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| Titel |
Biogeochemical factors affecting mercury methylation rate in two contaminated floodplain soils |
| VerfasserIn |
T. Frohne, J. Rinklebe, U. Langer, G. Laing, S. Mothes, R. Wennrich |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 1 ; Nr. 9, no. 1 (2012-01-26), S.493-507 |
| Datensatznummer |
250006678
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| Publikation (Nr.) |
 copernicus.org/bg-9-493-2012.pdf |
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| Zusammenfassung |
| An automated biogeochemical microcosm system allowing controlled variation
of redox potential (EH) in soil suspensions was used to assess the
effect of various factors on the mobility of mercury (Hg) as well as on the
methylation of Hg in two contaminated floodplain soils with different Hg
concentrations (approximately 5 mg Hg kg−1 and
>30 mg Hg kg–1). The experiment was conducted under stepwise variation from reducing
(approximately −350 mV at pH 5) to oxidizing conditions (approximately
600 mV at pH 5). Results of phospholipid fatty acids (PLFA) analysis indicate
the occurrence of sulfate reducing bacteria (SRB) such as Desulfobacter species (10Me16:0,
cy17:0, 10Me18:0, cy19:0) or Desulfovibrio species (18:2ω6,9), which are considered
to promote Hg methylation. The products of the methylation process are
lipophilic, highly toxic methyl mercury species such as the monomethyl
mercury ion [MeHg+], which is named as MeHg here. The ln(MeHg/Hgt)
ratio is assumed to reflect the net production of monomethyl mercury
normalized to total dissolved Hg (Hgt) concentration. This ratio
increases with rising dissolved organic carbon (DOC) to Hgt ratio
(ln(DOC/Hgt) ratio) (R2 = 0.39, p<0.0001, n= 63) whereas the
relation between ln(MeHg/Hgt ratio and lnDOC is weaker (R2 =
0.09; p<0.05; n = 63). In conclusion, the DOC/Hgt ratio might be a
more important factor for the Hg net methylation than DOC alone in the
current study. Redox variations seem to affect the biogeochemical behavior
of dissolved inorganic Hg species and MeHg indirectly through related
changes in DOC, sulfur cycle, and microbial community structure whereas
EH and pH values, as well as concentration of dissolved
Fe3+/Fe2+ and Cl– seem to play subordinate roles in Hg
mobilization and methylation under our experimental conditions. |
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