CONCENTRATION, DISTRIBUTION, AND COMPARISON OF SELECTED TRACE-ELEMENTS IN BED SEDIMENT AND FISH TISSUE IN THE SOUTH-PLATTE RIVER BASIN, USA, 1992-1993

During August-November 1992 and August 1993, bed sediment and fish liv er were sampled in the South Platte River Basin and analyzed for 45 el ements in bed sediment and 19 elements in fish liver. The results for aluminum, arsenic, cadmium, chromium, copper, iron, lead, manganese, s elenium, silver, uranium, and zinc are presented here. All 12 trace el ements were detected in bed sediment, but not all were detected in fis h liver or in all species of fish. A background concentration of trace elements in bed sediment was calculated using the cumulative frequenc y curves of trace element concentrations at all sites. Arsenic, cadmiu m, copper, lead, manganese, silver, uranium, and zinc concentrations w ere greater than background concentrations at sites in mining areas or at sites that have natural sources of these elements. Trace element c oncentrations in fish liver generally did not follow the same patterns as concentrations in bed sediment, although concentrations of aluminu m and cadmium were higher in fish liver collected at mountain sites th at had been disturbed by mining. Concentrations of aluminum, arsenic, cadmium, chromium, copper, iron, lead, silver, and zinc increased in b ed sediments in urban areas. Iron, silver, and zinc concentrations in fish liver also increased in urban areas. Concentrations of cadmium, c opper, silver, and zinc in fish liver increased in the agricultural ar eas of the basin. Downstream changes in trace element concentrations m ay be the result of geological changes in addition to changes in land use along the river.