Toxaphene and Sediment Yields in Runoff from a Mississippi Delta Watershed

Abstract

AbstractToxaphene (chlorinated camphene) and sediment concentrations in runoff from a 15.6‐ha watershed, planted to continuous cotton (Gossypium hirsutum L.), were measured from 1973 through 1975 to determine the toxaphene and sediment yields and to define the major mode of toxaphene transport. The watershed, consisting of Sharkey silty clay soil (Vertic Haplaquepts), had been land‐formed to a mean slope of 0.2%. Measurements indicated a linear relationship between toxaphene yield and sediment yield in runoff. Sediment yields were 28.9, 26.3, and 13.4 metric tons/ha in 1973, 1974, and 1975, respectively, when annual rainfall was 37, 50, and 22 cm above the 30‐year average (125 cm). Although no toxaphene was applied in 1973, the residual toxaphene concentration in the soil from previous applications was 3.5 µg/g. Toxaphene yield in 1973 was 117 g/ha. Toxaphene yields in 1974 and 1975, when 10.1 and 11.2 kg/ha of toxaphene were applied, were 97 and 54 g/ha, respectively, amounting to only 1 and 0.5%, respectively, of the amounts applied. In 1975, 93% of the toxaphene yield was attached to the sediments and only 7% was transported in solution. Toxaphene and sediment yields were greatest during the spring tillage‐planting‐cultivating period, but toxaphene concentrations in runoff and sediment were greatest during the summer application period. Improved erosion control practices are needed in the Delta to reduce the loss of valuable topsoil and to reduce the water pollution potential from sediment and toxaphene.