FACTORS AFFECTING THE ADSORPTION OF 2,4-D AND METHYL PARATHION IN SOILS AND SEDIMENTS

The adsorption of methyl parathion and 2,4-dichlorophenoxyacetic acid (2,4-D) by 19 soil and sediment materials differing widely in their physical and chemical properties was investigated using a batch equilibration technique. Organic matter was the most important single factor affecting adsorption of methyl parathion and 2,4-D. Soil pH and cation exchange capacity were also reasonably well associated with 2,4-D adsorption whereas cation exchange capacity contributed significantly for methyl parathion. Data are presented which indicate that in soil and sediment materials where the organic matter content in less than 1%, oxalate extractable Mn and Ca were associated with the adsorption of these synthetic organics. Additional work should be done in low organic matter soil materials to better quantify the relationship between adsorption and soil geochemical properties.