ADSORPTION AND MOBILITY OF ACEPHATE IN SOILS

The influence of soil properties on the adsorption and mobility of ace phate (O,S-dimethyl-acetylphosphoroamidothioate) was studied. The Freu ndlich adsorption constant (K) and the distribution coefficient (K-d) were found to be highly correlated (P < 0.001) with the silt + clay co ntent of the soil, both for the studied soils as a whole and for those with organic matter contents below 2%. The mobility of acephate as de termined by thin-layer chromatography (saturated flow conditions) was found to be R(f) = 1 for all soils except the three with a high silt clay content, whose R(f) was smaller than unity. A study of the aceph ate mobility in soil-packed columns under unsaturated flow conditions revealed that the highest proportion of the insecticide was retained a t the top of the columns; also, the insecticide distribution in the co lumns and the overall amounts retained and leached were related to the silt + day content of the soils. (C) 1994 Academic Press, Inc.