Occurrence and distribution of semivolatile organic compounds in stream bed sediments, United States, 1992-95

Bed-sediment samples from streams were collected from 443 sites in 19 major river basins during 1992-95 and analyzed for semivolatile organic compounds (SVOCs) to assess the occurrence and distribution of selected Hydrophobic contaminants. Forty SVOCs were detected in more than 5 percent of samples. Of these 40 SVOCs, 27 were polycyclic aromatic hydrocarbons (PAHs), 5 were azaarenes, 5 were phthalates, 2 were phenols, and 1 was a quinone. Statistically higher concentrations of the sum of PAHs, azaarenes, and phthalates were measured in samples from urban drainage basins in comparison to other land uses. The frequency of detection and concentrations of PAHs, azaarenes, and phthalates were highest in the northeastern part and lowest in the western part of the United States. Concentrations of the sum of PAHs and sum of phthalates had statistically significant, but weak, correlations with toxic releases to air, population density, and urban land use. Urban activities could be significant sources and the atmosphere could be a significant transport mechanism affecting the distribution of certain SVOCs.