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METHYLMERCURY OXIDATIVE DEGRADATION POTENTIALS IN CONTAMINATED ANDPRISTINE SEDIMENTS OF THE CARSON RIVER, NEVADA
Citation:
Oremland, R., L. Miller, P. Dowdle, T. Connell, AND T. Barkay. METHYLMERCURY OXIDATIVE DEGRADATION POTENTIALS IN CONTAMINATED ANDPRISTINE SEDIMENTS OF THE CARSON RIVER, NEVADA. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-95/570.
Description:
Sediments from mercury-contaminated and uncontaminated reaches of the Carson River, Nevada, were assayed for sulfate reduction, methanogenesis, denitrification, and monomethylmercury (MeHg) degradation. emethylation of "C-MeHg was detected at all sites as indicated by the formation of "CO, and "CR. xidative demethylation was indicated by the formation of "CO, and was present at significant levels in all samples. xidized/Reduced Demethylation Product (ORDP) ratios (i.e., "CO/14H4) generally ranged from 4.0 in surface layers to as low as 0.5 at depth. roduction of 14CO, was most pronounced at sediment surfaces which were zones of active denitrification and sulfate reduction but was also significant within zones of methanogenesis. n a core taken from an uncontaminated site having more oxidized, coarse-grained sediments, sulfate reduction and methanogenic activities were very low and 'CO, accounted for 98% of the product formed from "C-MeHg. here was no apparent relationship between the degree of mercury contamination of the sediments and the occurrence of oxidative demethylation. owever, sediments from Fort Churchill, the most contaminated site, were most active in terms of demethylation potentials. nhibition of sulfate reduction with molybdate resulted in significantly depressed ORDP ratios, but overall demethylation rates were comparable between inhibited and uninhibited samples. ddition of sulfate to sediment slurries stimulated production of "CO, from "C-MeHg, while 2-bromoethanesulfonic acid blocked production of "CR. hese results reveal the importance of sulfate reducing and methanogenic bacteria in oxidative demethylation of MeHg in anoxic environments.