Publication Summary

During June and July of 1998, the Washington State Department of Ecology collected water samples at three sites in surface drainage ditches from cranberry growing areas near Grayland, Washington. Two locations were test sites, and the third was a control site. Water samples were analyzed for organophosphorus pesticides and general water quality parameters. Laboratory and in situ bioassays using Daphnia pulex tested the toxicity of the drainage water. These data were collected to evaluate ongoing efforts to reduce pesticide contamination discovered in cranberry bog drainage in 1994.

During June and July of 1998, the Washington State Department of Ecology collected water samples at three sites in surface drainage ditches from cranberry growing areas near Grayland, Washington. Two locations were test sites, and the third was a control site. Water samples were analyzed for organophosphorus pesticides and general water quality parameters. Laboratory and in situ bioassays using Daphnia pulex tested the toxicity of the drainage water. These data were collected to evaluate ongoing efforts to reduce pesticide contamination discovered in cranberry bog drainage in 1994.

Three organophosphorus pesticides were detected in the water samples: chlorpyrifos, diazinon, and azinphos-methyl. All pesticide concentrations were lowest prior to pesticide application. The highest levels were measured after application.

All three pesticides detected exceeded recommended water quality criteria for most of the study period.

1. Chlorpyrifos exceeded the state water quality criterion of 0.041 ug/L in 25% of the samples before pesticide application and 83% after application.

2. Diazinon exceeded available water quality guidelines of 0.04 ug/L in 50% of the samples before application and 100% after application. Diazinon concentrations were the highest of the three detected pesticides.

3. Azinphos-methyl exceeded the EPA water quality criterion of 0.01 ug/L throughout the study period.

When compared to data collected between 1994 and1996, the 1998 data reveal no reduction in overall pesticide levels, despite implementation of best management practices by a few of the cranberry growers.

Bioassay results show the potential exists for adverse biological effects in the drainage ditches after pesticide application occurs.