WATER POLLUTION BY INSECTICIDES IN AN AGRICULTURAL RIVER .BASIN. I. OCCURRENCE OF INSECTICIDES IN RIVER AND TREATED MUNICIPAL WATER

Insecticide contamination was studied in a stream from the summer of 1959 through the winter of 1962–63. The stream drains a 400-square-mile (1,036-km2) watershed in northern Alabama, in which approximately 15,000 acres (6,070 ha) of cotton are cultivated annually. Estimates of insecticide usage on cotton varied from 58,000 lb technical (26.3 metric tons) in 1960 to 139,000 lb (63.0 metric tons) in 1962. Toxaphene, DDT, and BHC (benzene hexachloride) comprised over 90% of the insecticides used. Water was sampled by the carbon adsorption method at a municipal water treatment plant. The data are reported as concentrations of insecticide recovered. DDT was never detected, but toxaphene and BHC were detected in all samples. Toxaphene ranged from 7 to 410 parts per trillion (ppt), and BHC from 7 ppt to 1.0 part per billion (ppb). Samples of treated and untreated water showed that the purification process failed to remove toxaphene and BIIC. Samples taken in the summer of 1960 from the stream system indicated the same order of contamination observed at the water treatment plant. The data suggest that soil-persistent insecticides in the stream are related to levels of usage and to the solubility of the compounds.