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<br />bottom-sediment samples also were done by the National Water Quality <br />Laboratory using methods described by Wershaw and others (1987). Improvements <br />were made in analysis of carbamates in water at the laboratory, and the <br />reporting level for the samples collected for this study was 0.5 ~g/L <br />instead of 2.0 ~g/L as stated in Wershaw and others (1987). In addition, a <br />method was initiated at the laboratory in 1988 that can be used to determine <br />carbamate concentrations much smaller than 0.5 ~g/L in samples where positive <br />identification of target compounds was made (S.M. Johnson, u.s. Geological <br />Survey, written commun., 1988). <br /> <br />Inorganic analyses of bottom-sediment samples were done by the u.s. <br />Geological Survey's Branch of Exploration Geochemistry Laboratory in Lakewood, <br />Colorado. The samples were dry sieved at the laboratory through a 2-mm screen. <br />The samples then were split, and one split was sieved through a 0.0625-mm <br />screen. Both size fractions, less than 2 mm and less than 0.0625 mm, were <br />analyzed for trace elements. Analytical methods for bottom-sediment analyses <br />are described by Severson and others (1987). <br /> <br />Biological samples were analyzed by Hazelton Laboratories America, Inc., <br />in Madison, Wisconsin, and the Environmental Trace Substances Research <br />Center in Columbia, Missouri!. Those laboratories were contracted by the <br />u.s. Fish and Wildlife Services's Patuxent Analytical Control Facility in <br />Patuxent, Maryland. Biological samples were analyzed for the constituents <br />listed in table 8. Most trace elements were analyzed by inductively coupled <br />argon-plasma/atomic-absorption spectrometry after complete digestion of the <br />sample with strong acids. Arsenic and selenium were analyzed by hydride- <br />generation atomic absorption, and mercury was analyzed using flameless cold- <br />vapor atomic absorption. Biological samples scanned for pesticide residues <br />were analyzed using solvent extraction followed by electron-capture gas <br />chromatography. <br /> <br />DISCUSSION OF RESULTS <br /> <br />Water-Quality Results <br /> <br />Analytical results for stream samples were examined to identify effects <br />of the Uncompahgre Project on water quality of the Gunnison and Uncompahgre <br />Rivers and to determine if potentially harmful concentrations of trace <br />elements or pesticides were present at the downstream sites. Analytical <br />results for the sites at Sweitzer Lake were examined to determine if selenium, <br />other trace elements, or pesticides were present in potentially harmful <br />concentrations. Water-quality properties and analytical results of inorganic <br />constituents are reported in table 16, and results for pesticides are in <br />table 17 in the "Supplemental Data" section at the back of the report. <br /> <br />Constituent concentrations were compared to water-quality standards <br />established by the Water Quality Control Commission of the State of Colorado <br />(Colorado Department of Health, 1988). The State has classified streams and <br /> <br />!The use of trade names in this report does not constitute endorsement by <br />the U.S. Geological Surveyor the U.S. Fish and Wildlife Service. <br /> <br />36 <br />