Influence of Clay Minerals on the Persistence of Carbamate Pesticides

Influence of clay minerals, temperature, pesticide concentration, acidic, neutral alkaline pH, FYM (Farm yield manure), exchangeable cations, nitrogen, phosphate and fluoride on the persistence of six carbamate pesticides (Oxamyl I; Carbaryl II, Phorate III; Phosphomidon IV; Carbofuran V and methomyl VI), on three different clay minerals (Montmorillonite, illite and kaolinite) was investigated. The process of degradation followed the psudo first order kinetics. The degradation rate was found to increase with rise in temperature, amount of FYM or N and decrease with increasing pesticidal concentration, fluoride or phosphate. The degradation was rapid in alkaline medium than neutral or acidic. The degradation was rapid in untreated clay minerals and the nature of exchangeable cation has no appreciable effect on pesticide degradation. Degradation followed the order untreated >Na- >Al- > Fe-. The values of activation energies (Ea) indicated that hydrolysis is the probable mechanism of degradation. The rate of degradation decreased in the order pesticide I >VI >V>IV>II>III. The degradation of pesticides in the clay minerals followed the order kaolinite > illite > montmorillonite. The increase in rate of degradation in presence of clay minerals probably may be due to formation of a complex between pesticide-clay surface-metal.