Pesticides in Streams of the United States--Initial Results from the National Water-Quality Assessment Program

By Steven J. Larson, Robert J. Gilliom, and Paul D. Capel

U.S. GEOLOGICAL SURVEY
Water-Resources Investigations Report 98-4222
Sacramento, California, 1999

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Figure 36. Concentrations of chlorpyrifos at two sites. The U.S. Environmental Protection Agency aquatic-life criterion value of 0.041 microgrm per liter is shown as a horizontal line. Concentrations reported as not detected were assigned a value of zero.

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