Development and validation of a spectrophotometric method for soil adsorption study of malathion on three Indian soils

Abstract

In view of the widespread use of pesticides in agriculture and its associated toxic effects on environment and human beings, the fate of these chemicals in soil is of major concern. The pesticide adsorption process is one of the major factors affecting its persistence and movement in the soil. With a view of studying the fate of malathion in soil, the adsorption of this insecticide was studied on three Indian soils by using batch equilibrium method. To carry out the adsorption study, a new simple, sensitive, and rapid method was developed, based on microwave-assisted alkaline hydrolysis of insecticide to the dimethyl dithiophosphate and its subsequent reaction with copper(I) perchlorate in acetonitrile. On mixing the reagents, a yellow color developed, which was stable for 120 min and was measured at 419 nm. The adsorption of malathion was studied by using Freundlich's adsorption equation and n f values were observed less than 1 in all the soils. The leaching behavior of the insecticide was studied in terms of ground ubiquity score, which was below 1.8, classifying malathion as non-leacher pesticide, and hence it is not hazardous.