Publication Summary

This report describes first-year (2003) results in a multi-year monitoring effort to characterize pesticide concentrations in salmon-bearing surface waters. Urban runoff is investigated in Thornton Creek, located in the Cedar-Sammamish watershed. Agricultural land use is evaluated through sampling of the Marion Drain, Spring Creek, and Sulphur Creek Wasteway drainages of the Lower Yakima watershed.

Concentrations of all chemicals were generally low and close to analytical detection limits. 2,4-D was the most commonly detected chemical; however, pentachlorophenol was most commonly detected in the urban watershed. Endosulfan sulfate, azinphos-methyl, chlorpyrifos, diazinon, and 4,4′-DDE results were above the numeric component of selected standards.

The Washington State Department of Agriculture (WSDA) and the Washington State Department of Ecology (Ecology) designed a multi-year monitoring effort to characterize pesticide concentrations in salmonid-bearing surface waters during the typical pesticide use season. The data collected will allow WSDA and the U.S. Environmental Protection Agency (EPA) to refine exposure assessments for pesticides registered for use in Washington State. Understanding the fate and transport of pesticides used in Washington allows regulators to make appropriate decisions to protect endangered species while minimizing the economic impacts to agriculture.

Two index watersheds, representing urban and agricultural land-use patterns, were sampled from April through December 2003. Thornton Creek in the Cedar-Sammamish watershed was chosen as the urban drainage. Marion Drain, Spring Creek, and Sulphur Creek Wasteway in the Lower Yakima watershed represented agricultural land-use patterns. Sampling frequencies included weekly, every other week, and during storm events.

Concentrations of all chemicals were generally low and close to analytical detection limits. 2,4-dichlorophenylacetic acid (2,4-D) was the most commonly detected chemical; however, pentachlorophenol was most commonly detected in the urban watershed. Pesticide detections were compared to Washington State promulgated and EPA recommended aquatic life criteria. Detections were also compared to EPA Environmental Fate and Effects Division acute and chronic toxicological endpoints. One detection of endosulfan sulfate exceeded a Washington State water quality standard. Azinphos-methyl, chlorpyrifos, diazinon, and 4,4′-DDE results were above the numeric component of various standards, but data were insufficient to characterize the time component of these standards. Most chemicals had limited or no criteria available with which to compare concentrations.

Urban run-off frequently contains other chemicals in addition to pesticides and, therefore, semivolatile organic compounds (SVOCs) were analyzed in Thornton Creek. Thirty-eight compounds were detected; the majority of detections occurred during three storm events. Phthalates and polynuclear aromatic hydrocarbons were the most frequently detected compounds in the SVOC analyses.

Link to EIM data for User Study ID RJAC0010