Methylmercury oxidative degradation potentials in contaminated and pristine sediments of the Carson River, Nevada
Journal Article
·
· Applied and Environmental Microbiology
OSTI ID:102599
- Geological Survey, Menlo Park, CA (United States); and others
Sediments from mercury-contaminated and uncontaminated reaches of the Carson River, Nevada, were assayed for sulfate reduction, methanogenesis, denitrification, and monomethylmercury (MeHg) degradation. Demethylation of ({sup 14}C)MeHg was detected at all sites as indicated by the formation of {sup 14}CO{sub 2} and {sup 14}CH{sub 4}. Oxidative demethylation was indicated by the formation of {sup 14}CO{sub 2} and was present at significant levels in all samples. Oxidized/reduced demethylation product ratios (i.e., {sup 14}CO{sub 2}/{sup 14}CH{sub 4} ratios) generally ranged from 4.0 in surface layers to as low as 0.5 at depth. Production of {sup 14}CO{sub 2} was most pronounced at sediment surfaces which were zones of active denitrification and sulfate reduction but was also significant within zones of methanogenesis. In a core taken from an uncontaminated site having a high proportion of oxidized, coarse-grain sediments, sulfate reduction and methanogenic activity levels very low and {sup 14}CO{sub 2} accounted for 98% of the product formed from ({sup 14}C)MeHg. There as no apparent relationship between the degree of mercury contamination of the sediments and the occurrence of oxidative demethylation. However, sediments from Fort Churchill, the most contaminated site, were most active in terms of demethylation potentials. Inhibition of sulfate reduction with molybdate resulted in significantly depressed oxidized/reduced demethylation product ratios, but overall demethylation rates of inhibited and uninhibited samples were comparable. Addition of sulfate to sediment slurries stimulated production of {sup 14}CO{sub 2} from ({sup 14}C)MeHg, while 2-bromoethanesulfonic acid blocked production of {sup 14}CH{sub 4}. These results reveal the importance of sulfate-reducing and methanogenic bacteria in oxidative demethylation of MeHg in anoxic environments. 58 refs., 6 figs., 3 tabs.
- OSTI ID:
- 102599
- Journal Information:
- Applied and Environmental Microbiology, Journal Name: Applied and Environmental Microbiology Journal Issue: 7 Vol. 61; ISSN AEMIDF; ISSN 0099-2240
- Country of Publication:
- United States
- Language:
- English
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