The occurrence of selected contaminants in fish tissue in relation to land use within the South Platte River basin was investigated as part of the U.S. Geological Survey's National Water Quality Assessment Program. Land-use categories were forest (subcategories minimally impacted and mining), urban, agriculture, and rangeland. Fish (brown trout, white sucker, common carp) were collected at 17 sites during fall 1992. Whole fish were composited for organochlorine analyses and fish livers were composited for trace-element analyses. Results from organochlorine analyses indicated the presence of chlordane (range = 0. 006-0.041 µg/g), dichlorodiphenylchlorethane (DDT, 0.01-2.16 µg/g), dieldrin (0.013-0.79 µg/g), dacthal (DCPA, 0.007-0.063 µg/g), and polychlorinated biphenyls (PCBs, 0.096-0.580 µg/g). Organochlorine compounds were associated with specific land use. Chlordane was detected at urban sites and PCBs were detected at urban and agricultural sites. Concentrations of DDT, DCPA, and dieldrin were highest at agricultural sites. Concentrations of cadmium (Cd), manganese and zinc (Zn) in trout were higher at the mining site (23, 6, 127 µg/g, respectively) than at minimally impacted sites (<2, <4.5, <80 µg/g, respectively) in forested areas. Concentrations of Cd and Zn varied among fish species (carp: mean = 10.8 µg/g for Cd, 590 µg/g for Zn; sucker: 1.1 µg/g for Cd, 113 µg/g for Zn; trout: 0.9 µg/g for Cd; 76 µg/g for Zn), making comparisons among land uses difficult. Copper concentrations were higher at forested sites (mean = 0.33 µg/g) than at all other sites (<0.11 µg/g).
1 U.S. Geological Survey, Box 25046, MS 415, Denver Federal Center, Lakewood, CO 80225