ABSTRACT
Besides the organochlorine insecticides, a few compounds in other pesticide classes were detected in some studies. Most of these pesticides contained chlorine or fluorine substituents and were intermediate in hydrophobicity. The monitoring studies reviewed suggest that pesticides were detected more often in aquatic biota than in bed sediment. Agricultural use of insecticides declined during the 1980s. Also, there was a pronounced change in the types of insecticides used from the 1960s to the 1980s as organochlorine insecticides were replaced by organophosphate, carbamate, and other insecticides. Relatively few national studies monitored currently used pesticides in bed sediment or aquatic biota. Sources of pesticides to bed sediment and aquatic biota include agricultural and nonagricultural applications and atmospheric contamination. In urban areas, organochlorine insecticides have been largely replaced over time by insecticides in other classes. Seasonal events that strongly affect the movement of pesticides to and within surface waters also may influence the accumulation of pesticide residues in bed sediment and aquatic biota.
