Distribution of Pesticides in California

A study of pesticide concentrations in waters, sediments and aquatic organisms provided information on chlorinated hydrocarbon pesticides and thiophosphate pesticides. Results indicate that pesticide concentrations are directly related to agricultural practices, chlorinated hydrocarbon pesticides are persistent throughout the aquatic environment, and pesticide compounds are concentrated in sediments and aquatic organisms. Pesticide concentrations are highest in areas affected by agricultural development and decrease in surface waters. The temporal distribution of pesticides in surface waters are related to agricultural drainage practices and to rainfall runoff. Highest pesticide concentrations occur in sediments with smaller grain sizes. Lowest concentrations occur in larger grain size sediments and inorganic materials. Analyses of aquatic organisms support the concept of successive food chain concentration of pesticides. There is an apparent relationship between the age and size of fish, age of organism, and the pesticide concentration.