Washington State Pesticide Monitoring Program, Pesticide Residues in the Kittitas Valley Surficial Aquifer, Pesticides in Ground Water Report No. 10

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Date published: April 1997

Authors: Larson, Arthur G.

Reference:

Larson, Arthur G. 1997. Washington State Pesticide Monitoring Program, Pesticide Residues in the Kittitas Valley Surficial Aquifer, Pesticides in Ground Water Report No. 10. Washington State Department of Ecology. Publication No. 97-318. April.

Abstract:

Twenty-seven wells were sampled near Ellensburg, Washington for pesticides and nitrate+nitrite as N. Water temperature, pH, and specific conductance were also measured in the field. Wells were located in the surficial aquifer that underlies the Kittitas Valley. This water-table aquifer is shallow, with a depth to water ranging from as little as two feet to about 20 feet.

Seven pesticides were detected in the initial samples: atrazine, simazine, prometon, bromacil, bentazon, diphenylamine, and 2,4-D. The presence of bentazon and 2,4-D was not confirmed by the verification sampling. Pesticides were detected in nine of the 27 study wells, with more than one pesticide found in four wells. A breakdown product of atrazine, atrazine desethyl, was found in the six wells where atrazine was detected. Pesticides were not found in the deepest wells, but were restricted to depths less than about 50 feet. Concentrations of all pesticides were below the Maximum Contaminant Level or Lifetime Health Advisory Level set by the EPA for public drinking water. Nitrate was detected in all nine wells with detected pesticides. In one well, the nitrate+nitrite as N concentration in the initial sample ( 11. 9 mg/Lin May) exceeded the 10.0 mg/L drinking water standard for nitrate. However, a verification sample collected in December had a concentration of 3.2 mg/L.

Contact person/agency: Washington State Department of Ecology

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