Adsorption of fenitrothion and thiobencarb on bulk soil and its components

Adsorption isotherm of fenitrothion and thiobencarb were significantly greater on humic acid (HA) fraction followed by clay fraction compared to that on bulk soils of clay soil and sandy clay loam soil. The different adsorbents (HA fraction, clay fraction and bulk soil) of clay soil were more adsorbed fenitrothion and thiobencarb than the adsorbents of sandy clay loam soil. Adsorption capacity of soil mineral fractions can be arranged for fenitrothion and thiobencarb in the order; clay > silt > sand fraction, it is attributed to their difference in surface area. Using the soil fraction contribution in adsorption, data of the soil analysis and Karickhoff model, it was discovered that, at all different initial concentrations of fenitrothion and thiobencarb, the total prospective contribution of the various constituents together was substantially higher than what was actually adsorbed on bulk soil. Mean of actual amounts for fenitrothion adsorbed on the bulk soil was 33.65% for clay soil and 24.28% for sandy clay loam soil. Also, mean of actual amounts for thiobencarb adsorbed on the clay soil was 30.87% and on sandy soil was 16.62%. It's possible that certain active sites on clay and HA fractions were inactive during adsorption because they were occluded by other substances. Because the clay fraction (fclay) is larger than the organic matter (OM) fraction (fOM), it plays a significant role in the tested pesticide adsorption process. These results highlight the important function that clay minerals play in pesticide sorption because of their higher ratio to OM content.