high uranium values clustered in the Eagle and Chuckwalla Mountains. High uranium values in the 420 ..mu..m to 1000 ..mu..m fraction are clustered in the McCoy Mountains. Both fractions show groups of high values in the Chocolate Mountains at the Southeastern edge of the Chocolate Mountains Aerial Gunnery Range. Aerial distribution of analytical values shows that high values of many elements in both size fractions are grouped around the Eagle Mountains and the Chuckwalla Mountains. Fe, Mn, Ti, V, Sc, Hf, and the rare earth elements, all of which typically occur in high-density minerals, have higher average (log mean) concentrations in the finer fraction than in the coarser fraction.« less

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

Wu, T.; Griffin, A. M.; Gorski, C. A.

Dissimilatory microbial reduction of solid-phase Fe(III)-oxides and Fe(III)-bearing phyllosilicates (Fe(III)-phyllosilicates) is an important process in anoxic soils, sediments, and subsurface materials. Although various studies have documented the relative extent of microbial reduction of single-phase Fe(III)-oxides and Fe(III)-phyllosilicates, detailed information is not available on interaction between these two processes in situations where both phases are available for microbial reduction. The goal of this research was to use the model dissimilatory iron-reducing bacterium (DIRB) Geobacter sulfurreducens to study Fe(III)-oxide vs. Fe(III)-phyllosilicate reduction in a range of subsurface materials and Fe(III)-oxide stripped versions of the materials. Low temperature (12K) Mossbauer spectroscopy was usedmore » to infer changes in the relative abundances of Fe(III)-oxide, Fe(III)-phyllosilicate, and phyllosilicate-associated Fe(II) (Fe(II)-phyllosilicate). A Fe partitioning model was employed to analyze the fate of Fe(II) and assess the potential for abiotic Fe(II)-catalyzed reduction of Fe(III)-phyllosilicates. The results showed that in most cases Fe(III)- oxide utilization dominated (70-100 %) bulk Fe(III) reduction activity, and that electron transfer from oxide-derived Fe(II) played only a minor role (ca. 10-20 %) in Fe partitioning. In addition, the extent of Fe(III)-oxide reduction was positively correlated to surface area-normalized cation exchange capacity and the phyllosilicate-Fe(III)/total Fe(III) ratio, which suggests that the phyllosilicates in the natural sediments promoted Fe(III)-oxide reduction by binding of oxide-derived Fe(II), thereby enhancing Fe(III)-oxide reduction by reducing or delaying the inhibitory effect that Fe(II) accumulation on oxide and DIRB cell surfaces has on Fe(III)-oxide reduction. In general our results suggest that although Fe(III)-oxide reduction is likely to dominate bulk Fe(III) reduction in most subsurface sediments, Fe(II) binding by phyllosilicates is likely to play a key role in controlling the long-term kinetics of Fe(III)-oxide reduction.« less

Fe-rich carbonate chimney in Okinawa Trough Implication for Fe-driven Microbial Anaerobic Oxidation of Methane (AMO)

NASA Astrophysics Data System (ADS)

Peng, X.; Guo, Z.

2016-12-01

Marine sediments associated with cold seeps at continental margins discharge substantial amounts of methane. Microbial anaerobic oxidation of methane (AMO) is a key biogeochemical process in these environments, which can trigger the formation of carbonate chimneys within sediments. The exact biogeochemical mechanism of how AMO control the formation of carbonate chimneys and influence their mineralogy and chemistry remains poorly constrained. Here, we use nano-scale secondary ion mass spectrometry to characterize the petrology and geochemistry of methane-derived Fe-rich carbonate chimneys formed between 5-7 Ma in the Northern Okinawa Trough. We find abundant framboid pyrites formed in the authigenic carbonates in the chimneys, indicating a non-Fe limitation sedimentary system. The δ13C values of carbonate (-18.9‰ to -45.9‰, PDB) show their probable origin from a mixing source of biogenic and thermogenic methane. The δ34S values range from -3.9 ± 0.5‰ to 23.2 ± 0.5‰ (VCDT), indicative of a strong exhaustion of sulfates in a local sulfate pool. We proposed that Fe-rich carbonate chimneys formed at the bottom of the sulfate-methane transition zone, beneath which Fe-driven AOM may happen and provide available ferrous for the extensive precipitation of pyrite in carbonate chimneys. The accumulation of reductive Fe in sediments via this process may widely occur in other analogous settings, with important application for Fe and S biogeochemical cycling within deep sediments at continental margins.

[Limnology of high mountain tropical lake, in Ecuador: characteristics of sediments and rate of sedimentation].

PubMed

Gunkel, Günter

2003-06-01

Equatorial high mountain lakes are a special type of lake occurring mainly in the South American Andes as well as in Central Africa and Asia. They occur at altitudes of a few thousand meters above sea level and are cold-water lakes (< 20 degrees C). Relatively little is known about them. A long-term limnological study was therefore undertaken at Lake San Pablo, Ecuador, to analyze the basic limnological processes of the lake, which has a tendency for eutrophication. Sediment quality of San Pablo Lake is given under consideration of horizontal and vertical distribution using sediment cores. Significance of sediments for eutrophication process of lakes is demonstrated using phosphorus concentration of sediments as well as the phosphorus retention capacity of the sediments by ratio Fe/P. Dating of the sediments is done using 137Cs and 210Pb, but the activity of 137Cs in the sediment was very low nearly at the detection level. Sedimentation rate is determined to be 3.5 mm/year and the sediment cores represent about 110 years. P concentration of the sediments is high (approximately 5 g/kg dry substance), and P retention capacity by Fe is insufficient (Fe/P = 4). The sediment quality did not change significantly during the past decades, and the trophic state of San Pablo Lake was already less or more eutrophic 110 years ago. The contamination of the lake sediments by heavy metals is insignificant.

Investigation of heavy metals release from sediment with bioturbation/bioirrigation.

PubMed

He, Yi; Men, Bin; Yang, Xiaofang; Li, Yaxuan; Xu, Hui; Wang, Dongsheng

2017-10-01

Bioturbation/bioirrigation can affect the remobilization of metals from sediments. In this study, experiments were performed to examine the effect of bioturbation/bioirrigation by different organisms on cadmium (Cd), copper (Cu), zinc (Zn) and lead (Pb) releasing from the spiked sediment. The diffusive gradient in thin films technique (DGT) revealed that at the end of exposure time, the labile heavy metals concentrations in the pore water for all metal and organisms combinations except Cu and chironomid larvae were much lower than that in the control group. However, the concentrations of heavy metals detected by the DGT were virtually indistinguishable among the treatments with tubificid, chironomid larvae and loach. The correlation analysis of heavy metals with iron (Fe) and manganese (Mn) suggested that Cd, Zn and Pb were most likely bound as Fe-Mn oxidation form in the pore water, but Cu was in other forms. After 28 d of exposure, bioturbation/bioirrigation produced a significant release of particulate heavy metals into the overlying water, especially in the treatment with loach. The bioturbation/bioirrigation impact on the Pb remobilization was less than the other three heavy metals. The effects of bioturbaiton/bioirrigation on the heavy metals remobilization in the sediment were complex that with studying the heavy metals remobilization in the sediment and water interface, the biological indicators should be recommended. Copyright © 2017 Elsevier Ltd. All rights reserved.

Evidence for the Existence of Autotrophic Nitrate-Reducing Fe(II)-Oxidizing Bacteria in Marine Coastal Sediment

PubMed Central

Laufer, Katja; Røy, Hans; Jørgensen, Bo Barker

2016-01-01

ABSTRACT Nitrate-reducing Fe(II)-oxidizing microorganisms were described for the first time ca. 20 years ago. Most pure cultures of nitrate-reducing Fe(II) oxidizers can oxidize Fe(II) only under mixotrophic conditions, i.e., when an organic cosubstrate is provided. A small number of nitrate-reducing Fe(II)-oxidizing cultures have been proposed to grow autotrophically, but unambiguous evidence for autotrophy has not always been provided. Thus, it is still unclear whether or to what extent Fe(II) oxidation coupled to nitrate reduction is an enzymatically catalyzed and energy-yielding autotrophic process or whether Fe(II) is abiotically oxidized by nitrite from heterotrophic nitrate reduction. The aim of the present study was to find evidence for the existence of autotrophic nitrate-reducing Fe(II) oxidizers in coastal marine sediments. Microcosm incubations showed that with increasing incubation times, the stoichiometric ratio of reduced nitrate/oxidized Fe(II) [NO3−reduced/Fe(II)oxidized] decreased, indicating a decreasing contribution of heterotrophic denitrification and/or an increasing contribution of autotrophic nitrate-reducing Fe(II) oxidation over time. After incubations of sediment slurries for >10 weeks, nitrate-reducing activity ceased, although nitrate was still present. This suggests that heterotrophic nitrate reduction had ceased due to the depletion of readily available organic carbon. However, after the addition of Fe(II) to these batch incubation mixtures, the nitrate-reducing activity resumed, and Fe(II) was oxidized, indicating the activity of autotrophic nitrate-reducing Fe(II) oxidizers. The concurrent reduction of 14C-labeled bicarbonate concentrations unambiguously proved that autotrophic C fixation occurred during Fe(II) oxidation and nitrate reduction. Our results clearly demonstrated that autotrophic nitrate-reducing Fe(II)-oxidizing bacteria were present in the investigated coastal marine sediments. IMPORTANCE Twenty years after the discovery of nitrate-reducing Fe(II) oxidizers, it is still controversially discussed whether autotrophic nitrate-reducing Fe(II)-oxidizing microorganisms exist and to what extent Fe(II) oxidation in this reduction/oxidation process is enzymatically catalyzed or which role abiotic side reactions of Fe(II) with reactive N species play. Most pure cultures of nitrate-reducing Fe(II) oxidizers are mixotrophic; i.e., they need an organic cosubstrate to maintain their activity over several cultural transfers. For the few existing autotrophic isolates and enrichment cultures, either the mechanism of nitrate-reducing Fe(II) oxidation is not known or evidence for their autotrophic lifestyle is controversial. In the present study, we provide evidence for the existence of autotrophic nitrate-reducing Fe(II) oxidizers in coastal marine sediments. The evidence is based on stoichiometries of nitrate reduction and Fe(II) oxidation determined in microcosm incubations and the incorporation of carbon from CO2 under conditions that favor the activity of nitrate-reducing Fe(II) oxidizers. PMID:27496777

Mobility and chemical fate of arsenic and antimony in water and sediments of Sarouq River catchment, Takab geothermal field, northwest Iran.

PubMed

Sharifi, Reza; Moore, Farid; Keshavarzi, Behnam

2016-04-01

Arsenic (As) and antimony (Sb) concentrations in water and sediments were determined along flow paths in the Sarouq River, Zarshuran and Agh Darreh streams. The results indicate high As and Sb concentrations in water and sediment samples. Raman spectroscopy shows hematite (α-Fe2O3), goethite [α-FeO(OH)] and lepidocrocite [γ-FeO(OH)] in sediment samples. Calculated saturation indices (SI) indicate oversaturation with respect to amorphous Fe(OH)3 for all samples, but undersaturation with respect to Al and Mn mineral and amorphous phases. Therefore, ferric oxides and hydroxides are assumed to be principal mineral phases for arsenic and antimony attenuation by adsorption/co-precipitation processes. The considerable difference between As and Sb concentration in sediment is due to strong adsorption of As(V) into the solid phase. Also, lower affinity of Sb(V) for mineral surfaces suggests a greater potential for aqueous transport. The adsorption of arsenic and antimony was examined using the Freundlich adsorption isotherm to determine their distribution model in water-sediment system and its compatibility with the existing theoretical model. The results showed that the adsorption behavior of both elements complies with the Freundlich adsorption isotherm. Copyright © 2016 Elsevier Ltd. All rights reserved.

Metal (Al, Fe, Mn and Cu) distributions and origins of polycyclic aromatic hydrocarbons (PAHs) in the surface sediments of the Marmara Sea and the coast of Istanbul, Turkey.

PubMed

Taşkın, Ö S; Aksu, A; Balkıs, N

2011-11-01

In this study, total metal (Al, Fe, Mn and Cu) and PAHs analyses have been done in the surface sediments. Sediment samples have been collected from seven parts of the Marmara Sea and the coast of Istanbul during 2009. Total Al, Fe, Mn and Cu contents vary between 1.8% and 5.4%; 1.1% and 2.8%; 122 and 259 μg g(-1); 27 and 416 μg g(-1), respectively. EF and CF values of Fe and Mn are lower than 1.5 and 1, respectively, in all the stations. Total PAH contents range between 135 and 6009 ng g(-1) in the surface sediments. The origin of PAHs has been found pyrolitic according to the Phe/Ant ratio in the all stations. Contrastingly, at K0, MKC and MY1 Stations, PAH origins have been observed petrogenic according to the Flu/Pyr ratio. Copyright © 2011 Elsevier Ltd. All rights reserved.

Metalliferous sediments from Eolo Seamount (Tyrrhenian Sea): Hydrothermal deposition and re-deposition in a zone of oxygen depletion

USGS Publications Warehouse

Dekov, V.M.; Kamenov, George D.; Savelli, C.; Stummeyer, Jens; Thiry, M.; Shanks, Wayne C.; Willingham, A.L.; Boycheva, T.B.; Rochette, P.; Kuzmann, E.; Fortin, D.; Vertes, A.

2009-01-01

A sediment core taken from the south-east slope of the Eolo Seamount is composed of alternating red-brown and light-brown to bluish-grey layers with signs of re-deposition in the middle-upper section. The red-brown layers are Fe-rich metalliferous sediments formed as a result of low-temperature (??? 77????C) hydrothermal discharge, whereas the bluish-grey layers most probably originated from background sedimentation of Al-rich detrital material. The metalliferous layers are composed mainly of Si-rich goethite containing some Al. Co-precipitation of hydrothermally released SiO44- and Fe2+ as amorphous or poorly crystalline Fe-Si-oxyhydroxides explains the high Si concentration in goethite. The elevated Al content of the goethite is fairly unusual, but reflects the extremely high background Al content of the Tyrrhenian seawater due to the high eolian terrigenous flux from the Sahara desert. The Sr and Nd isotope data suggest that the Eolo metalliferous sediments are the product of a 3-component mixture: hydrothermal fluid, seawater, and detrital material (Saharan dust and Aeolian Arc material). The enrichment in Fe, P, As, Mo, Cd, Be, Sb, W, Y, V, depletion in REE and transition elements (Cu, Co, Ni, Zn) and the REE distribution patterns support the low-temperature hydrothermal deposition of the metalliferous layers. The hydrothermal field is located in a seawater layer of relative O2 depletion, which led to a significant fractionation of the hydrothermally emitted Fe and Mn. Fe-oxyhydroxides precipitated immediately around the vents whereas Mn stayed in solution longer and the Mn-oxides precipitated higher up on the seamount slope in seawater with relatively higher O2 levels. High seismic activity led to sediment re-deposition and slumping of the Mn-rich layers down slope and mixing with the Fe-rich layers. ?? 2009 Elsevier B.V. All rights reserved.

Diffusion-reaction modelling of early diagenesis of sediments affected by acid mine drainage.

NASA Astrophysics Data System (ADS)

Torres, E.; Ayora, C.; Arias, J. L.; Garcia Robledo, E.; Papaspyrou, S.; Corzo, A.

2012-04-01

The Sancho Reservoir (SW Spain) is a monomictic water reservoir affected by acid mine drainage. It has a pH of ~4, with high sulfate (200 ppm) and heavy metal concentrations in the water column. The reservoir develops reducing conditions at the bottom during the stratification period. A laboratory experiment was carried out to study the effect of this oxygen variation on the early diagenesis processes and the cycling of metals. Sediment cores and bottom water were collected during the stratification period and brought to the laboratory. The cores were maintained in an aquarium bubbled with nitrogen gas to maintain hypoxic conditions (~10 µmol O2 L-1) for 1 day. Then, oxic conditions were induced by bubbling with air and maintained for 50 days. Finally, hypoxia was re-established for 10 days. Triplicate cores were sliced in a anaerobic glove box at each stage. Pore water was extracted by centrifugation and: Eh, pH, DO, DOC, sulfate, Fe and trace metals were analyzed. The sediment was freeze-dried and a sequential extraction protocol was applied to determine the exchangeable, AVS, Fe-(oxy)hydroxides, Fe-oxides, organic matter, pyrite sulfur and residual phase iron fractions. Organic carbon and total C, N, H and S were also analyzed in the sediment. A reactive diffusion model has been used to obtain the rates of biogeochemical reactions by fitting to the experimental data. During hypoxic conditions sulfate and Fe-(oxy)hydroxides are reduced, due to the anaerobic oxidation of organic matter, at the very first few cm, releasing sulfide and Fe(II) which precipitate as iron sulfide. When oxygen diffuses in the sediment, sulfate-reduction and the sulfide peaks are displaced deeper into the sediment. Oxygen penetration depth and its consumption rates in the sediment increase quickly, resulting in the reoxidation of the iron sulfides that had precipitated during hypoxic conditions. Sulfide and Fe(II) are released and are again oxidized to Fe(III) and sulfate respectively. Arsenic can be adsorbed onto the iron sulfides and pyrite. During the dissolution of the iron sulfide As will be released and will diffuse to the water column. Copper and zinc can also precipitate as metal sulfides.

Core drilling provides information about Santa Fe Group aquifer system beneath Albuquerque's West Mesa

USGS Publications Warehouse

Allen, B.D.; Connell, S.D.; Hawley, J.W.; Stone, B.D.

1998-01-01

Core samples from the upper ???1500 ft of the Santa Fe Group in the Albuquerque West Mesa area provide a first-hand look at the sediments and at subsurface stratigraphic relationships in this important part of the basin-fill aquifer system. Two major hydrostratigraphic subunits consisting of a lower coarse-grained, sandy interval and an overlying fine-grained, interbedded silty sand and clay interval lie beneath the water table at the 98th St core hole. Borehole electrical conductivity measurements reproduce major textural changes observed in the recovered cores and support subsurface correlations of hydrostratigraphic units in the Santa Fe Group aquifer system based on geophysical logs. Comparison of electrical logs from the core hole and from nearby city wells reveals laterally consistent lithostratigraphic patterns over much of the metropolitan area west of the Rio Grande that may be used to delineate structural and related stratigraphic features that have a direct bearing on the availability of ground water.

Geochemical effects of rapid sedimentation in aquatic systems: Minimal diagenesis and the preservation of historical metal signatures

USGS Publications Warehouse

Callender, E.

2000-01-01

Rapid sedimentation exerts a pronounced influence on early sedimentary diagenesis in that there is insufficient time for a sediment particle to equilibrate in any one sediment layer before that layer may be displaced vertically by another layer. These sedimentation patterns are common in surface-water reservoirs whose sedimentation rates (1-10 cm yr-1) are several orders of magnitude greater than those for natural lakes (0.01-0.5 cm yr-1). Two examples of the effects of rapid sedimentation on geochemical metal signatures are presented here. Interstitial-water data (Fe) from two sites in the Cheyenne River Embayment of Lake Oahe on the Missouri River illustrate the effects of changing sedimentation rates on dissolved species. Rapid burial during high-flow yrs appears to limit early sedimentary diagenesis to aerobic respiration. Solid-phase metal data (Pb) from a site in Pueblo Reservoir on the upper Arkansas River in Colorado appear to record historical releases by flooding of abandoned mine sites upstream in Leadville, Colorado. Interstitial-water ammonia and ferrous Fe data indicate that at least one interval at depth in the sediment where solid metal concentrations peak is a zone of minimal diagenesis. The principal diagenetic reactions that occur in these sediments are aerobic respiration and the reduction of Mn and Fe oxides. Under slower sedimentation conditions, there is sufficient time for particulate organic matter to decompose and create a diagenetic environment where metal oxides may not be stable. The quasi-steady-state interstitial Fe profiles from Tidal Potomac River sediments are an example of such a situation. This occurs primarily because the residence time of particles in the surficial sediment column is long enough to allow benthic organisms and bacteria to perform their metabolic functions. When faster sedimentation prevails, there is less time for these metabolic reactions to occur since the organisms do not occupy a sediment layer for any length of time. Also, the quantity and quality of the organic matter input to the sediment layer is important in that reservoirs often receive more terrestrial organic matter than natural lakes and this terrestrial organic matter is generally more refractory than autochthonous aquatic organic matter.

Characterization of Fe(II) oxidizing bacterial activities and communities at two acidic Appalachian coalmine drainage-impacted sites

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

Senko, John M.; Wanjugi, Pauline; Lucas, Melanie

2008-06-12

We characterized the microbiologically mediated oxidative precipitation of Fe(II) from coalminederived acidic mine drainage (AMD) along flow-paths at two sites in northern Pennsylvania. At the Gum Boot site, dissolved Fe(II) was efficiently removed from AMD whereas minimal Fe(II) removal occurred at the Fridays-2 site. Neither site received human intervention to treat the AMD. Culturable Fe(II) oxidizing bacteria were most abundant at sampling locations along the AMD flow path corresponding to greatest Fe(II) removal and where overlying water contained abundant dissolved O2. Rates of Fe(II) oxidation determined in laboratory-based sediment incubations were also greatest at these sampling locations. Ribosomal RNA intergenicmore » spacer analysis and sequencing of partial 16S rRNA genes recovered from sediment bacterial communities revealed similarities among populations at points receiving regular inputs of Fe(II)-rich AMD and provided evidence for the presence of bacterial lineages capable of Fe(II) oxidation. A notable difference between bacterial communities at the two sites was the abundance of Chloroflexi-affiliated 16S rRNA gene sequences in clone libraries derived from the Gum Boot sediments. Our results suggest that inexpensive and reliable AMD treatment strategies can be implemented by mimicking the conditions present at the Gum Boot field site.« less

Influence of Dissolved Organic Matter and Fe (II) on the Abiotic Reduction of Pentachloronitrobenzene

EPA Science Inventory

Nitroaromatic pesticides (NAPs) are hydrophobic contaminants that can accumulate in sediments by the deposition of suspended solids from surface waters. Fe(II) and dissolved organic matter (DOM), present in suboxic and anoxic zones of freshwater sediments, can transform NAPs in n...

The Rusty Sink: Iron Promotes the Preservation of Organic Matter in Sediments

NASA Astrophysics Data System (ADS)

Lalonde, K. M.; Mucci, A.; Moritz, A.; Ouellet, A.; Gelinas, Y.

2011-12-01

The biogeochemical cycles of iron (Fe) and organic carbon (OC) are strongly interlinked. In oceanic waters, organic ligands have been shown to control the concentration of dissolved Fe [1], whereas in soils, solid Fe phases provide a sheltering and preservative effect for organic matter [2]. Until now however, the role of iron in the preservation of OC in sediments has not been clearly established. Here we show that 21.5 ± 8.6% of the OC in sediments is directly bound to reactive iron phases, which promote the preservation of OC in sediments. Iron-bound OC represents a global mass of 19 to 45 × 10^15 g of OC in surface marine sediments. This pool of OC is different from the rest of sedimentary OC, with 13C and nitrogen-enriched organic matter preferentially bound to Fe which suggests that biochemical fractionation occurs with OC-Fe binding. Preferential binding also affects the recovery of high molecular weight lipid biomarkers and acidic lignin oxidation products, changing the environmental message of proxies derived from these biomarkers. [1] Johnson, K. S., Gordon, R. M. & Coale, K. H. What controls dissolved iron in the world ocean? Marine Chemistry 57, 137-161 (1997). [2] Kaiser, K. & Guggenberger, G. The role of DOM sorption to mineral surfaces in the preservation of organic matter in soils. Organic Geochemistry 31, 711-725 (2000).

Survival of the fittest: phosphorus burial in the sulfidic deep Black Sea

NASA Astrophysics Data System (ADS)

Kraal, Peter; Dijkstra, Nikki; Behrends, Thilo; Slomp, Caroline

2016-04-01

The Black Sea is characterized by permanently anoxic and sulfidic deep waters. Studies of the mechanisms of P burial in such a setting can be used to improve our understanding of P cycling in modern coastal systems undergoing eutrophication and ancient oceans during periods of anoxia in Earth's past. Here, we present phosphorus and iron (Fe) pools as determined in surface sediments along a transect from oxic shallow waters to sulfidic deep waters in the northwestern Black Sea, using a combination of bulk chemical analyses and micro-scale X-ray fluorescence (μXRF) and X-ray absorption spectroscopy (μXAS). We show that under oxic bottom water conditions, ferric iron oxides (Fe(III)ox) in surficial sediment efficiently scavenge dissolved phosphate from pore waters. Under these conditions, Fe(III)ox-bound P constitutes the main P pool at the sediment surface, but rapidly declines with depth in the sediment due to anoxic diagenesis. The transition from shallow (oxic) to deep (sulfidic) waters along the depth transect is reflected in a slight increase in the fraction of organic P. We also show evidence for authigenic calcium phosphate formation under sulfidic conditions at relatively low dissolved PO4 concentrations. Furthermore, we provide spectroscopic evidence for the presence of Fe(II)-Mn(II)-Mg-P minerals in sediments of the sulfidic deep basin. We hypothesize that these minerals are formed as a result of input of Fe(III)ox-P from shallower waters and subsequent transformation in either the water column or sediment. This finding suggests an unexpected strength of Fe-P shuttling from the shelf to the deep basin. While the presence of Fe-P species in such a highly sulfidic environment is remarkable, further analysis suggests that this P pool may not be quantitatively significant. In fact, our results indicate that some of the P that is interpreted as Fe-bound P based on chemical extraction may in fact be Ca-associated PO4 consisting of a combination of fish debris and adsorbed P.

Reactivity of Uranium and Ferrous Iron with Natural Iron Oxyhydroxides.

PubMed

Stewart, Brandy D; Cismasu, A Cristina; Williams, Kenneth H; Peyton, Brent M; Nico, Peter S

2015-09-01

Determining key reaction pathways involving uranium and iron oxyhydroxides under oxic and anoxic conditions is essential for understanding uranium mobility as well as other iron oxyhydroxide mediated processes, particularly near redox boundaries where redox conditions change rapidly in time and space. Here we examine the reactivity of a ferrihydrite-rich sediment from a surface seep adjacent to a redox boundary at the Rifle, Colorado field site. Iron(II)-sediment incubation experiments indicate that the natural ferrihydrite fraction of the sediment is not susceptible to reductive transformation under conditions that trigger significant mineralogical transformations of synthetic ferrihydrite. No measurable Fe(II)-promoted transformation was observed when the Rifle sediment was exposed to 30 mM Fe(II) for up to 2 weeks. Incubation of the Rifle sediment with 3 mM Fe(II) and 0.2 mM U(VI) for 15 days shows no measurable incorporation of U(VI) into the mineral structure or reduction of U(VI) to U(IV). Results indicate a significantly decreased reactivity of naturally occurring Fe oxyhydroxides as compared to synthetic minerals, likely due to the association of impurities (e.g., Si, organic matter), with implications for the mobility and bioavailability of uranium and other associated species in field environments.

Tracking Changes in Iron Mineralogy Through Time in Gale Crater and Terrestrial Analogues

NASA Astrophysics Data System (ADS)

Sheppard, R.; Milliken, R.; Russell, J. M.

2017-12-01

Iron and other redox-sensitive elements measured in ancient mudstones of Gale Crater, Mars by the Curiosity rover can provide information on past climate and interactions between water and the early atmosphere. Preserved ferrous mineralogy can constrain lake bottom water conditions and potentially the relative position of the oxycline and/or shoreline through the stratigraphic section. Multiple oxidation states in a given assemblage may also indicate a potential energy source for microbes. The X-ray amorphous fraction of all rocks measured in Gale Crater to date is also enigmatic: it can constitute up to 50 wt% of the sediment but the precise composition and formation conditions are unknown. Features similar to those in the martian mudstones are seen in sediments from the terrestrial redox-stratified Lake Towuti, including alternating ferrous and ferric mineralogy and an abundant Fe-rich X-ray amorphous phase. To constrain conditions in the water column and early diagenetic processes, we present trends in chemistry and mineralogy for sediment acquired from soils in the mafic/ultramafic catchment and lake bottom/core samples. The soils contain high abundances of crystalline Fe-oxides (e.g. magnetite, goethite, hematite), whereas sediment from the very surface of the lake bottom maintain high Fe but not in crystalline form based on XRD. This suggests Fe is being rapidly cycled to form amorphous phases after entering the lake. Sequential extractions to isolate highly reactive iron (e.g. ferrihydrite) will be used to confirm the relative abundance of poorly crystalline phases in catchment versus lake sediment. Sediments from a 150 m core representing 1 Myr lake history also maintain high Fe content and distinct alternating bands of red and green sediment, but there are no crystalline Fe-oxides discernible in XRD data. The process(es) and timescale for this switching is not yet known, but understanding the conditions that allow ferrous vs. ferric iron to form, and what other changes happen concurrently with silicates such as clay minerals, may help constrain how to interpret lake sediment chemistry and mineralogy in terms of climate on Earth and Mars.

Biogeochemical interactions among the arsenic, iron, humic substances, and microbes in mud volcanoes in southern Taiwan.

PubMed

Liu, Chia-Chuan; Maity, Jyoti Prakash; Jean, Jiin-Shuh; Sracek, Ondra; Kar, Sandeep; Li, Zhaohui; Bundschuh, Jochen; Chen, Chien-Yen; Lu, Hsueh-Yu

2011-01-01

Fluid and mud samples collected from Hsiaokunshui (HKS), Wushanting (WST), Yenshuikeng (YSK), Kunshuiping (KSP), Liyushan (LYS), and Sinyangnyuhu (SYNH) mud volcanoes of southwestern Taiwan were characterized for major ions, humic substances (HS) and trace elements concentrations. The relationship between the release of arsenic (As) and activities of sulfate-reducing bacteria has been assessed to understand relevant geochemical processes in the mud volcanoes. Arsenic (0.02-0.06 mg/L) and humic substances (4.13 × 10(-4) to 1.64 × 10(-3) mM) in the fluids of mud volcanoes showed a positive correlation (r = 0.99, p < 0.05) except in Liyushan mud volcano. Arsenic and iron in mud sediments formed two separate groups i) high As, but low Fe in HKS, WST, and SYNH; and ii) low As, but high Fe in the YSK, KSP, and LYS mud volcanoes. The Eh(S.H.E.) values of the mud volcano liquids were characterized by mild to strongly reducing conditions. The HKS, SYNH, and WST mud volcanoes (near the Chishan Fault) belongs to strong reducing environment (-33 to -116 mV), whereas the LYS, YSK, and KSP mud volcanoes located near the coastal plain are under mild reducing environment (-11 to 172 mV). At low Eh values mud volcanoes, saturation index (SI) values of poorly crystalline phases such as amorphous ferric hydroxide indicate understaturation, whereas saturation is reached in relatively high Eh(S.H.E.) values mud volcanoes. Arsenic contents in sediments are low, presumably due to its release to fluids (As/Fe ratio in YSK, KSP, and LYS sediment: 4.86 × 10(-4)-6.20 × 10(-4)). At low Eh(S.H.E.) values (mild to strong reducing environment), arsenic may co-precipitate with sulfides as a consequence of sulfate reduction (As/Fe ratios in WST, HKS, and SYNH sediments: 0.42-0.69).

Phosphate mineral formation in Lake Baikal sediments and implications for paleoclimate

NASA Astrophysics Data System (ADS)

Fagel, N.; Alleman, L. Y.; André, L.; Cloots, R.; Hatert, F.; Juvigné, E.; Renson, V.

2003-04-01

The more than 20 million years old Lake Baikal sedimentary record provides a good climate archive. While most paleoclimate reconstructions are mainly based on biotic proxies, we tested in this study other minerogenic tracers. In particular, it was suggested that the formation of authigenic and/or diagenetic phosphate minerals in Baïkal sediments underlines transitions from glacial to interglacial periods (Deike et al., 1997). The phosphate mineral formation previously evidenced (Müller et al., 2002) may be sensitive to suspended sediment concentrations: glacial periods are characterised by high detrital discharge, interglacial intervals are marked by low detrital supply but high biogenic sedimentation. Phosphate minerals were observed in Baïkal sediments from recent to 65 kyr BP. Their abundance was related to the sedimentation rate, the phosphate enrichment layers being particularly common on low sedimentation site, i.e., the Academician Ridge. Major and trace elements have been analysed by ICP-AES and ICP-MS on four cores drilled on topographic hills, in the southern basin (Posolsky bank, CON01-604), in the central part (Academician Ridge, VER98-1-3 and VER98-1-14) and in the northern basin (Continent Ridge, CON01-603). The geochemical signature is consistent with the occurrence of Mn-Fe-phosphate minerals. For instance P2O5 reaches up to 3% wt. relative to a mean value of 0.3 in the background sediment, MnO2 presents an enrichment factor up to 6. There is no associated enrichment in any of the trace elements measured at the same levels. In the sediments, those P-Mn-Fe rich levels are related either to sparse millimetric dark concretions or to a layer (or a group of layers) defined by an alignment of numerous concretions but there is no so-called crusts. The concretions, isolated by >63 mm sieving, present a lamellar morphology. They are identified as Fe-phosphate phases with a variable proportion of Mn. The powder diffraction diagram is consistent with vivianite, a mineral that has been previously characterized in lacustrine sediments worldwide, including Baïkal. However, its precise formation process is not yet fully understood. Dean et al. (2002) emphasize that the occurrence of phosphate minerals in Elk lake (USA) is indicative of the paleo-productivity of the water-column. For Deike et al. (2002), phosphate crusts mainly accumulate under slow sedimentation conditions. We discuss the paleo-environmental implications of the occurrence of phosphate minerals in sediments. By studying the distribution of the phosphate concretions in sedimentary columns characterised under different sedimentary conditions, we would like to point up the implications of phosphate minerals for paleoclimate reconstruction. Dean et al., 2002. A 1500-year record of climatic and environmental change in Elk Lake, Cearwater County, Minnesota II : Geochemistry , mineralogy, and stable isotopes. J. Paleolimn. 27, 301-319. Müller et al., 2002. P, As, Sb, Mo, and other elements in sedimentary Fe/Mn layers of Lake Baïkal, Environmental Science and Technology, 36, 411-420. Deike et al., 1997. Formation of ferric iron crusts in quaternnary sediments of Lake Baikal, Russia and implications for paleoclimate. Marine Geology 139, 21-46.

Adsorption and desorption of arsenic to aquifer sediment on the Red River floodplain at Nam Du, Vietnam

PubMed Central

Thi Hoa Mai, Nguyen; Postma, Dieke; Thi Kim Trang, Pham; Jessen, Søren; Hung Viet, Pham; Larsen, Flemming

2016-01-01

The adsorption of arsenic onto aquifer sediment from the Red River floodplain, Vietnam, was determined in a series of batch experiments. Due to water supply pumping, river water infiltrates into the aquifer at the field site and has leached the uppermost aquifer sediments. The leached sediments, remain anoxic but contain little reactive arsenic and iron, and are used in our experiments. The adsorption and desorption experiments were carried out by addition or removal of arsenic from the aqueous phase in sediment suspensions under strictly anoxic conditions. Also the effects of HCO3, Fe(II), PO4 and Si on arsenic adsorption were explored. The results show much stronger adsorption of As(V) as compared to As(III), full reversibility for As(III) adsorption and less so for As(V). The presence or absence of HCO3 did not influence arsenic adsorption. Fe(II) enhanced As(V) sorption but did not influence the adsorption of As(III) in any way. During simultaneous adsorption of As(III) and Fe(II), As(III) was found to be fully desorbable while Fe(II) was completely irreversibly adsorbed and clearly the two sorption processes are uncoupled. Phosphate was the only solute that significantly could displace As(III) from the sediment surface. Compiling literature data on arsenic adsorption to aquifer sediment in Vietnam and Bangladesh revealed As(III) isotherms to be almost identical regardless of the nature of the sediment or the site of sampling. In contrast, there was a large variation in As(V) adsorption isotherms between studies. A tentative conclusion is that As(III) and As(V) are not adsorbing onto the same sediment surface sites. The adsorption behavior of arsenic onto aquifer sediments and synthetic Fe-oxides is compared. Particularly, the much stronger adsorption of As(V) than of As(III) onto Red River as well as on most Bangladesh aquifer sediments, indicates that the perception that arsenic, phosphate and other species compete for the same surface sites of iron oxides in sediments with properties similar to those of, for example a synthetic goethite, probably is not correct. A simple two-component Langmuir adsorption model was constructed to quantitatively describe the reactive transport of As(III) and PO4 in the aquifer. PMID:27867209

Mineralogical transformations controlling acid mine drainage chemistry

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

Peretyazhko, Tetyana; Zachara, John M.; Boily, Jean F.

2009-05-30

The role of Fe(III) minerals in controlling acid mine drainage (AMD) chemistry was studied using samples from two AMD sites [Gum Boot (GB) and Fridays-2 (FR)] located in northern Pennsylvania. Chemical extractions, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) were used to identify and characterize Fe(III) phases. The mineralogical analysis revealed that schwertmannite and goethite were the principal Fe(III) phases in the sediments. Schwertmannite transformation occurred at the GB site where poorly-crystallized goethite rich in surface-bound sulfate was initially formed. In contrast, no schwertmannite transformation occurred at the FR site. The goethite in GBmore » sediments had spherical morphology due to preservation of schwertmannite structure by adsorbed sulfate. Results of chemical extractions showed that poorly-crystallized goethite was subject to further crystallization accompanied by sulfate desorption. Changes in sulfate speciation preceded its desorption, with a conversion of bidentate- to monodentate-bound sulfate surface complexes. Laboratory sediment incubation experiments were conducted to evaluate the effect of mineral transformation on water chemistry. Incubation experiments were carried out with schwertmannite-containing sediments and AMD waters with different pH and chemical composition. The pH decreased to 1.9-2.2 in all suspensions and the concentrations of dissolved Fe and S increased significantly. Regardless of differences in the initial water composition, pH, Fe and S were similar in suspensions of the same sediment. XRD measurements revealed that schwertmannite transformed into goethite in GB and FR sediments during laboratory incubation. The incubation experiment demonstrated that schwertmannite transformation controlled AMD water chemistry during “closed system” laboratory contact.« less

Enhancement of sediment phosphorus release during a tunnel construction across an urban lake (Lake Donghu, China).

PubMed

Wang, Siyang; Li, Hui; Xiao, Jian; Zhou, Yiyong; Song, Chunlei; Bi, Yonghong; Cao, Xiuyun

2016-09-01

Tunnel construction in watershed area of urban lakes would accelerate eutrophication by inputting nutrients into them, while mechanisms underlying the internal phosphorus cycling as affected by construction events are scarcely studied. Focusing on two main pathways of phosphorus releasing from sediment (enzymatic mineralization and anaerobic desorption), spatial and temporal variations in phosphorus fractionation, and activities of extracellular enzymes (alkaline phosphatase, β-1,4-glucosidase, leucine aminopeptidase, dehydrogenase, lipase) in sediment were examined, together with relevant parameters in interstitial and surface waters in a Chinese urban lake (Lake Donghu) where a subaqueous tunnel was constructed across it from October 2013 to July 2014. Higher alkaline phosphatase activity (APA) indicated phosphorus deficiency for phytoplankton, as illustrated by a significantly negative relationship between APA and concentration of dissolved total phosphorus (DTP). Noticeably, in the construction area, APAs in both sediment and surface water were significantly lower than those in other relevant basins, suggesting a phosphorus supply from some sources in this area. In parallel, its sediment gave the significantly lower iron-bound phosphorus (Fe(OOH)∼P) content, coupled with significantly higher ratio of iron (II) to total iron content (Fe(2+)/TFe) and dehydrogenase activities (DHA). Contrastingly, difference in the activities of sediment hydrolases was not significant between the construction area and other basins studied. Thus, in the construction area, subsidy of bioavailable phosphorus from sediment to surface water was attributable to the anaerobic desorption of Fe(OOH)∼P rather than enzymatic mineralization. Finally, there existed a significantly positive relationship between chlorophyll a concentration in surface water and Fe(OOH)∼P content in sediment. In short, construction activities within lakes may interrupt cycling patterns of phosphorus across sediment-water interface by enhancing release of redox-sensitive phosphate, and thereby facilitating phytoplankton growth in water column.

Typha latifolia (broadleaf cattail) as bioindicator of different types of pollution in aquatic ecosystems-application of self-organizing feature map (neural network).

PubMed

Klink, Agnieszka; Polechońska, Ludmiła; Cegłowska, Aurelia; Stankiewicz, Andrzej

2016-07-01

The contents of Cd, Cu, Fe, Mn, Ni, Pb, and Zn in leaves of Typha latifolia (broadleaf cattail), water and bottom sediment from 72 study sites designated in different regions of Poland were determined using atomic absorption spectrometry. The aim of the study was to evaluate potential use of T. latifolia in biomonitoring of trace metal pollution. The self-organizing feature map (SOFM) identifying groups of sampling sites with similar concentrations of metals in cattail leaves was able to classify study sites according to similar use and potential sources of pollution. Maps prepared for water and bottom sediment showed corresponding groups of sampling sites which suggested similarity of samples features. High concentrations of Fe, Cd, Cu, and Ni were characteristic for industrial areas. Elevated Pb concentrations were noted in regions with intensive vehicle traffic, while high Mn and Zn contents were reported in leaves from the agricultural area. Manganese content in leaves of T. latifolia was high irrespectively of the concentrations in bottom sediments and water so cattail can be considered the leaf accumulator of Mn. Once trained, SOFMs can be applied in ecological investigations and could form a future basis for recognizing the type of pollution in aquatic environments by analyzing the concentrations of elements in T. latifolia.

Solid-phase arsenic speciation in aquifer sediments: A micro-X-ray absorption spectroscopy approach for quantifying trace-level speciation

DOE PAGES

Nicholas, Sarah L.; Erickson, Melinda L.; Woodruff, Laurel G.; ...

2017-05-19

Arsenic (As) is a geogenic contaminant affecting groundwater in geologically diverse systems globally. Arsenic release from aquifer sediments to groundwater is favored when biogeochemical conditions, especially oxidation-reduction (redox) potential, in aquifers fluctuate. The specific objective of this research is to identify the solid-phase sources and geochemical mechanisms of release of As in aquifers of the Des Moines Lobe glacial advance. The overarching concept is that conditions present at the aquifer-aquitard interfaces promote a suite of geochemical reactions leading to mineral alteration and release of As to groundwater. A microprobe X-ray absorption spectroscopy (μXAS) approach is developed and applied to rotosonicmore » drill core samples to identify the solid-phase speciation of As in aquifer, aquitard, and aquifer-aquitard interface sediments. This approach addresses the low solid-phase As concentrations, as well as the fine-scale physical and chemical heterogeneity of the sediments. The spectroscopy data are analyzed using novel cosine-distance and correlation-distance hierarchical clustering for Fe 1s and As 1s μXAS datasets. The solid-phase Fe and As speciation is then interpreted using sediment and well-water chemical data to propose solid-phase As reservoirs and release mechanisms. The results confirm that in two of the three locations studied, the glacial sediment forming the aquitard is the source of As to the aquifer sediments. The results are consistent with three different As release mechanisms: (1) desorption from Fe (oxyhydr)oxides, (2) reductive dissolution of Fe (oxyhydr)oxides, and (3) oxidative dissolution of Fe sulfides. The findings confirm that glacial sediments at the interface between aquifer and aquitard are geochemically active zones for As. The diversity of As release mechanisms is consistent with the geographic heterogeneity seen in the distribution of elevated-As wells.« less

Solid-phase arsenic speciation in aquifer sediments: A micro-X-ray absorption spectroscopy approach for quantifying trace-level speciation

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

Nicholas, Sarah L.; Erickson, Melinda L.; Woodruff, Laurel G.

Arsenic (As) is a geogenic contaminant affecting groundwater in geologically diverse systems globally. Arsenic release from aquifer sediments to groundwater is favored when biogeochemical conditions, especially oxidation-reduction (redox) potential, in aquifers fluctuate. The specific objective of this research is to identify the solid-phase sources and geochemical mechanisms of release of As in aquifers of the Des Moines Lobe glacial advance. The overarching concept is that conditions present at the aquifer-aquitard interfaces promote a suite of geochemical reactions leading to mineral alteration and release of As to groundwater. A microprobe X-ray absorption spectroscopy (μXAS) approach is developed and applied to rotosonicmore » drill core samples to identify the solid-phase speciation of As in aquifer, aquitard, and aquifer-aquitard interface sediments. This approach addresses the low solid-phase As concentrations, as well as the fine-scale physical and chemical heterogeneity of the sediments. The spectroscopy data are analyzed using novel cosine-distance and correlation-distance hierarchical clustering for Fe 1s and As 1s μXAS datasets. The solid-phase Fe and As speciation is then interpreted using sediment and well-water chemical data to propose solid-phase As reservoirs and release mechanisms. The results confirm that in two of the three locations studied, the glacial sediment forming the aquitard is the source of As to the aquifer sediments. The results are consistent with three different As release mechanisms: (1) desorption from Fe (oxyhydr)oxides, (2) reductive dissolution of Fe (oxyhydr)oxides, and (3) oxidative dissolution of Fe sulfides. The findings confirm that glacial sediments at the interface between aquifer and aquitard are geochemically active zones for As. The diversity of As release mechanisms is consistent with the geographic heterogeneity seen in the distribution of elevated-As wells.« less

Factors affecting the partitioning of Cu, Zn and Pb in boulder coatings and stream sediments in the vicinity of a polymetallic sulfide deposit

USGS Publications Warehouse

Filipek, L.H.; Chao, T.T.; Carpenter, R.H.

1981-01-01

A sequential extraction scheme is utilized to determine the geochemical partitioning of Cu, Zn and Pb among hydrous Mn- and Fe-oxides, organics and residual crystalline silicates and oxides in the minus-80-mesh ( Fe-oxides > Mn-oxides; Zn, Mn-oxides {reversed tilde equals} organics > Fe-oxides; Pb, Fe-oxides > organics > Mn-oxides. In the sediments, organics are the most efficient scavengers of all three ore metals. These results emphasize the importance of organics as sinks for the ore metals, even in environments with high concentrations of Mn- and Fe-oxides. Of the ore metals, Zn appears to be the most mobile, and is partitioned most strongly into the coatings. However, anomaly contrast for hydromorphic Zn, normalized to the MnFe-oxide or organic content, is similar in sediments and coatings. Cu shows the highest anomaly on the boulder coatings, probably due to precipitation of a secondary Cu mineral. In contrast, detrital Pb in the pan concentrates shows a better anomaly than any hydromorphic Pb component. ?? 1981.

Accumulation by fish of contaminants released from dredged sediments

USGS Publications Warehouse

Seelye, James G.; Hesselberg, Robert J.; Mac, Michael J.

1982-01-01

Inasmuch as the process of dredging and disposing of dredged materials causes a resuspension of these materials and an increase in bioavailability of associated contaminants, we conducted a series of experiments to examine the potential accumulation by fish of contaminants from suspended sediments. In the first experiment we compared accumulation of contaminants by yellow perch of hatchery and lake origin and found that after 10 days of exposure to nonaerated sediments, fish of hatchery origin accumulated PCBs and Fe, while fish of lake origin accumulated As, Cr, Fe, and Na. Two additional exposures were conducted to evaluate the effects of aerating the sediments prior to measuring bioavailability of associated contaminants. Fish of hatchery origin exposed to nonaerated sediments for 10 days accumulated PCBs and Hg, while fish of hatchery origin exposed to aerated sediments for 10 days accumulated PCBs, DDE, Zn, Fe, Cs, and Se. These results demonstrated not only the potential for uptake of contaminants by fish as a result of dredging but also the potential utility of fish bioassays in evaluating proposed dredging operations.

Pathways of organic carbon oxidation in three continental margin sediments

NASA Technical Reports Server (NTRS)

Canfield, D. E.; Jorgensen, B. B.; Fossing, H.; Glud, R.; Gundersen, J.; Ramsing, N. B.; Thamdrup, B.; Hansen, J. W.; Nielsen, L. P.; Hall, P. O.

1993-01-01

We have combined several different methodologies to quantify rates of organic carbon mineralization by the various electron acceptors in sediments from the coast of Denmark and Norway. Rates of NH4+ and Sigma CO2 liberation sediment incubations were used with O2 penetration depths to conclude that O2 respiration accounted for only between 3.6-17.4% of the total organic carbon oxidation. Dentrification was limited to a narrow zone just below the depth of O2 penetration, and was not a major carbon oxidation pathway. The processes of Fe reduction, Mn reduction and sulfate reduction dominated organic carbon mineralization, but their relative significance varied depending on the sediment. Where high concentrations of Mn-oxide were found (3-4 wt% Mn), only Mn reduction occurred. With lower Mn oxide concentrations more typical of coastal sediments, Fe reduction and sulfate reduction were most important and of a similar magnitude. Overall, most of the measured O2 flux into the sediment was used to oxidized reduced inorganic species and not organic carbon. We suspect that the importance of O2 respiration in many coastal sediments has been overestimated, whereas metal oxide reduction (both Fe and Mn reduction) has probably been well underestimated.

Contaminants in surface water and sediments near the Tynagh silver mine site, County Galway, Ireland.

PubMed

O'Neill, A; Phillips, D H; Bowen, J; Sen Gupta, B

2015-04-15

A former silver mine in Tynagh, Co. Galway, Ireland is one of the most contaminated mine sites in Europe with maximum concentrations of Zn, As, Pb, Mn, Ni, Cu, and Cd far exceeding guideline values for water and sediment. The aims of this research were to 1) further assess the contamination, particularly metals, in surface water and sediment around the site, and 2) determine if the contamination has increased 10 years after the Environmental Protection Agency Ireland (EPAI) identified off-site contamination. Site pH is alkaline to neutral because CaCO3-rich sediment and rock material buffer the exposed acid generating sulphide-rich ore. When this study was compared to the previous EPAI study conducted 10 years earlier, it appeared that further weathering of exposed surface sediment had increased concentrations of As and other potentially toxic elements. Water samples from the tailings ponds and adjacent Barnacullia Stream had concentrations of Al, Cd, Mn, Zn and Pb above guideline values. Lead and Zn concentrations from the tailings pond sediment were 16 and 5 times higher, respectively, than concentrations reported 10 years earlier. Pb and Zn levels in most sediment samples exceeded the Expert Group (EGS) guidelines of 1000 and 5000 mg/kg, respectively. Arsenic concentrations were as high as 6238 mg/kg in the tailings ponds sediment, which is 62 and 862 times greater than the EGS and Canadian Soil Quality Guidelines (CSQG), respectively. Cadmium, Cu, Fe, Mn, Pb and Zn concentrations in water and sediment were above guideline values downstream of the site. Additionally, Fe, Mn and organic matter (OM) were strongly correlated and correlated to Zn, Pb, As, Cd, Cu and Ni in stream sediment. Therefore, the nearby Barnacullia Stream is also a significant pathway for contaminant transport to downstream areas. Further rehabilitation of the site may decrease the contamination around the area. Copyright © 2015 Elsevier B.V. All rights reserved.

Pathways of coupled arsenic and iron cycling in high arsenic groundwater of the Hetao basin, Inner Mongolia, China: an iron isotope approach

USGS Publications Warehouse

Guo, Huaming; Liu, Chen; Lu, Hai; Wanty, Richard B.; Wang, Jun; Zhou, Yinzhu

2013-01-01

High As groundwater is widely distributed all over the world, which has posed a significant health impact on millions of people. Iron isotopes have recently been used to characterize Fe cycling in aqueous environments, but there is no information on Fe isotope characteristics in the groundwater. Since groundwater As behavior is closely associated with Fe cycling in the aquifers, Fe isotope signatures may help to characterize geochemical processes controlling As concentrations of shallow groundwaters. This study provides the first observation of Fe isotope fractionation in high As groundwater and evaluation of Fe cycling and As behaviors in shallow aquifers in terms of Fe isotope signatures. Thirty groundwater samples were taken for chemical and isotopic analysis in the Hetao basin, Inner Mongolia. Thirty-two sediments were sampled as well from shallow aquifers for Fe isotope analysis. Results showed that groundwater was normally enriched in isotopically light Fe with δ56Fe values between −3.40‰ and 0.58‰ and median of −1.14‰, while heavier δ56Fe values were observed in the sediments (between −1.10‰ and 0.75‰, median +0.36‰). In reducing conditions, groundwaters generally had higher δ56Fe values, in comparison with oxic conditions. High As groundwaters, generally occurring in reducing conditions, had high δ56Fe values, while low As groundwaters normally had low δ56Fe values. Although sediment δ56Fe values were generally independent of lithological conditions, a large variation in sediment δ56Fe values was observed in the oxidation–reduction transition zone. Three pathways were identified for Fe cycling in shallow groundwater, including dissimilatory reduction of Fe(III) oxides, re-adsorption of Fe(II), and precipitation of pyrite and siderite. Dissimilatory reduction of Fe(III) oxides resulted in light δ56Fe values (around −1.0‰) and high As concentration (>50 μg/L) in groundwater in anoxic conditions. Re-adsorption of isotopically heavy Fe(II) produced by microbially mediated reduction of Fe(III) oxides led to further enrichment of isotopically light Fe in groundwater (up to −3.4‰ of δ56Fe) in anoxic–suboxic conditions. Arsenic re-adsorption was expected to occur along with Fe(II) re-adsorption, decreasing groundwater As concentrations. In strongly reducing conditions, precipitation of isotopically light Fe-pyrite and/or siderite increased groundwater δ56Fe values, reaching +0.58‰ δ56Fe, with a subsequent decrease in As concentrations via co-precipitation. The mixed effect of those pathways would regulate As and Fe cycling in most groundwaters.

A baseline study on the concentration of trace elements in the surface sediments off Southwest coast of Tamil Nadu, India.

PubMed

Godson, Prince S; Magesh, N S; Peter, T Simon; Chandrasekar, N; Krishnakumar, S; Vincent, Salom Gnana Thanga

2018-01-01

Forty two surface sediment samples were collected in order to document baseline elemental concentration along the Southwest coast of Tamil Nadu, India. The elements detected were Manganese (Mn), Zinc (Zn), Iron (Fe), Copper (Cu), Nickel (Ni) and Lead (Pb). The concentration of Fe and Mn was primarily controlled by the riverine input. The source of Pb and Zn is attributed to leaded petrol and anti-biofouling paints. The calculated index (EF, Igeo and CF) suggests that the sediments of the study area are significantly enriched with all elements except Pb. The contamination factor showed the order of Mn>Zn>Fe>Cu>Ni>Pb. The sediment pollution index (SPI) revealed that the sediments belonged to low polluted to dangerous category. The correlation matrix and dendrogram showed that the elemental distribution was chiefly controlled by riverine input as well as anthropogenic activity in the coast. Copyright © 2017 Elsevier Ltd. All rights reserved.

Mechanism of molybdenum removal from the sea and its concentration in black shales: EXAFS evidence

USGS Publications Warehouse

Helz, G.R.; Miller, C.V.; Charnock, J.M.; Mosselmans, J.F.W.; Pattrick, R.A.D.; Garner, C.D.; Vaughan, D.J.

1996-01-01

Molybdenum K-edge EXAFS (extended X-ray absorption fine structure) spectra yield new structural information about the chemical environment of Mo in high-Mo black shales and sediments. Two spectral types are found. The less common one, associated with Mo ores developed in shale in China, is that of a MoS2 phase, possibly X-ray amorphous jordisite. The other, associated with Cretaceous deep sea sediments and with other black shales, is characterized by short Mo-O distances (1.69-1.71 A??), by Mo-S distances of 2.30-2.38 A??, and in some cases by second shell Mo and Fe interactions, which suggests that some Mo resides in transition metal-rich phases. EXAFS spectra of synthetic amorphous materials, prepared by scavenging Mo from HS solutions with Fe(II), FeOOH, and humic acid, suggest that the second spectral type arises from Mo present chiefly in two forms. One is a compact, Mo-Fe-S "cubane" type compound with Mo-S distances of ???2.36 A?? and Mo-Fe distances of ???2.66 A??, while the other is probably an organic form containing some Mo-O double bonds (???1.69 A??). Laboratory products, that were prepared by scavenging dissolved Mo from sulfidic solutions with humic acid, yield spectra quite similar to the second spectral type observed in shales and sediments, including unexpected indications of Mo-Fe interactions. Molybdenum L-edge spectra indicate that the mean oxidation state in the sediments and shales lies between IV and VI. This work demonstrates the merit of EXAFS for obtaining structural information on natural materials containing X-ray amorphous components which defeat conventional mineralogical characterization. The implications of these findings regarding Mo scavenging from sulfidic natural waters are considered. We introduce the concept of a geochemical switch, in which HS- transforms the marine behavior of Mo from that of a conservative element to that of a particle reactive element. The action point of the HS- switch is calculated to be, aHS- = 10-3.6 - 10-4.3. When aHS- approaches the action point, Mo becomes reactive to particles containing transition metals (e.g., Fe). We conjecture that thiols, including humic-bound thiol groups, also switch Mo behavior. In contrast to previous ideas, our model for Mo scavenging deemphasizes the role of reduction from Mo(VI) to Mo(V) as the initial step in scavenging; instead, we emphasize the ease with which Mo forms covalent bonds to transition metals and organic molecules via S bridges.

Fe(III) reduction and U(VI) immobilization by Paenibacillus sp. strain 300A, isolated from Hanford 300A subsurface sediments.

PubMed

Ahmed, Bulbul; Cao, Bin; McLean, Jeffrey S; Ica, Tuba; Dohnalkova, Alice; Istanbullu, Ozlem; Paksoy, Akin; Fredrickson, Jim K; Beyenal, Haluk

2012-11-01

A facultative iron-reducing [Fe(III)-reducing] Paenibacillus sp. strain was isolated from Hanford 300A subsurface sediment biofilms that was capable of reducing soluble Fe(III) complexes [Fe(III)-nitrilotriacetic acid and Fe(III)-citrate] but unable to reduce poorly crystalline ferrihydrite (Fh). However, Paenibacillus sp. 300A was capable of reducing Fh in the presence of low concentrations (2 μM) of either of the electron transfer mediators (ETMs) flavin mononucleotide (FMN) or anthraquinone-2,6-disulfonate (AQDS). Maximum initial Fh reduction rates were observed at catalytic concentrations (<10 μM) of either FMN or AQDS. Higher FMN concentrations inhibited Fh reduction, while increased AQDS concentrations did not. We also found that Paenibacillus sp. 300A could reduce Fh in the presence of natural ETMs from Hanford 300A subsurface sediments. In the absence of ETMs, Paenibacillus sp. 300A was capable of immobilizing U(VI) through both reduction and adsorption. The relative contributions of adsorption and microbial reduction to U(VI) removal from the aqueous phase were ∼7:3 in PIPES [piperazine-N,N'-bis(2-ethanesulfonic acid)] and ∼1:4 in bicarbonate buffer. Our study demonstrated that Paenibacillus sp. 300A catalyzes Fe(III) reduction and U(VI) immobilization and that these reactions benefit from externally added or naturally existing ETMs in 300A subsurface sediments.

Fe(III) Reduction and U(VI) Immobilization by Paenibacillus sp. Strain 300A, Isolated from Hanford 300A Subsurface Sediments

PubMed Central

Ahmed, Bulbul; Cao, Bin; McLean, Jeffrey S.; Ica, Tuba; Dohnalkova, Alice; Istanbullu, Ozlem; Paksoy, Akin; Fredrickson, Jim K.

2012-01-01

A facultative iron-reducing [Fe(III)-reducing] Paenibacillus sp. strain was isolated from Hanford 300A subsurface sediment biofilms that was capable of reducing soluble Fe(III) complexes [Fe(III)-nitrilotriacetic acid and Fe(III)-citrate] but unable to reduce poorly crystalline ferrihydrite (Fh). However, Paenibacillus sp. 300A was capable of reducing Fh in the presence of low concentrations (2 μM) of either of the electron transfer mediators (ETMs) flavin mononucleotide (FMN) or anthraquinone-2,6-disulfonate (AQDS). Maximum initial Fh reduction rates were observed at catalytic concentrations (<10 μM) of either FMN or AQDS. Higher FMN concentrations inhibited Fh reduction, while increased AQDS concentrations did not. We also found that Paenibacillus sp. 300A could reduce Fh in the presence of natural ETMs from Hanford 300A subsurface sediments. In the absence of ETMs, Paenibacillus sp. 300A was capable of immobilizing U(VI) through both reduction and adsorption. The relative contributions of adsorption and microbial reduction to U(VI) removal from the aqueous phase were ∼7:3 in PIPES [piperazine-N,N′-bis(2-ethanesulfonic acid)] and ∼1:4 in bicarbonate buffer. Our study demonstrated that Paenibacillus sp. 300A catalyzes Fe(III) reduction and U(VI) immobilization and that these reactions benefit from externally added or naturally existing ETMs in 300A subsurface sediments. PMID:22961903

Fe(III) Reduction and U(VI) Immobilization by Paenibacillus sp. Strain 300A, Isolated from Hanford 300A Subsurface Sediments

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

Ahmed, B.; Cao, B.; McLean, Jeffrey S.

2012-11-07

A facultative iron-reducing (Fe(III)-reducing) Paenibacillus sp. strain was isolated from Hanford 300A subsurface sediment biofilms that was capable of reducing soluble Fe(III) complexes (Fe(III)-NTA and Fe(III)-citrate) but unable to reduce poorly crystalline ferrihydrite (Fh). However, Paenibacillus sp. 300A was capable of reducing Fh in the presence of low concentrations (2 µM) of either of electron transfer mediators (ETMs) flavin mononucleotide (FMN) or anthraquinone-2,6-disulfonate (AQDS). Maximum initial Fh reduction rates were observed at catalytic concentrations (<10 µM) of either FMN or AQDS. Higher FMN concentrations inhibited Fh reduction, while increased AQDS concentrations did not. We found that Paenibacillus sp. 300A alsomore » could reduce Fh in the presence of natural ETMs from Hanford 300A subsurface sediments. In the absence of ETMs, Paenibacillus sp. 300A was capable of immobilizing U(VI) through both reduction and adsorption. The relative contributions of adsorption and microbial reduction to U(VI) removal from the aqueous phase were ~7:3 in PIPES and ~1:4 in bicarbonate buffer. Our study demonstrated that Paenibacillus sp. 300A catalyzes Fe(III) reduction and U(VI) immobilization and that these reactions benefit from externally added or naturally existing ETMs in 300A subsurface sediments.« less

A field, laboratory and modeling study of reactive transport of groundwater arsenic in a coastal aquifer

PubMed Central

Jung, Hun Bok; Charette, Matthew A.; Zheng, Yan

2009-01-01

A field, laboratory, and modeling study of As in groundwater discharging to Waquoit Bay, MA, shed light on coupled control of chemistry and hydrology on reactive transport of As in a coastal aquifer. Dissolved Fe(II) and As(III) in a reducing groundwater plume bracketed by an upper and a lower redox interface are oxidized as water flows towards the bay. This results in precipitation of Fe(III) oxides, along with oxidation and adsorption of As to sediment at the redox interfaces where concentrations of sedimentary HCl-leachable Fe (80~90% Fe(III)) are 734±232 mg kg-1, sedimentary phosphate extractable As (90~100% As(V)) are 316±111 μg kg-1, and are linearly correlated. Batch adsorption of As(III) onto orange, brown and gray sediments follows Langmuir isotherms, and can be fitted by a surface complexation model (SCM) assuming a diffuse layer for ferrihydrite. The sorption capacity and distribution coefficient for As increase with decreasing sediment Fe(II)/Fe. To allow accumulation of the amount of sediment As, similar hydrogeochemical conditions would have been operating for thousands of years at Waquoit Bay. The SCM simulated the observed dissolved As concentration better than a parametric approach based on Kd. Site specific isotherms should be established for Kd or SCM based models. PMID:19708362

Distribution of metal concentrations in sediments of the coastal zone of the Gulf of Riga and open part of the Baltic Sea

NASA Astrophysics Data System (ADS)

Seisuma, Z.; Kulikova, I.

2012-11-01

The comparison of spatial and temporal distribution of Hg, Cd, Pb, Cu, Ni, Zn, Mn and Fe concentrations in sediments from the Gulf of Riga and open Baltic Sea along the coastal zone is presented for the first time. There were considerable differences in Pb, Zn, Mn and Fe levels in sediment at various stations of the Gulf of Riga. A significant difference of Cd, Pb, Cu, Ni, Zn levels was found in sediments of various stations in the open Baltic coast. The amount of Cd, Pb, Cu, Ni, Zn and Fe levels also differed significantly in the sediments of the Gulf of Riga in different years. A considerable yearly difference in amount of Hg, Cd, Pb, Cu, Ni and Mn levels was found in sediments in the open Baltic coast. The essential highest values of Pb and Zn in coastal sediments of the open Baltic Sea are stated in comparison with the Gulf of Riga. The concentrations of other metals have only a tendency to be higher in coastal sediments of the open Baltic Sea in comparison with the Gulf of Riga. Natural and anthropogenic factors were proved to play an important role in determining resultant metals concentrations in the regions.

Mechanisms of Arsenic Mobilization and Attenuation in Subsurface Sediments

NASA Astrophysics Data System (ADS)

O'Day, P. A.; Illera, V.; Root, R.; Choi, S.; Vlassopoulos, D.

2007-12-01

This talk will review molecular mechanisms of As mobilization and attenuation in subsurface sediments using examples from recent field studies that represent a range in oxidation-redox (redox) potential. As a ubiquitous trace element in sediments, As speciation and fate is linked to the abundance and biogeochemical behavior of the generally more abundant redox-active elements Fe, S, and Mn. All four elements are subject to oxidation, reduction, and pH-dependent processes such as sorption, desorption, precipitation, and dissolution, and which may include both biotic and abiotic reaction steps. We have used spectroscopic interrogation and geochemical modeling to characterize As speciation in subsurface sediments in several contrasting environments, including high and low S and Fe settings. Aquifers most at risk for contamination by As include those that are rich in organic matter and nutrients, stimulating high rates of microbial reduction and creating anoxic conditions, but limited in labile or available S and/or Fe that remove As by precipitation or adsorption. In subsurface sediments with low labile S and Fe, laboratory experiments and spectroscopic studies suggest that sediment Mn minerals are important in the oxidation of sorbed As(III) to As(V), but that they have a limited oxidation capacity. Arsenic attenuation and mobilization in the subsurface are affected by seasonal variations when hydraulic conditions are influenced by surface infiltration, which may induce transitions from oxidized to reduced conditions (or vice versa) in porewater.

Enzymatic iron and uranium reduction by sulfate-reducing bacteria

USGS Publications Warehouse

Lovley, D.R.; Roden, E.E.; Phillips, E.J.P.; Woodward, J.C.

1993-01-01

The potential for sulfate-reducing bacteria (SRB) to enzymatically reduce Fe(III) and U(VI) was investigated. Five species of Desulfovibrio as well as Desulfobacterium autotrophicum and Desulfobulbus propionicus reduced Fe(III) chelated with nitrilotriacetic acid as well as insoluble Fe(III) oxide. Fe(III) oxide reduction resulted in the accumulation of magnetite and siderite. Desulfobacter postgatei reduced the chelated Fe(III) but not Fe(III) oxide. Desulfobacter curvatus, Desulfomonile tiedjei, and Desulfotomaculum acetoxidans did not reduce Fe(III). Only Desulfovibrio species reduced U(VI). U(VI) reduction resulted in the precipitation of uraninite. None of the SRB that reduced Fe(III) or U(VI) appeared to conserve enough energy to support growth from this reaction. However, Desulfovibrio desulfuricans metabolized H2 down to lower concentrations with Fe(III) or U(VI) as the electron acceptor than with sulfate, suggesting that these metals may be preferred electron acceptors at the low H2 concentrations present in most marine sediments. Molybdate did not inhibit Fe(III) reduction by D. desulfuricans. This indicates that the inability of molybdate to inhibit Fe(III) reduction in marine sediments does not rule out the possibility that SRB are important catalysts for Fe(III) reduction. The results demonstrate that although SRB were previously considered to reduce Fe(III) and U(VI) indirectly through the production of sulfide, they may also directly reduce Fe(III) and U(VI) through enzymatic mechanisms. These findings, as well as our recent discovery that the So-reducing microorganism Desulfuromonas acetoxidans can reduce Fe(III), demonstrate that there are close links between the microbial sulfur, iron, and uranium cycles in anaerobic marine sediments. ?? 1993.

Paleoenvironmental implications of early diagenetic siderites of the Paraíba do Sul Deltaic Complex, eastern Brazil

NASA Astrophysics Data System (ADS)

Rodrigues, Amanda Goulart; De Ros, Luiz Fernando; Neumann, Reiner; Borghi, Leonardo

2015-06-01

Abundant early diagenetic siderites occur as spherulites and rhombohedral microcrystalline and macrocrystalline crystals in the cores of the 2-MU-1-RJ well, drilled in the Paraíba do Sul Deltaic Complex, Rio de Janeiro (Brazil). The host sediments of the siderites are siliciclastic, hybrid, and carbonate deposits. Intense pedogenetic processes affected the siliciclastic sediments immediately after deposition, comprising clay illuviation, plants bioturbation, feldspar dissolution, and iron oxide/hydroxide precipitation. Siderite and pyrite are the main diagenetic constituents. The other diagenetic products are kaolinite, smectite, argillaceous and carbonate pseudomatrix, quartz overgrowths, diagenetic titanium minerals, jarosite, and iron oxides/hydroxides. Early diagenetic siderites were separated into four groups based on their elemental and stable isotopic composition, as well as on their paragenetic relationships with the other constituents and with the host sediments. Spherulitic to macrocrystalline siderites from group 1 are almost pure (average: 94.7 mol% FeCO3; 1.2 mol% MgCO3; 2.3 mol% CaCO3; 1.8 mol% MnCO3) and precipitated from meteoric porewaters in continental siliciclastic rocks under suboxic conditions (δ18Ovpdb values range in - 10.28 to - 5.57‰ and the δ13Cvpdb values in - 12.68 to - 4.33‰). Microcrystalline rhombohedral siderites from group 2 have zonation due to substantial Ca and Mg substitution (core average: 78.5 mol% FeCO3; 4.2 mol% MgCO3; 15.7 mol% CaCO3; 1.6 mol% MnCO3; edge average: 74.0 mol% FeCO3; 9.2 mol% MgCO3; 15.6 mol% CaCO3; 1.1 mol% MnCO3), and δ13Cvpdb and δ18Ovpdb values of + 0.17‰ and - 1.96‰, precipitated from marine porewaters in packstones/wackestones under methanogenic conditions. The group 3 is represented by irregular spherulitic siderites with moderate Ca and Mg substitutions (average: 80.2 mol% FeCO3; 7.9 mol% MgCO3; 11.3 mol% CaCO3; 0.6 mol% MnCO3), with δ18Ovpdb values ranging from - 5.96 to - 7.61‰ and δ13Cvpdb values ranging from - 5.15 to - 10.41‰. The group 4 microcrystalline siderites are magnesium-rich (average: 57.3 mol% FeCO3; 31.4 mol% MgCO3; 9.6 mol% CaCO3; 1.7 mol% MnCO3; δ13Cvpdb + 1.43‰ and δ18Ovpdb - 14.09‰). The group 3 and 4 siderites were formed from brackish porewater under suboxic conditions in hybrid and siliciclastic rocks. These variations in siderites are probably related to the Paraíba do Sul River dynamics, to sea level changes and to climatic variations that took place during the Quaternary.

Microbially catalyzed nitrate-dependent metal/radionuclide oxidation in shallow subsurface sediments

NASA Astrophysics Data System (ADS)

Weber, K.; Healy, O.; Spanbauer, T. L.; Snow, D. D.

2011-12-01

Anaerobic, microbially catalyzed nitrate-dependent metal/radionuclide oxidation has been demonstrated in a variety of sediments, soils, and groundwater. To date, studies evaluating U bio-oxidation and mobilization have primarily focused on anthropogenically U contaminated sites. In the Platte River Basin U originating from weathering of uranium-rich igneous rocks in the Rocky Mountains was deposited in shallow alluvial sediments as insoluble reduced uranium minerals. These reduced U minerals are subject to reoxidation by available oxidants, such nitrate, in situ. Soluble uranium (U) from natural sources is a recognized contaminant in public water supplies throughout the state of Nebraska and Colorado. Here we evaluate the potential of anaerobic, nitrate-dependent microbially catalyzed metal/radionuclide oxidation in subsurface sediments near Alda, NE. Subsurface sediments and groundwater (20-64ft.) were collected from a shallow aquifer containing nitrate (from fertilizer) and natural iron and uranium. The reduction potential revealed a reduced environment and was confirmed by the presence of Fe(II) and U(IV) in sediments. Although sediments were reduced, nitrate persisted in the groundwater. Nitrate concentrations decreased, 38 mg/L to 30 mg/L, with increasing concentrations of Fe(II) and U(IV). Dissolved U, primarily as U(VI), increased with depth, 30.3 μg/L to 302 μg/L. Analysis of sequentially extracted U(VI) and U(IV) revealed that virtually all U in sediments existed as U(IV). The presence of U(IV) is consistent with reduced Fe (Fe(II)) and low reduction potential. The increase in aqueous U concentrations with depth suggests active U cycling may occur at this site. Tetravalent U (U(IV)) phases are stable in reduced environments, however the input of an oxidant such as oxygen or nitrate into these systems would result in oxidation. Thus co-occurrence of nitrate suggests that nitrate could be used by bacteria as a U(IV) oxidant. Most probable number enumeration of nitrate-dependent U(IV) oxidizing microorganisms demonstrated an abundant community ranging from 1.61x104 to 2.74x104 cells g-1 sediment. Enrichments initiated verified microbial U reduction and U oxidation coupled to nitrate reduction. Sediment slurries were serially diluted and incubated over a period of eight weeks and compared to uninoculated controls. Oxidation (0-4,554 μg/L) and reduction (0-55 μg/L) of U exceeded uninoculated controls further providing evidence of a U biogeochemical cycling in these subsurface sediments. The oxidation of U(IV) could contribute to U mobilization in the groundwater and result in decreased water quality. Not only could nitrate serve as an oxidant, but Fe(III) could also contribute to U mobilization. Nitrate-dependent Fe(II) oxidation is an environmentally ubiquitous process facilitated by a diversity of microorganisms. Additional research is necessary in order to establish a role of biogenic Fe(III) oxides in U geochemical cycling at this site. These microbially mediated processes could also have a confounding effect on uranium mobility in subsurface environments.

Formation of carbonate pipes in the northern Okinawa Trough linked to strong sulfate exhaustion and iron supply

NASA Astrophysics Data System (ADS)

Peng, Xiaotong; Guo, Zixiao; Chen, Shun; Sun, Zhilei; Xu, Hengchao; Ta, Kaiwen; Zhang, Jianchao; Zhang, Lijuan; Li, Jiwei; Du, Mengran

2017-05-01

The microbial anaerobic oxidation of methane (AOM), a key biogeochemical process that consumes substantial amounts of methane produced in seafloor sediments, can lead to the formation of carbonate deposits at or beneath the sea floor. Although Fe oxide-driven AOM has been identified in cold seep sediments, the exact mode by which it may influence the formation of carbonate deposits remains poorly understood. Here, we characterize the morphology, petrology and geochemistry of a methane-derived Fe-rich carbonate pipe in the northern Okinawa Trough (OT). We detect abundant authigenic pyrites, as well as widespread trace Fe, within microbial mat-like carbonate veins in the pipe. The in situ δ34S values of these pyrites range from -3.9 to 31.6‰ (VCDT), suggesting a strong consumption of seawater sulfate by sulfate-driven AOM at the bottom of sulfate reduction zone. The positive δ56Fe values of pyrite and notable enrichment of Fe in the OT pipe concurrently indicate that the pyrites are primarily derived from Fe oxides in deep sediments. We propose that the Fe-rich carbonate pipe formed at the bottom of sulfate reduction zone, below which Fe-driven AOM, rather than Fe-oxide reduction coupled to organic matter degradation, might be responsible for the abundantly available Fe2+ in the fluids from which pyrites precipitated. The Fe-rich carbonate pipe described in this study probably represents the first fossil example of carbonate deposits linked to Fe-driven AOM. Because Fe-rich carbonate deposits have also been found at other cold seeps worldwide, we infer that similar processes may play an essential role in biogeochemical cycling of sub-seafloor methane and Fe at continental margins.

Authigenic apatite and octacalcium phosphate formation due to adsorption-precipitation switching across estuarine salinity gradients

NASA Astrophysics Data System (ADS)

Oxmann, J. F.; Schwendenmann, L.

2015-02-01

Mechanisms governing phosphorus (P) speciation in coastal sediments remain largely unknown due to the diversity of coastal environments and poor analytical specificity for P phases. We investigated P speciation across salinity gradients comprising diverse ecosystems in a P-enriched estuary. To determine P load effects on P speciation we compared the high P site with a low P site. Octacalcium phosphate (OCP), authigenic apatite (carbonate fluorapatite, CFAP) and detrital apatite (fluorapatite) were quantitated in addition to Al/Fe-bound P (Al/Fe-P) and Ca-bound P (Ca-P). Gradients in sediment pH strongly affected P fractions across ecosystems and independent of the site-specific total P status. We found a pronounced switch from adsorbed Al/Fe-P to mineral Ca-P with decreasing acidity from land to sea. This switch occurred at near-neutral sediment pH and has possibly been enhanced by redox-driven phosphate desorption from iron oxyhydroxides. The seaward decline in Al/Fe-P was counterbalanced by the precipitation of Ca-P. Correspondingly, two location-dependent accumulation mechanisms occurred at the high P site due to the switch, leading to elevated Al/Fe-P at pH < 6.6 (landward; adsorption) and elevated Ca-P at pH > 6.6 (seaward; precipitation). Enhanced Ca-P precipitation by increased P loads was also evident from disproportional accumulation of metastable Ca-P (Ca-Pmeta) at the high P site. Here, sediments contained on average 6-fold higher Ca-Pmeta levels compared with the low P site, although these sediments contained only 2-fold more total Ca-P than the low P sediments. Phosphorus species distributions indicated that these elevated Ca-Pmeta levels resulted from transformation of fertilizer-derived Al/Fe-P to OCP and CFAP in nearshore areas. Formation of CFAP as well as its precursor, OCP, results in P retention in coastal zones and can thus lead to substantial inorganic P accumulation in response to anthropogenic P input.

The role of iron-sulfides on cycling of organic carbon in the St Lawrence River system: Evidence of sulfur-promoted carbon sequestration?

NASA Astrophysics Data System (ADS)

Balind, K.; Barber, A.; Gélinas, Y.

2017-12-01

The biogeochemical cycle of sulfur is intimately linked with that of carbon, as well as with that of iron through the formation of iron-sulfur complexes. Iron-sulfide minerals such as mackinawite (FeS) and greigite (Fe3S4) form below the oxic/anoxic redox boundary in marine and lacustrine sediments and soils. Reactive iron species, abundant in surface sediments, can undergo reductive dissolution leading to the formation of soluble Fe(II) which can then precipitate in the form of iron sulfur species. While sedimentary iron-oxides have been thoroughly explored in terms of their ability to sorb and sequester organic carbon (OC) (Lalonde et al.; 2012), the role of FeS in the long-term preservation of OC remains undefined. In this study, we present depth profiles for carbon, iron, and sulfur in the aqueous-phase, along with data from sequential extractions of sulfur speciation in the solid-phase collected from sediment cores from the St Lawrence River and estuarine system, demonstrating the transition from fresh to saltwater sediments. Additionally, we present synthetic iron sulfur sorption experiments using both model and natural organic molecules in order to assess the importance of FeS in sedimentary carbon storage.

Laboratory studies of the diagenesis and mobility of 239,240pu and 137Cs in nearshore sediments

NASA Astrophysics Data System (ADS)

Sholkovitz, Edward R.; Cochran, J. Kirk; Carey, Anne E.

1983-08-01

Controlled laboratory experiments have been used to study the diagenetic chemistry of 239,240Pu 137Cs, and 55Fe. Experiments using Buzzards Bay sediments in small tanks show that sulfate reduction is accompanied by the production of large pore water concentration gradients of alkalinity, phosphate, ammonia and dissolved organic carbon and the formation of subsurface maxima in Fe and Mn. These pore water profiles demonstrate that bacterially-mediated processes of organic matter degradation and redox reactions can be simulated in the laboratory. A vertical profile of 55Fe in pore waters is reported for the first time: it follows the profile of stable Fe and as such has a large (200 dpm/100 kg) subsurface maximum between 2-4 cm depth. Comparison of 55Fe/Fe ratios in sediments and pore waters shows that there is preferential solubilization of 55Fe over stable Fe. The pore water activities of 239,240Pu show no gradients within the large uncertainties of the counting statistics, but are two to four times higher than Buzzards Bay seawater (0.05 dpm/100 kg). The activity of 137Cs in the pore water profile is constant (40 dpm/100 kg) within the large counting uncertainties and is twice that of Buzzards Bay seawater. Cs-137 does not appear to be involved in diagenetic chemistry but may increase in pore waters as a result of ion exchange reactions. Flux estimates based on the pore water data show that remobilization and transport of 239,240 Pu in coastal sediments are not significant processes while the transport of l37Cs may be.

Comparison of methods for the removal of organic carbon and extraction of chromium, iron and manganese from an estuarine sediment standard and sediment from the Calcasieu River estuary, Louisiana, U.S.A.

USGS Publications Warehouse

Simon, N.S.; Hatcher, S.A.; Demas, C.

1992-01-01

U.S. National Bureau of Standards (NBS) estuarine sediment 1646 from the Chesapeake Bay, Maryland, and surface sediment collected at two sites in the Calcasieu River estuary, Louisiana, were used to evaluate the dilute hydrochloric acid extraction of Cr, Fe and Mn from air-dried and freeze-dried samples that had been treated by one of three methods to remove organic carbon. The three methods for the oxidation and removal of organic carbon were: (1) 30% hydrogen peroxide; (2) 30% hydrogen peroxide plus 0.25 mM pyrophosphate; and (3) plasma oxidation (low-temperature ashing). There was no statistically significant difference at the 95% confidence level between air- and freeze-dried samples with respect to the percent of organic carbon removed by the three methods. Generally, there was no statistically significant difference at the 95% confidence level between air- and freeze-dried samples with respect to the concentration of Cr, Fe and Mn that was extracted, regardless of the extraction technique that was used. Hydrogen peroxide plus pyrophosphate removed the most organic carbon from sediment collected at the site in the Calcasieu River that was upstream from industrial outfalls. Plasma oxidation removed the most organic carbon from the sediment collected at a site in the Calcasieu River close to industrial outfalls and from the NBS estuarine sediment sample. Plasma oxidation merits further study as a treatment for removal of organic carbon. Operational parameters can be chosen to limit the plasma oxidation of pyrite which, unlike other Fe species, will not be dissolved by dilute hydrochloric acid. Preservation of pyrite allows the positive identification of Fe present as pyrite in sediments. ?? 1992.

Distribution and flux estimates of soluble, colloidal, and leachable particulate trace metals in dynamic and oxygen depleted Mauritanian shelf waters

NASA Astrophysics Data System (ADS)

Rapp, I.; Schlosser, C.; Gledhill, M.; Achterberg, E. P.

2016-02-01

Fe availability in surface waters determines primary production, N2 fixation and microbial community structure and thus plays an important role in ocean carbon and nitrogen cycles. Eastern boundary upwelling areas with oxygen minimum zones, such as the Mauritanian shelf region, are typically associated with elevated Fe concentrations with shelf sediments as key source of Fe to bottom and surface waters. The magnitude of vertical and horizontal Fe fluxes from shelf sediments to onshore and offshore surface waters are not well constrained and there are still large uncertainties concerning the stabilisation of Fe once released from sediments into suboxic and oxic waters. Supportive data of other trace metals can be used as an indicator of sediment release, scavenging processes and biological utilisation. Here we present soluble (<0.02 µm), dissolved (<0.2 µm) and total dissolvable (unfiltered) trace metal data collected at 10 stations on a 90 nautical mile transect across the Mauritanian shelf region in June 2014 (cruise Meteor 107). The samples were pre-concentrated using an automated off-line pre-concentration device and analysed simultaneously for Cd, Pb, Fe, Ni, Cu, Zn, Mn and Co using a high resolution inductively coupled plasma mass spectrometer (HR-ICP-MS). First results indicate the importance of benthic sources to the overall Fe budget in this region. Both dissolved Fe and Mn showed enhanced concentrations close to the shelf at depths between 40 and 180 m corresponding with low oxygen concentrations (<50 µmol L-1). Elevated soluble, dissolved, and total dissolvable Fe and Mn concentrations at an offshore station coincided with the location of a cyclonic Eddie that was characterised by an oxygen depleted water body. To further assess the accuracy of vertical and horizontal fluxes of Fe and other trace metals, we compare diffusivity estimates determined by a microstructure profiler and the scale length method (de Jong et al. 2012) with observed isotopic Ra data.

Archaeal diversity and the extent of iron and manganese pyritization in sediments from a tropical mangrove creek (Cardoso Island, Brazil)

NASA Astrophysics Data System (ADS)

Otero, X. L.; Lucheta, A. R.; Ferreira, T. O.; Huerta-Díaz, M. A.; Lambais, M. R.

2014-06-01

Even though several studies on the geochemical processes occurring in mangrove soils and sediments have been performed, information on the diversity of Archaea and their functional roles in these ecosystems, especially in subsurface environments, is scarce. In this study, we have analyzed the depth distribution of Archaea and their possible relationships with the geochemical transformations of Fe and Mn in a sediment core from a tropical mangrove creek, using 16S rRNA gene profiling and sequential extraction of different forms of Fe and Mn. A significant shift in the archaeal community structure was observed in the lower layers (90-100 cm), coinciding with a clear decrease in total organic carbon (TOC) content and an increase in the percentage of sand. The comparison of the archaeal communities showed a dominance of methanogenic Euryarchaeota in the upper layers (0-20 cm), whereas Crenarchaeota was the most abundant taxon in the lower layers. The dominance of methanogenic Euryarchaeota in the upper layer of the sediment suggests the occurrence of methanogenesis in anoxic microenvironments. The concentrations of Fe-oxyhydroxides in the profile were very low, and showed positive correlation with the concentrations of pyrite and degrees of Fe and Mn pyritization. Additionally, a partial decoupling of pyrite formation from organic matter concentration was observed, suggesting excessive Fe pyritization. This overpyritization of Fe can be explained either by the anoxic oxidation of methane by sulfate and/or by detrital pyrite tidal transportation from the surrounding mangrove soils. The higher pyritization levels observed in deeper layers of the creek sediment were also in agreement with its Pleistocenic origin.

In situ expression of nifD in Geobacteraceae in subsurface sediments

USGS Publications Warehouse

Holmes, Dawn E.; Nevin, Kelly P.; Lovely, Derek R.

2004-01-01

In order to determine whether the metabolic state of Geobacteraceae involved in bioremediation of subsurface sediments might be inferred from levels of mRNA for key genes, in situ expression of nifD, a highly conserved gene involved in nitrogen fixation, was investigated. When Geobacter sulfurreducens was grown without a source of fixed nitrogen in chemostats with acetate provided as the limiting electron donor and Fe(III) as the electron acceptor, levels of nifD transcripts were 4 to 5 orders of magnitude higher than in chemostat cultures provided with ammonium. In contrast, the number of transcripts of recA and the 16S rRNA gene were slightly lower in the absence of ammonium. The addition of acetate to organic- and nitrogen-poor subsurface sediments stimulated the growth of Geobacteraceae and Fe(III) reduction, as well as the expression of nifD in Geobacteraceae. Levels of nifD transcripts in Geobacteraceae decreased more than 100-fold within 2 days after the addition of 100 μM ammonium, while levels of recA and total bacterial 16S rRNA in Geobacteraceae remained relatively constant. Ammonium amendments had no effect on rates of Fe(III) reduction in acetate-amended sediments or toluene degradation in petroleum-contaminated sediments, suggesting that other factors, such as the rate that Geobacteraceae could access Fe(III) oxides, limited Fe(III) reduction. These results demonstrate that it is possible to monitor one aspect of the in situ metabolic state of Geobacteraceae species in subsurface sediments via analysis of mRNA levels, which is the first step toward a more global analysis of in situ gene expression related to nutrient status and stress response during bioremediation by Geobacteraceae.

Vertical variation of potential mobility of heavy metal in sediment to groundwater of the Kanto plain, Japan

NASA Astrophysics Data System (ADS)

Hossain, S.; Hachinohe, S.; Ishiyama, T.; Hamamoto, H.; Oguchi, C. T.

2014-12-01

Heavy metals release from sediment may occur due to sediment water interaction under different changing environmental conditions. This has substantial influence on groundwater quality. However, identification of potentially mobile fractions of metals like Cu, Cr, Ni, Pb, Zn, Fe, Mn and Ti requires for the sustainable land and groundwater development and pollution management. 44 sediment and pore water samples at 1 m interval were analyzed from a vertical profile beneath the Naka river at the bottom of Central Kanto plain, Japan. Sequential extraction method was applied to determine potentially mobile forms of metals such as water soluble, ion exchangeable, acid soluble and Fe-Mn oxide bound. Metals were determined using X-Ray Fluorescence, Inductively coupled plasma atomic emission and mass spectrometer. Analyses show that potential mobility is high in river bed, volcanic ash mix, marine and transitional clayey silt. Metal mobility was higher in lower gravelly aquifer than upper sandy aquifer. Potential mobility and bioavailability of Zn, Cu, Ni, Pb and Mn are very high in river bed sediment which may pose threat to river bottom aquatic system. Zn, Cu and Ni concentration in pore water is high in river bed and peat bearing sediment. In pore water of marine and transitional sediment ion concentration such as Ca2+ and SO42- is very high indicating high mobility of Calcium and Sulfur from sediment as no significant variation observed in total content. In vertical profile, potential mobility tendency of metal in sediment trends to be Zn > Cu > Ni > Cr > Pb > Mn > Fe > Ti. Current study indicates low potential mobility and pollution risk to groundwater due to overall low metal concentration in pore water and high portion of metals attached with sediment as Fe-Mn oxide bound. More over under strong reducing condition considerable amount of metals will release and pollute groundwater.

EAG Eminent Speaker: Cold war biogeochemistry: Microbes as architects for metal attenuation

NASA Astrophysics Data System (ADS)

Küsel, K.

2012-04-01

Legacy uranium mining in the area of Ronneburg, Germany, has resulted in extensive outflow of highly heavy metal contaminated ground and upcoming mine waters. Mine water flows along a grassland into a small creek and forms iron-rich precipitates yielding rust-colored terraces at the creek bank. These iron oxyhydroxides could have been formed by iron oxidizing bacteria (FeOB) or by chemical oxidation. Precipitates may serve as important biogeochemical interfaces, because heavy metals can adsorb or co-precipitate with Fe(II) or Fe(III) minerals. Thus, microbial Fe(II) oxidation but also the reductive dissolution of iron oxides can be important processes affecting the stability of metal contaminants. Here we present a study on the potential for iron cycling processes and on indigenous bacterial communities in this acidic creek. Oxic and anoxic in vitro sediment incubations revealed iron oxidation and reduction rates of same magnitude, indicating active iron cycling regardless of pH. XRD and TEM comparing the suspended particle load of water samples with fresh creek sediment showed that amorphous particles likely formed first, then aged to become more crystalline iron oxyhydroxides, such as akaganeite and goethite. During this aging process some of the initially smooth, 50-300 nm spherical particles may have formed nano-sized needles, which could potentially provide high reactive surface area for chemical and biological reactions. Surprisingly, total and dissolved metal concentrations in creek water and sediment revealed that elements such as Mn, Si, Ni, or Zn stayed mostly in solution. Only some metals such as Cu, Cr, and U seemed to be particle-associated in the water, likely co-precipitated with or adsorbed onto freshly-precipitating minerals. Pelagic and particle-associated organisms from water as well as fresh sediments were used for 16S rRNA gene cloning and sequencing and showed that members of the Proteobacteria (mainly Betaproteobacteria and Deltaproteobacteria) dominated bacterial communities. The relative fraction of FeOB-related clones was especially high in upcoming underground water and sediment of the adjacent creek site. Up to 80% of clones in sediment microbial 16S rRNA gene clone libraries had ≥97% sequence similarity to reported FeOM or FeRM, demonstrating a strong link to function, even on RNA level. Three novel moderately acidophilic FeOM strains, Thiomonas sp. FB-Cd and FB-6 and Bordetella sp. FB-8, were isolated from pH 6.3 sediment. FB-6 is likely involved in in situ iron oxidation as it has high similarity to a RNA-derived clone from this sediment. Our results demonstrated active microbial iron cycling in heavy metal contaminated creeks, which have important implications for understanding natural attenuation.

Ferrous iron phosphorus in sediments: development of a quantification method through 2,2'-bipyridine extraction.

PubMed

Li, Qingman; Wang, Xingxiang; Bartlett, Rebecca; Pinay, Gilles; Kan, Dan; Zhang, Wen; Sun, Jingxian

2012-11-01

The role of ferrous iron in the phosphorus cycle of an aquatic ecosystem is poorly understood because of a lack of suitable methods to quantitatively evaluate ferrous iron phosphorus (FIP) phases. Using sediments sampled from Fubao Bay of Dianchi Lake in China, a novel extraction method for FIP using 2,2'-bipyridine was explored. Total phosphorus and iron in the sediments ranged from 1.0 to 5.0 mg/g (dry weight) and 28.5 to 90.6 mg/g, respectively. Organic content (as indicated by loss on ignition or LOI) and iron(II) ranged from 3.1 to 27.0% and 26.5 to 64.9 mg/g, respectively. The dissolution dynamics of FIP extraction with a low solid/liquid ratio (1:25) indicated that a single application of 0.2% 2,2'-bipyridine extracted both iron(II) (Fe(II)) and phosphorus (as PO4(3-)) in sediments with different organic contents with low efficiency. The extraction efficiency of Fe(II) was improved by alteration of the solid/liquid ratio, but the effect was limited. However, addition of a 1:1000 solid/liquid ratio of 0.5 M potassium chloride to a 0.2% 2,2'-bipyridine solution significantly accelerated extraction of FIP with the release of Fe(II) and phosphorus toward equilibrium at approximately 150 hours. Further investigation demonstrated that 2,2'-bipyridine exhibited a higher selectivity in distinguishing FIP from phosphorus bound to ferric (Fe(III)) oxides or precipitated by calcium (Ca2+). Air-drying sediments significantly decreased the amount of extracted FIP, which indicates that fresh, wet sediment should be used in this type of FIP extraction. Based on experimental results using the proposed extraction protocol, (1) FIP in sediments of Fubao Bay had a predominant status in the lake sediment and accounted for 23.4 to 39.8% of total phosphorus, and (2) Fe(II)(FIP) released in the extraction is directly proportional to phosphorus(FIP) (Fe(II)(FIP) = 2.84 x P(FIP) + 0.0007; R2 = 0.97) with an average molar ratio of Fe(II)(FIP)/P(FIP) of 2.7. This study shows that FIP extraction with 2,2'-bipyridine is a robust method for releasing ferrous iron associated with phosphorus. Further, the high percentage of FIP in total phosphorus (40%) measured in the study site using this extraction method suggests that FIP might have been often underestimated in previous studies.

Reactive and recoverable sorbents for halogenated organic compound remediation in sediments

NASA Astrophysics Data System (ADS)

Werner, David; Taggalou, Villy; Kordulis, Christos; Dolfing, Jan; Karapanagioti, Hrissi K.

2013-04-01

Activated carbon (AC) has been proposed as a sediment amendment for aquatic systems polluted with hydrophobic organic compounds. AC acts as a strong binding agent that lowers the pollutant concentration and thus, its toxicity. A draw back of this in-situ remediation method is that although the pollutant will remain non-bioavailable for many years being sorbed into AC, it actually stays in the system. A reactive sorbent, a sorbent that would, at the same time, facilitate the degradation of the pollutant, would be better accepted by the public or the regulators than AC amendment. So far, catalysts supported on AC with zero valent iron and a reactive metal have been proposed for the dechlorination of chlorinated organic compounds. These reactive metals are usually expensive or toxic and thus, their addition to the environment is not desirable. In the present study, activated carbon modified with reduced iron(AC/Fe) is tested in batch systems in the presence of sediment and DDT sorbed on polyethylene sheets. The batch systems are equilibrated for different contact times. Then, the DDT remaining in the polyethylene sheets is quantified along with DDD produced due to the dechlorination of DDT. A small percentage of DDT is degraded to DDD in the systems containing the AC/Fe material. No degradation of DDT is observed in the control systems containing the pollutant and the sediment or the pollutant, the sediment and AC. Thus, the addition of AC/Fe to the sediment with the DDT is enough to cause the dechlorination of DDT. At the end of the experiments, a magnet rod is used to recover the AC/Fe material from the batches with the sediment. An average recovery of 83% is achieved. This is a high percentage suggesting that the material can be easily recovered. Some drawbacks of the material preparation method are identified after the composite material characterization. For example, the AC/Fe surface area is decreased with the material preparation compared to the initial surface area of the AC. This fact results in decrease of the sorption ability of the AC/Fe material compared to that of the AC. At the same time, more DDT degradation might be achievable by increasing the AC/Fe dosage from the 1% weight used in this study that is lower than commonly used for sediment amendments. More research is necessary to optimize the material preparation and properties.

Coupling fractionation and batch desorption to understand arsenic and fluoride co-contamination in the aquifer system.

PubMed

Kumar, Manish; Das, Nilotpal; Goswami, Ritusmita; Sarma, Kali Prasad; Bhattacharya, Prosun; Ramanathan, A L

2016-12-01

The present work is an attempt to study As and F+ coevality using laboratory based assays which couples fractionation and batch dissolution experiments. Sequential extraction procedure (SEP) resulting into five "operationally defined phases", was performed on sediment and soil samples collected from the Brahmaputra flood plains, Assam, India. High correlation between the Fe (hydr)oxide fraction and total As content of the soil/sediment sample indicates the involvement of Fe (hydr)oxides as the principal source of As. F - being an anion has high potential to be sorbed onto positively charged surfaces. Findings of the SEP were used to design the batch desorption experiments by controlling the Fe (hydr)oxide content of the soil/sediment. Desorption of As and F - was observed under acidic, neutral and alkaline pH from untreated and Fe (hydr)oxide removed samples. Highest amount of As and F - were found to be released from untreated samples under alkaline pH, while the amount leached from samples with no Fe (hydr)oxide was low. The study showed that the Fe (hydr)oxide fraction commonly found in the soils and sediments, had high affinity for negatively charged species like F - oxyanions of As, AsO 4 3- (arsenate) and AsO 3 3- (arsenite). Fe (hydr)oxide fraction was found to play the major role in co-evolution of As and F - . Two sorption coefficients were proposed based on easily leachable fraction and As present in the groundwater of sampling location for understanding of contamination vulnerability from the leaching. Copyright © 2016 Elsevier Ltd. All rights reserved.

Sediment cores from kettle holes in NE Germany reveal recent impacts of agriculture.

PubMed

Kleeberg, Andreas; Neyen, Marielle; Schkade, Uwe-Karsten; Kalettka, Thomas; Lischeid, Gunnar

2016-04-01

Glacial kettle holes in young moraine regions receive abundant terrigenous material from their closed catchments. Core chronology and sediment accumulation were determined for two semi-permanent kettle holes, designated RG and KR, on arable land close to the villages of Rittgarten and Kraatz, respectively, in Uckermark, NE Germany. Core dating ((210)Pb, (137)Cs) revealed variable sediment accretion rates through time (RG 0.4-23.1 mm a(-1); KR 0.2-35.5 mm a(-1)), with periods of high accumulation corresponding to periods of intensive agricultural activity and consequent erosional inputs from catchments. Sediment composition (C, N, P, S, K, Ca, Fe, Mn, Zn, Cu, Mo, Pb, Cd, Zr) was used to determine sediment source and input processes. At RG, annual P input increased from 0.65 kg ha(-1) in the early nineteenth century to 1.67 kg ha(-1) by 2013. At KR, P input increased from 0.6 to 4.1 kg ha(-1) over the last century. There was a concurrent increase in Fe input in both water bodies. Thus, Fe/P ratios showed no temporal trend and did not differ between RG (18.5) and KR (18.4), indicating similar P mobility. At RG, the S/Fe ratio increased from 0.4 to 2.3, indicating more iron sulphides and thus higher P availability, coinciding with high coverage of duckweed (Spirodela polyrhiza (L.)) and soft hornwort (Ceratophyllum submersum L.). At KR, however, this ratio remained low and relatively unchanged (0.3 ± 0.4), indicating more efficient Fe-P binding and lower hydrophyte productivity. Trends in sediment composition indicate a shift towards eutrophication in both kettle holes, but with differences in timing and magnitude. Other morphologically similar kettle holes in NE Germany that are prone to erosion could have been similarly impacted but may differ in the extent of sediment infilling and degradation of their ecological functions.

Geochemistry of surface sediments from the fjords of Northern Chilean Patagonia (44-47°S): Spatial variability and implications for paleoclimate reconstructions

NASA Astrophysics Data System (ADS)

Bertrand, Sébastien; Hughen, Konrad A.; Sepúlveda, Julio; Pantoja, Silvio

2012-01-01

The Patagonian fjords have a clear potential to provide high-resolution sedimentary and geochemical records of past climate and environmental change in the Southern Andes. To improve our ability to interpret these proxy records, we investigated the processes that control fjord sediment inorganic geochemistry through a geochemical, mineralogical and sedimentological analysis of surface sediment samples from the fjords of Northern Chilean Patagonia. A simple Terrestrial Index based on measurements of salinity and Fraction of Terrestrial Carbon was used to estimate the terrestrial input/river discharge at each site. Our results demonstrate that, under the cold climate conditions of Patagonia, chemical weathering is weak and the inorganic geochemical composition of the fjord sediments is primarily controlled by hydrodynamic mineralogical sorting, i.e., the intensity of river discharge. Our results suggest that the distribution of Fe, Ti and Zr in surface sediments is controlled by their association with heavy and/or coarse minerals, whereas Al is independent of hydrodynamic processes. The elemental ratios Fe/Al, Ti/Al and Zr/Al are therefore well suited for estimating changes in the energy of terrestrial sediment supply into the fjords through time. Zr/Al is particularly sensitive in proximal environments, while Fe/Al is most useful in the outer fjords and on the continental margin. In the most proximal environments, however, Fe/Al is inversely related to hydrodynamic conditions. Caution should therefore be exercised when interpreting Fe/Al ratios in terms of past river discharge. The application of these proxies to long sediment cores from Quitralco fjord and Golfo Elefantes validates our interpretations. Our results also emphasize the need to measure Al-based elemental ratios at high precision, which can be achieved using simultaneous acquisition ICP-AES technology. This study therefore constitutes a strong basis for the interpretation of sedimentary records from the Chilean Fjords.

Magnesium, Iron and Aluminum in LLNL Air Particulate and Rain Samples with Reference to Magnesium in Industrial Storm Water

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

Esser, Bradley K.; Bibby, Richard K.; Fish, Craig

Storm water runoff from the Lawrence Livermore National Laboratory’s (LLNL’s) main site and Site 300 periodically exceeds the Discharge Permit Numeric Action Level (NAL) for Magnesium (Mg) under the Industrial General Permit (IGP) Order No. 2014-0057-DWQ. Of particular interest is the source of magnesium in storm water runoff from the site. This special study compares new metals data from air particulate and precipitation samples from the LLNL main site and Site 300 to previous metals data for storm water from the main site and Site 300 and alluvial sediment from the main site to investigate the potential source of elevatedmore » Mg in storm water runoff. Data for three metals (Mg, Iron {Fe}, and Aluminum {Al}) were available from all media; data for additional metals, such as Europium (Eu), were available from rain, air particulates, and alluvial sediment. To attribute source, this study compared metals concentration data (for Mg, Al, and Fe) in storm water and rain; metal-metal correlations (Mg with Fe, Mg with Al, Al with Fe, Mg with Eu, Eu with Fe, and Eu with Al) in storm water, rain, air particulates, and sediments; and metal-metal ratios ((Mg/Fe, Mg/Al, Al/Fe, Mg/Eu, Eu/Fe, and Eu/Al) in storm water, rain, air particulates and sediments. The results presented in this study are consistent with a simple conceptual model where the source of Mg in storm water runoff is air particulate matter that has dry-deposited on impervious surfaces and subsequently entrained in runoff during precipitation events. Such a conceptual model is consistent with 1) higher concentrations of metals in storm water runoff than in precipitation, 2) the strong correlation of Mg with Aluminum (Al) and Iron (Fe) in both storm water and air particulates, and 3) the similarity in metal mass ratios between storm water and air particulates in contrast to the dissimilarity of metal mass ratios between storm water and precipitation or alluvial sediment. The strong correlation of Mg with Fe and Al and of Fe with Al in storm water and air particulates and the strong association of Mg, Fe, and Al with Eu in air particulates strongly suggests that a dominant source of the Mg in storm water is associated with mineral phases of natural origin. These observations all point to Mg exceedances being associated with natural sources and processes and not with anthropogenic processes or pollutant sources.« less

Multivariate analysis and geochemical approach for assessment of metal pollution state in sediment cores.

PubMed

Jamshidi-Zanjani, Ahmad; Saeedi, Mohsen

2017-07-01

Vertical distribution of metals (Cu, Zn, Cr, Fe, Mn, Pb, Ni, Cd, and Li) in four sediment core samples (C 1 , C 2 , C 3 , and C 4 ) from Anzali international wetland located southwest of the Caspian Sea was examined. Background concentration of each metal was calculated according to different statistical approaches. The results of multivariate statistical analysis showed that Fe and Mn might have significant role in the fate of Ni and Zn in sediment core samples. Different sediment quality indexes were utilized to assess metal pollution in sediment cores. Moreover, a new sediment quality index named aggregative toxicity index (ATI) based on sediment quality guidelines (SQGs) was developed to assess the degree of metal toxicity in an aggregative manner. The increasing pattern of metal pollution and their toxicity degree in upper layers of core samples indicated increasing effects of anthropogenic sources in the study area.

The effect of biogenic Fe(II) on the stability and sorption of Co(II)EDTA 2- to goethite and a subsurface sediment

NASA Astrophysics Data System (ADS)

Zachara, John M.; Smith, Steven C.; Fredrickson, James K.

2000-04-01

Laboratory experiments were conducted with suspensions of goethite (α-FeOOH) and a subsurface sediment to assess the influence of bacterial iron reduction on the fate of Co(II)EDTA 2-, a representative metal-ligand complex of intermediate stability (log K Co(II)EDTA = 17.97). The goethite was synthetic (ca. 55 m 2/g) and the sediment was a Pleistocene age, Fe(III) oxide-containing material from the Atlantic coastal plain (Milford). Shewanella alga strain BrY, a dissimilatory iron reducing bacterium (DIRB), was used to promote Fe(III) oxide reduction. Sorption isotherms and pH adsorption edges were measured for Co 2+, Fe 2+, Co(II)EDTA 2-, and Fe(II)EDTA 2- on the two sorbents in 0.001 mol/L Ca(ClO 4) 2 to aid in experiment interpretation. Anoxic suspensions of the sorbents in PIPES buffer at pH 6.5-7.0 were spiked with Co(II)EDTA 2- (10 -5 mol/L, 60Co and 14EDTA labeled), inoculated with BrY (1-6 × 10 8 organisms/mL), and the headspace filled with a N 2/H 2 gas mix. The experiments were conducted under non-growth conditions. The medium did not contain PO 43- (with one exception), trace elements, or vitamins. The tubes were incubated under anoxic conditions at 25°C for time periods in excess of 100 d. Replicate tubes were sacrificed and analyzed at desired time periods for pH, Fe(II) TOT, Fe (aq)2+, 60Co, and 14EDTA. Abiotic analogue experiments were conducted where Fe (aq)2+ was added in increasing concentration to Co(II)EDTA 2-/mineral suspensions to simulate the influence of bacterial Fe(II) evolution. The DIRB generated Fe(II) from both goethite and the Milford sediment that was strongly sorbed by mineral surfaces. Aqueous Fe 2+ increased during the experiment as surfaces became saturated; Fe (aq)2+ induced the dissociation of Co(II)EDTA 2- into a mixture of Co 2+, Co(II)EDTA 2-, and Fe(II)EDTA 2- (log K Fe(II)EDTA = 15.98). The extent of dissociation of Co(II)EDTA 2- was greater in the subsurface sediment because it sorbed Fe(II) less strongly than did goethite. The post dissociation sorption behavior of Co 2+ was dependent on pH and the intrinsic sorptivity of the solid phases. Dissociation generally lead to an increase in the sorption (e.g., K d) of Co 2+ relative to EDTA 4- (form unspecified). Sorbed biogenic Fe(II) competed with free Co (aq)2+and reduced its sorption relative to unreduced material. It is concluded that cationic radionuclides such as 60Co or 239/240Pu, which may be mobilized from disposed wastes by complexation with EDTA 4-, may become immobilized in groundwater zones where dissimilatory bacterial iron reduction is operative.

Isotopic, petrologic and biogeochemical investigations of banded iron-formations

NASA Technical Reports Server (NTRS)

Hayes, J. M.; Kaufman, A. J.; Klein, C.; Studley, S. A.; Baur, M. E.; Walter, M. R.

1986-01-01

It is recognized that the first occurrence of banded iron-formations (BIFs) clearly predates biological oxygenation of the atmosphere-hydrosphere system and that their last occurrences extend beyond plausible dates of pervasive biological oxygenation. For this reason, and because enormous quantities of oxidizing power have been sequestered in them, it is widely thought that these massive, but enigmatic, sediments must encode information about the mechanism and timing of the rise of atmospheric O2. By coupling isotopic analyses of iron-formation carbonates with biogeochemical and petrologic investigations, we are studying (1) the mechanism of initial sedimentation of iron; (2) the role of iron in microbially mediated diagenetic processes in fresh iron-formation sediments; and (3) the logical integration of mechanisms of deposition with observed levels of banding. Thus far, it has been shown that (1) carbonates in BIFs of the Hamersley Group of Western Australia are isotopically inhomogenous; (2) the nature and pattern of isotopic ordering is not consistent with a metamorphic origin for the overall depletion of C-13 observed in the carbonates; (3) if biological, the origin of the C-13 depleted carbonate could be either respiratory or fermentative; (4) iron may have been precipitate d as Fe(3+), then reduced to Fe(2+) within the sediment; and (5) sedimentary biogeochemical systems may have been at least partially closed to mass transport of carbonate species.

A mycological baseline study based on a multidisciplinary approach in a coastal area affected by contaminated torrent input.

PubMed

Capello, M; Carbone, C; Cecchi, G; Consani, S; Cutroneo, L; Di Piazza, S; Greco, G; Tolotti, R; Vagge, G; Zotti, M

2017-06-15

Fungi include a vast group of eukaryotic organisms able to colonise different natural, anthropised and extreme environments, including marine areas contaminated by metals. The present study aims to give a first multidisciplinary characterisation of marine bottom sediments contaminated by metals (Cd, Co, Cr, Cu, Ni, and Zn), originating in the water leakage from an abandoned Fe-Cu sulphide mine (Libiola, north-western Italy), and evaluate how the chemical and physical parameters of water and sediments may affect the benthic fungal communities. Our preliminary results showed the high mycodiversity of the marine sediments studied (13 genera and 23 species of marine fungi isolated), and the great physiological adaptability that this mycobiota evolved in reaction to the effects of the ecotoxic bottom sediment contamination, and associated changes in the seawater parameters. Copyright © 2017 Elsevier Ltd. All rights reserved.

Trace elements records from vermetids aragonite as millennial paleo-oceanographic archives in the South-East Mediterranean

NASA Astrophysics Data System (ADS)

Jacobson, Yitzhak; Yam, Ruth; Shemesh, Aldo

2017-04-01

The Mediterranean Sea is a region under high anthropogenic stress, thus a hotspot for climate change studies. Natural conditions, such as SST, productivity, precipitation and dust fluxes along with human induced activity affect seawater chemistry. We study millennial variability of trace elements in East Mediterranean Sea high-resolution records, in attempt to connect them to environmental factors. The Mediterranean reef builder Vermetid, D. petraeum is a sessile gastropod, secreting its aragonite shells in tidal zones. Cores of Vermetid reefs from the South Eastern Mediterranean (Israel) were previously analyzed by Sisma?Ventura et al. (2014) to reconstruct seawater surface temperature (SST) and δ13C of dissolved inorganic carbon (DIC). In this study we analyzed trace elements of these vermetid cores, and reconstructed millennial records of elements to calcium (el/Ca) molar ratios. Vermetid trace element contents from recent decades are mostly in agreement with known values for marine biogenic aragonites from corals and mollusk. We divide vermetid trace element records into three element groups: 1) Sr and U are related to SST and DIC. These elements correlate with major climatic events of the last millennium, such as the Medieval Warm Period (900-1300 AD) and the Little Ice Age (1450-1850 AD). 2) Pb and Cd are related to anthropogenic pollution and demonstrate industrial sourced trends throughout the anthropocene (since 1750 AD). 3) Terrogenous elements, including Fe, Al, Mn and V. Al in seawater and sediments has been used to trace water masses and land derived sediment source. We observe a major change in average vermetid Al/Fe ratios from 0.5 to 2.5 over the recorded period (n=72). This vermetid Al/Fe change points at a possible shift from Nilotic sediments (0.1-0.5 Al/Fe molar ratio) to Saharan dust ratio (2-4 Al/Fe molar ratio). Mn and V show a similar variability to Fe. Understanding the variability of vermetid TE can help us interpret the relative dominance of different climate systems and anthropogenic processes on the East Mediterranean environment.

Relationships between microbial communities and environmental parameters at sites impacted by mining of volcanogenic massive sulfide deposits, Prince William Sound, Alaska

USGS Publications Warehouse

Foster, A.L.; Munk, L.; Koski, R.A.; Shanks, Wayne C.; Stillings, L.L.

2008-01-01

The relations among geochemical parameters and sediment microbial communities were examined at three shoreline sites in the Prince William Sound, Alaska, which display varying degrees of impact by acid-rock drainage (ARD) associated with historic mining of volcanogenic massive sulfide deposits. Microbial communities were examined using total fatty acid methyl esters (FAMEs), a class of compounds derived from lipids produced by eukaryotes and prokaryotes (bacteria and Archaea); standard extraction techniques detect FAMEs from both living (viable) and dead (non-viable) biomass, but do not detect Archaeal FAMEs. Biomass and diversity (as estimated by FAMEs) varied strongly as a function of position in the tidal zone, not by study site; subtidal muds, Fe oxyhydroxide undergoing biogenic reductive dissolution, and peat-rich intertidal sediment had the highest values. These estimates were lowest in acid-generating, intertidal zone sediment; if valid, the estimates suggest that only one or two bacterial species predominate in these communities, and/or that Archeal species are important members of the microbial community in this sediment. All samples were dominated by bacterial FAMEs (median value >90%). Samples with the highest absolute abundance of eukaryotic FAMEs were biogenic Fe oxyhydroxides from shallow freshwater pools (fungi) and subtidal muds (diatoms). Eukaryotic FAMEs were practically absent from low-pH, sulfide-rich intertidal zone sediments. The relative abundance of general microbial functional groups such as aerobes/anaerobes and gram(+)/gram(-) was not estimated due to severe inconsistency among the results obtained using several metrics reported in the literature. Principal component analyses (PCAs) were performed to investigate the relationship among samples as separate functions of water, sediment, and FAMEs data. PCAs based on water chemistry and FAMEs data resulted in similar relations among samples, whereas the PCA based on sediment chemistry produced a very different sample arrangement. Specifically, the sediment parameter PCA grouped samples with high bulk trace metal concentration regardless of whether the metals were incorporated into secondary precipitates or primary sulfides. The water chemistry PCA and FAMEs PCA appear to be less prone to this type of artifact. Signature lipids in sulfide-rich sediments could indicate the presence of acid-tolerant and/or acidophilic members of the genus Thiobacillus or they could indicate the presence of SO4-reducing bacteria. The microbial community documented in subtidal and offshore sediments is rich in SRB and/or facultative anaerobes of the Cytophaga-Flavobacterium group; both could reasonably be expected in PWS coastal environments. The results of this study provide evidence for substantial feedback between local (meter to centimeter-scale) geochemical variations, and sediment microbial community composition, and show that microbial community signatures in the intertidal zone are significantly altered at sites where ARD drainage is present relative to sites where it is not, even if the sediment geochemistry indicates net accumulation of ARD-generated trace metals in the intertidal zone. ?? 2007 Elsevier Ltd. All rights reserved.

The effect of sediment mixing on mercury dynamics in two intertidal mudflats at Great Bay Estuary, New Hampshire, USA

PubMed Central

Brown, Lauren E.; Chen, Celia Y.; Voytek, Mary A.; Amirbahman, Aria

2016-01-01

Estuarine sediments store particulate contaminants including mercury (Hg). We studied Hg sediment dynamics in two intertidal mudflats at Great Bay estuary, NH, over multiple years. Sediments at both mudflats were physically mixed down to ~10 cm, as determined by 7Be measurements, albeit via different mechanisms. Portsmouth mudflat (PT) sediments were subject to bioturbation by infaunal organisms and Squamscott mudflat (SQ) sediments were subject to erosion and redeposition. The presence of higher concentrations of fresh Fe(III) hydroxide at PT suggested bioirrigation by the polychaetes (Nereis virens). At depths where infaunal bioirrigation was observed, pore-water inorganic Hg (Hgi) and methylmercury (MeHg) were lower potentially due to their interaction with Fe(III) hydroxide. Methylmercury concentrations increased immediately below this zone in some samples, suggesting that the observed increase in material flux in bioirrigated sediments may initiate from lower depths. Pore water in sediment at PT also had higher fractions of more protein-like and labile DOC than those at SQ that can lead to increased MeHg production in PT, especially at depths where Hgi is not removed from solution by Fe(III) hydroxide. Where sediment erosion and redeposition were observed at SQ, Hg species distribution was extended deeper into the sediment column. Moreover, methyl coenzyme M reductase (MCR) and mercury reductase (mer-A) genes were higher at SQ than PT suggesting differences in conditions for Hg cycling. Results showed that the near-surface region of high MeHg concentrations commonly observed in unmixed sediments does not exist in physically mixed sediments that are common in many estuarine environments. PMID:26924879

The effect of sediment mixing on mercury dynamics in two intertidal mudflats at Great Bay Estuary, New Hampshire, USA.

PubMed

Brown, Lauren E; Chen, Celia Y; Voytek, Mary A; Amirbahman, Aria

2015-12-01

Estuarine sediments store particulate contaminants including mercury (Hg). We studied Hg sediment dynamics in two intertidal mudflats at Great Bay estuary, NH, over multiple years. Sediments at both mudflats were physically mixed down to ~10 cm, as determined by 7 Be measurements, albeit via different mechanisms. Portsmouth mudflat (PT) sediments were subject to bioturbation by infaunal organisms and Squamscott mudflat (SQ) sediments were subject to erosion and redeposition. The presence of higher concentrations of fresh Fe(III) hydroxide at PT suggested bioirrigation by the polychaetes ( Nereis virens ). At depths where infaunal bioirrigation was observed, pore-water inorganic Hg (Hg i ) and methylmercury (MeHg) were lower potentially due to their interaction with Fe(III) hydroxide. Methylmercury concentrations increased immediately below this zone in some samples, suggesting that the observed increase in material flux in bioirrigated sediments may initiate from lower depths. Pore water in sediment at PT also had higher fractions of more protein-like and labile DOC than those at SQ that can lead to increased MeHg production in PT, especially at depths where Hg i is not removed from solution by Fe(III) hydroxide. Where sediment erosion and redeposition were observed at SQ, Hg species distribution was extended deeper into the sediment column. Moreover, methyl coenzyme M reductase (MCR) and mercury reductase ( mer -A) genes were higher at SQ than PT suggesting differences in conditions for Hg cycling. Results showed that the near-surface region of high MeHg concentrations commonly observed in unmixed sediments does not exist in physically mixed sediments that are common in many estuarine environments.

From source to sink: Rare-earth elements trace the legacy of sulfuric dredge spoils on estuarine sediments.

PubMed

Xu, Nian; Morgan, Bree; Rate, Andrew W

2018-05-17

Land disposal of dredged sulfide-rich coastal sediments generates secondary coastal acid sulfate soils (CASS), as previously reduced sulfide minerals oxidise to produce acidic drainage rich in Fe, SO 4 2- and rare-earth elements (REEs). Few studies investigate both the source and the sink of REEs in the context of interpreting their mobilisation and potential use in tracing anthropogenic activity. Here we investigate REE signatures in estuarine sediments (and overlying surface waters) that have received acute, long-term (>15 years) acidic drainage from legacy sulfuric dredge spoils. It was found that the dredge spoil continues to act as a source of acidity (pH 3.5-5.5), Fe and REEs during development of CASS, and contains negligible acid volatile sulfide (AVS, a proxy for FeS) and relatively low concentrations of ΣREE (mean 44.5 mg/kg, range 4.1-362 mg/kg). In the receiving sediments, high AVS concentrations (mean 92.2 μmol/g, range 0.38-278 μmol/g) reflect elevated FeS content, likely due to high inputs of Fe and SO 4 2- from the acidic drainage, and correspond with a high concentration of total S (mean 852 μmol/g, range 105-2209 μmol/g) and an accumulation of ΣREE (mean 670 mg/kg, range 19.9-1819 mg/kg). Importantly, where drain sediments that were previously enriched in highly reactive sulfidic minerals and trace elements and have become exposed to the atmosphere (e.g. Site 3) and partially oxidised, they provide a further source of acidification, remobilising the REEs to the downstream sediments. Interestingly, we also found a clear positive correlation between phosphorous and REEs both in the dredge spoil and sediment, suggesting phosphate minerals may act as a sink for REEs in CASS influenced drain sediments. This is further supported by strong positive gadolinium anomalies (1.1-1.6) and high calculated anthropogenic Gd values (12-38%), which may reflect the influence of phosphate fertiliser on this eutrophic system. Copyright © 2018 Elsevier B.V. All rights reserved.

Characterization of Natural Organic Matter in Alluvial Aquifer Sediments: Approaches and Implications for Reactivity

NASA Astrophysics Data System (ADS)

Fox, P. M.; Nico, P. S.; Hao, Z.; Gilbert, B.; Tfaily, M. M.; Devadoss, J.

2015-12-01

Sediment-associated natural organic matter (NOM) is an extremely complex assemblage of organic molecules with a wide range of sizes, functional groups, and structures, which is intricately associated with mineral particles. The chemical nature of NOM may control its' reactivity towards metals, minerals, enzymes, and bacteria. Organic carbon concentrations in subsurface sediments are typically much lower than in surface soils, posing a distinct challenge for characterization. In this study, we investigated NOM associated with shallow alluvial aquifer sediments in a floodplain of the Colorado River. Total organic carbon (TOC) contents in these subsurface sediments are typically around 0.1%, but can range from 0.03% up to approximately 1.5%. Even at the typical TOC values of 0.1%, the mass of sediment-associated OC is approximately 5000 times higher than the mass of dissolved OC, representing a large pool of carbon that may potentially be mobilized or degraded under changing environmental conditions. Sediment-associated OC is much older than both the depositional age of the alluvial sediments and dissolved OC in the groundwater, indicating that the vast majority of NOM was sequestered by the sediment long before it was deposited in the floodplain. We have characterized the sediment-bound NOM from two locations within the floodplain with differing physical and geochemical properties. One location has relatively low organic carbon (<0.2%) and is considered suboxic [dissolved oxygen is low or absent, but no dissolved Fe(II) observed], while the other is a naturally reducing zone with higher organic carbon (0.2-1.5%) and Fe(II)-reducing conditions. An extraction scheme was developed using a combination of sequential extraction [water and sodium pyrophosphate (pH 10)] and purification in order to isolate different fractions of sediment-associated NOM. Analysis of these different NOM fractions was then carried out by FTIR and ESI-FTICR-MS to allow for comparison of NOM structure and composition both across sites and across fractions for a single location. Using this combination of analytical techniques we can probe the variation in NOM chemical composition and mineral association across different biogeochemical regimes and assess the potential reactivity of various NOM pools.

Fe-phyllosilicate redox cycling organisms from a redox transition zone in Hanford 300 Area sediments.

PubMed

Benzine, Jason; Shelobolina, Evgenya; Xiong, Mai Yia; Kennedy, David W; McKinley, James P; Lin, Xueju; Roden, Eric E

2013-01-01

Microorganisms capable of reducing or oxidizing structural iron (Fe) in Fe-bearing phyllosilicate minerals were enriched and isolated from a subsurface redox transition zone at the Hanford 300 Area site in eastern Washington, USA. Both conventional and in situ "i-chip" enrichment strategies were employed. One Fe(III)-reducing Geobacter (G. bremensis strain R1, Deltaproteobacteria) and six Fe(II) phyllosilicate-oxidizing isolates from the Alphaproteobacteria (Bradyrhizobium japonicum strains 22, is5, and in8p8), Betaproteobacteria (Cupriavidus necator strain A5-1, Dechloromonas agitata strain is5), and Actinobacteria (Nocardioides sp. strain in31) were recovered. The G. bremensis isolate grew by oxidizing acetate with the oxidized form of NAu-2 smectite as the electron acceptor. The Fe(II)-oxidizers grew by oxidation of chemically reduced smectite as the energy source with nitrate as the electron acceptor. The Bradyrhizobium isolates could also carry out aerobic oxidation of biotite. This is the first report of the recovery of a Fe(II)-oxidizing Nocardioides, and to date only one other Fe(II)-oxidizing Bradyrhizobium is known. The 16S rRNA gene sequences of the isolates were similar to ones found in clone libraries from Hanford 300 sediments and groundwater, suggesting that such organisms may be present and active in situ. Whole genome sequencing of the isolates is underway, the results of which will enable comparative genomic analysis of mechanisms of extracellular phyllosilicate Fe redox metabolism, and facilitate development of techniques to detect the presence and expression of genes associated with microbial phyllosilicate Fe redox cycling in sediments.

Fe-phyllosilicate redox cycling organisms from a redox transition zone in Hanford 300 Area sediments

PubMed Central

Benzine, Jason; Xiong, Mai Yia; Kennedy, David W.; McKinley, James P.; Lin, Xueju; Roden, Eric E.

2013-01-01

Microorganisms capable of reducing or oxidizing structural iron (Fe) in Fe-bearing phyllosilicate minerals were enriched and isolated from a subsurface redox transition zone at the Hanford 300 Area site in eastern Washington, USA. Both conventional and in situ “i-chip” enrichment strategies were employed. One Fe(III)-reducing Geobacter (G. bremensis strain R1, Deltaproteobacteria) and six Fe(II) phyllosilicate-oxidizing isolates from the Alphaproteobacteria (Bradyrhizobium japonicum strains 22, is5, and in8p8), Betaproteobacteria (Cupriavidus necator strain A5-1, Dechloromonas agitata strain is5), and Actinobacteria (Nocardioides sp. strain in31) were recovered. The G. bremensis isolate grew by oxidizing acetate with the oxidized form of NAu-2 smectite as the electron acceptor. The Fe(II)-oxidizers grew by oxidation of chemically reduced smectite as the energy source with nitrate as the electron acceptor. The Bradyrhizobium isolates could also carry out aerobic oxidation of biotite. This is the first report of the recovery of a Fe(II)-oxidizing Nocardioides, and to date only one other Fe(II)-oxidizing Bradyrhizobium is known. The 16S rRNA gene sequences of the isolates were similar to ones found in clone libraries from Hanford 300 sediments and groundwater, suggesting that such organisms may be present and active in situ. Whole genome sequencing of the isolates is underway, the results of which will enable comparative genomic analysis of mechanisms of extracellular phyllosilicate Fe redox metabolism, and facilitate development of techniques to detect the presence and expression of genes associated with microbial phyllosilicate Fe redox cycling in sediments. PMID:24379809

Geochemical fractionation and pollution assessment of Zn, Cu, and Fe in surface sediments from Shadegan Wildlife Refuge, southwest of Iran.

PubMed

Chaharlang, Behnam Heidari; Bakhtiari, Alireza Riyahi; Mohammadi, Jahangard; Farshchi, Parvin

2017-09-01

This research focuses on the fractionation and distribution patterns of heavy metals (Zn, Cu, and Fe) in surficial sediments collected from Shadegan Wildlife Refuge, the biggest wetland in southern part of Iran, to provide an overall classification for the sources of metals in the study area using a sequential extraction method. For this purpose, a four-step sequential extraction technique was applied to define the partitioning of the metals into different geochemical phases of the sediment. The results illustrated that the average total level of Zn, Cu, and Fe in surface sediments were 55.20 ± 16.04, 22.86 ± 5.68, and 25,979.01 ± 6917.91 μg/g dw, respectively. On the average, the chemical partitioning of all metals in most stations was in the order of residual >oxidizable-organic > acid-reducible > exchangeable. In the same way, the results of calculated geochemical indices revealed that Cu, Zn, and Fe concentrations are mainly influenced by lithogenic origins. Compared with consensus-based SQGs, Cu was likely to result in occasionally harmful biological effects on the biota.

The influence of human settlement on the distribution and diversity of iron-oxidizing bacteria belonging to the Gallionellaceae in tropical streams

PubMed Central

Reis, Mariana P.; Ávila, Marcelo P.; Costa, Patrícia S.; Barbosa, Francisco A. R.; Laanbroek, Hendrikus J.; Chartone-Souza, Edmar; Nascimento, Andréa M. A.

2014-01-01

Among the neutrophilic iron-oxidizing bacteria (FeOB), Gallionella is one of the most abundant genera in freshwater environments. By applying qPCR and DGGE based on 16S rRNA gene-directed primers targeting Gallionellaceae, we delineated the composition and abundance of the Gallionellaceae-related FeOB community in streams differentially affected by metal mining, and explored the relationships between these community characteristics and environmental variables. The sampling design included streams historically impacted by mining activity and a non-impacted stream. The sediment and water samples harbored a distinct community represented by Gallionella, Sideroxydans, and Thiobacillus species. Sequences affiliated with Gallionella were exclusively observed in sediments impacted by mining activities, suggesting an adaptation of this genus to these environments. In contrast, Sideroxydans-related sequences were found in all sediments including the mining impacted locations. The highest and lowest relative frequencies of Gallionellaceae-related FeOB were associated with the lowest and highest concentrations of Fe, respectively. The data enclosed here clearly show distinct species-specific ecological niches, with Gallionella species dominating in sediments impacted by anthropogenic activities over Sideroxydans species. PMID:25505456

Metals in some lagoons of Mexico.

PubMed

Vazquez, F G; Sharma, V K; Alexander, V H; Frausto, C A

1995-02-01

The concentrations of metals, Cd, Cu, Fe, Mn, Ni, Pb, and Zn were determined in some lagoons to establish the level of metal pollution. The lagoons studied were Alvarado lagoon, Veracruz; San Andres lagoon, Tamaulipas; and Terminos lagoon, Campeche. The concentrations were determined in water, oyster (Crassostrea virginica), and sediments. Metals were accumulated in either oysters or sediments. Cu and Zn were higher in oysters and Fe and Mn were higher in sediments. The results in water samples were compared with the limit established by the Secretaria de Ecologia and Desarrollo Urbano Report and briefly discussed.

Quantifying export production in the Southern Ocean: Implications for the Baxs proxy

NASA Astrophysics Data System (ADS)

Hernandez-Sanchez, Maria T.; Mills, Rachel A.; Planquette, HéLèNe; Pancost, Richard D.; Hepburn, Laura; Salter, Ian; Fitzgeorge-Balfour, Tania

2011-12-01

The water column and sedimentary Baxs distribution around the Crozet Plateau is used to decipher the controls and timing of barite formation and to evaluate how export production signals are recorded in sediments underlying a region of natural Fe fertilization within the Fe limited Southern Ocean. Export production estimated from preserved, vertical sedimentary Baxs accumulation rates are compared with published export fluxes assessed from an integrated study of the biological carbon pump to determine the validity of Baxs as a quantitative proxy under different Fe supply conditions typical of the Southern Ocean. Detailed assessment of the geochemical partitioning of Ba in sediments and the lithogenic end-member allows appropriate correction of the bulk Ba content and determination of the Baxs content of sediments and suspended particles. The upper water column distribution of Baxs is extremely heterogeneous spatially and temporally. Organic carbon/Baxs ratios in deep traps from the Fe fertilized region are similar to other oceanic settings allowing quantification of the inferred carbon export based on established algorithms. There appears to be some decoupling of POC and Ba export in the Fe limited region south of the Plateau. The export production across the Crozet Plateau inferred from the Baxs sedimentary proxy indicates that the Fe fertilized area to the north of the Plateau experiences enhanced export relative to equivalent Southern Ocean settings throughout the Holocene and that this influence may also have impacted the site to the south for significant periods. This interpretation is corroborated by alternative productivity proxies (opal accumulation, 231Paxs/230Thxs). Baxs can be used to quantify export production in complex settings such as naturally Fe-fertilized (volcanoclastic) areas, providing appropriate lithogenic correction is undertaken, and sediment focusing is corrected for along with evaluation of barite preservation.

Geochemical controls on microbial nitrate-dependent U(IV) oxidation

USGS Publications Warehouse

Senko, John M.; Suflita, Joseph M.; Krumholz, Lee R.

2005-01-01

After reductive immobilization of uranium, the element may be oxidized and remobilized in the presence of nitrate by the activity of dissimilatory nitrate-reducing bacteria. We examined controls on microbially mediated nitrate-dependent U(IV) oxidation in landfill leachate-impacted subsurface sediments. Nitrate-dependent U(IV)-oxidizing bacteria were at least two orders of magnitude less numerous in these sediments than glucose- or Fe(II)-oxidizing nitrate-reducing bacteria and grew more slowly than the latter organisms, suggesting that U(IV) is ultimately oxidized by Fe(III) produced by nitrate-dependent Fe(II)-oxidizing bacteria or by oxidation of Fe(II) by nitrite that accumulates during organotrophic dissimilatory nitrate reduction. We examined the effect of nitrate and reductant concentration on nitrate-dependent U(IV) oxidation in sediment incubations and used the initial reductive capacity (RDC = [reducing equivalents] - [oxidizing equivalents]) of the incubations as a unified measurement of the nitrate or reductant concentration. When we lowered the RDC with progressively higher nitrate concentrations, we observed a corresponding increase in the extent of U(IV) oxidation, but did not observe this relationship between RDC and U(IV) oxidation rate, especially when RDC > 0, suggesting that nitrate concentration strongly controls the extent, but not the rate of nitrate-dependent U(IV) oxidation. On the other hand, when we raised the RDC in sediment incubations with progressively higher reductant (acetate, sulfide, soluble Fe(II), or FeS) concentrations, we observed progressively lower extents and rates of nitrate-dependent U(IV) oxidation. Acetate was a relatively poor inhibitor of nitrate-dependent U(IV) oxidation, while Fe(II) was the most effective inhibitor. Based on these results, we propose that it may be possible to predict the stability of U(IV) in a bioremediated aquifer based on the geochemical characteristics of that aquifer.

Phosphorus speciation and its bioavailability in sediments of the Jiaozhou Bay

NASA Astrophysics Data System (ADS)

Kang, Xuming; Song, Jinming; Yuan, Huamao; Shi, Xin; Yang, Weifeng; Li, Xuegang; Li, Ning; Duan, Liqin

2017-03-01

Phosphorus (P) is an important macronutrient that can limit primary productivity in coastal marine ecosystems. In this study, four sediment cores were collected in the Jiaozhou Bay to study the phosphorus forms and their bioavailability, including exchangeable or loosely sorbed P (Ex-P), iron-bound P (Fe-P), authigenic P (Ca-P), detrital P (De-P) and organic P (OP), which were separated and quantified using a sequential extraction method (SEDEX). The results showed that the concentration of total P (TP) in core sediments ranged from 6.23 to 10.46 μmol/g, and inorganic P (IP) was the dominated P form. Fe-P and De-P were the main chemical forms of IP in core sediments. The profile variation of OP presented the most significant among the phosphorus forms. Whereas the concentrations of Ex-P, Fe-P, and Ca-P varied slightly with depth, indicating that the transformation of Ex-P, Fe-P, Ca-P, and OP could occur during sedimentary P burial. Moreover, the distribution of P species was influenced by many factors, including terrigenous input, biological processes, organic matter degradation and increasing human activities. High total organic carbon (TOC)/OP ratio occurred in the Jiaozhou Bay, ranging from 73 to 472 (average, 180 ± 81) in core sediments, which was caused by the increasing terrestrial organic matter. The ratio of TOC/Preactive ranged from 24 to 101 (average 46 ± 15) in core sediments (lower than the Redfield ratio), implying a surplus of sedimentary reactive P compared with TOC. Potential bioavailable P (BAP) accounted for about 28.2-60.8% (average, 47.1 ± 7.4%) of TP in core sediments, and presented an increasing trend since 1980s, which might be responsible for the shift of phytoplankton community composition during these decades.

Nontronite Stability in Near-Surface Sediments

NASA Astrophysics Data System (ADS)

Home, C.; Baker, L.

2015-12-01

The purpose of this study is to examine how long nontronite clays persist in soil, by studying samples collected from a sediment cone weathering out of crack in a basalt outcrop near Moscow Idaho. Nontronite, a dioctahedral ferric smectite clay, is a frequent weathering product of basaltic rocks. However, it is rarely described in surface soils, even in basaltic terrains. At our field site, nontronite formed by basalt weathering is eroding from cracks in the basalt and forming small talus cones. We are examining samples collected from a trench and several soil cores to determine the clay mineralogy at different depths in the talus cone. Bulk and clay mineralogy is being determined using X-ray Diffractometry (XRD) analysis and Fourier Transform Infrared Spectroscopy (FT-IR) analysis. Bulk chemical analyses, and selective extractions with acid oxalate and citrate-bicarbonate-dithionite reagents, are being used to analyze Fe mineralogy and amorphous constituents. Preliminary observations suggest that iron mineralogy may vary with depth in the sediments, and that older, deeper sediments may contain more Fe in oxide phases. We hypothesize that nontronite in the sediments is decomposing over time to form low-Fe smectites + Fe oxides. The results of this study will help determine whether nontronite is stable to erosion and redeposition in a surficial environment, as well as the timescale of its possible decomposition. These results may be useful in assessing proposed models of nontronite transport and redeposition on Mars.

Oxidation of aromatic contaminants coupled to microbial iron reduction

USGS Publications Warehouse

Lovley, D.R.; Baedecker, M.J.; Lonergan, D.J.; Cozzarelli, I.M.; Phillips, E.J.P.; Siegel, D.I.

1989-01-01

THE contamination of sub-surface water supplies with aromatic compounds is a significant environmental concern1,2. As these contaminated sub-surface environments are generally anaerobic, the microbial oxidation of aromatic compounds coupled to nitrate reduction, sulphate reduction and methane production has been studied intensively1-7. In addition, geochemical evidence suggests that Fe(III) can be an important electron acceptor for the oxidation of aromatic compounds in anaerobic groundwater. Until now, only abiological mechanisms for the oxidation of aromatic compounds with Fe(III) have been reported8-12. Here we show that in aquatic sediments, microbial activity is necessary for the oxidation of model aromatic compounds coupled to Fe(III) reduction. Furthermore, a pure culture of the Fe(III)-reducing bacterium GS-15 can obtain energy for growth by oxidizing benzoate, toluene, phenol or p-cresol with Fe(III) as the sole electron acceptor. These results extend the known physiological capabilities of Fe(III)-reducing organisms and provide the first example of an organism of any type which can oxidize an aromatic hydrocarbon anaerobically. ?? 1989 Nature Publishing Group.

Chromium isotope fractionation in ferruginous sediments

NASA Astrophysics Data System (ADS)

Bauer, Kohen W.; Gueguen, Bleuenn; Cole, Devon B.; Francois, Roger; Kallmeyer, Jens; Planavsky, Noah; Crowe, Sean A.

2018-02-01

Ferrous Fe is a potent reductant of Cr(VI), and while a number of laboratory studies have characterized Cr isotope fractionation associated with Cr(VI) reduction by ferrous iron, the expression of this fractionation in real-world ferrous Fe-rich environments remains unconstrained. Here we determine the isotope fractionation associated with Cr(VI) reduction in modern ferrous Fe-rich sediments obtained from the previously well studied Lake Matano, Indonesia. Whole core incubations demonstrate that reduction of Cr(VI) within ferruginous sediments provides a sink for Cr(VI) leading to Cr(VI) concentration gradients and diffusive Cr(VI) fluxes across the sediment water interface. As reduction proceeded, Cr(VI) remaining in the overlying lake water became progressively enriched in the heavy isotope (53Cr), increasing δ53Cr by 2.0 ± 0.1‰ at the end of the incubation. Rayleigh distillation modelling of the evolution of Cr isotope ratios and Cr(VI) concentrations in the overlying water yields an effective isotope fractionation of εeff = 1.1 ± 0.2‰ (53Cr/52Cr), whereas more detailed diagenetic modelling implies an intrinsic isotope fractionation of εint = 1.80 ± 0.04‰. Parallel slurry experiments performed using anoxic ferruginous sediment yield an intrinsic isotope fractionation of εint = 2.2 ± 0.1‰. These modelled isotope fractionations are corroborated by direct measurement of the δ53Cr composition on the upper 0.5 cm of Lake Matano sediment, revealing an isotopic offset from the lake water of Δ53Cr = 0.21-1.81‰. The data and models reveal that effective isotope fractionations depend on the depth at which Cr(VI) reduction takes place below the sediment water interface-the deeper the oxic non-reactive zone, the smaller the effective fractionation relative to the intrinsic fractionation. Based on the geochemistry of the sediment we suggest the electron donors responsible for reduction are a combination of dissolved Fe(II) and 0.5 M HCl extractable (solid phase) Fe(II). Our results are in line with the range of intrinsic fractionation factors observed for such phases in previous laboratory studies. We suggest that intrinsic isotope fractionations of around 1.8‰, may be broadly characteristic of ferruginous environments, but we note that the partitioning of ferrous Fe between dissolved and solid phases may modulate this value. These results indicate that seawater δ53Cr is only captured with high-fidelity by ferruginous sediments when oxygen penetration, and therefore the upper boundary of the zone of Cr(VI) reduction, extends to more than 10 cm below the sediment-water-interface, as can be the case in sediments deposited below oligotrophic waters. In more productive regions, with thinner oxic zones, ferruginous sediments would record δ53Cr as much as 1.8‰ lower than seawater δ53Cr. This implies that a range of sediment δ53Cr compositions, that include that of the igneous silicate earth (ISE), are possible even when seawater is isotopically heavier than the ISE.

Geochemical, mineralogical and microbiological characteristics of sediment from a naturally reduced zone in a uranium-contaminated aquife

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

Campbell, K M; K Kukkadapu, R K; Qafoku, N P

2012-05-23

Localized zones or lenses of naturally reduced sediments have the potential to play a significant role in the fate and transport of redox-sensitive metals and metalloids in aquifers. To assess the mineralogy, microbiology and redox processes that occur in these zones, several cores from a region of naturally occurring reducing conditions in a U-contaminated aquifer (Rifle, CO) were examined. Sediment samples from a transect of cores ranging from oxic/suboxic Rifle aquifer sediment to naturally reduced sediment were analyzed for U and Fe content, oxidation state, and mineralogy; reduced S phases; and solid-phase organic C content using a suite of analyticalmore » and spectroscopic techniques on bulk sediment and size fractions. Solid-phase U concentrations were higher in the naturally reduced zone, with a high proportion of the U present as U(IV). The sediments were also elevated in reduced S phases and Fe(II), indicating it is very likely that U(VI), Fe(III), and SO4 reduction has occurred or is occurring in the sediment. The microbial community was assessed using lipid- and DNA-based techniques, and statistical redundancy analysis was performed to determine correlations between the microbial community and the geochemistry. Increased concentrations of solid-phase organic C and biomass in the naturally reduced sediment suggests that natural bioreduction is stimulated by a zone of increased organic C concentration associated with fine-grained material and lower permeability to groundwater flow. Characterization of the naturally bioreduced sediment provides an understanding of the natural processes that occur in the sediment under reducing conditions and how they may impact natural attenuation of radionuclides and other redox sensitive materials. Results also suggest the importance of recalcitrant organic C for maintaining reducing conditions and U immobilization.« less

Geochemical, mineralogical and microbiological characteristics of sediment from a naturally reduced zone in a uranium-contaminated aquifer

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

Campbell, K. M.; Kukkadapu, R. K.; Qafoku, N. P.

2012-08-01

Localized zones or lenses of naturally reduced sediments have the potential to play a significant role in the fate and transport of redox-sensitive metals and metalloids in aquifers. To assess the mineralogy, microbiology and redox processes that occur in these zones, several cores from a region of naturally occurring reducing conditions in a U-contaminated aquifer (Rifle, CO) were examined. Sediment samples from a transect of cores ranging from oxic/suboxic Rifle aquifer sediment to naturally reduced sediment were analyzed for U and Fe content, oxidation state, and mineralogy; reduced S phases; and solid-phase organic C content using a suite of analyticalmore » and spectroscopic techniques on bulk sediment and size fractions. Solid-phase U concentrations were higher in the naturally reduced zone, with a high proportion of the U present as U(IV). The sediments were also elevated in reduced S phases and Fe(II), indicating it is very likely that U(VI), Fe(III), and SO 4 reduction has occurred or is occurring in the sediment. The microbial community was assessed using lipid- and DNA-based techniques, and statistical redundancy analysis was performed to determine correlations between the microbial community and the geochemistry. Increased concentrations of solid-phase organic C and biomass in the naturally reduced sediment suggests that natural bioreduction is stimulated by a zone of increased organic C concentration associated with fine-grained material and lower permeability to groundwater flow. Characterization of the naturally bioreduced sediment provides an understanding of the natural processes that occur in the sediment under reducing conditions and how they may impact natural attenuation of radionuclides and other redox sensitive materials. Results also suggest the importance of recalcitrant organic C for maintaining reducing conditions and U immobilization.« less

Manganese and iron as oxygen carriers to anoxie estuarine sediment

NASA Astrophysics Data System (ADS)

Brayner, F. M. M.; Matvienko, B.

2003-05-01

We studied the concentration of a series of transition metals including Mn and Fe in an estuarine fishpond. The pond is situated at latitude 8°10'S and longitude 34°55'W, in the Capibaribe River estuary, within the Recife city boundaries, which is located in Pernambuco, a state of the Brazilian Northeast Pond area is 1.5 ha and it bas a 0.5 m depth. It is separated from the river by dikes. Water temperature at 28° C is stable throughout the year. Light breezes keep the water aerated, but intense ongoing decomposition makes the sediment anoxie. The area, originally of mangrove type, has been changed by antropic action on its fauna and vegetation. The study focuses on changes in behaviour of heavy metals. Samples of bottom sediments wore collected by Eckman dredge sediment sampler and total metal concentration was determined by the lithium borate fusion method. Water, recent sediment, and consolidated sediment were examined in this fishpond where Mn and Fe are brought in periodically by water and then gradually go into the sediment at respective rates of 10.52 and 1332 mg m^{-2}a^{-1}. Strong bioturbation re-suspends sediment while simultaneously re-dissolution of these ions is going on fhrough reduction in the anoxie sédiment. As soluble species these ions migrate from sediment to water and are there continually oxidized by dissolved oxygen, becoming insoluble. With their precipitation, chemically bound oxygen is carried down to the sediment, constituting a parallel channel of transport in addition to migration into the sediment bydiffusion of the oxygen dissolved in the water. The estimated flow rates are 3.25 and 76 mg O2 m^{-2}a^{-1} due to Mn and Fe respectively. The rates were established using natural silicon as a tracer.

Humic acids enhance the microbially mediated release of sedimentary ferrous iron.

PubMed

Chang, Chun-Han; Wei, Chia-Cheng; Lin, Li-Hung; Tu, Tzu-Hsuan; Liao, Vivian Hsiu-Chuan

2016-03-01

Iron (Fe) is an essential element for many organisms, but high concentrations of iron can be toxic. The complex relation between iron, arsenic (As), bacteria, and organic matter in sediments and groundwater is still an issue of environmental concern. The present study addresses the effects of humic acids and microorganisms on the mobilization of iron in sediments from an arsenic-affected area, and the microbial diversity was analyzed. The results showed that the addition of 50, 100, and 500 mg/L humic acids enhanced ferrous iron (Fe(II)) release in a time-dependent and dose-dependent fashion under anaerobic conditions. A significant increase in the soluble Fe(II) concentrations occurred in the aqueous phases of the samples during the first 2 weeks, and aqueous Fe(II) reached its maximum concentrations after 8 weeks at the following Fe(II) concentrations: 28.95 ± 1.16 mg/L (original non-sterilized sediments), 32.50 ± 0.71 mg/L (50 mg/L humic acid-amended, non-sterilized sediments), 37.50 ± 1.85 mg/L (100 mg/L humic acid-amended, non-sterilized sediments), and 39.00 ± 0.43 mg/L (500 mg/L humic acid-amended, non-sterilized sediments). These results suggest that humic acids can further enhance the microbially mediated release of sedimentary iron under anaerobic conditions. By contrast, very insignificant amounts of iron release were observed from sterilized sediments (the abiotic controls), even with the supplementation of humic acids under anaerobic incubation. In addition, the As(III) release was increased from 50 ± 10 μg/L (original non-sterilized sediments) to 110 ± 45 μg/L (100 mg/L humic acid-amended, non-sterilized sediments) after 8 weeks of anaerobic incubation. Furthermore, a microbial community analysis indicated that the predominant class was changed from Alphaproteobacteria to Deltaproteobacteria, and clearly increased populations of Geobacter sp., Paludibacter sp., and Methylophaga sp. were found after adding humic acids along with the increased release of iron and arsenic. Our findings provide evidence that humic acids can enhance the microbially mediated release of sedimentary ferrous iron in an arsenic-affected area. It is thus suggested that the control of anthropogenic humic acid use and entry into the environment is important for preventing the subsequent iron contamination in groundwater.

Distribution of chemical elements in calc-alkaline igneous rocks, soils, sediments and tailings deposits in northern central Chile

NASA Astrophysics Data System (ADS)

Oyarzún, Jorge; Oyarzun, Roberto; Lillo, Javier; Higueras, Pablo; Maturana, Hugo; Oyarzún, Ricardo

2016-08-01

This study follows the paths of 32 chemical elements in the arid to semi-arid realm of the western Andes, between 27° and 33° S, a region hosting important ore deposits and mining operations. The study encompasses igneous rocks, soils, river and stream sediments, and tailings deposits. The chemical elements have been grouped according to the Goldschmidt classification, and their concentrations in each compartment are confronted with their expected contents for different rock types based on geochemical affinities and the geologic and metallogenic setting. Also, the element behavior during rock weathering and fluvial transport is here interpreted in terms of the ionic potentials and solubility products. The results highlight the similarity between the chemical composition of the andesites and that of the average Continental Crust, except for the higher V and Mn contents of the former, and their depletion in Mg, Ni, and Cr. The geochemical behavior of the elements in the different compartments (rocks, soils, sediments and tailings) is highly consistent with the mobility expected from their ionic potentials, their sulfates and carbonates solubility products, and their affinities for Fe and Mn hydroxides. From an environmental perspective, the low solubility of Cu, Zn, and Pb due to climatic, chemical, and mineralogical factors reduces the pollution risks related to their high to extremely high contents in source materials (e.g., rocks, altered zones, tailings). Besides, the complex oxyanions of arsenic get bound by colloidal particles of Fe-hydroxides and oxyhydroxides (e.g., goethite), thus becoming incorporated to the fine sediment fraction in the stream sediments.

Characterisation of heavy metal-bearing phases in stream sediments of the Meža River Valley, Slovenia, by means of SEM/EDS analysis

NASA Astrophysics Data System (ADS)

Miler, M.; Gosar, M.

2010-02-01

Stream sediment reflects the rock structure of the catchment area, its geochemical characteristics and possible recent contamination upstream of the sampling point and thus, it is most frequently used in geochemical researches of heavy metal pollution. Stream sediment samples were collected along the Meža River and its tributaries and the Drava River, located in the NNE part of Slovenia. Previous geochemical studies have shown that these sediments are heavily polluted with heavy metals as a consequence of past mining of Pb-Zn ore and steelworks activities. Conventional geochemical analyses (ICP-MS, AAS, etc.) provided limited information on mineralogy, morphology and sources of heavy metal-bearing phases therefore SEM/EDS was utilized. Several problems were confronted with during EDS analysis, which are related to identification and quantification of light elements, identification of elements due to peak overlaps and quantification of spectra from unpolished samples. These problems were successfully dealt with. SEM/EDS enabled successful identification of heavy metal-bearing phases in stream sediments. Ore mineral phases, such as cerussite, sphalerite, smithsonite and galena, different heavy metal-bearing Fe-alloys, Fe-oxides and spherical particles and common rock-forming and accessory mineral phases, such as barite, rutile, ilmenite, zircon and monazite, were identified using solely SEM/EDS. These results were used for subsequent geochemical interpretation and source apportionment of heavy metals, according to associations of different heavy metal-bearing phases. Heavy metal-bearing phases were arranged by their source and genesis into three groups, denoted as geogenic/technogenic, technogenic and geogenic.

Mechanisms involved in phosphorus mobility at sediment/water interface under redox oscillations in dam-reservoir context

NASA Astrophysics Data System (ADS)

Rapin, Anne; Grybos, Malgorzata; Rabiet, Marion; Kestens, Tim; Mourier, Brice; Deluchat, Veronique

2017-04-01

The construction of dams, in response to the growing human demand of water and electricity, leads to the perturbation of several natural biogeochemical cycles, including phosphorus (P). Given its high affinity for solid phases, P tends to accumulate with the sediments in dam-reservoirs. Since the sedimentary P may contribute to water eutrophication, attention should be paid to better understand the parameters, conditions and mechanisms controlling the release of P at the sediment/water interface in such a system. The mobility of P at sediment/water interface closely depends on bio-physico-chemical conditions (redox potential, pH, temperature). Champsanglard dam-reservoir (19.5 m height; 55 ha; Creuse, France) was constructed in 1982 and is annually subject to bathing bans caused by the development of cyanobacteria, although the surface water is classified by the EU Water Framework Directive as being of medium quality regarding total dissolved P. The sediments accumulated in this reservoir are relatively rich in P (1.81 ± 0.22 mgP/gDW), in the silt-sand fraction and characterized by high organic matter content (21 ± 0.1 %). The development of temporary anoxia during summer in hypolimnion and P distribution in the sediments (66% of P associated with amorphous Mn/Fe-oxy-hydroxydes) highlight the importance of the redox potential variation on P mobility. In this context, incubation experiments were conducted to evaluate the role of alternation between aerobic and anaerobic conditions on P sediment mobility. Surface sediments (Φ<2 mm) were incubated with a synthetic solution simulating the chemistry of Champsanglard reservoir water and submitted to two successive aerated and non-aerated phases. Physico-chemical composition (pH, Eh, P-PO43-, FeII, Mn, NO3-, SO42- and dissolved organic carbon (DOC)) and organic matter aromaticity (SUVA254) of the supernatant were monitored all along the incubation. The results showed that the development of anaerobic conditions (decrease of redox potential, NO3- and SO42- and increase of FeII and Mn concentrations) during the two non-aerated phases induces the release of P to the solution. However, during the second anaerobic phase, a higher release of 57 % P- PO43- was observed (8.7 ± 0.5 mgP/L for the second phase to 6.4 ± 0.5 mgP/L for the first one). During the first anaerobic phase, P-PO43- dynamic was correlated with the release of FeII and Mn suggesting that the reductive dissolution of Mn/Fe-oxy-hydroxydes was the main mechanism controlling the P mobility. However, in the second anaerobic phase, Mn and FeII concentrations were much lower (respectively of 24 % and 56 %) than in the first anaerobic phase. SUVA254 index showed that organic compounds released in the first cycle were less aromatic than in the second cycle and exhibited the geochemical characteristics of microbial metabolites (in opposition to humic substances in the second cycle). According to Pan et al. (2016), aromatic organic matter could limit reductive dissolution of Fe-oxyhydroxydes and involve competition for P sorption sites. This experiment highlighted that organic matter quality plays together with Mn/Fe-oxy-hydroxydes an important role in P mobility at sediment/water interface in dam-reservoirs. Keywords: Phosphorus; Sediment; Redox-oscillations; Dam reservoir; Mechanisms

Decoupling of As and Fe release to Bangladesh groundwater under reducing conditions. Part I: Evidence from sediment profiles

NASA Astrophysics Data System (ADS)

Horneman, A.; van Geen, A.; Kent, D. V.; Mathe, P. E.; Zheng, Y.; Dhar, R. K.; O'Connell, S.; Hoque, M. A.; Aziz, Z.; Shamsudduha, M.; Seddique, A. A.; Ahmed, K. M.

2004-09-01

This study reexamines the notion that extensive As mobilization in anoxic groundwater of Bangladesh is intimately linked to the dissolution of Fe oxyhydroxides on the basis of analyses performed on a suite of freshly collected samples of aquifer material. Detailed sediment profiles extending to 40 to 70 m depth below the surface were obtained at six sites where local groundwater As concentrations were known to span a wide range. The sediment properties that were measured include (1) the proportion of Fe(II) in the Fe fraction leached in hot 1.2 N HCl, (2) diffuse spectral reflectance, and (3) magnetic susceptibility. In parallel with local concentrations of dissolved As ranging from <5 to 600 μg/L, Fe(II)/Fe ratios in shallow (gray) Holocene sands tended to gradually increase with depth from values of 0.3 to 0.5 to up to 0.9. In deeper (orange) aquifers of presumed Pleistocene age that were separated from shallow sands by a clay layer and contained <5 μg/L dissolved As, leachable Fe(II)/Fe ratios averaged ˜0.2. There was no consistent relation between sediment Fe(II)/Fe and dissolved Fe concentrations in groundwater in nearby wells. The reflectance measurements indicate a systematic linear relation (R 2 of 0.66; n = 151) between the first derivative transform of the reflectance at 520 nm and Fe(II)/Fe. The magnetic susceptibility of the shallow aquifer sands ranged from 200 to 3600 (x 10 -9 m 3/kg SI) and was linearly related (R 2 of 0.75; n = 29) to the concentrations of minerals that could be magnetically separated (0.03 to 0.79% dry weight). No systematic depth trends in magnetic susceptibility were observed within the shallow sands, although the susceptibility of deeper low-As aquifers was low (up to ˜200 × 10 -9 m 3/kg SI). This set of observations, complemented by incubation results described in a companion paper by van Geen et al. (this volume), suggests that the release of As is linked to the transformation of predominantly Fe (III) oxyhydroxide coatings on sand particles to Fe(II) or mixed Fe(II/III) solid phases with a flatter reflectance spectrum such as siderite, vivianite, or magnetite, without necessarily resulting in the release of Fe to groundwater. The very low As/Fe ratio of magnetically separated minerals compared to the As/Fe of bulk acid leachate (2 vs. 40 10 -6, respectively) suggests that such a transformation could be accompanied by a significant redistribution of As to a mobilizable phase on the surface of aquifer particles.

Microbial reduction of manganese oxides - Interactions with iron and sulfur

NASA Technical Reports Server (NTRS)

Myers, Charles R.; Nealson, Kenneth H.

1988-01-01

Alteromonas putrefaciens (strain MR-1) is capable of rapid Mn(IV) reduction under conditions of neutral pH and temperatures characteristic of the Oneida Lake, New York, sediments from which it was isolated. MR-1 also reduces Fe(3+) to Fe(2+), and disproportionates thiosulfate to sulfide and sulfite; independently, the Fe(2+) and sulfide act as rapid reductants of Mn. The addition of Fe(3+) or thiosulfate to cultures of MR-1 in the presence of oxidized Mn increases the rate and the extent of Mn reduction relative to that observed in the absence of Fe(3+) or thiosulfate. Furthermore, when Fe(3+) and Mn oxides are present conjointly, Fe(2+) does not appear until the reduction of the oxidized Mn is complete. These results demonstrate that the observed rates of Fe(2+) and sulfide production may underestimate the total rates of Fe and sulfate reduction in those environments containing oxidized Mn. These results also demonstrate the potential impact that a single microbe can exert on sediment geochemistry, and provide the basis for preliminary models of the complexity of microbial and geochemical interactions that occur.

Response of sediment microbial community structure in a freshwater reservoir to manipulations in oxygen availability.

PubMed

Bryant, Lee D; Little, John C; Bürgmann, Helmut

2012-04-01

Hypolimnetic oxygenation systems (HOx) are being increasingly used in freshwater reservoirs to elevate dissolved oxygen levels in the hypolimnion and suppress sediment-water fluxes of soluble metals (e.g. Fe and Mn) which are often microbially mediated. We assessed changes in sediment microbial community structure and corresponding biogeochemical cycling on a reservoir-wide scale as a function of HOx operations. Sediment microbial biomass as quantified by DNA concentration was increased in regions most influenced by the HOx. Following an initial decrease in biomass in the upper sediment while oxygen concentrations were low, biomass typically increased at all depths as the 4-month-long oxygenation season progressed. A distinct shift in microbial community structure was only observed at the end of the season in the upper sediment near the HOx. While this shift was correlated to HOx-enhanced oxygen availability, increased TOC levels and precipitation of Fe- and Mn-oxides, abiotic controls on Fe and Mn cycling, and/or the adaptability of many bacteria to variations in prevailing electron acceptors may explain the delayed response and the comparatively limited changes at other locations. While the sediment microbial community proved remarkably resistant to relatively short-term changes in HOx operations, HOx-induced variation in microbial structure, biomass, and activity was observed after a full season of oxygenation. © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

[Mechanism of phosphorus adsorption and immobility by sediments in innercity heavily polluted canal].

PubMed

Li, Da-Peng; Huang, Yong; Yuan, Yan; Fan, Cheng-Xin

2011-01-01

The mechanisms of phosphorus (P) adsorption and immobility were investigated in laboratory experiments. The sediments and waters used were taken from an inner-city heavily polluted canal. Addition of KH2PO4 into the operated experimental units, with and without (i.e., static) intermittent sediment resuspension, were made similar to the external P input and carried out periodically. The results show that the amount of the accumulative P adsorption onto the sediments was up to 363.4 mg x kg(-1) under the conditions of sediment disturbance over a 39-day period, and it was evidently higher than that (213.2 mg x kg(-1)) under static conditions. Sequential fractionation indicated that most of the incorporated P was accounted for in the Fe/Al-P. There were over 61% in the case of intermittent sediment disturbance and up to 83% in the case of static conditions. Based on the bioavailability of Fe/Al-P, 40.6% of the incorporated P was accounted for in non-occluded Fe/Al-P of the sediments under intermittent sediment disturbance conditions. This value increased to 59.5% under static conditions. In addition, more than 23% of the incorporated P was accounted for in HCl-P of the sediments under intermittent sediment disturbance conditions, on the other hand, the concentration of HCl-P kept relatively constant under static conditions. After 39 d of P adsorption by the both sediments, the values of the maximum sorption capacity (S(max)) decreased,while zero equilibrium P concentration (EPC0) and P saturation P(%) increased. However, the extent of EPC0 and P% under intermittent sediment disturbance conditions was obviously lower than that under static conditions. It was hopefully suggested that intermittent sediment disturbance can not only accelerate the P adsorption but also enhance the P retention by sediments.

Effects of bottom water dissolved oxygen variability on copper and lead fractionation in the sediments across the oxygen minimum zone, western continental margin of India.

PubMed

Chakraborty, Parthasarathi; Chakraborty, Sucharita; Jayachandran, Saranya; Madan, Ritu; Sarkar, Arindam; Linsy, P; Nath, B Nagender

2016-10-01

This study describes the effect of varying bottom-water oxygen concentration on geochemical fractionation (operational speciation) of Cu and Pb in the underneath sediments across the oxygen minimum zone (Arabian Sea) in the west coast of India. Both, Cu and Pb were redistributed among the different binding phases of the sediments with changing dissolved oxygen level (from oxic to hypoxic and close to suboxic) in the bottom water. The average lability of Cu-sediment complexes gradually decreased (i.e., stability increased) with the decreasing dissolved oxygen concentrations of the bottom water. Decreasing bottom-water oxygen concentration increased Cu association with sedimentary organic matter. However, Pb association with Fe/Mn-oxyhydroxide phases in the sediments gradually decreased with the decreasing dissolved oxygen concentration of the overlying bottom water (due to dissolution of Fe/Mn oxyhydroxide phase). The lability of Pb-sediment complexes increased with the decreasing bottom-water oxygen concentration. This study suggests that bottom-water oxygen concentration is one of the key factors governing stability and lability of Cu and Pb complexes in the underneath sediment. Sedimentary organic matter and Fe/Mn oxyhydroxide binding phases were the major hosting phases for Cu and Pb respectively in the study area. Increasing lability of Pb-complexes in bottom sediments may lead to positive benthic fluxes of Pb at low oxygen environment. Copyright © 2016 Elsevier B.V. All rights reserved.

Influence of AOM on iron-sulfur-carbon systematics in marine sediment: A study from Krishna-Godavari basin, Bay of Bengal

NASA Astrophysics Data System (ADS)

Carvalho, M. A.

2017-12-01

Sedimentary diagenetic processes play key role in global sulfur-iron-carbon cycle. Microbially driven organoclastic sulfate reduction and anaerobic oxidation of methane (AOM) pathways are responsible for sulfate reduction in marine sediments. Concomitant H2S production and iron sulfide precipitation lead to Fe-sulfide burial in the sediments. Intra/intermolecular organic bound sulfur is also another major sink of global sulfur burial. In the present study, we have investigated the sulfidisation process in a core from Krishna-Godavari (K-G) basin, Bay of Bengal. K-G basin is well known for gas hydrate deposits and methane enrichment within 100-120 mbsf. Previous work from K-G basin has shown tell-tale evidence of paleo episodic- methane expulsion events and formation of authigenic carbonate crust at or above the sea floor1. Our study was carried out on a core MD-161-15 (water depth of 983 m and Lat. =16° 00.5700' N;Long. = 82° 03.4502' E) recovered on board R/V Marion Dufrense). The pyrite content in the core (measured as chromium reducible sulfur: CRS) range from 0.003 to 1.1 wt%. The reactive content (FeTR = FeOx + FeD + FeCRS) range from 0.9 to 3.5 wt%, where FeOX, FeD and FeCRS represents oxalate extractable (magnetite), buffered dithionite extractable (ferrihydrite, lepidocrocite, goethite, hematite) and boiling CrCl2 (in 6N HCl) extractable (Pyrite: FeS2) iron respectively. The δ34SCRS range from -49 to +16.7 ‰ VCDT and show good positive correlation with FeTR. Presence of highly 13C depleted authigenic carbonate in the sediments within 1600-3000 mbsf indicate influence of AOM and possible methane seepage2. The δ34SCRS profile show marked 34S depletion trend within the top 1012 mbsf. Below this depth, δ34SCRS values show steadily increasing trend superimposed by zones of sharp enrichment/ depletion of 34S. The 34S enrichment trend may attributed to late diagenetic pyritization from 34S enriched H2S produced from residual pore water sulfate via AOM pathway.

Occurrence of phosphorus, iron, aluminum, silica, and calcium in a eutrophic lake during algae bloom sedimentation.

PubMed

Li, Guolian; Xie, Fazhi; Zhang, Jin; Wang, Jingrou; Yang, Ying; Sun, Ruoru

2016-09-01

Phosphorus (P) in a water body is mainly controlled by the interaction between surface sediment and the overlying water column after the complete control of external pollution. Significant enhancement of P in a water body would cause eutrophication of lakes. Thus, a better understanding is needed of the occurrences of P between the sediment and water column in eutrophic lakes. Here, we measured total phosphorus (TP) and major elements (Fe, Al, Ca, Mn, Si) in the water column, and total nitrogen, organic matter, TP and major oxides (Fe 2 O 3 , Al 2 O 3 , CaO, SiO 2 ) in surface sediment of Chaohu Lake, a continuously eutrophic lake. The results showed that the rank of TP levels was western lake > eastern lake > southern lake. There were significantly positive correlations between TP (including water TP and sedimentary TP) and Fe, Al, Mn, while the correlation coefficients between water TP and sedimentary TP were -0.43, -0.41 and 0.18 for the western, eastern and southern lake respectively. The negative and significant correlations of water TP and sedimentary TP may indicate that the risk of sedimentary P release was great in the western and eastern lake during algae bloom sedimentation, while the southern lake showed weak P exchange between the sediment and water column.

Micro-spatial variation of elemental distribution in estuarine sediment and their accumulation in mangroves of Indian Sundarban.

PubMed

Bakshi, Madhurima; Ram, S S; Ghosh, Somdeep; Chakraborty, Anindita; Sudarshan, M; Chaudhuri, Punarbasu

2017-05-01

This work describes the micro-spatial variation of elemental distribution in estuarine sediment and bioaccumulation of those elements in different mangrove species of the Indian Sundarbans. The potential ecological risk due to such elemental load on this mangrove-dominated habitat is also discussed. The concentrations of elements in mangrove leaves and sediments were determined using energy-dispersive X-ray fluorescence spectroscopy. Sediment quality and potential ecological risks were assessed from the calculated indices. Our data reflects higher concentration of elements, e.g., Al, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, and Pb, in the sediment, as compared to that reported by earlier workers. Biological concentration factors for K, Ca, Mn, Fe, Cu, and Zn in different mangroves indicated gradual elemental bioaccumulation in leaf tissues (0.002-1.442). Significant variation was observed for elements, e.g., Ni, Mn, and Ca, in the sediments of all the sites, whereas in the plants, significant variation was found for P, S, Cl, K, Ca, Mn, Fe, Cu, and Zn. This was mostly due to the differences in uptake and accumulation potential of the plants. Various sediment quality indices suggested the surface sediments to be moderately contaminated and suffering from progressive deterioration. Cu, Cr, Zn, Mn, and Ni showed higher enrichment factors (0.658-1.469), contamination factors (1.02-2.7), and geo-accumulation index (0.043-0.846) values. The potential ecological risk index values considering Cu, Cr, Pb, and Zn were found to be within "low ecological risk" category (20.04-24.01). However, Cr and Ni in the Sundarban mangroves exceeded the effect range low and probable effect level limits. Strong correlation of Zn with Fe and K was observed, reflecting their similar transportation and accumulation process in both sediment and plant systems. The plant-sediment elemental correlation was found to be highly non-linear, suggesting role of some physiological and edaphic factors in the accumulation process. Overall, the study of micro-spatial distribution of elements can act as a useful tool for determining health of estuarine ecosystem.

Implication of the monomineral eclogite thermobarometry for the reconstruction of the PT conditions and origin of mantle eclogites in the structure of Siberian and other cratons.

NASA Astrophysics Data System (ADS)

Ashchepkov, Igor; Logvinova, Alla; Spetsius, Zdislav; Ntaflos, Theodoros; Ravi, Subramanaian; Vladykin, Nikolai; Stegnitsky, Yuri; Babushkina, Svetlana; Ovchinnikov, Yuri

2016-04-01

Enhanced monomineral thermobarometry for clinopyroxenes and garnet (Ashchepkov et al., 2015) allow reconstruction of thermal conditions for the mantle eclogitic xenoliths and xenocrysts of omphacites and pyrope almandine garnets of eclogitic and megacrystic types. Three common groups according to Dawson,(1977) A. Mg - eclogites; B. common subduction-related basaltic eclogites and C. Na-Fe- rich eclogites. In addition group D compile Ca-Al rich varieties (Spetsius et al., 2008; Viljoen et al., 2010). We subdivided these groups and their positions in mantle lithosphere sections beneath the most studied pipes in Yakutia and most interesting localities Worldwide. Group A including Al-rich and low groups are restites or cumulates from the ancient komatiitic basalts or boninites. The Fe# for olivine in equilibrium is 0.05 -0.11 using melt -solid partition coefficient ~0.33 for Fe (Albarede, 1992). For the group B Fe# of the omphacites are ~ 0.11- 0.23 and they could be only cumulates from melted subducted MORB basalts or reactional products. The higher values of Fe -Na-Al rich group C (Fe# ~0.25-0.4) could relate to the subducted basalts or Al - rich sediments (Spetsius et al., 2008) or Mg-rich crustal rocks which were subducted without much melting. Group D Ca-rich eclogites are commonly low Fe but subduction related varieties (Dongre et al., 2015) could be higher in Fe and Na. Partition coefficients of the trace elements between Gar and Cpx for most mantle eclogites relate to equilibration with the melts and REE patterns show different inclinations, while crustal eclogites which re-equilibrated in the solid state often show the same inclinations. Groups A1: a Cr-bearing group formed after crystallization of partial melts produced by volatile fluxes generated by ancient subduction (Heaman et al., 2006; Smart et al., 2009); A2 - low - Al cumulates and restites from komatiitic melts (Aulbach et al., 2011); A3 - low-Cr group which could be restites (Wyman and Kerrich, 2009) or deep cumulates from tonalite- trondhjemite or Mg-rich boninitic arc magmas (Horodytskyi et al., 2007; Barth et al., 2002); A4 a group derived by crystallization of differentiated protokimberlite melts (Haggerty et al., 1979; Kamenetsky et al., 2009). The largest group B with Fe# (~ 0.15-0.25, moderate in Al and Na values, commonly reveal Eu anomalies. The GrB1 interpreted as subducted metagrabbro close to MORB (Jagoutz et al., 1974; Beard et al., 1996; Pearson, 1995; Snyder et al., 1997) reacted with oceanic water (Neal et al., 1990). Enriched Group B2 eclogites are thought to be products of fluid melting of ancient oceanic crust and interaction with peridotites during subduction (Aulbach et al., 2007). Group B3 eclogites (>3 GPa) may be basaltic cumulates derived from plume or ancient arc magmas in cratonic margins (Wyman and Kerrich, 2009); those near Moho may be eclogitized lower crustal cumulates (Shu et al., 2014). Group B4 eclogites are results of hybridization of subducted basalts with protokimberlite and other plume melts (Shatsky et al., 2008 -2015). High-Fe -Na Group C1 eclogites (Fe# > 0.27) may be subducted Fe- basalts; Ca-enriched varieties may be meta-tonalites or trondhjemites (Group C2) (Barth et al., 2002) and those which are very rich in Al could be metasediments (Group C3) (Mazzone and Haggerty, 1989). High -Ca- Al GrD1 are rare high-Ca and low-Fe varieties, commonly Al-rich and kyanite-bearing (sometimes with coesite) (grosspydites) which may be originally carbonate metasomatites (Smyth, 1977) or metapelites (Liou et al., 2014); Group GrD3 eclogites are high-Ca and moderate-Fe and may be ancient Mg-granites (Barth et al., 2002; Jacob et al., 2003) . According to the thermobarometry GrA eclogites are distributed mostly in the lower (L) and- middle parts of SCLM and correspond to low - temperature thermal gradients. GrB2 eclogites form trends of increasing Fe# for garnets and omphacites with decreasing pressure. This could be due to the progressive melting of subducted basalts (Rosenthal et al., 2014) or an opposite due to crystallization of evolving partial melts from primary eclogites. In USCLM the GrB3 omphacites show reactional trends with decreasing Fe# upward or an opposite progressive rise due to magmatic differentiation. GrC dominate the middle part of the SCLM (3-4 GPa) and mostly correspond to the layer originated in the Early Archean time at 3.5-4.0 GPa possibly due to subduction of the tonalitic crust and related metasediments. CrD1 -rich grosspyditic varieties from India, Siberia and South Africa are relatively low-Fe and Al-rich and possibly are metasomatites or products of interaction of sediments and peridotites. The other Ca- rich varieties most likely are subducted anorthosites or rare granites. Supported by the RFBR grants: 05-05-64718, 03-05-64146, 11 -05-00060, 11-05-91060-PICS, 16-05-00841, 16-05-00860 and projects 77-2, 65-03, 02-05 UIGGM SB RAS and ALROSA Stock Company

Chloroethene Biodegradation Potential, ADOT/PF Peger Road Maintenance Facility, Fairbanks, Alaska

USGS Publications Warehouse

Bradley, Paul M.; Chapelle, Frances H.

2004-01-01

A series of 14C-radiotracer-based microcosm experiments were conducted to assess: 1) the extent, rate and products of microbial dechlorination of trichloroethene (TCE), cis-dichloroethene (cis-DCE) and vinyl chloride (VC) in sediments at the Peger Road site; 2) the effect of three electron donor amendments (molasses, shrimp and crab chitin, and 'Hydrogen Release Compound' (HRC)) on microbial degradation of TCE in three Peger Road sediments; and 3) the potential significance at the site of chloroethene biodegradation processes other than reductive dechlorination. In these experiments, TCE biodegradation yielded the reduced products, DCE and VC, and the oxidation product CO 2. Biodegradation of DCE and VC involved stoichiometric oxidation to CO 2. Both laboratory microcosm study and field redox assessment results indicated that the predominant terminal electron accepting process in Peger Road plume sediments under anoxic conditions was Mn/Fe-reduction. The rates of chloroethene biodegradation observed in Peger Road sediment microcosms under low temperature conditions (4?C) were within the range of those observed in sediments from temperate (20?C) aquifer systems. This result confirmed that biodegradation can be a significant mechanism for in situ contaminant remediation even in cold temperature aquifers. The fact that CO2 was the sole product of cis-DCE and VC biodegradation detected in Peger Road sediments indicated that a natural attenuation assessment based on reduced daughter product accumulation may significantly underestimate the potential for DCE and VC biodegradation at the Peger Road. Neither HRC nor molasses addition stimulated TCE reductive dechlorination. The fact that molasses and HRC amendment did stimulate Mn/Fe-reduction suggests that addition of these electron donors favored microbial Mn/Fe-reduction to the detriment of microbial TCE dechlorinating activity. In contrast, amendment of sediment microcosms with shrimp and crab chitin resulted in the establishment of mixed Mn/Fe-reducing, SO42--reducing and methanogenic conditions and enhanced TCE biodegradation in two of three Peger Road sediment treatments.

A comparison of microbial communities in deep-sea polymetallic nodules and the surrounding sediments in the Pacific Ocean

NASA Astrophysics Data System (ADS)

Wu, Yue-Hong; Liao, Li; Wang, Chun-Sheng; Ma, Wei-Lin; Meng, Fan-Xu; Wu, Min; Xu, Xue-Wei

2013-09-01

Deep-sea polymetallic nodules, rich in metals such as Fe, Mn, and Ni, are potential resources for future exploitation. Early culturing and microscopy studies suggest that polymetallic nodules are at least partially biogenic. To understand the microbial communities in this environment, we compared microbial community composition and diversity inside nodules and in the surrounding sediments. Three sampling sites in the Pacific Ocean containing polymetallic nodules were used for culture-independent investigations of microbial diversity. A total of 1013 near full-length bacterial 16S rRNA gene sequences and 640 archaeal 16S rRNA gene sequences with ~650 bp from nodules and the surrounding sediments were analyzed. Bacteria showed higher diversity than archaea. Interestingly, sediments contained more diverse bacterial communities than nodules, while the opposite was detected for archaea. Bacterial communities tend to be mostly unique to sediments or nodules, with only 13.3% of sequences shared. The most abundant bacterial groups detected only in nodules were Pseudoalteromonas and Alteromonas, which were predicted to play a role in building matrix outside cells to induce or control mineralization. However, archaeal communities were mostly shared between sediments and nodules, including the most abundant OTU containing 290 sequences from marine group I Thaumarchaeota. PcoA analysis indicated that microhabitat (i.e., nodule or sediment) seemed to be a major factor influencing microbial community composition, rather than sampling locations or distances between locations.

Comparison of elemental accumulation rates between ferromanganese deposits and sediments in the South Pacific Ocean

USGS Publications Warehouse

Kraemer, T.; Schornick, J.C.

1974-01-01

Rates of accumulation of Fe and Mn, as well as Cu, Ni, Co, Pb, Zn, Hg, U and Th have been determined for five ferromanganese deposits from four localities in the South Pacific Ocean. Manganese is accumulating in nodules and crusts at a rate roughly equivalent to that found to be accumulating in sediments in the same area. Iron shows a deficiency in accumulation in nodules and crusts with respect to sediments, especially near the continents, but also in the central and south-central Pacific. Copper is accumulating in nodules and crusts at a rate one order of magnitude less than the surrounding sediments. This is interpreted as meaning that most of the Mn is supplied as an authigenic phase to both sediments and nodules while Fe is supplied mostly by ferromanganese micro-nodules and by detrital and adsorbed components of sediments; and Cu is enriched in sediments relative to nodules and crusts most probably through biological activity. ?? 1974.

V isotope composition in modern marine hydrothermal sediments

NASA Astrophysics Data System (ADS)

Wu, F.; Owens, J. D.; Nielsen, S.; German, C. R.; Rachel, M.

2017-12-01

Vanadium is multivalence transition metal with two isotopes (51V and 50V). Recent work has shown that large V isotope variations occur with oxygen variations in modern sediments (Wu et al., 2016 and 2017 Goldschmidt Abstracts), providing its potential as a promising proxy for determining low oxygen conditions. However, the development of V isotopes as a proxy to probe past redox conditions requires a comprehensive understanding of the modern oceanic isotopic mass balance. Therein, the scavenging of V from the hydrous iron oxides in hydrothermal fluid has been shown to be an important removal process from seawater (Rudnicki and Elderfield, 1993 GCA) but remains unquantified. In this study, we analyzed V isotopic compositions of metalliferous sediments around the active TAG hydrothermal mound from the mid-Atlantic Ridge (26° degrees North) and the Eastern Pacific Zonal Transect (GEOTRACES EPZT cruise GP16). The TAG sediments deposited as Fe oxyhydroxides from plume fall-out, and have δ51V values between -0.3 to 0‰. The good correlation between Fe and V for these metalliferous sediments indicate that the accumulation of V in these samples is directly related to the deposition of Fe oxyhydroxides, which also control their V isotope signature. The EPZT samples cover 8,000 km in the South Pacific Ocean with sedimentary areas that underlie the Peru upwelling region and the well-oxygenated deep South Pacific Ocean influenced by hydtorthermal plume material from southern East Pacific Rise (EPR). The sediments collected at the east of the EPR have δ51V values between -1.2 to -0.7‰, similar to previous δ51V of oxic sediments. In contrast, the sediments from the west of the EPR have δ51V values (-0.4 to 0‰) similar to hydrothermal sediments from the mid-Atlantic Ridge, indicating the long transportation (more than 4,000 km, Fitzsimmons et al., 2017 NG) of Fe and Mn from hydrothermal plume and their incorporation into sediments have a major impact on the cycle of V in the ocean. The fingerprint of δ51V between oxic sediments and hydrothermal flux are significantly different and should be easily discernible in the geologic record. Consequently, our results show that the removal of V from hydrothermal sediments has an important influence on the marine V cycle, which needs to be considered for future modern and paleoclimatic studies.

Roles of Ferrous and Sulfide Ions in the Fromation of Algae—Induced Black Bloom in Hyper Eutrophic Freshwater Lakes in China

NASA Astrophysics Data System (ADS)

Shen, Q.; Gao, Q.; Yu, C.; Zhang, L.; Wang, Z.

2016-12-01

Water column hypoxia is one of the most serious threats from eutrophication to large water bodies. In the past several years, black bloom phenomenon has become a serious ecosystem disaster in some important severe eutrophic lakes in China, which caused not only environment degradation but also drinking water crisis. Black color and offensive odour of the water column are two notorious sensory features. High Fe2+ and ΣH2S (ΣS2-=S2-+HS-+H2S) were typical characteristics of the black bloom water. Analysis of the black substances of the black bloom water using X-ray photoelectron spectroscopy indicated that abundant FeS were included in these particulates. The black color of the black bloom water could be attributed to the formation of FeS in the anoxic/anaerobic water column. Field investigation and laboratory incubation experiment indicated that the formation of black bloom was closely related to the Fe2+ and ΣH2S in surface sediments. The Fe2+ concentration in surface sediment pore water was high and showed a release tendency from the sediment water interface to the overlying water during the formation of black bloom, while the similar trend was found in ΣH2S production at sediment water micro-interface. Both Fe2+ and ΣS2- affected by oxic and redox conditions, respectively, contributed to the formation of black bloom significantly. However, ΣS2- was found to be the limiting factor directly controlling the outbreak of black bloom. Analysis of microbioal community diversity demonstrated that sulfate reducing bacteria (SRB) were abundant in the surface sediment of black bloom, which strongly influenced the production and accumulation of ΣH2S and drove the formation of black bloom.

[Characterization and optimization of the NaOH-EDTA extracts for solution 31P-NMR analysis of organic phosphorus in river sediments].

PubMed

Zhang, Wen-Qiang; Shan, Bao-Qing; Zhang, Hong; Tang, Wen-Zhong

2014-01-01

Optimization and mechanism of NaOH-EDTA extraction solutions were studied in phosphorus (P) pollution river sediments, which were Fe, Al-rich sediment, by solution 31P nuclear magnetic resonance spectroscopy (31P-NMR). Different proportions of NaOH and EDTA showed different extraction efficiency on total P (TP) and organic P (Po) in the sediment. The concentration of Po in NaOH + EDTA extract was higher than that in NaOH extract. The mechanism was that the TP and Po were released under the conditions of EDTA chelating with Fe and Al. The concentration of TP and Po were the highest in 1.00 mol x L(-1) NaOH +75 mmol x L(-1) EDTA extract and 0.25 mol x L(-1) NaOH + 50 mmol x L(-1) EDTA extract, which were 3.88 mg x g(-1) and 0.24 mg x g(-1), respectively. The extractions of Fe, Mn, Ca, Mg, Al were increasing as the EDTA increased under the same NaOH concentration. Extraction efficiency of Fe, Mn, Ca showed negative correlation with the pH of the extracting solution (P < 0.01). Exponential relationship was found between the extraction of Al and the pH of the extraction solution (P < 0.01) because of the AlO2- and EDTA-Al complex. The quality of spectra of NaOH-EDTA extract was better than that of NaOH extract. Six P species were detected in different extractions, including phosphonates, orthophosphate, pyrophosphate, orthophosphate monoesters, phospholipids and deoxyribonucleic acids. Therefore, 0. 25 mol x L(-1) NaOH + 50 mmol x L(-1) EDTA was the optimization extraction solution for Po analysis in Fe and Al-rich river sediment by 31P-NMR.

Toxic trace element assessment for soils/sediments deposited during Hurricanes Katrina and Rita from southern Louisiana, USA: a sequential extraction analysis.

PubMed

Shi, Honglan; Witt, Emitt C; Shu, Shi; Su, Tingzhi; Wang, Jianmin; Adams, Craig

2010-07-01

Analysis of soil/sediment samples collected in the southern Louisiana, USA, region three weeks after Hurricanes Katrina and Rita passed was performed using sequential extraction procedures to determine the origin, mode of occurrence, biological availability, mobilization, and transport of trace elements in the environment. Five fractions: exchangeable, bound to carbonates, bound to iron (Fe)-manganese (Mn) oxides, bound to organic matter, and residual, were subsequently extracted. The toxic trace elements Pb, As, V, Cr, Cu, and Cd were analyzed in each fraction, together with Fe in 51 soil/sediment samples. Results indicated that Pb and As were at relatively high concentrations in many of the soil/sediment samples. Because the forms in which Pb and As are present tend to be highly mobile under naturally occurring environmental conditions, these two compounds pose an increased health concern.Vanadium and Cr were mostly associated with the crystal line nonmobile residual fraction. A large portion of the Cu was associated with organic matter and residual fraction. Cadmium concentrations were low in all soil/sediment samples analyzed and most of this element tended to be associated with the mobile fractions. An average of 21% of the Fe was found in the Fe-Mn oxide fraction, indicating that a substantial part of the Fe was in an oxidized form. The significance of the overall finding of the present study indicated that the high concentrations and high availabilities of the potentially toxic trace elements As and Pb may impact the environment and human health in southern Louisiana and, in particular, the New Orleans area. Copyright (c) 2010 SETAC.

Diffuse-flow hydrothermal field in an oceanic fracture zone setting, Northeast Pacific: Deposit composition

USGS Publications Warehouse

Hein, J.R.; Koski, R.A.; Embley, R.W.; Reid, J.; Chang, S.-W.

1999-01-01

This is the first reported occurrence of an active hydrothermal field in an oceanic fracture zone setting. The hydrothermal field occurs in a pull-apart basin within the Blanco Fracture Zone (BFZ), which has four distinct mineral deposit types: (1) barite mounds and chimneys, (2) barite stockwork breccia, (3) silica-barite beds, and (4) silica, barite, and Fe-Mn oxyhydroxide in sediments. All deposit types contain minor amounts of sulfides. In barite stockwork, silica-barite beds, and mineralized sediment, Ba, Ph, Ag, S, Au, Zn, Cu, Hg, TI, As, Mo, Sb, U, Cd, and Cu are enriched relative to unmineralized rocks and sediments of the BFZ. Fe and Mn are not enriched in the barite stockwork or silica-barite beds, but along with P, Co, and Mg are enriched in the mineralized sediments. Silver contents in deposits of the hydrothermal field range up to 86 ppm, gold to 0.7 ppm, zinc to 3.2%, copper to 0.8%, and barium to 22%. Mineralization occurred by diffuse, low to intermediate temperature (mostly <250??C) discharge of hydrothermal fluids through pillow lavas and ponds of mixed volcaniclastic and biosiliceous sediments. Bacterial mats were mineralized by silica, barite, and minor Fe hydroxides, or less commonly, by Mn oxyhydroxides. Pervasive mineralization of bacterial mats resulted in formation of silica-barite beds. Silica precipitated from hydrothermal fluids by conductive cooling and mixing with seawater. Sulfate, U, and rare earth elements (REEs) in barite were derived from seawater, whereas the REE content of hydrothermal silica deposits and mineralized sediments is associated with the aluminosilicate detrital fraction. Fe-, Zn-, Cu-, Pb-, and Hg-sulfide minerals, Ba in barite, and Eu in all mineralized deposits were derived from hydrothermal fluids. Manganese oxides and associated elements (Co, Sb, Mo, W, Cl, and Cu) and Fe oxides and associated elements (Be, B, P, and Mo) precipitated as the result of mixing of hydrothermal fluids with seawater. ?? 2001 Canadian Institute of Mining, Metallurgy and Petroleum. All rights reserved.

Remediation of groundwater contaminated with arsenic through enhanced natural attenuation: Batch and column studies.

PubMed

Hafeznezami, Saeedreza; Zimmer-Faust, Amity G; Jun, Dukwoo; Rugh, Megyn B; Haro, Heather L; Park, Austin; Suh, Jae; Najm, Tina; Reynolds, Matthew D; Davis, James A; Parhizkar, Tarannom; Jay, Jennifer A

2017-10-01

Batch and column laboratory experiments were conducted on natural sediment and groundwater samples from a contaminated site in Maine, USA with the aim of lowering the dissolved arsenate [As(V)] concentrations through chemical enhancement of natural attenuation capacity. In batch factorial experiments, two levels of treatment for three parameters (pH, Ca, and Fe) were studied at different levels of phosphate to evaluate their impact on As(V) solubility. Results illustrated that lowering pH, adding Ca, and adding Fe significantly increased the sorption capacity of sediments. Overall, Fe amendment had the highest individual impact on As(V) levels. To provide further evidence for the positive impact of Ca on As(V) adsorption, isotherm experiments were conducted at three different levels of Ca concentrations. A consistent increase in adsorption capacity (26-37%) of sediments was observed with the addition of Ca. The observed favorable effect of Ca on As(V) adsorption is likely caused by an increase in the surface positive charges due to surface accumulation of Ca 2+ ions. Column experiments were conducted by flowing contaminated groundwater with elevated pH, As(V), and phosphate through both uncontaminated and contaminated sediments. Potential in-situ remediation scenarios were simulated by adding a chemical amendment feed to the columns injecting Fe(II) or Ca as well as simultaneous pH adjustment. Results showed a temporary and limited decrease in As(V) concentrations under the Ca treatment (39-41%) and higher levels of attenuation in Fe(II) treated columns (50-91%) but only after a certain number of pore volumes (18-20). This study illustrates the importance of considering geochemical parameters including pH, redox potential, presence of competing ions, and sediment chemical and physical characteristics when considering enhancing the natural attenuation capacity of sediments to mitigate As contamination in natural systems. Copyright © 2017 Elsevier Ltd. All rights reserved.

Long-term variations in sediment heavy metals of a reservoir with changing trophic states: Implications for the impact of climate change.

PubMed

Wu, Qiong; Qi, Jun; Xia, Xinghui

2017-12-31

Two dated sediment cores from the Miyun Reservoir of Beijing in China were analyzed to reconstruct the pollution history of heavy metals including cadmium (Cd), chromium (Cr), iron (Fe), nickel (Ni), and zinc (Zn) as well as phosphorus (P). Enrichment factor (EF) and geoaccumulation index (I geo ) were applied to assess the enrichment status of heavy metals. Average EF and I geo values indicated that the studied heavy metals in the sediments mainly originated from non-point source pollution and soil-water erosion, showing low ecological risks. In addition, correlation analysis and principal component analysis (PCA) identified that Cd, Zn, and P were mainly from agricultural diffusion pollution caused by utilization of the phosphate fertilizer; Zn, Ni, and Cr originated from soil erosion. PCA analysis was further conducted to investigate the relationships among meteorological factors, algae-dominant total organic carbon (TOC), and heavy metals. Results showed that algae-dominant TOC had strong positive correlation with temperature, which can be explained by that increased temperature accelerated the growth of algae. Meanwhile the opposite loadings between algae-dominant TOC and heavy metal suggested that primary production played an important role in migration and transformation of metals. Moreover, stepwise multiple regression models showed that Fe was sensitive to temperature, which accounted for approximately 39.0% and 40.1% of the variations in Fe of two sediment cores, respectively. Fe showed significant decreasing trends during the past 50years. Reductive environment of water-sediment interface caused by increasing temperature probably contributed to the restoration of ferric iron, resulting in the release of soluble Fe to overlying waters. Future climate change with elevated temperature and extreme weather events will aggravate the ecological risk of heavy metals in water environment due to the enhanced leaching effect and non-point source pollution as well as the release of heavy metals from sediments to water environment. Copyright © 2017. Published by Elsevier B.V.

Enrichment of Geobacter species in response to stimulation of Fe(III) reduction in sandy aquifer sediments

USGS Publications Warehouse

Snoeyenbos-West, O.L.; Nevin, K.P.; Anderson, R.T.; Lovely, D.R.

2000-01-01

Engineered stimulation of Fe(III) has been proposed as a strategy to enhance the immobilization of radioactive and toxic metals in metal-contaminated subsurface environments. Therefore, laboratory and field studies were conducted to determine which microbial populations would respond to stimulation of Fe(III) reduction in the sediments of sandy aquifers. In laboratory studies, the addition of either various organic electron donors or electron shuttle compounds stimulated Fe(III) reduction and resulted in Geobacter sequences becoming important constituents of the Bacterial 16S rDNA sequences that could be detected with PCR amplification and denaturing gradient gel electrophoresis (DGGE). Quantification of Geobacteraceae sequences with a PCR most-probable-number technique indicated that the extent to which numbers of Geobacter increased was related to the degree of stimulation of Fe(III) reduction. Geothrix species were also enriched in some instances, but were orders of magnitude less numerous than Geobacter species. Shewanella species were not detected, even when organic compounds known to be electron donors for Shewanella species were used to stimulate Fe(III) reduction in the sediments. Geobacter species were also enriched in two field experiments in which Fe(III) reduction was stimulated with the addition of benzoate or aromatic hydrocarbons. The apparent growth of Geobacter species concurrent with increased Fe(III) reduction suggests that Geobacter species were responsible for much of the Fe(III) reduction in all of the stimulation approaches evaluated in three geographically distinct aquifers. Therefore, strategies for subsurface remediation that involve enhancing the activity of indigenous Fe(III)-reducing populations in aquifers should consider the physiological properties of Geobacter species in their treatment design.

The Use of Enzyme Hydrolysis to Assess the Seasonal Mobility and Bioavailability of Organic Phosphorus in Lake Sediments

NASA Astrophysics Data System (ADS)

Giles, C. D.; Lee, L. G.; Cade-Menun, B. J.; Rutila, B. C.; Schroth, A. W.; Xu, Y.; Hill, J. E.; Druschel, G.

2013-12-01

Lake sediments represent a significant internal source of phosphorus (P) in eutrophic freshwater systems during periods of high biological activity and oxygen depletion in sediments. Enzyme-labile and redox-sensitive P fractions may be a major component of the mobile sediment P pool which contributes to the development of harmful algal blooms. We present a high-through-put enzyme-based method for assessing potentially bioavailable (enzyme-labile) P in lake sediments and describe the relationship between enzyme-labile P, ascorbate-extractable (reactive) P and metals (Fe, Mn, Al, Ca), and P species identified using solution 31-P NMR spectroscopy. Sediment cores (0-10 cm) were collected from Lake Champlain over multiple years (Missisquoi Bay, VT, USA; 2007-2013). A principal components analysis of sediment properties suggests that enzyme-labile and reactive P, Mn, and Fe concentrations were more effective than the 31-P NMR methodology alone for differentiating algal bloom stage associated with periods of sediment anoxia. Bloom onset (July 2008) and peak bloom (August 2008, 2012) periods corresponded to the highest enzyme-labile P and lowest reactive P and metals proportions, despite 31-P NMR profiles which did not change significantly with respect to time and depth. High levels of reduced Fe and Mn ions were also detected in pore-water during this period, confirming previous reports that organic P bioavailability is linked to the redox status of sediments. High through-put analysis of enzyme-labile P fractions will provide spatially and temporally resolved information on bioavailable P pools at lower cost than traditional methods (i.e., 31-P NMR), and provide much-needed detail on aquatic P cycles during discrete stages of algal bloom development and sediment anoxia.

Persistence of deeply sourced iron in the Pacific Ocean.

PubMed

Horner, Tristan J; Williams, Helen M; Hein, James R; Saito, Mak A; Burton, Kevin W; Halliday, Alex N; Nielsen, Sune G

2015-02-03

Biological carbon fixation is limited by the supply of Fe in vast regions of the global ocean. Dissolved Fe in seawater is primarily sourced from continental mineral dust, submarine hydrothermalism, and sediment dissolution along continental margins. However, the relative contributions of these three sources to the Fe budget of the open ocean remains contentious. By exploiting the Fe stable isotopic fingerprints of these sources, it is possible to trace distinct Fe pools through marine environments, and through time using sedimentary records. We present a reconstruction of deep-sea Fe isotopic compositions from a Pacific Fe-Mn crust spanning the past 76 My. We find that there have been large and systematic changes in the Fe isotopic composition of seawater over the Cenozoic that reflect the influence of several, distinct Fe sources to the central Pacific Ocean. Given that deeply sourced Fe from hydrothermalism and marginal sediment dissolution exhibit the largest Fe isotopic variations in modern oceanic settings, the record requires that these deep Fe sources have exerted a major control over the Fe inventory of the Pacific for the past 76 My. The persistence of deeply sourced Fe in the Pacific Ocean illustrates that multiple sources contribute to the total Fe budget of the ocean and highlights the importance of oceanic circulation in determining if deeply sourced Fe is ever ventilated at the surface.

Magnesium ferrite nanocrystal clusters for magnetorheological fluid with enhanced sedimentation stability

NASA Astrophysics Data System (ADS)

Wang, Guangshuo; Ma, Yingying; Li, Meixia; Cui, Guohua; Che, Hongwei; Mu, Jingbo; Zhang, Xiaoliang; Tong, Yu; Dong, Xufeng

2017-01-01

In this study, magnesium ferrite (MgFe2O4) nanocrystal clusters were synthesized using an ascorbic acid-assistant solvothermal method and evaluated as a candidate for magnetorheological (MR) fluid. The morphology, microstructure and magnetic properties of the MgFe2O4 nanocrystal clusters were investigated in detail by field emission scanning electron microscopy (FESEM), transmission electron microscope (TEM), thermogravimetric analyzer (TGA), X-ray diffraction (XRD) and superconducting quantum interference device (SQUID). The MgFe2O4 nanocrystal clusters were suspended in silicone oil to prepare MR fluid and the MR properties were tested using a Physica MCR301 rheometer fitted with a magneto-rheological module. The prepared MR fluid showed typical Bingham plastic behavior, changing from a liquid-like to a solid-like structure under an external magnetic field. Compared with the conventional carbonyl iron particles, MgFe2O4 nanocrystal clusters-based MR fluid demonstrated enhanced sedimentation stability due to the reduced mismatch in density between the particles and the carrier medium. In summary, the as-prepared MgFe2O4 nanocrystal clusters are regarded as a promising candidate for MR fluid with enhanced sedimentation stability.

Rare earth elements (REE) and yttrium in stream waters, stream sediments, and Fe Mn oxyhydroxides: Fractionation, speciation, and controls over REE + Y patterns in the surface environment

NASA Astrophysics Data System (ADS)

Leybourne, Matthew I.; Johannesson, Karen H.

2008-12-01

We have collected ˜500 stream waters and associated bed-load sediments over an ˜400 km 2 region of Eastern Canada and analyzed these samples for Fe, Mn, and the rare earth elements (REE + Y). In addition to analyzing the stream sediments by total digestion (multi-acid dissolution with metaborate fusion), we also leached the sediments with 0.25 M hydroxylamine hydrochloride (in 0.05 M HCl), to determine the REE + Y associated with amorphous Fe- and Mn-oxyhydroxide phases. We are thus able to partition the REE into "dissolved" (<0.45 μm), labile (hydroxylamine) and detrital sediment fractions to investigate REE fractionation, and in particular, with respect to the development of Ce and Eu anomalies in oxygenated surface environments. Surface waters are typically LREE depleted ([La/Sm] NASC ranges from 0.16 to 5.84, average = 0.604, n = 410; where the REE are normalized to the North America Shale Composite), have strongly negative Ce anomalies ([Ce/Ce ∗] NASC ranges from 0.02 to 1.25, average = 0.277, n = 354), and commonly have positive Eu anomalies ([Eu/Eu ∗] NASC ranges from 0.295 to 1.77, average = 0.764, n = 84). In contrast, the total sediment have flatter REE + Y patterns relative to NASC ([La/Sm] NASC ranges from 0.352 to 1.12, average = 0.778, n = 451) and are slightly middle REE enriched ([Gd/Yb] NASC ranges from 0.55 to 3.75, average = 1.42). Most total sediments have negative Ce and Eu anomalies ([Ce/Ce ∗] NASC ranges from 0.097 to 2.12, average = 0.799 and [Eu/Eu ∗] NASC ranges from 0.39 to 1.43, average = 0.802). The partial extraction sediments are commonly less LREE depleted than the total sediments ([La/Sm] NASC ranges from 0.24 to 3.31, average = 0.901, n = 4537), more MREE enriched ([Gd/Yb] NASC ranges from 0.765 to 6.28, average = 1.97) and Ce and Eu anomalies (negative and positive) are more pronounced. The partial extraction recovered, on average ˜20% of the Fe in the total sediment, ˜80% of the Mn, and 21-29% of the REEs (Ce = 19% and Y = 32%). Comparison between REEs in water, partial extraction and total sediment analyses indicates that REEs + Y in the stream sediments have two primary sources, the host lithologies (i.e., mechanical dispersion) and hydromorphically transported (the labile fraction). Furthermore, Eu appears to be more mobile than the other REE, whereas Ce is preferentially removed from solution and accumulates in the stream sediments in a less labile form than the other REEs + Y. Despite poor statistical correlations between the REEs + Y and Mn in either the total sediment or partial extractions, based on apparent distribution coefficients and the pH of the stream waters, we suggest that either sediment organic matter and/or possibly δ-MnO 2/FeOOH are likely the predominant sinks for Ce, and to a lesser extent the other REE, in the stream sediments.

Metals in some lagoons of Mexico.

PubMed Central

Vazquez, F G; Sharma, V K; Alexander, V H; Frausto, C A

1995-01-01

The concentrations of metals, Cd, Cu, Fe, Mn, Ni, Pb, and Zn were determined in some lagoons to establish the level of metal pollution. The lagoons studied were Alvarado lagoon, Veracruz; San Andres lagoon, Tamaulipas; and Terminos lagoon, Campeche. The concentrations were determined in water, oyster (Crassostrea virginica), and sediments. Metals were accumulated in either oysters or sediments. Cu and Zn were higher in oysters and Fe and Mn were higher in sediments. The results in water samples were compared with the limit established by the Secretaria de Ecologia and Desarrollo Urbano Report and briefly discussed. PMID:7621796

Processes affecting transport of uranium in a suboxic aquifer

USGS Publications Warehouse

Davis, J.A.; Curtis, G.P.; Wilkins, M.J.; Kohler, M.; Fox, P.; Naftz, D.L.; Lloyd, J.R.

2006-01-01

At the Naturita site in Colorado, USA, groundwaters were sampled and analyzed for chemical composition and by culture and culture-independent microbiological techniques. In addition, sediments were extracted with a dilute sodium carbonate solution to determine quantities of labile uranium within the sediments. Samples from the upgradient portion of the contaminated aquifer, where very little dissolved Fe(II) is found in the groundwater, have uranium content that is controlled by U(VI) adsorption and few metal-reducing bacteria are observed. In the extreme downgradient portion of the aquifer, where dissolved Fe(II) is observed, uranium content of the sediments includes significant quantities of reduced U(IV) and diverse populations of Fe(III)-reducing bacteria were present in the subsurface with the potential of reducing U(VI) to U(IV). ?? 2006 Elsevier Ltd. All rights reserved.

Distribution of Cu, Co, As, and Fe in mine waste, sediment, soil, and water in and around mineral deposits and mines of the Idaho Cobalt Belt, USA

USGS Publications Warehouse

Gray, John E.; Eppinger, Robert G.

2012-01-01

The distribution of Cu, Co, As and Fe was studied downstream from mines and deposits in the Idaho Cobalt Belt (ICB), the largest Co resource in the USA. To evaluate potential contamination in ecosystems in the ICB, mine waste, stream sediment, soil, and water were collected and analyzed for Cu, Co, As and Fe in this area. Concentrations of Cu in mine waste and stream sediment collected proximal to mines in the ICB ranged from 390 to 19,000 μg/g, exceeding the USEPA target clean-up level and the probable effect concentration (PEC) for Cu of 149 μg/g in sediment; PEC is the concentration above which harmful effects are likely in sediment dwelling organisms. In addition concentrations of Cu in mine runoff and stream water collected proximal to mines were highly elevated in the ICB and exceeded the USEPA chronic criterion for aquatic organisms of 6.3 μg/L (at a water hardness of 50 mg/L) and an LC50 concentration for rainbow trout of 14 μg/L for Cu in water. Concentrations of Co in mine waste and stream sediment collected proximal to mines varied from 14 to 7400 μg/g and were highly elevated above regional background concentrations, and generally exceeded the USEPA target clean-up level of 80 μg/g for Co in sediment. Concentrations of Co in water were as high as in 75,000 μg/L in the ICB, exceeding an LC50 of 346 μg/L for rainbow trout for Co in water by as much as two orders of magnitude, likely indicating an adverse effect on trout. Mine waste and stream sediment collected in the ICB also contained highly elevated As concentrations that varied from 26 to 17,000 μg/g, most of which exceeded the PEC of 33 μg/g and the USEPA target clean-up level of 35 μg/g for As in sediment. Conversely, most water samples had As concentrations that were below the 150 μg/L chronic criterion for protection of aquatic organisms and the USEPA target clean-up level of 14 μg/L. There is abundant Fe oxide in streams in the ICB and several samples of mine runoff and stream water exceeded the chronic criterion for protection of aquatic organisms of 1000 μg/L for Fe. There has been extensive remediation of mined areas in the ICB, but because some mine waste remaining in the area contains highly elevated Cu, Co, As and Fe, inhalation or ingestion of mine waste particulates may lead to human exposure to these elements.

Dominance of 'Gallionella capsiferriformans' and heavy metal association with Gallionella-like stalks in metal-rich pH 6 mine water discharge

USGS Publications Warehouse

Fabisch, Maria; Freyer, Gina; Johnson, Carol A.; Buchel, Georg; Akob, Denise M.; Neu, Thomas R.; Kusel, Kirsten

2016-01-01

Heavy metal-contaminated, pH 6 mine water discharge created new streams and iron-rich terraces at a creek bank in a former uranium-mining area near Ronneburg, Germany. The transition from microoxic groundwater with ~5 mm Fe(II) to oxic surface water may provide a suitable habitat for microaerobic iron-oxidizing bacteria (FeOB). In this study, we investigated the potential contribution of these FeOB to iron oxidation and metal retention in this high-metal environment. We (i) identified and quantified FeOB in water and sediment at the outflow, terraces, and creek, (ii) studied the composition of biogenic iron oxides (Gallionella-like twisted stalks) with scanning and transmission electron microscopy (SEM, TEM) as well as confocal laser scanning microscopy (CLSM), and (iii) examined the metal distribution in sediments. Using quantitative PCR, a very high abundance of FeOB was demonstrated at all sites over a 6-month study period. Gallionella spp. clearly dominated the communities, accounting for up to 88% ofBacteria, with a minor contribution of other FeOB such as Sideroxydans spp. and ‘Ferrovum myxofaciens’. Classical 16S rRNA gene cloning showed that 96% of the Gallionella-related sequences had ≥97% identity to the putatively metal-tolerant ‘Gallionella capsiferriformans ES-2’, in addition to known stalk formers such as Gallionella ferruginea and Gallionellaceae strain R-1. Twisted stalks from glass slides incubated in water and sediment were composed of the Fe(III) oxyhydroxide ferrihydrite, as well as polysaccharides. SEM and scanning TEM-energy-dispersive X-ray spectroscopy revealed that stalk material contained Cu and Sn, demonstrating the association of heavy metals with biogenic iron oxides and the potential for metal retention by these stalks. Sequential extraction of sediments suggested that Cu (52–61% of total sediment Cu) and other heavy metals were primarily bound to the iron oxide fractions. These results show the importance of ‘G. capsiferriformans’ and biogenic iron oxides in slightly acidic but highly metal-contaminated freshwater environments.

Persistence of deeply sourced iron in the Pacific Ocean

PubMed Central

Horner, Tristan J.; Williams, Helen M.; Hein, James R.; Saito, Mak A.; Burton, Kevin W.; Halliday, Alex N.; Nielsen, Sune G.

2015-01-01

Biological carbon fixation is limited by the supply of Fe in vast regions of the global ocean. Dissolved Fe in seawater is primarily sourced from continental mineral dust, submarine hydrothermalism, and sediment dissolution along continental margins. However, the relative contributions of these three sources to the Fe budget of the open ocean remains contentious. By exploiting the Fe stable isotopic fingerprints of these sources, it is possible to trace distinct Fe pools through marine environments, and through time using sedimentary records. We present a reconstruction of deep-sea Fe isotopic compositions from a Pacific Fe−Mn crust spanning the past 76 My. We find that there have been large and systematic changes in the Fe isotopic composition of seawater over the Cenozoic that reflect the influence of several, distinct Fe sources to the central Pacific Ocean. Given that deeply sourced Fe from hydrothermalism and marginal sediment dissolution exhibit the largest Fe isotopic variations in modern oceanic settings, the record requires that these deep Fe sources have exerted a major control over the Fe inventory of the Pacific for the past 76 My. The persistence of deeply sourced Fe in the Pacific Ocean illustrates that multiple sources contribute to the total Fe budget of the ocean and highlights the importance of oceanic circulation in determining if deeply sourced Fe is ever ventilated at the surface. PMID:25605900

Mackinawite (FeS) Reduces Mercury(II) under Sulfidic Conditions

PubMed Central

2015-01-01

Mercury (Hg) is a toxicant of global concern that accumulates in organisms as methyl Hg. The production of methyl Hg by anaerobic bacteria may be limited in anoxic sediments by the sequestration of divalent Hg [Hg(II)] into a solid phase or by the formation of elemental Hg [Hg(0)]. We tested the hypothesis that nanocrystalline mackinawite (tetragonal FeS), which is abundant in sediments where Hg is methylated, both sorbs and reduces Hg(II). Mackinawite suspensions were equilibrated with dissolved Hg(II) in batch reactors. Examination of the solid phase using Hg LIII-edge extended X-ray absorption fine structure (EXAFS) spectroscopy showed that Hg(II) was indeed reduced in FeS suspensions. Measurement of purgeable Hg using cold vapor atomic fluorescence spectrometry (CVAFS) from FeS suspensions and control solutions corroborated the production of Hg(0) that was observed spectroscopically. However, a fraction of the Hg(II) initially added to the suspensions remained in the divalent state, likely in the form of β-HgS-like clusters associated with the FeS surface or as a mixture of β-HgS and surface-associated species. Complexation by dissolved S(-II) in anoxic sediments hinders Hg(0) formation, but, by contrast, Hg(II)–S(-II) species are reduced in the presence of mackinawite, producing Hg(0) after only 1 h of reaction time. The results of our work support the idea that Hg(0) accounts for a significant fraction of the total Hg in wetland and estuarine sediments. PMID:25180562

Distribution and Potential Toxicity of Trace Metals in the Surface Sediments of Sundarban Mangrove Ecosystem, Bangladesh

NASA Astrophysics Data System (ADS)

Kumar, A.; Ramanathan, A.; Mathukumalli, B. K. P.; Datta, D. K.

2014-12-01

The distribution, enrichment and ecotoxocity potential of Bangladesh part of Sundarban mangrove was investigated for eight trace metals (As, Cd, Cr, Cu, Fe, Mn, Pb and Zn) using sediment quality assessment indices. The average concentration of trace metals in the sediments exceeded the crustal abundance suggesting sources other than natural in origin. Additionally, the trace metals profile may be a reflection of socio-economic development in the vicinity of Sundarban which further attributes trace metals abundance to the anthropogenic inputs. Geoaccumulation index suggests moderately polluted sediment quality w.r.t. Ni and As and background concentrations for Al, Fe, Mn, Cu, Zn, Pb, Co, As and Cd. Contamination factor analysis suggested low contamination by Zn, Cr, Co and Cd, moderate by Fe, Mn, Cu and Pb while Ni and As show considerable and high contamination, respectively. Enrichment factors for Ni, Pb and As suggests high contamination from either biota or anthropogenic inputs besides natural enrichment. As per the three sediment quality guidelines, Fe, Mn, Cu, Ni, Co and As would be more of a concern with respect to ecotoxicological risk in the Sundarban mangroves. The correlation between various physiochemical variables and trace metals suggested significant role of fine grained particles (clay) in trace metal distribution whereas owing to low organic carbon content in the region the organic complexation may not be playing significant role in trace metal distribution in the Sundarban mangroves.

Uranium accumulation in modern and ancient Fe-oxide sediments: Examples from the Ashadze-2 hydrothermal sulfide field (Mid-Atlantic Ridge) and Yubileynoe massive sulfide deposit (South Urals, Russia)

NASA Astrophysics Data System (ADS)

Ayupova, N. R.; Melekestseva, I. Yu.; Maslennikov, V. V.; Tseluyko, A. S.; Blinov, I. A.; Beltenev, V. E.

2018-05-01

Fe-oxyhydroxide sediments (gossans) from the Ashadze-2 hydrothermal sulfide field (Mid-Atlantic Ridge) and hematite-carbonate-quartz rocks (gossanites) from the Yubileynoe Cu-Zn VHMS deposit (South Urals) are characterized by anomalously high U contents (up to 352 ppm and 73 ppm, respectively). In gossans from the Ashadze-2 hydrothermal sulfide field, rare isometric anhedral uraninite grains (up to 2 μm) with outer P- and Ca-rich rims, and numerous smaller (<1 μm) grains, occur in Fe-oxyhydroxides and sepiolite, associated with pyrite, isocubanite, chalcopyrite, galena, atacamite and halite. In gossanites from the Yubileynoe deposit, numerous uraninite particles (<3 μm) are associated with apatite, V-rich Mg-chlorite, micro-nodules of pyrite, Se-bearing galena, hessite and acanthite in a hematite-carbonate-quartz matrix. Small (1-3 μm) round grains of uraninite, which locally coalesce to large grains up to 10 μm in size, are associated with authigenic chalcopyrite. The similar diagenetic processes of U accumulation in modern and ancient Fe-oxyhydroxide sediments were the result of U fixation from seawater during the oxidation of sulfide minerals. Uraninite in gossanites was mainly deposited from diagenetic pore fluids, which circulated in the sulfide-hyaloclast-carbonate sediments.

Coupled cycling of Fe and organic carbon in submarine hydrothermal systems: Modelling approach

NASA Astrophysics Data System (ADS)

Legendre, Louis; German, Christopher R.; Sander, Sylvia G.; Niquil, Nathalie

2014-05-01

It has been recently proposed that hydrothermal plumes may be a significant source of dissolved Fe to the oceans. In order to assess this proposal, we investigated the fate of dissolved Fe released from hydrothermal systems to the overlying ocean using an approach that combined modelling and field values. We based our work on a consensus conceptual model developed by members of SCOR-InterRidge Working Group 135. The model was both complex enough to capture the main processes of dissolved Fe released from hydrothermal systems and chemical transformation in the hydrothermal plume, and simple enough to be parameterized with existing field data. It included the following flows: Fe, water and heat in the high temperature vent fluids, in the fluids diffusing around the vent, and in the entrained seawater in the buoyant plume; Fe precipitation in polymetallic sulphides near the vent; transport of Fe in the non-buoyant plume, and both its precipitation in particles onto the sea bottom away from the vent and dissolution into deep-sea waters. In other words, there were three Fe input flows into the buoyant hydrothermal plume (vent-fluids; entrained diffuse flow; entrained seawater) and three Fe output flows (sedimentation from the buoyant plume as polymetallic sulfides; sedimentation from the non-buoyant plume in particulate form; export to the deep ocean in dissolved or nanoparticulate form). The output flows balanced the input flows. We transformed the conceptual model into equations, and parameterized these with field data. To do so, we assumed that all hydrothermal systems, globally, can be represented by the circumstances that prevail at the EPR 9°50'N hydrothermal field, although we knew this assumption not to be accurate. We nevertheless achieved, by following this approach, two important goals, i.e. we could assemble into a coherent framework, for the first time, several discrete data sets acquired independently over decades of field work, and we could obtain model results that were consistent with recent field observations. We used our model to explore scenarios of Fe emissions and transformations under various constraints. The modelling exercises indicated that the provision of significant amounts of dissolved Fe to the oceans by hydrothermal plumes was consistent with realistic model parameters. This supported the proposition that hydrothermal systems play significant roles in the global biogeochemical Fe cycle.

Characterization of Fe (III)-reducing enrichment culture and isolation of Fe (III)-reducing bacterium Enterobacter sp. L6 from marine sediment.

PubMed

Liu, Hongyan; Wang, Hongyu

2016-07-01

To enrich the Fe (III)-reducing bacteria, sludge from marine sediment was inoculated into the medium using Fe (OH)3 as the sole electron acceptor. Efficiency of Fe (III) reduction and composition of Fe (III)-reducing enrichment culture were analyzed. The results indicated that the Fe (III)-reducing enrichment culture with the dominant bacteria relating to Clostridium and Enterobacter sp. had high Fe (III) reduction of (2.73 ± 0.13) mmol/L-Fe (II). A new Fe (III)-reducing bacterium was isolated from the Fe (III)-reducing enrichment culture and identified as Enterobacter sp. L6 by 16S rRNA gene sequence analysis. The Fe (III)-reducing ability of strain L6 under different culture conditions was investigated. The results indicated that strain L6 had high Fe (III)-reducing activity using glucose and pyruvate as carbon sources. Strain L6 could reduce Fe (III) at the range of NaCl concentrations tested and had the highest Fe (III) reduction of (4.63 ± 0.27) mmol/L Fe (II) at the NaCl concentration of 4 g/L. This strain L6 could reduce Fe (III) with unique properties in adaptability to salt variation, which indicated that it can be used as a model organism to study Fe (III)-reducing activity isolated from marine environment. Copyright © 2015 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Organic matter mineralization and trace element post-depositional redistribution in Western Siberia thermokarst lake sediments

NASA Astrophysics Data System (ADS)

Audry, S.; Pokrovsky, O. S.; Shirokova, L. S.; Kirpotin, S. N.; Dupré, B.

2011-11-01

This study reports the very first results on high-resolution sampling of sediments and their porewaters from three thermokarst (thaw) lakes representing different stages of ecosystem development located within the Nadym-Pur interfluve of the Western Siberia plain. Up to present time, the lake sediments of this and other permafrost-affected regions remain unexplored regarding their biogeochemical behavior. The aim of this study was to (i) document the early diagenesic processes in order to assess their impact on the organic carbon stored in the underlying permafrost, and (ii) characterize the post-depositional redistribution of trace elements and their impact on the water column. The estimated organic carbon (OC) stock in thermokarst lake sediments of 14 ± 2 kg m-2 is low compared to that reported for peat soils from the same region and denotes intense organic matter (OM) mineralization. Mineralization of OM in the thermokarst lake sediments proceeds under anoxic conditions in all the three lakes. In the course of the lake development, a shift in mineralization pathways from nitrate and sulfate to Fe- and Mn-oxyhydroxides as the main terminal electron acceptors in the early diagenetic reactions was suggested. This shift was likely promoted by the diagenetic consumption of nitrate and sulfate and their gradual depletion in the water column due to progressively decreasing frozen peat lixiviation occurring at the lake's borders. Trace elements were mobilized from host phases (OM and Fe- and Mn-oxyhydroxides) and partly sequestered in the sediment in the form of authigenic Fe-sulfides. Arsenic and Sb cycling was also closely linked to that of OM and Fe- and Mn-oxyhydroxides. Shallow diagenetic enrichment of particulate Sb was observed in the less mature stages. As a result of authigenic sulfide precipitation, the sediments of the early stage of ecosystem development were a sink for water column Cu, Zn, Cd, Pb and Sb. In contrast, at all stages of ecosystem development, the sediments were a source of dissolved Co, Ni and As to the water column. However, the concentrations of these trace elements remained low in the bottom waters, indicating that sorption processes on Fe-bounding particles and/or large-size organo-mineral colloids could mitigate the impact of post-depositional redistribution of toxic elements on the water column.

Organic matter mineralization and trace element post-depositional redistribution in Western Siberia thermokarst lake sediments

NASA Astrophysics Data System (ADS)

Audry, S.; Pokrovsky, O. S.; Shirokova, L. S.; Kirpotin, S. N.; Dupré, B.

2011-08-01

This study reports the very first results on high-resolution sampling of sediments and their porewaters from three thermokarst (thaw) lakes representing different stages of ecosystem development located within the Nadym-Pur interfluve of the Western Siberia plain. Up to present time, the lake sediments of this and other permafrost-affected regions remain unexplored regarding their biogeochemical behavior. The aim of this study was to (i) document the early diagenesic processes in order to assess their impact on the organic carbon stored in the underlying permafrost, and (ii) characterize the post-depositional redistribution of trace elements and their impact on the water column. The estimated organic carbon (OC) stock in thermokarst lake sediments of 14 ± 2 kg m-2 is low compared to that reported for peat soils from the same region and denotes intense organic matter (OM) mineralization. Mineralization of OM in the thermokarst lake sediments proceeds under anoxic conditions in all the three lakes. In the course of the lake development, a shift in mineralization pathways was evidenced from nitrate and sulfate to Fe- and Mn-oxyhydroxides as the main terminal electron acceptors in the early diagenetic reactions. This shift was promoted by the diagenetic consumption of nitrate and sulfate and their gradual depletion in the water column due to progressively decreasing frozen peat lixiviation occurring at the lake's borders. Trace elements were mobilized from host phases (OM and Fe- and Mn-oxyhydroxides) and partly sequestered in the sediment in the form of authigenic Fe-sulfides. Arsenic and Sb cycling was also closely linked to that of OM and Fe- and Mn-oxyhydroxides. Shallow diagenetic enrichment of particulate Sb was observed in the less mature stages. As a result of authigenic sulfide precipitation, the sediments of the early stage of ecosystem development were a sink for water column Cu, Zn, Cd, Pb and Sb. In contrast, at all stages of ecosystem development, the sediments were a source of dissolved Co, Ni and As to the water column. However, the concentrations of these trace elements remained low in the bottom waters, indicating that sorption processes on Fe-bounding particles and/or large-size organo-mineral colloids could mitigate the impact of post-depositional redistribution of toxic elements on the water column.

Greigite (Fe3S4) as an indicator of drought - The 1912-1994 sediment magnetic record from White Rock Lake, Dallas, Texas, USA

USGS Publications Warehouse

Reynolds, R.L.; Rosenbaum, J.G.; Van Metre, P.; Tuttle, M.; Callender, E.; Goldin, A.

1999-01-01

Combined magnetic and geochemical studies were conducted on sediments from White Rock Lake, a reservoir in suburban Dallas (USA), to investigate how land use has affected sediment and water quality since the reservoir was filled in 1912. The chronology of a 167-cm-long core is constrained by the recognition of the pre-reservoir surface and by 137Cs results. In the reservoir sediments, magnetic susceptibility (MS) and isothermal remanent magnetization (IRM) are largely carried by detrital titanomagnetite that originally formed in igneous rocks. Titanomagnetite and associated hematite are the dominant iron oxides in a sample from the surficial deposit in the watershed but are absent in the underlying Austin Chalk. Therefore, these minerals were transported by wind into the watershed. After about 1960, systematic decreases in Ti, Fe, and Al suggest diminished input of detrital Fe-Ti oxides from the surficial deposits. MS and IRM remain constant over this interval, however, implying compensation by an increase in strongly magnetic material derived from human activity. Anthropogenic magnetite in rust and ferrite spherules (from fly ash?) are more common in sediment deposited after about 1970 than before and may account for the constant magnetization despite the implied decrease in detrital Fe-Ti oxides. An unexpected finding is the presence of authigenic greigite (Fe3S4), the abundance of which is at least partly controlled by climate. Greigite is common in sediments that predate about 1975, with zones of concentration indicated by relatively high IRM/MS. High greigite contents in sediment deposited during the early to mid-1950s and during the mid-1930s correspond to several-year periods of below-average precipitation and drought from historical records. Relatively long water-residence times in the reservoir during these periods may have led to elevated levels of sulfate available for bacterial sulfate reduction. The sulfate was probably derived via the oxidation of pyrite that is common in the underlying Austin Chalk. These results provide a basis for the paleoenvironmental interpretation of greigite occurrence in older lake sediments. The results also indicate that greigite formed rapidly and imply that it can be preserved in the amounts produced over a short time span (in this lake, only a few years). This finding thus suggests that, in some lacustrine settings, greigite is capable of recording paleomagnetic secular variation.

Mobility of arsenic in the sub-surface environment: An integrated hydrogeochemical study and sorption model of the sandy aquifer materials

NASA Astrophysics Data System (ADS)

Nath, Bibhash; Chakraborty, Sudipta; Burnol, André; Stüben, Doris; Chatterjee, Debashis; Charlet, Laurent

2009-01-01

SummaryGroundwater and aquifer materials have been characterized geochemically at a field site located in the Chakdaha municipality of West Bengal, India. Sorption experiments were also carried out on a sandy aquifer material to understand the mobility of arsenic (As) in the sub-surface environments. The result shows that the areas associated with high groundwater As (mean: 1.8 μM) is typically associated with low Eh (mean: -129 mV), and high Fe (mean: 0.11 mM), where Fe 2+/Fe(OH) 3 couple is controlling groundwater redox potential. Analysis of the aquifer material total concentrations showed the dominance of As (range: 8.9-22 mg kg -1), Fe (range: 3.0-9.7% as Fe 2O 3) and Mn (range: 0.05-0.18% as MnO) in the silt-/clay-rich sediments; whereas fine-/medium-sand rich sediment contains considerably lower amount of As (<8.1 mg kg -1), Fe (range: 1.6-3.9% as Fe 2O 3) and Mn (range: 0.02-0.08% as MnO). The acid extractable As do not correlate with ascorbate extractable Fe-oxyhydroxide, however Fe-oxyhydroxide is generally high in the sediments from low groundwater As areas. Chemical speciation computations indicated Fe(II), Ca(II), Mg(II) and Mn(II) to be at equilibrium (with respect to calcite, dolomite and rhodochrosite) or slightly over-saturated (with respect to siderite). These carbonate minerals may therefore participate to the As immobilization. The measured total organic carbon (˜1%) and groundwater temperature (26-32 °C) coupled with sorption studies strongly favors microbially mediated Fe(III)-oxyhydroxide reduction as the dominant mechanism for the release of As in the groundwater. Oscillations of As, Mn and Fe concentrations with depth reflected pCO 2 oscillations consecutive to microbial respiration intensity.

Assessment of oxidative stress and bioaccumulation of the metals Cu, Fe, Zn, Pb, Cd in the polychaete Perinereis gualpensis from estuaries of central Chile.

PubMed

Gaete, Hernán; Álvarez, Manuel; Lobos, Gabriela; Soto, Eulogio; Jara-Gutiérrez, Carlos

2017-11-01

The estuaries of the Aconcagua and Maipo Rivers of central Chile are receptors of residues that contain metals from anthropic activities including agriculture, mining and smelters, which have different levels in the two basins. This study postulates that the exposition to metals is different in the two estuaries and that their sediments contain bioavailable chemical agents that produce oxidative stress. The aim of the study was to evaluate the effect of estuarine sediments on the polychaete Perinereis gualpensis using oxidative stress biomarkers and to determine the metal concentrations in sediments and their accumulation in P. gualpensis. Sediments and organisms were collected in December 2015 and January 2016 in the estuaries. The Catapilco estuary was used as control, since its basin has little anthropic activity. The metal concentrations of Fe Cu, Pb, Zn and Cd were determined in tissues of the organisms and in sediments. The granulometry, conductivity, redox potential, pH and organic matter in sediments were determined, as well as catalase activity and lipid peroxidation. The results show that the concentrations of metals in sediments were higher in the estuary of the Aconcagua River: Cu: 48 ± 2μgg -1 ; Fe: 154 ± 19mgg -1 , Pb: 20 ± 3μgg -1 and Zn: 143 ± 20μgg -1 . In tissues, Pb and Fe were higher in the estuary of the Maipo River, while Cd was detected only in the Catapilco River mouth. Catalase activity was greater in the estuary of the Aconcagua River and lipid peroxidation in the estuary of the Catapilco River. Significant regressions were found between biomarkers of oxidative stress and metal concentrations in tissues of P. gualpensis. In conclusion, the sediments of the studied estuaries contain bioavailable chemical agents that provoke oxidative stress in P. gualpensis, which may be a risk for the benthic communities of these ecosystems. This species is proposed to monitor metals bioavailability and oxidative stress in estuarine sediments. Copyright © 2017 Elsevier Inc. All rights reserved.

Mineralogical, geochemical, and magnetic signatures of surface sediments from the Canadian Beaufort Shelf and Amundsen Gulf (Canadian Arctic)

NASA Astrophysics Data System (ADS)

Gamboa, Adriana; Montero-Serrano, Jean-Carlos; St-Onge, Guillaume; Rochon, André; Desiage, Pierre-Arnaud

2017-02-01

Mineralogical, geochemical, magnetic, and siliciclastic grain-size signatures of 34 surface sediment samples from the Mackenzie-Beaufort Sea Slope and Amundsen Gulf were studied in order to better constrain the redox status, detrital particle provenance, and sediment dynamics in the western Canadian Arctic. Redox-sensitive elements (Mn, Fe, V, Cr, Zn) indicate that modern sedimentary deposition within the Mackenzie-Beaufort Sea Slope and Amundsen Gulf took place under oxic bottom-water conditions, with more turbulent mixing conditions and thus a well-oxygenated water column prevailing within the Amundsen Gulf. The analytical data obtained, combined with multivariate statistical (notably, principal component and fuzzy c-means clustering analyses) and spatial analyses, allowed the division of the study area into four provinces with distinct sedimentary compositions: (1) the Mackenzie Trough-Canadian Beaufort Shelf with high phyllosilicate-Fe oxide-magnetite and Al-K-Ti-Fe-Cr-V-Zn-P contents; (2) Southwestern Banks Island, characterized by high dolomite-K-feldspar and Ca-Mg-LOI contents; (3) the Central Amundsen Gulf, a transitional zone typified by intermediate phyllosilicate-magnetite-K-feldspar-dolomite and Al-K-Ti-Fe-Mn-V-Zn-Sr-Ca-Mg-LOI contents; and (4) mud volcanoes on the Canadian Beaufort Shelf distinguished by poorly sorted coarse-silt with high quartz-plagioclase-authigenic carbonate and Si-Zr contents, as well as high magnetic susceptibility. Our results also confirm that the present-day sedimentary dynamics on the Canadian Beaufort Shelf is mainly controlled by sediment supply from the Mackenzie River. Overall, these insights provide a basis for future studies using mineralogical, geochemical, and magnetic signatures of Canadian Arctic sediments in order to reconstruct past variations in sediment inputs and transport pathways related to late Quaternary climate and oceanographic changes.

Validation of an updated fractionation and indirect speciation procedure for inorganic arsenic in oxic and suboxic soils and sediments.

PubMed

Lock, Alan; Wallschläger, Dirk; McMurdo, Colin; Tyler, Laura; Belzile, Nelson; Spiers, Graeme

2016-12-01

A sequential extraction procedure (SEP) for the speciation analysis of As(III) and As(V) in oxic and suboxic soils and sediments was validated using a natural lake sediment and three certified reference materials, as well as spike recoveries of As(III) and As(V). Many of the extraction steps have been previously validated making the procedure useful for comparisons to similar previous SEP studies. The novel aspect of this research is the validation for the SEP to maintain As(III) and As(V) species. The proposed five step extraction procedure includes the extraction agents (NH 4 ) 2 SO 4 , NH 4 H 2 PO 4 , H 3 PO 4  + NH 2 OH·HCl, oxalate + ascorbic acid (heated), and HNO 3  + HCl + HF, targeting operationally defined easily exchangeable, strongly sorbed, amorphous Fe oxide bound, crystalline Fe oxide bound, and residual As fractions, respectively. The third extraction step, H 3 PO 4  + NH 2 OH·HCl, has not been previously validated for fraction selectivity. We present evidence for this extraction step to target As complexed with amorphous Fe oxides when used in the SEP proposed here. All solutions were analyzed on ICP-MS. The greatest concentrations of As were extracted from the amorphous Fe oxide fraction and the dominant species was As(V). Lake sediment materials were found to have higher As(III) concentrations than the soil materials. Because different soils/sediments have different chemical characteristics, maintenance of As species during extractions must be validated for specific soil/sediment types using spiking experiments. Copyright © 2016 Elsevier Ltd. All rights reserved.

Geochemical characterisation of shallow aquifer sediments of Matlab Upazila, Southeastern Bangladesh — Implications for targeting low-As aquifers

NASA Astrophysics Data System (ADS)

von Brömssen, Mattias; Häller Larsson, Sara; Bhattacharya, Prosun; Hasan, M. Aziz; Ahmed, Kazi Matin; Jakariya, M.; Sikder, Mohiuddin A.; Sracek, Ondra; Bivén, Annelie; Doušová, Barbora; Patriarca, Claudio; Thunvik, Roger; Jacks, Gunnar

2008-07-01

High arsenic (As) concentrations in groundwater pose a serious threat to the health of millions of people in Bangladesh. Reductive dissolution of Fe(III)-oxyhydroxides and release of its adsorbed As is considered to be the principal mechanism responsible for mobilisation of As. The distribution of As is extremely heterogeneous both laterally and vertically. Groundwater abstracted from oxidised reddish sediments, in contrast to greyish reducing sediments, contains significantly lower amount of dissolved arsenic and can be a source of safe water. In order to study the sustainability of that mitigation option, this study describes the lithofacies and genesis of the sediments within 60 m depth and establishes a relationship between aqueous and solid phase geochemistry. Oxalate extractable Fe and Mn contents are higher in the reduced unit than in the oxidised unit, where Fe and Mn are present in more crystalline mineral phases. Equilibrium modelling of saturation indices suggest that the concentrations of dissolved Fe, Mn and PO43--tot in groundwater is influenced by secondary mineral phases in addition to redox processes. Simulating AsIII adsorption on hydroferric oxides using the Diffuse Layer Model and analytical data gave realistic concentrations of dissolved and adsorbed AsIII for the reducing aquifer and we speculate that the presence of high PO43--tot in combination with reductive dissolution results in the high-As groundwater. The study confirms high mobility of As in reducing aquifers with typically dark colour of sediments found in previous studies and thus validates the approach for location of wells used by local drillers based on sediment colour. A more systematic and standardised colour description and similar studies at more locations are necessary for wider application of the approach.

Distribution and grain-size partitioning of metals in bovfom sediments of an experimentally acidified Wisconsin lake

USGS Publications Warehouse

Elder, John F.

2007-01-01

A study of concentrations and distribution of major and trace elements in surficial bottom sediments of Little Rock Lake in northern Wisconsin included examination of spatial variation and grain-size effects. No significant differences with respect to metal distribution in sediments were observed between the two basins of the lake, despite the experimental acidification of one of the basins from pH 6.1 to 4.6. The concentrations of most elements in the lake sediments were generally similar to soil concentrations in the area and were well below sediment quality criteria. Two exceptions were lead and zinc, whose concentrations in July 1990 exceeded the criteria of 50 μg/g and 100 μg/g, respectively, in both littoral and pelagic sediments. Concentrations of some elements, particularly Cu, Pb, and Zn, increased along transects from nearshore to midlake, following a similar gradient of sedimentary organic carbon. In contrast, Mn, Fe, and alkali/alkaline-earth elements were at maximum concentrations in nearshore sediments. These elements are less likely to partition to organic particles, and their distribution is more dependent on mineralogical composition, grain size, and other factors. Element concentrations varied among different sediment grain-size fractions, although a simple inverse relation to grain size was not observed. Fe, Mn, Pb, and Zn were more concentrated in a grain-size range 20–60 tm than in either the very fine or the coarse fractions, possibly because of the aggregation of smaller particles cemented together by organic and Fe/Mn hydrous-oxide coatings.

Sustained removal of uranium from contaminated groundwater following stimulation of dissimilatory metal reduction.

PubMed

N'Guessan, A Lucie; Vrionis, Helen A; Resch, Charles T; Long, Philip E; Lovley, Derek R

2008-04-15

Previous field studies on in situ bioremediation of uranium-contaminated groundwater in an aquifer in Rifle, Colorado identified two distinct phases following the addition of acetate to stimulate microbial respiration. In phase I, Geobacter species are the predominant organisms, Fe(III) is reduced, and microbial reduction of soluble U(VI) to insoluble U(IV) removes uranium from the groundwater. In phase II, Fe(III) is depleted, sulfate is reduced, and sulfate-reducing bacteria predominate. Long-term monitoring revealed an unexpected third phase during which U(VI) removal continues even after acetate additions are stopped. All three of these phases were successfully reproduced in flow-through sediment columns. When sediments from the third phase were heat sterilized, the capacity for U(VI) removal was lost. In the live sediments U(VI) removed from the groundwater was recovered as U(VI) in the sediments. This contrasts to the recovery of U(IV) in sediments resulting from the reduction of U(VI) to U(IV) during the Fe(III) reduction phase in acetate-amended sediments. Analysis of 16S rRNA gene sequences in the sediments in which U(VI) was being adsorbed indicated that members of the Firmicutes were the predominant organisms whereas no Firmicutes sequences were detected in background sediments which did not have the capacity to sorb U(VI), suggesting that the U(VI) adsorption might be due to the presence of these living organisms or at least their intact cell components. This unexpected enhanced adsorption of U(VI) onto sediments following the stimulation of microbial growth in the subsurface may potentially enhance the cost effectiveness of in situ uranium bioremediation.

In Situ, High-Resolution Profiles of Labile Metals in Sediments of Lake Taihu

PubMed Central

Wang, Dan; Gong, Mengdan; Li, Yangyang; Xu, Lv; Wang, Yan; Jing, Rui; Ding, Shiming; Zhang, Chaosheng

2016-01-01

Characterizing labile metal distribution and biogeochemical behavior in sediments is crucial for understanding their contamination characteristics in lakes, for which in situ, high-resolution data is scare. The diffusive gradient in thin films (DGT) technique was used in-situ at five sites across Lake Taihu in the Yangtze River delta in China to characterize the distribution and mobility of eight labile metals (Fe, Mn, Zn, Ni, Cu, Pb, Co and Cd) in sediments at a 3 mm spatial resolution. The results showed a great spatial heterogeneity in the distributions of redox-sensitive labile Fe, Mn and Co in sediments, while other metals had much less marked structure, except for downward decreases of labile Pb, Ni, Zn and Cu in the surface sediment layers. Similar distributions were found between labile Mn and Co and among labile Ni, Cu and Zn, reflecting a close link between their geochemical behaviors. The relative mobility, defined as the ratio of metals accumulated by DGT to the total contents in a volume of sediments with a thickness of 10 mm close to the surface of DGT probe, was the greatest for Mn and Cd, followed by Zn, Ni, Cu and Co, while Pb and Fe had the lowest mobility; this order generally agreed with that defined by the modified BCR approach. Further analyses showed that the downward increases of pH values in surface sediment layer may decrease the lability of Pb, Ni, Zn and Cu as detected by DGT, while the remobilization of redox-insensitive metals in deep sediment layer may relate to Mn cycling through sulphide coprecipitation, reflected by several corresponding minima between these metals and Mn. These in situ data provided the possibility for a deep insight into the mechanisms involved in the remobilization of metals in freshwater sediments. PMID:27608033

Geochemistry of bed and suspended sediment in the Mississippi river system: provenance versus weathering and winnowing.

PubMed

Piper, D Z; Ludington, Steve; Duval, J S; Taylor, H E

2006-06-01

Stream-bed sediment for the size fraction less than 150 microm, examined in 14,000 samples collected mostly from minor tributaries to the major rivers throughout the Mississippi River drainage system, is composed of 5 mineral fractions identified by factor analysis-Al-silicate minerals, quartz, calcite and dolomite, heavy minerals, and an Fe-Mn fraction. The Al-silicate fraction parallels its distribution in the regolith, emphasizing the local sediment source as a primary control to its distribution. Quartz and the heavy-mineral fraction, and associated trace elements, exhibit a complementary distribution to that of the Al-silicate fraction, with a level of enrichment in the bed sediment that is achieved through winnowing and sorting. The carbonate fraction has a distribution suggesting its dissolution during transport. Trace elements partitioned onto the Fe-Mn, possibly amorphous oxyhydride, fraction are introduced to the streams, in part, through human activity. Except for the heavy-mineral fraction, these fractions are identified in suspended sediment from the Mississippi River itself. Although comparison of the tributary bed sediment with the riverine suspended sediment is problematic, the geochemistry of the suspended sediment seems to corroborate the interpretation of the geochemistry of the bed sediment.

Geochemistry of bed and suspended sediment in the Mississippi river system: Provenance versus weathering and winnowing

USGS Publications Warehouse

Piper, D.Z.; Ludington, S.; Duval, J.S.; Taylor, Howard E.

2006-01-01

Stream-bed sediment for the size fraction less than 150 ??m, examined in 14,000 samples collected mostly from minor tributaries to the major rivers throughout the Mississippi River drainage system, is composed of 5 mineral fractions identified by factor analysis-Al-silicate minerals, quartz, calcite and dolomite, heavy minerals, and an Fe-Mn fraction. The Al-silicate fraction parallels its distribution in the regolith, emphasizing the local sediment source as a primary control to its distribution. Quartz and the heavy-mineral fraction, and associated trace elements, exhibit a complementary distribution to that of the Al-silicate fraction, with a level of enrichment in the bed sediment that is achieved through winnowing and sorting. The carbonate fraction has a distribution suggesting its dissolution during transport. Trace elements partitioned onto the Fe-Mn, possibly amorphous oxyhydride, fraction are introduced to the streams, in part, through human activity. Except for the heavy-mineral fraction, these fractions are identified in suspended sediment from the Mississippi River itself. Although comparison of the tributary bed sediment with the riverine suspended sediment is problematic, the geochemistry of the suspended sediment seems to corroborate the interpretation of the geochemistry of the bed sediment.

Distribution and relationships of selected trace metals in molluscs and associated sediments from the Gulf of Aden, Yemen.

PubMed

Szefer, P; Ali, A A; Ba-Haroon, A A; Rajeh, A A; Gełdon, J; Nabrzyski, M

1999-09-01

Concentrations of Cd, Pb, Zn, Cu, Ni, Co, Cr, Mn and Fe in the soft tissue of Turbo coronatus, Acanthopleura haddoni, Ostrea cucullata and Pitar sp., as well as in associated surface sediments (bulk and bioavailable metal concentrations) from the Gulf of Aden, Yemen, were determined by atomic absorption spectrophotometry method. Large differences between size-classes of molluscs in metal concentrations were recorded. Significant spatial differences in metal concentrations in both the soft tissue of the molluscs and associated sediments studied were mostly identified. Statistically significant correlations (p<0.01) between concentrations of selected metals were observed. A slope of the linear regression is significantly higher than unity for Fe (9.91) and Cd (3.45) in A. haddoni and for Ni (4.15) in T. coronatus, suggesting that the bioavailability of these metals is disproportionally increased with a degree of enrichment of the sediments in Fe, Cd and Ni, respectively. A slope constant approximating to unity (1.14) for Cu in A. haddoni relative to its concentration in sediment extract implies that bioavailability of this metal proportionally increased with growing concentrations of its labile forms in the associated sediment. The degree of contamination of Gulf of Aden waters by the metals studied is discussed and the potential ability of molluscs, especially A. haddoni and T. coronatus, as biomonitors of metallic pollutants is postulated.

Trace metals in sediments of two estuarine lagoons from Puerto Rico.

PubMed

Acevedo-Figueroa, D; Jiménez, B D; Rodríguez-Sierra, C J

2006-05-01

Concentrations of As, Cd, Cu, Fe, Hg, Pb and Zn were evaluated in surface sediments of two estuaries from Puerto Rico, known as San José Lagoon (SJL) and Joyuda Lagoon. Significantly higher concentrations in microg/g dw of Cd (1.8 vs. 0.1), Cu (105 vs. 22), Hg (1.9 vs. 0.17), Pb (219 vs. 8), and Zn (531 vs. 52) were found in sediment samples from SJL when compared to Joyuda Lagoon. Average concentrations of Hg, Pb, and Zn in some sediment samples from SJL were above the effect range median (ERM) that predict toxic effects to aquatic organisms. Enrichments factors using Fe as a normalizer, and correlation matrices showed that metal pollution in SJL was the product of anthropogenic sources, while the metal content in Joyuda Lagoon was of natural origins. Sediment metal concentrations found in SJL were comparable to aquatic systems classified as contaminated from other regions of the world.

Metal concentrations in water and sediments from tourist beaches of Acapulco, Mexico.

PubMed

Jonathan, M P; Roy, P D; Thangadurai, N; Srinivasalu, S; Rodríguez-Espinosa, P F; Sarkar, S K; Lakshumanan, C; Navarrete-López, M; Muñoz-Sevilla, N P

2011-04-01

A survey on the metal concentrations (As, Ba, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, V, Zn) in beach water and sediments is reported from the tourist destination of Acapulco city on the Pacific coast of Mexico. The concentration of dissolved trace metals (DTMs) in beach water and acid leachable trace metals (ALTMs) in sediments indicated that they are anthropogenic in nature due to the increased tourist activities in the crowded beach locations. The statistical analysis indicates Fe and Mn play a major role as metal scavengers in both the medium (water and sediment) and the higher value of other metals is site specific in the study area, indicating that they are transported from the local area. Comparison results suggest that the beach water quality has deteriorated more than the sediments and special care needs to be taken to restore the beach quality. Copyright © 2011 Elsevier Ltd. All rights reserved.

Isotopic studies of epigenetic features in metalliferous sediment, Atlantis II Deep, Red Sea

USGS Publications Warehouse

Zierenberg, Robert A.; Shanks, Wayne C.

1988-01-01

The unique depositional environment of the Atlantis II Deep brine pool in the Red Sea produces a stratiform metalliferous deposit of greater areal extent than deposits formed by buoyant-plume systems typical of the midocean ridges because of much more efficient metal entrapment. Isotopic analyses of strontium, sulfur, carbon, and oxygen from the metalliferous sediments indicate that three major sources contribute dissolved components to the hydrothermal system: seawater, Miocene evaporites, and rift-zone basalt. An areally restricted magnetite-hematite-pyroxene assemblage formed at high temperatures, possibly in response to hydrothermal convection initiated by intrusion of basalt into the metalliferous sediment. A correlation between smectite Fe/(Fe+Mg) ratios and oxygen isotope temperatures suggests that smectite is a potentially important chemical geothermometer, and confirms geochemical calculations indicating that Mg-rich smectite is more stable than Fe-rich smectite at elevated temperatures.

The metal oxide fraction of pelagic sediment in the equatorial North Pacific Ocean: A source of metals in ferromanganese nodules

USGS Publications Warehouse

Piper, D.Z.

1988-01-01

Pelagic sediment recovered at DOMES Site A in the equatorial North Pacific (151??W, 9?? 15???N) consists of a surface homogeneous layer, approximately 10 cm thick, overlying a strongly mottled layer that is lighter in color. The radiolarian composition of both units is Quaternary. In areas where this sediment was only a few centimeters thick, the underlying sediment was early Tertiary. Clay mineralogy and major oxide composition of the two Quaternary sediments are uniform. Their similarity to continental shale suggests that the sediment has a terrigenous source. Clay mineralogy and major oxide composition of the Tertiary sediment also are uniform, although they differ markedly from the Quarternary sediment. In contrast to the major oxides, concentrations of Mn, Co, Cu, and Ni soluble in hydroxylamine hydrochlorideacetic acid are strongly different in the surface and subsurface Quaternary sediment. Mn and Ni exhibit pronounced depletions in the subsurface sediment, Ni slightly more than Mn. Cu is also depleted in the subsurface sediment, but less than Mn. It is also depleted in the subsurface Tertiary sediment, whereas the Mn concentration remains high. Concentration of Co relative to Mn increases into the subsurface Quaternary sediment to a constant Co:Mn ratio of 3 ?? 10-2. The trivalent REE (the REE exclusive of Ce) and Fe exhibit little down-core variation. Distribution of elements in these sediments is closely related to their concentration in associated surface ferromanganese nodules. The nodules are of two distinct types: those from the area where the Quaternary sediment is relatively thick have ??-MnO2 as the dominant manganese mineral. The ratios of Ni:Mn, Cu:Mn, and Fe:Mn in these nodules approximate the corresponding ratios of the soluble fraction of surface sediment. Todorokite is the dominant mineral of nodules recovered from areas where the Quaternary sediment is thin. Relatively high Cu/Mn, Ni/Mn, and low Fe/Mn ratios of these nodules mirror differences between the soluble fraction of surface and subsurface Quaternary sediment. These compositional trends of sediment and nodules at DOMES Site A reflect a diagenetic origin for the todorokite nodules and a predominantly hydrogenous origin for the ??-MnO2 nodules. ?? 1988.

Geochemical peculiarities of sediments in the northeastern Black Sea

NASA Astrophysics Data System (ADS)

Rozanov, A. G.; Gursky, Yu. N.

2016-11-01

We present the results of chemical determinations of Al, Fe, Mn, Cu, Ni, Co, Cr, Pb, Sb, and As in Black Sea sediments over a profile from the Kerch Strait to the eastern part of a deep depression (2210 m). The lithological and geochemical variations were studied in the horizontal and vertical profiles of sediments up to 3 m thick. The tendencies in the distributions of the studied metals during Pleistocene and Holocene sedimentation were analyzed beginning from Neoeuxinian freshwater deposits via the overlaying Drevnechernomorian beds with elevated contents of sapropel to modern clayey carbonate deposits with coccolithophorids. Statistical factor analysis isolated five factors: two main factors (75% of the total dispersion) and three subordinate factors. The first leading biogenic factor (47% of dispersion) reflects the correlation between Corg, Cu, and Ni; the second terrigenous factor (28% of dispersion) combimes Fe, Al, Cr, and Sb. The chemical composition of the sediments reflects the manifestation of diagenesis of landslide processes and mud volcanism along with sedimentation regularities.

Multivariate analysis of heavy metal contents in soils, sediments and water in the region of Meknes (central Morocco).

PubMed

Tahri, M; Benyaïch, F; Bounakhla, M; Bilal, E; Gruffat, J J; Moutte, J; Garcia, D

2005-03-01

Concentrations of Al, Fe, Cr, Cu, Ni, Pb and Zn in soils, sediments and water samples collected along the Oued Boufekrane river (Meknes, central Morocco) were determined. In soils, a homogeneous distribution of metal concentrations was observed throughout the study area except for Pb, which presents high enrichment at sites located at the vicinity of a main highway. In sediments, high enrichment, with respect to upstream sites, were observed downstream of the city of Meknes for Al, Cr, Fe and Ni and inside the city for Cu, Zn and Pb. In water samples, the metal contents showed to correlate with their homologues in sediments suggesting that the metal contents in water and sediments have identical origins. Descriptive statistics and multivariate analysis (principal factor method, PFM) were used to assist the interpretation of elemental data. This allowed the determination of the correlations between the metals and the identification of three main factor loadings controlling the metal variability in soils and sediments.

Stimulated anoxic biodegradation of aromatic hydrocarbons using Fe(III) ligands

USGS Publications Warehouse

Lovley, D.R.; Woodward, J.C.; Chapelle, F.H.

1994-01-01

Contamination of ground waters with water-soluble aromatic hydrocarbons, common components of petroleum pollution, often produces anoxic conditions under which microbial degradation of the aromatics is slow. Oxygen is often added to contaminated ground water to stimulate biodegradation, but this can be technically difficult and expensive. Insoluble Fe(III) oxides, which are generally abundant in shallow aquifers, are alternative potential oxidants, but are difficult for microorganisms to access. Here we report that adding organic ligands that bind to Fe(III) dramatically increases its bioavailability, and that in the presence of these ligands, rates of degradation of aromatic hydrocarbons in anoxic aquifer sediments are comparable to those in oxic sediments. We find that even benzene, which is notoriously refractory in the absence of oxygen, can be rapidly degraded. Our results suggest that increasing the bioavailability of Fe(III) by adding suitable ligands provides a potential alternative to oxygen addition for the bioremediation of petroleum-contaminated aquifers.Contamination of ground waters with water-soluble aromatic hydrocarbons, common components of petroleum pollution, often produces anoxic conditions under which microbial degradation of the aromatics is slow. Oxygen is often added to contaminated ground water to stimulate biodegradation, but this can be technically difficult and expensive. Insoluble Fe(III) oxides, which are generally abundant in shallow aquifers, are alternative potential oxidants, but are difficult for microorganisms to access. Here we report that adding organic ligands that bind to Fe(III) dramatically increases its bioavailability, and that in the presence of these ligands, rates of degradation of aromatic hydrocarbons in anoxic aquifer sediments are comparable to those in oxic sediments. We find that even benzene, which is notoriously refractory in the absence of oxygen, can be rapidly degraded. Our results suggest that increasing the bioavailability of Fe(III) by adding suitable ligands provides a potential alternative to oxygen addition for the bioremediation of petroleum-contamined aquifers.

Distribution and variability of redox zones controlling spatial variability of arsenic in the Mississippi River Valley alluvial aquifer, southeastern Arkansas

USGS Publications Warehouse

Sharif, M.U.; Davis, R.K.; Steele, K.F.; Kim, B.; Hays, P.D.; Kresse, T.M.; Fazio, J.A.

2008-01-01

Twenty one of 118 irrigation water wells in the shallow (25-30??m thick) Mississippi River Valley alluvial aquifer in the Bayou Bartholomew watershed, southeastern Arkansas had arsenic (As) concentrations (< 0.5 to 77????g/L) exceeding 10????g/L. Sediment and groundwater samples were collected and analyzed from the sites of the highest, median, and lowest concentrations of As in groundwater in the alluvial aquifers located at Jefferson County, Arkansas. A traditional five-step sequential extraction was performed to differentiate the exchangeable, carbonate, amorphous Fe and Mn oxide, organic, and hot HNO3-leachable fraction of As and other compounds in sediments. The Chao reagent (0.25??M hydroxylamine hydrochloride in 0.25??M HCl) removes amorphous Fe and Mn oxides and oxyhydroxides (present as coatings on grains and amorphous minerals) by reductive dissolution and is a measure of reducible Fe and Mn in sediments. The hot HNO3 extraction removes mostly crystalline metal oxides and all other labile forms of As. Significant total As (20%) is complexed with amorphous Fe and Mn oxides in sediments. Arsenic abundance is not significant in carbonates or organic matter. Significant (40-70????g/kg) exchangeable As is only present at shallow depth (0-1??m below ground surface). Arsenic is positively correlated to Fe extracted by Chao reagent (r = 0.83) and hot HNO3 (r = 0.85). Arsenic extracted by Chao reagent decreases significantly with depth as compared to As extracted by hot HNO3. Fe (II)/Fe (the ratio of Fe concentration in the extracts of Chao reagent and hot HNO3) is positively correlated (r = 0.76) to As extracted from Chao reagent. Although Fe (II)/Fe increases with depth, the relative abundance of reducible Fe decreases noticeably with depth. The amount of reducible Fe, as well as As complexed to amorphous Fe and Mn oxides and oxyhydroxides decreases with depth. Possible explanations for the decrease in reducible Fe and its complexed As with depth include historic flushing of As and Fe from hydrous ferric oxides (HFO) by microbially-mediated reductive dissolution and aging of HFO to crystalline phases. Hydrogeochemical data suggests that the groundwater in the area falls in the mildly reducing (suboxic) to relatively highly reducing (anoxic) zone, and points to reductive dissolution of HFO as the dominant As release mechanism. Spatial variability of gypsum solubility and simultaneous SO42- reduction with co-precipitation of As and sulfide is an important limiting process controlling the concentration of As in groundwater in the area. ?? 2008 Elsevier B.V. All rights reserved.

Tracing redox processes during paleoclimatic changes in the Neoproterozoic: Stable chromium isotopic results from the Arroyo del Soldado Group (Ediacaran, Uruguay)

NASA Astrophysics Data System (ADS)

Frei, R.; Gaucher, C.

2007-12-01

Positive δ13C carbonate values, combined with the occurrence of Fe-rich cherts (oxide-facies BIF) and organic-rich black shales within the late Ediacaran (ca. 580-560 Ma) Yerbal Fm. of the Arroyo del Soldato Group (Uruguay) are compatible with paleoclimatic models which postulate that enhanced bioproductivity due to higher availability of nutrient (P, N, Fe) was essential for controlling Neoproterozoic glaciations. Tracing of associated redox processes (f.e. linked to oxygenation of bottom waters in restricted basins) that might have been responsible for the deposition of Fe-rich cherts (BIFs) is therefore an important tool to better understand the seawater changes during cold-warm periods. Besides the traditionally used Fe and Mo isotopic systems, the redox-sensitive element Cr (Cr(III); Cr(IV)) and its stable isotopes offer another complementary system to trace paleo-redox processes. We have applied Cr stable isotope systematics to a sequence of samples from a late Ediacaran sedimentary sequence in Uruguay, using a 52Cr-54Cr double spike (Schoenberg et al., Chem..Geol., subm.). The middle Yerbal Fm. is dominated by organic-rich, black shales and black dolostones (δ53Cr = -0.05‰), followed by organic-rich cherts (δ53Cr = +1.83 - +4.49 ‰) and BIF (δ53Cr = -0.31 +0.90 ‰) gradually changing into Fe-bearing, organic-rich cherts and shales (δ53Cr = -0.28 - -0.01 ‰), and another sequence with BIF and organic-rich cherts topped by carbonates of the lower Polanco Fm. (δ53Cr = -0.17 to -0.27 ‰). The strongly positively fractionated Cr isotopic signatures in organic-rich and Fe-rich cherts in the Yerbal Fm. may point to significant oxidation processes either directly in the seawater column and/or during early diagenetic processes at the sediment-water interface. While these strongly positive δ53Cr values are the first to be reported from Neoproterozoic sedimentary sequence, the exact nature of the chemical process that produced these anomalies is not yet understood. However, the occurrence of these anomalies in organic-rich and Fe-rich chemical sediments that were deposited in a period following a glacial (Gaskiers?) event is compatible with "Snowball Earth" scenarios whereby impulsive oxidation of the upper seawater was in response to ice cover retraction which allowed booming of the biosphere and concomitant oxidation of accumulated Fe2+ and subsequent precipitation of the Fe-oxyhydroxides to form the "BIF" during such epochs. Schoenberg et al. (subm.) The stable Cr isotope inventory of solid earth reservoirs determined by double-spike MC-ICP-MS. Chemical Geology

Stabilized chitosan/Fe(0)-nanoparticle beads to remove heavy metals from polluted sediments.

PubMed

Liu, T; Sun, Y; Wang, Z L

2016-01-01

Sediment contamination by heavy metals has become a widespread problem that can affect the normal behaviors of rivers and lakes. After chitosan/Fe(0)-nanoparticles (CS-NZVI) beads were cross-linked with glutaraldehyde (GLA), their mechanical strength, stability and separation efficiency from the sediment were obviously improved. Moreover, the average aperture size of GLA-CS-NZVI beads was 20.6 μm and NZVI particles were nearly spherical in shape with a mean diameter of 40.2 nm. In addition, the pH showed an insignificant effect on the removal rates from the sediment. Due to the dissolution of metals species into aqueous solutions as an introduction of the salt, the removal rates of all heavy metals from the sediment were increased with an increase of the salinity. The competitive adsorption of heavy metals between the sediment particles and GLA-CS-NZVI beads became stronger as the sediment particles became smaller, leading to decreased removal rates. Therefore, the removal efficiency could be enhanced by optimizing experimental conditions and choosing appropriate materials for the target contaminants.

Monitoring Uranium Transformations Determined by the Evolution of Biogeochemical Processes: Design of Mixed Batch Reactor and Column Studies at Oak Ridge National Laboratory

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

Criddle, Craig S.; Wu, Weimin

2013-04-17

With funds provided by the US DOE, Argonne National Laboratory subcontracted the design of batch and column studies to a Stanford University team with field experience at the ORNL IFRC, Oak Ridge, TN. The contribution of the Stanford group ended in 2011 due to budget reduction in ANL. Over the funded research period, the Stanford research team characterized ORNL IFRC groundwater and sediments and set up microcosm reactors and columns at ANL to ensure that experiments were relevant to field conditions at Oak Ridge. The results of microcosm testing demonstrated that U(VI) in sediments was reduced to U(IV) with themore » addition of ethanol. The reduced products were not uraninite but were instead U(IV) complexes associated with Fe. Fe(III) in solid phase was only partially reduced. The Stanford team communicated with the ANL team members through email and conference calls and face to face at the annual ERSP PI meeting and national meetings.« less

Molybdenum isotopes in modern marine hydrothermal Fe/Mn deposits: Implications for Archean and Paleoproterozoic Mo cycles

NASA Astrophysics Data System (ADS)

Goto, K. T.; Hein, J. R.; Shimoda, G.; Aoki, S.; Ishikawa, A.; Suzuki, K.; Gordon, G. W.; Anbar, A. D.

2016-12-01

Molybdenum isotope (δ98/95Mo) variations recorded in Archean and Paleoproterozoic Fe/Mn-rich sediments have been used to constrain ocean redox conditions at the time of deposition (Canfield et al., 2013 PNAS; Planavsky et al., 2014 Nat. Geo.; Kurzweil et al., 2015 GCA). However, except for hydrogenous Fe-Mn crusts (Siebert et al., 2003), δ98/95Mo variation of modern Fe and Mn oxide deposits has been poorly investigated. Marine hydrothermal systems are thought to be the major source of Fe and Mn in Archean and Paleoproterozoic Fe- and Mn-rich sediments. Hence, to accurately interpret Mo isotope data of those ancient sedimentary rocks, it is important to evaluate the possible influence of hydrothermally derived Mo on δ98/95Mo of modern Fe- and Mn-rich sediments. In this study, we analyzed Mo isotopic compositions of one hydrothermal Fe oxide and 15 Mn oxides from five different hydrothermal systems in the modern ocean. The Fe oxide is composed mainly of goethite, and has a δ98/95Mo of 0.7‰, which is 1.4‰ lighter than that of present-day seawater. The observed offset is similar to isotope fractionation observed during adsorption experiments of Mo on goethite (Δ98/95Mogoethite-solution = -1.4 ± 0.5%; Goldberg et al., 2009 GCA). The 15 hydrothermal Mn oxides show large variations in δ98/95Mo ranging from -1.7 to 0.5‰. However, most of the values are similar to those of modern hydrogenous Fe-Mn crusts (Siebert et al., 2003 EPSL), and fall within the range of estimated δ98/95Mo of Mn oxides precipitated from present-day seawater using the isotope offset reported from adsorption experiments (Δ98/95Mo = -2.7 ± 0.3‰; Wasylenki et al., 2008 GCA). These findings indicate that seawater is the dominant source of Mo for modern hydrothermal Fe and Mn deposits. However, the observed large variation indicates that the contribution Mo from local hydrothermal systems is not negligible. The oceanic Mo inventory during the Archean and Paleoproterozoic is thought to be much smaller than that of present-day (Scott et al., 2008 Nature). Hence, δ98/95Mo of Archean and Paleoproterozoic Fe- and Mn-rich sediments could be strongly influenced by hydrothermally derived Mo, which may contrast to modern hydrothermal deposits. Possible Archean and Paleoproterozoic Mo cycles constrained by these data will also be discussed.

Detailed seamount-scale studies of ferromanganese crusts reveal new insights into their formation and resource assessment.

NASA Astrophysics Data System (ADS)

Murton, B. J.; Lusty, P.; Yeo, I. A.; Howarth, S.

2017-12-01

The seafloor hosts abundant mineral deposits critical for low-carbon economies and emerging technologies. These include ferromanganese crusts (FeMnC) that grow on seamounts. While the broad distribution of FeMnC is known, local controls on growth, composition and formation are not. Here, we describe a detailed study of a gyot in the NE Atlantic (Tropic Seamount) that explores the controls, from the surface to the seafloor, exerted on FeMnC growth from current energy, surface productivity, sediment distribution, seafloor morphology, substrate lithology, sediments mobility and thickness, and seamount subsidence. During cruise JC142 (2016), we mapped the seamount with EM120 multibeam, mapped the 400km2 summit with AUV multibeam, sidescan sonar, sub-bottom profiler and 361,644 photographs. During 28 ROV dives we drilled 58 core and collected 344 individual rock samples. We found FeMnC at all depths, with the thickest (<20cm) located at the greatest depths (3000-4000m). The thinnest are on the summit plateau, with the centre and southern edge having the thickest sediment. FeMnC pavements form many different terraces on the summit. Frequent undercuts expose a calcareous substrate. Elsewhere, cobbles and pebbles form the nucleolus for crusts up to 10cm thick, with growth into the sediment. Many substrates are found to comprise semi-consolidated sediment. The presence of thick crusts at the base of the seamount contradicts accepted understanding of FeMnC deposition just below the oxygen minimum zone (OMZ). In areas on the eastern and western spurs, between 2500m and 1000m, where current energy is greatest, sessile fauna are most abundant. Dense coral debris at these locations appears to inhibit crust formation and coral and sponge `gardens' are frequent on near vertical cliffs. The observation that crusts have grown downwards into and over soft sediment is enigmatic since present understanding requires hard substrates to be exposed to seawater for crusts to grow, and any burial would inhibit such growth. Plume tracking shows reduction to background within 1000m. Our study challenges the view that ferromanganese crusts form at the base of the OMZ and grow upwards on solid substrates. Instead, we see an interplay between crust precipitation, the morphological evolution of the seamount, its hydrography and substrates.

Cenozoic marine geochemistry of thallium deduced from isotopic studies of ferromanganese crusts and pelagic sediments

USGS Publications Warehouse

Rehkamper, M.; Frank, M.; Hein, J.R.; Halliday, A.

2004-01-01

Cenozoic records of Tl isotope compositions recorded by ferromanganese (Fe-Mn) crusts have been obtained. Such records are of interest because recent growth surfaces of Fe-Mn crusts display a nearly constant Tl isotope fractionation relative to seawater. The time-series data are complemented by results for bulk samples and leachates of various marine sediments. Oxic pelagic sediments and anoxic marine deposits can be distinguished by their Tl isotope compositions. Both pelagic clays and biogenic oozes are typically characterized by ??205Tl greater than +2.5, whereas anoxic sediments have ??205Tl of less than -1.5 (??205Tl is the deviation of the 205Tl/203Tl isotope ratio of a sample from NIST SRM 997 Tl in parts per 104). Leaching experiments indicate that the high ??205Tl values of oxic sediments probably reflect authigenic Fe-Mn oxyhydroxides. Time-resolved Tl isotope compositions were obtained from six Fe-Mn crusts from the Atlantic, Indian, and Pacific oceans and a number of observations indicate that these records were not biased by diagenetic alteration. Over the last 25 Myr, the data do not show isotopic variations that significantly exceed the range of Tl isotope compositions observed for surface layers of Fe-Mn crusts distributed globally (??205 Tl=+12.8??1.2). This indicates that variations in deep-ocean temperature were not recorded by Tl isotopes. The results most likely reflect a constant Tl isotope composition for seawater. The growth layers of three Fe-Mn crusts that are older than 25 Ma show a systematic increase of ??205Tl with decreasing age, from about +6 at 60-50 Ma to about +12 at 25 Ma. These trends are thought to be due to variations in the Tl isotope composition of seawater, which requires that the oceans of the early Cenozoic either had smaller output fluxes or received larger input fluxes of Tl with low ??205Tl. Larger inputs of isotopically light Tl may have been supplied by benthic fluxes from reducing sediments, rivers, and/or volcanic emanations. Alternatively, the Tl isotope trends may reflect the increasing importance of Tl fluxes to altered ocean crust through time. ?? 2004 Elsevier B.V. All rights reserved.

Glacial influence on the geochemistry of riverine iron fluxes to the Gulf of Alaska and effects of deglaciation

USGS Publications Warehouse

Schroth, A.W.; Crusius, John; Chever, F.; Bostick, B.C.; Rouxel, O.J.

2011-01-01

Riverine iron (Fe) derived from glacial weathering is a critical micronutrient source to ecosystems of the Gulf of Alaska (GoA). Here we demonstrate that the source and chemical nature of riverine Fe input to the GoA could change dramatically due to the widespread watershed deglaciation that is underway. We examine Fe size partitioning, speciation, and isotopic composition in tributaries of the Copper River which exemplify a long-term GoA watershed evolution from one strongly influenced by glacial weathering to a boreal-forested watershed. Iron fluxes from glacierized tributaries bear high suspended sediment and colloidal Fe loads of mixed valence silicate species, with low concentrations of dissolved Fe and dissolved organic carbon (DOC). Iron isotopic composition is indicative of mechanical weathering as the Fe source. Conversely, Fe fluxes from boreal-forested systems have higher dissolved Fe concentrations corresponding to higher DOC concentrations. Iron colloids and suspended sediment consist of Fe (hydr)oxides and organic complexes. These watersheds have an iron isotopic composition indicative of an internal chemical processing source. We predict that as the GoA watershed evolves due to deglaciation, so will the source, flux, and chemical nature of riverine Fe loads, which could have significant ramifications for Alaskan marine and freshwater ecosystems.

Biolabile ferrous iron bearing nanoparticles in glacial sediments

NASA Astrophysics Data System (ADS)

Hawkings, Jon R.; Benning, Liane G.; Raiswell, Rob; Kaulich, Burkhard; Araki, Tohru; Abyaneh, Majid; Stockdale, Anthony; Koch-Müller, Monika; Wadham, Jemma L.; Tranter, Martyn

2018-07-01

Glaciers and ice sheets are a significant source of nanoparticulate Fe, which is potentially important in sustaining the high productivity observed in the near-coastal regions proximal to terrestrial ice cover. However, the bioavailability of particulate iron is poorly understood, despite its importance in the ocean Fe inventory. We combined high-resolution imaging and spectroscopy to investigate the abundance, morphology and valence state of particulate iron in glacial sediments. Our results document the widespread occurrence of amorphous and Fe(II)-rich and Fe(II)-bearing nanoparticles in Arctic glacial meltwaters and iceberg debris, compared to Fe(III)-rich dominated particulates in an aeolian dust sample. Fe(II) is thought to be highly biolabile in marine environments. Our work shows that glacially derived Fe is more labile than previously assumed, and consequently that glaciers and ice sheets are therefore able to export potentially bioavailable Fe(II)-containing nanoparticulate material to downstream ecosystems, including those in a marine setting. Our findings provide further evidence that Greenland Ice Sheet meltwaters may provide biolabile particulate Fe that may fuel the large summer phytoplankton bloom in the Labrador Sea, and that Fe(II)-rich particulates from a region of very high productivity downstream of a polar ice sheet may be glacial in origin.

Trace metal occurrence and distribution in sediments and mangroves, Pumicestone region, southeast Queensland, Australia.

PubMed

Preda, Micaela; Cox, Malcolm E

2002-11-01

The Pumicestone region is a unique catchment in northern Moreton Bay, southeast Queensland. The region supports a wide range of land-use activities as well as attractions such as nature conservation areas. One environmental aspect that has not previously been addressed in this area is the occurrence of minor and trace metals in estuarine sediments associated with the main estuaries of the region. The trace metals included in this investigation are: vanadium, chromium, molybdenum, cobalt, nickel, copper, zinc, cadmium, lead and arsenic. To determine and evaluate the occurrence and distribution of metals in the area, several components have been analysed: bedrock material, pre-industrial settings, recent estuarine sediments, soils of estuarine origin and mangrove pneumatophores. The 40 sites chosen for sediment and soil samples cover a variety of estuarine settings and represent a range of natural conditions in terms of channel and bank morphology, tidal energy, vegetation cover, relationship to bedrock, water salinity and land disturbance. The chemical, mineralogical and statistical analyses employed in this study enabled (a) establishment of background values for the area, (b) determination of relationships between metals and (c) identification of sites with anomalous metal concentrations. All the metals found in the sediments of the area are sourced from the geological bedrock. The dominant trace elements identified in sediments are Zn, V and Cr. The remaining metals are highly variable spatially. All trace metals are controlled by the presence of Fe and Mn oxides, and by the grainsize of the sediment. Typically, fine-grained Fe-rich materials tend to adsorb more trace metals than sandy sediments. In soils that have developed from estuarine muds, some metals such as Cr, Mo, Pb and As tend to be in larger quantities than in the estuarine counterparts. Some of the elements, which occur in significant amounts in the sediment, have been detected in mangrove tissue (Avicenniamarina) such as V, Cr, Zn, Fe and Mn. Of particular note is Cu, which is present in mangrove tissue in quantities many times exceeding the sediment concentration. The comparative analysis of pre-industrial settings and recent sediments and soils highlighted some areas of metal enrichment such as acid-affected sites where oxidation of pyrite has mobilised metals from sediments; these metals are then redistributed in Fe-rich surficial layers. Disturbed banks within the estuaries are also likely to have low levels of metal enrichment due to boating activities.

The shift of microbial communities and their roles in sulfur and iron cycling in a copper ore bioleaching system.

PubMed

Niu, Jiaojiao; Deng, Jie; Xiao, Yunhua; He, Zhili; Zhang, Xian; Van Nostrand, J D; Liang, Yili; Deng, Ye; Liu, Xueduan; Yin, Huaqun

2016-10-04

Bioleaching has been employed commercially to recover metals from low grade ores, but the production efficiency remains to be improved due to limited understanding of the system. This study examined the shift of microbial communities and S&Fe cycling in three subsystems within a copper ore bioleaching system: leaching heap (LH), leaching solution (LS) and sediment under LS. Results showed that both LH and LS had higher relative abundance of S and Fe oxidizing bacteria, while S and Fe reducing bacteria were more abundant in the Sediment. GeoChip analysis showed a stronger functional potential for S 0 oxidation in LH microbial communities. These findings were consistent with measured oxidation activities to S 0 and Fe 2+ , which were highest by microbial communities from LH, lower by those from LS and lowest form Sediment. Moreover, phylogenetic molecular ecological network analysis indicated that these differences might be related to interactions among microbial taxa. Last but not the least, a conceptual model was proposed, linking the S&Fe cycling with responsible microbial populations in the bioleaching systems. Collectively, this study revealed the microbial community and functional structures in all three subsystems of the copper ore, and advanced a holistic understanding of the whole bioleaching system.

The shift of microbial communities and their roles in sulfur and iron cycling in a copper ore bioleaching system

NASA Astrophysics Data System (ADS)

Niu, Jiaojiao; Deng, Jie; Xiao, Yunhua; He, Zhili; Zhang, Xian; van Nostrand, J. D.; Liang, Yili; Deng, Ye; Liu, Xueduan; Yin, Huaqun

2016-10-01

Bioleaching has been employed commercially to recover metals from low grade ores, but the production efficiency remains to be improved due to limited understanding of the system. This study examined the shift of microbial communities and S&Fe cycling in three subsystems within a copper ore bioleaching system: leaching heap (LH), leaching solution (LS) and sediment under LS. Results showed that both LH and LS had higher relative abundance of S and Fe oxidizing bacteria, while S and Fe reducing bacteria were more abundant in the Sediment. GeoChip analysis showed a stronger functional potential for S0 oxidation in LH microbial communities. These findings were consistent with measured oxidation activities to S0 and Fe2+, which were highest by microbial communities from LH, lower by those from LS and lowest form Sediment. Moreover, phylogenetic molecular ecological network analysis indicated that these differences might be related to interactions among microbial taxa. Last but not the least, a conceptual model was proposed, linking the S&Fe cycling with responsible microbial populations in the bioleaching systems. Collectively, this study revealed the microbial community and functional structures in all three subsystems of the copper ore, and advanced a holistic understanding of the whole bioleaching system.

The shift of microbial communities and their roles in sulfur and iron cycling in a copper ore bioleaching system

PubMed Central

Niu, Jiaojiao; Deng, Jie; Xiao, Yunhua; He, Zhili; Zhang, Xian; Van Nostrand, J. D.; Liang, Yili; Deng, Ye; Liu, Xueduan; Yin, Huaqun

2016-01-01

Bioleaching has been employed commercially to recover metals from low grade ores, but the production efficiency remains to be improved due to limited understanding of the system. This study examined the shift of microbial communities and S&Fe cycling in three subsystems within a copper ore bioleaching system: leaching heap (LH), leaching solution (LS) and sediment under LS. Results showed that both LH and LS had higher relative abundance of S and Fe oxidizing bacteria, while S and Fe reducing bacteria were more abundant in the Sediment. GeoChip analysis showed a stronger functional potential for S0 oxidation in LH microbial communities. These findings were consistent with measured oxidation activities to S0 and Fe2+, which were highest by microbial communities from LH, lower by those from LS and lowest form Sediment. Moreover, phylogenetic molecular ecological network analysis indicated that these differences might be related to interactions among microbial taxa. Last but not the least, a conceptual model was proposed, linking the S&Fe cycling with responsible microbial populations in the bioleaching systems. Collectively, this study revealed the microbial community and functional structures in all three subsystems of the copper ore, and advanced a holistic understanding of the whole bioleaching system. PMID:27698381

Geochemistry and magnetic sediment distribution at the western boundary upwelling system of southwest Atlantic

NASA Astrophysics Data System (ADS)

Cruz, Anna P. S.; Barbosa, Catia F.; Ayres-Neto, Arthur; Munayco, Pablo; Scorzelli, Rosa B.; Amorim, Nívea Santos; Albuquerque, Ana L. S.; Seoane, José C. S.

2018-02-01

In order to investigate the chemical and magnetic characteristics of sediments of the western boundary upwelling system of Southwest Atlantic we analyzed magnetic susceptibility, grain size distribution, total organic carbon, heavy mineral abundance, Fe associated with Mössbauer spectra, and Fe and Mn of pore water to evaluate the deposition patterns of sediments. Four box-cores were collected along a cross-shelf transect. Brazil Current and coastal plume exert a primary control at the inner and outer shelf cores, which exhibited similar depositional patterns characterized by a high abundance of heavy minerals (mean 0.21% and 0.08%, respectively) and very fine sand, whereas middle shelf cores presented low abundances of heavy minerals (mean 0.03%) and medium silt. The inner shelf was dominated by sub-angular grains, while in middle and outer shelf cores well-rounded grains were found. The increasing Fe3+:Fe2+ ratio from the inner to the outer shelf reflects farther distance to the sediment source. The outer shelf presented well-rounded minerals, indicating abrasive processes as a result of transport by the Brazil Current from the source areas. In the middle shelf, cold-water intrusion of the South Atlantic Central Water contributes to the primary productivity, resulting in higher deposition of fine sediment and organic carbon accumulation. The high input of organic carbon and the decreased grain size are indicative of changes in the hydrodynamics and primary productivity fueled by the western boundary upwelling system, which promotes loss of magnetization due to the induction of diagenesis of iron oxide minerals.

Platinum stable isotopes in ferromanganese crust and nodules

NASA Astrophysics Data System (ADS)

Corcoran, Loretta; Seward, Terry; Handler, Monica R.

2015-04-01

Hydrogenetic ferromanganese (Fe-Mn) crust and nodules are slow-growing chemical sediments that form by direct precipitation from seawater, resulting in a record of changing seawater chemistry. These sediments are the primary sink for platinum in the modern oxic marine environment, hosting well-documented enrichments over other platinum-group elements (PGEs): the Pt anomaly [1]. Platinum is a non-bio-essential, highly siderophile, transition metal with six stable isotopes (190Pt, 192Pt, 194Pt, 195Pt, 196Pt, and 198Pt) with several oxidation states (Pt0, Pt2+ and Pt4+). Platinum is generally considered to exist in the hydrosphere as Pt2+ although its behaviour in the marine environment is poorly constrained, and Pt4+may also be present. Variations in ocean redox state, together with changes in source fluxes to the oceans, may therefore lead to small variations (< ±1) in the stable isotopic composition of marine platinum, raising the potential of adding platinum to the growing arsenal of paleoceanographic tracers. A method has been developed to measure the platinum isotopic composition using double spike MC-ICPMS analysis [2]and applied to a global suite of modern Fe-Mn crust and nodules. Combining synchrotron XAFS analyses of platinum adsorbed onto Fe-Mn oxide and oxyhydroxide surfaces to determine oxidation state and bonding environment, with platinum stable isotopic measurements allowing us to evaluate both platinum incorporation onto these sediments and the associated degree of platinum isotopic fractionation. Leaching experiments conducted on platinum rich terrestrial materials underwent platinum stable isotopic measurement as an analogue for the Pt isotopic fractionation associated with continental weathering. [1] Hodge, V.F. et al. (1985) Earth and Planetary Science Letters, 72, 158-162. [2] Creech, J. et al. (2013) Journal of Analytical Atomic Spectrometry, 28. 853-865.

Toward an understanding of "Legacy P" - phosphorus sorption mechanisms in stream sediments as influenced by organic matter

NASA Astrophysics Data System (ADS)

Audette, Yuki; O'Halloran, Ivan P.; Nowell, Peter M.; Congreves, Katelyn; Voroney, R. Paul

2017-04-01

Water chemistry and phosphorus (P) forms were analyzed to determine the nature of legacy P in sediments of the West Holland River and the adjacent drainage canals of the Holland Marsh drainage system, located in southern Ontario, Canada. The river and canals route water from the intensively cropped muck polders of the Holland Marsh and drain Lake Simcoe. Sediment samples were characterized for mineralogy using X-ray diffraction techniques (XRD); total P (TP); and Ca, Fe, Mn, and Mg contents, as well as cation exchange capacity and organic matter (OM) content. Forms of sediment P in five depth sections (ranging from 0-15 cm depth) were characterized and quantified by sequential P fractionation chemistry. At all study sites, mobile P forms including organic P forms were found to be higher in surface sediments than in deeper sediments. The major P form within the sediments of the two canal sites, where the concentration of TP in the surface water was within the Ontario Provincial Water Quality Objectives (PWQO) of 0.03 mg P L-1, was Ca-bound P, indicating a low risk of soluble reactive P (SRP) release. A trace of apatite (a stable Ca-P mineral) was also detected in these sediments. Conversely, sediments collected from the West Holland River at sites located within the Holland Marsh exhibited a high risk of SRP release, and redox-sensitive P was the dominant P form in the sediment despite the surface water exhibiting higher concentration of Ca and alkaline pH. In addition, the concentrations of TP as measured in surface water samples taken from the site were 8 times greater than PWQO. In the sediments where the risk of SRP release was high, OM contents were also relatively high and traces of brushite (a labile Ca-P mineral) were detected. The formation of OM and cation complexes, such as OM-Fe complexes, may play an important role in regulating the fate of sediment-P forms through the adsorption of SRP. These OM-Fe complexes may inhibit the formation of more stable Ca-P minerals, even under neutral to alkaline conditions. Thus, where OM-Fe-P forms predominate, we predict a high risk of SRP release from sediments when water chemistry changes. In addition, OM may inhibit the transformation of labile Ca-P forms to more stable Ca-P minerals. Loading of OM affects the development of hypoxia in aquatic systems, and the accumulation of OM can promote the release of both SRP and dissolved organic C to downstream environments. This study provides evidence that the presence of OM in stream sediments influences P sorption mechanisms and is critical in understanding P biogeochemistry in freshwater environments.

Mobility and fractionation of Fe, Pb and Zn in river sediments from a silver and base-metals mining area: Taxco, México.

PubMed

Espinosa, E; Armienta, M A

2007-08-01

The impact of mining wastes on both the concentration and environmental mobility of Zn, Pb and Fe was studied in a shallow river. The studied tributary of the Taxco river is located south of the historical Ag, Zn, Cu and Pb mining area of Taxco, about 150 km south of México City. Methodology included total concentration determinations and sequential extraction analyses of the operational defined fractions of sediments. Results indicated that Fe, Pb and Zn concentrations are up to 5, 100 and 390 times respectively, greater than regional background concentrations. Higher contents of Pb and Zn were observed in the rainy season versus the dry season, whereas Fe was lower in the rainy season. Zinc and lead increased downflow in the dry season, and did not show any trend during the rainy season. Speciation showed that Zn was mainly linked to the carbonatic fraction (25-39%), to the hydrous Fe/Mn oxides fraction (15-25%) and to the organic matter and sulfide fraction (14-48%); lead was mainly associated to the hydrous Fe/Mn oxides (49-59%) and residual (22-39%) fractions; finally, iron was contained mainly in the residual (65-78%) and the hydrous Fe/Mn oxides fraction (15%). Mobility decreased according to the relation: Zn > Pb > Fe. Sediments were classified as strongly polluted in zinc, strongly to very strongly polluted in Pb, and moderately to strongly polluted in iron. However, a low proportion of metals in the exchangeable fractions, indicates low bioavailability. Limestone presence played a very important role on Zn and Pb fractionation and environmental mobility. Results show the importance of including geological background in river pollution studies.

Seasonal and spatial variabilities in northern Gulf of Alaska surface water iron concentrations driven by shelf sediment resuspension, glacial meltwater, a Yakutat eddy, and dust

NASA Astrophysics Data System (ADS)

Crusius, John; Schroth, Andrew W.; Resing, Joseph A.; Cullen, Jay; Campbell, Robert W.

2017-06-01

Phytoplankton growth in the Gulf of Alaska (GoA) is limited by iron (Fe), yet Fe sources are poorly constrained. We examine the temporal and spatial distributions of Fe, and its sources in the GoA, based on data from three cruises carried out in 2010 from the Copper River (AK) mouth to beyond the shelf break. April data are the first to describe late winter Fe behavior before surface water nitrate depletion began. Sediment resuspension during winter and spring storms generated high "total dissolvable Fe" (TDFe) concentrations of 1000 nmol kg-1 along the entire continental shelf, which decreased beyond the shelf break. In July, high TDFe concentrations were similar on the shelf, but more spatially variable, and driven by low-salinity glacial meltwater. Conversely, dissolved Fe (DFe) concentrations in surface waters were far lower and more seasonally consistent, ranging from 4 nmol kg-1 in nearshore waters to 0.6-1.5 nmol kg-1 seaward of the shelf break during April and July, despite dramatic depletion of nitrate over that period. The reasonably constant DFe concentrations are likely maintained during the year across the shelf by complexation by strong organic ligands, coupled with ample supply of labile particulate Fe. The April DFe data can be simulated using a simple numerical model that assumes a DFe flux from shelf sediments, horizontal transport by eddy diffusion, and removal by scavenging. Given how global change is altering many processes impacting the Fe cycle, additional studies are needed to examine controls on DFe in the Gulf of Alaska.

Redox Zonation and Oscillation in the Hyporheic Zone of the Ganges-Brahmaputra-Meghna Delta: Implications for the Fate of Groundwater Arsenic during Discharge

PubMed Central

Jung, Hun Bok; Zheng, Yan; Rahman, Mohammad W.; Rahman, Mohammad M.; Ahmed, Kazi M.

2015-01-01

Riverbank sediment cores and pore waters, shallow well waters, seepage waters and river waters were collected along the Meghna Riverbank in Gazaria Upazila, Bangladesh in Jan. 2006 and Oct.-Nov. 2007 to investigate hydrogeochemical processes controlling the fate of groundwater As during discharge. Redox transition zones from suboxic (0-2 m depth) to reducing (2-5 m depth) then suboxic conditions (5-7 m depth) exist at sites with sandy surficial deposits, as evidenced by depth profiles of pore water (n=7) and sediment (n=11; diffuse reflectance, Fe(III)/Fe ratios and Fe(III) concentrations). The sediment As enrichment zone (up to ~700 mg kg−1) is associated with the suboxic zones mostly between 0-2 m depth and less frequently between 5-7 m depth. The As enriched zones consist of several 5 to 10 cm-thick dispersed layers and span a length of ~5-15 m horizontally from the river shore. Depth profiles of riverbank pore water deployed along a 32 m transect perpendicular to the river shore show elevated levels of dissolved Fe (11.6±11.7 mg L−1) and As (118±91 μg L−1, mostly as arsenite) between 2-5 m depth, but lower concentrations between 0-2 m depth (0.13±0.19 mg L−1 Fe, 1±1 μg L−1 As) and between 5-6 m depth (1.14±0.45 mg L−1 Fe, 28±17 μg L−1 As). Because it would take more than a few hundred years of steady groundwater discharge (~10 m yr−1) to accumulate hundreds of mg kg−1 of As in the riverbank sediment, it is concluded that groundwater As must have been naturally elevated prior to anthropogenic pumping of the aquifer since the 1970s. Not only does this lend unequivocal support to the argument that As occurrence in the Ganges-Brahmaputra-Meghna Delta groundwater is of geogenic origin, it also calls attention to the fate of this As enriched sediment as it may recycle As into the aquifer. PMID:26855475

Vertical Geochemical Variations and Speciation Studies of As, Fe, Mn, Zn, and Cu in the Sediments of the Central Gangetic Basin: Sequential Extraction and Statistical Approach

PubMed Central

Ramanathan, AL.

2018-01-01

A geochemical and speciation study of As, Fe, Mn, Zn, and Cu was performed using sequential extraction and statistical approaches in the core sediments taken at two locations—Rigni Chhapra and Chaube Chhapra—of the central Gangetic basin (India). A gradual increase in the grain size (varying from clay to coarse sands) was observed in both the core profiles up to 30.5 m depth. The concentrations of analyzed elements ranged as follows: 6.9–14.2 mg/kg for As, 13,849–31,088 mg/kg for Fe, 267–711 mg/kg for Mn, 45–164 mg/kg for Cu for Rigni Chhapra while for Chaube Chhapra the range was 7.5–13.2 mg/kg for As, 10,936–37,052 mg/kg for Fe, 267–1052 mg/kg for Mn, 60–198 mg/kg for Zn and 60–108 mg/kg for Cu. Significant amounts (53–95%) of all the fractionated elemental concentrations were bound within the crystal structure of the minerals as a residual fraction. The reducible fraction was the second most dominant fraction for As (7% and 8%), Fe (3%), Mn (20% and 26%), and Cu (7% and 6%) respectively for both the cores. It may be released when aquifers subjected to changing redox conditions. The acid soluble fraction was of most interest because it could quickly mobilize into the water system which formed the third most dominating among all three fractions. Four color code of sediments showed an association with total As concentration and did not show a relation with any fraction of all elements analyzed. The core sediment was observed enriched with As and other elements (Cu, Fe, Mn, and Zn). However, it fell under uncontaminated to moderately contaminate which might exhibit a low risk in prevailing natural conditions. X-ray diffraction analyses indicated the availability of siderite and magnetite minerals in the core sediments in a section of dark grey with micaceous medium sand with organic matter (black). PMID:29360767

The influence of colloids on the geochemical behavior of metals in polluted water using as an example Yongdingxin River, Tianjin, China.

PubMed

Ren, Huimin; Liu, Huijuan; Qu, Jiuhui; Berg, Michael; Qi, Weixiao; Xu, Wei

2010-01-01

The role of colloids in estuarine and marine systems has been studied extensively in recent years, whereas less is known about the polluted freshwater system. Yongdingxin River is one of the major recipients of industrial effluents in Tianjin. This article evaluates the role of colloids in controlling geochemical behavior of Cu, Zn, Fe, Mn, Hg and Cr at the confluences between Yongdingxin River and its major tributaries Beijing Drainage River, Jinzhong River and Beitang Drainage River. Based on the distribution of metal partitioning among particulate (>0.22mum), colloidal (1kDa to 0.22mum) and truly dissolved (<1kDa) fractions, the metals can be assigned to the following groups: Group 1 - organic colloidal pool-borne elements Cu and Cr; Group 2 - inorganic colloidal pool-borne metals Fe and Mn; Group 3 - Zn and Hg characterized by varying complexation patterns. The distribution of metal partitioning among particulate, colloidal and truly dissolved fractions was influenced by anthropogenic input. In addition, the theoretical concentrations of elements in case of conservative mixing between the waters of Yongdingxin River and the waters of its tributaries were compared with the measured values to evaluate the geochemical role of colloids. The result showed that all of the metals presented a non-conservative mixing behavior. Addition of colloids resulted in the removal of metals from the water column to bed sediment during river water mixing, which was furthermore confirmed by the similar partition coefficient of metal concentration between colloid and sediment. Copyright 2009 Elsevier Ltd. All rights reserved.

The iron source in phreatomagmatic pipes in the Tunguska Basin (eastern Siberia): insights into hydrothermal-metasomatic leaching processes from Fe isotopes, microstructures, and mass balances.

NASA Astrophysics Data System (ADS)

John, Timm; Svensen, Henrik; Weyer, Stefan; Polozov, Alexander; Planke, Sverre

2010-05-01

The Siberian iron-bearing phreatomagmatic pipes represent world class Fe-ore deposit, and 5-6 are currently mined in eastern Siberia. The pipes formed within the vast Tunguska Basin, cutting thick accumulations of carbonates (dolostones) and evaporites (anhydrite, halite, dolostone). These sediments were intruded by the sub-volcanic part of the Siberian Traps at 252 Ma, and sills and dykes are abundant throughout the basin. The pipes formed during sediment-magma interactions in the deep parts of the basin, and the degassing is believed to have triggered the end-Permian environmental crisis. A major problem with understanding the pipe formation is related to the source of iron. Available hypotheses state that the iron was leached from a Fe-enriched magmatic melt that incorporated dolostones. It is currently unclear how the magmatic, hydrothermal, and sedimentary processes interacted to form the deposits, as there are no actual constraints to pin down the iron source. We hypothesize two end-member scenarios to account for the magnetite enrichment and deposition, which is testable by analyzing Fe-isotopes of magnetite: 1) Iron sourced from dolerite magma through leaching and metasomatism by chloride brines. 2) Leaching of iron from sedimentary rocks (shale, dolostone) during magma-sediment interactions. We focus on understanding the Fe-isotopic architecture of the pipes in order constrain the source of the Fe and the mechanism that caused this significant Fe redistribution. We further evaluate possible fractionation during fast metasomatic ore-forming process that took place soon after pipe formation.

Reconstructing the Mineralogy and Bioavailability of Dust-Borne Iron Deposited to the Southern Ocean through the Last Glacial Cycle

NASA Astrophysics Data System (ADS)

Shoenfelt, E. M.; Winckler, G.; Lamy, F.; Bostick, B. C.

2017-12-01

The iron (Fe) in dust deposited to the Fe-limited Southern Ocean plays an important role in ocean biogeochemistry and global climate. For instance, increases in dust-borne Fe deposition in the subantarctic Southern Ocean have been linked to increases in productivity and part of the CO2 drawdown of the last glacial cycle [1]. Notably, bioavailable Fe impacts productivity rather than total Fe. While it has long been understood that Fe mineralogy impacts Fe bioavailability in general, our understanding of the mineralogy of Fe in dust in specific is limited to that in modern dust sources. Reduced mineral Fe in dust has been shown to be more bioavailable than oxidized mineral iron, as it is more readily dissolved [2], and it is more easily utilized directly by a model diatom [3]. Our previous work focusing on South American dust sources shows that glacial activity is associated with higher Fe(II) fractions in dust-borne minerals, due to the physical weathering of Fe(II)-rich silicates in bedrock [3]. Thus, we hypothesize that there were higher Fe(II) fractions in dust deposited during cold glacial periods where ice sheets were more widespread. Using synchrotron-based X-ray absorption spectroscopy, we have reconstructed the mineralogy of Fe deposited to Southern Ocean sediment cores from the subantarctic South Atlantic (TN057-6/ODP Site 1090) and South Pacific (PS7/56-1) through the last glacial cycle, creating the first paleorecord of Fe mineralogy and its associated bioavailability. During cold glacial periods there is a higher fraction of reduced Fe - in the form of Fe(II) silicates - deposited to the sediments compared to warm interglacial periods. Thus, Fe(II) content is directly correlated with dust input. The presence of Fe(II) silicates rather than products of diagenesis such as pyrite suggests that these Fe(II) minerals are physically weathered from bedrock and preserved rather than produced in the sediment. This result suggests that not only was there more dust and Fe deposited to the Southern Ocean during glacial periods, glacial Fe was also more bioavailable due to the importance of glacial activity to high latitude dust formation. [1] A. Martinez-Garcia et al., Science 343 (2014). [2] A. W. Schroth et al., Nat. Geosci. 2 (2009). [3] E. M. Shoenfelt et al., Sci. Adv. 3(6), DOI:10.1126/sciadv.1700314 (2017).

Tourmaline mineralization in the Barberton greenstone belt, South Africa: early Archean metasomatism by evaporite-derived boron.

PubMed

Byerly, G R; Palmer, M R

1991-05-01

Tourmaline-rich rocks are common in the low-grade, interior portions of the Barberton greenstone belt of South Africa, where shallow-marine sediments and underlying altered basaltic and komatiitic lavas contain up to 50% tourmaline. The presence of tourmaline-bearing rip-up clasts, intraformational tourmaline pebbles and tourmaline-coated grains indicate that boron mineralization was a low-temperature, surficial process. The association of these lithologies with stromatolites, evaporites, and shallow-water sedimentary structures and the virtual absence of tourmaline in correlative deep-water facies rocks in the greenstone belt strengthens this model. Five tourmaline-bearing lithologic groups (basalts, komatiites, evaporite-bearing sediments, stromatolitic sediments, and quartz veins) are distinguished based on field, petrographic, and geochemical criteria. Individual tourmaline crystals within these lithologies show internal chemical and textural variations that reflect continued growth through intervals of change in bulk-rock and fluid composition accompanying one or more metasomatic events. Large single-crystal variations exist in Fe/Mg, Al/Fe, and alkali-site vacancies. A wide range in tourmaline composition exists in rocks altered from similar protoliths, but tourmalines in sediments and lavas have similar compositional variations. Boron-isotope analyses of the tourmalines suggest that the boron enrichment in these rocks has a major marine evaporitic component. Sediments with gypsum pseudomorphs and lavas altered at low temperatures by shallow-level brines have the highest delta 11B values (+2.2 to -1.9%); lower delta 11B values of late quartz veins (-3.7 to -5.7%) reflect intermediate temperature, hydrothermal remobilization of evaporitic boron. The delta 11B values of tourmaline-rich stromatolitic sediments (-9.8 and -10.5%) are consistent with two-stage boron enrichment, in which earlier marine evaporitic boron was hydrothermally remobilized and vented in shallow-marine or subaerial sites, mineralizing algal stromatolites. The stromatolite-forming algae preferentially may have lived near the sites of hydrothermal discharge in Archean times.

Influence of Oxygen and Nitrate on Fe (Hydr)oxide Mineral Transformation and Soil Microbial Communities during Redox Cycling.

PubMed

Mejia, Jacqueline; Roden, Eric E; Ginder-Vogel, Matthew

2016-04-05

Oscillations between reducing and oxidizing conditions are observed at the interface of anaerobic/oxic and anaerobic/anoxic environments, and are often stimulated by an alternating flux of electron donors (e.g., organic carbon) and electron acceptors (e.g., O2 and NO3(-)). In iron (Fe) rich soils and sediments, these oscillations may stimulate the growth of both Fe-reducing bacteria (FeRB) and Fe-oxidizing bacteria (FeOB), and their metabolism may induce cycling between Fe(II) and Fe(III), promoting the transformation of Fe (hydr)oxide minerals. Here, we examine the mineralogical evolution of lepidocrocite and ferrihydrite, and the adaptation of a natural microbial community to alternating Fe-reducing (anaerobic with addition of glucose) and Fe-oxidizing (with addition of nitrate or air) conditions. The growth of FeRB (e.g., Geobacter) is stimulated under anaerobic conditions in the presence of glucose. However, the abundance of these organisms depends on the availability of Fe(III) (hydr)oxides. Redox cycling with nitrate results in decreased Fe(II) oxidation thereby decreasing the availability of Fe(III) for FeRB. Additionally, magnetite is detected as the main product of both lepidocrocite and ferrihydrite reduction. In contrast, introduction of air results in increased Fe(II) oxidation, increasing the availability of Fe(III) and the abundance of Geobacter. In the lepidocrocite reactors, Fe(II) oxidation by dissolved O2 promotes the formation of ferrihydrite and lepidocrocite, whereas in the ferrihydrite reactors we observe a decrease in magnetite stoichiometry (e.g., oxidation). Understanding Fe (hydr)oxide transformation under environmentally relevant redox cycling conditions provides insight into nutrient availability and transport, contaminant mobility, and microbial metabolism in soils and sediments.

U(VI) bioreduction with emulsified vegetable oil as the electron donor--microcosm tests and model development.

PubMed

Tang, Guoping; Wu, Wei-Min; Watson, David B; Parker, Jack C; Schadt, Christopher W; Shi, Xiaoqing; Brooks, Scott C

2013-04-02

We conducted microcosm tests and biogeochemical modeling to study U(VI) reduction in contaminated sediments amended with emulsified vegetable oil (EVO). Indigenous microorganisms in the sediments degraded EVO and stimulated Fe(III), U(VI), and sulfate reduction, and methanogenesis. Acetate concentration peaked in 100-120 days in the EVO microcosms versus 10-20 days in the oleate microcosms, suggesting that triglyceride hydrolysis was a rate-limiting step in EVO degradation and subsequent reactions. Acetate persisted 50 days longer in oleate- and EVO- than in ethanol-amended microcosms, indicating that acetate-utilizing methanogenesis was slower in the oleate and EVO than ethanol microcosms. We developed a comprehensive biogeochemical model to couple EVO hydrolysis, production, and oxidation of long-chain fatty acids (LCFA), glycerol, acetate, and hydrogen, reduction of Fe(III), U(VI) and sulfate, and methanogenesis with growth and decay of multiple functional microbial groups. By estimating EVO, LCFA, and glycerol degradation rate coefficients, and introducing a 100 day lag time for acetoclastic methanogenesis for oleate and EVO microcosms, the model approximately matched observed sulfate, U(VI), and acetate concentrations. Our results confirmed that EVO could stimulate U(VI) bioreduction in sediments and the slow EVO hydrolysis and acetate-utilizing methanogens growth could contribute to longer term bioreduction than simple substrates (e.g., ethanol, acetate, etc.) in the subsurface.

Isolation of Geobacter species from diverse sedimentary environments

USGS Publications Warehouse

Coaxes, J.D.; Phillips, E.J.P.; Lonergan, D.J.; Jenter, H.; Lovley, D.R.

1996-01-01

In an attempt to better understand the microorganisms responsible for Fe(III) reduction in sedimentary environments, Fe(III)-reducing microorganisms were enriched for and isolated from freshwater aquatic sediments, a pristine deep aquifer, and a petroleum-contaminated shallow aquifer. Enrichments were initiated with acetate or toluene as the electron donor and Fe(III) as the electron acceptor. Isolations were made with acetate or benzoate. Five new strains which could obtain energy for growth by dissimilatory Fe(III) reduction were isolated. All five isolates are gram- negative strict anaerobes which grow with acetate as the electron donor and Fe(III) as the electron acceptor. Analysis of the 16S rRNA sequence of the isolated organisms demonstrated that they all belonged to the genus Geobacter in the delta subdivision of the Proteobacteria. Unlike the type strain, Geobacter metallireducens, three of the five isolates could use H2 as an electron donor fur Fe(III) reduction. The deep subsurface isolate is the first Fe(III) reducer shown to completely oxidize lactate to carbon dioxide, while one of the freshwater sediment isolates is only the second Fe(III) reducer known that can oxidize toluene. The isolation of these organisms demonstrates that Geobacter species are widely distributed in a diversity of sedimentary environments in which Fe(III) reduction is an important process.

Arsenic, vanadium, iron, and manganese biogeochemistry in a deltaic wetland, southern Louisiana, USA

DOE PAGES

Telfeyan, Katherine; Breaux, Alexander; Kim, Jihyuk; ...

2017-04-05

Geochemical cycling of the redox-sensitive trace elements arsenic (As) and vanadium (V) was examined in shallow pore waters from a marsh in an interdistributary embayment of the lower Mississippi River Delta. In particular, we explore how redox changes with depth and distance from the Mississippi River affect As and V cycling in the marsh pore waters. Previous geophysical surveys and radon mass balance calculations suggested that Myrtle Grove Canal and bordering marsh receive fresh groundwater, derived in large part from seepage of the Mississippi River, which subsequently mixes with brackish waters of Barataria Bay. In addition, the redox geochemistry ofmore » pore waters in the wetlands is affected by Fe and S cycling in the shallow subsurface (0-20 cm). Sediments with high organic matter content undergo SO 4 2- reduction, a process ubiquitous in the shallow subsurface but largely absent at greater depths (~3 m). Instead, at depth, in the absence of organic-rich sediments, Fe concentrations are elevated, suggesting that reduction of Fe(III) oxides/oxyhydroxides buffers redox conditions. Arsenic and V cycling in the shallow subsurface are decoupled from their behavior at depth, where both V and As appear to be removed from solution by either diffusion or adsorption onto, or co-precipitation with, authigenic minerals within the deeper aquifer sediments. Pore water As concentrations are greatest in the shallow subsurface (e.g., up to 315 nmol kg -1 in the top ~20 cm of the sediment) but decrease with depth, reaching values <30 nmol kg -1 at depths between 3 and 4 m. Vanadium concentrations appear to be tightly coupled to Fe cycling in the shallow subsurface, but at depth, V may be adsorbed to clay or sedimentary organic matter (SOM). Diffusive fluxes are calculated to examine the export of trace elements from the shallow marsh pore waters to the overlying canal water that floods the marsh. The computed fluxes suggest that the shallow sediment serves as a source of Fe, Mn, and As to the surface waters, whereas the sediments act as a sink for V. Iron and Mn fluxes are substantial, ranging from 50 to 30,000 and 770 to 4,300 nmol cm -2 day -1, respectively, whereas As fluxes are much less, ranging from 2.1 to 17 nmol cm -2 day -1. Vanadium fluxes range from 3.0 nmol cm -2 day -1 directed into the sediment to 1.7 nmol cm -2 day -1 directed out of the sediment« less

Arsenic, vanadium, iron, and manganese biogeochemistry in a deltaic wetland, southern Louisiana, USA

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

Telfeyan, Katherine; Breaux, Alexander; Kim, Jihyuk

Geochemical cycling of the redox-sensitive trace elements arsenic (As) and vanadium (V) was examined in shallow pore waters from a marsh in an interdistributary embayment of the lower Mississippi River Delta. In particular, we explore how redox changes with depth and distance from the Mississippi River affect As and V cycling in the marsh pore waters. Previous geophysical surveys and radon mass balance calculations suggested that Myrtle Grove Canal and bordering marsh receive fresh groundwater, derived in large part from seepage of the Mississippi River, which subsequently mixes with brackish waters of Barataria Bay. In addition, the redox geochemistry ofmore » pore waters in the wetlands is affected by Fe and S cycling in the shallow subsurface (0-20 cm). Sediments with high organic matter content undergo SO 4 2- reduction, a process ubiquitous in the shallow subsurface but largely absent at greater depths (~3 m). Instead, at depth, in the absence of organic-rich sediments, Fe concentrations are elevated, suggesting that reduction of Fe(III) oxides/oxyhydroxides buffers redox conditions. Arsenic and V cycling in the shallow subsurface are decoupled from their behavior at depth, where both V and As appear to be removed from solution by either diffusion or adsorption onto, or co-precipitation with, authigenic minerals within the deeper aquifer sediments. Pore water As concentrations are greatest in the shallow subsurface (e.g., up to 315 nmol kg -1 in the top ~20 cm of the sediment) but decrease with depth, reaching values <30 nmol kg -1 at depths between 3 and 4 m. Vanadium concentrations appear to be tightly coupled to Fe cycling in the shallow subsurface, but at depth, V may be adsorbed to clay or sedimentary organic matter (SOM). Diffusive fluxes are calculated to examine the export of trace elements from the shallow marsh pore waters to the overlying canal water that floods the marsh. The computed fluxes suggest that the shallow sediment serves as a source of Fe, Mn, and As to the surface waters, whereas the sediments act as a sink for V. Iron and Mn fluxes are substantial, ranging from 50 to 30,000 and 770 to 4,300 nmol cm -2 day -1, respectively, whereas As fluxes are much less, ranging from 2.1 to 17 nmol cm -2 day -1. Vanadium fluxes range from 3.0 nmol cm -2 day -1 directed into the sediment to 1.7 nmol cm -2 day -1 directed out of the sediment« less

Analysis of elements in lake sediment samples by PIXE spectrometry

NASA Astrophysics Data System (ADS)

Chelarescu, E. D.; Radulescu, C.; Stihi, C.; Bretcan, P.; Tanislav, D.; Dulama, I. D.; Stirbescu, R. M.; Teodorescu, S.; Bucurica, I. A.; Andrei, R.; Morarescu, C.

2017-09-01

This work aims to determine the concentrations of several elements (e.g. Pb, Ni, Zn, Mn, Cr, and Fe) from lake sediments, in order to characterize their origin and evolution. Particle Induced X-ray Emission (PIXE) technique using the 3 MV Tandetron™ particle accelerator from National Institute for R&D in Physics and Nuclear Engineering "Horia Hulubei" (IFIN-HH), Magurele-Bucharest, Romania, was applied. Sediment cores from different salt lakes from Romania (i.e. Amara Lake, Caineni Lake, and Movila Miresii Lake) were collected, in August 2015. The content of Pb, Cr, Mn, Fe, and Ni from sediment samples show similarities with other data presented in literature and international regulation. The Zn was the only element with a higher content in all samples (e.g. maximum 401.7-517.3 mg/kg d.w.).

The fate of arsenic in sediments formed at a river confluence affected by acid mine drainage

NASA Astrophysics Data System (ADS)

Guerra, P. A.; Pasten, P. A.; Pizarro, G.; Simonson, K.; Escauriaza, C. R.; Gonzalez, C.; Bonilla, C.

2012-12-01

Fluvial confluences receiving acid mine drainage may play a critical role in a watershed as a suite of interactions between chemistry and hydrodynamics occur, determining the fate of toxic contaminants like arsenic. Solid reactive phases of iron and/or aluminum oxi-hydroxides may form or transform, ranging from iron oxide nanoparticles that aggregate and form floccules that are transported in the suspended load up to gravel and arsenic-rich rock coatings. In order to further understand the role of reactive fluvial confluences, we have studied the mixing between the Caracarani River (flow=170-640 L/s, pH 8, conductivity 1.5 mS/cm, total As<0.1 mg/L and total Fe< 5 mg/L) and the Azufre River (flow=45-245 L/s, pH<2, conductivity > 10 mS/cm, total As>2 mg/L, total Fe=35-125 mg/L), located in the Lluta watershed in northern Chile. This site is an excellent natural laboratory located in a water-scarce area, where the future construction of a dam has prompted the attention of decision makers and scientists interested in weighing the risks derived by the accumulation of arsenic-rich sediments. Suspended sediments (> 0.45 μm), riverbed sediments, and coated rocks were collected upstream and downstream from the confluence. Suspended sediments >0.45 μm and riverbed sediments were analyzed by total reflection x-ray fluorescence for metals, while coated river bed rocks were analyzed by chemical extractions and a semi-quantitative approach through portable x-ray fluorescence. Water from the Caracarani and Azufre rivers were mixed in the laboratory at different ratios and mixing velocities aiming to characterize the effect of the chemical-hydrodynamic environment where arsenic solids were formed at different locations in the confluence. Despite a wide range of iron and arsenic concentrations in the suspended sediments from the field (As=1037 ± 1372 mg/kg, Fe=21.0 ± 24.5 g/kg), we found a rather narrow As/Fe ratio, increasing from 36.5 to 55.2 mgAs/kgFe when the bulk water pH increased from 3 to 6. Sequential extraction analyses suggest that ~80% of As in the solid pahse is strongly sorbed to the sediments, whereas ~15% of As is forming co-precipitated phase. Riverbed sediments (sand and gravel) showed much lower concentrations of Fe and As (17.1 ± 3.0 g/kg and 67.5 ± 53.9 mg/kg, respectively), owing to a dilution from non-reactive phases like quartz from sand. Coated rocks showed concentrations of Fe and As of 34.8 ± 12.5 g/kg and 680 ± 401 mg/kg, respectively, suggesting the coatings are possibly constituted by As-rich particles sequestered from the flow. In the case of the laboratory mixing tests, suspended solids ranged from 10 to 60 mg/L, with higher values at lower mixing ratios or higher pHs. Our findings suggest that the spatial and temporal variability driven by the hydrodynamics of a confluence determine distinct geochemical characteristics of arsenic-rich solid phases, thus playing a role in the fate of reactive contaminants like arsenic in the watershed. Research funded by Fondecyt project 1100943.

Uranium fate in wetland mesocosms: Effects of plants at two iron loadings with different pH values.

PubMed

Koster van Groos, Paul G; Kaplan, Daniel I; Chang, Hyun-Shik; Seaman, John C; Li, Dien; Peacock, Aaron D; Scheckel, Kirk G; Jaffé, Peter R

2016-11-01

Small-scale continuous flow wetland mesocosms (∼0.8 L) were used to evaluate how plant roots under different iron loadings affect uranium (U) mobility. When significant concentrations of ferrous iron (Fe) were present at circumneutral pH values, U concentrations in root exposed sediments were an order of magnitude greater than concentrations in root excluded sediments. Micro X-ray absorption near-edge structure (μ-XANES) spectroscopy indicated that U was associated with the plant roots primarily as U(VI) or U(V), with limited evidence of U(IV). Micro X-ray fluorescence (μ-XRF) of plant roots suggested that for high iron loading at circumneutral pH, U was co-located with Fe, perhaps co-precipitated with root Fe plaques, while for low iron loading at a pH of ∼4 the correlation between U and Fe was not significant, consistent with previous observations of U associated with organic matter. Quantitative PCR analyses indicated that the root exposed sediments also contained elevated numbers of Geobacter spp., which are likely associated with enhanced iron cycling, but may also reduce mobile U(VI) to less mobile U(IV) species. Copyright © 2016 Elsevier Ltd. All rights reserved.

Distribution and solid-phase speciation of toxic heavy metals of bed sediments of Bharali tributary of Brahmaputra River.

PubMed

Hoque, Raza Rafiqul; Goswami, K G; Kusre, B C; Sarma, K P

2011-06-01

Heavy metal (Fe, Mn, Zn, Cu, Ni, Pb, and Cd) concentrations and their chemical speciations were investigated for the first time in bed sediments of Bharali River, a major tributary of the Brahmaputra River of the Eastern Himalayas. Levels of Fe, Mn, Pb, and Cd in the bed sediments were much below the average Indian rivers; however, Cu and Zn exhibit levels on the higher side. Enrichment factors (EF) of all metals was greater than 1 and a higher trend of EF was seen in the abandoned channel for most metals. Pb showed maximum EF of 32 at site near an urban center. The geoaccumulation indices indicate that Bharali river is moderately polluted. The metals speciations, done by a sequential extraction regime, show that Cd, Cu, and Pb exhibit considerable presence in the exchangeable and carbonate fraction, thereby showing higher mobility and bioavailability. On the other hand, Ni, Mn, and Fe exhibit greater presence in the residual fraction and Zn was dominant in the Fe-Mn oxide phase. Inter-species correlations at three sites did not show similar trends for metal pairs indicating potential variations in the contributing sources.

Effect of Organic Substances on the Efficiency of Fe(Ii) to Fe(Iii) Oxidation and Removal of Iron Compounds from Groundwater in the Sedimentation Process

NASA Astrophysics Data System (ADS)

Krupińska, Izabela

2017-09-01

One of the problems with iron removal from groundwater is organic matter. The article presents the experiments involved groundwater samples with a high concentration of total iron - amounting to 7.20 mgFe/dm3 and an increased amount of organic substances (TOC from 5.50 to 7.50 mgC/dm3). The water samples examined differed in terms of the value of the ratio of the TOC concentration and the concentration of total iron (D). It was concluded that with increase in the coexistence ratio of organic substances and total iron in water (D = [TOC]/[Fetot]), efficiency of Fe(II) to Fe(III) oxidization with dissolved oxygen decreased, while the oxidation time was increasing. This rule was not demonstrated for potassium manganate (VII) when used as an oxidizing agent. The application of potassium manganate (VII) for oxidation of Fe(II) ions produced the better results in terms of total iron concentration reduction in the sedimentation process than the oxidation with dissolved oxygen.

IMPACTS OF IRON, NUTRIENTS, AND MINERAL FINES ON ANAEROBIC BIODEGRADATION OF CANOLA OIL IN FRESHWATER SEDIMENTS

EPA Science Inventory

Factors affecting anaerobic biodegradation kinetics of canola oil in freshwater sediments were investigated. An optimum dose of ferric hydroxide (10.5 g Fe(III)·kg^-1 sediment) was found to stimulate anaerobic biodegradation of canola oil (18.6 g oil kg^-1). ...

TOTAL AND BIOAVAILABLE METALS AT MARINA SEDIMENTS IN LAKE TEXOMA

EPA Science Inventory

Total and bioavailable metals in sediments were measured at marina areas in Lake Texoma during the fall of 2001. The metals most often found in the highest concentrations in sediments were Ca (56811 mg/kg) and Al (31095 mg/kg), followed by Fe (19393 mg/kg), K (6089 mg/kg), and Mg...

Fractionation of iron isotopes during leaching of natural particles by acidic and circumneutral leaches and development of an optimal leach for marine particulate iron isotopes

NASA Astrophysics Data System (ADS)

Revels, Brandi N.; Zhang, Ruifeng; Adkins, Jess F.; John, Seth G.

2015-10-01

Iron (Fe) is an essential nutrient for life on land and in the oceans. Iron stable isotope ratios (δ56Fe) can be used to study the biogeochemical cycling of Fe between particulate and dissolved phases in terrestrial and marine environments. We have investigated the dissolution of Fe from natural particles both to understand the mechanisms of Fe dissolution, and to choose a leach appropriate for extracting labile Fe phases of marine particles. With a goal of finding leaches which would be appropriate for studying dissolved-particle interactions in an oxic water column, three particle types were chosen including oxic seafloor sediments (MESS-3), terrestrial dust (Arizona Test Dust - A2 Fine), and ocean sediment trap material from the Cariaco basin. Four leaches were tested, including three acidic leaches similar to leaches previously applied to marine particles and sediments (25% acetic acid, 0.01 N HCl, and 0.5 N HCl) and a pH 8 oxalate-EDTA leach meant to mimic the dissolution of particles by organic complexation, as occurs in natural seawater. Each leach was applied for three different times (10 min, 2 h, 24 h) at three different temperatures (25 °C, 60 °C, 90 °C). MESS-3 was also leached under various redox conditions (0.02 M hydroxylamine hydrochloride or 0.02 M hydrogen peroxide). For all three sample types tested, we find a consistent relationship between the amount of Fe leached and leachate δ56Fe for all of the acidic leaches, and a different relationship between the amount of Fe leached and leachate δ56Fe for the oxalate-EDTA leach, suggesting that Fe was released through proton-promoted dissolution for all acidic leaches and by ligand-promoted dissolution for the oxalate-EDTA leach. Fe isotope fractionations of up to 2‰ were observed during acidic leaching of MESS-3 and Cariaco sediment trap material, but not for Arizona Test Dust, suggesting that sample composition influences fractionation, perhaps because Fe isotopes are greatly fractionated during leaching of silicates and clays but only minimally fractionated during dissolution of Fe oxyhydroxides. Two different analytical models were developed to explain the relationship between amount of Fe leached and δ56Fe, one of which assumes mixing between two Fe phases with different δ56Fe and different dissolution rates, and the other of which assumes dissolution of a single phase with a kinetic isotope effect. We apply both models to fit results from the acidic leaches of MESS-3 and find that the fit for both models is very similar, suggesting that isotope data will never be sufficient to distinguish between these two processes for natural materials. Next, we utilize our data to choose an optimal leach for application to marine particles. The oxalate-EDTA leach is well-suited to this purpose because it does not greatly fractionate Fe isotopes for a diversity of particle types over a wide variety of leaching conditions, and because it approximates the conditions by which particulate Fe dissolves in the oceans. We recommend a 2 h leach at 90 °C with 0.1 M oxalate and 0.05 M EDTA at pH 8 to measure labile ;ligand-leachable; particulate δ56Fe on natural marine materials with a range of compositions.

The anaerobic degradation of organic matter in Danish coastal sediments - Iron reduction, manganese reduction, and sulfate reduction

NASA Technical Reports Server (NTRS)

Canfield, Donald E.; Thamdrup, BO; Hansen, Jens W.

1993-01-01

A combination of porewater and solid phase analysis as well as a series of sediment incubations are used to quantify organic carbon oxidation by dissimilatory Fe reduction, Mn reduction, and sulfate reduction, in sediments from the Skagerrak (located off the northeast coast of Jutland, Denmark). Solid phase data are integrated with incubation results to define the zones of the various oxidation processes. At S(9), surface Mn enrichments of up to 3.5 wt pct were found, and with such a ready source of Mn, dissimilatory Mn reduction was the only significant anaerobic process of carbon oxidation in the surface 10 cm of the sediment. At S(4) and S(6), active Mn reduction occurred; however, most of the Mn reduction may have resulted from the oxidation of acid volatile sulfides and Fe(2+) rather than by a dissimilatory sulfate. Dissolved Mn(2+) was found to completely adsorb onto sediment containing fully oxidized Mn oxides.

Distribution patterns of particulate trace metals in the water column and nepheloid layer of the Gulf of Riga.

PubMed

Poikāne, Rita; Carstensen, Jacob; Dahllöf, Ingela; Aigars, Juris

2005-07-01

The dynamics (fate) of trace metals in suspended particulate matter within the Gulf of Riga has not yet been adequately addressed in the scientific literature. Therefore, during a two year period (2001-2002) samples of suspended particulate matter and surface sediments for trace metal analysis were collected in the Gulf of Riga and the Daugava river, and these data were combined with background information from the national marine monitoring program in Latvia. This paper presents a descriptive study of solid phase trace metals (aluminium, iron, cadmium, chromium, copper, manganese, nickel, lead and zinc) dynamics and their spatial distribution within the Gulf of Riga based on Principal Component Analysis and Cluster analysis. Fluvial particulate matter and particulate Al, Fe, Cr and Ni were brought into the Gulf of Riga mainly during spring flood and thereafter quickly diluted by the water masses of the Gulf of Riga. Fine-grained suspended material and particulate Al and Fe were well mixed and evenly distributed through all deepwater basins of the Gulf of Riga. The increase of particulate Mn below the thermocline in August and a strong negative correlation with dissolved oxygen concentrations suggested that particulate Mn in the water column and the sediments were regulated mainly by changing oxic-anoxic conditions in the sediments of the Gulf of Riga. The observed correlation between Al and Fe in the water column is in contrast to that observed in the nepheloid layer where Fe correlated with Mn, obviously due to fast diagenetic processes on sediment surface. The observed negative correlation of Cd and Zn with total carbon and total nitrogen in the nepheloid layer might indicate different sedimentation mechanisms of these elements, however, this assumption is still inconclusive.

Investigating redox processes under diffusive and advective flow conditions using a coupled omics and synchrotron approach

NASA Astrophysics Data System (ADS)

Kemner, K. M.; Boyanov, M.; Flynn, T. M.; O'Loughlin, E. J.; Antonopoulos, D. A.; Kelly, S.; Skinner, K.; Mishra, B.; Brooks, S. C.; Watson, D. B.; Wu, W. M.

2015-12-01

FeIII- and SO42--reducing microorganisms and the mineral phases they produce have profound implications for many processes in aquatic and terrestrial systems. In addition, many of these microbially-catalysed geochemical transformations are highly dependent upon introduction of reactants via advective and diffusive hydrological transport. We have characterized microbial communities from a set of static microcosms to test the effect of ethanol diffusion and sulfate concentration on UVI-contaminated sediment. The spatial distribution, valence states, and speciation of both U and Fe were monitored in situ throughout the experiment by synchrotron x-ray absorption spectroscopy, in parallel with solution measurements of pH and the concentrations of sulfate, ethanol, and organic acids. After reaction initiation, a ~1-cm thick layer of sediment near the sediment-water (S-W) interface became visibly dark. Fe XANES spectra of the layer were consistent with the formation of FeS. Over the 4 year duration of the experiment, U LIII-edge XANES indicated reduction of U, first in the dark layer and then throughout the sediment. Next, the microcosms were disassembled and samples were taken from the overlying water and different sediment regions. We extracted DNA and characterized the microbial community by sequencing 16S rRNA gene amplicons with the Illumina MiSeq platform and found that the community evolved from its originally homogeneous composition, becoming significantly spatially heterogeneous. We have also developed an x-ray accessible column to probe elemental transformations as they occur along the flow path in a porous medium with the purpose of refining reactive transport models (RTMs) that describe coupled physical and biogeochemical processes in environmental systems. The elemental distribution dynamics and the RTMs of the redox driven processes within them will be presented.

Laboratory Investigation of Complex Conductivity and Magnetic Susceptibility on Natural Iron Oxide Coated Sand

NASA Astrophysics Data System (ADS)

Wang, C.; Slater, L. D.; Day-Lewis, F. D.; Briggs, M. A.

2017-12-01

Redox reactions occurring at the oxic/anoxic interface where groundwater discharges to surface water commonly result in iron oxide deposition that coats sediment grains. With relatively large total surface area, these iron oxide coated sediments serve as a sink for sorption of dissolved contaminants, although this sink may be temporary if redox conditions fluctuate with varied flow conditions. Characterization of the distribution of iron oxides in streambed sediments could provide valuable understanding of biogeochemical reactions and the ability of a natural system to sorb contaminants. Towards developing a field methodology, we conducted laboratory spectral induced polarization (SIP) and magnetic susceptibility (MS) measurements on natural iron oxide coated sand (Fe-sand) with grain sizes ranging from 0.3 to 2.0 mm in order to assess the sensitivity of these measurements to iron oxides in sediments. The Fe-sand was also sorted by sieving into various grain sizes to study the impact of grain size on the polarization mechanisms. The unsorted Fe-sand saturated with 0.01 S/m NaCl solution exhibited a distinct phase response ( > 4 mrad) in the frequency range from 0.001 to 100 Hz whereas regular silica sand was characterized by a phase response less than 1 mrad under the same conditions. The presence of iron oxide substantially increased MS (3.08×10-3 SI) over that of regular sand ( < 10-5 SI). An increase of both phase peak and relaxation time was found with increasing grain size of the sorted Fe-sand. Laboratory results demonstrated that SIP and MS may be well suited to mapping the distribution of iron oxides in streambed sediments associated with anoxic groundwater discharge.

Fe-oxide mineralogy of the Jiujiang red earth sediments and implications for Quaternary climate change, southern China.

PubMed

Yin, Ke; Hong, Hanlie; Algeo, Thomas J; Churchman, Gordon Jock; Li, Zhaohui; Zhu, Zongmin; Fang, Qian; Zhao, Lulu; Wang, Chaowen; Ji, Kaipeng; Lei, Weidong; Duan, Zhenggang

2018-02-26

Diffuse reflectance spectrophotometry (DRS) is a new, fast, and reliable method to characterize Fe-oxides in soils. The Fe-oxide mineralogy of the Jiujiang red earth sediments was investigated using DRS to investigate the climate evolution of southern China since the mid-Pleistocene. The DRS results show that hematite/(hematite + goethite) ratios [Hm/(Hm + Gt)] exhibit an upward decreasing trend within the Jiujiang section, suggesting a gradual climate change from warm and humid in the middle Pleistocene to cooler and drier in the late Pleistocene. Upsection trends toward higher (orthoclase + plagioclase)/quartz ratios [(Or + Pl)/Q] and magnetic susceptibility values (χ lf ) support this inference, which accords with global climate trends at that time. However, higher-frequency climatic subcycles observed in loess sections of northern China are not evident in the Jiujiang records, indicating a relatively lower climate sensitivity of the red earth sediments in southern China.

Extraterrestrial platinum group nuggets in deep-sea sediments

NASA Technical Reports Server (NTRS)

Brownlee, D. E.; Bates, B. A.; Wheelock, M. M.

1984-01-01

A previously unrecognized property of iron cosmic spheres is reported. The most common spheres larger than 300 microns do not, in fact, contain FeNi metal cores, but instead contain a micrometer-sized nugget composed almost entirely of platinum group elements. These elements appear to have been concentrated by the oxidation of molten meteoritic metal during atmospheric entry. This process is critically dependent on the relative abundance of oxygen in the atmosphere, and the first appearance of the nuggets in the geological record may provide a marker indicating when the oxygen abundance attained half of its present level.

Calcium phosphate formation due to pH-induced adsorption/precipitation switching along salinity gradients

NASA Astrophysics Data System (ADS)

Oxmann, J. F.; Schwendenmann, L.

2014-07-01

Mechanisms governing phosphorus (P) speciation in coastal sediments remain unknown due to the diversity of coastal environments and poor analytical specificity for P phases. We investigated P speciation along salinity gradients comprising diverse ecosystems in a P-enriched estuary. To determine P load effects on P speciation we compared the high P site with a P-unenriched site. To improve analytical specificity, octacalcium phosphate (OCP), authigenic apatite (carbonate fluorapatite; CFAP) and detrital apatite (fluorapatite) were quantitated in addition to Al/Fe-bound P (Al/Fe-P) and Ca-bound P (Ca-P). Sediment pH primarily affected P fractions across ecosystems and independent of the P status. Increasing pH caused a pronounced downstream transition from adsorbed Al/Fe-P to mineral Ca-P. Downstream decline in Al/Fe-P was counterbalanced by the precipitation of Ca-P. This marked upstream-to-downstream switch occurred at near-neutral sediment pH and was enhanced by increased P loads. Accordingly, the site comparison indicated two location-dependent accumulation mechanisms at the P-enriched site, which mainly resulted in elevated Al/Fe-P at pH < 6.6 (upstream; adsorption) and elevated Ca-P at pH > 6.6 (downstream; precipitation). Enhanced Ca-P precipitation by increased loads was also evident from disproportional accumulation of metastable Ca-P (Ca-PMmeta). The average Ca-Pmeta concentration was six-fold, whereas total Ca-P was only twofold higher at the P-enriched site compared to the P-unenriched site. Species concentrations showed that these largely elevated Ca-Pmeta levels resulted from transformation of fertilizer-derived Al/Fe-P to OCP and CFAP due to decreasing acidity from land to the sea. Formation of OCP and CFAP results in P retention in coastal zones, which may lead to substantial inorganic P accumulation by anthropogenic P input in near-shore sediments.

The Impact of Gamma Radiation on Sediment Microbial Processes

PubMed Central

Brown, Ashley R.; Boothman, Christopher; Pimblott, Simon M.

2015-01-01

Microbial communities have the potential to control the biogeochemical fate of some radionuclides in contaminated land scenarios or in the vicinity of a geological repository for radioactive waste. However, there have been few studies of ionizing radiation effects on microbial communities in sediment systems. Here, acetate and lactate amended sediment microcosms irradiated with gamma radiation at 0.5 or 30 Gy h−1 for 8 weeks all displayed NO3− and Fe(III) reduction, although the rate of Fe(III) reduction was decreased in 30-Gy h−1 treatments. These systems were dominated by fermentation processes. Pyrosequencing indicated that the 30-Gy h−1 treatment resulted in a community dominated by two Clostridial species. In systems containing no added electron donor, irradiation at either dose rate did not restrict NO3−, Fe(III), or SO42− reduction. Rather, Fe(III) reduction was stimulated in the 0.5-Gy h−1-treated systems. In irradiated systems, there was a relative increase in the proportion of bacteria capable of Fe(III) reduction, with Geothrix fermentans and Geobacter sp. identified in the 0.5-Gy h−1 and 30-Gy h−1 treatments, respectively. These results indicate that biogeochemical processes will likely not be restricted by dose rates in such environments, and electron accepting processes may even be stimulated by radiation. PMID:25841009

Effects of four different phosphorus-locking materials on sediment and water quality in Xi'an moat.

PubMed

Wang, Guanbai; Wang, Yi; Guo, Yu; Peng, Dangcong

2017-01-01

To lower phosphorus concentration in Xi'an moat, four different phosphorus-locking materials, namely, calcium nitrate, sponge-iron, fly ash, and silica alumina clay, were selected in this experiment to study their effects on water quality and sediment. Results of the continuous 68-day experiment showed that calcium nitrate was the most effective for controlling phosphorus concentration in overlying and interstitial water, where the efficiency of locking phosphorus was >97 and 90 %, respectively. Meanwhile, the addition of calcium nitrate caused Fe/Al-bound phosphorus (Fe/Al-P) content in sediment declining but Ca-bound phosphorus (Ca-P) and organic phosphorus (OP) content ascending. The phosphorus-locking efficiency of sponge-iron in overlying and interstitial water was >72 and 66 %, respectively. Meanwhile, the total phosphorus (TP), OP, Fe/Al-P, and Ca-P content in sediment increased by 33.8, 7.7, 23.1, and 23.1 %, respectively, implying that under the action of sponge-iron, the locked phosphorus in sediment was mainly inorganic form and the phosphorus-locking efficiency of sponge-iron could be stable and persistent. In addition, the phosphorus-locking efficiency of fly ash was transient and limited, let alone silica alumina clay had almost no capacity for phosphorus-locking efficiency. Therefore, calcium nitrate and sponge-iron were excellent phosphorus-locking agents to repair the seriously polluted water derived from an internal source.

Geochemical baseline level and function and contamination of phosphorus in Liao River Watershed sediments of China.

PubMed

Liu, Shaoqing; Wang, Jing; Lin, Chunye; He, Mengchang; Liu, Xitao

2013-10-15

The quantitative assessment of P contamination in sediments is a challenge due to sediment heterogeneity and the lacking of geochemical background or baseline levels. In this study, a procedure was proposed to determine the average P background level and P geochemical baseline level (GBL) and develop P geochemical baseline functions (GBF) for riverbed sediments of the Liao River Watershed (LRW). The LRW has two river systems - the Liao River System (LRS) and the Daliao River System (DRS). Eighty-eight samples were collected and analyzed for P, Al, Fe, Ca, organic matter, pH, and texture. The results show that Fe can be used as a better particle-size proxy to construct the GBF of P (P (mg/kg) = 39.98 + 166.19 × Fe (%), R(2) = 0.835, n = 66). The GBL of P was 675 mg/kg, while the average background level of P was 355 mg/kg. Noting that many large cities are located in the DRS watershed, most of the contaminated sites were located within the DRS and the riverbed sediments were more contaminated by P in the DRS watershed than in the LRS watershed. The geochemical background and baseline information of P are of great importance in managing P levels within the LRW. Copyright © 2013 Elsevier Ltd. All rights reserved.

Real-time monitoring of subsurface microbial metabolism with graphite electrodes

DOE PAGES

Wardman, Colin; Nevin, Kelly P.; Lovley, Derek R.

2014-11-21

Monitoring in situ microbial activity in anoxic submerged soils and aquatic sediments can be labor intensive and technically difficult, especially in dynamic environments in which a record of changes in microbial activity over time is desired. Microbial fuel cell concepts have previously been adapted to detect changes in the availability of relatively high concentrations of organic compounds in waste water but, in most soils and sediments, rates of microbial activity are not linked to the concentrations of labile substrates, but rather to the turnover rates of the substrate pools with steady state concentrations in the nM-μ M range. In ordermore » to determine whether levels of current produced at a graphite anode would correspond to the rates of microbial metabolism in anoxic sediments, small graphite anodes were inserted in sediment cores and connected to graphite brush cathodes in the overlying water. Currents produced were compared with the rates of [2- 14C]-acetate metabolism. There was a direct correlation between current production and the rate that [2- 14C]-acetate was metabolized to 14CO 2 and 14CH 4 in sediments in which Fe(III) reduction, sulfate reduction, or methane production was the predominant terminal electron-accepting process. At comparable acetate turnover rates, currents were higher in the sediments in which sulfate-reduction or Fe(III) reduction predominated than in methanogenic sediments. This was attributed to reduced products (Fe(II), sulfide) produced at distance from the anode contributing to current production in addition to the current that was produced from microbial oxidation of organic substrates with electron transfer to the anode surface in all three sediment types. In conclusion, the results demonstrate that inexpensive graphite electrodes may provide a simple strategy for real-time monitoring of microbial activity in a diversity of anoxic soils and sediments.« less

Magnetotelluric Data, San Luis Valley, Colorado

USGS Publications Warehouse

Rodriguez, Brian D.; Williams, Jackie M.

2008-01-01

The San Luis Valley region population is growing. Water shortfalls could have serious consequences. Future growth and land management in the region depend on accurate assessment and protection of the region?s ground-water resources. An important issue in managing the ground-water resources is a better understanding of the hydrogeology of the Santa Fe Group and the nature of the sedimentary deposits that fill the Rio Grande rift, which contain the principal ground-water aquifers. The shallow unconfined aquifer and the deeper confined Santa Fe Group aquifer in the San Luis Basin are the main sources of municipal water for the region. The U.S. Geological Survey (USGS) is conducting a series of multidisciplinary studies of the San Luis Basin located in southern Colorado. Detailed geologic mapping, high-resolution airborne magnetic surveys, gravity surveys, an electromagnetic survey (called magnetotellurics, or MT), and hydrologic and lithologic data are being used to better understand the aquifers. The MT survey primary goal is to map changes in electrical resistivity with depth that are related to differences in rock types. These various rock types help control the properties of aquifers. This report does not include any data interpretation. Its purpose is to release the MT data acquired at 24 stations. Two of the stations were collected near Santa Fe, New Mexico, near deep wildcat wells. Well logs from those wells will help tie future interpretations of this data with geologic units from the Santa Fe Group sediments to Precambrian basement.

The lacustrine carbon cycle as illuminated by the waters and sediments of two hydrologically distinct headwater lakes in North-Central Minnesota, U.S.A

USGS Publications Warehouse

Dean, W.E.; Schwalb, A.

2002-01-01

The accumulation rates of CaCO3 and organic carbon (OC) in lake sediments are delicately balanced between production in the epilimnion and destruction in the hypolimnion. The cycling of these two forms of carbon makes a "carbon pump" that greatly affects the biogeochemical cycles of other elements. To further understand these biogeochemical dynamics, the lakes, streams, and wetlands of the Shingobee River headwater area of north-central Minnesota have been subjected to intensive hydrologic and biogeochemical studies. Williams Lake, situated close to the highest point in the regional flow system, is hydrologically closed, with no surface inlet or outlet, and ground water and precipitation as the only sources of water. Shingobee Lake, situated at the lowest point in the regional flow system, has the Shingobee River as an inlet and outlet. The surface waters of both lakes are oversaturated, and the bottom waters undersaturated, with respect to CaCO3 during the summer. The small amount of CaCO3 that is precipitated in the epilimnion of Williams Lake during the summer is dissolved in the undersaturated hypolimnion and sediments with the result that no CaCO3 is incorporated into the profundal surface sediments. Because of the high phytoplankton productivity of Shingobee Lake, sufficient CaCO3 is produced in the epilimnion that large amounts survive the corrosive hypolimnion and sediments, and an average of 46 wt. % accumulates in surface sediments. Another consequence of higher phytoplankton productivity in Shingobee Lake is that the hypolimnion becomes oxygen deficient within a month after overturn in both the spring and fall. Because of reducing conditions that develop in the hypolimnion of Shingobee Lake, high concentrations of dissolved Fe and Mn accumulate there during summer stratification. Precipitation of Fe and Mn oxyhydroxides during periods of fall and spring overturn results in high concentrations of Fe and Mn in surface sediments. In Williams Lake, high concentrations of Fe and Mn do not build up in the hypolimnion. The concentration of CaCO3 is about 80 wt. % in lower Holocene sediments of both lakes. The lower Holocene sediments in both lakes also contain high concentrations of Fe and Mn, and the lower Holocene sediments of Shingobee are laminated. The waters of both lakes had identical values of ??13C and ??18O during the early Holocene, but the waters of Williams Lake "evolved" during the early Holocene, increasing about 10??? in both ??13C and ??18O. Deposits of lacustrine marl occur as much as seven meters above the present elevation of Williams Lake, the highest of the two lakes. Taken together, these observations suggest that the lakes were once connected to form a larger lake called Lake Willobee with a hypolimnion that was anoxic, at least seasonally.

Environmental evaluations for deepening of Richmond Harbor and Santa Fe Channels

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

Brown, B.; Kohn, N.P.; Crecelius, E.A.

Richland, California is an important commercial port in San Francisco Bay. The San Francisco District of the US Army Corps of Engineers (USACE) plans to increase the depth of Richmond Harbor and Santa Fe Channels to -38 feet Mean Lower Low Water (MLLW) to accommodate deep-draft commercial vessels. The total volume of dredged material is expected to be approximately 1.4 million cubic yards. The options for disposal of the dredged material are aquatic disposal and upland disposal. The purpose of this study was to develop a database on chemical compounds in the dredged material to assist with determination of disposalmore » methods and the need for additional testing. This purpose was accomplished through an extensive field sampling program followed by chemical analysis of samples. Field sampling involved collection of core samples from Sante Fe and Richmond Harbor Channels. Cores were shipped to Battelle/Marine Sciences Laboratory, where they were subsampled for chemical analysis and/or archived by freezing. All sediment and water samples were analyzed for priority pollutants, including metals, organotins, base/neutral semivolatile organic compounds, chlorinated pesticides and PCBs, herbicide acids, and acidic phenols. Sediment samples were also analyzed for oil and grease and total organic carbon. Organophosphorus pesticides and dioxins and furans were measured in selected sediment samples from Richland Harbor Channel and from both sediment and water samples from Santa Fe Channel. 21 refs., 10 figs., 60 tabs.« less

Enhancing the Process of Anaerobic Ammonium Oxidation Coupled to Iron Reduction in Constructed Wetland Mesocosms with Supplementation of Ferric Iron Hydroxides

NASA Astrophysics Data System (ADS)

Shuai, W.; Jaffe, P. R.

2017-12-01

Effective ammonium (NH4+) removal has been a challenge in wastewater treatment processes. Aeration, which is required for the conventional NH4+ removal approach by ammonium oxidizing bacteria, is an energy intensive process during the operation of wastewater treatment plant. The efficiency of NH4+ oxidation in natural systems is also limited by oxygen transfer in water and sediments. The objective of this study is to enhance NH4+ removal by applying a novel microbial process, anaerobic NH4+ oxidation coupled to iron (Fe) reduction (also known as Feammox), in constructed wetlands (CW). Our studies have shown that an Acidimicrobiaceae bacterium named A6 can carry out the Feammox process using ferric Fe (Fe(III)) minerals like ferrihydrite as their electron acceptor. To investigate the properties of the Feammox process in CW as well as the influence of electrodes, Feammox bacterium A6 was inoculated in planted CW mesocosms with electrodes installed at multiple depths. CW mesocosms were operated using high NH4+ nutrient solution as inflow under high or low sediment Fe(III) level. During the operation, NH4+ and ferrous Fe concentration, pore water pH, voltages between electrodes, oxidation reduction potential and dissolved oxygen were measured. At the end of the experiment, CW sediment samples at different depths were taken, DNAs were extracted and quantitative polymerase chain reaction and pyrosequencing were performed to analyze the microbial communities. The results show that the high Fe level CW mesocosm has much higher NH4+ removal ability than the low Fe level CW mesocosm after Fe-reducing conditions are developed. This indicates the enhanced NH4+ removal can be attributed to elevated Feammox activity in high Fe level CW mesocosm. The microbial community structures are different in high or low Fe level CW mesocosms and on or away from the installed electrodes. The voltages between cathode and anode increased after the injection of A6 enrichment culture in low Fe level CW mesocosm but remained stable in high Fe level CW mesocosm, indicating A6 may use electrodes as their electron acceptor in the scarcity of Fe(III). The application of Feammox process in Fe-rich CW is promising in providing a cost and energy effective NH4+ removal approach, and the electrogenesis of A6 may also be useful in enhancing the Feammox process.

A twisted tale - how biocorrosion communities yield new insight on the distribution of marine iron-oxidizing bacteria

NASA Astrophysics Data System (ADS)

McBeth, J. M.; Emerson, D.

2011-12-01

Microbiologically influenced corrosion (MIC) of mild steel is a complex process involving biogeochemical interactions between bacteria, steel surfaces, and biogenic and abiotically produced minerals. The role of neutrophilic iron-oxidizing bacteria (FeOB) in this process is poorly understood, and surprisingly, little is known about the microbial ecology of corroding steel in marine environments. Based on previous work (McBeth et al 2011), we hypothesized that coastal sediments act as reservoirs for marine FeOB of the candidatus class 'Zetaproteobacteria', and that these bacteria will colonize and become numerically abundant on steel surfaces. To test this, mild steel coupons were incubated in a salt marsh and sampled over 40 days in summer 2010. DNA extracted from the steel surfaces was analyzed for overall bacterial diversity by pyrosequencing of the V4 variable region of the 16S rRNA gene, and relevant communities were quantified using qPCR. The qPCR analyses were done using 16S primers specific to prokaryotes (Takai & Horikoshi 2000) and Zetaproteobacteria (Kato et al 2009), and a dsrA gene specific primer (Ben-Dov et al 2007) to assess the population of sulfate-reducing bacteria (SRB). Pyrosequencing data analyses showed Zetaproteobacteria were present on steel samples throughout the incubations and were also present in adjacent sediments; however, the diversity of Zetaproteobacteria was lower on the steel in comparison with sediments, indicating specific populations were enriched on the steel coupons. Iron oxyhydroxide stalk biosignatures were observed on the steel and in enrichment cultures, evidence that the Zetaproteobacteria identified using molecular techniques were likely FeOB. Relatives of the H2-oxidizing genus Hydrogenophaga and members of the family Rhodobacterales were also identified as important members of the biocorrosion community and were present both on steel and in sediments. The diversity of these organisms on steel surfaces increased with incubation time. The populations assessed with qPCR remained fairly constant in the sediments during the course of the study. The number of Zetaproteobacteria in the sediments was approximately 10 fold lower than the SRB numbers. In contrast, the proportion of Zetaproteobacteria present on the steel increased rapidly over the first 10 days, exceeding the copy numbers present in the sediment by an order of magnitude. The SRB numbers on the steel were 10 fold lower than in sediments during the first days of incubation, but increased with time to near the sediment numbers of SRB at 40 days. The proportion of SRB in sediments was relatively high and constant. This work illustrates that coastal sediments may be a hitherto unrecognized reservoir for Zetaproteobacteria who, though numerically low in the sediment, can quickly colonize environments where free Fe(II) is abundant.

Temporal shifts in reef lagoon sediment composition, Discovery Bay, Jamaica

NASA Astrophysics Data System (ADS)

Perry, Christopher T.; Taylor, Kevin G.; Machent, Philip G.

2006-03-01

Discovery Bay, north Jamaica, forms a large (1.5 km wide), deep (up to 56 m) embayment that acts as a sink for reef-derived and lagoonal carbonate sediments. Since the mid-1960s, the bay has also provided a sink for inputs of bauxite sediment that are spilled during loading at a boat terminal constructed within Discovery Bay. Bauxite has accumulated across much of the southern section of the bay with surficial sediments presently composed of up to 35 weight% non-carbonate. Cores recovered from sites on the western side of the bay provide a stratigraphic record of this history of bauxite contamination across water depths from 5 to 25 m. The bauxite-influenced upper sediment horizons are clearly visible in each core from the distinctive red-brown colouration of the sediment. These sediments are composed of approximately 10% non-carbonate (bauxite) and have Fe contents of around 2-3000 μg/g (up to 7000 μg/g). The thickness of this upper bauxite-contaminated sequence increases down transect (approximately 18 cm in the shallowest core, to around 47 cm in the deepest core), and in each core overlies a sequence of 'clean' lagoon carbonates. These typically are poorly sorted carbonate sands with variable amounts of coral rubble. Down-core data on CaCO 3 and Fe content provide a chemical record of decreasing sediment contamination with depth, with the lower 'clean' carbonates composed of only around 2% non-carbonate and <700 μg/g Fe. Down-core sediment-constituent data also indicate significant changes in sediment production at the shallowest sites. At depths of 5 and 10 m, sediment assemblages have shifted from diverse assemblages of coral, mollusc, Amphiroa and Halimeda in the clean lagoon sands, to assemblages dominated by Halimeda and Amphiroa within the surficial sediments. At the deeper sites, no major down-core shifts in sediment constituents occur. These sites thus record a rather complex history of changes in sediment composition and chemistry. Clear shifts in chemistry and stratigraphy occur in all the cores and reflect progressive bauxite contamination in the near-surface horizons. These inputs, however, do not appear to have directly affected carbonate production, since the major constituent changes appear to be a response to more regional declines in coral community and reef status.

The cosmic native iron in Upper Jurassic to Miocene deep-sea deposits of the western North Atlantic

NASA Astrophysics Data System (ADS)

Murdmaa, Ivar; Pechersky, Diamar; Nurgaliev, Danis; Gilmanova, Di; Sloistov, Sergey

2014-05-01

Thermomagnetic analysis of 335 rock samples from DSDP sites 386, 387 (Leg 43) and 391 A, C (Leg 44) drilled in the western North Atlantic revealed distribution patterns of native Fe particles in Upper Jurassic to Miocene deep-sea deposits. Native iron occurs in deep-sea rocks as individual particles from tens of nm to 100 µm in size. The native Fe is identified throughout the sections recovered. Its concentration ranges from nx10-6% to 5x10-3%, but zero values persist to occur in each lithostratigraphic unit studied. The bimodal distribution of the native iron concentration with a zero mode is typical for the cosmic dust in sedimentary rocks, because of its slow flux to the Earth surface, as compared to sedimentation fluxes. Ni admixture in native Fe also demonstrates bimodal distribution with the zero mode (pure Fe) and a mode 5 - 6% that corresponds to average Ni content in the cosmic dust and meteorites. Concentration of native Fe does not depend on rock types and geological age. Relatively high mean native Fe concentrations (less zero values) occur in Lower Cretaceous laminated limestones (sites 387, 391) interpreted as contourites and in Oligocene volcaniclastic turbidites of the Bermuda Rise foot (Site 386), whereas minimum values are measured in Miocene mass flow deposits (Site 391). We suggest that concentration of native Fe increases in deposits of pulsating sedimentation (turbidites, laminated contourites) due to numerous short hiatuses and slow sedimentation events in between instantaneous turbidite or contourite deposition pulses. Extreme values possibly indicate cosmic dust flux anomalies. The study was partially supported by RFBR, research project No. 14-05-00744a.

Rapid anaerobic benzene oxidation with a variety of chelated Fe(III) forms

USGS Publications Warehouse

Lovley, D.R.; Woodward, J.C.; Chapelle, F.H.

1996-01-01

Fe(III) chelated to such compounds as EDTA, N-methyliminodiacetie acid, ethanol diglycine, humic acids, and phosphates stimulated benzene oxidation coupled to Fe(III) reduction in anaerobic sediments from a petroleum- contaminated aquifer as effectively as or more effectively than nitrilotriacetic acid did in a previously demonstrated stimulation experiment. These results indicate that many forms of chelated Fe(III) might be applicable to aquifer remediation.

Phosphorus dynamics in and below the redoxcline in the Black Sea and implications for phosphorus burial

NASA Astrophysics Data System (ADS)

Dijkstra, N.; Kraal, P.; Séguret, M. J. M.; Flores, M. R.; Gonzalez, S.; Rijkenberg, M. J. A.; Slomp, C. P.

2018-02-01

Marine basins with oxygen-depleted deep waters provide a natural laboratory to investigate the consequences of anoxic and sulfidic (i.e. euxinic) conditions for biogeochemical processes in seawater and sediments. In this study, we investigate the dynamics of the key nutrient phosphorus (P) and associated elements such as manganese (Mn), iron (Fe) and calcium (Ca) in the euxinic deep basin of the Black Sea. By examining water column particles with scanning electron microscope - energy dispersive spectroscopy and synchrotron-based X-ray absorption spectroscopy, we show that Mn(III/IV)-P is the key form of particulate P in the redoxcline. Other forms of particulate P include organic P, Fe(III)-P, and inorganic polyphosphates. Most inorganic P particles that are formed in the redoxcline subsequently dissolve in the underlying sulfidic waters, with the exception of some particulate Fe(III)-P that accounts for <1% of all P settling onto the seafloor. Organic P is the dominant source of P to the sediment. Most of this organic P is degraded in the upper 2 cm of the sediment. Results of sequential extractions and a 33P radiotracer experiment point towards the formation of labile Ca-P and P adsorbed onto calcium-carbonate and clays and a role of these phases as a major sink of P in the sediment. The total P burial efficiency in the sediments is ∼27%, which is relatively high when compared to estimates for sediments in other euxinic basins such as the Baltic Sea (<12%). We suggest that the abundant presence of calcium carbonate may contribute to the more efficient sequestration of P in Black Sea sediments.

Effect of Oxalic Acid Treatment on Sediment Arsenic Concentrations and Lability under Reducing Conditions

PubMed Central

Sun, Jing; Bostick, Benjamin C.; Mailloux, Brian J.; Ross, James M.; Chillrud, Steven N.

2016-01-01

Oxalic acid enhances arsenic (As) mobilization by dissolving As host minerals and competing for sorption sites. Oxalic acid amendments thus could potentially improve the efficiency of widely used pump-and-treat (P&T) remediation. This study investigates the effectiveness of oxalic acid on As mobilization from contaminated sediments with different As input sources and redox conditions, and examines whether residual sediment As after oxalic acid treatment can still be reductively mobilized. Batch extraction, column, and microcosm experiments were performed in the laboratory using sediments from the Dover Municipal Landfill and the Vineland Chemical Company Superfund sites. Oxalic acid mobilized As from both Dover and Vineland sediments, although the efficiency rates were different. The residual As in both Dover and Vineland sediments after oxalic acid treatment was less vulnerable to microbial reduction than before the treatment. Oxalic acid could thus improve the efficiency of P&T. X-ray absorption spectroscopy analysis indicated that the Vineland sediment samples still contained reactive Fe(III) minerals after oxalic acid treatment, and thus released more As into solution under reducing conditions than the Dover samples. Therefore, the efficacy of P&T must consider sediment Fe mineralogy when evaluating its overall potential for remediating groundwater As. PMID:26970042

Photolytic Release of Dissolved Vanadium and Copper from Resuspended Coastal Marine Sediments

NASA Astrophysics Data System (ADS)

Skrabal, S. A.; Hammaker, S. N.; McBurney, A. W.; Avery, G. B., Jr.; Kieber, R. J.; Mead, R. N.

2016-02-01

Sunlight photolysis engenders release of dissolved vanadium (V), copper (Cu), and dissolved organic carbon (DOC) from a wide variety of resuspendable coastal marine sediments. Net photoreleases after 6 h of simulated sunlight were as high as 12 nM for Cu and as high as 15 nM for V. Release of Cu significantly correlated with sediment Cu. Photoreleased Cu (but not V) correlated with sediment Fe content, suggesting that photoreduction of Fe oxide carrier phases may be an important photoproduction mechanism for Cu. Longer term experiments showed continued release of metals that were not immediately readsorbed back onto sediments after 24 h of irradiation suggesting that photoproduced metals persist in the dissolved phase and are not immediately scavenged onto particles. Experiments utilizing differing total suspended sediment (TSS) levels show that, although higher TSS causes more photoproduction of Cu and V, the amount produced per mass of sediment is greatest at the lowest TSS. Vanadium photoproduction increased in Macondo oil-amended sediments compared to controls after a one-month incubation period suggesting that the oil may be a source of this metal to the water column. These results imply that photoproduction is an unrecognized source of the micronutrient metals Cu and V to coastal waters.

Assessment of acid leachable trace metals in sediment cores from River Uppanar, Cuddalore, Southeast coast of India.

PubMed

Ayyamperumal, T; Jonathan, M P; Srinivasalu, S; Armstrong-Altrin, J S; Ram-Mohan, V

2006-09-01

An acid leachable technique is employed in core samples (C1, C2 and C3) to develop a baseline data on the sediment quality for trace metals of River Uppanar, Cuddalore, southeast coast of India. Acid leachable metals (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn and Cd) indicate peak values at the sulphidic phase and enrichment of metals in the surface layers are due to the anthropogenic activities. Association of trace metals with Fe, Mn indicates their adsorption onto Fe-Mn oxyhydroxides and their correlation with S indicate that they are precipitated as metal sulphides. Factor analysis identified three possible types of geochemical associations and the supremacy of trace metals along with Fe, Mn, S and mud supports their geochemical associations. Factor analysis also signifies that anthropogenic activities have affected both the estuarine and fresh water regions of River Uppanar.

A great volcanic eruption around AD 1300 recorded in lacustrine sediment from Dongdao Island, South China Sea

NASA Astrophysics Data System (ADS)

Yang, Zhongkang; Long, Nanye; Wang, Yuhong; Zhou, Xin; Liu, Yi; Sun, Liguang

2017-02-01

The contents of Ti, Al and Fe 2 O 3 in a lacustrine sediment core (DY6) collected from Dongdao Island, South China Sea (SCS), were determined to be much higher than those in the three major sediment end-members (coral sand, guano and plants), and their likely sources include terrigenous dust and volcanic ash. At 61 cm (˜AD 1300), the contents of Ti, Al and Fe 2 O 3 have an abnormally high spike, which cannot be explained by terrigenous dust. The Sr and Nd isotope compositions at 61 cm are in excellent agreement with those in volcanic materials, but they are significantly different from those in terrigenous dust, implying a possible material input from historical volcanic eruptions in the lacustrine sediment DY6. The documented great Samalas volcanic eruption at AD 1257 in Indonesia is likely the candidate for this volcanic eruption.

Characterizing the Fate and Mobility of Phosphorus in Utah Lake Sediments

NASA Astrophysics Data System (ADS)

Randall, M.; Carling, G. T.; Nelson, S.; Bickmore, B.; Miller, T.

2016-12-01

An increasing number of lakes worldwide are impacted by eutrophication and harmful algal blooms due to nutrient inputs. Utah Lake, located in northern Utah, is a eutrophic freshwater lake that is unique because it is naturally shallow, turbid, and alkaline with high dissolved oxygen levels. Recently, the Utah Division of Water Quality has proposed a new rule to limit phosphorus (P) loading to Utah Lake from wastewater treatment plants in an effort to mitigate eutrophication. However, reducing external P loads may not lead to immediate improvements in water quality due to the legacy pool of nutrients in lake sediments. The purpose of this study is to characterize the fate and mobility of P in Utah Lake to better understand P cycling in this unique system. We analyzed P speciation, mineralogy, and binding capacity in lake sediment samples collected from 9 locations across Utah Lake. P concentrations in sediment ranged from 1120 to 1610 ppm, with highest concentrations in Provo Bay near the major metropolitan area. Likewise, P concentrations in sediment pore water were highest in Provo Bay with concentrations up to 4 mg/L. Sequential leach tests indicate that 30-45% of P is bound to apatite and another 40-55% is adsorbed onto the surface of redox sensitive Fe/Mn hydroxides. This was confirmed by SEM images, which showed the highest P concentrations correlating with both Ca (apatite) and Fe (Fe hydroxides). The apatite-bound P fraction is likely immobile, but the P fraction sorbed to Fe/Mn hydroxides is potentially bioavailable under changing redox conditions. Batch sorption results indicate that lake sediments have a high capacity to absorb and remove P from the water column, with an average uptake of 70-96% of P from spiked surface water with concentrations ranging from 1-10 mg/L. Mineral precipitation and sorption to bottom sediments is an efficient removal mechanism of P in Utah Lake, but a significant portion of P may be available for resuspension and cycling in surface waters. Mitigating lake eutrophication is a complex problem that goes beyond reducing nutrient loads to the water body and requires a better understanding of internal P cycling.

Source and distribution of naturally occurring arsenic in groundwater from Alberta’s Southern Oil Sands Regions

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

Moncur, Michael C.; Paktunc, Dogan; Jean Birks, S.

Arsenic (As) concentrations as high as 179 μg/L have been observed in shallow groundwater in the Alberta’s Southern Oil Sand Regions. The geology of this area of Alberta includes a thick cover (up to 200 m) of unconsolidated glacial deposits, with a number of regional interglacial sand and gravel aquifers, underlain by marine shale. Arsenic concentrations observed in 216 unconsolidated sediment samples ranged from 1 and 17 ppm. A survey of over 800 water wells sampled for As in the area found that 50% of the wells contained As concentrations exceeding drinking water guidelines of 10 μg/L. Higher As concentrationsmore » in groundwater were associated with reducing conditions. Measurements of As speciation from 175 groundwater samples indicate that As(III) was the dominant species in 74% of the wells. Speciation model calculations showed that the majority of groundwater samples were undersaturated with respect to ferrihydrite, suggesting that reductive dissolution of Fe-oxyhydroxides may be the source of some As in groundwater. Detailed mineralogical characterization of sediment samples collected from two formations revealed the presence of fresh framboidal pyrite in the deeper unoxidized sediments. Electron microprobe analysis employing wavelength dispersive spectrometry indicated that the framboidal pyrite had variable As content with an average As concentration of 530 ppm, reaching up to 1840 ppm. In contrast, the oxidized sediments did not contain framboidal pyrite, but exhibited spheroidal Fe-oxyhydroxide grains with elevated As concentrations. The habit and composition suggest that these Fe-oxyhydroxide grains in the oxidized sediment were an alteration product of former framboidal pyrite grains. X-ray absorption near edge spectroscopy (XANES) indicated that the oxidized sediments are dominated by As(V) species having spectral features similar to those of goethite or ferrihydrite with adsorbed As, suggesting that Fe-oxyhydroxides are the dominant As carriers. XANES spectra collected on unoxidized sediment samples, in contrast, indicated the presence of a reduced As species (As(-I)) characteristic of arsenopyrite and arsenian pyrite. The results of the mineralogical analyses indicate that the oxidation of framboidal pyrite during weathering may be the source of As released to shallow aquifers in this region.« less

Effect of adsorbed metals ions on the transport of Zn- and Ni-EDTA complexes in a sand and gravel aquifer

USGS Publications Warehouse

Kent, D.B.; Davis, J.A.; Anderson, L.C.D.; Rea, B.A.; Coston, J.A.

2002-01-01

Adsorption, complexation, and dissolution reactions strongly influenced the transport of metal ions complexed with ethylenediaminetetraacetic acid (EDTA) in a predominantly quartz-sand aquifer during two tracer tests conducted under mildly reducing conditions at pH 5.8 to 6.1. In tracer test M89, EDTA complexes of zinc (Zn) and nickel (Ni), along with excess free EDTA, were injected such that the lower portion of the tracer cloud traveled through a region with adsorbed manganese (Mn) and the upper portion of the tracer cloud traveled through a region with adsorbed Zn. In tracer test S89, Ni- and Zn-EDTA complexes, along with excess EDTA complexed with calcium (Ca), were injected into a region with adsorbed Mn. The only discernable chemical reaction between Ni-EDTA and the sediments was a small degree of reversible adsorption leading to minor retardation. In the absence of adsorbed Zn, the injected Zn was displaced from EDTA complexes by iron(III) [Fe(III)] dissolved from the sediments. Displacement of Zn by Fe(III) on EDTA became increasingly thermodynamically favorable with decreasing total EDTA concentration. The reaction was slow compared to the time-scale of transport. Free EDTA rapidly dissolved aluminum (Al) from the sediments, which was subsequently displaced slowly by Fe. In the portion of tracer cloud M89 that traveled through the region contaminated with adsorbed Zn, little displacement of Zn complexed with EDTA was observed, and Al was rapidly displaced from EDTA by Zn desorbed from the sediments, in agreement with equilibrium calculations. In tracer test S89, desorption of Mn dominated over the more thermodynamically favorable dissolution of Al oxyhydroxides. Comparison with results from M89 suggests that dissolution of Al oxyhydroxides in coatings on these sediment grains by Ca-EDTA was rate-limited whereas that by free EDTA reached equilibrium on the time-scale of transport. Rates of desorption are much faster than rates of dissolution of Fe oxyhydroxides from sediment-grain surfaces and, therefore, adsorbed metal ions can strongly influence the speciation of ligands like EDTA in soils and sediments, especially over small temporal and spatial scales. Copyright ?? 2002 Elsevier Science Ltd.

Effects of inorganic electron acceptors on methanogenesis and methanotrophy and on the community structure of bacteria and archaea in sediments of a boreal lake

NASA Astrophysics Data System (ADS)

Rissanen, Antti J.; Karvinen, Anu; Nykänen, Hannu; Peura, Sari; Tiirola, Marja; Mäki, Anita; Kankaala, Paula

2016-04-01

Lake sediments are globally significant sources of CH4 to the atmosphere, but the factors controlling the production and consumption of CH4 in these systems are understudied. Increasing availability of electron acceptors (EA) (other than CO2) in sediments can decrease or even suppress CH4 production by diverting the electron flow (from H2 and organic substances) from methanogenic to other anaerobic respiration pathways. However, whether these changes in microbial function extend down to changes in the structure of microbial communities is not known. Also anaerobic oxidation of methane (AOM) could be enhanced by increased availability of EAs (SO42-, NO3-, Fe3+ and Mn4+), but information on the role of this process in lake sediments is scarce. We studied the effects of inorganic EAs on the potential for CH4 production and consumption and on the structure of microbial communities in sediments of a boreal lake. Anoxic slurries of sediment samples collected from two depths (0 - 10 cm; 10 - 30 cm) of the profundal zone of a boreal, mesotrophic Lake Ätäskö, were amended with 1) CH4 or with CH4 and either 2) 10 mM Mn4+, 3) 10 mM Fe3+, 4) O2 or 5) CH2F2 (inhibitor of aerobic methane oxidation) and incubated at +10° C for up to 4 months. Furthermore, slurries from the 10 - 30 cm layer were amended with CH4 and either 6) 2 mM NO3- or 7) 2 mM SO42- and incubated at +4 ° C for up to 14 months. The processes were measured using 13C-labelling and by concentration measurements of CH4 and CO2. Effects of treatments 1-3 on microbial communities were also analysed by next-generation sequencing of 16S rRNA, as well as methyl coenzyme-M reductase gene amplicons and mRNA transcripts. CH4 production (max. 83 nmol gdw-1d-1) took place in the anaerobic treatments but was generally decreased by the addition of NO3-, SO42-, Fe3+ and Mn4+. Although the structure of sediment archaeal community was resistant to Fe3+/Mn4+ - additions, slight changes in the structure of bacterial community occurred. Besides decreasing the availability of methanogenic substrates, the Mn4+/Fe3+ - induced changes in the bacterial community also probably decreased the H2:acetate - ratio in the substrate pool. This led to increase in the relative activity (mRNA level) of some operational taxonomic units assigned to aceticlastic Methanosaetaceae and decrease in the relative activity of hydrogenotrophic Methanoregulaceae in the sediment. CH4 oxidation (0.02 - 0.30 nmol gdw-1d-1 in anaerobic and 18 - 73 nmol gdw-1d-1in aerobic treatments) took place without EA additions and was enhanced only by O2. This suggests decoupling of the process from the reduction of other inorganic EAs. The results also indicate that Fe3+/Mn4+ - reduction did not increase CH4 oxidation via increased availability of SO42- by cryptic sulfur cycle or via increased availability of organic EAs. Furthermore, ANME - archaea were only ≤ 3% of sediment archaeal community and their relative activity was decreased during incubations. Thus, EA driving CH4 oxidation in the anoxic sediments of the lake remains unknown or the process was methanogen-driven via trace methane oxidation.

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

Chen, Chunmei; Kukkadapu, Ravi K.; Lazareva, Olesya

Properties of Fe minerals are poorly understood in natural soils and sediments with variable redox conditions. In this study, we combined 57Fe Mössbauer and Fe K-edge X-ray absorption spectroscopic techniques to assess solid-phase Fe speciation along the vertical redox gradients of floodplain profiles, which exhibited a succession of oxic, anoxic and suboxic-oxic zones with increasing depth along the vertical profiles. The anoxic conditions at the intermediate horizon (55-80 cm) of the eastern floodplain resulted in extensive depletion of Fe(III)-oxides including both ferrihydrite and goethite, concurrent with a corresponding reduction of phyllosilicates(PS)-Fe(III) to PS-Fe(II). In addition, the anoxic conditions increased themore » crystallinity of Fe(III)-oxides in this reduced zone, relative to the oxic zones. In the most reduced intermediate sediments at 80-120cm of the western floodplain, the anoxic conditions drove the complete reductive dissolution of Fe(III) oxides, as well as the greatest reduction (48-55%) in PS-Fe(III). In both oxic near-surface horizon and oxic-suboxic gravel aquifers beneath the soil horizons, Fe(III)-oxides were mainly present as ferrihydrite with a less amount of goethite, which preferentially occurred as nanogoethite or Al/Si-substituted goethite. Ferrihydrite with varying crystallinity or impurities such as organic matter, Al or Si, persisted under suboxic-oxic conditions in the floodplain. This study indicates that vertical redox gradients exert a major control on the quantity and speciation of Fe(III) oxides as well as the oxidation state of structural Fe in PS, which could significantly affect nutrient cycling and carbon (de)stabilization.« less

Sediment heavy metals and benthic diversities in Hun-Tai River, northeast of China.

PubMed

Qu, Xiaodong; Ren, Ze; Zhang, Min; Liu, Xiaobo; Peng, Wenqi

2017-04-01

In aquatic ecosystems, metal contamination in sediments has become a ubiquitous environmental problem, causing serious issues. Hun-Tai River, located in northeast of China, flows through an important heavy industry region and metropolitan area. This study examined the heavy metals (Cd, Cr, Cu, Fe, Mn, Pb, Ni, and Zn) of sediments and diversities (taxa richness, Shannon diversity, and evenness) of benthic assemblages (benthic algae and macroinvertebrate) in Hun-Tai River. The results clearly described the spatial patterns of metal contamination in terms of geo-accumulation index and contamination factor, as well as the spatial patterns of benthic diversities in terms of taxa richness, Shannon index, and evenness by kriging interpolation. The sediments were largely contaminated by Cd, followed by Cu, Fe, Zn, Mn, and Ni. Cd and Zn had similar spatial patterns and similar sources. Cu, Fe, Mn, and Ni showed similar spatial patterns and similar sources. The surface sediments were unpolluted by Cr and Pb. The metal mines and the heavy industry in the major cities were the potential pollution sources. Benthic algae and macroinvertebrate responded similarly to the heterogeneous environment and metal contamination, with high taxa richness and Shannon index in middle-upper reaches of Hun-Tai River. Evenness showed complex spatial patterns. Under low contamination, both taxa richness, Shannon diversity, and evenness had a large variation range. However, under the moderate and high contamination, the taxa richness and Shannon diversity kept to a low level but the evenness had a high level. This study provided insights into the sediment heavy metal contamination in Hun-Tai River.

Assessment of heavy metals in sediment of Aguamilpa Dam, Mexico.

PubMed

Rangel-Peraza, Jesús Gabriel; de Anda, José; González-Farías, Fernando A; Rode, Michael; Sanhouse-García, Antonio; Bustos-Terrones, Yaneth A

2015-03-01

The Aguamilpa Dam is part of the reservoir cascade system formed by four reservoirs in the middle and lower part of the Santiago River. For decades, this system has received urban and industrial wastewater from the metropolitan area of Guadalajara and the runoff of agricultural fields located in the river basin. The present study was carried out to obtain a preliminary assessment on the concentration distribution of heavy metals (Al, Ba, Cd, Cr, Cu, Fe, Hg, Mg, Ni, Pb, and Zn) in surface sediments of the Aguamilpa reservoir collected from 10 sampling stations. The metal concentrations (mg kg(-1)) in the sampling stations ranged as follows: Al, 27,600-7760; Ba, 190.0-15.9; Cd, 0.27-0.02; Cr, 18.30-0.22; Cu, 60.80-0.79; Fe, 15,900-4740; Hg, 0.04-0.01; Mg, 7590-8.05; Ni, 189.00-0.24; Pb, 13.6-1.64; and Zn, 51.8-14.8. Significant spatial variation in concentrations was observed for Al, Fe, and Pb. Sediment pollution was evaluated using the enrichment factor, the geo-accumulation index, the pollution load index, and sediment quality guidelines. Based on geo-accumulation and pollution load indexes, Aguamilpa sediments were found, in some sampling stations, as unpolluted to moderately polluted with Ni, Cd, Cu, and Mg. Enrichment factors showed that Cd is highly related to agricultural activities that take place in the surrounding areas of the Aguamilpa reservoir. Despite these results, none of the heavy metals evaluated exceeded international concentrations limits, indicating that the Aguamilpa reservoir surface sediments are not contaminated.

An integrated bioremediation process for petroleum hydrocarbons removal and odor mitigation from contaminated marine sediment.

PubMed

Zhang, Zhen; Lo, Irene M C; Yan, Dickson Y S

2015-10-15

This study developed a novel integrated bioremediation process for the removal of petroleum hydrocarbons and the mitigation of odor induced by reduced sulfur from contaminated marine sediment. The bioremediation process consisted of two phases. In Phase I, acetate was dosed into the sediment as co-substrate to facilitate the sulfate reduction process. Meanwhile, akaganeite (β-FeOOH) was dosed in the surface layer of the sediment to prevent S(2-) release into the overlying seawater. In Phase II, NO3(-) was injected into the sediment as an electron acceptor to facilitate the denitrification process. After 20 weeks of treatment, the sequential integration of the sulfate reduction and denitrification processes led to effective biodegradation of total petroleum hydrocarbons (TPH), in which about 72% of TPH was removed. In Phase I, the release of S(2-) was effectively controlled by the addition of akaganeite. The oxidation of S(2-) by Fe(3+) and the precipitation of S(2-) by Fe(2+) were the main mechanisms for S(2-) removal. In Phase II, the injection of NO3(-) completely inhibited the sulfate reduction process. Most of residual AVS and S(0) were removed within 4 weeks after NO3(-) injection. The 16S rRNA clone library-based analysis revealed a distinct shift of bacterial community structure in the sediment over different treatment phases. The clones affiliated with Desulfobacterales and Desulfuromonadales were the most abundant in Phase I, while the clones related to Thioalkalivibrio sulfidophilus, Thiohalomonas nitratireducens and Sulfurimonas denitrificans predominated in Phase II. Copyright © 2015 Elsevier Ltd. All rights reserved.

Provenance of fine-grained sediments in the inner shelf of the Korea Strait (South Sea), Korea

NASA Astrophysics Data System (ADS)

Um, In kwon; Choi, Man Sik; Bae, Sung Ho; Song, Yunho; Kong, Gee Soo

2017-12-01

Major metals (Al, Fe, Mg, and Ti), trace metals (Li, Cs, Sc, and Rb), and rare earth elements (REEs) in the fine-grained sediments (< 15 μm) of the central South Sea mud (CSSM) were analyzed to determine the sediment provenance. The spatial distribution of the analyzed elements showed a clear separation between the western (W-CSSM) and eastern (E-CSSM) regions of the CSSM. Concentrations of Fe, Ti, Mg, Sc, and REEs were higher in the WCSSM, whereas concentrations of Al, Cs, Li, and Rb were higher in the E-CSSM. Unlike the ratios of trace metals ((Cs+Sc)/Li and Rb/Li), REEs could not be used to track the provenance of fine-grained sediments because of a grain size effect. The mixing relationships of the provenance indicators showed that the fine-grained sediments of the CSSM comprise a mixture of the sediments discharged from the Seomjin River (SRS) and sediments eroded and transported from the Heuksan mud belt (HMBS) area by the Korean Coastal Current. Sediments originating from the HMB were deposited mostly in the W-CSSM, whereas those from the Seomjin River were deposited mostly in the E-CSSM. This study indicated that sediments from Chinese rivers as well as the Geum River are important even in the inner shelf of the South Sea of Korea.

Provenance of Fine-grained Sediments in the Inner Shelf of the Korea Strait (South Sea), Korea

NASA Astrophysics Data System (ADS)

Um, In kwon; Choi, Man Sik; Bae, Sung Ho; Song, Yunho; Kong, Gee Soo

2018-03-01

Major metals (Al, Fe, Mg, and Ti), trace metals (Li, Cs, Sc, and Rb), and rare earth elements (REEs) in the fine-grained sediments (< 15 μm) of the central South Sea mud (CSSM) were analyzed to determine the sediment provenance. The spatial distribution of the analyzed elements showed a clear separation between the western (W-CSSM) and eastern (E-CSSM) regions of the CSSM. Concentrations of Fe, Ti, Mg, Sc, and REEs were higher in the WCSSM, whereas concentrations of Al, Cs, Li, and Rb were higher in the E-CSSM. Unlike the ratios of trace metals ((Cs+Sc)/Li and Rb/Li), REEs could not be used to track the provenance of fine-grained sediments because of a grain size effect. The mixing relationships of the provenance indicators showed that the fine-grained sediments of the CSSM comprise a mixture of the sediments discharged from the Seomjin River (SRS) and sediments eroded and transported from the Heuksan mud belt (HMBS) area by the Korean Coastal Current. Sediments originating from the HMB were deposited mostly in the W-CSSM, whereas those from the Seomjin River were deposited mostly in the E-CSSM. This study indicated that sediments from Chinese rivers as well as the Geum River are important even in the inner shelf of the South Sea of Korea.

The distribution of phosphorus in Popes Creek, VA, and in the Pocomoke River, MD: Two watersheds with different land management practices in the Chesapeake Bay Basin

USGS Publications Warehouse

Simon, N.S.; Bricker, O.P.; Newell, W.; McCoy, J.; Morawe, R.

2005-01-01

This paper compares phosphorus (P) concentrations in sediments from two watersheds, one with, and one without, intensive animal agriculture. The watersheds are in the coastal plain of the Chesapeake Bay and have similar physiographic characteristics. Agriculture in the Pocomoke River, MD, watershed supplied 2.7 percent of all broiler chickens produced in the USA in 1997. Poultry litter is an abundant, local source of manure for crops. Broiler chickens are not produced in the Popes Creek, VA, watershed and poultry manure is, therefore, not a major source of fertilizer. The largest concentrations of P in sediment samples are found in floodplain and main-stem bottom sediment in both watersheds. Concentrations of total P and P extracted with 1N HCl are significantly larger in main-stem bottom sediments from the Pocomoke River than in main-stem bottom sediments from Popes Creek. Larger concentrations of P are associated with what are potentially redox sensitive iron oxyhydroxides in sediment samples from the Pocomoke River watershed than are associated with what are potentially redox sensitive iron oxyhydroxides in sediment samples from the Popes Creek watershed. Data for P and iron (Fe) concentrations in sediments from the Popes Creek watershed provide a numerical framework (baseline) with which to compare P and Fe concentrations in sediment from the Pocomoke River watershed. ?? Springer 2005.

Biostabilization of cadmium contaminated sediments using indigenous sulfate reducing bacteria: Efficiency and process.

PubMed

Peng, Weihua; Li, Xiaomin; Liu, Tong; Liu, Yingying; Ren, Jinqian; Liang, Dawei; Fan, Wenhong

2018-06-01

Sulfate reducing bacteria (SRB) was used to stabilize cadmium (Cd) in sediments spiked with Cd. The study found that the Cd in sediments (≤600 mg kg -1 ) was successfully stabilized after 166 d SRB bio-treatment. This was verified by directly and indirectly examining Cd speciation in sediments, mobilization index, and Cd content in interstitial water. After 166 d bio-treatment, compared with control groups, Cd concentrations in interstitial water of Cd-spiked sediments were reduced by 77.6-96.4%. The bioavailable fractions of Cd (e.g., exchangeable and carbonate bound phases) were reduced, while more stable fractions of Cd (e.g., Fe-Mn oxide, organic bound, and residual phases) were increased. However, Cd mobilization in sediment was observed during the first part of bio-treatment (32 d), leading to an increase of Cd concentrations in the overlying water. Bacterial community composition (e.g., richness, diversity, and typical SRB) played an important role in Cd mobilization, dissolution, and stabilization. Bacterial community richness and diversity, including the typical SRB (e.g., Desulfobacteraceae and Desulfobulbaceae), were enhanced. However, bacterial communities were also influenced by Cd content and its speciations (especially the exchangeable and carbonate bound phases) in sediments, as well as total organic carbon in overlying water. Copyright © 2018 Elsevier Ltd. All rights reserved.

Sedimentary Carbon, Sulfur, and Iron Relationships in Modern and Ancient Diagenetic Environments of the Eel River Basin (U.S.A.)

USGS Publications Warehouse

Sommerfield, C.K.; Aller, R.C.; Nittrouer, C.A.

2001-01-01

Depositional and diagenetic controls on the distributions of carbon, sulfur, and iron (C-S-Fe) in modern sediments and upper Pleistocene mudrocks of the Eel River Basin (ERB), northern California continental margin, were investigated using a combination of geochemical, radioisotopic, and sedimentological methods. A mass balance based on down-core profiles of porewater and solid-phase constituents and diagenetic modeling suggests that only 12-30% of the pyrite-S produced via SO4-2 reduction during burial is retained in modern shelf and upper slope deposits of the ERB. Bioturbational reoxidation of initially reduced S is inferred to be the major control on S preservation, on the basis of an observed inverse relationship between pyrite-S retention and biological mixing intensity, estimated from profiles of excess 234Th. Importantly, these findings argue that massive depositional episodes on the shelf following floods of the Eel River have a negligible long-term impact on bioturbating macrofauna and the potential to affect geochemical properties of the sediments. Down-core profiles of reactive Fe3+and Py-Fe(II) for the modern deposits suggest that highly reactive Fe phases are sulfidized well within ∼ 500-2000 years of burial, thereby limiting later pyritization, which could occur through sulfidation of less reactive phases. This result explains the low (≤ 0.4) degree of pyritization (DOP) values exhibited by both modern and ancient deposits of the ERB and lends support to the notion that pyritization in aerobic continental-margin sediments is largely associated with highly reactive detrital Fe oxides. Comparable mean C/S weight ratios for modern sediments (5.4 ± 3.3, 1σ) and mudrocks (6.9 ± 4.5) of the ERB suggest that the upper Pleistocene strata reflect a geochemical environment analogous to that of the modern margin. Specifically, the C-S-Fe signatures shared by the modern and ancient deposits are a consequence of similar detrital Fe mineralogies, initial organic-matter content (Corg ≤ 1%) and composition (C/N = 13 to 17, δ13Corg = -22 to -25‰), burial rate, and importantly, bioturbation intensity. The findings of this study have important implications for the use of C-S-Fe signatures as indicators of diagenetic processes in dynamic, continental-margin environments.

Selective separation of iron from uranium in quantitative determination of traces of uranium by alpha spectrometry in soil/sediment sample.

PubMed

Singhal, R K; Narayanan, Usha; Karpe, Rupali; Kumar, Ajay; Ranade, A; Ramachandran, V

2009-04-01

During this work, controlled redox potential methodology was adopted for the complete separation of traces of uranium from the host matrix of mixed hydroxide of Iron. Precipitates of Fe(+2) and Fe(+3) along with other transuranic elements were obtained from acid leached solution of soil by raising the pH to 9 with 14N ammonia solution. The concentration of the uranium observed in the soil samples was 200-600 ppb, whereas in sediment samples, the concentration range was 61-400 ppb.

Mercury, methylmercury, and other constituents in sediment and water from seasonal and permanent wetlands in the Cache Creek settling basin and Yolo Bypass, Yolo County, California, 2005-06

USGS Publications Warehouse

Marvin-DiPasquale, Mark; Alpers, Charles N.; Fleck, Jacob A.

2009-01-01

This report presents surface water and surface (top 0-2 cm) sediment geochemical data collected during 2005-2006, as part of a larger study of mercury (Hg) dynamics in seasonal and permanently flooded wetland habitats within the lower Sacramento River basin, Yolo County, California. The study was conducted in two phases. Phase I represented reconnaissance sampling and included three locations within the Cache Creek drainage basin; two within the Cache Creek Nature Preserve (CCNP) and one in the Cache Creek Settling Basin (CCSB) within the creek's main channel near the southeast outlet to the Yolo Bypass. Two additional downstream sites within the Yolo Bypass Wildlife Area (YBWA) were also sampled during Phase I, including one permanently flooded wetland and one seasonally flooded wetland, which had began being flooded only 1–2 days before Phase I sampling.Results from Phase I include: (a) a negative correlation between total mercury (THg) and the percentage of methylmercury (MeHg) in unfiltered surface water; (b) a positive correlation between sediment THg concentration and sediment organic content; (c) surface water and sediment THg concentrations were highest at the CCSB site; (d) sediment inorganic reactive mercury (Hg(II)R) concentration was positively related to sediment oxidation-reduction potential and negatively related to sediment acid volatile sulfur (AVS) concentration; (e) sediment Hg(II)R concentrations were highest at the two YBWA sites; (f) unfiltered surface water MeHg concentration was highest at the seasonal wetland YBWA site, and sediment MeHg was highest at the permanently flooded YBWA site; (g) a 1,000-fold increase in sediment pore water sulfate concentration was observed in the downstream transect from the CCNP to the YBWA; (h) low sediment pore water sulfide concentrations (<1 µmol/L) across all sites; and (i) iron (Fe) speciation data suggest a higher potential for microbial Fe(III)-reduction in the YBWA compared to the CCSB.Phase II sampling did not include the original three Cache Creek sites, but instead focused on the original two sites within the YBWA and a similarly paired set of seasonally and permanently flooded wetland sites within the CCSB. Sediment sampling at the YBWA and CCSB occurred approximately 28 days and 52 days, respectively, after the initial flooding of the respective seasonal wetlands, and again towards the end of the seasonal flooding period (end of May 2006). Results from Phase II sampling include: (a) sediment MeHg concentration and the percentage of THg as MeHg (%MeHg) in unfiltered surface waters were generally higher in the YBWA compared to the CCSB; (b) suspended sediment concentration (SCC) in surface water was positively correlated with both THg and MeHg in unfiltered water across all sites, although the relationship between SCC and MeHg differed for the two regions, suggesting local MeHg sources; (c) MeHg concentration in unfiltered surface water was positively correlated to sediment MeHg concentrations across all sites, supporting the suggestion of unique local (sediment) sources of MeHg to the water column; (d) THg concentration in filtered water was positively correlated with both total Fe and dissolved organic carbon (DOC), offering additional support for the role of these constituents in the partitioning of THg between particulate and dissolved phases; (e) flooding of the YBWA seasonal wetland resulted in a rapid and significant (5-fold) rise in sediment MeHg concentration within 3–4 weeks following inundation; and (f) temporal changes in sediment S and Fe speciation suggest that rates of both microbial sulfate reduction and Fe(III)-reduction were significantly higher at YBWA, compared to CCSB, during the period between flooding and drying.The geochemical data presented in this report indicate that (a) strong spatial and temporal differences in Hg speciation and transformations can occur within the range of wetland habitats found in the lower Sacramento River basin; (b) flooding of seasonal wetlands can be accompanied by a rapid increase in benthic MeHg production and the release of previously formed MeHg (generated during or since the previous flooding season) to the overlying water column; (c) S and Fe chemistry, and associated microbial reduction pathways, play an important role in mediating the speciation and transformation of Hg in these wetland habitats; (d) hydroperiod is a primary forcing function in mediating MeHg production among various wetland types; and (e) MeHg production appears to be more active in the YBWA compared to the CCSB.

Diffuse flow hydrothermal manganese mineralization along the active Mariana and southern Izu-Bonin arc system, western Pacific

USGS Publications Warehouse

Hein, J.R.; Schulz, M.S.; Dunham, R.E.; Stern, R.J.; Bloomer, S.H.

2008-01-01

Abundant ferromanganese oxides were collected along 1200 km of the active Izu-Bonin-Mariana arc system. Chemical compositions and mineralogy show that samples were collected from two deposit types: Fe-Mn crusts of mixed hydrogenetic/hydrothermal origin and hydrothermal Mn oxide deposits; this paper addresses only the second type. Mn oxides cement volcaniclastic and biogenic sandstone and breccia layers (Mn sandstone) and form discrete dense stratabound layers along bedding planes and within beds (stratabound Mn). The Mn oxide was deposited within coarse-grained sediments from diffuse flow systems where precipitation occurred below the seafloor. Deposits were exposed at the seabed by faulting, mass wasting, and erosion. Scanning electron microscopy and microprobe analyses indicate the presence of both amorphous and crystalline 10 ?? and 7 ?? manganate minerals, the fundamental chemical difference being high water contents in the amorphous Mn oxides. Alternation of amorphous and crystalline laminae occurs in many samples, which likely resulted from initial rapid precipitation of amorphous Mn oxides from waxing pulses of hydrothermal fluids followed by precipitation of slow forming crystallites during waning stages. The chemical composition is characteristic of a hydrothermal origin including strong fractionation between Fe (mean 0.9 wt %) and Mn (mean 48 wt %) for the stratabound Mn, generally low trace metal contents, and very low rare earth element and platinum group element contents. However, Mo, Cd, Zn, Cu, Ni, and Co occur in high concentrations in some samples and may be good indicator elements for proximity to the heat source or to massive sulfide deposits. For the Mn sandstones, Fe (mean-8.4%) and Mn (12.4%) are not significantly fractionated because of high Fe contents in the volcaniclastic material. However, the proportion of hydrothermal Fe (nondetrital Fe) to total Fe is remarkably constant (49-58%) for all the sample groups, regardless of the degree of Mn mineralization. Factor analyses indicate various mixtures of two dominant components: hydrothermal Mn oxide for the stratabound Mn and detrital aluminosilicate for the Mn-cemented sandstone; and two minor components, hydrothermal Fe oxyhydroxide and biocarbonate/biosilica. Our conceptual model shows that Mn mineralization was produced by hydrothermal convection cells within arc volcanoes and sedimentary prisms that occur along, the flanks and within calderas. The main source of hydrothermal fluid was seawater that penetrated through fractures, faults, and permeable volcanic edifices. The fluids were heated by magma, enriched in metals by leaching of basement rocks and sediments, and mixed with magmatic fluids and gases. Dikes and sills may have been another source of heat that drove small-scale circulation within sedimentary prisms. Copyright 2008 by the American Geophysical Union.

Diffuse flow hydrothermal manganese mineralization along the active Mariana and southern Izu-Bonin arc system, western Pacific

NASA Astrophysics Data System (ADS)

Hein, James R.; Schulz, Marjorie S.; Dunham, Rachel E.; Stern, Robert J.; Bloomer, Sherman H.

2008-08-01

Abundant ferromanganese oxides were collected along 1200 km of the active Izu-Bonin-Mariana arc system. Chemical compositions and mineralogy show that samples were collected from two deposit types: Fe-Mn crusts of mixed hydrogenetic/hydrothermal origin and hydrothermal Mn oxide deposits; this paper addresses only the second type. Mn oxides cement volcaniclastic and biogenic sandstone and breccia layers (Mn sandstone) and form discrete dense stratabound layers along bedding planes and within beds (stratabound Mn). The Mn oxide was deposited within coarse-grained sediments from diffuse flow systems where precipitation occurred below the seafloor. Deposits were exposed at the seabed by faulting, mass wasting, and erosion. Scanning electron microscopy and microprobe analyses indicate the presence of both amorphous and crystalline 10 Å and 7 Å manganate minerals, the fundamental chemical difference being high water contents in the amorphous Mn oxides. Alternation of amorphous and crystalline laminae occurs in many samples, which likely resulted from initial rapid precipitation of amorphous Mn oxides from waxing pulses of hydrothermal fluids followed by precipitation of slow forming crystallites during waning stages. The chemical composition is characteristic of a hydrothermal origin including strong fractionation between Fe (mean 0.9 wt %) and Mn (mean 48 wt %) for the stratabound Mn, generally low trace metal contents, and very low rare earth element and platinum group element contents. However, Mo, Cd, Zn, Cu, Ni, and Co occur in high concentrations in some samples and may be good indicator elements for proximity to the heat source or to massive sulfide deposits. For the Mn sandstones, Fe (mean 8.4%) and Mn (12.4%) are not significantly fractionated because of high Fe contents in the volcaniclastic material. However, the proportion of hydrothermal Fe (nondetrital Fe) to total Fe is remarkably constant (49-58%) for all the sample groups, regardless of the degree of Mn mineralization. Factor analyses indicate various mixtures of two dominant components: hydrothermal Mn oxide for the stratabound Mn and detrital aluminosilicate for the Mn-cemented sandstone; and two minor components, hydrothermal Fe oxyhydroxide and biocarbonate/biosilica. Our conceptual model shows that Mn mineralization was produced by hydrothermal convection cells within arc volcanoes and sedimentary prisms that occur along the flanks and within calderas. The main source of hydrothermal fluid was seawater that penetrated through fractures, faults, and permeable volcanic edifices. The fluids were heated by magma, enriched in metals by leaching of basement rocks and sediments, and mixed with magmatic fluids and gases. Dikes and sills may have been another source of heat that drove small-scale circulation within sedimentary prisms.

Physical versus chemical effects on bacterial and bromide transport as determined from on site sediment column pulse experiments

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

Hall, James A.; Mailloux, Brian J.; Onstott, Tullis C.

2005-02-01

Twenty eight bacterial and Br transport experiments were performed in the field to determine the effects of physical and chemical heterogeneity of the aquifer sediment. The experiments were performed using groundwater from two field locations to examine the effects of groundwater chemistry on transport. Groundwater was extracted from multilevel samplers and pumped through 7 cm long columns of intact sediment or re-packed sieved and coated or uncoated sediment from the underlying aquifer. Two bacterial strains, Comamonas sp. DA001 and Paenibacillus polymyxa FER-02, were injected along with Br into the influent end of the columns to examine the effect of cellmore » morphology and surface properties on bacterial transport. The effect of column sediment grain size and mineral coatings coupled with groundwater geochemistry were also delineated. Significant irreversible attachment of DA001 was observed in the Fe oxyhydroxide coated columns, but only in the sub-oxic groundwater where the concentrations of dissolved organic carbon (DOC) were ca. 1 ppm. In the oxic groundwater where DOC was ca. 8 ppm, little attachment of DA001 to the Fe oxyhydroxide coated columns was observed. This indicates that DOC can significantly reduce bacterial attachment due electrostatic interactions. The larger and more negatively charged FER-02 displayed increasing attachment with decreasing grain size regardless of DOC concentration, and modeling of FER-02 attachment revealed that the presence of Fe and Al coatings on the sediment also promoted attachment. Finally, the presence of Al coatings and Al containing minerals appeared to significantly retard the Br tracer regardless of the concentration of DOC. These findings suggest that DOC in shallow oxic groundwater aquifers can significantly enhance the transport of bacteria by reducing attachment to Fe, Mn and Al oxyhydroxides. This effect is profound for weakly charged, hydrophilic bacteria and may contribute to differences in observations between laboratory experiments verses field-scale investigations particularly if the groundwater pH remains circum-neutral and Fe oxyhydroxide phases exist. These observations validate the novel approach taken in the experiments outlined here of performing laboratory-scale experiments on site to facilitate the use of fresh groundwater and thus be more representative of in situ groundwater conditions.« less

Potentially bioavailable ferrous iron nanoparticles in glacial sediments

NASA Astrophysics Data System (ADS)

Hawkings, J.; Benning, L. G.; Raiswell, R.; Kaulich, B.; Araki, T.; Abyaneh, M.; Koch-Müller, M.; Stockdale, A.; Tranter, M.; Wadham, J.

2017-12-01

Iron (Fe) is an essential nutrient for marine phytoplankton, the primary producers of the ocean. Despite it being the fourth most abundant element in the Earth's crust, it is highly insoluble, due in part to its rapid oxidation from ferric (Fe2+) to ferrous phases (Fe3+), which often leads to the formation of nanoparticulate iron oxyhydroxide phases1. The insoluble nature of Fe in oxygenated waters means Fe limitation of primary producers is prevalent in 30-50% of the world's oceans, including areas of high biological productivity proximal to significant glacial activity (e.g., the Southern Ocean). Glaciers and ice sheets are a significant source of nanoparticulate Fe, which may be important in sustaining the high productivity observed in the near coastal regions proximal to glacial coverage. The reactivity of particulate iron is poorly understood, despite its importance in the ocean Fe inventory. Here we combined geochemical extractions, high-resolution imaging and spectroscopy to investigate the abundance, morphology and valence state of reactive iron in glacial sediments. Our results document the widespread occurrence of amorphous and Fe(II)-rich nanoparticles in glacial meltwaters and icebergs. Fe(II) is thought to be highly bioavailable in marine environments. We argue that glaciers and ice sheets are therefore able to supply potentially bioavailable Fe(II)-containing nanoparticulate material for downstream ecosystems, including those in a marine setting. The flux of bioavailable particulate iron from Arctic glaciers may increase as rising air temperatures lead to higher meltwater export.

Effects of pollution on the geochemical properties of marine sediments across the fringing reef of Aqaba, Red Sea.

PubMed

Al-Rousan, Saber; Al-Taani, Ahmed A; Rashdan, Maen

2016-09-15

The Gulf of Aqaba is of significant strategic and economic value to all gulf-bordering states, particularly to Jordan, where it provides Jordan with its only marine outlet. The Gulf is subject to a variety of impacts posing imminent ecological risk to its unique marine ecosystem. We attempted to investigate the status of metal pollution in the coastal sediments of the Jordanian Gulf of Aqaba. The distribution of Cd, Cr, Zn, Cu, Pb, Al, Fe, and Mn concentrations were determined in trapped and bottom-surface sediments at three selected sites at different depths. In addition, monthly sedimentation rates at varying water depths were also estimated at each sampling site using sediment traps. The high concentrations of Cd, Cr, Zn were recorded at the Phosphate Loading Birth (PLB) site followed by the Industrial Complex (IC) site indicating their dominant anthropogenic source (i.e., the contribution of industrial activities). However, Fe, Al, and Mn contents were related to inputs from the terrigenous (crustal) origin. Except for Al, Fe and Mn at the PLB site, the concentrations of metals exhibited a decreasing trend with increasing water depth (distance from the shoreline). The PLB site also showed the highest sedimentation rate which decreased with increasing water depth. The Enrichment factors (EFs) showed that Cd was the most enriched element in the sediment (indicating that Cd pollution is widespread), whereas the least enriched metal in sediments was Cu. EF values suggested that the coastal area is impacted by a combination of human and natural sources of metals, where the anthropogenic sources are intense in the PLB site (north of Gulf of Aqaba). The MSS area is potentially the least polluted, consistent with being a marine reserve. The IC sediments have been found to be impacted by human activities but less intensely compared to the PLB area. These results suggested that there are two sources of metals in sediments; the primary source is likely closer to PLB, while the secondary is nearby the IC. Copyright © 2016 Elsevier Ltd. All rights reserved.

Heavy metal assessment using geochemical and statistical tools in the surface sediments of Vembanad Lake, Southwest Coast of India.

PubMed

Selvam, A Paneer; Priya, S Laxmi; Banerjee, Kakolee; Hariharan, G; Purvaja, R; Ramesh, R

2012-10-01

The geochemical distribution and enrichment of ten heavy metals in the surface sediments of Vembanad Lake, southwest coast of India was evaluated. Sediment samples from 47 stations in the Lake were collected during dry and wet seasons in 2008 and examined for heavy metal content (Al, Fe, Mn, Cr, Zn, Ni, Pb, Cu, Co, Cd), organic carbon, and sediment texture. Statistically significant spatial variation was observed among all sediment variables, but negligible significant seasonal variation was observed. Correlation analysis showed that the metal content of sediments was mainly regulated by organic carbon, Fe oxy-hydroxides, and grain size. Principal component analysis was used to reduce the 14 sediment variables into three factors that reveal distinct origins or accumulation mechanisms controlling the chemical composition in the study area. Pollution intensity of the Vembanad Lake was measured using the enrichment factor and the pollution load index. Severe and moderately severe enrichment of Cd and Zn in the north estuary with minor enrichment of Pb and Cr were observed, which reflects the intensity of the anthropogenic inputs related to industrial discharge into this system. The results of pollution load index reveal that the sediment was heavily polluted in northern arm and moderately polluted in the extreme end and port region of the southern arm of the lake. A comparison with sediment quality guideline quotient was also made, indicating that there may be some ecotoxicological risk to benthic organisms in these sediments.

Unravelling metal mobility under complex contaminant signatures.

PubMed

de Souza Machado, Anderson Abel; Spencer, Kate L; Zarfl, Christiane; O'Shea, Francis T

2018-05-01

Metals are concerning pollutants in estuaries, where contamination can undergo significant remobilisation driven by physico-chemical forcing. Environmental concentrations of metals in estuarine sediments are often higher than natural backgrounds, but show no contiguity to potential sources. Thus, better understanding the metal mobility in estuaries is essential to improve identification of pollution sources and their accountability for environmental effects. This study aims to identify the key biogeochemical drivers of metal mobilisation on contaminated estuarine sediments through (1) evaluation of the potential mobilisation under controlled conditions, and (2) investigation of the relevance of metal mobilisation for in situ pollution levels in an area with multiple contaminant sources. Sediments from a saltmarsh adjacent to a coastal landfill, a marina, and a shipyard on the Thames Estuary (Essex, UK) were exposed in the laboratory (24h, N=96, 20°C) to water under various salinity, pH, and redox potential. Major cations, Fe(II), and trace metal concentrations were analysed in the leachate and sediment. Salinity, pH and redox had a significant effect on metal mobilisation (p<0.001), e.g. under certain conditions Fe(II) leaching was increased ~1000-fold. Measurements in situ of surface and subsurface sediment cores revealed that landfill proximity poorly explained metal spatial distribution. However, physicochemical parameters explained up to 97% of geochemically normalized metal concentrations in sediments. Organic matter and pH were dominant factors for most of the metal concentrations at the sediment surface. At subsurface, major cations (Ca, Na, Mg and K) were determinant predictors of metal concentrations. Applying the empirical model obtained in the laboratory to geochemical conditions of the studied saltmarsh it was possible to demonstrate that Fe mobilisation regulates the fate of this (and other) metal in that area. Thus, present results highlight the importance of metal mobility to control sediment pollution and estuarine fate of metals. Copyright © 2017 Elsevier B.V. All rights reserved.

Heavy metals in soils and sediments from Dongting Lake in China: occurrence, sources, and spatial distribution by multivariate statistical analysis.

PubMed

Zhang, Yaxin; Tian, Ye; Shen, Maocai; Zeng, Guangming

2018-05-01

Heavy metal contamination in soils/sediments and its impact on human health and ecological environment have aroused wide concerns. Our study investigated 30 samples of soils and sediments around Dongting Lake to analyze the concentration of As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn in the samples and to distinguish the natural and anthropogenic sources. Also, the relationship between heavy metals and the physicochemical properties of samples was studied by multivariate statistical analysis. Concentration of Cd at most sampling sites were more than five times that of national environmental quality standard for soil in China (GB 15618-1995), and Pb and Zn levels exceeded one to two times. Moreover, Cr in the soil was higher than the national environmental quality standards for one to two times while in sediment was lower than the national standard. The investigation revealed that the accumulations of As, Cd, Mn, and Pb in the soils, and sediments were affected apparently by anthropogenic activities; however, Cr, Fe, and Ni levels were impacted by parent materials. Human activities around Dongting Lake mainly consisted of industrial activities, mining and smelting, sewage discharges, fossil fuel combustion, and agricultural chemicals. The spatial distribution of heavy metal in soil followed the rule of geographical gradient, whereas in sediments, it was significantly affected by the river basins and human activities. The result of principal component analysis (PCA) demonstrated that heavy metals in soils were associated with pH and total phosphorus (TP), while in sediments, As, Cr, Fe, and Ni were closely associated with cation exchange capacity (CEC) and pH, where Pb, Zn, and Cd were associated with total nitrogen (TN), TP, total carbon (TC), moisture content (MC), soil organic matter (SOM), and ignition lost (IL). Our research provides comprehensive approaches to better understand the potential sources and the fate of contaminants in lakeshore soils and sediments.

Determination of heavy metal levels in water, sediment and tissues of tench (Tinca tinca L., 1758) from Beyşehir Lake (Turkey).

PubMed

Tekin-Ozan, Selda

2008-10-01

In the present study, some heavy metals (Cu, Fe, Zn and Mn) were seasonally determined in water, sediment and some tissues of fish Tinca tinca from Beyşehir Lake, which is an important bird nesting and visiting area, a water source for irrigation and drinking. In the water, Fe has the highest concentrations among the studied metals. Generally, the metal concentrations increased in the hottest period decreased in warm seasons. Results for levels in water were compared with national and international water quality guidelines, as well as literature data reported for the lakes. Fe was the highest in sediment samples, also Cu and Zn were the highest in spring, while Fe and Mn were in autumn. Among the heavy metals studied, Cu and Mn were below the detection limits in some tissues. Generally, higher concentrations of the tested metals were found in the summer and winter, compared with those during the autumn and spring seasons. High levels of heavy metals were found in liver of T. tinca, while low levels in muscle samples. Metal concentrations in the muscle of examined fish were within the safety permissible levels for human consumption. The present study shows that precautions need to be taken in order to prevent further heavy metal pollution.

Bioaccumulation of Heavy Metals in Water, Sediments, and Tissues and Their Histopathological Effects on Anodonta cygnea (Linea, 1876) in Kabul River, Khyber Pakhtunkhwa, Pakistan

PubMed Central

Khan, Muhammad Iftikhar; Gulfam, Naila; Siraj, Muhammad; Zaidi, Farrah; Ahmadullah; Abidullah; Fatima, Syeda Hira; Noreen, Shumaila; Hamidullah; Shah, Zafar Ali; Qadir, Fazli

2018-01-01

The present investigation aimed to assess the concentrations of selected heavy metals in water and sediments and their bioaccumulation in tissues of freshwater mussels and their histopathological effects on the digestive gland, gills, and gonads of Anodonta cygnea. Water, sediments, and freshwater mussel samples were collected at four sites, that is, reference and polluted sites, along the Kabul River, Khyber Pakhtunkhwa. The polluted sites were receiving effluents from the industrial, agricultural, municipal, and domestic sources. The order of metals in the water was Zn > Pb > Ni > Cu > Mn > Fe > Cr > Cd, in sediments the order was Fe > Zn > Cr > Ni > Mn > Pb > Cu > Cd, and in the soft tissues the order was Fe > Zn > Mn > Pb > Cu > Cr > Ni > Cd. Histopathological alterations observed in polluted sites of Kabul River were inflammation, hydropic vacuolation, and lipofuscin pigments (in digestive gland), gill lamellar fusion, dilated hemolymphatic sinus, clumping, and generation of cilia and hemocytic infiltration (in gills), and atresia, necrosis, granulocytoma, hemocytic infiltration, and lipofuscin pigments (in gonads). The histopathological alterations in the organs of Anodonta cygnea can be considered as reliable biomarkers in biomonitoring of heavy metal pollution in aquatic ecosystems. PMID:29693003

Microbial Sulfate Reduction Enhances Arsenic Mobility Downstream of Zerovalent-Iron-Based Permeable Reactive Barrier.

PubMed

Kumar, Naresh; Couture, Raoul-Marie; Millot, Romain; Battaglia-Brunet, Fabienne; Rose, Jérôme

2016-07-19

We assessed the potential of zerovalent-iron- (Fe(0)) based permeable reactive barrier (PRB) systems for arsenic (As) remediation in the presence or absence of microbial sulfate reduction. We conducted long-term (200 day) flow-through column experiments to investigate the mechanisms of As transformation and mobility in aquifer sediment (in particular, the PRB downstream linkage). Changes in As speciation in the aqueous phase were monitored continuously. Speciation in the solid phase was determined at the end of the experiment using X-ray absorption near-edge structure (XANES) spectroscopy analysis. We identified thio-As species in solution and AsS in solid phase, which suggests that the As(V) was reduced to As(III) and precipitated as AsS under sulfate-reducing conditions and remained as As(V) under abiotic conditions, even with low redox potential and high Fe(II) content (4.5 mM). Our results suggest that the microbial sulfate reduction plays a key role in the mobilization of As from Fe-rich aquifer sediment under anoxic conditions. Furthermore, they illustrate that the upstream-downstream linkage of PRB affects the speciation and mobility of As in downstream aquifer sediment, where up to 47% of total As initially present in the sediment was leached out in the form of mobile thio-As species.

DEVELOPMENT OF SULFATE RADICAL-BASED CHEMICAL OXIDATION PROCESSES FOR TREATMENT OF PCBS

EPA Science Inventory

This study investigates transition metal based activation of peroxymonosulfate for generation of highly reactive sulfate radicals to degrade Polychlorinated Biphenyls (PCBs) in contaminated aqueous and sediment systems. Environmental friendly transition metal iron (Fe (II), Fe (I...

Uptake of uranium by aquatic plants growing in fresh water ecosystem around uranium mill tailings pond at Jaduguda, India.

PubMed

Jha, V N; Tripathi, R M; Sethy, N K; Sahoo, S K

2016-01-01

Concentration of uranium was determined in aquatic plants and substrate (sediment or water) of fresh water ecosystem on and around uranium mill tailings pond at Jaduguda, India. Aquatic plant/substrate concentration ratios (CRs) of uranium were estimated for different sites on and around the uranium mill tailings disposal area. These sites include upstream and downstream side of surface water sources carrying the treated tailings effluent, a small pond inside tailings disposal area and residual water of this area. Three types of plant groups were investigated namely algae (filamentous and non-filamentous), other free floating & water submerged and sediment rooted plants. Wide variability in concentration ratio was observed for different groups of plants studied. The filamentous algae uranium concentration was significantly correlated with that of water (r=0.86, p<0.003). For sediment rooted plants significant correlation was found between uranium concentration in plant and the substrate (r=0.88, p<0.001). Both for other free floating species and sediment rooted plants, uranium concentration was significantly correlated with Mn, Fe, and Ni concentration of plants (p<0.01). Filamentous algae, Jussiaea and Pistia owing to their high bioproductivity, biomass, uranium accumulation and concentration ratio can be useful for prospecting phytoremediation of stream carrying treated or untreated uranium mill tailings effluent. Copyright © 2015 Elsevier B.V. All rights reserved.

The development of Fe-nodules surrounding biological material mediated by microorganisms

NASA Astrophysics Data System (ADS)

Yoshida, Hidekazu; Yamamoto, Koshi; Murakami, Yuki; Katsuta, Nagayoshi; Hayashi, Toru; Naganuma, Takeshi

2008-09-01

Takashikozo is a phenomenon of Quaternary sediments in Japan. They are cylindrical Fe-oxyhydroxide nodules that form as plaques round plant roots, where Fe is preferentially concentrated to develop a solid wall. Structural features suggest that after the roots have decayed, the central space where the roots were situated acts as a flow path for oxidized water. Analysis of microbial 16S rDNA extracted from the nodules identified iron-oxidizing bacteria encrusted round the roots where they are the likely initiators of nodule formation. Direct microscopic observation revealed an accumulation of Fe-oxyhydroxides that fill the pore spaces and is also likely to be linked with the encrusting microbial colonies. Geological history and nanofossil evidence suggest that these Fe-nodules may have been buried at a depth of up to several tens of meters for at least 105 years in reducing Quaternary sediments. Thus Fe-oxyhydroxide nodules that have formed in a geological environment at the interfaces between water and rock by microbial mediation can persist under reducing conditions. If this is the case, the phenomenon is significant as an analogue of post-closure conditions in radioactive waste repositories, since it could influence nuclide migration.

Macro- and microelement distribution in organs of Glyceria maxima and biomonitoring applications.

PubMed

Klink, Agnieszka; Stankiewicz, Andrzej; Wisłocka, Magdalena; Polechońska, Ludmiła

2014-07-01

The content of nutrients (N, P, K, Ca and Mg) and of trace metals (Fe, Cu, Mn, Zn, Pb, Cd, Co and Ni) in water, bottom sediments and various organs of Glyceria maxima from 19 study sites selected in the Jeziorka River was determined. In general, the concentrations of nutrients recorded in the plant material decreased in the following order: leaf>root>rhizome>stem, while the concentrations of the trace elements showed the following accumulation scheme: root>rhizome>leaf>stem. The bioaccumulation and transfer factors for nutrients were significantly higher than for trace metals. G. maxima from agricultural fields was characterised by the highest P and K concentrations in leaves, and plants from forested land contained high Zn and Ni amounts. However, the manna grass from small localities showed high accumulation of Ca, Mg and Mn. Positive significant correlations between Fe, Cu, Zn, Cd, Co and Ni concentrations in water or sediments and their concentrations in plant indicate that G. maxima may be employed as a biomonitor of trace element contamination. Moreover, a high degree of similarity was noted between self-organizing feature map (SOFM)-grouped sites of comparable quantities of elements in the water and sediments and sites where G. maxima had a corresponding content of the same elements in its leaves. Therefore, SOFM could be recommended in analysing ecological conditions of the environment from the perspective of nutrients and trace element content in different plant species and their surroundings.

Biogeochemistry of sediments from restricted exchange environments of Kandalaksha bay, White Sea, Russian Arctic

NASA Astrophysics Data System (ADS)

Koukina, Sofia

2010-05-01

The Arctic has come under intense scrutiny by the scientific community in recent years. The White sea of Russian Arctic is characterised by extreme diversity of enclosed estuarine systems that are often sites of unique biota. The present study focuses on the sediments of the inner part of Kandalaksha bay, adjacent to the Karelian shore of the White sea. Due to the endogenous crustal uplift (4 mm per year an average), this bay contains a continuum of shallow environments, ranging from estuaries of different types to separating basins where water exchange is severely restricted. The evolution of sediments here is caused by specific depositional conditions, which are strongly affected by small-scale hydrological and hydrodynamic processes unique for each particular area. The detrital, non-detrital (labile) and organically bound fractions of Fe, Mn, Cu, Zn, Pb, Cr, Li along with TOC, n-alkanes, granulometry and bacteria species distribution were determined in surface sediment samples from representative separating basins and small exchange environments of the Karelian shore. The sediments studied tended to be terrigenous with major input of organic matter from both terrestrial remains and autochthonous microbial sources. According to sediment quality guidelines, all trace-metal contents were below the threshold levels. The strong positive correlation between labile Fe, Mn, Cr, Zn and total Li revealed their association with Fe-hydroxides and clay minerals, while Pb and especially Cu exhibited their affinity to organic matter. The metals in sediments studied occur mainly in a biogeochemically stabile mineral-incorporated form, which comprises 77-99% of total metal content. The contents of labile form were high for Fe, Mn and Cr (up to 7.5 %) in sediments from separating basins, which are also enriched in clay fraction <0.01 mm (up to 60%), TOC (5-20%) and hydrogen sulfide. This is due to the anaerobic conditions formed in sediments in the coarse of separating process. In such environments with restricted water exchange with an open sea, from one side, and permanent organic matter input from land, from the other side, the mass extinction of marine biota with simultaneous spread of microbiota take place. Thus, in the basins studied the colonies of Thiocapsa roseopersicina and Amoebobacter sp., Microcystis sp. and Oscillatotia sp., and Beggiatoa alba (B.Gigantea) were found. The present study can serve as a basis of an environmenthal assessment of the region and objective anoxia prognosis in Arctic ecosystems.

Ferromanganese deposits from the Gulf of Alaska seamount province: mineralogy, chemistry, and origin.

USGS Publications Warehouse

Koski, R.A.

1988-01-01

Petrographic and chemical data presented and discussed permit the following conclusions regarding the high-latitude Gulf of Alaska (GA) Fe-Mn deposits: 1) thick (10-50 mm) Fe-Mn crusts form on alkali-basalt and volcaniclastic substrates by hydrogenetic processes, contain delta -MnO2 as the principal Mn phase, and have compositions similar to those of seamount crusts from comparable depths in the Hawaiian archipelago. GA crusts have higher Mn/Fe and lower Co contents than crusts from low-altitude, central Pacific seamounts; 2) thin (<10 mm) crusts on tuffaceous conglomerate, sandstone and phosphorite have a high proportion of crystalline Mn oxides and are genetically related to vein deposits; 3) vein deposits of todorokite and cryptomelane form during low-T oxidative diagenesis of volcanogenic sediment. Mn and other transition metals are supplied during the initial palagonitization of basaltic glass. The oxidation of Fe2+ to Fe3+ in palagonite and the dissolution of the diluted microfossil fraction of the sediment lower the Eh of the ambient pore fluid and enhance the solubility of Mn2+. The K released during the formation of palagonite may be redeposited in secondary phyllosilicate minerals, phillipsite, todorokite and cryptomelane; 4) the vein deposits formed soon after the deposition of sediment derived from the erosion and mass wasting of Mill Seamount but before crust deposition. Therefore, the deposition of hydrogenous crusts and the deposition of diagenetic veins are chemically distinct processes in time and space.-J.M.H.

Post-depositional redistribution processes and their effects on middle rare earth element precipitation and the cerium anomaly in sediments in the South Korea Plateau, East Sea

NASA Astrophysics Data System (ADS)

Kang, Jeongwon; Jeong, Kap-Sik; Cho, Jin Hyung; Lee, Jun Ho; Jang, Seok; Kim, Seong Ryul

2014-03-01

We sampled two box-core sediments from the slope of the eastern South Korea Plateau (SKP) in the East Sea (Sea of Japan) at water depths of 1400 and 1700 m. Two chemical fractions of extractable (hydroxylamine/acetic acid) and residual rare earth elements (REEs) together with Al, Ca, Fe, Mg, Mn, P, S, As, Mo, and U were analyzed to assess the post-depositional redistribution of REEs. Extractable Fe and Mn are noticeably abundant in the oxic topmost sediment layer (<3 cm). However, some trace elements (e.g., S, As, Mo, U) are more abundant at depth, where redox conditions are different. Analysis of upper continental crust (UCC)-normalized (La/Gd)UCC, (La/Yb)UCC, and (Ce/Ce*)UCC revealed that the extractable REE is characterized by middle REE (MREE) enrichment and a positive cerium (Ce) anomaly, different from the case of the residual fraction which shows slight enrichment in light REEs (LREEs) with no Ce anomaly. The extractable MREEs seem to have been incorporated into high-Mg calcite during reductive dissolution of Fe oxyhydroxides. In the top sediment layer, the positive Ce anomaly is attributed to Ce oxide, which can be mobilized in deeper oxygen-poor environments and redistributed in the sediment column. In addition, differential concentrations of Ce and other LREEs in pore water appear to result in variable (Ce/Ce*)UCC ratios in the extractable fraction at depth.

Chemical speciation and ecological risk assessment of arsenic in marine sediments from Izmir Bay (Eastern Aegean Sea).

PubMed

Gonul, L T

2015-12-01

Total arsenic, arsenic(III) and (V), Fe, and Mn were measured in 17 surface sediment samples from Izmir Bay. The concentrations and ecological risk of As were characterized in the sediment affected by urban and agricultural activities. Total As ranged from 8.87 to 28.3 μg g(-1) dry weight (96.5-99.9 % as inorganic As). Distribution of total As and total As/Fe followed a different trend in sediments at all sampling sites. Arsenite (As(III)) was the most dominant form followed by As(V), while organic arsenic represented a minor constituent (0.03 to 3.49 %). The highest concentration of total As was observed at Gediz River estuary and exceeded lower threshold value (threshold effects level (TEL)). Due to the biological reduction of As(V) and abundance of Fe (oxyhydr)oxides in the sediments, most inorganic As in the Izmir Bay was present as As(III). Besides, the levels of As were >TEL and

Trace metal partitioning in Thalassia testudinum and sediments in the Lower Laguna Madre, Texas.

PubMed

Whelan, Thomas; Espinoza, Jorge; Villarreal, Xiomara; Cottagoma, Maria

2005-01-01

Seagrass communities dominate the Laguna Madre, which accounts for 25% of the coastal region of Texas. Seagrasses are essential to the health of the Laguna Madre (LM) and have experienced an overall decline in coverage in the Lower Laguna Madre (LLM) since 1967. Little is known on the existing environmental status of the LLM. This study focuses on the trace metal chemistry of four micronutrient metals, Fe, Mn, Cu, and Zn, and two non-essential metals, Pb and As, in the globally important seagrass Thalassia testudinum. Seasonal trends show that concentrations of most essential trace metals increase in the tissue during the summer months. With the exception of (1) Cu in the vertical shoot and root, and (2) Mn in the roots, no significant positive correlation exists between the rhizosphere sediment and T. testudinum tissue. Iron indicates a negative correlation between the morphological units and the rhizosphere sediments. No other significant relationship was found between the sediments and the T. testudinum tissue. Mn was enriched up to 10-fold in the leaf tissue relative to the other morphological units and also enriched relative to the rhizosphere sediments. Both Cu and Mn appear to be enriched in leaf tissue compared to other morphological units and also enriched relative to the Cu and Mn in the rhizoshpere sediments. Sediments cores taken in barren areas were slightly elevated in Zn relative to the rhizosphere sediments, whereas no other metals showed statistical differences between barren sediment cores and rhizosphere sediments. However, no correlation was measured in T. testudinum tissue and Zn in rhizosphere sediments. Previous studies suggested that Fe/Mn ratios could indicate differences between seagrass environments. Our results indicate that there is an influence from the Rio Grande in the Fe/Mn signature in sediments, and that ratio is not reflected in the T. testudinum tissue. The results from this study show that the LLM contains trace metal concentrations less than or equal to values for uncontaminated locations worldwide. In addition, there appears to be a complex partitioning in the trace metals in the morphological units of T. testudinum tissue and that analysis only of the leaf may not be indicative of the trace metal levels in this important seagrass species.

Impact of terrestrial mining and intensive agriculture in pollution of estuarine surface sediments: Spatial distribution of trace metals in the Gulf of Urabá, Colombia.

PubMed

Vallejo Toro, Pedro Pablo; Vásquez Bedoya, Luis Fernando; Correa, Iván Darío; Bernal Franco, Gladys Rocío; Alcántara-Carrió, Javier; Palacio Baena, Jaime Alberto

2016-10-15

The Gulf of Urabá (northwestern Colombia) is a geostrategic region, rich in biodiversity and natural resources. Its economy is mainly based on agribusinesses and mining activities. In this research is determined the impact of these activities in bottom surface sediments of the estuary. Thus, grain size, total organic carbon, total nitrogen, carbonates, Ag, Al, Ca, Cr, Cu, Fe, Hg, Mg, Mn, Ni, Pb and Zn concentrations from 17 surface sediment samples were obtained and enrichment factors (EF) as well as geo-accumulation indices (Igeo) were calculated to determine the contamination level in the gulf. EF and Igeo values revealed that the estuary is extremely contaminated with Ag and moderately contaminated with Zn. Therefore, the observed enrichment of Ag may be explained as a residue of the extraction of gold and platinum-group metals and the enrichment with Zn associated mainly to pesticides used in banana plantations. Copyright © 2016 Elsevier Ltd. All rights reserved.

Interannual heavy element and nutrient concentration trends in the top sediments of Venice Lagoon (Italy).

PubMed

Masiol, Mauro; Facca, Chiara; Visin, Flavia; Sfriso, Adriano; Pavoni, Bruno

2014-12-15

The elemental composition of surficial sediments of Venice Lagoon (Italy) in 1987, 1993, 1998 and 2003 were investigated. Zn and Cr concentrations resulted in higher than background levels, but only Cd and Hg were higher than legal quality standards (Italian Decree 2010/260 and Water Framework Directive 2000/60/EC). Contaminants with similar spatial distribution are sorted into three groups by means of correlation analysis: (i) As, Co, Cd, Cu, Fe, Pb, Zn; (ii) Ni, Cr; (iii) Hg. Interannual concentrations are compared by applying a factor analysis to the matrix of differences between subsequent samplings. A general decrease of heavy metal levels is observed from 1987 to 1993, whereas particularly high concentrations of Ni and Cr are recorded in 1998 as a consequence of intense clam fishing, subsequently mitigated by better prevention of illegal harvesting. Due to the major role played by anthropogenic sediment resuspension, bathymetric variations are also considered. Copyright © 2014 Elsevier Ltd. All rights reserved.

Speciations of trace metals in the Danube alluvial sediments within an oil refinery.

PubMed

Relić, Dubravka; Dordević, Dragana; Popović, Aleksandar; Blagojević, Tamara

2005-07-01

A sequential extraction procedure was applied to identify forms of Ni, Zn, Pb and Cu with Fe- and Mn-oxides associated in alluvial sediments of the River Danube within Pancevo Oil Refinery (Serbia). The five steps of the sequential extraction procedure partitioned metals into: CH(3)COONH(4) extractable (S1); NH(2)OH.HCl carbonate extractable and easily reducible (S2); (NH(4))(2)C(2)O(2)/H(2)C(2)O(2) moderately reducible (S3); H(2)O(2)-HNO(3) organic extractable (S4); and HCl acid soluble residue (S5). Extracted concentrations of trace metals, analyzed after all five steps, were found to be (mg kg(-1)) for Mn: 656, Fe: 26734, Ni: 32.3, Zn: 72.8, Pb: 13.4 and Cu: 27.0. Most of the elements were found in acid soluble residue, characterizing stable compounds in sediments. Non-residual fractions of trace metals (sum of the first four fractions) were analyzed because they are more bioavailable than the residual amount. Correlation analysis and two multivariate analysis methods (principal component and cluster analysis) were used to understand and visualize the associations between the non-residual fractions of trace metals and certain forms, more or less crystalline of Fe- and Mn-oxides within the analyzed sediments, since Fe- and Mn-oxides play an important role in trace metal sorption within aquatic systems, especially within the Danube alluvium where the fluctuations of groundwater are very frequent and the level of groundwater could come close to surface.

Arsenic mobilization in the Brahmaputra plains of Assam: groundwater and sedimentary controls.

PubMed

Sailo, Lalsangzela; Mahanta, Chandan

2014-10-01

Arsenic (As) mobilization to the groundwater of Brahmaputra floodplains was investigated in Titabor, Jorhat District, located in the North Eastern part of India. The groundwater and the aquifer geochemistry were characterized in the study area. The range of As concentration in the groundwater varies from 10 to 440 μg/l with mean concentration 210 μg/l. The groundwaters are characterized by high dissolved Fe, Mn, and HCO₃(-) and low concentrations of NO₃(-) and SO₄(2-) indicating the reduced conditions prevailing in the groundwater. In order to understand the actual mobilization processes in the area, six core drilling surrounding the two target tube wells (T1 and T2) with high As concentration (three drill-cores surrounds each tube well closely) was done. The sediment was analyzed its chemical, mineralogical, and elemental compositions. A selective sequential extraction suggested that most of the As in the sediment is bound to Fe oxides fractions (32 to 50%) and the competition for adsorption site by anions (PO₄(3-)) also accounts to significant fractions of the total arsenic extracted. High variability in the extraction as well as properties of the sediment was observed due to the heterogeneity of the sediment samples with different chemical properties. The SEM and EDX results indicate the presence of Fe, Mn coating along with As for most of the sample, and the presence of As associated minerals were calculated using PHREEQC. The mobilization of As into the groundwater was anticipated to be largely controlled by the reductive dissolution of Fe oxides and partly by the competitive anions viz. PO₄(3-).

New insights into the mineralogy of the Atlantis II Deep metalliferous sediments, Red Sea

NASA Astrophysics Data System (ADS)

Laurila, Tea E.; Hannington, Mark D.; Leybourne, Matthew; Petersen, Sven; Devey, Colin W.; Garbe-Schönberg, Dieter

2015-12-01

The Atlantis II Deep of the Red Sea hosts the largest known hydrothermal ore deposit on the ocean floor and the only modern analog of brine pool-type metal deposition. The deposit consists mainly of chemical-clastic sediments with input from basin-scale hydrothermal and detrital sources. A characteristic feature is the millimeter-scale layering of the sediments, which bears a strong resemblance to banded iron formation (BIF). Quantitative assessment of the mineralogy based on relogging of archived cores, detailed petrography, and sequential leaching experiments shows that Fe-(oxy)hydroxides, hydrothermal carbonates, sulfides, and authigenic clays are the main "ore" minerals. Mn-oxides were mainly deposited when the brine pool was more oxidized than it is today, but detailed logging shows that Fe-deposition and Mn-deposition also alternated at the scale of individual laminae, reflecting short-term fluctuations in the Lower Brine. Previous studies underestimated the importance of nonsulfide metal-bearing components, which formed by metal adsorption onto poorly crystalline Si-Fe-OOH particles. During diagenesis, the crystallinity of all phases increased, and the fine layering of the sediment was enhanced. Within a few meters of burial (corresponding to a few thousand years of deposition), biogenic (Ca)-carbonate was dissolved, manganosiderite formed, and metals originally in poorly crystalline phases or in pore water were incorporated into diagenetic sulfides, clays, and Fe-oxides. Permeable layers with abundant radiolarian tests were the focus for late-stage hydrothermal alteration and replacement, including deposition of amorphous silica and enrichment in elements such as Ba and Au.

Fractionation profile and mobility pattern of metals in sediments from the Mediterranean Coast, Libya.

PubMed

Nasr, Samir M; Okbah, Mohamed A; El Haddad, Huda S; Soliman, Naglaa F

2015-07-01

A five-step sequential extraction technique, following Tessier's protocol, has been applied to determine the chemical association of Cd, Cu, Fe, Pb, and Zn with major sedimentary phases (exchangeable, carbonate, manganese and iron oxides, organic and residual fraction) in surface sediments from 14 stations off the Libyan Mediterranean coast. This study is a first approach of chemical fractionation of these metals in one of the most economically important area of the Libyan coastline in Mediterranean Sea. The total metal content was also determined. The total concentration of metals ranged from 5-10.5 mg/kg for Cd, 9.1-22.7 mg/kg for Cu, 141.8-1056.8 mg/kg for Fe, 18.9-56.9 mg/kg for Pb, and 11.6-30.5 mg/kg for Zn. The results of the partitioning study showed that the residual form was the dominant fraction of the selected metals among most of the studied locations. The degree of surface sediment contamination was computed for risk assessment code (RAC), individual contamination factor (ICF), and Global contamination factor (GCF). Risk assessment code classification showed that the relative amounts of easily dissolved phase of trace metals in the sediments are in the order of Pb>Zn>Cd>Cu>Fe. The results of ICF and GCF showed that Sirt and Abu Kammashand had higher GCF than other sites indicating higher environmental risk. In terms of ICF value, a decrease order in environmental risk by trace metals was Pb>Zn>Cu>Cd>Fe. Therefore, Pb had highest risk to water body.

The truth is out there: measured, calculated and modelled benthic fluxes.

NASA Astrophysics Data System (ADS)

Pakhomova, Svetlana; Protsenko, Elizaveta

2016-04-01

In a modern Earth science there is a great importance of understanding the processes, forming the benthic fluxes as one of element sources or sinks to or from the water body, which affects the elements balance in the water system. There are several ways to assess benthic fluxes and here we try to compare the results obtained by chamber experiments, calculated from porewater distributions and simulated with model. Benthic fluxes of dissolved elements (oxygen, nitrogen species, phosphate, silicate, alkalinity, iron and manganese species) were studied in the Baltic and Black Seas from 2000 to 2005. Fluxes were measured in situ using chamber incubations (Jch) and at the same time sediment cores were collected to assess the porewater distribution at different depths to calculate diffusive fluxes (Jpw). Model study was carried out with benthic-pelagic biogeochemical model BROM (O-N-P-Si-C-S-Mn-Fe redox model). It was applied to simulate biogeochemical structure of the water column and upper sediment and to assess the vertical fluxes (Jmd). By the behaviour at the water-sediment interface all studied elements can be divided into three groups: (1) elements which benthic fluxes are determined by the concentrations gradient only (Si, Mn), (2) elements which fluxes depend on redox conditions in the bottom water (Fe, PO4, NH4), and (3) elements which fluxes are strongly connected with organic matter fate (O2, Alk, NH4). For the first group it was found that measured fluxes are always higher than calculated diffusive fluxes (1.5

Distribution and relationships of trace metals in the isopod Saduria entomon and adjacent bottom sediments in the southern Baltic.

PubMed

Góral, Marta; Szefer, Piotr; Ciesielski, Tomasz; Warzocha, Jan

2009-10-01

The concentrations of Ag, Cd, Co, Cr, Cu, Fe, Ni, Pb, Mn and Zn in Saduria entomon and adjacent bottom sediments from the southern Baltic were determined by FAAS. In order to estimate the strength of correlations between accumulated elements in these crustaceans and surficial sediment, bioaccumulation factors (BAFs) were calculated. The results of factor analysis (FA) and the Kruskal-Wallis analysis of variance (ANOVA) clearly indicate geographical differences between the concentrations of these elements. Cd, Co, Fe, Ni, Pb and Zn levels were higher in S. entomon from the Gulf of Gdańsk, whereas Cr and Mn levels were higher in the crustaceans inhabiting open Baltic waters. The concentrations of Ag and Cu were comparable in both regions. There was a tendency for metal concentrations to distinguish organisms inhabiting the muddy bottom from those living in sandy sediments. The granulometric composition of the sediment appears to influence trace metal bioavailability. The results show that S. entomon could be a valuable sentinel organism for biomonitoring heavy metal contamination in the southern Baltic.

Source discrimination of heavy metals in sediment and water of To Lich River in Hanoi City using multivariate statistical approaches.

PubMed

Thuong, Nguyen Thi; Yoneda, Minoru; Ikegami, Maiko; Takakura, Masato

2013-10-01

The concentrations of Mn, Fe, Ni, Cr, Cu, Pb, Zn, As, and Cd were determined to evaluate the level of contamination of To Lich River in Hanoi City. All metal concentrations in 0-10-cm water samples, except Mn, were lower than the maximum permitted concentration for irrigation water standard. Meanwhile, concentrations of As, Cd, and Zn in 0-30-cm sediments were likely to have adverse effects on agriculture and aquatic life. Sediment pollution assessment was undertaken using enrichment factor and geoaccumulation index (I geo). The I geo results indicated that the sediment was not polluted with Cr, Mn, Fe, and Ni, and the pollution level increased in the order of Cu < Pb < Zn < As < Cd. Meanwhile, significant enrichment was shown for Cd, As, Zn, and Pb. Cluster and principal component analyses suggest that As and Mn in sediment were derived from both lithogenic and anthropogenic sources, while Cu, Pb, Zn, Cr, Cd, and Ni originated from anthropogenic sources such as vehicular fumes for Pb and metallic discharge from industrial sources and fertilizer application for other metals.

Microanalysis (micro-XRF, micro-XANES, and micro-XRD) of a tertiary sediment using microfocused synchrotron radiation.

PubMed

Denecke, Melissa A; Somogyi, Andrea; Janssens, Koen; Simon, Rolf; Dardenne, Kathy; Noseck, Ulrich

2007-06-01

Micro-focused synchrotron radiation techniques to investigate actinide elements in geological samples are becoming an increasingly used tool in nuclear waste disposal research. In this article, results using mu-focus techniques are presented from a bore core section of a U-rich tertiary sediment collected from Ruprechtov, Czech Republic, a natural analog to nuclear waste repository scenarios in deep geological formations. Different methods are applied to obtain various, complementary information. Elemental and element chemical state distributions are obtained from micro-XRF measurements, oxidation states of As determined from micro-XANES, and the crystalline structure of selected regions are studied by means of micro-XRD. We find that preparation of the thin section created an As oxidation state artifact; it apparently changed the As valence in some regions of the sample. Results support our previously proposed hypothesis of the mechanism for U-enrichment in the sediment. AsFeS coating on framboid Fe nodules in the sediment reduced mobile groundwater-dissolved U(VI) to less-soluble U(IV), thereby immobilizing the uranium in the sediment.

Arsenic cycling in hydrocarbon plumes: secondary effects of natural attenuation

USGS Publications Warehouse

Cozzarelli, Isabelle M.; Schreiber, Madeline E.; Erickson, Melinda L.; Ziegler, Brady A.

2016-01-01

Monitored natural attenuation is widely applied as a remediation strategy at hydrocarbon spill sites. Natural attenuation relies on biodegradation of hydrocarbons coupled with reduction of electron acceptors, including solid phase ferric iron (Fe(III)). Because arsenic (As) adsorbs to Fe-hydroxides, a potential secondary effect of natural attenuation of hydrocarbons coupled with Fe(III) reduction is a release of naturally occurring As to groundwater. At a crude-oil-contaminated aquifer near Bemidji, Minnesota, anaerobic biodegradation of hydrocarbons coupled to Fe(III) reduction has been well documented. We collected groundwater samples at the site annually from 2009 to 2013 to examine if As is released to groundwater and, if so, to document relationships between As and Fe inside and outside of the dissolved hydrocarbon plume. Arsenic concentrations in groundwater in the plume reached 230 µg/L, whereas groundwater outside the plume contained less than 5 µg/L As. Combined with previous data from the Bemidji site, our results suggest that (1) naturally occurring As is associated with Fe-hydroxides present in the glacially derived aquifer sediments; (2) introduction of hydrocarbons results in reduction of Fe-hydroxides, releasing As and Fe to groundwater; (3) at the leading edge of the plume, As and Fe are removed from groundwater and retained on sediments; and (4) downgradient from the plume, patterns of As and Fe in groundwater are similar to background. We develop a conceptual model of secondary As release due to natural attenuation of hydrocarbons that can be applied to other sites where an influx of biodegradable organic carbon promotes Fe(III) reduction.

Arsenic Cycling in Hydrocarbon Plumes: Secondary Effects of Natural Attenuation.

PubMed

Cozzarelli, Isabelle M; Schreiber, Madeline E; Erickson, Melinda L; Ziegler, Brady A

2016-01-01

Monitored natural attenuation is widely applied as a remediation strategy at hydrocarbon spill sites. Natural attenuation relies on biodegradation of hydrocarbons coupled with reduction of electron acceptors, including solid phase ferric iron (Fe(III)). Because arsenic (As) adsorbs to Fe-hydroxides, a potential secondary effect of natural attenuation of hydrocarbons coupled with Fe(III) reduction is a release of naturally occurring As to groundwater. At a crude-oil-contaminated aquifer near Bemidji, Minnesota, anaerobic biodegradation of hydrocarbons coupled to Fe(III) reduction has been well documented. We collected groundwater samples at the site annually from 2009 to 2013 to examine if As is released to groundwater and, if so, to document relationships between As and Fe inside and outside of the dissolved hydrocarbon plume. Arsenic concentrations in groundwater in the plume reached 230 µg/L, whereas groundwater outside the plume contained less than 5 µg/L As. Combined with previous data from the Bemidji site, our results suggest that (1) naturally occurring As is associated with Fe-hydroxides present in the glacially derived aquifer sediments; (2) introduction of hydrocarbons results in reduction of Fe-hydroxides, releasing As and Fe to groundwater; (3) at the leading edge of the plume, As and Fe are removed from groundwater and retained on sediments; and (4) downgradient from the plume, patterns of As and Fe in groundwater are similar to background. We develop a conceptual model of secondary As release due to natural attenuation of hydrocarbons that can be applied to other sites where an influx of biodegradable organic carbon promotes Fe(III) reduction. © 2015, National Ground Water Association.

The Marine Geochemistry of Iron and Iron Isotopes

DTIC Science & Technology

2004-09-01

suspension of sediments, and hydrothermal vents. A schematic of the Fe cycle in the open ocean is shown in Figure 1.1. Fe concentrations are highest near...than 2% of their coastal values 100 km from the California continental margin (JOHNSON et al., 1997). Hydrothermal input of Fe is believed to be...important only near its sources (mostly in the deep ocean) because most of the Fe from hydrothermal vents precipitates near the vents and ridge axis (DE

A model for Cryogenian iron formation

NASA Astrophysics Data System (ADS)

Cox, Grant M.; Halverson, Galen P.; Poirier, André; Le Heron, Daniel; Strauss, Justin V.; Stevenson, Ross

2016-01-01

The Neoproterozoic Tatonduk (Alaska) and Holowilena (South Australia) iron formations share many characteristics including their broadly coeval (Sturtian) ages, intimate association with glaciogenic sediments, and mineralogy. We show that these shared characteristics extend to their neodymium (εNd) and iron isotope (δ56Fe) systematics. In both regions δ56Fe values display a distinct up-section trend to isotopically heavier values, while εNd values are primitive and similar to non-ferruginous mudstones within these successions. The δ56Fe profiles are consistent with oxidation of ferruginous waters during marine transgression, and the εNd values imply that much of this iron was sourced from the leaching of continental margin sediments largely derived from continental flood basalts. Rare earth element data indicate a secondary hydrothermal source for this iron.

Pathways and supply of dissolved iron in the Amundsen Sea (Antarctica)

NASA Astrophysics Data System (ADS)

St-Laurent, P.; Yager, P. L.; Sherrell, R. M.; Stammerjohn, S. E.; Dinniman, M. S.

2017-09-01

Numerous coastal polynyas fringe the Antarctic continent and strongly influence the productivity of Antarctic shelf systems. Of the 46 Antarctic coastal polynyas documented in a recent study, the Amundsen Sea Polynya (ASP) stands out as having the highest net primary production per unit area. Incubation experiments suggest that this productivity is partly controlled by the availability of dissolved iron (dFe). As a first step toward understanding the iron supply of the ASP, we introduce four plausible sources of dFe and simulate their steady spatial distribution using conservative numerical tracers. The modeled distributions replicate important features from observations including dFe maxima at the bottom of deep troughs and enhanced concentrations near the ice shelf fronts. A perturbation experiment with an idealized drawdown mimicking summertime biological uptake and subsequent resupply suggests that glacial meltwater and sediment-derived dFe are the main contributors to the prebloom dFe inventory in the top 100 m of the ASP. The sediment-derived dFe depends strongly on the buoyancy-driven overturning circulation associated with the melting ice shelves (the "meltwater pump") to add dFe to the upper 300 m of the water column. The results support the view that ice shelf melting plays an important direct and indirect role in the dFe supply and delivery to polynyas such as the ASP.

A hydrogen-oxidizing, Fe(III)-reducing microorganism from the Great Bay estuary, New Hampshire

USGS Publications Warehouse

Caccavo, F.; Blakemore, R.P.; Lovley, D.R.

1992-01-01

A dissimilatory Fe(III)- and Mn(IV)-reducing bacterium was isolated from bottom sediments of the Great Bay estuary, New Hampshire. The isolate was a facultatively anaerobic gram-negative rod which did not appear to fit into any previously described genus. It was temporarily designated strain BrY. BrY grew anaerobically in a defined medium with hydrogen or lactate as the electron donor and Fe(III) as the electron acceptor. BrY required citrate, fumarate, or malate as a carbon source for growth on H2 and Fe(III). With Fe(III) as the sole electron acceptor, BrY metabolized hydrogen to a minimum threshold at least 60-fold lower than the threshold reported for pure cultures of sulfate reducers. This finding supports the hypothesis that when Fe(III) is available, Fe(III) reducers can outcompete sulfate reducers for electron donors. Lactate was incompletely oxidized to acetate and carbon dioxide with Fe(III) as the electron acceptor. Lactate oxidation was also coupled to the reduction of Mn(IV), U(VI), fumarate, thiosulfate, or trimethylamine n-oxide under anaerobic conditions. BrY provides a model for how enzymatic metal reduction by respiratory metal-reducing microorganisms has the potential to contribute to the mobilization of iron and trace metals and to the immobilization of uranium in sediments of Great Bay Estuary.

Mössbauer spectroscopic study of the test well (DND) located in Jaisalmer Basin of Rajasthan, India

NASA Astrophysics Data System (ADS)

Ganwani, Girish; Meena, Samay Singh; Ram, Sahi; Bhatia, Beena; Tripathi, R. P.

2018-05-01

The Jaisalmer basin represents mainly the westerly dipping flank of Indus shelf. The palynological and geochemical studies have predicted good quality of hydrocarbons in this basin. The cretaceous and Jurassic sediments are believed to contain source rock in this basin. In present preliminary study, Mössbauer spectroscopic investigation has been done on sedimentary samples collected from different depths of upper cretaceous sedimentary sequence of well DND-1 drilled in Jaisalmer basin. The iron is found mainly in carbonate and clay. The relatively small presence of Fe2+ in comparison to Fe3+ in clay is an indication of poor reducing environment in sediments, which can be attributed to poor maturity of source rocks in upper cretaceous sediments of this basin.

Recovery of Humic-Reducing Bacteria from a Diversity of Environments

PubMed Central

Coates, John D.; Ellis, Debra J.; Blunt-Harris, Elizabeth L.; Gaw, Catherine V.; Roden, Eric E.; Lovley, Derek R.

1998-01-01

To evaluate which microorganisms might be responsible for microbial reduction of humic substances in sedimentary environments, humic-reducing bacteria were isolated from a variety of sediment types. These included lake sediments, pristine and contaminated wetland sediments, and marine sediments. In each of the sediment types, all of the humic reducers recovered with acetate as the electron donor and the humic substance analog, 2,6-anthraquinone disulfonate (AQDS), as the electron acceptor were members of the family Geobacteraceae. This was true whether the AQDS-reducing bacteria were enriched prior to isolation on solid media or were recovered from the highest positive dilutions of sediments in liquid media. All of the isolates tested not only conserved energy to support growth from acetate oxidation coupled to AQDS reduction but also could oxidize acetate with highly purified soil humic acids as the sole electron acceptor. All of the isolates tested were also able to grow with Fe(III) serving as the sole electron acceptor. This is consistent with previous studies that have suggested that the capacity for Fe(III) reduction is a common feature of all members of the Geobacteraceae. These studies demonstrate that the potential for microbial humic substance reduction can be found in a wide variety of sediment types and suggest that Geobacteraceae species might be important humic-reducing organisms in sediments. PMID:9546186

Changes in Fe Oxidation Rate in Hydrothermal Plumes as a Potential Driver of Enhanced Hydrothermal Input to Near-Ridge Sediments During Glacial Terminations

NASA Astrophysics Data System (ADS)

Cullen, J. T.; Coogan, L. A.

2017-12-01

Recent studies have hypothesized that changes in sea level due to glacial-interglacial cycles lead to changes in the rate of melt addition to the crust at mid-ocean ridges with globally significant consequences. Arguably the most compelling evidence for this comes from increases in the hydrothermal component in near-ridge sediments during glacial-interglacial transitions. Here we explore the hypothesis that changes in ocean bottom water [O2] and pH across glacial-interglacial transitions would lead to changes in the rate of Fe oxidation in hydrothermal plumes. A simple model shows that a several fold increase in the rate of Fe oxidation is expected at glacial-interglacial transitions. Uncertainty in bottom water chemistry and the relationship between oxidation and sedimentation rates prevent direct comparison of the model and data. However, it appears that the null hypothesis of invariant hydrothermal vent fluxes into ocean bottom water that changed in O2 content and pH across these transitions cannot currently be discounted.

Biogeochemistry of Mariana Islands coastal sediments: terrestrial influence on /gd13, Ash, CaCO3, Al, Fe, Si and P

NASA Astrophysics Data System (ADS)

Matson, Ernest A.

1989-01-01

Stable C isotope ratios (δ13C-PDB), percentages of organic matter, and HCl insoluble ash and soluble carbonates, extractable Fe, Al, Si and P were used to determine the distribution and accumulation of terrestrial material in reef-flat moats and lagoons of two high islands (Guam and Saipan) in the western tropical Pacific. Carbonate sediments of a reef-flat moat infiltrated by seepage of aquifer waters (but without surface runoff) were depleted in both P (by 38%) and 13C (by 41%) and enriched in Si (by 100%) relative to offshore lagoon sediments. Iron and ash accumulated in depositional regimes regardless of the occurrence of runoff but was depleted from coarse-grained carbonates in turbulent regimes. Aluminum (>ca. 10 to 20 μmol g-1), Fe (>ca. 1 to 3 μmol g-1) and ash (>0.5%) indicated terrigenous influence which was corroborated by depletions in both 13C and P. Low-salinity geochemical segregation, natural biochemical accumulation, as well as long-shore currents and eddies help sequester these materials nearshore.

Assessing the potential ecological risk of Co, Cr, Cu, Fe and Zn in the sediments of Hooghly-Matla estuarine system, India.

PubMed

Ghosh, Somdeep; Bakshi, Madhurima; Kumar, Alok; Ramanathan, A L; Biswas, Jayanta Kumar; Bhattacharyya, Subarna; Chaudhuri, Punarbasu; Shaheen, Sabry M; Rinklebe, Jörg

2018-05-09

Hooghly-Matla estuarine system along with the Sundarbans mangroves forms one of the most diverse and vulnerable ecosystems in the world. We have investigated the distribution of Co, Cr, Cu, Fe and Zn along with sediment properties at six locations [Shamshernagar (S1), Kumirmari (S2 and S3), Petuaghat (S4), Tapoban (S5) and Chemaguri (S6)] in the Hooghly estuary and reclaimed islands of the Sundarbans for assessing the degree of contamination and potential ecological risks. Enrichment factor values (0.9-21.6) show enrichment of Co, Cu and Zn in the intertidal sediments considering all sampling locations and depth profiles. Geo-accumulation index values irrespective of sampling locations and depth revealed that Co and Cu are under class II and class III level indicating a moderate contamination of sediments. The pollution load index was higher than unity (1.6-2.1), and Co and Cu were the major contributors to the sediment pollution followed by Zn, Cr and Fe with the minimum values at S1 and the maximum values at S5. The sediments of the Hooghly-Matla estuarine region (S4, S5 and S6) showed considerable ecological risks, when compared with effect range low/effect range median and threshold effect level/probable effect level values. The variation in the distribution of the studied elements may be due to variation in discharge pattern and exposure to industrial effluent and domestic sewage, storm water and agricultural run-off and fluvial dynamics of the region. The study illuminates the necessity for the proper management of vulnerable coastal estuarine ecosystem by stringent pollution control measures along with regular monitoring and checking program.

Transfer kinetics of phosphorus (P) in macrophyte rhizosphere and phytoremoval performance for lake sediments using DGT technique.

PubMed

Wu, Zhihao; Wang, Shengrui; Luo, Jun

2018-05-15

DGT (diffusive gradients in thin films) technique and DIFS (DGT induced fluxes in sediment) model are firstly designed for macrophyte-rhizobox system and in-situ macrophytes in Lake Erhai. Dynamics of phosphorus (P) transfer in Zizania latifolia (ZL) and Myriophyllum verticiilatur (MV) rhizosphere is revealed and phytoremediation performance for P in sediment is evaluated. Dynamic transfer process of P at DGT/sediment interface includes (i) diffusion flux and concentration gradients at DGT(root)/porewater interface leading to porewater concentration (C 0 ) depletion and (ii) P desorption from labile P pool in sediment solid to resupply C 0 depletion. Fe-redox controlled P release from Fe-bound P (BD-P2) and then NH 4 Cl-P1 in rhizosphere sediment resupplies porewater depletion due to DGT (root) sink. K d (labile P pool size in solid phase), r (resupply ratio) and kinetic exchange (Tc and k -1 ) lead to change characters of DIFS curves of (1) r against deployment time and (2) C solu (dissolved concentration) against distance at 24 h. They include two opposite types of "fast" and "slow" rate of resupplies. Sediment properties and DIFS parameters control P diffusion and resupply in rhizosphere sediment. Phytoremoval ability for sediment P in lake is estimated to be 23.4 (ZL) or 15.0 t a -1 (MV) by "DGT-flux" method. Copyright © 2018 Elsevier B.V. All rights reserved.

Geomicrobiology of Fe-rich crusts in Lake Superior sediment

NASA Astrophysics Data System (ADS)

Dittrich, M.; Monreau, L.; Quazi, S.; Raoof, B.; Chesnyuk, A.; Katsev, S.; Fulthorpe, R.

2012-04-01

The limnological puzzles of Lake Superior are increasingly attracting scientists, and very little is known about the sediments and their associated microflora. The sediments are organic poor (less than 5%C) and the lake is deep oligotrophic, with water temperatures at the bottom around 3C. Previous studies reveal Fe-rich layers in the sediments at multiple loccations around the lake. The origin and mechanisms of formation of this layer remain unknown. In this study we investigated geochemical and microbiological processes that may lead to the formation of a two cm thick iron layer about 10 cm below the sediment surface. Sediment cores from two stations (EM, 230m water depth and ED, 310m water depth) in the East Basin were used. We monitored oxygen and pH depth profiles with microsensors, porewater and sediment solid matter were analyzed for nutrient and metal contents. Furthermore, phosphorus and iron sequantial extractions of sediment cores have been perfomed. The total cell count was determined using DAPI epifluoresence microscopy. DNA was extracted from the sediment samples and 16S ribosonal RNA amplicons were analyzed with denaturing gradient gel electrophoresis (DGGE). For a more in depth analysis, DNA samples from 8-10 cm and 10-12 cm were sent to the Research and Testing Lab (Texas) for pyrosequencing of 16S rRNA gene amplicons amplified using barcoded universal primers 27f-519r. The scanning electron microscope (SEM) images from the iron layer 10-12cm show filaments that were encrusted with spheres ca. 20 nm in diameter. SEM observations of thin sections also indicate the presence of very fine particles showing various morphologies. Analyses of the deposit material by SEM and energy dispersive X-ray spectroscopy (EDS) indicate that bacteria cells surfaces served as nucleation surfaces for Fe-oxide formation. EDS line-scans through bacterial cells covered with precipitates reveal phosphorus and carbon peaks at interface between cell surface and Fe-particles. The cluster analysis performed on the DGGE separation of ribosomal RNA gene fragments revealed that the two iron layers were not highly similar to each other. We obtained a total of 26,062 16S rRNA gene sequence reads from the two iron layers and the layers directly above them, which were clustered into operational taxonomic units sharing 80% similarity or more. 64-70% of these clusters could not be classified below the phylum level. While the 8-10 cm sediment layers were dominated (46.5% of reads) by relatives of Paenisporosarcina, the iron layers contained far fewer gram positive organisms, far more proteobacteria, and an a high proportion of Nitrospira species which show relatively high similarity to organisms found in an iron II rich seep.

Multielement chemical and statistical analyses from a uranium hydrogeochemical and stream-sediment survey in and near the Elkhorn Mountains, Jefferson County, Montana; Part II, Stream sediments

USGS Publications Warehouse

Suits, V.J.; Wenrich, K.J.

1982-01-01

Fifty-two stream-sediment samples, collected from an area south of Helena, Jefferson County, Montana, were sieved into two size fractions (50 ppm for the fine fraction) were encountered in samples from the Warm Springs Creek drainage area, along Prickly Pear Creek near Welmer and Golconda Creeks and along Muskrat Creek. All groups showed a significant correlation at the 99 percent confidence level (r between 0.73 and 0.77) between U and Th. Uranium was found to correlate significantly only with Th (as mentioned above) and with -Ni in the fine fraction of the volcanics group. U correlates significantly with -Al2O3, Ba, organic C, -K2O, -Sr and Y in both size fractions for the Boulder batholith. Correlations between U and each of several elements differ for the fine and coarse fractions of the Boulder batholith group, suggesting that the U distribution in these stream sediments is in large part controlled by grain size. Correlations were found between U and CaO, Cr, Fe203, -Na2O, Sc, -SiO2, TiO2, Yb and Zr in the coarse fraction but not in the fine fraction. U correlates weakly (to the 90% confidence level, crc<.37) with -Co and -Cu in the fine but not the coarse fraction. These results are compared to a previous study in the northern Absaroka mountains. Correlation coefficients between all other elements determined from these samples are also shown in Tables 12 to 15.

Influence of humic acid concentration on nTiO2 attachment to quartz sand and Fe-coated quartz sand

NASA Astrophysics Data System (ADS)

Cheng, T.; Wu, Y.

2016-12-01

The transport of nano-scale or micro-scale titanium dioxide particles (nTiO2) in subsurface environments are strongly influenced by nTiO2 attachment to sediment grains. The objective of this study is to investigate the role of humic acid (HA) in the attachment of nTiO2 to sand at low HA concentrations that are relevant to typical groundwater conditions, so that mechanisms that control nTiO2 immobilization and transport in groundwater can be elucidated. nTiO2 may carry either positive or negative charges in natural water, therefore, environmental factors such as pH, humic substances, and Fe oxyhydroxide coatings on sediment grains, which are known to control the transport of negatively-charged colloids, may influence nTiO2 in different manners. Attachment of nTiO2 to quartz sand and Fe oxyhydroxide coated quartz sand are experimentally measured under a range of HA concentrations at fixed pH. Experimental results show that at pH 5, negatively-charged HA strongly adsorbs to positively-charged nTiO2 and Fe oxyhydroxide, which, at low HA concentrations, partially neutralizes the positive charges on nTiO2 and Fe oxyhydroxide, and therefore decreases the repulsive electrostatic forces between the surfaces, resulting in relatively high nTiO2 attachment. At high HA concentrations, adsorbed HA reverses the surface charges of nTiO2 and Fe oxyhydroxide, and makes nTiO2 and Fe oxyhydroxide strongly negatively charged, resulting in low nTiO2 attachment. At pH 9, HA, nTiO2, and Fe oxyhydroxide are all negatively charged, and HA adsorption is low and does not have a strong impact on the attachment of nTiO2. This study demonstrates that the changes in surface charges of nTiO2 and Fe oxyhydroxide coating caused by HA adsorption could be a key factor that controls the attachment of nTiO2 to sediment grains.

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

Kaus, Noor Haida Mohd., E-mail: noorhaida@usm.my; Collins, A. M.; Mann, S.

In this paper, we present a facile method for production stable aqueous dispersion of ferrocene (FO) nanoparticles. Ferrocene compounds were employed to achieve stable nanodispersions, stabilized with three different biopolymers namely, alginate, CM-dextran and chitosan. The nanoparticles produce are spherical, less than 10 nm in mean diameter and highly stable without any sedimentation. Fourier infrared transform (FTIR) and X-ray diffraction (XRD) studies confirmed the purity of ferrocene nanoparticles there is no modifications occur during the preparation route. FTIR spectra results were consistent with the presence of absorption band of cyclopentadienyl ring (C{sub 5}H{sub 5}{sup −} ion) which assigned to ν(C-C)more » vibrations (1409 cm-1), δ(C-H) stretching at 1001 cm{sup −1} and π(C-H) vibrations at 812 cm{sup −1}. Furthermore, all functional group for biopolymers such as CO from carboxyl group of CM-dextran and sodium alginate appears at 1712 cm{sup −1} and 1709 cm{sup −1} respectively, indicating there are steric repulsion interactions for particles stabilization. Powder X-ray diffraction patterns of sedimented samples of the biopolymers-stabilized ferrocene (FO) showed all reflections which were indexed respectively to the (−110), (001), (−201), (−111), (200), (−211), (210), (120) and (111) according to the monoclinic phase ferrocene. This confirmed that the products obtained were of high purity of Fe and EDAX analysis also suggests that the presence of the Fe element in the colloidal dispersion.« less

The Contribution of Opal-Associated Phosphorus to Bioavailable Phosphorus in Surface and Core Sediments in the East China Sea

NASA Astrophysics Data System (ADS)

Li, Huanxin; He, Huijun; Yang, Shifeng; Liu, Yanli; Che, Hong; Li, Mujian; Zhang, Jing

2018-06-01

To improve the burial flux calculations of bioavailable phosphorus (P) and study opal-associated P (Opal-P) in the East China Sea (ECS), surface and core sediments were collected in the Changjiang Estuary (CE) and the south of the Cheju Island. In this study, sedimentary P was operationally divided into seven different forms using modified sedimentary extraction (SEDEX) technique: LSor-P (exchangeable or loosely sorbed P), Fe-P (easily reducible or reactive ferric Fe-bound P), CFA-P (authigenic carbonate fluorapatite and biogenic apatite and CaCO3-bound P), Detr-P (detrital apatite), Org-P (organic P), Opal-P and Ref-P (refractory P). The data revealed that the concentrations of the seven different P forms rank as Detr-P > CFA-P > Org-P > Ref-P > Opal-P > Fe-P > LSor-P in surface sediments and CFA-P > Detr-P > Org-P > Ref-P > Fe-P > Opal-P > LSor-P in core sediments. The distributions of the total phosphorus (TP), TIP, CFA-P, Detr-P are similar and decrease from the CE to the south of the Cheju Island. Meanwhile, Org-P and Opal-P exhibit different distribution trends; this may be affected by the grain size and TOM. The concentrations of potentially bioavailable P are 9.6-13.0 μmol g-1 and 10.0-13.6 μmol g-1, representing 61%-70% and 41%-64% of the TP in surface and core sediments, respectively. The concentrations of Opal-P are 0.6-2.3 μmol g-1 and 0.6-1.4 μmol g-1 in surface and core sediments, accounting for 5.3%-19.8% and 4.2%-10.6% of bioavailable P, respectively. The total burial fluxes of Opal-P and bioavailable P are 1.4×109 mol yr-1 and 1.1×1010 mol yr-1 in the ECS, respectively. Opal-P represents about 12.7% of potentially bioavailable P, which should be recognized when studying P cycling in marine ecosystems.

Geochemistry of ferromanganese nodules from DOMES site a, Northern Equatorial Pacific: Multiple diagenetic metal sources in the deep sea

USGS Publications Warehouse

Calvert, S.E.; Piper, D.Z.

1984-01-01

The major and minor element composition of ferromanganese nodules from DOMES Site A has been determined by X-ray fluorescence methods. Three phases appear to control the bulk compositions: Mn and Fe oxyhydroxides and aluminosilicates. Relatively wide compositional variations are evident throughout the area. Nodules with high Mn/Fe ratios, high Cu, Mg, Mo, Ni and Zn concentrations and high todorokite/??-MnO2 ratios have granular surface textures and are confined to an east-west trending depression with thin Quaternary sediment cover. Nodules with low Mn/Fe ratios, high concentrations of As, Ca, Ce, Co, La, P, Sr, Ti, V, Y and Zr and low todorokite/??-MnO2 ratios have smooth surfaces and are confined to shallower areas with relatively thick Quaternary sediment to the north and south of the depression. All nodules in the area have compositions which are influenced by diagenesis, but those with the most marked diagenetic signature (high Mn/Fe and Cu/Ni ratios, low Ce/La ratios and more todorokite) are found in areas of very slow or non-existent sedimentation; many of these nodules are actually in contact with outcropping Tertiary sediment. This paradox may be resolved by postulating, by analogy with some shallow-water occurrences, that the nodules accrete from bottom waters which have enhanced particulate and dissolved metal contents derived from diagenetic reaction in areas remote from the site of nodule formation. The metals are supplied in a bottom flow (probably Antarctic Bottom Water) which also erodes, or prevents modern sedimentation in, the depression. Nodules on the flanks of the depression are not evidently affected by this flow and derive at least pan of their constituent metals from diagenetic reaction in the underlying Quaternary sediment. Apparently, abyssal diagenetic nodules can have an immediate and a remote diagenetic metal source. Metal fluxes derived from pore water dissolved metal gradients may not be relevant to particular accreting nodules if a significant fraction of their metals is derived from outside the area in which they form. ?? 1984.

The effect of an oil drilling operation on the trace metal concentrations in offshore bottom sediments of the Campos Basin oil field, SE Brazil.

PubMed

Rezende, C E; Lacerda, L D; Ovalle, A R C; Souza, C M M; Gobo, A A R; Santos, D O

2002-07-01

The concentrations of Al, Fe, Mn, Zn, Cu, Pb, Ni, Cr, Ba, V, Sn and As in offshore bottom sediments from the Bacia de Campos oil field, SE Brazil, were measured at the beginning and at 7 months after completion of the drilling operation. Concentrations of Al, Fe, Ba, Cr, Ni and Zn were significantly higher closer to the drilling site compared to stations far from the site. Average concentrations of Al, Cu, and in particular of Ni, were significantly higher at the end of the drilling operation than at the beginning. Comparison between drilling area sediments with control sediments of the continental platform, however, showed no significant difference in trace metal concentrations. Under the operation conditions of this drilling event, the results show that while changes in some trace metal concentrations do occur during drilling operations, they are not significantly large to be distinguished from natural variability of the local background concentrations.

Assessment of heavy metals in sediments of the Don Hoi Lot area in the Mae Klong estuary, Thailand.

PubMed

Pengthamkeerati, Patthra; Kornkanitnan, Narumol; Sawangarreruks, Suchat; Wanichacheva, Nantanit; Wainiphithapong, Chantana; Sananwai, Nipawan

2013-01-01

The status and seasonal variation of heavy metals in surface sediment were investigated at Don Hoi Lot, located in the Mae Klong estuary, Thailand. Results revealed that all the measured heavy metals, except Zn, in the sediments had lower concentrations than in other nearby estuaries. Only Zn may be of concern for potential negative effects on estuarine biota in the study area. With the exception of Fe, all the studied heavy metals showed seasonal variation, but the patterns were diverse. Organic matter and the clay fraction in sediments were good sinks for heavy metals, excluding Zn, while Fe and Mn were good catchers. Principal component analysis suggested that Zn might have different origins and/or mechanisms of transport, accumulation and circulation, compared with the other heavy metals studied. A better understanding of sources and the behavior of Zn would enhance the efficiency of the estuary management plan in this study area.

Influence of variable chemical conditions on EDTA-enhanced transport of metal ions in mildly acidic groundwater

USGS Publications Warehouse

Kent, D.B.; Davis, J.A.; Joye, J.L.; Curtis, G.P.

2008-01-01

Adsorption of Ni and Pb on aquifer sediments from Cape Cod, Massachusetts, USA increased with increasing pH and metal-ion concentration. Adsorption could be described quantitatively using a semi-mechanistic surface complexation model (SCM), in which adsorption is described using chemical reactions between metal ions and adsorption sites. Equilibrium reactive transport simulations incorporating the SCMs, formation of metal-ion-EDTA complexes, and either Fe(III)-oxyhydroxide solubility or Zn desorption from sediments identified important factors responsible for trends observed during transport experiments conducted with EDTA complexes of Ni, Zn, and Pb in the Cape Cod aquifer. Dissociation of Pb-EDTA by Fe(III) is more favorable than Ni-EDTA because of differences in Ni- and Pb-adsorption to the sediments. Dissociation of Ni-EDTA becomes more favorable with decreasing Ni-EDTA concentration and decreasing pH. In contrast to Ni, Pb-EDTA can be dissociated by Zn desorbed from the aquifer sediments. Variability in adsorbed Zn concentrations has a large impact on Pb-EDTA dissociation.

Geochemical assessment of heavy metals pollution in surface sediments of Vellar and Coleroon estuaries, southeast coast of India.

PubMed

Nethaji, S; Kalaivanan, R; Arya Viswam; Jayaprakash, M

2017-02-15

Surface sediments were collected from Vellar and Coleroon estuaries for determine sediment texture, calcium carbonate, organic matter and heavy metals. Pollution indices such as pollution load index (PLI), contamination factor (CF), enrichment factor (EF) and geo-accumulation index (I geo ) were done for this study to know the level of heavy metals pollution in the estuarine ecosystem. Pearson correlation matrix and factor were used to assess the relationship and source of heavy metals in the estuarine sediments. The results of PLI values reveal that the study area was polluted by all the heavy metals. The calculated values of CF and I geo followed the decreasing order Cu>Ni>Pb>Co>Cr>Zn>Mn>Fe and illustrate that Cu, Ni and Pb are contaminated due to anthropogenic sources in both estuaries. Correlation and factor analysis suggest that FeMn oxyhydroxides, organic matter and fine particles are responsible for high concentration of heavy metals. Copyright © 2016 Elsevier Ltd. All rights reserved.

Dissolved and particulate trace metal micronutrients under the McMurdo Sound seasonal sea ice: basal sea ice communities as a capacitor for iron

PubMed Central

Noble, Abigail E.; Moran, Dawn M.; Allen, Andrew E.; Saito, Mak A.

2013-01-01

Dissolved and particulate metal concentrations are reported from three sites beneath and at the base of the McMurdo Sound seasonal sea ice in the Ross Sea of Antarctica. This dataset provided insight into Co and Mn biogeochemistry, supporting a previous hypothesis for water column mixing occurring faster than scavenging. Three observations support this: first, Mn-containing particles with Mn/Al ratios in excess of the sediment were present in the water column, implying the presence of bacterial Mn-oxidation processes. Second, dissolved and labile Co were uniform with depth beneath the sea ice after the winter season. Third, dissolved Co:PO3−4 ratios were consistent with previously observed Ross Sea stoichiometry, implying that over-winter scavenging was slow relative to mixing. Abundant dissolved Fe and Mn were consistent with a winter reserve concept, and particulate Al, Fe, Mn, and Co covaried, implying that these metals behaved similarly. Elevated particulate metals were observed in proximity to the nearby Islands, with particulate Fe/Al ratios similar to that of nearby sediment, consistent with a sediment resuspension source. Dissolved and particulate metals were elevated at the shallowest depths (particularly Fe) with elevated particulate P/Al and Fe/Al ratios in excess of sediments, demonstrating a sea ice biomass source. The sea ice biomass was extremely dense (chl a >9500 μg/L) and contained high abundances of particulate metals with elevated metal/Al ratios. A hypothesis for seasonal accumulation of bioactive metals at the base of the McMurdo Sound sea ice by the basal algal community is presented, analogous to a capacitor that accumulates iron during the spring and early summer. The release and transport of particulate metals accumulated at the base of the sea ice by sloughing is discussed as a potentially important mechanism in providing iron nutrition during polynya phytoplankton bloom formation and could be examined in future oceanographic expeditions. PMID:24790953

Porewater dynamics of silver, lead and copper in coastal sediments and implications for benthic metal fluxes

USGS Publications Warehouse

Kalnejais, Linda H.; Martin, W. R.; Bothner, Michael H.

2015-01-01

To determine the conditions that lead to a diffusive release of dissolved metals from coastal sediments, porewater profiles of Ag, Cu, and Pb have been collected over seven years at two contrasting coastal sites in Massachusetts, USA. The Hingham Bay (HB) site is a contaminated location in Boston Harbor, while the Massachusetts Bay (MB) site is 11 km offshore and less impacted. At both sites, the biogeochemical cycles include scavenging by Fe-oxyhydroxides and release of dissolved metals when Fe-oxyhydroxides are reduced. Important differences in the metal cycles at the two sites, however, result from different redox conditions. Porewater sulfide and seasonal variation in redox zone depth is observed at HB, but not at MB. In summer, as the conditions become more reducing at HB, trace metals are precipitated as sulfides and are no longer associated with Fe-oxyhydroxides. Sulfide precipitation close to the sediment–water interface limits the trace metal flux in summer and autumn at HB, while in winter, oxidation of the sulfide phases drives high benthic fluxes of Cu and Ag, as oxic conditions return. The annual diffusive flux of Cu at HB is found to be significant and contributes to the higher than expected water column Cu concentrations observed in Boston Harbor. At MB, due to the lower sulfide concentrations, the association of trace metals with Fe-oxyhydroxides occurs throughout the year, leading to more stable fluxes. A surface enrichment of solid phase trace metals was found at MB and is attributed to the persistent scavenging by Fe-oxyhydroxides. This process is important, particularly at sites that are less reducing, because it maintains elevated metal concentrations at the surface despite the effects of bioturbation and sediment accumulation, and because it may increase the persistence of metal contamination in surface sediments.

Dissolved and particulate trace metal micronutrients under the McMurdo Sound seasonal sea ice: basal sea ice communities as a capacitor for iron

NASA Astrophysics Data System (ADS)

Noble, Abigail; Saito, Mak; Moran, Dawn; Allen, Andrew

2013-10-01

Dissolved and particulate metal concentrations are reported from three sites beneath and at the base of the McMurdo Sound seasonal sea ice in the Ross Sea of Antarctica. This dataset provided insight into Co and Mn biogeochemistry, supporting a previous hypothesis for water column mixing occurring faster than scavenging. Three observations support this: first, Mn-containing particles with Mn/Al ratios in excess of the sediment were present in the water column, implying the presence of bacterial Mn-oxidation processes. Second, dissolved and labile Co were uniform with depth beneath the sea ice after the winter season. Third, dissolved Co:PO43- ratios were consistent with previously observed Ross Sea stoichiometry, implying that over-winter scavenging was slow relative to mixing. Abundant dissolved Fe and Mn were consistent with a winter reserve concept, and particulate Al, Fe, Mn, and Co covaried, implying that these metals behaved similarly. Elevated particulate metals were observed in proximity to the nearby Islands, with particulate Fe/Al ratios similar to that of nearby sediment, consistent with a sediment resuspension source. Dissolved and particulate metals were elevated at the shallowest depths (particularly Fe) with elevated particulate P/Al and Fe/Al ratios in excess of sediments, demonstrating a sea ice biomass source. The sea ice biomass was extremely dense (chl a >9500 μg/L) and contained high abundances of particulate metals with elevated metal/Al ratios. A hypothesis for seasonal accumulation of bioactive metals at the base of the McMurdo Sound sea ice by the basal algal community is presented, analogous to a capacitor that accumulates iron during the spring and early summer. The release and transport of particulate metals accumulated at the base of the sea ice by sloughing is discussed as a potentially important mechanism in providing iron nutrition during polynya phytoplankton bloom formation and could be examined in future oceanographic expeditions.

Treatment of arsenic in acid wastewater and river sediment by Fe@Fe2O3 nanobunches: The effect of environmental conditions and reaction mechanism.

PubMed

Tang, Lin; Feng, Haopeng; Tang, Jing; Zeng, Guangming; Deng, Yaocheng; Wang, Jiajia; Liu, Yani; Zhou, Yaoyu

2017-06-15

High concentration of arsenic in acid wastewater and polluted river sediment caused by metallurgical industry has presented a great environmental challenge for decades. Nanoscale zero valent iron (nZVI) can detoxify arsenic-bearing wastewater and groundwater, but the low adsorption capacity and rapid passivation restrict its large-scale application. This study proposed a highly efficient arsenic treatment nanotechnology, using the core-shell Fe@Fe 2 O 3 nanobunches (NBZI) for removal of arsenic in acid wastewater with cyclic stability and transformation of arsenic speciation in sediment. The adsorption capacity of As(III) by NBZI was 60 times as high as that of nanoscale zero valent iron (nZVI) at neutral pH. Characterization of the prepared materials after reaction revealed that the contents of As(III) and As(V) were 65% and 35% under aerobic conditions, respectively, which is the evidence of oxidation included in the reaction process apart from adsorption and co-precipitation. The presence of oxygen was proved to improve the adsorption ability of the prepared NBZI towards As(III) with the removal efficiency increasing from 68% to 92%. In order to further enhance the performance of NBZI-2 in the absence of oxygen, a new Fenton-Like system of NBZI/H 2 O 2 to remove arsenic under the anoxic condition was also proposed. Furthermore, the removal efficiency of arsenic in acid wastewater remained to be 78% after 9 times of cycling. Meanwhile, most of the mobile fraction of arsenic in river sediment was transformed into residues after NBZI treatment for 20 days. The reaction mechanism between NBZI and arsenic was discussed in detail at last, indicating great potential of NBZI for the treatment of arsenic in wastewater and sediment. Copyright © 2017 Elsevier Ltd. All rights reserved.

Platinum group elements in stream sediments of mining zones: The Hex River (Bushveld Igneous Complex, South Africa)

NASA Astrophysics Data System (ADS)

Almécija, Clara; Cobelo-García, Antonio; Wepener, Victor; Prego, Ricardo

2017-05-01

Assessment of the environmental impact of platinum group elements (PGE) and other trace elements from mining activities is essential to prevent potential environmental risks. This study evaluates the concentrations of PGE in stream sediments of the Hex River, which drains the mining area of the Bushveld Igneous Complex (South Africa), at four sampling points. Major, minor and trace elements (Fe, Ca, Al, Mg, Mn, V, Cr, Zn, Cu, As, Co, Ni, Cd, and Pb) were analyzed by FAAS and ETAAS in suspended particulate matter and different sediment fractions (<63, 63-500 and 500-2000 μm), and Pt, Pd, Rh, and Ir were measured by ICP-MS after removal of interfering elements (cation exchange resin 50W-DOWEX-X8). Procedures were blank-corrected and accuracy checked using reference materials. Nickel, Cr, Pt, Pd, Rh and Ir show concentrations 3-, 13- 18-, 28-, 48- and 44- fold the typical upper continental crust levels, respectively, although lower than concentrations reported for the parent rocks. The highest concentrations were observed closer to the mining area, decreasing with distance and in the <63 μm fraction, probably derived from atmospheric deposition and surface runoff of PGE-rich particles released from mining activities. Thus, mining activities are causing some disturbance of the surface PGE geochemical cycle, increasing the presence of PGE in the fine fraction of river sediments. We propose that indicators such as airborne particulate matter, and soil and river sediment quality, should be added to the protocols for evaluating the sustainability of mining activities.

Iron and manganese oxide mineralization in the Pacific

USGS Publications Warehouse

Hein, J.R.; Koschinsky, A.; Halbach, P.; Manheim, F.T.; Bau, M.; Kang, J.-K.; Lubick, N.

1997-01-01

Iron, manganese, and iron-manganese deposits occur in nearly all geomorphologic and tectonic environments in the ocean basins and form by one or more of four processes: (1) hydrogenetic precipitation from cold ambient seawater, (2) precipitation from hydrothermal fluids, (3) precipitation from sediment pore waters that have been modified from bottom water compositions by diagenetic reactions in the sediment column and (4) replacement of rocks and sediment. Iron and manganese deposits occur in five forms: nodules, crusts, cements, mounds and sediment-hosted stratabound layers. Seafloor oxides show a wide range of compositions from nearly pure iron to nearly pure manganese end members. Fe/Mn ratios vary from about 24 000 (up to 58% elemental Fe) for hydrothermal seamount ironstones to about 0.001 (up to 52% Mn) for hydrothermal stratabound manganese oxides from active volcanic arcs. Hydrogenetic Fe-Mn crusts that occur on most seamounts in the ocean basins have a mean Fe/Mn ratio of 0.7 for open-ocean seamount crusts and 1.2 for continental margin seamount crusts. Fe-Mn nodules of potential economic interest from the Clarion-Clipperton Zone have a mean Fe/Mn ratio of 0.3, whereas the mean ratio for nodules from elsewhere in the Pacific is about 0.7. Crusts are enriched in Co, Ni and Pt and nodules in Cu and Ni, and both have significant concentrations of Pb, Zn, Ba, Mo, V and other elements. In contrast, hydrothermal deposits commonly contain only minor trace metal contents, although there are many exceptions, for example, with Ni contents up to 0.66%, Cr to 1.2%, and Zn to 1.4%. Chondrite-normalized REE patterns generally show a positive Ce anomaly and abundant ΣREEs for hydrogenetic and mixed hydrogenetic-diagenetic deposits, whereas the Ce anomaly is negative for hydrothermal deposits and ΣREE contents are low. However, the Ce anomaly in crusts may vary from strongly positive in East Pacific crusts to slightly negative in West Pacific crusts, which may reflect the redox conditions of seawater. The concentration of elements in hydrogenetic Fe-Mn crusts depends on a wide variety of water column and crust surface characteristics, whereas concentration of elements in hydrothermal oxide deposits depends of the intensity of leaching, rock types leached, and precipitation of sulphides at depth in the hydrothermal system.

Bioaccumulation of metals in fish species from water and sediments in macrotidal Ennore creek, Chennai, SE coast of India: A metropolitan city effect.

PubMed

Jayaprakash, M; Kumar, R Senthil; Giridharan, L; Sujitha, S B; Sarkar, S K; Jonathan, M P

2015-10-01

Accumulation of trace metals (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn, Cd) were investigated in water, sediment (n=20) along with six fish of diverse feeding guilds (Sillago sihama, Liza parsia, Etroplus suratensis, Oreochromis mossambicus, Arius parkii and Gerres oyena) from the Ennore creek, northern part of Chennai metropolitan megacity, southeast coast of India. Dissolved trace metals (DTMs) in surface water samples and total trace metals (TTMs) in surface sediments (top 0-10cm) indicate that concentration pattern of metals was higher in the discharge point of the river/channels entering the main creek. The maximum mean values of DTMs exhibited the following decreasing order (expressed in µg/L): Fe (1698)>Mn (24)>Zn (14.50)>Pb (13.89)>Ni (6.73)>Cu (3.53)>Co (3.04)>Cr (2.01) whereas the trend is somewhat different in sediments (µgg(-1)): Fe (4300)>Mn (640)>Cr (383)>Zn (155)>Cu (102)>Ni (35)>Pb (32)>Cd (0.51) are mainly due to the industrial complexes right on the banks of the river/channels. Species-specific heterogeneous patterns of tissue metal loads were apparent and the overall metal enrichment exhibited the following decreasing order (expressed in µgg(-1)): Cu (7.33)>Fe (6.53)>Zn (4.91)>Cr (1.67)>Pb (1.33)>Ni (0.44)>Mn (0.43)>Co (0.36)>Cd (0.11). This indicates that metals are absorbed onto the different organs, which is also endorsed by the calculated values of bioaccumulation factor (BAFs) (avg. muscle 117, gill 126, liver 123, intestine 118) in fishes. The high calculated biota sediment accumulation factor (BSAF) (0.437) for the species Arius parkii is considered to be a potential bioindicator in this region. The enrichment of trace metals is also supported by the association of metals in water, sediments and different body organs (muscle, gill, liver, intestine) of fish samples. Comparative studies with other coastal regions indicate considerable enrichment of DTMs & TTMs in sediments as well as in various organs of fish samples. Holistic spatial, temporal monitoring and comprehensive regional strategies are required to prevent health risks and ensure nutritional safety conditions. Copyright © 2015 Elsevier Inc. All rights reserved.

Mechanisms for Fe(III) oxide reduction in sedimentary environments

USGS Publications Warehouse

Nevin, Kelly P.; Lovely, Derek R.

2002-01-01

Although it was previously considered that Fe(III)-reducing microorganisms must come into direct contact with Fe(III) oxides in order to reduce them, recent studies have suggested that electron-shuttling compounds and/or Fe(III) chelators, either naturally present or produced by the Fe(III)-reducing microorganisms themselves, may alleviate the need for the Fe(III) reducers to establish direct contact with Fe(III) oxides. Studies with Shewanella alga strain BrY and Fe(III) oxides sequestered within microporous beads demonstrated for the first time that this organism releases a compound(s) that permits electron transfer to Fe(III) oxides which the organism cannot directly contact. Furthermore, as much as 450 w M dissolved Fe(III) was detected in cultures of S. alga growing in Fe(III) oxide medium, suggesting that this organism releases compounds that can solublize Fe(III) from Fe(III) oxide. These results contrast with previous studies, which demonstrated that Geobacter metallireducens does not produce electron-shuttles or Fe(III) chelators. Some freshwater aquatic sediments and groundwaters contained compounds, which could act as electron shuttles by accepting electrons from G. metallireducens and then transferring the electrons to Fe(III). However, other samples lacked significant electron-shuttling capacity. Spectroscopic studies indicated that the electron-shuttling capacity of the waters was not only associated with the presence of humic substances, but water extracts of walnut, oak, and maple leaves contained electron-shuttling compounds did not appear to be humic substances. Porewater from a freshwater aquatic sediment and groundwater from a petroleum-contaminated aquifer contained dissolved Fe(III) (4-16 w M), suggesting that soluble Fe(III) may be available as an electron acceptor in some sedimentary environments. These results demonstrate that in order to accurately model the mechanisms for Fe(III) reduction in sedimentary environments it will be necessary to have information on the concentrations of electron-shuttling compounds and possibly Fe(III) ligands. Furthermore, as it is now apparent that different genera of Fe(III)-reducing microorganisms may reduce Fe(III) via different mechanisms, knowledge of which Fe(III)-reducing microorganisms predominate in the environment of interest is essential in order to model this process appropriately.

Manganese oxide shuttling in pre-GOE oceans - evidence from molybdenum and iron isotopes

NASA Astrophysics Data System (ADS)

Kurzweil, Florian; Wille, Martin; Gantert, Niklas; Beukes, Nicolas J.; Schoenberg, Ronny

2016-10-01

The local occurrence of oxygen-rich shallow marine water environments has been suggested to significantly predate atmospheric oxygenation, which occurred during the Great Oxidation Event (GOE) ca. 2.4 billion years ago. However, the potential influence of such 'oxygen oases' on the mobility, distribution and isotopic composition of redox sensitive elements remains poorly understood. Here, we provide new molybdenum and iron isotopic data from shallow marine carbonate and silicate iron formations of the Koegas Subgroup, South Africa, that confirm local ocean redox stratification prior to the GOE. Mn concentrations correlate negatively with both δ98 Mo and δ56 Fe values, which highlights the substantial role of particulate manganese for the cycling of Mo and Fe in the Paleoproterozoic oceans. Based on these trends we propose that pore water molybdate was recharged (1) by the diffusional transport of seawater molybdate with high δ98 Mo and (2) by the re-liberation of adsorbed molybdate with low δ98 Mo during Mn oxide dissolution within the sediment. The relative contribution of isotopically light Mo is highest close to a Mn chemocline, where the flux of Mn oxides is largest, causing the negative correlation of Mn concentrations and δ98 Mo values in the Koegas sediments. The negative correlation between δ56 Fe values and Mn concentrations is likely related to Fe isotope fractionation during Fe(II) oxidation by Mn oxides, resulting in lower δ56 Fe values in the uppermost water column close to a Mn chemocline. We argue that the preservation of these signals within Paleoproterozoic sediments implies the existence of vertically extended chemoclines with a smoother gradient, probably as a result of low atmospheric oxygen concentrations. Furthermore, we suggest that abiotic oxidation of Fe(II) by a Mn oxide particle shuttle might have promoted the deposition of the Koegas iron formations.

Biogeochemical Insights into B-Vitamins in the Coastal Marine Sediments of San Pedro Basin, CA

NASA Astrophysics Data System (ADS)

Monteverde, D.; Berelson, W.; Baronas, J. J.; Sanudo-Wilhelmy, S. A.

2015-12-01

Coastal marine sediments support a high abundance of mircoorganisms which play key roles in the cycling of nutrients, trace metals, and carbon, yet little is known about many of the cofactors essential for their growth, such as the B-vitamins. The suite of B-vitamins (B1, B2, B6, B7, B12) are essential across all domains of life for both primary and secondary metabolism. Therefore, studying sediment concentrations of B-vitamins can provide a biochemical link between microbial processes and sediment geochemistry. Here we present B-vitamin pore water concentrations from suboxic sediment cores collected in September 2014 from San Pedro Basin, a silled, low oxygen, ~900 m deep coastal basin in the California Borderlands. We compare the B-vitamin concentrations (measured via LCMS) to a set of geochemical profiles including dissolved Fe (65-160 μM), dissolved Mn (30-300 nM), TCO2, solid phase organic carbon, and δ13C. Our results show high concentrations (0.8-3nM) of biotin (B7), commonly used for CO2 fixation as a cofactor in carboxylase enzymes. Thiamin (B1) concentrations were elevated (20-700nM), consistent with previous pore water measurements showing sediments could be a source of B1 to the ocean. Cobalamin (B12), a cofactor required for methyl transfers in methanogens, was also detected in pore waters (~4-40pM). The flavins (riboflavin [B2] and flavin mononucleotide[FMN]), molecules utilized in external electron transfer, showed a distinct increase with depth (10-90nM). Interestingly, the flavin profiles showed an inverse trend to dissolved Fe (Fe decreases with depth) providing a potential link to culture experiments which have shown extracellular flavin release to be a common trait in some metal reducers. As some of the first B-vitamin measurements made in marine sediments, these results illustrate the complex interaction between the microbial community and surrounding geochemical environment and provide exciting avenues for future research.

Adsorption And Simultaneous Dechlorination Of PCBs On GAC/Fe/Pd: Mechanistic Aspects And Reactive Capping Barrier Concept

EPA Science Inventory

There are many concerns and challenges in current remediation strategies for sediments contaminated with polychlorinated biphenyls (PCBs). Our efforts have been geared toward the development of granular activated carbon (GAC) impregnated with reactive iron/palladium (Fe/Pd) bime...

Sedimentary regimes at Potter Cove, King George Island, maritime Antarctica - from source to sink

NASA Astrophysics Data System (ADS)

Monien, Donata; Monien, Patrick; Brünjes, Robert M.; Widmer, Tatjana; Schnetger, Bernhard; Brumsack, Hans-Jürgen

2013-04-01

Increased particle run-off due to recently retreated ice masses along the Antarctic margins may play an important role in fertilizing the high-nutrient-low-chlorophyll regions of the Southern Ocean. At Potter Cove, King George Island, maritime Antarctica, small melt water streams at the south-eastern shoreline (Potter Peninsula) discharge up to 1,500 mg L-1 (av. 110 mg L-1) of suspended particle matter (SPM) per day into the coastal water body during the summer seasons. Apart from potential light limitation of plankton growth by the suspension load, the particle run-off affects benthic feeders, possibly changes the depositional regime and the preservation of chemical proxies in the outlet zones, and exports trace elements offshore. In Potter Cove's water column, the average particle size is low, and extreme turbidity events are restricted to the upper five to seven meters. High particle loads are often associated with low salinities, most probably induced by increased onshore precipitation. Sediment traps installed in the inner and outer cove at 5 and 20 m water depth suggest mass accumulation rates of 0.83 and 0.58 g cm-2 yr-1, and 0.13 and 0.11 g cm-2 yr-1 (considering 183 days of sedimentation), respectively. 210Pb measurements of short sediment cores reveal recent sediment accumulation rates of approximately 0.1 to 0.6 g cm-2 yr-1. The SPM sampled in the melt water streams and plumes is chemically different to surface sediments deposited in Potter Cove. Chemical characteristics suggest a significant impact of particle sorting: SPM and outer cove sediments are more clayey, whereas inner cove sediments contain more heavy minerals. Generally, sediment deposits in Potter Cove exhibit coarser grain sizes and are mainly derived from Barton Peninsula (northern shoreline), whereas the SPM consists of more fine-grained material originating from Potter Peninsula eluviations. Sequential leaching of the SPM by ascorbic acid showed that approximately 0.5 to 2% of the total iron (5.9 wt.% Fe) is easily dissolvable, which in turn can be translated into an additional load of approximately 5 to 21 mmol L-1 dissolved Fe2+. In consequence, the results of our three-summer study highlight that the major part of the particle load from the melt water streams are exported to the Southern Ocean rather than being deposited near shore in Potter Cove. These exported particles are rich in easily leachable Fe acting as a natural fertilization to the Fe-limited Southern Ocean.

Solid-Phase Fe Speciation along the Vertical Redox Gradients in Floodplains using XAS and Mössbauer Spectroscopies.

PubMed

Chen, Chunmei; Kukkadapu, Ravi K; Lazareva, Olesya; Sparks, Donald L

2017-07-18

Properties of Fe minerals are poorly understood in natural soils and sediments with variable redox conditions. In this study, we combined 57 Fe Mössbauer and Fe K-edge X-ray absorption spectroscopic (XAS) techniques to assess solid-phase Fe speciation along the vertical redox gradients of floodplains, which exhibited a succession of oxic, anoxic, and suboxic-oxic zones with increasing depth along the vertical profiles. The incised stream channel is bounded on the east by a narrow floodplain and a steep hillslope, and on the west by a broad floodplain. In the eastern floodplain, the anoxic conditions at the intermediate horizon (55-80 cm) coincided with lower Fe(III)-oxides (particularly ferrihydrite), in concurrence with a greater reduction of phyllosilicates(PS)-Fe(III) to PS-Fe(II), relative to the oxic near-surface and sandy gravel layers. In addition, the anoxic conditions in the eastern floodplain coincided with increased crystallinity of goethite, relative to the oxic layers. In the most reduced intermediate sediments at 80-120 cm of the western floodplain, no Fe(III)-oxides were detected, concurrent with the greatest PS-Fe(III) reduction (PS-Fe(II)/Fe(III) ratio ≈ 1.2 (Mössbauer) or 0.8 (XAS)). In both oxic near-surface horizon and oxic-suboxic gravel aquifers beneath the soil horizons, Fe(III)-oxides were mainly present as ferrihydrite with a much less amount of goethite, which preferentially occurred as nanogoethite or Al/Si-substituted goethite. Ferrihydrite with varying crystallinity or impurities such as organic matter, Al or Si, persisted under suboxic-oxic conditions in the floodplain. This study indicates that vertical redox gradients exert a major control on the quantity and speciation of Fe(III) oxides as well as the oxidation state of structural Fe in PS, which could significantly affect nutrient cycling and carbon (de)stabilization.

The influence of groundwater chemistry on arsenic concentrations and speciation in a quartz sand and gravel aquifer

USGS Publications Warehouse

Kent, D.B.; Fox, P.M.

2004-01-01

We examined the chemical reactions influencing dissolved concentrations, speciation, and transport of naturally occurring arsenic (As) in a shallow, sand and gravel aquifer with distinct geochemical zones resulting from land disposal of dilute sewage effluent. The principal geochemical zones were: (1) the uncontaminated zone above the sewage plume [350 ??M dissolved oxygen (DO), pH 5.9]; (2) the suboxic zone (5 ??M DO, pH 6.2, elevated concentrations of sewage-derived phosphate and nitrate); and (3) the anoxic zone [dissolved iron(II) 100-300 ??M, pH 6.5-6.9, elevated concentrations of sewage-derived phosphate]. Sediments are comprised of greater than 90% quartz but the surfaces of quartz and other mineral grains are coated with nanometer-size iron (Fe) and aluminum (Al) oxides and/or silicates, which control the adsorption properties of the sediments. Uncontaminated groundwater with added phosphate (620 ??M) was pumped into the uncontaminated zone while samples were collected 0.3 m above the injection point. Concentrations of As(V) increased from below detection (0.005 ??M) to a maximum of 0.07 ??M during breakthrough of phosphate at the sampling port; As(III) concentrations remained below detection. These results are consistent with the hypothesis that naturally occurring As(V) adsorbed to constituents of the coatings on grain surfaces was desorbed by phosphate in the injected groundwater. Also consistent with this hypothesis, vertical profiles of groundwater chemistry measured prior to the tracer test showed that dissolved As(V) concentrations increased along with dissolved phosphate from below detection in the uncontaminated zone to approximately 0.07 and 70 ??M, respectively, in the suboxic zone. Concentrations of As(III) were below detection in both zones. The anoxic zone had approximately 0.07 ??M As(V) but also had As(III) concentrations of 0.07-0.14 ??M, suggesting that release of As bound to sediment grains occurred by desorption by phosphate, reductive dissolution of Fe oxides, and reduction of As(V) to As(III), which adsorbs only weakly to the Fe-oxide-depleted material in the coatings. Results of reductive extractions of the sediments suggest that As associated with the coatings was relatively uniformly distributed at approximately 1 nmol/g of sediment (equivalent to 0.075 ppm As) and comprised 20%-50% of the total As in the sediments, determined from oxidative extractions. Quartz sand aquifers provide high-quality drinking water but can become contaminated when naturally occurring arsenic bound to Fe and Al oxides or silicates on sediment surfaces is released by desorption and dissolution of Fe oxides in response to changing chemical conditions. ?? 2004 American Institute of Physics.

Uranium fate in wetland mesocosms: Effects of plants at two ...

EPA Pesticide Factsheets

Small-scale continuous flow wetland mesocosms (~0.8 L) were used to evaluate how plant roots under different iron loadings affect uranium (U) mobility. When significant concentrations of ferrous iron (Fe) were present at circumneutral pH values, U concentrations in root exposed sediments were an order of magnitude greater than concentrations in root excluded sediments. Micro X-ray absorption near-edge structure (µ-XANES) spectroscopy indicated that U was associated with the plant roots primarily as U(VI) or U(V), with limited evidence of U(IV). Micro X-ray fluorescence (µ-XRF) of plant roots suggested that for high iron loading at circumneutral pH, U was co-located with Fe, perhaps co-precipitated with root Fe plaques, while for low iron loading at a pH of ~4 the correlation between U and Fe was not significant, consistent with previous observations of U associated with organic matter. Quantitative PCR analyses indicated that the root exposed sediments also contained elevated numbers of Geobacter spp., which are likely associated with enhanced iron cycling, but may also reduce mobile U(VI) to less mobile U(IV) species. There are significant uncertainties regarding the environmental fate of uranium (U) and efforts to minimize U exposures require understanding of its mobility in environmental systems. Much research has focused on sequestering U as solids within groundwater aquifers, where localized risks can be controlled.1 Subsurface sequestration limits t

Attenuation of dissolved metals in neutral mine drainage in the Zambian Copperbelt.

PubMed

Sracek, Ondra; Filip, Jan; Mihaljevič, Martin; Kříbek, Bohdan; Majer, Vladimír; Veselovský, František

2011-01-01

Behaviour of metals like Cu and Co was studied in nearly neutral (pH ≥ 6.4) mine drainage seepage in a stream downgradient of a tailing dam at Chambishi site in the Copperbelt of Zambia. They are attenuated by precipitation of ferruginous ochres that incorporate significant quantities of metals. Using chemical analysis, X-ray powder diffraction and Mössbauer spectroscopy, we show that the ochres are composed mostly of amorphous ferric hydroxide. Close to the seepage face, the total Fe content of ochres increases due to precipitation of amorphous ferric hydroxide, but total Fe in sediment decreases further downstream. The stream then flows through wetland (dambo) where the remaining fraction of metals is removed. During rainy periods, increased flow rate may result in re-suspension of ochres, increasing thus the mobility of metals. Major ions like sulphate are conservative at the start of the dry period (May), but gypsum may probably precipitate later at the end of the dry period. Sequential extractions of bulk sediments indicate that Mn behaves differently to Fe, with a trend of increasing Mn with distance from the tailing dam. There is much more Fe than Mn in residual (Aqua Regia) fraction, indicating that amorphous ferric hydroxides are transformed to more crystalline phases deeper in sediment. Environmental impact of mine drainage is relatively limited due to its neutral character.

Trimethylamine stimulated and dissolved organic matter inhibited methane production in sediment from the Poyang Lake, China.

PubMed

Wang, Jiajia; Liu, Chunying; Gong, Xiaofeng; Liu, Yuanmu; Chen, Chunli

2016-10-01

Methane (CH4) emitted from wetlands contributes significantly to the greenhouse effect. The Poyang Lake, the largest freshwater lake in China, is fed by five rivers and connects to the Yangtze River. The area of the lake fluctuates dramatically between drawdown and flood periods with large areas of wetlands. In order to understand the CH4 production capacity and factors that influence CH4 production in the wetland, a static closed chamber combined with a gas chromatograph technique was used to investigate the influence of substrates and electron acceptors on methanogenesis. The results showed that CH4 production capacity of sediments from the Poyang Lake was [Formula: see text] and it was stimulated by trimethylamine (TMA) to a great extent. Incubation temperature played a vital role on CH4 production in sediments and the optimum temperature for methanogenesis was 35°C. Minimum CH4 production capacity occurred with the addition of FeCl3, and the inhibitory effects of electron acceptors decreased in the sequence: FeCl3 > MnO2 > DOM > Fe2O3. In this study, DOM was demonstrated as one of the inhibitors to methanogenesis and TMA was the main substrate of methanogens in the sediments of the Poyang Lake whose pH value is 7.83.

Influence of Coprecipitated Organic Matter on Fe2+(aq) -Catalyzed Transformation of Ferrihydrite: Implications for Carbon Dynamics

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

Chen, Chunmei; Kukkadapu, Ravi K.; Sparks, Donald L.

2015-08-10

The poorly crystalline Fe(III) hydroxide ferrihydrite is an important sink for organic matter (OM), nutrients and contaminants in soils and sediments. Aqueous Fe(II) is known to catalyze the transformation of ferrihydrite to more crystalline and thus less reactive phases. While coprecipitation of OM with ferrihydrite could be a common process in many environments due to changes in pH, redox potential or ionic strength, little is known about the impacts of coprecipitated OM on Fe(II)-catalyzed ferrihydrite transformation and its consequences for C dynamics. Accordingly, we explored the extent and pathways of Fe(II)-induced transformation of OM-ferrihydrite coprecipitates and subsequent C mobility. Mössbauermore » spectroscopic results indicated that the coprecipitated OM within ferrihydrite weakened the inter-particle magnetic interactions and decreased average particle size. The coprecipitated OM resulted in diminished Fe(II)-induced ferrihydrite transformation and thus preservation of ferrihydrite. The secondary mineral profiles upon Fe(II) reaction with ferrihydrite were a function of OM content and Fe(II) concentration. At low Fe(II) levels, OM completely inhibited goethite formation and stimulated lepidocrocite formation. At high Fe(II) levels, whereas goethite was formed in the presence of OM, OM reduced the amount of goethite and magnetite formation and increased the formation of lepidocrcocite. The solid-phase C content remained unchanged after reaction, while OM desorpability by H2PO4- was enhanced following reaction of OM-ferrihydrites with aqueous Fe(II). These findings provide insights into the reactivity of natural ferrihydrite containing OM in soils and sediments and the subsequent impact on mineral evolution and C dynamics.« less

Effects of nitrate on the stability of uranium in a bioreduced region of the subsurface.

PubMed

Wu, Wei-Min; Carley, Jack; Green, Stefan J; Luo, Jian; Kelly, Shelly D; Van Nostrand, Joy; Lowe, Kenneth; Mehlhorn, Tonia; Carroll, Sue; Boonchayanant, Benjaporn; Löfller, Frank E; Watson, David; Kemner, Kenneth M; Zhou, Jizhong; Kitanidis, Peter K; Kostka, Joel E; Jardine, Philip M; Criddle, Craig S

2010-07-01

The effects of nitrate on the stability of reduced, immobilized uranium were evaluated in field experiments at a U.S. Department of Energy site in Oak Ridge, TN. Nitrate (2.0 mM) was injected into a reduced region of the subsurface containing high levels of previously immobilized U(IV). The nitrate was reduced to nitrite, ammonium, and nitrogen gas; sulfide levels decreased; and Fe(II) levels increased then deceased. Uranium remobilization occurred concomitant with nitrite formation, suggesting nitrate-dependent, iron-accelerated oxidation of U(IV). Bromide tracer results indicated changes in subsurface flowpaths likely due to gas formation and/or precipitate. Desorption-adsorption of uranium by the iron-rich sediment impacted uranium mobilization and sequestration. After rereduction of the subsurface through ethanol additions, background groundwater containing high levels of nitrate was allowed to enter the reduced test zone. Aqueous uranium concentrations increased then decreased. Clone library analyses of sediment samples revealed the presence of denitrifying bacteria that can oxidize elemental sulfur, H(2)S, Fe(II), and U(IV) (e.g., Thiobacillus spp.), and a decrease in relative abundance of bacteria that can reduce Fe(III) and sulfate. XANES analyses of sediment samples confirmed changes in uranium oxidation state. Addition of ethanol restored reduced conditions and triggered a short-term increase in Fe(II) and aqueous uranium, likely due to reductive dissolution of Fe(III) oxides and release of sorbed U(VI). After two months of intermittent ethanol addition, sulfide levels increased, and aqueous uranium concentrations gradually decreased to <0.1 microM.

Assessment of heavy metal contamination in the sediments of Nansihu Lake Catchment, China.

PubMed

Liu, Enfeng; Shen, Ji; Yang, Liyuan; Zhang, Enlou; Meng, Xianghua; Wang, Jianjun

2010-02-01

At present, anthropogenic contribution of heavy metals far exceeds natural input in some aquatic sediment, but the proportions are difficult to differentiate due to the changes in sediment characters. In this paper, the metal (Al, Fe, K, Mg, Ca, Cr, Cu, Ni, and Zn) concentrations, grain size, and total organic carbon (TOC) content in the surface and core sediments of Nansihu Lake Catchment (the open lake and six inflow rivers) were determined. The chemical speciations of the metals (Al, Fe, Cr, Cu, Ni, and Zn) in the surface sediments were also analyzed. Approaches of factor analysis, normalized enrichment factor (EF) and the new non-residual fractions enrichment factor (K(NRF)) were used to differentiate the sources of the metals in the sediments, from detrital clastic debris or anthropogenic input, and to quantify the anthropogenic contamination. The results indicate that natural processes were more dominant in concentrating the metals in the surface and core sediments of the open lake. High concentration of Ca and deficiency of other metals in the upper layers of the sediment core were attributed to the input of carbonate minerals in the catchment with increasing human activities since 1980s. High TOC content magnified the deficiency of the metals. Nevertheless, the EF and K(NRF) both reveal moderate to significant anthropogenic contamination of Cr, Cu, Ni, and Zn in the surface sediments of Laoyun River and the estuary and Cr in the surface sediments of Baima River. The proportion of non-residual fractions (acid soluble, reducible, and oxidizable fractions) of Cr, Cu, Ni, and Zn in the contaminated sediments increased to 37-99% from the background levels less than 30%.

The impact of suspended oyster farming on nitrogen cycling and nitrous oxide production in a sub-tropical Australian estuary

NASA Astrophysics Data System (ADS)

Erler, Dirk V.; Welsh, David T.; Bennet, William W.; Meziane, Tarik; Hubas, Cédric; Nizzoli, Daniele; Ferguson, Angus J. P.

2017-06-01

In this study we quantified nitrate (NO3-) reduction (denitrification, anammox and DNRA) and N2O production in sediments and epibiont communities associated with Sydney Rock Oyster (Saccostrea glomerata) farming. In sediments beneath an active suspended oyster farm, DNRA accounted for 98% of NO3- reduction with rates of up to 169 ± 45 μmol N m-2 h-1. Much of this DNRA was fuelled by NO3- derived from nitrification. Reference sediments had significantly lower DNRA rates of 83.8 ± 28.2 μmol N m-2 h-1, however this constituted 96% of the sites total NO3- reduction. Fatty acid analysis showed that sediment organic matter was more labile in the oyster impacted sediments, facilitating subtle shifts in sediment oxygen demand which increased the Fe2+ availability with respect to the reference sediments. The difference in DNRA rate between the sites was attributed to autotrophic oxidation of soluble Fe2+ in sediments underlying the oyster cultures. DNRA was absent in the oyster shell epibiont communities and rates of anammox and denitrification were lower than in the sediments. Production of NH4+ from the oysters and their associated epibionts was larger than DNRA and reached a rate of 206.2 μmol N m-2 h-1. Nitrous oxide production rates were generally low compared to other aquaculture systems and the net flux of N2O for the combined oyster cultivation system (i.e. sediments plus epibionts) was negative, i.e. there was N2O consumption in the sediments beneath the oysters. Overall, subtropical suspended oyster farming systems favour inorganic N retention over N loss.

Geochemical, mineralogical and microbiological characteristics of sediment from a naturally reduced zone in a uranium-contaminated aquifer

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

Campbell, Kate M.; Kukkadapu, Ravi K.; Qafoku, Nikolla

2012-05-23

Localized zones or lenses of naturally reduced sediments have the potential to play a significant role in the fate and transport of redox-sensitive metals and metalloids in aquifers. To assess the mineralogy, microbiology, and redox processes that occur in these zones, we examined several cores from a region of naturally occurring reducing conditions in a uranium-contaminated aquifer (Rifle, CO). Sediment samples from a transect of cores ranging from oxic/suboxic Rifle aquifer sediment to naturally reduced sediment were analyzed for uranium and iron content, oxidation state, and mineralogy, reduced sulfur phases, and solid phase organic carbon content using a suite ofmore » analytical and spectroscopic techniques on bulk sediment and size fractions. Solid-phase uranium concentrations were higher in the naturally reduced zone, with a high proportion of the uranium present as reduced U(IV). The sediments were also elevated in reduced sulfur phases and Fe(II), indicating it is very likely that U(VI), Fe(III), and sulfate reduction occurred or is occurring in the sediment. The microbial community was assessed using lipid- and DNA-based techniques, and statistical redundancy analysis was performed to determine correlations between the microbial community and the geochemistry. Increased concentration of solid phase organic carbon and biomass in the naturally reduced sediment suggests that natural bioreduction is stimulated by a zone of increased organic carbon concentration associated with fine-grained material and lower permeability to groundwater flow. Characterization of the naturally bioreduced sediment provides an understanding of the natural processes that occur in the sediment under reducing conditions and how they may impact natural attenuation of radionuclides and other redox sensitive materials. Results also suggest the importance of recalcitrant organic carbon for maintaining reducing conditions and uranium immobilization.« less

The use of nuclear muprobe techniques to study the chemistry of lacustrine sediments and particles

NASA Astrophysics Data System (ADS)

Grime, G. W.; Davison, W.

1993-05-01

The Oxford SPM has been used in two novel studies of lake chemistry: (a) The distribution of dissolved iron in sediment pore waters close to the sediment/water interface has been measured using the novel technique of diffusive equilibration in a thin film (DET). In this technique, which has a spatial resolution of < 1 mm, much less than that of competing techniques (1 cm), a thin layer of polyacrylamide gel is inserted into the sediment and after the rapid equilibration with the pore water, the gel is dried and fixed. The distribution of trace elements can then be measured using mubeam PIXE. Preliminary results have shown for the first time a subsurface maximum of Fe consistent with current theories of Fe dynamics. This paper presents some results obtained using the technique and discusses the limits on resolution and sensitivity, (b) Individual suspended lake particles (predominantly iron oxides and sulphides) have been analysed using point mubeam RBS and PIXE. Of particular interest in this study is the oxidation state of iron rich particles, so RBS with a 1 μm beam was used to determine the Fe: O stoichiometry of single particles. The particles were filtered from a depth of 14 m in Esthwaite Water in the English Lake District and handled in anoxic conditions until evacuation in the SPM sample chamber. Two distinct compositions of iron oxide were determined in clusters of about 5 μm diameter. Analysis by PIXE revealed that FeS was uniformly distributed in the particulate material and that it also contained elevated levels of Cu and Zn. This study was the first to demonstrate directly that discrete clusters of iron oxides are present in black particulate material which is commonly considered to comprise iron sulphides.

Adsorption of multi-heavy metals Zn and Cu onto surficial sediments: modeling and adsorption capacity analysis.

PubMed

Li, Shanshan; Zhang, Chen; Wang, Meng; Li, Yu

2014-01-01

Improved multiple regression adsorption models (IMRAMs) was developed to estimate the adsorption capacity of the components [Fe oxides (Fe), Mn oxides (Mn), organic materials (OMs), residuals] in surficial sediments for multi-heavy metal Zn and Cu. IMRAM is an improved version over MRAM, which introduces a computer program in the model developing process. As MRAM, Zn(Cu) IMRAM, and Cu(Zn) IMRAM again confirmed that there is significant interaction effects that control the adsorption of compounded Zn and Cu, which was neglected by additional adsorption model. The verification experiment shows that the relative deviation of the IMRAMs is less than 13%. It is revealed by the IMRAMs that Mn, which has the greatest adsorption capability for compounded Zn and Cu (54.889 and 161.180 mg/l, respectively), follows by interference adsorption capacity of Fe/Mn (-1.072 and -24.591 mg/l respectively). Zn and Cu influence each other through different mechanisms. When Zn is the adsorbate, compounded Cu mainly affects the adsorption capacities of Fe/Mn and Fe/Mn/OMs; while when Cu is the adsorbate, compounded Zn mainly exerts its effect on Mn, Fe/Mn, and Mn/OMs. It also shows that the compounded Zn or Cu weakened the interference adsorption of Fe/Mn, and meanwhile, strengthened the interference adsorption of Mn/OMs.

Biochemical Mechanisms and Microorganisms Involved in Anaerobic Testosterone Metabolism in Estuarine Sediments

PubMed Central

Shih, Chao-Jen; Chen, Yi-Lung; Wang, Chia-Hsiang; Wei, Sean T.-S.; Lin, I-Ting; Ismail, Wael A.; Chiang, Yin-Ru

2017-01-01

Current knowledge on the biochemical mechanisms underlying microbial steroid metabolism in anaerobic ecosystems is extremely limited. Sulfate, nitrate, and iron [Fe (III)] are common electron acceptors for anaerobes in estuarine sediments. Here, we investigated anaerobic testosterone metabolism in anaerobic sediments collected from the estuary of Tamsui River, Taiwan. The anaerobic sediment samples were spiked with testosterone (1 mM) and individual electron acceptors (10 mM), including nitrate, Fe3+, and sulfate. The analysis of androgen metabolites indicated that testosterone biodegradation under denitrifying conditions proceeds through the 2,3-seco pathway, whereas testosterone biodegradation under iron-reducing conditions may proceed through an unidentified alternative pathway. Metagenomic analysis and PCR-based functional assays suggested that Thauera spp. were the major testosterone degraders in estuarine sediment samples incubated with testosterone and nitrate. Thauera sp. strain GDN1, a testosterone-degrading betaproteobacterium, was isolated from the denitrifying sediment sample. This strain tolerates a broad range of salinity (0–30 ppt). Although testosterone biodegradation did not occur under sulfate-reducing conditions, we observed the anaerobic biotransformation of testosterone to estrogens in some testosterone-spiked sediment samples. This is unprecedented since biotransformation of androgens to estrogens is known to occur only under oxic conditions. Our metagenomic analysis suggested that Clostridium spp. might play a role in this anaerobic biotransformation. These results expand our understanding of microbial metabolism of steroids under strictly anoxic conditions. PMID:28848528

Geochemistry of molybdenum in some stream sediments and waters

NASA Astrophysics Data System (ADS)

Kaback, Dawn S.; Runnells, Donald D.

1980-03-01

Elevated concentrations of Mo are present in both the waters and sediments of Tenmile Creek, downstream from the large Mo deposit at Climax. Colorado. Concentrations of Mo reach a maximum of 10mg/1 in the water and 384μ/g in the (-) 80 mesh fraction of the sediment. The Mo anomaly extends for more than 80 km downstream from Climax, and results from the mining and milling at Climax. Background Mo concentrations in the nearby mountainous area are < 10μg/l (water) and < 5μg/g (sediment). Immediately below three small unmined Mo-rich orebodies elsewhere in Colorado < 3μg/l Mo are present in the waters and 20-30μg/g Mo in the fine fraction of the sediments. The Mo in the sediment of Tenmile Creek is chiefly adsorbed on coatings of amorphous Fe oxyhydroxide. and is similar to its form below two small, unmined Mo deposits. Mining has not changed the character of the chemical processes responsible for Mo dispersion from the Climax site. A modified version of the WATEQF computer program ( PLUMMERet al., 1976) predicts that Tenmile Creek is undersaturated with respect to ferrimolybdite. molybdenite, powellite, and ilsemannite. The Mo in the stream water occurs as the molybdate ion which can be adsorbed on amorphous Fe oxyhydroxides. These predictions are supported by the absence of Mo minerals in the sediment of Tenmile Creek.

Diversity of the Sediment Microbial Community in the Aha Watershed (Southwest China) in Response to Acid Mine Drainage Pollution Gradients

PubMed Central

Sun, Weimin; Sun, Min; Dong, Yiran; Ning, Zengping; Xiao, Enzong; Tang, Song; Li, Jiwei

2015-01-01

Located in southwest China, the Aha watershed is continually contaminated by acid mine drainage (AMD) produced from upstream abandoned coal mines. The watershed is fed by creeks with elevated concentrations of aqueous Fe (total Fe > 1 g/liter) and SO42− (>6 g/liter). AMD contamination gradually decreases throughout downstream rivers and reservoirs, creating an AMD pollution gradient which has led to a suite of biogeochemical processes along the watershed. In this study, sediment samples were collected along the AMD pollution sites for geochemical and microbial community analyses. High-throughput sequencing found various bacteria associated with microbial Fe and S cycling within the watershed and AMD-impacted creek. A large proportion of Fe- and S-metabolizing bacteria were detected in this watershed. The dominant Fe- and S-metabolizing bacteria were identified as microorganisms belonging to the genera Metallibacterium, Aciditerrimonas, Halomonas, Shewanella, Ferrovum, Alicyclobacillus, and Syntrophobacter. Among them, Halomonas, Aciditerrimonas, Metallibacterium, and Shewanella have previously only rarely been detected in AMD-contaminated environments. In addition, the microbial community structures changed along the watershed with different magnitudes of AMD pollution. Moreover, the canonical correspondence analysis suggested that temperature, pH, total Fe, sulfate, and redox potentials (Eh) were significant factors that structured the microbial community compositions along the Aha watershed. PMID:25979900

Marine Chemistry in the People’s Republic of China.

DTIC Science & Technology

1984-08-01

Eh, Fe, Al, Mn, Cu, Pb, Zn, Cd, Hg, Cr, and also the sedimentation rate by Pb- 210 method. (2) The effects of flow rate, eddy diffusion, axial length of...sediments, distribution, determination, radium-226, uranium-238, radon-222, polonium - 210 , bismuth- 210 , lead-206, particulates, adsorption, polonium ...sediments, distribution, radium-226, uranium-238, radon-222, polonium - 210 , bismuth- 210 , lead-206, particulates, adsorption, polonium , dating, Zhujiang

(99)Tc(VII) Retardation, Reduction, and Redox Rate Scaling in Naturally Reduced Sediments.

PubMed

Liu, Yuanyuan; Liu, Chongxuan; Kukkadapu, Ravi K; McKinley, James P; Zachara, John; Plymale, Andrew E; Miller, Micah D; Varga, Tamas; Resch, Charles T

2015-11-17

An experimental and modeling study was conducted to investigate pertechnetate (Tc(VII)O4(-)) retardation, reduction, and rate scaling in three sediments from Ringold formation at U.S. Department of Energy's Hanford site, where (99)Tc is a major contaminant in groundwater. Tc(VII) was reduced in all the sediments in both batch reactors and diffusion columns, with a faster rate in a sediment containing a higher concentration of HCl-extractable Fe(II). Tc(VII) migration in the diffusion columns was reductively retarded with retardation degrees correlated with Tc(VII) reduction rates. The reduction rates were faster in the diffusion columns than those in the batch reactors, apparently influenced by the spatial distribution of redox-reactive minerals along transport paths that supplied Tc(VII). X-ray computed tomography and autoradiography were performed to identify the spatial locations of Tc(VII) reduction and transport paths in the sediments, and results generally confirmed the newly found behavior of reaction rate changes from batch to column. The results from this study implied that Tc(VII) migration can be reductively retarded at Hanford site with a retardation degree dependent on reactive Fe(II) content and its distribution in sediments. This study also demonstrated that an effective reaction rate may be faster in transport systems than that in well-mixed reactors.

Manganese and iron geochemistry in sediments underlying the redox-stratified Fayetteville Green Lake

NASA Astrophysics Data System (ADS)

Herndon, Elizabeth M.; Havig, Jeff R.; Singer, David M.; McCormick, Michael L.; Kump, Lee R.

2018-06-01

Manganese and iron are redox-sensitive elements that yield clues about biogeochemistry and redox conditions both in modern environments and in the geologic past. Here, we investigated Mn and Fe-bearing minerals preserved in basin sediments underlying Fayetteville Green Lake, a redox-stratified lake that serves as a geochemical analogue for Paleoproterozoic oceans. Synchrotron-source microprobe techniques (μXRF, μXANES, and μXRD) and bulk geochemical analyses were used to examine the microscale distribution and speciation of Mn, Fe, and S as a function of depth in the top 48 cm of anoxic lake sediments. Manganese was primarily associated with calcite grains as a manganese-rich carbonate that precipitated in the chemocline of the water column and settled through the euxinic basin to collect in lake sediments. Iron was preserved in framboidal iron sulfides that precipitated in euxinic bottom waters and underwent transformation to pyrite and marcasite in the sediments. Previous studies attribute the formation of manganese-rich carbonates to the diagenetic alteration of manganese oxides deposited in basins underlying oxygenated water. Our study challenges this paradigm by providing evidence that Mn-bearing carbonates form in the water column and accumulate in sediments below anoxic waters. Consequently, manganoan carbonates preserved in the rock record do not necessarily denote the presence of oxygenated bottom waters in ocean basins.

Phosphorus dynamics in lake sediments: Insights from field study and reactive-transport modeling

NASA Astrophysics Data System (ADS)

Dittrich, Maria; Markovic, Stefan; Cadena, Sandra; Doan, Phuong T. K.; Watson, Sue; Mugalingam, Shan

2016-04-01

Phosphorus is an indispensable nutrient for organisms in aquatic systems and its availability often controls primary productivity. At the sediment-water interface, intensive microbiological, geochemical and physical processes determine the fraction of organic matter, nutrients and pollutants released into the overlying water. Therefore, detailed understanding of the processes occurring in the top centimeters of the sediment is essential for the assessment of water quality and the management of surface waters. In cases where measurements are impossible or expensive, diagenetic modelling is required to investigate the interplay among the processes, verify concepts and predict potential system behavior. The main aims of this study are to identify and predict the dynamics of phosphorus (P) in sediments and gain insight into the mechanism of P release from sediments under varying environmental conditions. We measured redox, O2 and pH profiles with micro-sensors at the sediment-water interface; analyzed phosphate and metals (Fe, Mn, Al, Ca) content in pore waters collected using in situ samplers, so called "peepers"; determined P binding forms using sequential extraction and analyzed metals associated with each fraction. Following the sediment analysis, P binding forms were divided in five groups: inert, carbonate-bound, organic, redox-sensitive, and labile P. Using the flux of organic and inorganic matter as dynamic boundary conditions, the diagenetic model simulates P internal loading and predicts P retention. This presentation will discuss the results of two years studies on P dynamics at the sediment-water interface in three different lakes ranging from heavy-polluted Hamilton Harbor and Bay of Quinte to pristine Georgian Bay in Ontario, Canada.

Pyritic event beds and sulfidized Fe (oxyhydr)oxide aggregates in metalliferous black mudstones of the Paleoproterozoic Talvivaara formation, Finland

NASA Astrophysics Data System (ADS)

Virtasalo, Joonas J.; Laitala, Jaakko J.; Lahtinen, Raimo; Whitehouse, Martin J.

2015-12-01

The Paleoproterozoic, 2.0-1.9 Ga Talvivaara formation of Finland was deposited during the Shunga Event, a worldwide episode of enhanced accumulation of organic-rich sediments in the aftermath of the Lomagundi-Jatuli carbon isotope excursion. Sulfidic carbonaceous mudstones in the Talvivaara formation contain one of the largest known shale-hosted nickel deposits. In order to gain new insight into this Shungian sedimentary environment, sedimentological, petrographical and in situ S and Fe isotopic microanalyses were carried out on samples representing depositional and early-diagenetic conditions. The event-bedded lithology with tidal signatures in the organic-rich mudstones strongly indicates deposition from predominantly river-delivered mud on a highly-productive coastal area, below storm-wave base. The riverine supply of phosphorus, sulfate and iron supported high primary productivity and resulted in strong lateral and vertical chemical gradients in the nearshore waters with a shallow oxic surface layer underlain by euxinic water. The stratigraphic upper part of the Talvivaara formation contains banded intervals of thin alternating pyrite beds and carbonaceous mudstone beds. The pyrite beds were deposited by seaward excursions of the concentrated, acidic Fe-rich river plume subsequent to droughts or dry seasons, which led to intense pyrite precipitation upon mixing with euxinic waters. δ34S and δ56Fe values of the bedded pyrite (median δ34S = - 10.3 ‰ and δ56Fe = - 0.79 ‰) are consistent with the reaction of dissolved Fe(II) with H2S from bacterial sulfate reduction. Organic-rich clayey Fe-monosulfide-bearing granules were transported from the muddy estuary, and enclosed in Fe (oxyhydr)oxide aggregates that were forming by wave and current reworking in nearshore accumulations of river-delivered iron. The isotopic composition of these presently pyrrhotitic inclusions (median δ34S = - 3.3 ‰ and δ56Fe = - 1.6 ‰) indicates microbial iron reduction. The Fe (oxyhydr)oxide aggregates were transported in muddy debris flows to the distal euxinic seafloor. Their Fe (oxyhydr)oxide matrix was replaced by pyrite (median δ34S = + 5.8 ‰ and δ56Fe = + 0.81 ‰) at shallow sediment depths with 34S and 56Fe-enriched porewater. Wavy-crinkly laminae of possible microbial origin developed on the euxinic seafloor during low sedimentation. These results indicate episodic deposition at seasonal to multiannual time scales. δ34S and δ56Fe values in the studied Fe-sulfides provide evidence of microbial isotope fractionation processes and syndepositional and early-diagenetic origin, finding no support for the previously proposed local hydrothermal activity in the Talvivaara mudstones.

Carbohydrate oxidation coupled to Fe(III) reduction, a novel form of anaerobic metabolism

USGS Publications Warehouse

Coates, J.D.; Councell, T.; Ellis, D.J.; Lovley, D.R.

1998-01-01

An isolate, designated GC-29, that could incompletely oxidize glucose to acetate and carbon dioxide with Fe(III) serving as the electron acceptor was recovered from freshwater sediments of the Potomac River, Maryland. This metabolism yielded energy to support cell growth. Strain GC-29 is a facultatively anaerobic, Gram-negative motile rod which, in addition to glucose, also used sucrose, lactate, pyruvate, yeast extract, casamino acids or H2 as alternative electron donors for Fe(III) reduction. Stain GC-29 could reduce NO-3, Mn(IV), U(VI), fumarate, malate, S2O32-, and colloidal S0 as well as the humics analog, 2,6-anthraquinone disulfonate. Analysis of the almost complete 16S rRNA sequence indicated that strain GC-29 belongs in the Shewanella genus in the epsilon subdivision of the Proteobacteria. The name Shewanella saccharophilia is proposed. Shewanella saccharophilia differs from previously described fermentative microorganisms that metabolize glucose with the reduction of Fe(III) because it transfers significantly more electron equivalents to Fe(III); acetate and carbon dioxide are the only products of glucose metabolism; energy is conserved from Fe(III) reduction; and glucose is not metabolized in the absence of Fe(III). The metabolism of organisms like S. saccharophilia may account for the fact that glucose is metabolized primarily to acetate and carbon dioxide in a variety of sediments in which Fe(III) reduction is the terminal electron accepting process.

Multivariate analysis for source identification of pollution in sediment of Linggi River, Malaysia.

PubMed

Elias, Md Suhaimi; Ibrahim, Shariff; Samuding, Kamarudin; Rahman, Shamsiah Ab; Wo, Yii Mei; Daung, Jeremy Andy Dominic

2018-03-29

Rapid socioeconomic development in the Linggi River Basin has contributed to the significant increase of pollution discharge into the Linggi River and its adjacent coastal areas. The toxic element contents and distributions in the sediment samples collected along the Linggi River were determined using neutron activation analysis (NAA) and inductively coupled plasma-mass spectrometry (ICP-MS) techniques. The measured mean concentration of As, Cd, Pb, Sb, U, Th and Zn is relatively higher compared to the continental crust value of the respective element. Most of the elements (As, Cr, Fe, Pb, Sb and Zn) exceeded the freshwater sediment quality guideline-threshold effect concentration (FSQG-TEC) value. Downstream stations of the Linggi River showed that As concentrations in sediment exceeded the freshwater sediment quality guideline-probable effect concentration (FSQG-PEC) value. This indicates that the concentration of As will give an adverse effect to the growth of sediment-dwelling organisms. Generally, the Linggi River sediment can be categorised as unpolluted to strongly polluted and unpolluted to strongly to extremely polluted. The correlation matrix of metal-metal relationship, principle component analysis (PCA) and cluster analysis (CA) indicates that the pollution sources of Cu, Ni, Zn, Cd and Pb in sediments of the Linggi River originated from the industry of electronics and electroplating. Elements of As, Cr, Sb and Fe mainly originated from motor-vehicle workshops and metal work, whilst U and Th originated from natural processes such as terrestrial runoff and land erosion.

Implications of Fe/Pd Bimetallic Nanoparticles Immobilized on Adsorptive Activated Carbon for the Remediation of Groundwater and Sediment Contaminated with PCBs

EPA Science Inventory

In order to respond to the current limitations and challenges in remediating groundwater and sediment contaminated with polychlorinated biphenyls (PCBs), we have recently developed a new strategy, integration of the physical adsorption of PCBs with their electrochemical dechlori...

Metal pollution and ecological risk assessment in marine sediments of Karachi Coast, Pakistan.

PubMed

Mashiatullah, Azhar; Chaudhary, Muhammad Zaman; Ahmad, Nasir; Javed, Tariq; Ghaffar, Abdul

2013-02-01

Concentrations of 12 metals (Fe, Mn, Cr, Mo, Ni, Pb, Se, Sr, U, V, Zn, and Zr) in surface sediments of Karachi Coast, Pakistan were determined to evaluate their distribution and pollution assessment. The measured metals in the sediments were found to be in the range of Fe, 0.84-6.96 %; Mn, 300-1,300 μg/g; Cr, 12.0-319.84 μg/g; Mo, 0.49-2.03 μg/g; Ni, 1.53-58.86 μg/g; Pb, 9.0-49.46 μg/g; Se, 0.25-.86 μg/g; Sr, 192-1185 μg/g; U, 0.19-1.66 μg/g; V, 15.80-118.20 μg/g; Zn, 15.60-666.28 μg/g; and Zr, 44.02-175.26 μg/g. The mean contents of the metal studied were: Fe, 3.07 %, Mn, 0.05 %; Cr, 96.75 μg/g; Mo, 1.34 μg/g; Ni, 31.39 μg/g; Pb, 23.24 μg/g; Se, 0.61 μg/g; Sr, 374.83 μg/g; U, 0.64 μg/g; V, 61.75 μg/g; Zn, 204.75 μg/g; and Zr:76.27 μg/g, and arrangement of the metals from higher to lower mean content in this area is: Fe > Zn > Mn > Sr > Zn > Cr > Zr > V > Ni > Pb > Mo > U > Se. There is no significant correlation among most of these metals, indicating different anthropogenic and natural sources. To assess ecotoxic potential of marine sediments, Numerical Sediment Quality Guidelines were also applied. The concentration of Pb in all the sediments except one was lower than the threshold effect concentration (TECs) showing that there are no harmful effects to marine life from Pb. On the other hand, the concentrations of Cr, Ni, and Zn exceeded TEC in three stations, indicating their potential risk. The degree of pollution in sediments for metals was assessed by calculating enrichment factor (EF) and pollution load index (PLI). The results indicated that sediments of Layari River Mouth Area, Fish Harbour, and KPT Boat Building Area are highly enriched with Cr and Zn (EF > 5). Sediments of Layari River Outfall Zone were moderately enriched with Ni and Pb (EF > 2). The pollution load index was found in the range of 0.98 to 1.34. Lower values of PLI (≤ 1) at most of sampling locations imply no appreciable input from anthropogenic sources. However, relatively higher PLI values (>1) at Layari River Mouth Area, Fish Harbour, and KPT Boat Building Area are attributed to increased human activity in the area.

Oxidative dissolution of pyrite surfaces by hexavalent chromium: Surface site saturation and surface renewal

NASA Astrophysics Data System (ADS)

Graham, Andrew M.; Bouwer, Edward J.

2012-04-01

In-situ reduction of toxic Cr(VI) to nontoxic Cr(III) represents an important natural attenuation process for Cr(VI)-impacted environments. This study investigates the stoichiometry and kinetics of Cr(VI) reduction by pyrite, a reduced iron-sulfur mineral ubiquitous in recent estuarine and marine sediments. Pyrite suspensions at surface loadings of 0.28-2.10 m2/L (typical of estuarine or marine sediments) were capable of completely reducing 7-120 μM Cr(VI) on the timescale of minutes to days, with the time to reaction completion decreasing with increasing pyrite loading, decreasing initial Cr(VI) concentration, and decreasing suspension pH. Analysis of metal species (Cr and Fe) and sulfur species in solution and at the mineral surface indicated that Cr(VI) oxidatively dissolved the pyrite surface, releasing ferrous iron and sulfate into solution as the reaction progressed. Surface disulfide groups were postulated as the Cr(VI)-reactive surface entity. Net production or consumption of aqueous Fe(II) was shown to depend upon the relative rates of proton-promoted Fe(II) release, Fe(II) release due to oxidative dissolution of pyrite in the presence of Cr(VI), and Fe(II) consumption due to homogeneous reaction with Cr(VI). Kinetics of Cr(VI) reduction by pyrite displayed a biphasic pattern, and the time to reaction completion increased dramatically with increasing initial Cr(VI) concentration. Rapid Cr(VI) removal occurred early in the reaction progress, attributable to Cr(VI) loss under an adsorption-limited regime. Slow, approximately zero-order, Cr(VI) removal occurred over the bulk of the time courses, and corresponded to Cr(VI) removal under surface site saturation conditions. Stoichiometric Cr(VI) reduction was able to proceed under surface site limited conditions owing to regeneration of reactive surface sites following desorption/dissolution of oxidized surface products, as demonstrated in repeat Cr(VI)-spiking experiments. The role of surface passivation was evaluated by comparing rates of Cr(VI) reduction in the presence and absence of the Cr(III)-complexing agent citrate. While citrate addition significantly enhanced Cr(III) solubility, rates of Cr(VI) reduction were only marginally accelerated, suggesting that Cr(OH)3(s) coatings did not completely block access of Cr(VI) to reactive surface sites on pyrite. Given the rapid rates of Cr(VI) reduction with pyrite under pH and surface coverage conditions typical of natural environments, we propose that Cr(VI) reduction by pyrite be considered in fate and transport models for Cr in contaminated sediments.

Geologic Map of the San Luis Quadrangle, Costilla County, Colorado

USGS Publications Warehouse

Machette, Michael N.; Thompson, Ren A.; Drenth, Benjamin J.

2008-01-01

The map area includes San Luis and the primarily rural surrounding area. San Luis, the county seat of Costilla County, is the oldest surviving settlement in Colorado (1851). West of the town are San Pedro and San Luis mesas (basalt-covered tablelands), which are horsts with the San Luis fault zone to the east and the southern Sangre de Cristo fault zone to the west. The map also includes the Sanchez graben (part of the larger Culebra graben), a deep structural basin that lies between the San Luis fault zone (on the west) and the central Sangre de Cristo fault zone (on the east). The oldest rocks exposed in the map area are the Pliocene to upper Oligocene basin-fill sediments of the Santa Fe Group, and Pliocene Servilleta Basalt, a regional series of 3.7?4.8 Ma old flood basalts. Landslide deposits and colluvium that rest on sediments of the Santa Fe Group cover the steep margins of the mesas. Rare exposures of the sediment are comprised of siltstones, sandstones, and minor fluvial conglomerates. Most of the low ground surrounding the mesas and in the graben is covered by surficial deposits of Quaternary age. The alluvial deposits are subdivided into three Pleistocene-age units and three Holocene-age units. The oldest Pleistocene gravel (unit Qao) forms extensive coalesced alluvial fan and piedmont surfaces, the largest of which is known as the Costilla Plain. This surface extends west from San Pedro Mesa to the Rio Grande. The primary geologic hazards in the map area are from earthquakes, landslides, and localized flooding. There are three major fault zones in the area (as discussed above), and they all show evidence for late Pleistocene to possible Holocene movement. The landslides may have seismogenic origins; that is, they may be stimulated by strong ground shaking during large earthquakes. Machette and Thompson based this geologic map entirely on new mapping, whereas Drenth supplied geophysical data and interpretations.

Discrimination of fine-grained sediment provenance using geochemical elements on the inner shelf of the Korean Strait (South Sea), Korea

NASA Astrophysics Data System (ADS)

Um, I. K.; Choi, M. S.

2017-12-01

The central South Sea mud (CSSM) is located between the Heuksan mud belt (HMB) in the Yellow Sea and Korea Strait shelf mud (KSSM) in the East Sea and developed along the eastward transport pathway in the South Sea. Major elements (Al, Fe, Mg, and Ti), trace elements (Li, Cs, Sc, and Rb), and rare earth elements (REEs) in the fine-grained sediments (<15 μm) of thirty-two surface sediment samples on the CSSM were analyzed to determine the fine-grained sediment provenance. The spatial distribution of the analyzed elements showed a clear separation of the western (W-CSSM) and eastern (E-CSSM) regions of the CSSM. Concentrations of Fe, Ti, Mg, Sc, and REEs were higher in the W-CSSM, whereas concentrations of Al, Cs, Li, and Rb were higher in the E-CSSM. The ratios of trace metals ((Cs+Sc)/Li and Rb/Li) can be successfully used as a provenance indicator in the study area but REEs compositions could not be used to track the provenance of fine-grained sediments because of a grain size effect. The mixing relationships of the provenance indicators showed that the fine-grained sediments of the CSSM comprise a mixture of the sediments discharged from the Seomjin River (SRS) and sediments eroded and transported from the Heuksan mud belt (HMBS) area by the Korean coastal current. Sediments originating from the HMB were deposited mostly in the W-CSSM, whereas those from the Seomjin River were deposited mostly in the E-CSSM

Environmental monitoring and assessment of heavy metals in surface sediments at Coleroon River Estuary in Tamil Nadu, India.

PubMed

Venkatramanan, S; Chung, S Y; Ramkumar, T; Selvam, S

2015-08-01

The combined studies on grain size distribution, organic matter contents of sediments, sequential extraction and bulk concentration of heavy metals, statistical analysis, and ecological risk assessments were carried out to investigate the contamination sources and ecological risks of surface sediments at Coleroon River Estuary in Tamil Nadu, India. The sequential extraction of metals showed that a larger portion of the metals was associated with the residual phase and also in other fractions. The low concentrations of heavy metals were found in exchangeable and carbonate bounds (bioavailable phases). It revealed that sediments of Coleroon River Estuary were relatively unpolluted and were influenced mainly by natural sources. The observed order of bulk concentrations of heavy metals in the sediments was as follows: Fe > Mn > Zn > Cu > Pb > Cr > Ni > Co. Factor analyses represented that the enrichment of heavy metals was mostly resulted from lithogenic origins associated with anthropogenic sources. These sources were reconfirmed by cluster analysis. Risk assessment code (RAC) suggested that all metals were not harmful in monsoon season. However, Fe was in medium risk, and Mn and Cu were in low risk in summer. According to pollution load index (PLI) of sediments, all heavy metals were toxic. Cu might be related with adverse biological effects on the basis of sediment quality guidelines (SQG) in both seasons. These integrated approaches were very useful to identify the contamination sources and ecological risks of sediments in estuarine environment. It is expected that this research can give a useful information for the remediation of heavy metals in sediments.

Spatial and temporal variations of Rb/Sr ratios of the bulk surface sediments in Lake Qinghai

PubMed Central

2010-01-01

The Rb/Sr ratios of lake sediments have been suggested as indicators of weathering intensity by increasing work. However, the geochemistry of Rb/Sr ratios of lake sediments is variable between different lakes. In this study, we investigated the spatial and temporal patterns of Rb/Sr ratios, as well as those of other major elements in surface sediments of Lake Qinghai. We find that the spatial pattern of Rb/Sr ratios of the bulk sediments correlates well with that of the mass accumulation rate, and those of the terrigenous fractions, e.g., SiO2, Ti, and Fe. The temporal variations of Rb/Sr ratios also synchronize with those of SiO2, Ti, and Fe of each individual core. These suggest that Rb/Sr ratios of the surface sediments are closely related to terrigenous input from the catchment. Two out of eight cores show similar trends between Rb/Sr ratios and precipitation indices on decadal scales; however, the other cores do not show such relationship. The result of this study suggests that physical weathering and chemical weathering in Lake Qinghai catchment have opposite influence on Rb/Sr ratios of the bulk sediments, and they compete in dominating the Rb/Sr ratios of lake sediments on different spatial and temporal scales. Therefore, it is necessary to study the geochemistry of Rb/Sr ratio of lake sediments (especially that on short term timescales) particularly before it is used as an indicator of weathering intensity of the catchment. PMID:20615264

Characterizing suspended sediments from the Piracicaba River Basin by means of k0-INAA

NASA Astrophysics Data System (ADS)

França, E. J.; Fernandes, E. A. N.; Cavalca, I. P. O.; Fonseca, F. Y.; Camilli, L.; Rodrigues, V. S.; Bardini Junior, C.; Ferreira, J. R.; Bacchi, M. A.

2010-10-01

The inorganic chemical characterization of suspended sediments is of utmost relevance for the knowledge of the dynamics and movement of chemical elements in the aquatic and wet ecosystems. Despite the complexity of the effective design for studying this ecological compartment, this work has tested a procedure for analyzing suspended sediments by instrumental neutron activation analysis, k0 method ( k0-INAA). The chemical elements As, Ba, Br, Ca, Ce, Co, Cr, Cs, Eu, Fe, Hf, Hg, K, La, Mo, Na, Ni, Rb, Sb, Sc, Se, Sm, Sr, Ta, Tb, Th, Yb and Zn were quantified in the suspended sediment compartment by means of k0-INAA. When compared with World Average for rivers, high mass fractions of Fe (222,900 mg/kg), Ba (4990 mg/kg), Zn (1350 mg/kg), Cr (646 mg/kg), Co (74.5 mg/kg), Br (113 mg/kg) and Mo (31.9 mg/kg) were quantified in suspended sediments from the Piracicaba River, the Piracicamirim Stream and the Marins Stream. Results of the principal component analysis for standardized chemical element mass fractions indicated an intricate correlation among chemical elements evaluated, as a response of the contribution of natural and anthropogenic sources of chemical elements for ecosystems.

Iron speciation in peats: Chemical and spectroscopic evidence for the co-occurrence of ferric and ferrous iron in organic complexes and mineral precipitates

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

Bhattacharyya, Amrita; Schmidt, Michael P.; Stavitski, Eli

The speciation of iron (Fe) in organic matter (OM)-rich environments under in situ variable redox conditions is largely unresolved. Peatlands provide a natural setting to study Fe–OM interactions. Utilizing chemical, spectroscopic and theoretical modeling approaches, we report the chemical forms, oxidation states and local coordination environment of naturally occurring Fe in the vertically redox-stratified Manning peatlands of western New York. In addition, we report dominant carbon, sulfur and nitrogen species that can potentially stabilize the various Fe species present in these peatlands. Our results provide clear direct and indirect evidence for the co-occurrence of ferrous (Fe 2+) and ferric (Femore » 3+) iron species in peats under both oxic and anoxic conditions. Iron is mostly present within the operationally defined organic and amorphous (i.e., short range ordered, SRO) fractions; ferric iron primarily as magnetically isolated paramagnetic Fe 3+ in Fe(III)-organic complexes, but also in mineral forms such as ferrihydrite; ferrous iron in tetrahedral coordination in Fe(II)-organic complexes with minor contribution from pyrite. All of the Fe species identified stabilize Fe(III) and/or Fe(II) in anoxic and oxic peats. Fundamental differences are also observed in the relative proportion of C, S and N functionalities of OM in oxic and anoxic peats. Aromatic C=C, ester, phenol and anomeric C (R-O-C-O-R), as well as thiol, sulfide and heterocyclic N functionalities are more prevalent in anoxic peats. Collectively, our experimental evidence suggests iron forms coordination complexes with O-, S- and N-containing functional groups of OM. We posit the co-occurrence of organic and mineral forms of Fe(II) and Fe(III) in both oxic and anoxic peat layers results from dynamic complexation and hydrolysis-precipitation reactions that occur under variable redox conditions. In conclusion, our findings aid in understanding the crucial role OM plays in determining Fe species in soils and sediments.« less

Iron speciation in peats: Chemical and spectroscopic evidence for the co-occurrence of ferric and ferrous iron in organic complexes and mineral precipitates

DOE PAGES

Bhattacharyya, Amrita; Schmidt, Michael P.; Stavitski, Eli; ...

2017-10-31

The speciation of iron (Fe) in organic matter (OM)-rich environments under in situ variable redox conditions is largely unresolved. Peatlands provide a natural setting to study Fe–OM interactions. Utilizing chemical, spectroscopic and theoretical modeling approaches, we report the chemical forms, oxidation states and local coordination environment of naturally occurring Fe in the vertically redox-stratified Manning peatlands of western New York. In addition, we report dominant carbon, sulfur and nitrogen species that can potentially stabilize the various Fe species present in these peatlands. Our results provide clear direct and indirect evidence for the co-occurrence of ferrous (Fe 2+) and ferric (Femore » 3+) iron species in peats under both oxic and anoxic conditions. Iron is mostly present within the operationally defined organic and amorphous (i.e., short range ordered, SRO) fractions; ferric iron primarily as magnetically isolated paramagnetic Fe 3+ in Fe(III)-organic complexes, but also in mineral forms such as ferrihydrite; ferrous iron in tetrahedral coordination in Fe(II)-organic complexes with minor contribution from pyrite. All of the Fe species identified stabilize Fe(III) and/or Fe(II) in anoxic and oxic peats. Fundamental differences are also observed in the relative proportion of C, S and N functionalities of OM in oxic and anoxic peats. Aromatic C=C, ester, phenol and anomeric C (R-O-C-O-R), as well as thiol, sulfide and heterocyclic N functionalities are more prevalent in anoxic peats. Collectively, our experimental evidence suggests iron forms coordination complexes with O-, S- and N-containing functional groups of OM. We posit the co-occurrence of organic and mineral forms of Fe(II) and Fe(III) in both oxic and anoxic peat layers results from dynamic complexation and hydrolysis-precipitation reactions that occur under variable redox conditions. In conclusion, our findings aid in understanding the crucial role OM plays in determining Fe species in soils and sediments.« less

Sulphide-sulphate stability and melting in subducted sediment and its role in arc mantle redox and chalcophile cycling in space and time

NASA Astrophysics Data System (ADS)

Canil, Dante; Fellows, Steven A.

2017-07-01

The redox budget during subduction is tied to the evolution of oxygen and biogeochemical cycles on Earth's surface over time. The sulphide-sulphate couple in subducted crust has significant potential for redox and control on extraction of chalcophile metals from the arc mantle. We derive oxygen buffers for sulphide-sulphate stability ('SSO buffers') using mineral assemblages in subducted crust within the eclogite facies, and examine their disposition relative to the fO2 in the arc mantle along various P-T trajectories for subduction. The fO2 required for sulphide stability in subducted crust passing beneath an arc is shifted by variations in the bulk Ca/(Ca + Mg + Fe) of the subducting crust alone. Hotter slabs and more Fe-rich sediments stabilize sulphide and favour chalcophile sequestration deep into the mantle, whereas colder slabs and calcic sediment will stabilize anhydrite, in some cases at depths of melt generation in the arc mantle (<130 km). The released sulphate on melting potentially increases the fO2 of the arc mantle. We performed melting experiments on three subducted sediment compositions varying in bulk Ca/(Ca + Mg + Fe) from 0.3 to 0.6 at 2.5 GPa and 900-1100 °C to confirm how anhydrite stability can change by orders of magnitude the S, Cu, As, Zn, Mo, Pb, and Sb contents of sediment melts, and their subsequent liberation to the arc mantle. Using Cu/Sc as a proxy for the behaviour of S, the effect of variable subducted sediment composition on sulphide-sulphate stability and release of chalcophiles to the arc mantle is recognizable in volcanic suites from several subduction zones in space and time. The fO2 of the SSO buffers in subducted sediment relative to the arc mantle may have changed with time by shifts in the nature of pelagic sedimentation in the oceans over earth history. Oxidation of arc mantle and the proliferation of porphyry Cu deposits may be latter-day advents in earth history partly due to the rise of planktic calcifiers in the oceans in only the past 250 million years.

Effect of mining and related activities on the sediment trace element geochemistry of Lake Coeur D'Alene, Idaho, USA. Part I: Surface sediments

USGS Publications Warehouse

Horowitz, Arthur J.; Elrick, Kent A.; Cook, Robert B.

1993-01-01

During the summer of 1989 surface sediment samples were collected in Lake Coeur d'Alene, the Coeur d'Alene River and the St Joe River, Idaho, at a density of approximately one sample per square kilometre. Additional samples were collected from the banks of the South Fork of the Coeur d'Alene and the Coeur d'Alene Rivers in 1991. All the samples were collected to determine trace element concentrations, partitioning and distribution patterns, and to relate them to mining, mining related and discharge operations that have occurred in the Coeur d'Alene district since the 1880s, some of which are ongoing.Most of the surface sediments in Lake Coeur d'Alene north of Conkling Point and Carey Bay are substantially enriched in Ag, As, Cu, Cd, Hg, Pb, Sb and Zn relative to unaffected sediments in the southern portion of the lake near the St Joe River. All the trace element enriched sediments are extremely fine grained (mean grain sizes « 63 μm). Most of the enriched trace elements, based on both the chemical analyses of separated heavy and light mineral fractions and a two step sequential extraction procedure, are associated with an operationally defined Fe oxide phase; much smaller percentages are associated either with operationally defined organics/sulphides or refractory phases.The presence, concentration and distribution of the Fe oxides and heavy minerals indicates that a substantial portion of the enriched trace elements are probably coming from the Coeur d'Alene River, which is serving as a point source. Within the lake, this relatively simple point source pattern is complicated by a combination of (1) the formation of trace element rich authigenic Fe oxides that appear to have reprecipitated from material solubilized from anoxic bed sediments and (2) physical remobilization by currents and wind driven waves. The processes that have caused the trace element enrichment in the surface sediments of Lake Coeur d'Alene are likely to continue for the foreseeable future.

Spatial patterns and origins of heavy metals in Sheyang River catchment in Jiangsu, China based on geographically weighted regression.

PubMed

Wu, Shan-Shan; Yang, Hao; Guo, Fei; Han, Rui-Ming

2017-02-15

Multivariate statistical analyses combined with geographically weighted regression (GWR) were used to identify spatial variations of heavy metals in sediments and to examine relationships between metal pollution and land use practices in watersheds, including urban land, agriculture land, forest and water bodies. Seven metals (Cu, Zn, Pb, Cr, Ni, Mn and Fe) of sediments were measured at 31 sampling sites in Sheyang River. Most metals were under a certain degree enrichment based on the enrichment factors. Cluster analysis grouped all sites into four statistically significant cluster, severely contaminated areas were concentrated in areas with intensive human activities. Correlation analysis and PCA indicated Cu, Zn and Pb were derived from anthropogenic activities, while the sources of Cr and Ni were complicated. However, Fe and Mn originated from natural sources. According to results of GWR, there are stronger association between metal pollution with urban land than agricultural land and forest. Moreover, the relationships between land use and metal concentration were affected by the urbanization level of watersheds. Agricultural land had a weak associated with heavy metal pollution and the relationships might be stronger in less-urbanized. This study provided useful information for the assessment and management of heavy metal hazards in studied area. Copyright © 2016 Elsevier B.V. All rights reserved.

The Geologic Signature of Anaerobic Oxidation of Methane (Invited)

NASA Astrophysics Data System (ADS)

Ussler, W.; Paull, C. K.

2010-12-01

Anaerobic oxidation of methane (AOM) is an enormous sink in anoxic marine sediments for methane produced in situ or ascending through the sediment column towards the seafloor. Existing estimates indicate that between 75 and 382 Tg of sedimentary methane are oxidized each year before reaching the sediment-water interface making AOM a diagenetic process of global significance. This methane is derived from a variety of sources including microbial production, thermocatalytic cracking of complex organic matter, decomposing gas hydrates, and possibly abiogenic processes. Stables isotopes of membrane lipid biomarkers and authigenic carbonates associated with zones of AOM, fluorescence in situ hybridization, and anaerobic methane incubations have substantiated the role Archaea and sulfate-reducing bacteria have in driving AOM. The products of AOM are dissolved inorganic carbon (predominantly HCO3-) and bisulfide (HS-). Stable isotope measurements of authigenic carbonates associated with zones of AOM are consistent with the diagenetic carbon being primarily methane derived. These methane-derived carbonates occur in a variety of forms including sedimentary nodules and thin lenses within and below zones of contemporary AOM; outcrops of slabs, ledges, and jagged authigenic carbonates exhumed on the seafloor; and authigenic carbonate mounds associated with near-subsurface methane gas accumulations. Examples of exhumed authigenic carbonates include rugged outcrops along the Guaymas Transform in the Gulf of California, extensive slabs and ledges in the Eel River Basin, and mounds in various stages of development near Bullseye Vent, off Vancouver Island and in the Santa Monica Basin. It is clear from basic microbial biogeochemistry and the occurrences of massive authigenic carbonate which span a large range in size that DIC produced by AOM is preserved as authigenic carbonate within the seafloor and not on the seafloor. These exhumed authigenic carbonate provide a glimpse of how authigenic carbonates may be appear in the geologic record. Based on the stochiometry of the AOM reaction [CH4 + SO4= → HCO3- + HS-], HCO3- and HS- should occur in a 1:1 molar ratio in sediment pore water. Methane-derived carbonates are common in methane-rich sediments and methane venting areas, however the corresponding amount of HS- precipitated as iron monosulfides (FeS) is not. The prediction, based on their molecular weights and densities, is that the volume ratio of authigenic carbonate to FeS should be 2:1. However, in anoxic Black Sea sediments, where a high degree of preservation would be expected, the authigenic carbonate to FeS ratio is ~50:1. Massive accumulations of FeS associated with authigenic carbonates have not been observed. There are a number of fates for the HS- produced by AOM: (1) HS- is oxidized in situ adding sulfate back to the pore water pool; (2) HS- selectively diffuses (relative to HCO3-) towards the seafloor and is oxidized in the benthic water column; or (3) FeS precipitates, but is oxidized when authigenic carbonates are exhumed leaving a vuggy texture. None of these explanations are entirely satisfactory for the early diagenetic loss of HS- from sediments, but strongly suggest that massive accumulations of FeS derived from AOM will not be found in the geologic record.

Heavy metals relationship with water and size-fractionated sediments in rivers using canonical correlation analysis (CCA) case study, rivers of south western Caspian Sea.

PubMed

Vosoogh, Ali; Saeedi, Mohsen; Lak, Raziyeh

2016-11-01

Some pollutants can qualitatively affect aquatic freshwater such as rivers, and heavy metals are one of the most important pollutants in aquatic fresh waters. Heavy metals can be found in the form of components dissolved in these waters or in compounds with suspended particles and surface sediments. It can be said that heavy metals are in equilibrium between water and sediment. In this study, the amount of heavy metals is determined in water and different sizes of sediment. To obtain the relationship between heavy metals in water and size-fractionated sediments, a canonical correlation analysis (CCA) was utilized in rivers of the southwestern Caspian Sea. In this research, a case study was carried out on 18 sampling stations in nine rivers. In the first step, the concentrations of heavy metals (Cu, Zn, Cr, Fe, Mn, Pb, Ni, and Cd) were determined in water and size-fractionated sediment samples. Water sampling sites were classified by hierarchical cluster analysis (HCA) utilizing squared Euclidean distance with Ward's method. In addition, for interpreting the obtained results and the relationships between the concentration of heavy metals in the tested river water and sample sediments, canonical correlation analysis (CCA) was utilized. The rivers were grouped into two classes (those having no pollution and those having low pollution) based on the HCA results obtained for river water samples. CCA results found numerous relationships between rivers in Iran's Guilan province and their size-fractionated sediments samples. The heavy metals of sediments with 0.038 to 0.125 mm size in diameter are slightly correlated with those of water samples.

Mineral ecophysiological evidence for microbial activity in banded iron formation

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

Li, Dr. Yi-Liang; Konhauser, Dr, Kurt; Cole, David R

2011-01-01

The phosphorus composition of banded-iron formations (BIFs) has been used as a proxy for Precambrian seawater composition and the paleoeredox state of Earth's surface environment. However, it is unclear whether the phosphorus in BIFs originally entered the sediment as a sorbed component of the iron oxyhydroxide particles, or whether it was incorporated into the biomass of marine phytoplankton. We conducted high-resolution mineral analyses and report here the first detection of an Fe(III) acetate salt, as well as nanocrystals of apatite in association with magnetite, in the 2.48 Ga Dales Gorge Member of the Brockman Iron Formation (a BIF), Hamersley, Westernmore » Australia. The clusters of apatite are similar in size and morphology to biogenic apatite crystals resulting from biomass decay in Phanerozoic marine sediments, while the formation of an Fe(III) acetate salt and magnetite not only implies the original presence of biomass in the BIF sediments, but also that organic carbon likely served as an electron donor during bacterial Fe(III) reduction. This study is important because it suggests that phytoplankton may have played a key role in the transfer of phosphorus (and other trace elements) from the photic zone to the seafloor.« less

Potential for microbial H2 and metal transformations associated with novel bacteria and archaea in deep terrestrial subsurface sediments.

PubMed

Hernsdorf, Alex W; Amano, Yuki; Miyakawa, Kazuya; Ise, Kotaro; Suzuki, Yohey; Anantharaman, Karthik; Probst, Alexander; Burstein, David; Thomas, Brian C; Banfield, Jillian F

2017-08-01

Geological sequestration in deep underground repositories is the prevailing proposed route for radioactive waste disposal. After the disposal of radioactive waste in the subsurface, H 2 may be produced by corrosion of steel and, ultimately, radionuclides will be exposed to the surrounding environment. To evaluate the potential for microbial activities to impact disposal systems, we explored the microbial community structure and metabolic functions of a sediment-hosted ecosystem at the Horonobe Underground Research Laboratory, Hokkaido, Japan. Overall, we found that the ecosystem hosted organisms from diverse lineages, including many from the phyla that lack isolated representatives. The majority of organisms can metabolize H 2 , often via oxidative [NiFe] hydrogenases or electron-bifurcating [FeFe] hydrogenases that enable ferredoxin-based pathways, including the ion motive Rnf complex. Many organisms implicated in H 2 metabolism are also predicted to catalyze carbon, nitrogen, iron and sulfur transformations. Notably, iron-based metabolism is predicted in a novel lineage of Actinobacteria and in a putative methane-oxidizing ANME-2d archaeon. We infer an ecological model that links microorganisms to sediment-derived resources and predict potential impacts of microbial activity on H 2 consumption and retardation of radionuclide migration.

Role of Dissolved Organic Matter and Geochemical Controls on Arsenic Cycling from Sediments to Groundwater along the Meghna River, Bangladesh: Tracking possible links to permeable natural reactive barrier

NASA Astrophysics Data System (ADS)

Datta, S.; Berube, M.; Knappett, P.; Kulkarni, H. V.; Vega, M.; Jewell, K.; Myers, K.

2017-12-01

Elevated levels of dissolved arsenic (As), iron (Fe) and manganese (Mn) are seen in the shallow groundwaters of southeast Bangladesh on the Ganges Brahmaputra Meghna River delta. This study takes a multi disciplinary approach to understand the extent of the natural reactive barrier (NRB) along the Meghna River and evaluate the role of the NRB in As sequestration and release in groundwater aquifers. Shallow sediment cores, and groundwater and river water samples were collected from the east and west banks of the Meghna. Groundwater and river water samples were tested for FeT, MnT, and AsT concentrations. Fluorescence spectroscopic characterization of groundwater dissolved organic matter (DOM) provided insight into the hydro geochemical reactions active in the groundwater and the hyporheic zones. Eight sediment cores of 1.5 m depth were collected 10 m away from the edge of the river. Vertical solid phase concentration profiles of Fe, Mn and As were measured via 1.2 M HCl digestion which revealed solid phase As accumulation along the riverbanks up to concentrations of 1500 mg/kg As. Microbial interactions with DOM prompts the reduction of Fe3+ to Fe2+, causing As to mobilize into groundwater and humic-like DOM present in the groundwater may catalyze this process. The extent to which microbially mediated release of As occurs is limited by labile dissolved organic carbon (DOC) availability. Aqueous geochemical results showed the highest dissolved As concentrations in shallow wells (<30 m depth), where organic matter was fresh, humic-like, and aromatic. Based on fluorescence characterization, shallow groundwater was found to contain microbial and terrestrial derived DOC, and decomposed, humified and aromatic DOM. Deeper aquifers had a significantly larger microbial OM signature than the shallower aquifers and was less aromatic, decomposed and humified. The results from this study illustrate the potential for humic substances to contribute to As cycling and quantify the extent of As accumulation in the sediments and groundwater along a 1 km stretch of the Meghna. These findings contribute to the overall understanding of geochemical processes involved in As release into groundwaters from sediments within a fluvial deltaic environment and close proximity to a possible permeable natural reactive barrier.

Dissimilatory Fe(III) and Mn(IV) reduction.

PubMed Central

Lovley, D R

1991-01-01

The oxidation of organic matter coupled to the reduction of Fe(III) or Mn(IV) is one of the most important biogeochemical reactions in aquatic sediments, soils, and groundwater. This process, which may have been the first globally significant mechanism for the oxidation of organic matter to carbon dioxide, plays an important role in the oxidation of natural and contaminant organic compounds in a variety of environments and contributes to other phenomena of widespread significance such as the release of metals and nutrients into water supplies, the magnetization of sediments, and the corrosion of metal. Until recently, much of the Fe(III) and Mn(IV) reduction in sedimentary environments was considered to be the result of nonenzymatic processes. However, microorganisms which can effectively couple the oxidation of organic compounds to the reduction of Fe(III) or Mn(IV) have recently been discovered. With Fe(III) or Mn(IV) as the sole electron acceptor, these organisms can completely oxidize fatty acids, hydrogen, or a variety of monoaromatic compounds. This metabolism provides energy to support growth. Sugars and amino acids can be completely oxidized by the cooperative activity of fermentative microorganisms and hydrogen- and fatty-acid-oxidizing Fe(III) and Mn(IV) reducers. This provides a microbial mechanism for the oxidation of the complex assemblage of sedimentary organic matter in Fe(III)- or Mn(IV)-reducing environments. The available evidence indicates that this enzymatic reduction of Fe(III) or Mn(IV) accounts for most of the oxidation of organic matter coupled to reduction of Fe(III) and Mn(IV) in sedimentary environments. Little is known about the diversity and ecology of the microorganisms responsible for Fe(III) and Mn(IV) reduction, and only preliminary studies have been conducted on the physiology and biochemistry of this process. PMID:1886521

Quaternary stratigraphy, sediment characteristics and geochemistry of arsenic-contaminated alluvial aquifers in the Ganges-Brahmaputra floodplain in central Bangladesh.

PubMed

Shamsudduha, M; Uddin, A; Saunders, J A; Lee, M-K

2008-07-29

This study focuses on the Quaternary stratigraphy, sediment composition, mineralogy, and geochemistry of arsenic (As)-contaminated alluvial aquifers in the Ganges-Brahmaputra floodplain in the central Bangladesh. Arsenic concentrations in 85 tubewells in Manikganj area, 70 km northwest of Dhaka City, range from 0.25 microg/L to 191 microg/L with a mean concentration of 33 microg/L. Groundwater is mainly Ca-HCO(3) type with high concentrations of dissolved As, Fe, and Mn, but low level of SO(4). The uppermost aquifer occurs between 10 m and 80 m below the surface that has a mean arsenic concentration of 35 microg/L. Deeper aquifer (>100 m depth) has a mean arsenic concentration of 18 microg/L. Sediments in the upper aquifer are mostly gray to dark-gray, whereas sediments in the deep aquifer are mostly yellowing-gray to brown. Quartz, feldspar, mica, hornblende, garnet, kyanite, tourmaline, magnetite, ilmenite are the major minerals in sediments from both aquifers. Biotite and potassium feldspar are dominant in shallow aquifer, although plagioclase feldspar and garnet are abundant in deep aquifer sediments. Sediment composition suggests a mixed provenance with sediment supplies from both orogenic belts and cratons. High arsenic concentrations in sediments are found within the upper 50 m in drilled core samples. Statistical analysis shows that As, Fe, Mn, Ca, and P are strongly correlated in sediments. Concentrations of Cd, Cu, Ni, Zn, and Bi also show strong correlations with arsenic in the Manikganj sediment cores. Authigenic goethite concretions, possibly formed by bacteria, are found in the shallow sediments, which contain arsenic of a concentration as high as 8.8 mg/kg. High arsenic concentrations in aquifers are associated with fine-grained sediments that were derived mostly from the recycled orogens and relatively rapidly deposited mainly by meandering channels during the Early to Middle Holocene rising sea-level conditions.

Anaerobic mineralization of vinyl chloride in Fe(III)-reducing, aquifer sediments

USGS Publications Warehouse

Bradley, P.M.; Chapelle, F.H.

1996-01-01

Within anaerobic aquifer systems, reductive dehalogenation of polychlorinated ethenes commonly results in the accumulation of vinyl chloride, which is highly toxic and carcinogenic to humans. Anaerobic reduction of vinyl chloride is considered to be slow and incomplete. Here, we provide the first evidence for anaerobic oxidation of vinyl chloride under Fe(III)reducing conditions. Addition of chelated Fe(III) (as Fe-EDTA) to anaerobic aquifer microcosms resulted in mineralization of up to 34% of [1,2- 14C]vinyl chloride within 84 h. The results indicate that vinyl chloride can be mineralized under anaerobic, Fe(III)-reducing conditions and that the bioavailability of Fe(III) is an important factor affecting the rates of mineralization.

Metal distribution in sediment cores from São Paulo State Coast, Brazil.

PubMed

Silva, Paulo S C; Damatto, Sandra R; Maldonado, Caio; Fávaro, Deboráh I T; Mazzilli, Barbara P

2011-05-01

Ten sediment core samples with lengths ranging from 35 to 100 cm were collected in the Baixada Santista region and analyzed to determine As, Br, Co, Cr, Cs, Fe, Rb, Sb, Ta, Th, U, Zn and rare earths (Sc, Ce, Eu, La, Lu, Nd, Sm, Tb and Yb) level concentrations using instrumental neutron activation analysis (INAA). The studied region is located in the southeastern coast of São Paulo State and is comprised of a densely urbanized area, the largest industrial complex of the country, with a predominance of petrochemical and fertilizer plants. It is also home to Brazil's most important and busiest port. The conclusions found that the As, La, Sm, Ne, Ce, Eu, Hf, Ta, Th, and U elements have a high background level in the region and that Fe and Zn were the main indicators of anthropogenic contribution in the sediments. Copyright © 2011 Elsevier Ltd. All rights reserved.

Geochemical Fractionations and Mobility of Arsenic, Lead and Cadmium in Sediments of the Kanto Plain, Japan.

NASA Astrophysics Data System (ADS)

Hossain, Sushmita; Oguchi, Chiaki T.; Hachinohe, Shoichi; Ishiyama, Takashi; Hamamoto, Hideki

2014-05-01

Lowland alluvial and floodplain sediment play a major role in transferring heavy metals and other elements to groundwater through sediment water interaction in changing environmental conditions. However identification of geochemical forms of toxic elements such as arsenic (As), lead (Pb) and cadmium (Cd) requires risk assessment of sediment and subsequent groundwater pollution. A four steps sequential extraction procedure was applied to characterize the geochemical fractionations of As, Pb and Cd for 44 sediment samples including one peat sample from middle basin area of the Nakagawa river in the central Kanto plain. The studied sediment profile extended from the bottom of the river to 44 m depth; sediment samples were collected at 1m intervals from a bored core. The existing sedimentary facies in vertical profile are continental, transitional and marine. There are two aquifers in vertical profile; the upper aquifer (15-20m) contains fine to medium sand whereas medium to coarse sand and gravelly sand contain in lower aquifer (37-44m). The total As and Pb contents were measured by the X-Ray Fluorescence analysis which ranged from 4 to 23 mg/kg of As and 10 to 27 mg/kg of Pb in sediment profile. The three trace elements and major heavy metals were determined by ICP/MS and ICP/AES, and major ions were measured by an ion chromatograph. The marine sediment is mainly Ca-SO4 type. The Geochemical analysis showed the order of mobility trends to be As > Pb > Cd for all the steps. The geochemical fractionations order was determined to be Fe-Mn oxide bound > carbonate bound > ion exchangeable > water soluble for As and Pb whereas the order for Cd is carbonate bound > Fe-Mn oxide bound > ion exchangeable > water soluble. The mobility tendency of Pb and Cd showed high in fine silty sediment of marine environment than for those from continental and transitional environments. In the case of As, the potential mobility is very high (>60%) in the riverbed sediments and clayey silt sediment at 13m depth which is just above the upper aquifer. This potential mobility may pose a threat to upper aquifer and riverbed aquatic system. The overall geochemical analysis revealed that the dissolution of Fe-Mn oxide is the most effective mechanism for As, Pb in groundwater however the mobility of Cd is mainly carbonate bound. In the present study, the pollution level is much below from leaching environmental standards (0.01 mg/L) for all three elements and the total content is within the natural abundance of As, Pb and Cd in sediment. The potential mobility of these elements in oxidized fine silty sediment and the possible further effect to the aquifer suggest that shallow groundwater abstraction should be restricted to protect seasonal groundwater fluctuation. Moreover marine sediment containing high total toxic element contents and mobility tendency at changing oxidation and reduction environments requires proper management when sediments are excavated for construction purpose.

Geochemical and lithological factors in acid precipitation

Treesearch

James R. Kramer

1976-01-01

Acid precipitation is altered by interaction with rocks, sediment and soil. A calcareous region buffers even the most intense loading at pH ~8; an alumino silicate region with unconsolidated sediment buffers acid loadings at pH ~6.5; alumino silicate outcrops are generally acidified. Either FeOOH or alumino silicates are probable H+...

Metal concentrations in sediments from tourist beaches of Miri City, Sarawak, Malaysia (Borneo Island).

PubMed

Nagarajan, R; Jonathan, M P; Roy, Priyadarsi D; Wai-Hwa, L; Prasanna, M V; Sarkar, S K; Navarrete-López, M

2013-08-15

Forty-three sediment samples were collected from the beaches of Miri City, Sarawak, Malaysia to identify the enrichment of partially leached trace metals (PLTMs) from six different tourist beaches. The samples were analyzed for PLTMs Fe, Mn, Cr, Co, Cu, Ni, Pb, Sr and Zn. The concentration pattern suggest that the southern side of the study area is enriched with Fe (1821-6097 μg g(-1)), Mn (11.57-90.22 μg g(-1)), Cr (51.50-311 μg g(-1)), Ni (18-51 μg g(-1)), Pb (8.81-84.05 μg g(-1)), Sr (25.95-140.49 μg g(-1)) and Zn (12.46-35.04 μg g(-1)). Compared to the eco-toxicological values, Cr>Effects range low (ERL), Lowest effect level (LEL), Severe effect level (SEL); Cu>Unpolluted sediments, ERL, LEL; Pb>Unpolluted sediments and Ni>ERL and LEL. Comparative results with other regions indicate that Co, Cr, Cu, Ni and Zn are higher, indicating an external input rather than natural process. Copyright © 2013 Elsevier Ltd. All rights reserved.

Attenuation and colloidal mobilization of bacteriophages in natural sediments under anoxic as compared to oxic conditions.

PubMed

Klitzke, Sondra; Schroeder, Jendrik; Selinka, Hans-Christoph; Szewzyk, Regine; Chorus, Ingrid

2015-06-15

Redox conditions are known to affect the fate of viruses in porous media. Several studies report the relevance of colloid-facilitated virus transport in the subsurface, but detailed studies on the effect of anoxic conditions on virus retention in natural sediments are still missing. Therefore, we investigated the fate of viruses in natural flood plain sediments with different sesquioxide contents under anoxic conditions by considering sorption to the solid phase, sorption to mobilized colloids, and inactivation in the aqueous phase. Batch experiments were conducted under oxic and anoxic conditions at pH values between 5.1 and 7.6, using bacteriophages MS2 and PhiX174 as model viruses. In addition to free and colloid-associated bacteriophages, dissolved and colloidal concentrations of Fe, Al and organic C as well as dissolved Ca were determined. Results showed that regardless of redox conditions, bacteriophages did not adsorb to mobilized colloids, even under favourable charge conditions. Under anoxic conditions, attenuation of bacteriophages was dominated by sorption over inactivation, with MS2 showing a higher degree of sorption than PhiX174. Inactivation in water was low under anoxic conditions for both bacteriophages with about one log10 decrease in concentration during 16 h. Increased Fe/Al concentrations and a low organic carbon content of the sediment led to enhanced bacteriophage removal under anoxic conditions. However, even in the presence of sufficient Fe/A-(hydr)oxides on the solid phase, bacteriophage sorption was low. We presume that organic matter may limit the potential retention of sesquioxides in anoxic sediments and should thus be considered for the risk assessment of virus breakthrough in the subsurface. Copyright © 2015 Elsevier B.V. All rights reserved.

[Pollution Characteristics and Potential Ecological Risk of Heavy Metals in Urban Surface Water Sediments from Yongkang].

PubMed

Qi, Peng; Yu, Shu-quan; Zhang, Chao; Liang, Li-cheng; Che, Ji-lu

2015-12-01

In order to understand the pollution characteristics of heavy metals in surface water sediments of Yongkang, we analyzed the concentrations of 10 heavy metals including Ti, Cr, Mn, Co, Ni, Cu, Zn, As, Pb and Fe in 122 sediment samples, explored the underlying source of heavy metals and then assessed the potential ecological risks of those metals by methods of the index of geo-accumulation and the potential ecological risk. The study results showed that: 10 heavy metal contents followed the order: Fe > Ti > Mn > Zn > Cr > Cu > Ph > Ni > As > Co, all heavy metals except for Ti were 1. 17 to 3.78 times higher than those of Zhejiang Jinhua- Quzhou basin natural soils background values; The concentrations of all heavy metals had a significantly correlation between each other, indicating that those heavy metals had similar sources of pollution, and it mainly came from industrial and vehicle pollutions; The pollution extent of heavy metals in sediments by geo-accumulation index (Igeo) followed the order: Cr > Zn > Ni > Cu > Fe > As > Pb >Mn > Ti, thereinto, Cr, Zn, Cu and Ni were moderately polluted or heavily polluted at some sampling sites; The potential ecological risk of 9 heavy metals in sediments were in the following order: Cu > As > Ni > Cr > Pb > Co > Zn > Mn > Ti, Cu and As contributed the most to the total potential ecological risk, accounting for 22.84% and 21. 62% , others had a total of 55.54% , through the ecological risk assessment, 89. 34% of the potential ecological risk indexes ( RI) were low and 10. 66% were higher. The contamination level of heavy metals in Yongkang was slight in total, but was heavy in local areas.

The Elemental Composition of Demospongiae from the Red Sea, Gulf of Aqaba

PubMed Central

Mayzel, Boaz; Aizenberg, Joanna; Ilan, Micha

2014-01-01

Trace elements are vital for the growth and development of all organisms. Little is known about the elemental content and trace metal biology of Red Sea demosponges. This study establishes an initial database of sponge elemental content. It provides the necessary foundation for further research of the mechanisms used by sponges to regulate the uptake, accumulation, and storage of metals. The metal content of 16 common sponge species was determined using ICP measurements. A combination of statistical methods was used to determine the correlations between the metals and detect species with significantly high or low concentrations of these metals. Bioaccumulation factors were calculated to compare sponge metal content to local sediment. Theonella swinhoei contained an extremely high concentration of arsenic and barium, much higher (at least 200 times) than all other species and local sediment. Hyrtios erecta had significantly higher concentration of Al, Cr, Fe, Mn, Ti and V than all other species. This is due to sediment accumulation and inclusion in the skeleton fibers of this sponge species. Suberites clavatus was found to contain significantly higher concentration of Cd, Co, Ni and Zn than all other species and local sediment, indicating active accumulation of these metals. It also has the second highest Fe concentration, but without the comparably high concentrations of Al, Mn and Ti that are evident in H. erecta and in local sediment. These differences indicate active uptake and accumulation of Fe in S. clavatus, this was also noted in Niphates rowi. A significantly higher B concentration was found in Crella cyatophora compared to all other species. These results indicate specific roles of trace elements in certain sponge species that deserve further analysis. They also serve as a baseline to monitor the effects of anthropogenic disturbances on Eilat's coral reefs. PMID:24759635

Mineralogical and Geochemical Analyses of Antarctic Lake Sediments: A Reflectance and Moessbauer Spectroscopy Study with Applications for Remote Sensing on Mars

NASA Technical Reports Server (NTRS)

Froeschl, Heinz; Lougear, Andre; Trautwein, Alfred X.; Newton, Jason; Doran, Peter T.; Koerner, Wilfried; Koeberl, Christian; Bishop, Janice (Technical Monitor); DeVincenzi, Donald L. (Technical Monitor)

2000-01-01

Lakebottom sediments from the Dry Valleys region of Antarctica have been analyzed here in order to study the influence of water chemistry on the mineralogy and geochemistry of these sediments, as well as to evaluate techniques for remote spectral identification of potential biomarker minerals on Mars. Lakes from the Dry Valleys region of Antarctica have been investigated as possible analogs for extinct lake environments on early Mars. Sediment cores were collected in the present study from perennially ice-covered Lake Hoare in the Taylor Valley. These sediments were taken from a core in an oxic region of the lake and another core in an anoxic zone. Differences between the two cores were observed in the sediment color, Fe(II)/Fe(III) ratio, the presence of pyrite, the abundance of Fe, S and some trace elements, and the C, N and S isotope fractionation patterns. The results of visible-infrared reflectance spectroscopy (0.3-25 microns) Mossbauer spectroscopy (77 and 4 K) and X-ray diffraction are combined to determine the mineralogy and composition of these samples. The sediments are dominated by plagioclase, K-feldspar, quartz and pyroxene. Algal mats grow on the bottom of the lake and organic material has been found throughout the cores. Calcite is abundant in some layers of the aerobic core (shallow region) and pyrite is abundant in some layers of the anaerobic core (deep region). Analysis of the spectroscopic features due to organics and carbonates with respect to the abundance of organic C and carbonate contents was performed in order to select optimal spectral bands for remote identification of these components in planetary regoliths. Carbonate bands near 4 and 6.8 microns (approx.2500 and 1500/cm) were detected for carbonate abundances as low as 0.1 wt.% CO2. Organic features at 3.38, 3.42 and 3.51 microns (2960, 2925 and 2850/cm) were detected for organic C abundances as low as 0.06 wt.% C. The d13C trends show a more complex organic history for the anaerobic sediments than for the aerobic sediments. The biogenic pyrite found in the anaerobic core is associated with lighter d34S values and high organic C levels and could be used as a biomarker mineral for paleolakes on Mars.

Analysis of heavy metals from water, sediment, and tissues of Labeo angra (Hamilton, 1822), from an Ox-box lake- an wetland site from Assam, India.

PubMed

Das, Suchismita; Choudhury, Shamim Sultana

2016-01-01

The aim of this study was to assess the regional impacts of heavy metals (Mn, Fe, Mg, Ca, Cu, Zn, Cd, Cr, Pb and Ni) on water, sediment and a native, teleost fish species, Labeo angra, inhabiting a flood plain wetland of Barak River in Assam, India. Heavy metal concentrations in the water, sediments and fish were measured; bioaccumulation factor, metal pollution index as well as condition indices were calculated, to assess the pollution load and health status of the fish. Multivariate statistical analysis was used on wetland water and sediment heavy metals to ascertain the possible sources and seasonal variations of the pollutants. Results showed that most heavy metals in the wetland water and sediments exceeded the water (drinking and irrigation) and sediment quality guidelines, respectively. Seasonal variations were observed for geogenic heavy metals, Mn, Fe, Mg and Ca while no seasonal variations were observed for anthropogenic heavy metals, Cu, Cd, Cr, Pb and Ni. Multivariate statistical analysis showed that there was strong correlation between geogenic and anthropogenic heavy metals in water and sediment, both originating from the common anthropogenic sources. Accumulation of most of the metals in all the tissues was above the safe limits as recommended by the Food and Agriculture Organization. High bioaccumulation factors and metal pollution index for these metals in the different tissues revealed that metals were extensively bio-accumulated and bioconcentrated. Condition indices in fish from the wetland suggested metabolic abnormalities.

Selenate reduction to elemental selenium by anaerobic bacteria in sediments and culture: biogeochemical significance of a novel, sulfate-independent respiration

USGS Publications Warehouse

Oremland, Ronald S.; Hollibaugh, James T.; Maest, Ann S.; Presser, Theresa S.; Miller, Laurence G.; Culbertson, Charles W.

1989-01-01

Interstitial water profiles of SeO42−, SeO32−, SO42−, and Cl− in anoxic sediments indicated removal of the seleno-oxyanions by a near-surface process unrelated to sulfate reduction. In sediment slurry experiments, a complete reductive removal of SeO42− occurred under anaerobic conditions, was more rapid with H2 or acetate, and was inhibited by O2, NO3−, MnO2, or autoclaving but not by SO42− or FeOOH. Oxidation of acetate in sediments could be coupled to selenate but not to molybdate. Reduction of selenate to elemental selenium was determined to be the mechanism for loss from solution. Selenate reduction was inhibited by tungstate and chromate but not by molybdate. A small quantity of the elemental selenium precipitated into sediments from solution could be resolublized by oxidation with either nitrate or FeOOH, but not with MnO2. A bacterium isolated from estuarine sediments demonstrated selenate-dependent growth on acetate, forming elemental selenium and carbon dioxide as respiratory end products. These results indicate that dissimilatory selenate reduction to elemental selenium is the major sink for selenium oxyanions in anoxic sediments. In addition, they suggest application as a treatment process for removing selenium oxyanions from wastewaters and also offer an explanation for the presence of selenite in oxic waters.

Basis for paleoenvironmental interpretation of magnetic properties of sediment from Upper Klamath Lake (Oregon): Effects of weathering and mineralogical sorting

USGS Publications Warehouse

Rosenbaum, J.G.; Reynolds, R.L.

2004-01-01

Studies of magnetic properties enable reconstruction of environmental conditions that affected magnetic minerals incorporated in sediments from Upper Klamath Lake. Analyses of stream sediment samples from throughout the catchment of Upper Klamath Lake show that alteration of Fe-oxide minerals during subaerial chemical weathering of basic volcanic rocks has significantly changed magnetic properties of surficial deposits. Titanomagnetite, which is abundant both as phenocrysts and as microcrystals in fresh volcanic rocks, is progressively destroyed during weathering. Because fine-grained magnetite is readily altered due to large surface-to-volume ratios, weathering causes an increase in average magnetic grain size as well as reduction in the quantity of titanomagnetite both absolutely and relative to hematite. Hydrodynamic mineralogical sorting also produces differences in magnetic properties among rock and mineral grains of differing sizes. Importantly, removal of coarse silicate and Fe-oxide grains by sorting concentrated extremely fine-grained magnetite in the resulting sediment. The effects of weathering and sorting of minerals cannot be completely separated. These processes combine to produce the magnetic properties of a non-glacial lithic component of Upper Klamath Lake sediments, which is characterized by relatively low magnetite content and coarse magnetic grain size. Hydrodynamic sorting alone causes significant differences between the magnetic properties of glacial flour in lake sediments and of fresh volcanic rocks in the catchment. In comparison to source volcanic rocks, glacial flour in the lake sediment is highly enriched in extremely fine-grained magnetite.

Conditions affecting the release of phosphorus from surface lake sediments.

PubMed

Christophoridis, Christophoros; Fytianos, Konstantinos

2006-01-01

Laboratory studies were conducted to determine the effect of pH and redox conditions, as well as the effect of Fe, Mn, Ca, Al, and organic matter, on the release of ortho-phosphates in lake sediments taken from Lakes Koronia and Volvi (Northern Greece). Results were evaluated in combination with experiments to determine P fractionation in the sediment. The study revealed the major effect of redox potential and pH on the release of P from lake sediments. Both lakes showed increased release rates under reductive conditions and high pH values. The fractionation experiments revealed increased mobility of the reductive P fraction as well as of the NaOH-P fraction, indicating participation of both fractions in the overall release of sediment-bound P, depending on the prevailing environmental conditions. The results were assessed in combination with the release patterns of Fe, Mn, Ca, Al, and organic matter, enabling the identification of more specific processes of P release for each lake. The basic release patterns included the redox induced reductive dissolution of P-bearing metal oxides and the competitive exchange of phosphate anions with OH- at high pH values. The formation of an oxidized surface microlayer under oxic conditions acted as a protective film, preventing further P release from the sediments of Lake Volvi, while sediments from Lake Koronia exhibited a continuous and increased tendency to release P under various physicochemical conditions, acting as a constant source of internal P loading.

Microbial transformations of arsenic: Mobilization from glauconitic sediments to water

USGS Publications Warehouse

Mumford, Adam C.; Barringer, Julia L.; Benzel, William M.; Reilly, Pamela A.; Young, L.Y.

2012-01-01

In the Inner Coastal Plain of New Jersey, arsenic (As) is released from glauconitic sediment to carbon- and nutrient-rich shallow groundwater. This As-rich groundwater discharges to a major area stream. We hypothesize that microbes play an active role in the mobilization of As from glauconitic subsurface sediments into groundwater in the Inner Coastal Plain of New Jersey. We have examined the potential impact of microbial activity on the mobilization of arsenic from subsurface sediments into the groundwater at a site on Crosswicks Creek in southern New Jersey. The As contents of sediments 33–90 cm below the streambed were found to range from 15 to 26.4 mg/kg, with siderite forming at depth. Groundwater beneath the streambed contains As at concentrations up to 89 μg/L. Microcosms developed from site sediments released 23 μg/L of As, and active microbial reduction of As(V) was observed in microcosms developed from site groundwater. DNA extracted from site sediments was amplified with primers for the 16S rRNA gene and the arsenate respiratory reductase gene, arrA, and indicated the presence of a diverse anaerobic microbial community, as well as the presence of potential arsenic-reducing bacteria. In addition, high iron (Fe) concentrations in groundwater and the presence of iron-reducing microbial genera suggests that Fe reduction in minerals may provide an additional mechanism for release of associated As, while arsenic-reducing microorganisms may serve to enhance the mobility of As in groundwater at this site.

Denitrification activity is closely linked to the total ambient Fe concentration in mangrove sediments of Goa, India

NASA Astrophysics Data System (ADS)

Fernandes, Sheryl Oliveira; Gonsalves, Maria-Judith; Michotey, Valérie D.; Bonin, Patricia C.; Loka, A.; Bharathi, P.

2013-10-01

Denitrification activity (DNT) and associated environmental parameters were examined in two mangrove ecosystems of Goa, India - the relatively unimpacted Tuvem and the anthropogenically-influenced Divar. Sampling was carried out at every 2 cm interval within the 0-10 cm depth range to determine (1) seasonal (pre-monsoon, monsoon and post-monsoon) down-core variation in DNT (2) assess the environmental factors influencing the DNT and (3) to build predictive models for benthic DNT. Denitrification generally decreased with depth and showed marked seasonal variation at both the locations. Denitrification peaked during the pre-monsoon occurring at a rate of up to 21.00 ± 12.84 nmol N2O g-1 h-1 within 0-4 cm at both the locations. Further, DNT at pre-monsoon was significantly influenced by Fe content at Tuvem and Divar suggesting Fe-mediated nitrate respiration. The influence of other limiting substrates such as NO3- and NO2- was most important during the monsoon and post-monsoon especially at Divar. The multiple regression models developed could predict 67-98% of the observed variability in DNT through the seasons. About 6-9 environmental variables were required to relatively well-predict DNT in these sediments with the complexity governing DNT decreasing from pre-monsoon to post-monsoon. Our results reveal that seasonal dynamics of DNT in tropical mangrove sediments are closely linked to the total Fe at the prevailing ambient concentration in both the systems.

Assessing the mechanisms controlling the mobilization of arsenic in the arsenic contaminated shallow alluvial aquifer in the blackfoot disease endemic area.

PubMed

Liao, Vivian Hsiu-Chuan; Chu, Yu-Ju; Su, Yu-Chen; Lin, Po-Cheng; Hwang, Yaw-Huei; Liu, Chen-Wuing; Liao, Chung-Min; Chang, Fi-John; Yu, Chan-Wei

2011-12-15

High levels of arsenic in groundwater and drinking water represent a major health problem worldwide. Drinking arsenic-contaminated groundwater is a likely cause of blackfoot disease (BFD) in Taiwan, but mechanisms controlling the mobilization of arsenic present at elevated concentrations within aquifers remain understudied. Microcosm experiments using sediments from arsenic contaminated shallow alluvial aquifers in the blackfoot disease endemic area showed simultaneous microbial reduction of Fe(III) and As(V). Significant soluble Fe(II) (0.23±0.03 mM) in pore waters and mobilization of As(III) (206.7±21.2 nM) occurred during the first week. Aqueous Fe(II) and As(III) respectively reached concentrations of 0.27±0.01 mM and 571.4±63.3 nM after 8 weeks. We also showed that the addition of acetate caused a further increase in aqueous Fe(II) but the dissolved arsenic did not increase. We further isolated an As(V)-reducing bacterium native to aquifer sediments which showed that the direct enzymatic reduction of As(V) to the potentially more-soluble As(III) in pore water is possible in this aquifer. Our results provide evidence that microorganisms can mediate the release of sedimentary arsenic to groundwater in this region and the capacity for arsenic release was not limited by the availability of electron donors in the sediments. Copyright © 2011 Elsevier B.V. All rights reserved.

Total and labile metals in surface sediments of the tropical river-estuary system of Marabasco (Pacific coast of Mexico): Influence of an iron mine.

PubMed

Marmolejo-Rodríguez, Ana Judith; Prego, Ricardo; Meyer-Willerer, Alejandro; Shumilin, Evgueni; Cobelo-García, Antonio

2007-01-01

Marabasco is a tropical river-estuary system comprising the Marabasco river and the Barra de Navidad Lagoon. The river is impacted by the Peña Colorada iron mine, which produces 3.5 million tons of pellets per year. Thirteen surface sediment samples were collected in May 2005 (dry season) in order to establish background levels of Al, Cd, Co, Cu, Fe, Ni, Pb, and Zn in the system and to ascertain the potential mobility of metals in the sediments. Analyses were carried out in the fraction finer than 63 microm, and labile metals extracted according the BCR procedure. Certified reference materials were used for validation of methods. Total concentrations of Cd, Co, Cu, Ni, Pb, and Zn were in the range of 0.05-0.34, 6-95, 0.7-31, 9-26, 2-18, and 53-179 mgkg(-1), respectively; Al and Fe ranges of 24-127, and 26-69 mgg(-1) correspondingly. Cadmium was found to be significantly labile in the sediments (20-100%), followed by Co (0-35%), Ni (3-16%) and Zn (0-25%), whereas the labile fraction for Cu, Fe and Pb was almost negligible (<4%). According with the total metal concentrations, background levels and normalised enrichment factors (NEF) of the metals studied, the impact of the Peña Colorada iron mine on the Marabasco system is lower than expected when compared with other similar World systems influenced by mining activities.

Arsenic partitioning among particle-size fractions of mine wastes and stream sediments from cinnabar mining districts.

PubMed

Silva, Veronica; Loredo, Jorge; Fernández-Martínez, Rodolfo; Larios, Raquel; Ordóñez, Almudena; Gómez, Belén; Rucandio, Isabel

2014-10-01

Tailings from abandoned mercury mines represent an important pollution source by metals and metalloids. Mercury mining in Asturias (north-western Spain) has been carried out since Roman times until the 1970s. Specific and non-specific arsenic minerals are present in the paragenesis of the Hg ore deposit. As a result of intensive mining operations, waste materials contain high concentrations of As, which can be geochemically dispersed throughout surrounding areas. Arsenic accumulation, mobility and availability in soils and sediments are strongly affected by the association of As with solid phases and granular size composition. The objective of this study was to examine phase associations of As in the fine grain size subsamples of mine wastes (La Soterraña mine site) and stream sediments heavily affected by acid mine drainage (Los Rueldos mine site). An arsenic-selective sequential procedure, which categorizes As content into seven phase associations, was applied. In spite of a higher As accumulation in the finest particle-size subsamples, As fractionation did not seem to depend on grain size since similar distribution profiles were obtained for the studied granulometric fractions. The presence of As was relatively low in the most mobile forms in both sites. As was predominantly linked to short-range ordered Fe oxyhydroxides, coprecipitated with Fe and partially with Al oxyhydroxides and associated with structural material in mine waste samples. As incorporated into short-range ordered Fe oxyhydroxides was the predominant fraction at sediment samples, representing more than 80% of total As.

Immobilization of mercury in field soil and sediment using carboxymethyl cellulose stabilized iron sulfide nanoparticles

NASA Astrophysics Data System (ADS)

Gong, Yanyan; Liu, Yuanyuan; Xiong, Zhong; Kaback, Dawn; Zhao, Dongye

2012-07-01

Mercury (Hg) is one of the most pervasive and bio-accumulative metals in the environment. Yet, effective in situ remediation technologies have been lacking. This study investigated the effectiveness of a class of soil-deliverable FeS nanoparticles for in situ immobilization of Hg in two field-contaminated soils from a New Jersey site and one sediment from an Alabama site. The nanoparticles were prepared using sodium carboxymethyl cellulose (CMC) as a stabilizer. Transmission electron microscopy measurements revealed a particle size of 34.3 ± 8.3 nm (standard deviation), whereas dynamic light scattering gave a hydrodynamic diameter of 222.5 ± 3.2 nm. Batch tests showed that at an FeS-to-Hg molar ratio of 28:1-118:1, the nanoparticles reduced water-leachable Hg by 79%-96% and the TCLP (toxicity characteristic leaching procedure) based leachability by 26%-96%. Column breakthrough tests indicated that the nanoparticles were deliverable in the sediment/soil columns under moderate injection pressure. However, once the external pressure was removed, the delivered nanoparticles remained virtually mobile under typical groundwater flow conditions. When the Hg-contaminated soil and sediment were treated with 52-95 pore volumes of a 500 mg l-1 FeS nanoparticle suspension, water-leachable Hg was reduced by 90%-93% and TCLP-leachable Hg was reduced by 65%-91%. The results warrant further field demonstration of this promising in situ remediation technology.

Arsenic release by indigenous bacteria Bacillus cereus from aquifer sediments at Datong Basin, northern China

NASA Astrophysics Data System (ADS)

Xie, Zuoming; Wang, Yanxin; Duan, Mengyu; Xie, Xianjun; Su, Chunli

2011-03-01

Endemic arsenic poisoning due to long-term drinking of high arsenic groundwater has been reported in Datong Basin, northern China. To investigate the effects of microbial activities on arsenic mobilization in contaminated aquifers, Bacillus cereus ( B. cereus) isolated from high arsenic aquifer sediments of the basin was used in our microcosm experiments. The arsenic concentration in the treatment with both bacteria and sodium citrate or glucose had a rapid increase in the first 18 d, and then, it declined. Supplemented with bacteria only, the concentration could increase on the second day. By contrast, the arsenic concentration in the treatment supplemented with sodium citrate or glucose was kept very low. These results indicate that bacterial activities promoted the release of arsenic in the sediments. Bacterial activities also influenced other geochemical parameters of the aqueous phase, such as pH, Eh, and the concentrations of dissolved Fe, Mn, and Al that are important controls on arsenic release. The removal of Fe, Mn, and Al from sediment samples was observed with the presence of B. cereus. The effects of microbial activities on Fe, Mn, and Al release were nearly the same as those on As mobilization. The pH values of the treatments inoculated with bacteria were lower than those without bacteria, still at alkaline levels. With the decrease of Eh values in treatments inoculated with bacteria, the microcosms became more reducing and are thus favorable for arsenic release.

Hexavalent Chromium Generation within Naturally Structured Soils and Sediments

DOE PAGES

Hausladen, Debra M.; Fendorf, Scott

2017-01-13

Chromium(VI) produced from the oxidation of indigenous Cr(III) minerals is increasingly being recognized as a threat to groundwater quality. A critical determinant of Cr(VI) generation within soils and sediments is the necessary interaction of two low-solubility phases$-$Cr(III) silicates or (hydr)oxides and Mn(III/IV) oxides—that lead to its production. Here in this paper, we investigate the potential for Cr(III) oxidation by Mn oxides within fixed solid matrices common to soils and sediments. Artificial aggregates were constructed from Cr(OH) 3- and Cr 0.25Fe 0.75(OH) 3-coated quartz grains and either mixed with synthetic birnessite or inoculated with the Mn(II)-oxidizing bacterium Leptothrix cholodnii. In aggregatesmore » simulating low organic carbon environments, we observe Cr(VI) concentrations within advecting solutes at levels more than twenty-times the California drinking water standard. Chromium(VI) production is highly dependent on Cr-mineral solubility; increasing Fe-substitution (x = 0 to x = 0.75) decreases the solubility of the solid and concomitantly decreases total Cr(VI) generation by 37%. In environments with high organic carbon, reducing conditions within aggregate cores (microbially) generate sufficient Fe(II) to suppress Cr(VI) efflux. Our results illustrate Cr(VI) generation from reaction with Mn oxides within structured media simulating soils and sediments and provide insight into how fluctuating hydrologic and redox conditions impact coupled processes controlling Cr and Mn cycling.« less

Hexavalent Chromium Generation within Naturally Structured Soils and Sediments

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

Hausladen, Debra M.; Fendorf, Scott

Chromium(VI) produced from the oxidation of indigenous Cr(III) minerals is increasingly being recognized as a threat to groundwater quality. A critical determinant of Cr(VI) generation within soils and sediments is the necessary interaction of two low-solubility phases$-$Cr(III) silicates or (hydr)oxides and Mn(III/IV) oxides—that lead to its production. Here in this paper, we investigate the potential for Cr(III) oxidation by Mn oxides within fixed solid matrices common to soils and sediments. Artificial aggregates were constructed from Cr(OH) 3- and Cr 0.25Fe 0.75(OH) 3-coated quartz grains and either mixed with synthetic birnessite or inoculated with the Mn(II)-oxidizing bacterium Leptothrix cholodnii. In aggregatesmore » simulating low organic carbon environments, we observe Cr(VI) concentrations within advecting solutes at levels more than twenty-times the California drinking water standard. Chromium(VI) production is highly dependent on Cr-mineral solubility; increasing Fe-substitution (x = 0 to x = 0.75) decreases the solubility of the solid and concomitantly decreases total Cr(VI) generation by 37%. In environments with high organic carbon, reducing conditions within aggregate cores (microbially) generate sufficient Fe(II) to suppress Cr(VI) efflux. Our results illustrate Cr(VI) generation from reaction with Mn oxides within structured media simulating soils and sediments and provide insight into how fluctuating hydrologic and redox conditions impact coupled processes controlling Cr and Mn cycling.« less

Influence of seasonal variation and anthropogenic activity on phosphorus cycling and retention in mangrove sediments: A case study in China

NASA Astrophysics Data System (ADS)

Jiang, Shan; Lu, Haoliang; Liu, Jingchun; Lin, Yushan; Dai, Minyue; Yan, Chongling

2018-03-01

Mangroves are known for sequestering and storing large quantities of phosphorus (P) within their sediments. In the present study, the sediment P cycle (including phosphatase activity intensity, total sedimentary P, P fractions distinguished by a sequential extraction method, as well as diffusion-adsorption processes) in a mangrove swamp in a subtropical estuary in China was studied. In the spring, the acid phosphatase activity varied between 1.3 and 1.9 units in the four sites in the estuary. The activity of alkaline phosphatase varied from 0.8 to 1.4 units. The total sedimentary P ranged from 821 to 1689 mg kg-1 with a dominance of redox-sensitive (Fe/Al bound) P. In the autumn, activities of both phosphatases and the total sediment P amount increased, probably due to enhanced inputs of organic matter and Fe oxides. In addition to seasonal variation, P in the mangrove sediment was influenced by anthropogenic activities. In particular, redox-sensitive P decreased significantly while phosphatase activity increased in the site that was flushed with aquaculture pond effluents. In contrast, sediment P enrichment was observed in the site that received domestic sewage. Both sources of anthropogenic P increased the eutrophication risk of the mangrove sediment because of a decrease in the amount of P adsorption and an enhancement of P release via diffusion. Diesel contamination due to the presence of a dock depressed phosphatase activity in the surficial sediment. The overlap between seasonal rhythm and human influences may introduce significant variations in P cycling, which warrants further attention from coastal management.

Microbially-induced Fe and Mn oxides in condensed pelagic sediments (Middle-Upper Jurassic, Western Sicily)

NASA Astrophysics Data System (ADS)

Préat, A.; Mamet, B.; Di Stefano, P.; Martire, L.; Kolo, K.

2011-06-01

This article presents a petrographic comparison of the Rosso Ammonitico facies of Western Sicily and the original Rosso Ammonitico Veronese of Northern Italy based on a total of 27 sections. The Rosso Ammonitico has been the subject of numerous controversies that range from bathyal to shallow-water platform sedimentation. Therefore it seemed interesting to verify if the term Rosso Ammonitico has the same geologic connotation from region to region. The Middle-Upper Jurassic Rosso Ammonitico of Western Sicily is a condensed succession formed during a period of extensional synsedimentary tectonics related to the spreading of the Ionian Ocean. Slope-to-basin or pelagic carbonate deposits characterize the sedimentation which consists of reddish mudstones and wackestones. The abundant fauna is composed of radiolarians, protoglobigerinids, Saccocoma, Bositra associated with ammonites. A few ferruginous hardgrounds, Fe-Mn oxide crusts and Mn-coated condensation horizons are also present. The red matrices contain abundant Fe-Mn encrusted, microbored and bioeroded bioclasts. Sporadic Fe-Mn oncolites composed of amorphous Mn-minerals and goethite are also conspicuous. The matrix, as well as the shells and the fillings of the complex associated veinlets, are frequently altered into calcite microsparite. Submicronic iron bacterial and fungal filaments associated with mineralized extracellular polymeric substances (EPS) are observed in the matrix. They record dysaerobic microenvironments at or near the sediment-water interfaces. Early mineralized discontinuities enhanced by subsequent pressure dissolution are reported in the succession. Mn-(Ni) bacterial filaments are exceptionally observed in the cortex of the Fe-Mn oncolites. As a consequence of an early lithification, the Mn filaments are poorly preserved. The pigmentation of the rock is due to the dispersion of submicronic oxyhydroxides (now goethite and amorphous iron) formed by bacterial mediation during early diagenesis in microaerophilitic environments. As in the case of the original 'Rosso Ammonitico Veronese', Fe and Mn bacteria/fungi were able to produce bioconstructions which have no bathymetric significance. The limiting factor must have been the oxygen content which was low in these very quiet and relatively deep environments. Thus the Rosso Ammonitico of northern and southern Italy have a number of points in common, but some obvious dissimilarities are observed that explain some of the various sedimentological interpretations. Among them, the chemical composition is of particular importance, more Fe is present in Veneto (Northern Italy) while Mn is associated with the Sicilian Rosso Ammonitico. The Sicilian localities were more proximal to oceanic magmatic sources which were related to the activity of the oceanic crust.

Diversity of the Sediment Microbial Community in the Aha Watershed (Southwest China) in Response to Acid Mine Drainage Pollution Gradients.

PubMed

Sun, Weimin; Xiao, Tangfu; Sun, Min; Dong, Yiran; Ning, Zengping; Xiao, Enzong; Tang, Song; Li, Jiwei

2015-08-01

Located in southwest China, the Aha watershed is continually contaminated by acid mine drainage (AMD) produced from upstream abandoned coal mines. The watershed is fed by creeks with elevated concentrations of aqueous Fe (total Fe > 1 g/liter) and SO4 (2-) (>6 g/liter). AMD contamination gradually decreases throughout downstream rivers and reservoirs, creating an AMD pollution gradient which has led to a suite of biogeochemical processes along the watershed. In this study, sediment samples were collected along the AMD pollution sites for geochemical and microbial community analyses. High-throughput sequencing found various bacteria associated with microbial Fe and S cycling within the watershed and AMD-impacted creek. A large proportion of Fe- and S-metabolizing bacteria were detected in this watershed. The dominant Fe- and S-metabolizing bacteria were identified as microorganisms belonging to the genera Metallibacterium, Aciditerrimonas, Halomonas, Shewanella, Ferrovum, Alicyclobacillus, and Syntrophobacter. Among them, Halomonas, Aciditerrimonas, Metallibacterium, and Shewanella have previously only rarely been detected in AMD-contaminated environments. In addition, the microbial community structures changed along the watershed with different magnitudes of AMD pollution. Moreover, the canonical correspondence analysis suggested that temperature, pH, total Fe, sulfate, and redox potentials (Eh) were significant factors that structured the microbial community compositions along the Aha watershed. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

Post Gold King Mine Spill Investigation of Metal Stability in Water and Sediments of the Animas River Watershed.

PubMed

Rodriguez-Freire, Lucia; Avasarala, Sumant; Ali, Abdul-Mehdi S; Agnew, Diane; Hoover, Joseph H; Artyushkova, Kateryna; Latta, Drew E; Peterson, Eric J; Lewis, Johnnye; Crossey, Laura J; Brearley, Adrian J; Cerrato, José M

2016-11-01

We applied spectroscopy, microscopy, diffraction, and aqueous chemistry methods to investigate the persistence of metals in water and sediments from the Animas River 13 days after the Gold King Mine spill (August 5, 2015). The Upper Animas River watershed, located in San Juan Colorado, is heavily mineralized and impacted by acid mine drainage, with low pH water and elevated metal concentrations in sediments (108.4 ± 1.8 mg kg -1 Pb, 32.4 ± 0.5 mg kg -1 Cu, 729.6 ± 5.7 mg kg -1 Zn, and 51 314.6 ± 295.4 mg kg -1 Fe). Phosphate and nitrogen species were detected in water and sediment samples from Farmington, New Mexico, an intensive agricultural area downstream from the Animas River, while metal concentrations were low compared to those observed upstream. Solid-phase analyses of sediments suggest that Pb, Cu, and Zn are associated with metal-bearing jarosite and other minerals (e.g., clays, Fe-(oxy)hydroxides). The solubility of jarosite at near-neutral pH and biogeochemical processes occurring downstream could affect the stability of metal-bearing minerals in river sediments. This study contributes relevant information about the association of metal mixtures in a heavy mineralized semiarid region, providing a foundation to better understand long-term metal release in a public and agricultural water supply.

Spatial distribution and potential biological risk of some metals in relation to granulometric content in core sediments from Chilika Lake, India.

PubMed

Barik, Saroja K; Muduli, Pradipta R; Mohanty, Bita; Rath, Prasanta; Samanta, Srikanta

2018-01-01

The article presents first systematic report on the concentration of selected major elements [iron (Fe) and manganese (Mn)] and minor elements [zinc (Zn), copper (Cu), chromium (Cr), lead (Pb), nickel (Ni), and cobalt (Co)] from the core sediment of Chilika Lake, India. The analyzed samples revealed higher content of Pb than the background levels in the entire study area. The extent of contamination from minor and major elements is expressed by assessing (i) the metal enrichments in the sediment through the calculations of anthropogenic factor (AF), pollution load index (PLI), Enrichment factor (EF), and geoaccumulation index (Igeo) and (ii) potential biological risks by the use of sediment quality guidelines like effect range median (ERM) and effect range low (ERL) benchmarks. The estimated indices indicated that sediment is enriched with Pb, Ni, Cr, Cu and Co. The enrichment of these elements seems to be due to the fine granulometric characteristics of the sediment with Fe and Mn oxyhydroxides being the main metal carriers and fishing boats using low grade paints, fuel, and fishing technology using lead beads fixed to fishing nets. Trace element input to the Chilika lake needs to be monitored with due emphasis on Cr and Pb contaminations since the ERM and ERL benchmarks indicated potential biological risk with these metals.

Maghemite-to-magnetite reduction across the Fe-redox boundary in a sediment core from the Ontong-Java Plateau: influence on relative palaeointensity estimation and environmental magnetic application

NASA Astrophysics Data System (ADS)

Yamazaki, Toshitsugu; Solheid, Peter

2011-06-01

During reduction diagenesis, production of dissolved Fe2+ by reduction of ferric oxide starts at the Fe-redox boundary. The associated magnetic property changes may influence palaeomagnetic and environmental magnetic records of marine sediments, however, this has not been evaluated thoroughly. In this study, using a gravity core from the Ontong-Java Plateau, we document in detail rock magnetic changes across the Fe-redox boundary, and investigate their influence on relative palaeointensity estimation and on a magnetic proxy for the proportion of terrigenous/biogenic magnetic minerals. The magnetic mineral assemblage above the Fe-redox boundary is characterized by a component with a mean coercivity of ˜100 mT in isothermal remanent magnetization (IRM) component analyses and low S-ratios (S-0.1T). Low-temperature IRM measurements and Mössbauer spectroscopy indicate that the degree of maghemitization is higher above the Fe-redox boundary. From these observations, we conclude that reduction of maghemite to magnetite occurs at the Fe-redox boundary, and we infer that a maghemite skin on magnetic grains is lost across the boundary. Relative palaeointensity variations obtained by normalizing NRM intensity with SIRM agree well with regional and global palaeointensity stacks, which suggests that relative palaeointensity estimation is not significantly affected by the Fe-redox boundary. Temporal variations of the ratio of anhysteretic remanent magnetization susceptibility and saturation IRM (χARM/SIRM) coincide with the regional pattern across the Ontong-Java Plateau. It is also possible to estimate variations in the proportion of terrigenous to biogenic components using the χARM/SIRM ratio across the Fe-redox boundary.

The fate of nitrogen is linked to iron(II) availability in a freshwater lake sediment

NASA Astrophysics Data System (ADS)

Robertson, Elizabeth K.; Thamdrup, Bo

2017-05-01

The fate of nitrogen in natural environments is controlled by anaerobic nitrate-reducing processes by which nitrogen is removed as N2 or retained as NH4+. These processes can potentially be driven by oxidation of reduced inorganic compounds at oxic-anoxic interfaces. Several studies have investigated the use of Fe2+ as an electron donor in nitrate reduction in bacterial cultures, however current information on this process in the environment is sparse. We aimed to determine whether nitrate-reducing processes in the freshwater Lake Almind (Silkeborg, Denmark) were linked to Fe2+ oxidation. Anaerobic sediment slurries were supplemented with 15N-substrates and electron donors (Fe2+ and/or acetate) to characterize nitrate-reducing processes under environmentally relevant substrate concentrations and at higher concentrations traditionally used in microbial enrichment studies. Dissimilatory nitrate reduction to ammonium, DNRA, was stimulated by Fe2+ addition in 7 of 10 slurry experiments and in some cases, denitrification was concomitantly reduced. The determined kinetic parameters (Vmax and Km) for Fe2+-driven DNRA were 4.7 μmol N L-1 d-1 and 33.8 μmol Fe2+ L-1, respectively and reaction stoichiometry for Fe2+:NH4+ (8.2:1) was consistent with that of predicted stoichiometry (8:1). Conversely, under enrichment conditions, denitrification was greatly increased while DNRA rates remained unchanged. Increased Fe2+ concentrations may be exploited by DNRA organisms and have an inhibitory effect on denitrification, thus Fe2+ may play a role in regulating N transformations in Lake Almind. Furthermore, we suggest enrichment conditions may promote the adaptation or change of microbial communities to optimally utilize the available high substrate concentrations; misrepresenting metabolisms occurring in situ.

Merged digital aeromagnetic data for the middle Rio Grande and southern Espanola basins, New Mexico

USGS Publications Warehouse

Sweeney, Ronald E.; Grauch, V.J.S.; Phillips, Jeffrey D.

2002-01-01

The U. S. Geological Survey (USGS) recently conducted a multi-disciplinary study of the Middle Rio Grande basin (Bartolino and Cole, 2002; Fig. 1). The main purpose of this study was to gain a better multi-dimensional understanding of the basin's hydrogeologic framework and use this new understanding to construct an improved regional ground-water flow model. The Middle Rio Grande basin fill serves as the primary water resource for Albuquerque and surrounding communities (Thorn and others, 1993). It is composed of poorly consolidated, Tertiary to Quaternary sediments, collectively called the Santa Fe Group. These sediments were deposited during the Tertiary to Quaternary development of the Rio Grande rift (Fig. 1, inset). The strata vary in thickness from 1,000 to more than 4,000 m and range from mudstone to conglomerate (Kelley, 1977; May and Russell, 1994).

Improving sediment-quality guidelines for nickel: development and application of predictive bioavailability models to assess chronic toxicity of nickel in freshwater sediments

USGS Publications Warehouse

Vangheluwe, Marnix L. U.; Verdonck, Frederik A. M.; Besser, John M.; Brumbaugh, William G.; Ingersoll, Christopher G.; Schlekat, Christan E.; Rogevich Garman, Emily

2013-01-01

Within the framework of European Union chemical legislations an extensive data set on the chronic toxicity of sediment nickel has been generated. In the initial phase of testing, tests were conducted with 8 taxa of benthic invertebrates in 2 nickel-spiked sediments, including 1 reasonable worst-case sediment with low concentrations of acid-volatile sulfide (AVS) and total organic carbon. The following species were tested: amphipods (Hyalella azteca, Gammarus pseudolimnaeus), mayflies (Hexagenia sp.), oligochaetes (Tubifex tubifex, Lumbriculus variegatus), mussels (Lampsilis siliquoidea), and midges (Chironomus dilutus, Chironomus riparius). In the second phase, tests were conducted with the most sensitive species in 6 additional spiked sediments, thus generating chronic toxicity data for a total of 8 nickel-spiked sediments. A species sensitivity distribution was elaborated based on 10% effective concentrations yielding a threshold value of 94 mg Ni/kg dry weight under reasonable worst-case conditions. Data from all sediments were used to model predictive bioavailability relationships between chronic toxicity thresholds (20% effective concentrations) and AVS and Fe, and these models were used to derive site-specific sediment-quality criteria. Normalization of toxicity values reduced the intersediment variability in toxicity values significantly for the amphipod species Hyalella azteca and G. pseudolimnaeus, but these relationships were less clearly defined for the mayfly Hexagenia sp. Application of the models to prevailing local conditions resulted in threshold values ranging from 126 mg to 281 mg Ni/kg dry weight, based on the AVS model, and 143 mg to 265 mg Ni/kg dry weight, based on the Fe model

[Residues and potential ecological risk assessment of metal in sediments from lower reaches and estuary of Pearl River].

PubMed

Xie, Wen-Ping; Wang, Shao-Bing; Zhu, Xin-Ping; Chen, Kun-Ci; Pan, De-Bo; Hong, Xiao-You; Yin, Yi

2012-06-01

In order to investigate the heavy metal concentrations and their potential ecological risks in surface sediments of lower reaches and estuary of Pearl River, 21 bottom sediment samples were collected from lower reaches and estuary of Pearl River. Total contents of Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Cd, Sb, Pb and Hg in these samples were measured by the inductively coupled plasma mass spectrometry (ICP-MS) and the atomic fluorescence spectrometry (AFS) and using the index of geoaccumulation and the potential ecological risk index to evaluate the pollution degree of heavy metals in the sediments. Results indicated that the concentration of total Fe and total Mn were 41658.73 and 1104.73 mg x kg(-1) respectively and toxic trace metals, such as Cr, Co, Ni, Cu, Zn, As, Se, Cd, Sb, Pb and Hg were 86.62, 18.18, 54.10, 80.20, 543.60, 119.55, 4.28, 10.60, 20.26, 104.58 and 0.520 mg x kg(-1). The descending order of pollution degree of various metals is: Cd > As approximately Zn > Hg > Pb approximately Cu approximately Cr, while the single potential ecological risk followed the order: Cd > Hg > As > Cu > Pb > Zn > Cr. The pollution extent and potential ecological risk of Cd were the most serious among all heavy metals. The distribution pattern of Cd individual potential ecological risk indices is exactly the same as that of general potential ecological risk indices for all heavy metals. Clustering analysis indicates that the sampling stations may be classified into five groups which basically reflected the characteristics of the heavy metal contamination and sedimentation environments along the different river reaches in lower reaches and estuary of Pearl Rive. In general, the serious heavy metal pollution and the high potential ecological risk existed in three river reaches: Chengcun-Shawan, Chengcun-Shundegang and Waihai-Hutiaomen. The pollution degree and potential ecological risk are higher in related river reaches of Beijiang than that in other lower reaches and estuary of Pearl River.

Mineralogy and arsenic mobility in arsenic-rich Brazilian soils and sediments

USGS Publications Warehouse

de Mello, J.W.V.; Roy, W.R.; Talbott, J.L.; Stucki, J.W.

2006-01-01

Background. Soils and sediments in certain mining regions of Brazil contain an unusually large amount of arsenic (As), which raises concerns that mining could promote increased As mobility, and thereby increase the risks of contaminating water supplies. Objectives. The purpose of t his study was to identify the most important factors governing As mobility in sediments and soils near three gold-mining sites in the State of Minas Gerais, Brazil. Methods. Surface and sub-surface soil samples were collected at those sites and characterized by chemical and mineralogical analyses. Oxalate (Feo) and citrate-bicarbonate-dithionite (Fed) iron contents were determined by atomic absorption spectroscopy (AAS). Arsenic mobilization was measured after incubating the samples in a 2.5 mM CaCl2 solution under anaerobic conditions for 1, 28, 56, 84, or 112 days. The solution concentrations of As, Fe, and Mn were then measured by inductively coupled plasma-mass spectrometry (ICP-MS) and AAS, respectively. Results and Discussion. Results indicated that As mobilization is largely independent of both the total As and the Feo/Fed ratio of the solid phase. Soluble As is roughly controlled by the Fe (hydr)oxide content of the soil, but a closer examination of the data revealed the importance of other highly weathered clay minerals and organic matter. Large amounts of organic matter and a low iron oxide content should favor As leaching from soils and sediments. Under reducing conditions, As is mobilized by the reductive dissolution of Fe and/or Mn oxides. However, released As may be readsorbed depending on the sorptive properties of the soil. Gibbsite is particularly effective in adsorbing or readsorbing As, as is the remaining unreduced fraction of the iron (hydr)oxides. Conclusion and Outlook. In general, low soluble As is rel ated to the presence of gibbsite, a large amount of iron oxides, and a lack of organic matter in the solid phase. This has environmental significance because gibbsite is thermodynamically more stable than Fe oxides under anaerobic conditions, such as those found in waterlogged soils and lake sediments. ?? 2006 ecomed publishers (Verlagsgruppe Hu??thig Jehle Rehm GmbH), D-86899 Landsberg and Tokyo.

Redox Heterogenity in MORB

NASA Astrophysics Data System (ADS)

Cottrell, E.; Kelley, K. A.

2012-12-01

Mantle oxygen fugacity (fO2) has a first-order effect on the petrogenesis of mantle-derived melts and the speciation of mantle fluids. Current debate centers on the spatial uniformity of upper mantle fO2 and its constancy through geologic time. We use iron K-edge X-ray absorption near-edge structure (μXANES) spectroscopy to provide Fe3+ /ΣFe ratios of submarine mantle-derived basalts from mid-ocean ridges (MORB) as a proxy for fO2. A global survey of primitive (>8.75 wt% MgO) MORB glasses at spreading centers, unaffected by plumes, reveals a decrease in Fe3+ /ΣFe ratio of 12% relative with indices of mantle enrichment such as 87/86Sr, 208/204Pb, Ba/La, and Rb/Sr ratios. The strong negative correlation between upper mantle fO2 and enrichment recorded by MORB glasses contrasts with the positive relationship hinted at by abyssal peridotite oxybarometry (e.g. Ballhaus, CMP, 1993) and the general prediction of a positive correlation born of the expectation that Fe3+ can be treated as more incompatible than Fe2+ during mantle melting. These data unequivocally link upper mantle oxidation state to mantle source enrichment. EMORB generation is commonly attributed to subduction-related processes. That EMORB is more reduced than NMORB implies that deeply subducted and recycled lithologies, such as anoxic sediment, may be more reduced than ambient mantle. Negative correlations between traditional tracers of recycled sediment (e.g. +Nb anomaly, high 87/86Sr, high LILE/LREE) and redox support this hypothesis. Preservation of redox signatures on plate-recycling timescales of hundreds of millions to billions of years would require the mantle to be very poorly buffered. Alternatively, MORB Fe3+ /ΣFe ratios may be generated in situ beneath ridges as a function of variable carbon content. The shallow MORB source is too oxidized to stabilize graphite (Cottrell and Kelley, EPSL, 2011) and carbon exists as oxides. Decreasing fO2 with increasing depth eventually stabilizes reduced carbon species (diamond, carbides, alloys), however, and aCO2 may buffer mantle assemblages. Upon ascent, reduced carbon in upwelling mantle must oxidize, reducing Fe in the process such that more carbon-rich mantle would arrive at the surface with a lower Fe3+ /ΣFe ratio. We cannot directly correlate Fe3+ /ΣFe ratios with CO2 concentrations because submarine basalts have variably degassed CO2; however, the unequivocally carbon-rich sample 2πD43 (popping rock) does record a low Fe3+ /ΣFe ratio. CO2 variations on the order of 80 ppm in the mantle source would explain the range of MORB/EMORB Fe3+ /ΣFe ratios we observe, indicating a possible range of carbon concentrations in subduction-related lithologies. The relationships between MORB Fe3+ /ΣFe ratios, trace elements, and isotopes are consistent with modeled mixtures of depleted melts and low-degree carbonatitic melts of ancient subducted igneous crust plus 5-15% sediment (Stracke et al., G3, 2001) using the near-solidus carbonatitic partition coefficients of Dasgupta et al., Chem Geol, (2009). It may be that low degree carbonatitic melts even act through geologic time to scavenge and fractionate trace elements, creating enriched high-carbon reservoirs. Low Fe3+ /ΣFe ratios, and even EMORB itself, may therefore herald greater carbon concentrations, and the influence of low-degree carbonatitic melts, in Earth's mantle.

Heavy metal distribution in sediments from Calabar River, southeastern Nigeria

NASA Astrophysics Data System (ADS)

Ntekim, E. E. U.; Ekwere, S. J.; Ukpong, E. E.

1993-08-01

The concentration and areal distribution of selected metals (Pb, Zn, Cu, Cd, Ni, Fe, and Cr) in the sediments of the Calabar River were studied to determine the extent of anthropogenic input and to estimate the effects of dumping industrial waste materials into the river. The concentrations of Pb, Zn, and Cu indicate relatively moderate pollution mainly on the left-hand side of the river while Ni, Cr, Co, Cd, and Fe levels are below values found to have adverse effects on the lives of marine biota. High metal contents are found close to industrial establishments and so enhanced metal concentrations are related to industrial sewage and metal leaching from garbage and solid waste dumps.

The End of Monterey Submarine Canyon Incision and Potential River Source Areas-Os, Nd, and Pb Isotope Constraints from Hydrogenetic Fe-Mn Crusts

NASA Astrophysics Data System (ADS)

Conrad, T. A.; Nielsen, S.; Ehrenbrink, B. P. E.; Blusztajn, J.; Hein, J. R.; Paytan, A.

2015-12-01

The Monterey Canyon off central California is the largest submarine canyon off North America and is comparable in scale to the Grand Canyon. The age and history of the Monterey Canyon are poorly constrained due to thick sediment cover and sediment disruption from turbidity currents. To address this deficit we analyzed isotopic proxies (Os, Pb, Nd) from hydrogenetic ferromanganese (Fe-Mn) crusts, which grow over millions of years on elevated rock surfaces by precipitation of metals from seawater. Fe-Mn crusts were studied from Davidson Seamount near the base of the Monterey submarine fan, the Taney Seamount Chain, and from Hoss Seamount, which serves as a regional control (Fig.). Fe-Mn crusts were dated using Os isotope ratios compared to those that define the Cenozoic Os isotope seawater curve. Four Fe-Mn crust samples from Davidson and Taney Seamounts deviate from the Os isotopic seawater curve towards radiogenic values after 4.5±1 Ma. Osmium is well mixed in the global ocean and is not subject to significant diffusive reequilibration in Fe-Mn crusts. We therefore attribute deviations from the Os isotope seawater curve to large-scale terrestrial input that ended about 4.5±1 Ma. The two Davidson samples also show more radiogenic Nd isotope values from about 4.5±1 Ma. Lead isotopes in one Davidson Seamount crust, measured by LA-ICPMS, deviate from regional values after 4.5±1 Ma for about 500 ka towards terrestrial sources. The Taney Seamount Fe-Mn crust does not deviate from regional Nd nor Pb isotope values due to its greater distance from Monterey Canyon and the shorter marine residence times of Nd and Pb. Isotope plots of our crust data and compiled data for potential source rocks indicate that the river that carved Monterey Canyon carried sediment with values closer to the Sierra Nevada than to a Colorado Plateau source, with cessation of major riverine input occurring approximately 4.5±1 Ma, an age that we interpret as the end of the Monterey Canyon incision.

Characterizing the Fate and Mobility of Phosphorus in Utah Lake Sediments

NASA Astrophysics Data System (ADS)

Carling, G. T.; Randall, M.; Nelson, S.; Rey, K.; Hansen, N.; Bickmore, B.; Miller, T.

2017-12-01

An increasing number of lakes worldwide are impacted by eutrophication and harmful algal blooms due to anthropogenic nutrient inputs. Utah Lake is a unique eutrophic freshwater lake that is naturally shallow, turbid, and alkaline with high dissolved oxygen levels that has experienced severe algal blooms in recent years. Recently, the Utah Division of Water Quality has proposed a new limitation of phosphorus (P) loading to Utah Lake from wastewater treatment plants in an effort to mitigate eutrophication. However, reducing external P loads may not lead to immediate improvements in water quality due to the legacy pool of nutrients in lake sediments. The purpose of this study was to characterize the fate and mobility of P in Utah Lake sediments to better understand P cycling in this unique system. We analyzed P speciation, mineralogy, and binding capacity in lake sediment samples collected from 15 locations across Utah Lake. P concentrations in sediment ranged from 615 to 1894 ppm, with highest concentrations in Provo Bay near the major metropolitan area. Sequential leach tests indicate that 25-50% of P is associated with Ca (CaCO₃/ Ca10(PO4)6(OH,F,Cl)2 ≈ P) and 40-60% is associated with Fe (Fe(OOH) ≈ P). Ca-associated P was confirmed by SEM images, which showed the highest P concentrations correlating with Ca (carbonate minerals/apatite). The Ca-associated P fraction is likely immobile, but the Fe-bound P is potentially bioavailable under changing redox conditions. Batch sorption results indicate that lake sediments have a high capacity to absorb and remove P from the water column, with an average uptake of 70-96% removal over the range of 1-10 mg/L P. Mineral precipitation and sorption to bottom sediments is an efficient removal mechanism of P in Utah Lake, but a significant portion of P may be temporarily available for resuspension and cycling in surface waters. Mitigating lake eutrophication is a complex problem that goes beyond decreasing external nutrient loads to the water body and requires a better understanding in-lake P cycling.

The Geochemical Record of Cultural Eutrophication and Remediation Efforts in Three Connecticut Lakes

NASA Astrophysics Data System (ADS)

Ku, T.; Bourne, H. L.; Tirtajana, S.; Nahar, M.; Kading, T.

2009-12-01

Cultural eutrophication is the process whereby human activity increases the amount of nutrients, primarily nitrogen and phosphorous, entering an aquatic ecosystem causing excessive biological growth. To reverse or decelerate cultural eutrophication, many regulatory agencies have implemented stringent laws intended to lower the flux of nutrients into impacted water bodies or have emplaced internal remediation systems designed to decrease primary productivity. To quantify the effects of cultural eutrophication and remediation efforts, we examined sedimentary histories of three eutrophic Connecticut lakes that record the transition from pre-anthropogenic conditions into eutrophication and through recent remediation. The three Connecticut lakes (Lake Waramaug, Beseck Lake, and Amos Lake) represent a range of remediation activities. Since 1983, Lake Waramaug has been the focus of significant remediation efforts including the installation of three hypolimnetic withdrawal / layer aeration systems, zoning regulations to limit runoff, and the stocking and seeding of fish and zooplankton. Beseck Lake has experienced episodic eutrophic conditions, in part due to failing septic systems, and in 2001, 433 residences were converted from septic systems to a city sewer system. Amos Lake serves as a cultural eutrophication end member as it has not has received any major remediation. Multiple freeze and gravity cores were collected from 2005-2008. Radiocarbon, Pb-210, Cs-137, Hg, and Pb measurements determined sediment ages. Organic C accumulation rates, C/N ratios, organic matter delta-15N, bulk sediment Fe and Al concentrations, and P speciation (labile, iron-bound, aluminum-bound, organic, and total) determined sediment and nutrient sources and accumulations. Dithionite-extractable iron, pyrite S, and pyrite delta-34S provided insight into changes in P-Fe-S cycling. The sediment cores represent the last few hundreds of years of lake history and, importantly, some Lake Waramaug freeze cores preserved the sediments deposited after remediation efforts began. European settlement beginning in the 1700s caused an increase in total P and organic C sedimentation rates, a decrease in C/N, an increase in delta-15N, and an increase in allochthonous aluminosilicate sedimentation. The increase in delta-15N since the 1700s was caused the influx of high delta-15N sources such as agricultural fertilizers. In some Lake Waramaug cores, delta-15N has decreased in the last few decades, likely in response to new zoning laws, and demonstrates that remediation efforts have successfully altered nutrient inputs into the lake. Increased nutrient and aluminosilicate inputs during the 1800 and 1900s caused the dominant sediment P reservoir to shift from organic-P to Fe- or Al- bound P. In some cases, Fe-bound P decreased when pyrite S concentrations increased and d34S values decreased, suggesting that increased atmospheric sulfur inputs and subsequent pyritization has decreased the iron available to bind phosphorus. This work expands our knowledge of recovering aquatic systems and shows that recent sediment records may be used to measure the success of remediation strategies.

Enhanced cellular preservation by clay minerals in 1 billion-year-old lakes.

PubMed

Wacey, David; Saunders, Martin; Roberts, Malcolm; Menon, Sarath; Green, Leonard; Kong, Charlie; Culwick, Timothy; Strother, Paul; Brasier, Martin D

2014-07-28

Organic-walled microfossils provide the best insights into the composition and evolution of the biosphere through the first 80 percent of Earth history. The mechanism of microfossil preservation affects the quality of biological information retained and informs understanding of early Earth palaeo-environments. We here show that 1 billion-year-old microfossils from the non-marine Torridon Group are remarkably preserved by a combination of clay minerals and phosphate, with clay minerals providing the highest fidelity of preservation. Fe-rich clay mostly occurs in narrow zones in contact with cellular material and is interpreted as an early microbially-mediated phase enclosing and replacing the most labile biological material. K-rich clay occurs within and exterior to cell envelopes, forming where the supply of Fe had been exhausted. Clay minerals inter-finger with calcium phosphate that co-precipitated with the clays in the sub-oxic zone of the lake sediments. This type of preservation was favoured in sulfate-poor environments where Fe-silicate precipitation could outcompete Fe-sulfide formation. This work shows that clay minerals can provide an exceptionally high fidelity of microfossil preservation and extends the known geological range of this fossilization style by almost 500 Ma. It also suggests that the best-preserved microfossils of this time may be found in low-sulfate environments.

Enhanced cellular preservation by clay minerals in 1 billion-year-old lakes

PubMed Central

Wacey, David; Saunders, Martin; Roberts, Malcolm; Menon, Sarath; Green, Leonard; Kong, Charlie; Culwick, Timothy; Strother, Paul; Brasier, Martin D.

2014-01-01

Organic-walled microfossils provide the best insights into the composition and evolution of the biosphere through the first 80 percent of Earth history. The mechanism of microfossil preservation affects the quality of biological information retained and informs understanding of early Earth palaeo-environments. We here show that 1 billion-year-old microfossils from the non-marine Torridon Group are remarkably preserved by a combination of clay minerals and phosphate, with clay minerals providing the highest fidelity of preservation. Fe-rich clay mostly occurs in narrow zones in contact with cellular material and is interpreted as an early microbially-mediated phase enclosing and replacing the most labile biological material. K-rich clay occurs within and exterior to cell envelopes, forming where the supply of Fe had been exhausted. Clay minerals inter-finger with calcium phosphate that co-precipitated with the clays in the sub-oxic zone of the lake sediments. This type of preservation was favoured in sulfate-poor environments where Fe-silicate precipitation could outcompete Fe-sulfide formation. This work shows that clay minerals can provide an exceptionally high fidelity of microfossil preservation and extends the known geological range of this fossilization style by almost 500 Ma. It also suggests that the best-preserved microfossils of this time may be found in low-sulfate environments. PMID:25068404

Isotopic evidence for oxygenated Mesoarchaean shallow oceans

NASA Astrophysics Data System (ADS)

Eickmann, Benjamin; Hofmann, Axel; Wille, Martin; Bui, Thi Hao; Wing, Boswell A.; Schoenberg, Ronny

2018-02-01

Mass-independent fractionation of sulfur isotopes (MIF-S) in Archaean sediments results from photochemical processing of atmospheric sulfur species in an oxygen-depleted atmosphere. Geological preservation of MIF-S provides evidence for microbial sulfate reduction (MSR) in low-sulfate Paleoarchaean (3.8-3.2 billion years ago (Ga)) and Neoarchaean (2.8-2.5 Ga) oceans, but the significance of MSR in Mesoarchaean (3.2-2.8 Ga) oceans is less clear. Here we present multiple sulfur and iron isotope data of early diagenetic pyrites from 2.97-Gyr-old stromatolitic dolomites deposited in a tidal flat environment of the Nsuze Group, Pongola Supergroup, South Africa. We identified consistently negative Δ33S values in pyrite, which indicates photochemical reactions under anoxic atmospheric conditions, but large mass-dependent sulfur isotope fractionations of 30‰ in δ34S, identifying active MSR. Negative pyrite δ56Fe values (-1.31 to -0.88‰) record Fe oxidation in oxygen-bearing shallow oceans coupled with biogenic Fe reduction during diagenesis, consistent with the onset of local Fe cycling in oxygen oases 3.0 Ga. We therefore suggest the presence of oxygenated near-shore shallow-marine environments with ≥5 μM sulfate at this time, in spite of the clear presence of an overall reduced Mesoarchaean atmosphere.

Biogeochemical characteristics of Kuan-Tzu-Ling, Chung-Lun and Bao-Lai hot springs in southern Taiwan.

PubMed

Maity, Jyoti Prakash; Liu, Chia-Chuan; Nath, Bibhash; Bundschuh, Jochen; Kar, Sandeep; Jean, Jiin-Shuh; Bhattacharya, Prosun; Liu, Jiann-Hong; Atla, Shashi B; Chen, Chien-Yen

2011-01-01

Hot springs are the important natural sources of geothermally heated groundwater from the Earth's crust. Kuan-Tzu-Ling (KTL), Chung-Lun (CL) and Bao-Lai (BL) are well-known hot springs in southern Taiwan. Fluid and mud (sediments) samples were collected from the eruption points of three hot springs for detailed biogeochemical characterization. The fluid sample displays relatively high concentrations of Na(+) and Cl(-) compared with K(+), Mg(2+), Ca(2+), NO(2) (-), and SO(4) (2-), suggesting a possible marine origin. The concentrations of Fe, Cr, Mn, Ni, V and Zn were significantly higher in the mud sediments compared with fluids, whereas high concentrations of As, Ba, Cu, Se, Sr and Rb were observed in the fluids. This suggests that electronegative elements were released during sediment-water interactions. High As concentration in the fluids was observed to be associated with low redox (Eh) conditions. The FTIR spectra of the humic acid fractions of the sediments showed the presence of possible functional groups of secondary amines, ureas, urethanesm (amide), and silicon. The sulfate-reducing deltaproteobacterium 99% similar to Desulfovibrio psychrotolerans (GU329907) were rich in the CL hot spring while mesophilic, proteolytic, thiosulfate- and sulfur-reducing bacterium that 99% similar to Clostridium sulfidigenes (GU329908) were rich in the BL hot spring.

Trace Metal Distribution and Speciation in Pore Water of Hydrothermal Sediments From the Guaymas Basin, Gulf of California

NASA Astrophysics Data System (ADS)

Morales-Villafuerte, M.; Ortega-Osorio, A.; Wheat, G.; Seewald, J.

2004-12-01

Thirteen sediment cores were collected through out direct sampling with the MBARI/ ROV "Tiburon" in the southern trough of the Guaymas Basin in March 2003. Pore water samples from regular 2.5 cm intervals of sediment cores were extracted onboard by centrifugation. The supernatants were collected in clean polystyrene vials and stored at 4° C until analytical work on shore. Dissolved Fe, Mn, Cu, Pb, Zn and Ni concentrations in extracted fluid samples were analyzed by direct injection of atomic absorption spectrometry. Four zones in the hydrothermal field were classified according to their physical characteristics. A core located away from the influence of active vents was recovered as a background site. The second zone is characterized by low temperatures (4.2-80° C) and sediments saturated in hydrocarbons. Sulfides formation and higher temperatures (4-166° C) were observed in the third zone. Precipitation of carbonates on top of the sediment characterizes the fourth zone. Concentration of trace metals at the water-sediment interface appears to be the highest, probably due to metal precipitation from the hydrothermal plume, followed by diffusion into the pore water. A decrease in concentration is observed between 5-12 cm depth, suggesting that biological activity is consuming essential metals (zone of bioturbation). Metal concentrations in zones where sulfide phases are rich, exhibit smaller values in pore water (Fe=2.4-3.8 μ mol/kg, Cu=0.6-0.8 μ mol/kg, Pb=1.2-1.5 μ mol/kg, Zn=0.4-0.5 μ mol/kg and Ni= 3.4-4.4 μ mol/kg) relative to samples located at hydrocarbon sites (Fe= 2.7-11.4, Cu= 0.7-1.0 μ mol/kg, Pb= 1.2-2.2 μ mol/kg, Zn= 0.4-0.7 μ mol/kg and Ni= 3.4-5.2 μ mol/kg). At sulfide zones, pH and Eh conditions help to precipitate their stable sulfides as opposed to the hydrocarbon areas, where conditions are not favorable for sulfide formation due to the absence of H2S. In general, Fe concentrations in pore water are lower than that of Mn, very likely due to the easier precipitation and greater stability of FeS relative to MnS. As an attempt to reconstruct predominant species and their abundance in the system, aqueous chemical models were applied. The codes EQBRM and SUPCRT92 were run with total concentrations to calculate, concentrations, activity coefficients and thermodynamic properties of aqueous species. Experimental data such as total chloride, total sulfur and measured pH were used in the model. According to the prevailing conditions in the Guaymas Basin, all metals studied form chloride complexes. Iron, lead, and zinc exist mainly as hydroxy complexes, manganese as free ion and copper as CuHS. Speciation results are well supported by the Pearson's hard-soft rule which states that soft metal ion Cu++ bonds with soft bisulfide ligand, likewise, borderline metal ions as Fe2+, Mn2+, Pb2+ and Zn2+ bond with chloride, hydroxyl or water ligands. The results reported here provide a greater insight into the behavior of trace metals in pore waters of hydrothermal sediments.

Reoxidation of estuarine sediments during simulated resuspension events: Effects on nutrient and trace metal mobilisation

NASA Astrophysics Data System (ADS)

Vidal-Durà, Andrea; Burke, Ian T.; Stewart, Douglas I.; Mortimer, Robert J. G.

2018-07-01

Estuarine environments are considered to be nutrient buffer systems as they regulate the delivery of nutrients from rivers to the ocean. In the Humber Estuary (UK) seawater and freshwater mixing during tidal cycles leads to the mobilisation of oxic surface sediments (0-1 cm). However, less frequent seasonal events can also mobilise anoxic subsurface (5-10 cm) sediments, which may have further implications for the estuarine geochemistry. A series of batch experiments were carried out on surface and subsurface sediments taken from along the salinity gradient of the Humber Estuary. The aim was to investigate the geochemical processes driving major element (N, Fe, S, and Mn) redox cycling and trace metal behaviour during simulated resuspension events. The magnitude of major nutrient and metal release was significantly greater during the resuspension of outer estuarine sediments rather than from inner estuarine sediments. When comparing resuspension of surface versus subsurface sediment, only the outer estuary experiments showed significant differences in major nutrient behaviour with sediment depth. In general, any ammonium, manganese and trace metals (Cu and Zn) released during the resuspension experiments were rapidly removed from solution as new sorption sites (i.e. Fe/Mn oxyhydroxides) formed. Therefore Humber estuary sediments showed a scavenging capacity for these dissolved species and hence may act as an ultimate sink for these elements. Due to the larger aerial extent of the outer estuary intertidal mudflats in comparison with the inner estuary area, the mobilisation of the outer estuary sediments (more reducing and richer in sulphides and iron) may have a greater impact on the transport and cycling of nutrients and trace metals. Climate change-associated sea level rise combined with an increasing frequency of major storm events in temperate zones, which are more likely to mobilise deeper sediment regions, will impact the nutrient and metal inputs to the coastal waters, and therefore enhance the likelihood of eutrophication in this environment.

The environmental impacts of one of the largest tailing dam failures worldwide.

PubMed

Hatje, Vanessa; Pedreira, Rodrigo M A; de Rezende, Carlos Eduardo; Schettini, Carlos Augusto França; de Souza, Gabriel Cotrim; Marin, Danieli Canaver; Hackspacher, Peter Christian

2017-09-06

The impacts of the SAMARCO iron tailing spill along more than 650 km, between the dam and the plume of the Doce River in the Atlantic, were assessed by the determination of toxic metals. The tailing spill caused a substantial increase in suspended sediment loads (up to 33,000 mg L -1 ), in addition to large depositions of waste along the Doce basin. The highest estimated transport of dissolved metals was observed for Fe (58.8 μg s -1 ), Ba (37.9 μg s -1 ) and Al (25.0 μg s -1 ). Sediments reached the highest enrichment factors (EFs) for Hg (4,234), Co (133), Fe (43), and Ni (16), whereas As (55), Ba (64), Cr (16), Cu (17), Mn (41), Pb (38) and Zn (82) highest EFs were observed for suspended particulate matter (SPM). Iron, As, Hg, Mn exceeded sediment quality guidelines. Therefore, the risk of occurrence of adverse effects is highly possible, not only due to the dam failure, but also due to the Fe mining and the artisan Au mining. Heavy rain episodes will likely cause enhanced erosion, remobilization, and transport of contaminated particles, sustaining high inputs of SPM and metals for the years to come and threatening the ecosystem services.

Mineral ecophysiological evidence for biogeochemical cycles in 2461-2495 million year old banded iron formations (BIF).

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

Li, Y; Konhauser, Dr, Kurt; Cole, David

2011-01-01

The phosphorus composition of banded-iron formations (BIFs) has been used as a proxy for Precambrian seawater composition and the paleoeredox state of Earth's surface environment. However, it is unclear whether the phosphorus in BIFs originally entered the sediment as a sorbed component of the iron oxyhydroxide particles, or whether it was incorporated into the biomass of marine phytoplankton. We conducted high-resolution mineral analyses and report here the first detection of an Fe(III) acetate salt, as well as nanocrystals of apatite in association with magnetite, in the 2.48 Ga Dales Gorge Member of the Brockman Iron Formation (a BIF), Hamersley, Westernmore » Australia. The clusters of apatite are similar in size and morphology to biogenic apatite crystals resulting from biomass decay in Phanerozoic marine sediments, while the formation of an Fe(III) acetate salt and magnetite not only implies the original presence of biomass in the BIF sediments, but also that organic carbon likely served as an electron donor during bacterial Fe(III) reduction. This study is important because it suggests that phytoplankton may have played a key role in the transfer of phosphorus (and other trace elements) from the photic zone to the seafloor.« less

Potential for microbial H2 and metal transformations associated with novel bacteria and archaea in deep terrestrial subsurface sediments

PubMed Central

Hernsdorf, Alex W; Amano, Yuki; Miyakawa, Kazuya; Ise, Kotaro; Suzuki, Yohey; Anantharaman, Karthik; Probst, Alexander; Burstein, David; Thomas, Brian C; Banfield, Jillian F

2017-01-01

Geological sequestration in deep underground repositories is the prevailing proposed route for radioactive waste disposal. After the disposal of radioactive waste in the subsurface, H2 may be produced by corrosion of steel and, ultimately, radionuclides will be exposed to the surrounding environment. To evaluate the potential for microbial activities to impact disposal systems, we explored the microbial community structure and metabolic functions of a sediment-hosted ecosystem at the Horonobe Underground Research Laboratory, Hokkaido, Japan. Overall, we found that the ecosystem hosted organisms from diverse lineages, including many from the phyla that lack isolated representatives. The majority of organisms can metabolize H2, often via oxidative [NiFe] hydrogenases or electron-bifurcating [FeFe] hydrogenases that enable ferredoxin-based pathways, including the ion motive Rnf complex. Many organisms implicated in H2 metabolism are also predicted to catalyze carbon, nitrogen, iron and sulfur transformations. Notably, iron-based metabolism is predicted in a novel lineage of Actinobacteria and in a putative methane-oxidizing ANME-2d archaeon. We infer an ecological model that links microorganisms to sediment-derived resources and predict potential impacts of microbial activity on H2 consumption and retardation of radionuclide migration. PMID:28350393

Metal forms in sediments from Arctic coastal environments in Kandalaksha Bay, White Sea, under separation processes

NASA Astrophysics Data System (ADS)

Koukina, S. E.; Vetrov, A. A.

2013-09-01

This study focuses on sediments from small restricted exchange environments along the Karelian shore of Kandalaksha Bay (White Sea, Russian Arctic), which are known as separating basins and are characterised by contrasting oxidising conditions within the water column and the occurrence of anoxia. In the basins that were studied, no significant contamination by trace heavy metals (Pb, Cu, Zn and Cr, in particular) was detected. The comparative study of the two most bioavailable metal forms, namely, labile (acid soluble) and organically bound (alkali soluble) forms, indicated that acetic acid and sodium pyrophosphate released 3-11% and 2-12%, respectively, of the total metal content from sediments. The most bioavailable parts of metals are weakly bound to organic matter and, to a greater extent, associated with easily soluble amorphous Fe-oxides. Among the studied elements, most of the bioavailable Zn and Cu was most likely bound to organic substances, whereas bioavailable Cr and Mn were controlled to a greater extent by the formation of Fe-oxyhydroxide. The elements studied could be arranged in the following decreasing order of average potential bioavailability: Cu > Zn > Mn > Fe > Cr > Pb. In the separating basins, the relative proportion of labile bioavailable metals is enhanced in relation to the neighbouring open coastal sea.

Sedimentary environment and tectonic deformations of the Neoproterozoic Iron formation at the Wadi El-Dabbah greenstone sequence, Central Eastern Desert, Egypt

NASA Astrophysics Data System (ADS)

Kiyokawa, S.; Suzuki, T.; Ikehara, M.; Horie, K.; Takehara, M.; Abd-Elmonem, H.; Dawoud, A. D. M.; El-Hasan, M. M.

2017-12-01

El-Dabbah area Central Eastern Desert of the Nubia Shield preserved Neoproterozoic lower green schist faces volcaniclastics greenstone sequence and covered strike-slip deformation related subaerial sedimentary sequence (Hammamat Group). The volcaniclastics greenstone sequence (El-Dabbah Formation) preserved several iron beds bearing well stratified sequence. Four tectonic deformation identified as this area; thrust deformation (D1), strike-slip deformation with transtension normal fault and strong left-lateral shear (D2), subaerial pull apart sediments basin formed strike-slip deformations (D3), and extensional deformation after the Hammamat Group sedimentation (D4). New age data from intrusions identified about 638 Ma white granite and about 660 Ma quartz porphyry. Based on the detail mapping, we reconstruct more than 5000m thick volcano sedimentary succession. At least, 10 iron rich sections were identified within 3500m thick volcano-sedimentary sequence. There are 14 iron formation sequence identified in this greenstone sequence. Each Iron sequences are bedded with greenish-black shales within massive volcaniclastics and lava flow. Iron formation is formed mostly fine grain magnetite deposited within volcanic mudstone and siltstone with gradual distribution. Timing of this iron sediment is identified within Sturtian glaciation (730-700Ma). However, there is no geological direct support evidence in the Snowball earth event at this greenstone sequence. The volcanic activities at this ocean already produced many Fe2+ to ocean water. Repeated iron precipitation occur during volcanic activity interphase period which produced oxidation of iron and produce oxyhydroxide with mud-silt sediment at bottom of ocean.

Oxidation of Structural Fe(II) in Biotite by Lithotrophic Fe(II)-oxidizing microorganisms

NASA Astrophysics Data System (ADS)

Shelobolina, E.; Blöthe, M.; Xu, H.; Konishi, H.; Roden, E.

2008-12-01

The potential for microbial involvement in the oxidation of Fe(II)-bearing phyllosilicates is an understudied aspect of soil/sediment Fe biogeochemistry. An important property of structural Fe in Fe-bearing smectites is their ability to undergo multiple redox cycles without being mobilized. An obvious choice of mineral substrate for enumeration/isolation of Fe(II)-oxidizing microorganisms would be reduced smectite. But reduced smectite is readily oxidized by air. That is why biotite was chosen as a substrate for this study. In contrast to smectite, biotite is more stable in the presence of air, but incapable of redox cycling. Once Fe(II) is oxidized, biotite is weathered to expendable 2:1 phyllosilicates or kaolinite. First, we evaluated the ability of a neutral-pH lithoautotrophic nitrate-reducing enrichment culture (MPI culture), recovered by Straub et al (Appl. Environ. Microbiol., 1996, 62:1458-1460) from a freshwater ditch, to oxidize two different specimens of biotite. The culture was capable of multiple transfers in anaerobic nitrate-containing biotite suspensions. The growth of MPI culture resulted in decrease of 0.5 N HCl-extractable Fe(II) content and simultaneous nitrate reduction. Cell yields were comparable to those observed for other neutral-pH lithoautotrophic Fe(II)-oxidizing bacteria. High resolution TEM examination revealed structural and chemical changes at the edges of oxidized biotite and formation of reddish amorphous precipitates dominated by Si and Fe. To further evaluate efficiency of biotite for recovery of oxygen- and nitrate-dependent Fe(II) oxidizing cultures microbial enumeration study was performed using subsoil from a site near Madison, WI. The soil is rich in Fe-bearing smectite and shows evidence of redoximorphic features. The enumeration of Fe(II) oxidizing organisms from this sediment showed 10-fold higher efficiency of biotite over soluble Fe(II) for recovery of Fe(II)-oxidizers. Isolation and identification of both aerobic and nitrate-utilizing Fe(II)-oxidizing cultures is under way. This study demonstrates that biotite can be effectively used to recover and study microorganisms involved in the oxidative side of iron redox cycle in phyllosilicates. Our findings also indicate that microbial redox metabolism has the potential to vastly accelerate the oxidative weathering of otherwise relatively stable Fe(II)-bearing phyllosilicates.