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<br />Concentrations of selenium in four sets of water samples collected in <br />Sweitzer Lake ranged from 10 to 25 micrograms per liter. The selenium <br />concentrations in all water samples collected at Sweitzer Lake exceeded <br />criteria for protection of aquatic life. Mercury was detected in water <br />samples collected from the lake and from inflow into the lake in July 1988. <br /> <br />Concentrations of selenium in bottom-sediment samples collected from the <br />Gunnison and Uncompahgre Rivers were slightly greater than baseline concen- <br />trations for soils in the Western United States. There was substantially more <br />selenium in bottom sediments from Sweitzer Lake; the selenium concentration <br />was 41 micrograms per gram in a sample collected in January 1988. <br /> <br />Selenium concentrations in fish and avian food items at Sweitzer Lake may <br />be large enough for fish and wildlife to accumulate harmful amounts of sele- <br />nium through biomagnification of selenium in the food chain. Selenium concen- <br />trations in all whole-body fish samples from Sweitzer Lake exceeded the <br />85th-percentile concentration of the National Contaminants Biomonitoring <br />Program. The maximum selenium concentration was 50 micrograms per gram dry <br />weight in a carp sample from Sweitzer Lake. The maximum recommended daily <br />intake of selenium for humans could be exceeded by eating catfish from <br />Sweitzer Lake; three ounces of catfish fillet had about 502 micrograms of <br />selenium. <br /> <br />Concentrations of selenium in many whole-body samples from the Gunnison <br />and Uncompahgre Rivers and three tributaries of the Uncompahgre River exceeded <br />the 85th-percentile concentration of the National Contaminants Biomonitoring <br />Program. The maximum selenium concentration in a fish sample collected from <br />streams was 10.5 micrograms per gram dry weight in a carp collected from Dry <br />Creek, a tributary of the Uncompahgre River. <br /> <br />Selenium concentrations in bird livers, whole-body birds, and eggs <br />collected at Sweitzer Lake and the Escalante State Wildlife Area were equal, <br />and some of the selenium concentrations indicate significant exposure to <br />selenium. The maximum selenium concentration in a bird sample was about <br />84 micrograms per gram dry weight in the liver of a western grebe collected <br />at Sweitzer Lake. - <br /> <br />Most other trace-element concentrations were less than baseline con- <br />centrations or less than concentrations that might be harmful to fish and <br />wildlife. There were concentrations of cadmium, copper, mercury, and zinc in <br />some biota samples that exceeded background concentrations. Large concen- <br />trations of mercury were reported in two common merganser livers collected at <br />the Escalante Stale Wildlife Area. <br /> <br />DDE was detected in all biota samples that were analyzed for organic <br />compounds. The maximum DDE concentration was 110 micrograms per gram wet <br />weight in a whole-body killdeer that probably accumulated the DDE in its <br />wintering areas outside of Colorado. Toxaphene was detected in 12 biota <br />samples. Concentrations of the herbicide .dacthal in three fish samples <br />exceeded the maximum dacthal concentration reported by the National Pesticide <br />Monitoring Program. <br /> <br />2 <br />