Transformations of mercury species in the presence of Elbe river bacteria

Ebinghaus, Ralf; Wilken, Rolf‐Dieter

doi:10.1002/aoc.590070207

Cited by 23 publications

(5 citation statements)

References 16 publications

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“…The occurrence and bioavailability of mercury in sediments may be linked to the microbially mediated biotransformations (e.g., biomethylation) of this element (21,54,61). Although anaerobic conditions, sulfate-reducing bacteria, and cobalamin-mediated reactions are implicated in the methylation of mercury (9,12,13,15,27,28,33,53), these factors are not consistently correlated to the formation of methylmercury (12,13,15,54,67).…”

Section: Discussionmentioning

confidence: 99%

Anaerobic microflora of everglades sediments: effects of nutrients on population profiles and activities

Drake¹,

Aumen²,

Kuhner³

et al. 1996

Appl Environ Microbiol

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Everglades sediments (wetland soils) near sources of agricultural runoff had low redox potentials, were blackened with sulfide, and displayed high porewater phosphorus (total) concentrations and high water column conductivities. These sediments yielded 10 3-to 10 4-fold-higher numbers of culturable anaerobes, including methanogens, sulfate reducers, and acetate producers, than did sediments from Everglades and Lake Okeechobee comparative control sites not as directly associated with agricultural runoff. These observations demonstrated that there was a general, rather than specific, enhancement of the anaerobic microflora in the sediments most likely influenced by agricultural runoff. Despite these differences in microfloral patterns, methylmercury and total mercury levels were similar among these contrasting sediments. Although available sulfate and phosphorus appeared to stimulate the productivity of sulfate reducers in Everglades sediments, the number of culturable sulfate reducers did not directly correspond to the concentration of sulfate and phosphorus in porewaters. Microcosms supplemented with sulfate, nitrate, and phosphate altered the initial capacities of the sediment microflora to produce acetate and methane from endogenous matter. For sediments nearest sources of agricultural runoff, phosphorus temporarily enhanced acetate formation and initially suppressed methane production, sulfate enhanced acetate formation but did not significantly alter the production of methane, and nitrate totally suppressed the initial production of both methane and acetate. In regards to the latter, microbes capable of dissimilating nitrate to ammonium were present in greater culturable numbers than denitrifiers. In microcosms, acetate was a major source of methane, and supplemental hydrogen was directed towards the synthesis of acetate via CO 2-dependent acetogenesis. These findings demonstrate that Everglades sediments nearest agricultural runoff have enhanced anaerobic microbial profiles and that the anaerobic microflora are poised to respond rapidly to phosphate, sulfate, and nitrate input.

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Section: Discussionmentioning

confidence: 99%

Anaerobic microflora of everglades sediments: effects of nutrients on population profiles and activities

Drake¹,

Aumen²,

Kuhner³

et al. 1996

Appl Environ Microbiol

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“…Chen et al and Hammerschmidt et al suggested that this process may be occurring in the aqueous phase in the atmosphere. Abiotic methylation of Hg(II) , requires suitable methyl donors and, although available methyl donors may be products of biological processes such as organic compounds, methylation is still considered to be abiotic. , Some potential pathways of chemical methylation have been studied, such as the reaction of Hg(II) with fulvic and humic acids, acetic acid, methylmetals like methyltin or methyllead, − or small molecules such as methyl iodide. , …”

Section: Introductionmentioning

confidence: 99%

“…17,18 Some potential pathways of chemical methylation have been studied, such as the reaction of Hg(II) with fulvic and humic acids, 19 acetic acid, 20 methylmetals like methyltin or methyllead, 21À24 or small molecules such as methyl iodide. 22,25 The contribution of abiotic methylation pathways may have been overlooked in particular methylation involving Hg(0). Since Hg(0) is the dominant mercury specie in the troposphere, abiotic Hg(0) methylation might be an important pathway by which MeHg species are produced and dispersed globally.…”

Section: ' Introductionmentioning

confidence: 99%

A Theoretical Study of Abiotic Methylation Reactions of Gaseous Elemental Mercury by Halogen-Containing Molecules

et al. 2011

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Methylation reactions of gaseous elementary mercury by halogen containing molecules such as halogenomethane species CH(3)X (with X = Cl, Br, and I) and the dimethylchlorinium ion CH(3)ClCH(3)(+) were investigated at the density functional level. With CH(3)X, the reaction is predicted to be almost athermic and kinetically demanding for a thermal reaction. The reaction can proceed photochemically in the visible range; therefore sunlight may increase the reaction rate. These results compare well with the experimental data. Consecutive methylation of the CH(3)HgX products (with X = Cl, Br, and I) and subsequent formation of CH(3)HgCH(3) were also studied. These reactions are predicted to be kinetically inaccessible and thermodynamically unfavorable. With CH(3)ClCH(3)(+), the reaction is predicted to be athermic but kinetically easy. This is due to the suitability of the methyl transfer reagent. Geometrical and electronic data were systematically analyzed in order to rationalize the results.

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“…Present as a thiolate complex (likely with cysteine), methylmercury(II) represents up to 95% of total mercury in top predators. Methylation of Hg(II) by methyl iodide has been reported, in addition to methylation of various reduced forms of mercury . As part of our efforts to investigate rates and mechanisms of abiotic mercury methylation in natural waters, we undertook to examine the reaction of methyl iodide with Hg(II).…”

Section: Introductionmentioning

confidence: 99%

Kinetics and Mechanism of the Mercury(II)-Assisted Hydrolysis of Methyl Iodide

Celo

Scott

2005

Inorg. Chem.

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The kinetics and mechanism of the reaction of aqueous Hg(II) with methyl iodide have been investigated. The overall reaction is best described as Hg(II)-assisted hydrolysis, resulting in quantitative formation of methanol and, in the presence of excess methyl iodide, ultimately, HgI2 via the intermediate HgI+. The kinetics are biexponential when methyl iodide is in excess. At 25 degrees C, the acceleration provided by Hg2+ is 7.5 times greater than that caused by HgI+, while assistance of hydrolysis was not observed for HgI2. Thus, the reactions are not catalytic in Hg(II). The kinetics are consistent with an SN2-M+ mechanism involving electrophilic attack at iodide. As expected, methylation of mercury is not a reaction pathway; traces of methylmercury(II) are artifacts of the extraction/preconcentration procedure used for methylmercury analysis.

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Transformations of mercury species in the presence of Elbe river bacteria

Cited by 23 publications

References 16 publications

Anaerobic microflora of everglades sediments: effects of nutrients on population profiles and activities

Anaerobic microflora of everglades sediments: effects of nutrients on population profiles and activities

A Theoretical Study of Abiotic Methylation Reactions of Gaseous Elemental Mercury by Halogen-Containing Molecules

Kinetics and Mechanism of the Mercury(II)-Assisted Hydrolysis of Methyl Iodide

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