The Persistence of Pesticides in Impounded Waters

The purpose of this study was to investigate the persistance of the insecticides aldrin, dieldrin, chlordane, and DDT in water. A small drainage area was sprayed with these compounds, and the insecticides were collected in the runoff water from the area. Laboratory experiments were performed to determine the effectiveness of aeration, adsorption on silt, and adsorption on algae in removing the pesticides from water. All of the pesticides were found in samples of water collected from the area for the full period of the tests. The amounts which were found in a small pond into which the surface water drained was consistently less than that found in the surface runoff water itself. The reduced concentrations in the pond water were apparently the result of a combination of sedimentation, adsorption on algae or silt, or volatilization of the insecticide from the water into the atmosphere. In general, the efficiency of removal of insecticide from water by any one of these processes appears to be low. However, because of the large ratio of absorbant to insecticide, the overall removal is substantial