Occurrence and Distribution of Selected Organochlorine Compounds and Trace Elements in Fish Tissue and Streambed Sediment in the Upper Colorado River Basin, 1995-96
By Jeffrey R. Deacon
Fish-tissue and streambed-sediment samples were collected in the Upper Colorado River Basin to determine the occurrence and distribution of organochlorine compounds and trace elements in comparison to land use. Thirty-six sites were sampled during fall 1995 and 1996. Fish and streambed sediment were collected at 14 sites, plus two additional sites for collection of streambed sediment, and analyzed for organochlorine compounds and trace elements. Twenty additional sites were sampled for streambed sediment and analyzed solely for trace elements. More organochlorine compounds were detected in fish tissue than in streambed sediment. DDT and its metabolites were the most commonly detected compounds in fish tissue. Detection frequencies of DDT and its metabolites ranged from 90 to 95%; however, concentrations were low, ranging from 0.006 to 0.980 (g/g). Chlordane, Dacthal, and PCB's also were detected in fish tissue at agricultural, mining, and mixed land-use sites. Concentrations of these compounds were highest at agricultural land-use sites. DDT and its metabolites were detected in streambed sediment at 30 to 35% of the sites, but at low concentrations (ranging from 0.001 to 0.007 (g/g). Concentrations of trace elements in fish tissue and streambed sediment, including As, Cd, Cu, Pb, and Zn, were high in mined areas in the basin. Concentrations of trace elements in fish tissue were mid-range compared to all the data for urban land use, mixed land use, and background sites. Detections of trace elements at agricultural sites were low compared to other land-use sites. Concentrations of As, Cd, Cu, Pb, and Zn in streambed sediment at mining sites exceeded severe effect levels defined in the Canadian sediment-quality guidelines. Concentrations of some trace elements in urban and mixed land uses and at background sites exceeded the lowest effect levels of the sediment-quality guidelines.