RESUMO
Samples of water, streambed material, fish, and soil were collected in four small drainage basins in Pennsylvania in 1969-71 and analyzed to determine the concentrations of chlorinated hydrocarbon insecticides. Water samples were also analyzed for phenoxy-acid herbicides. Each basin studied represents a predominant land use: forest, general farms, residential areas, and orchards. All water and fish samples showed pesticide concentrations less than the maximum level recommended by the Public Health Service, U.S. Department of Health, Education, and Welfare. However, no fish were found in the orchard stream. DDT or one of its metabolites was the most frequently occurring insecticide and was detected in all media sampled except the forest soil. The highest combined concentration of DDT and its metabolites in storm-runoff samples was 11.4 mug/liter in a sample collected from the residential area stream, but the median was higher (0.12 mug/liter) in the orchard than in the residential area (0.02 mug/liter). A sample of the top 0.5 inch (13 mm) of orchard soil contained 40,000 mug/kg DDT and its metabolites, even though DDT had not been used in the orchards for several years prior to this study. Maximum concentrations detected in other orchard media are 330 mug/kg in streambed material and 3.45 mug/kg in storm runoff. Dieldrin was the second most frequently occurring insecticide. Other insecticides detected were chlordane, heptachlor epoxide, lindane, and a trace of aldrin in one fish sample. Each stream contained at least one of the following herbicides: 2,4-D, silvex, or 2,4,5-T.