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Mercury investigations in the Walker River Basin, Nevada
Date Posted: January 17, 2003Elevated mercury concentrations were discovered by staff of the BioDiversity Research Institute in the blood of common loons that use Walker Lake in western Nevada during both spring and fall migration. Service Contaminants staff were uncertain as to the source of the mercury because fish from Walker Lake are not known to have highly elevated concentrations of mercury. However, mercury amalgamation was used to recover gold and silver from ores during the late 1800's at mines in the basin, so it was possible that Walker Lake was the source of the mercury. Therefore, in 1999 and 2000 additional sampling of fish from Walker Lake was conducted. The U.S. Geological Survey, Water Resources Division collected water and sediment samples throughout the Walker River basin and Service staff collected aquatic invertebrates and fish from similar sites in an effort to locate mercury sources and determine the degree of contamination. Mercury residues in sediment and aquatic invertebrates were found to be elevated downstream from several abandoned mine sites. The concentrations in some sediment samples were high enough to potentially cause adverse effects to aquatic invertebrates. Mercury residues in fish from Walker Lake of the size consumed by common loons were generally low, but were much higher for somewhat larger fish; however, other evidence still points to Walker Lake as a significant source of mercury to the loons. Service staff will work with various Federal and State agencies and other partners that deal with abandoned mine land issues to further pinpoint sources of mercury in an effort to cleanup contaminated sites.