Selected trace-element and synthetic-organic compound data for streambed sediment from the Clark Fork-Pend Oreille and Spokane River Basins, Montana, Idaho, and Washington, 1998

Streambed-sediment samples were collected at 22 sites during the summer of 1998 as part of the U.S. Geological Survey National Water-Quality Assessment Program. Sampling sites in the Clark Fork-Pend Oreille and Spokane River basins represented a wide range of environmental conditions including pristine mountain streams and large rivers affected by mining related and urban activities. Samples were analyzed for 45 inorganic major and trace elements, 109 synthetic organic compounds, and carbon. This report presents the selected results of streambed-sediment sampling from the Clark Fork-Pend Oreille and Spokane River basins in Montana, Idaho, and Washington. Trace-element concentrations in streambed sediment determined from this study were compared to median trace-element concentrations for streambedsediment data collected from streams across the Nation during 1992-96. Generally, concentrations of arsenic, cadmium, copper, lead, mercury, and zinc were higher or similar to the national median concentration of these same trace elements. Concentrations of chromium, nickel, and selenium in streambed sediment of the study area generally were lower than the national median concentration. Most of the analytical results for synthetic organic compounds were reported as either estimated or non-detected values. Phthalates and polycyclic aromatic hydrocarbons were the most frequently detected classes of synthetic organic compounds in streambed sediment. Organochlorine pesticide residues were detected at two sites. Polychlorinated biphenyls were detected at one site