U.S. Geological Survey

Preliminary Evaluation of Streambed Sediment and Aquatic Biota as Media for Characterizing the Occurrence of Trace Elements and Organochlorine Compounds in the Willamette Basin, Oregon

During 1992-93, 27 organochlorine compounds (pesticides plus total PCBs) and 21 trace elements were analyzed in bed sediment and aquatic biota from 20 stream sites in the Willamette Basin as part of the National Water-Quality Assessment (NAWQA) Program. All samples were collected, processed, and analyzed using standardized, nationally consistent NAWQA protocols. Most trace-element concentrations were considerably higher in bed sediment than in tissue, although Cd, Hg, Se, and Ag were notable exceptions. Conversely, although frequencies of detections for organochlorine compounds in tissue were only slightly greater than in bed sediment, actual concentrations in tissue (normalized to lipid) were as much as 19 times those in bed sediment (normalized to organic carbon). Sculpin (Cottus spp.) and Asiatic clams (Corbicula fluminea), which were found at 14 and 7 sites, respectively, were the most widespread taxa collected during the study. Concentrations of trace elements typically were greater in Asiatic clams than in sculpin. In contrast, almost half of the organochlorine compounds analyzed were found in sculpin, but only DDT and its degradation products were detected in Asiatic clams; this may be related to the lipid content of sculpin, which was almost three times higher than for Asiatic clams.