Mercury levels in the Carson River and effect of group VI anions on methylmercury production in sediments
Conference
·
OSTI ID:214864
- Univ. of Nevada, Reno, NV (United States); and others
Distribution and speciation of Hg were determined in a fluvial-lacustrine system impacted by Hg-contaminated mine wastes. Levels of total-Hg (THg), introduced into the river by contaminated particles eroded from mine tailings, were found to be controlled by the water flow regimes and varying from background concentrations of {approximately}2 ng L{sup -1} to values in the ppb range in the contaminated section. Concentrations of MeHg were higher in surface waters of both the contaminated river section (>7 ng Hg L{sup -1}) and the reservoir (11 to 4 ng Hg L{sup -1}), than in the seasonally anoxic bottom waters of the reservoir (<1 ng Hg L{sup -1}). The Carson River flows in to the and basin of eastern California and western Nevada, where the rivers are essentially Ca-Na-HCO{sub 3} waters with the terminal lakes being Na-Cl-CO{sub 3} waters. Due to the evapoconcentration of water as it flows downstream in this and environment, levels of naturally occurring oxyanion-forming elements (such as Mo, W, Se,{hor_ellipsis}) known to influence sulfate reduction, are high for noncontaminated freshwaters, exhibiting their highest values in terminal basins. In contrast, MeHg/THg ratios decreased significantly with the increase downstream of oxyanion-forming element concentrations. Experimental results of Hg methylation conducted with sediments showed that combined to alkaline pH (>7.4) and high levels of inorganic Hg, the production of MeHg in the studied aquatic system, mainly by sulfate reducing bacteria, could be negatively affected by some group VI anions, since they could interfere in metabolic processes involving both phosphate and sulfate.
- OSTI ID:
- 214864
- Report Number(s):
- CONF-950801--
- Country of Publication:
- United States
- Language:
- English
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