Bonding of methyl mercury to reduced sulfur groups in soil and stream organic matter as determined by x-ray absorption spectroscopy and binding affinity studies

Qian, Jin; Skyllberg, Ulf; Frech, Wolfgang; Bleam, William F.; Bloom, Paul R.; Petit, P.

doi:10.1016/s0016-7037(02)00974-2

Cited by 131 publications

(125 citation statements)

References 42 publications

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“…The concentration of RSH was estimated by assuming the ratio of RSH to DOC was 0.25 mass %. This value was based on the average measured bulk-phase organic S : organic C ratio in the sediment of our study site (from data in Table 5; , 0.16 mol S mol 21 C; , 4.2 mass %) and the assumptions that the ratio of reduced organic S to total organic S concentration is , 20 mass % (Ravichandran 2004) and that the ratio of thiol to total reduced organic sulfur concentration is , 30 mass % (Qian et al 2002). For example, a pore-water DOC concentration of 500 mmol L 21 (6 mg L 21 ) would yield an estimated RSH concentration of , 0.47 mmol L 21 (15 mg L 21 ).…”

Section: Methodsmentioning

confidence: 99%

Mercury and methylmercury cycling in sediments of the mid‐Atlantic continental shelf and slope

Hollweg

Gilmour

Mason

2010

Limnology & Oceanography

100

115

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We present a detailed study of the biogeochemical factors controlling mercury (Hg) distribution, methylmercury (MeHg) production, and MeHg efflux in sediments of the mid-Atlantic continental shelf and slope. The mildly reduced surface sediments of the shelf and slope provide ideal conditions for MeHg production. They are sufficiently reduced to support microbial sulfate reduction, but contain very low dissolved sulfide concentrations. The redox zonation of sediments determined the depth distribution of MeHg production, whereas the bioavailability of inorganic Hg for methylation appeared to be the dominant driver of spatial patterns across the shelf and slope. Sediment total Hg concentrations were well predicted by sediment organic matter (SOM) content, with the highest concentrations of Hg and MeHg in the fine-grained organic clays of the slope. However, SOM-normalized Hg concentrations decreased with distance from shore. The changing character of organic matter with distance from shore appeared to affect Hg partitioning and bioavailability for methylation. The percentage of Hg in sediments as MeHg was well predicted by measured methylation rates, but not by demethylation rates. On the basis of measured concentrations in bottom waters and surficial pore waters, the average diffusive efflux of Hg(II) and MeHg from sediments to coastal waters was estimated to be 26 and 0.8 pmol m 22 d 21 , respectively. Extrapolated globally, the diffusive input of MeHg from shelf and slope sediments is estimated to be 0.01 Mmol per year. As the actual fluxes can be substantially higher than diffusive fluxes, we suggest that shelf and upper slope sediments are a major source of MeHg to the coastal ocean.

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Section: Methodsmentioning

confidence: 99%

Mercury and methylmercury cycling in sediments of the mid‐Atlantic continental shelf and slope

Hollweg

Gilmour

Mason

2010

Limnology & Oceanography

100

115

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“…Recognition of the cross-linking structural role of the reduced S species shows that the organic C-S-C linkages are generated during humifi cation in the early stages of diagenesis, thus supporting the argument that humic substances are the precursors of source-rock kerogens. In other related S K-edge XANES studies, Jokic et al (2003) analyzed S speciation in wetland soils from Saskatchewan, and Qian et al (2002) found that methyl mercury, CH 3 Hg(II), preferentially forms complexes with reduced organic S groups of humic substances in northern soils and stream sediments. With the advent of high-brightness synchrotron-radiation beams, spatial mapping of S species is now possible.…”

Section: Organic Geochemistrymentioning

confidence: 95%

“…Differential reduction of organic S compounds to H 2 S does not identify the organic functional groups or the intermediate oxidation states of S. The pyrolysis -gas chromatography -mass spectrometry approach is used for coal, kerogens and aquatic humic substances, but is limited to speciation of thermally stable forms of S. Within this context, S K-and L-edge XANES spectroscopy are proving to be invaluable, non-destructive, and in some cases in situ, techniques for characterizing the S functional groups in natural organic matter. The method has been applied to coals (e.g., Hussain et al 1982, Spiro et al 1984, Huffman et al 1991, George et al 1991, Brown et al 1992, Kasrai et al 1990, 1996b, Olivella et al 2002, Huggins et al 1997, heavy petroleum asphalts (bitumens) and asphaltenes (George & Gorbaty 1989, Gorbaty et al 1991, Waldo et al 1991, Kasrai et al 1994, Vairavamurthy et al 1994, Sarret et al 1999, kerogens , Sarret et al 2002 and sediments, soils and humus (Vairavamurthy et al 1994, 1997, Morra et al 1997, Olivella et al 2002, Qian et al 2002, Beauchemin et al 2002, Solomon et al 2003, Jokic et al 2003. FIG.…”

Section: Organic Geochemistrymentioning

confidence: 99%

Xanes Spectroscopy of Sulfur in Earth Materials

Fleet¹

2005

The Canadian Mineralogist

148

134

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X-ray absorption near-edge structure (XANES) spectroscopy is the ideal non-destructive technique for characterizing and quantifying S species in compositionally complex natural materials such as silicate glasses and minerals, coals, asphalts and asphaltenes, kerogens and humic substances. Sulfur absorption edges represent the transition of S 1s and 2p core electrons to unoccupied antibonding orbitals at the bottom of the conduction band. Shifts in the position of the absorption-edge feature of S K-and L-edge XANES spectra constitute a chemical ruler for oxidation state of both inorganic and organic species of S; the S K edge shifts from 2469.5 eV for chalcopyrite (2-oxidation state) to 2482 eV for gypsum (6+). However, chemical state of S in Earth materials is most readily assigned by comparing the overall XANES profi le with spectra for reference compounds. Sulfur XANES spectra are reviewed for pyrite, troilite, pyrrhotite and NiAs-type Co 0.923 S and Ni 0.923 S, niningerite (MgS), oldhamite (CaS), alabandite (MnS) and cubic FeS, and sphalerite and related phases, as well as for selected solid-solutions of the monosulfi des. Sulfur XANES spectra for FeS, CoS, NiS, MgS, CaS, MnS and ZnS have been simulated by multiple scattering calculations. The S K-edge XANES of transition-metal-bearing monosulfi des generally show anomalous absorption consistent with hybridization of the fi nal S 3p * antibonding states with empty 3d orbitals on the metal atoms. Various applications of S K-and L-edge XANES fi ngerprinting are discussed, including speciation of inorganic S in basaltic glasses, lazurite and haüyne, identifi cation of organic functional groups of S in coals, kerogens and humic substances extracted from subtropical soils and marine sediments, and the association of sulfated sugars with calcifi cation of coral aragonite skeletons.Keywords: XANES spectroscopy, chemical state of S, electronic structure and bonding, sulfi des, sulfates, magma, organic geochemistry. SOMMAIRELa spectroscopie d'absorption des rayons X dans la région pré-seuil (XANES) s'avère la technique non-destructive par excellence pour caractériser et quantifi er les espèces de soufre dans les matériaux naturels de composition complexe, par exemple les verres silicatés et minéraux, charbons, asphaltes et asphaltènes, kérogènes et substances humiques. Les seuils d'absorption du soufre résultent de la transition des électrons 1s et 2p du noyau à des orbites non occupés anti-liaisons à la base de la bande de conduction. Les décalages dans la position des seuils K et L du soufre des spectres XANES constituent un barème chimique important dans l'évaluation du niveau d'oxydation du soufre, à la fois pour les espèces inorganiques et organiques; le seuil K est déplacé de 2469.5 eV dans la chalcopyrite (valence 2-) à 2482 eV dans le gypse (6+). Toutefois, l'état du soufre des matériaux terrestres est plus facilement attribué en comparant le profi l XANES entier d'un échantillon aux spectres des composés de réfé-rence. Les spectres XANES du soufre so...

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“…Furthermore, biogenic sulfide production under anaerobic conditions could promote reactions between sulfide and organic molecules, which form RSH groups, through what has been termed the "sulfurisation process" Mopper 1987, Eglinton et al 1994). Using methylmercury as a probe, Qian et al (2002) demonstrated that RSH groups comprised approximately 30% of the reduced organic S moieties (as determined by S XANES) in natural organic matter of soils and streams.…”

Section: Major S Species In Laboratory and Full-scale Cstbrsmentioning

confidence: 99%

Chemical speciation of sulfur and metals in biogas reactors – Implications for cobalt and nickel bio-uptake processes

Yekta

Skyllberg

Danielsson

et al. 2017

Journal of Hazardous Materials

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A balanced supply of micronutrients, including metals such as iron (Fe), cobalt (Co), and nickel (Ni), is required for the efficient and stable production of biogas. During biogas formation, the uptake of micronutrient metals by microorganisms is controlled by a complex network of biological and chemical reactions, in which reduced sulfur (S) compounds play a central role. This thesis addresses the interrelationship between the overall chemical speciation of S, Fe, Co, and Ni in relation to the metals bio-uptake processes. Laboratory continuous stirred tank biogas reactors (CSTBR) treating S-rich grain stillage, as well as a number full-scale CSTBRs treating sewage sludge and various combinations of organic wastes, termed codigestion, were considered. Sulfur speciation was evaluated using acid volatile sulfide (AVS) extraction and S X-ray absorption near edge structure (XANES). The chemical speciation of Fe, Co, and Ni was evaluated through the determination of aqueous metals and metal fractions pertaining to solid phases, as well as kinetic and thermodynamic analyses (chemical speciation modelling).The relative Fe to S content in biogas reactors, which in practice is regulated through the addition of Fe for the purpose of sulfide removal or prior to the anaerobic digestion of sewage sludge, is identified as a critical factor for the chemical speciation and bio-uptake of metals. In the reactors treating sewage sludge, the quantity of Fe exceeds that of S, inducing Fe(II)-dominated conditions under anaerobic conditions, while sulfide dominates in the co-digestion and laboratory reactors due to an excess of S over Fe. Under sulfide-dominated conditions, chemical speciation of the metals is regulated by hydrogen sulfide and the formation of metal sulfide precipitates, which in turn restrict the availability of metals for microorganisms. However, despite the limitations set by sulfide, aqueous concentrations of different Co and Ni species were shown to be sufficient to support metal acquisition by the microorganisms under sulfidic conditions. Comparatively, the concentrations of free metal ions and labile metalphosphate and -carbonate complexes in aqueous phase, which directly participate in bio-uptake processes, are higher under Fe-dominated conditions. This results in an enhanced metal adsorption on cell surfaces and faster bio-uptake rates. It is therefore suggested that the chemical speciation and potential bioavailability of metals may be controlled through adjustments of the influent Fe concentration in relation to S content. The results also indicated that the pool of metal sulfides in the biogas reactors could be regarded as a source of metals for microbial activities. Thus, the recovery and utilisation of this fraction of metals may be considered as a measure with which to minimise the metal dosing concentrations to CSTBRs.Keywords: Biogas, Anaerobic digestion, Chemical speciation, bio-uptake, Sulfur, Iron, Cobalt, Nickel SammanfattningFör att en effektiv och stabil biogasproduktion från organiskt a...

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Bonding of methyl mercury to reduced sulfur groups in soil and stream organic matter as determined by x-ray absorption spectroscopy and binding affinity studies

Cited by 131 publications

References 42 publications

Mercury and methylmercury cycling in sediments of the mid‐Atlantic continental shelf and slope

Mercury and methylmercury cycling in sediments of the mid‐Atlantic continental shelf and slope

Xanes Spectroscopy of Sulfur in Earth Materials

Chemical speciation of sulfur and metals in biogas reactors – Implications for cobalt and nickel bio-uptake processes

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