ABSTRACT
APPROVED FOR PUBLICATION BY THE DIRECTOR OF THE U.S. GEOLOGICAL SURVEY
To be presented at the national meeting of the Society of Environmental Toxicology and Chemistry (SETAC), to be held November 16-20, 2002 in Salt Lake City, Utah
Mercury Bioaccumulation from Historical Mining in the Trinity River Watershed, California
Jason T. May*, U.S. Geological Survey, Sacramento, CA, Roger L. Hothem, U.S. Geological Survey, Davis, CA; Walter G. Duffy, U. S. Geological Survey, Arcata, CA; Charles N. Alpers, U.S. Geological Survey, Sacramento, CA; James J. Rytuba, U.S. Geological Survey, Menlo Park, CA.
Historical gold and mercury mining operations in the Trinity River watershed
continue to release mercury to downstream water bodies. To evaluate the extent
of mercury contamination in the watershed, the U.S. Geological Survey collected
game fish during 2000-2001 from sites in the Trinity River watershed: 4 locations
within Trinity Lake, 11 stream sites, and 3 pond sites. Samples of amphibians
and predaceous aquatic insects were also collected from select sites. Concentrations
of total mercury (Hg) were determined in fish tissue (fillets), amphibian carcasses,
and composites of predaceous aquatic insects. Additionally, methylmercury/total
mercury ratios were determined for predaceous aquatic insects. Total mercury
in 69 black bass (Micropterus spp.) ranged from 0.12 to 1.22 parts per
million (ppm) wet weight (ww). Mercury concentrations in 76 percent of the
34 black bass of “legal catch size” (
305 millimeters in length) were 0.3
ppm (ww)(which is the U.S. Environmental Protection Agency water-quality criterion
for the protection of human health). Mercury concentrations exceeded 1.0 ppm
(which is the Food and Drug Administration action level for commercial fish)
in 9 percent of the legal size black bass. In contrast, all 41 trout samples
from stream sites had Hg concentrations < 0.3 ppm (ww), which is likely due
to trophic position. Mercury concentrations in samples of water, sediment,
insects, amphibians, and fish indicate that the inactive Altoona mercury mine,
which drains into the East Fork Trinity River, is a significant contributor
of mercury to Trinity Lake. Ongoing studies are focused on understanding the
fate and transport of mercury from the Altoona mine into Trinity Lake.
