STUDIES ON ADSORPTION BEHAVIOUR OF THIOPHANATE METHYL ON SOILS

摘要

The problem of pesticide residue in soils and plants is becoming more and more acute because of their application in large quantities and subsequent slow breakdown. The paper deals with a study on the adsorption behaviour of thiophanate-methyl on somesoils of UP. The adsorption ranges of thiophanate-methyl were 2.6 to 15.5, 2.08 to 13.17 and 1.56 to 12.36 (umol/g for silty clay loam, sandy clay loam and sandy loam soils, respectively. All the adsorption isotherms were "S' shaped. The study indicatesthat the adsorption gradient with concentration depends both on the quantity of thiophanate-methyl already adsorbed on the soil and its concentration. The rapid adsorption following initial low rate of adsorption might be attributed to the displacementof solvent molecules from the soil surface by the molecules of thiophanate-methyl. This implies possibility of multilayer adsorption until saturation is reached.