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Mercury pathways in the carson river—lahontan reservoir system, nevada, usa
Author(s) -
Bonzongo JeanClaude J.,
Lyons W. Berry,
Heim Kenneth J.,
Chen Y Uan,
Warwick John J.,
Miller Glenn C.,
Lechler Paul J.
Publication year - 1996
Publication title -
environmental toxicology and chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.1
H-Index - 171
eISSN - 1552-8618
pISSN - 0730-7268
DOI - 10.1002/etc.5620150510
Subject(s) - mercury (programming language) , environmental chemistry , methylmercury , hypolimnion , surface water , anoxic waters , hydrology (agriculture) , sediment , snowmelt , environmental science , surface runoff , chemistry , geology , bioaccumulation , eutrophication , ecology , environmental engineering , paleontology , geotechnical engineering , organic chemistry , nutrient , computer science , programming language , biology
Concentrations of mercury (Hg) were determined in surface waters and associated river bank sediment samples in a river—reservoir system contaminated by mine wastes. The distribution of total and methyl Hg in surface waters along the Carson River was similar to that measured in river bank sediments and influenced by flow regimes. High levels of Hg (up to 7,585 and 7.2 ng Hg/L for total and methyl Hg, respectively) determined on surface water samples were in large part discharged from Hg‐contaminated tailings, distributed in the river bank sediments. Once introduced into the river during the spring snowmelt runoff, Hg was transported downstream and accumulated in the lacustrine part of the system. Elemental Hg (Hg 0 ) increased from 0.02 ng/L in the noncontaminated region to about 2 ng/L in the reservoir. The vertical distribution of total methylmercury (MeHg T ) in water of the reservoir differs from that observed elsewhere, in both Hg‐contaminated and noncontaminated lakes. The highest levels of MeHg T (<1 ng/L as Hg) and acid‐reactive Hg (4 ng/L) were observed in the alkaline and oxic surface waters. The decrease of pH with depth and the absence of oxygen in depth >10 m did not enhance MeHg production. In the anoxic hypolimnion of the reservoir, the recycling of MeHg T was more influenced by the redox cycling of Mn. The addition of group VI anions (SeO 2− 4 , MoO 2− 4 , and WO 2− 4 ) in the range of concentrations of oxyanion‐forming elements found in the Carson River system to anoxic sediment slurry spiked with SO 2− 4 resulted in the reduction of rates of MeHg production. Their negative effect on MeHg production was enhanced by increasing pH. Group VI anions, analogous to SO 2− 4 are inhibitory to sulfate‐reducing bacteria, which are known to play a key role in MeHg production in anoxic sediments. Accordingly, the particular water geochemistry of the Carson River system could partly explain the observed low levels of MeHg where one would expect higher concentrations.