Degradation of the insecticide malathion in soils from Brazilian northeast region

Abstract

The chemical transformation of the insecticide malathion in four soil types from the States of Alagoas and Paraíba was analyzed by using radiometric techniques. The rate of degradation in the four soils was related to the adsorption of the insecticide by soil components, suggesting that in three profiles of Red-Yellow Podzolic soil the degradation took place by a chemical process catalyzed by adsorption. In the profile of Light-Humic dystrophic Gley soil the adsorption retarded the transformation of malathion into other chemical species; this might be related to the type of clay mineral present in the soil structure. The ¹⁴CO₂ evolution was very slow as compared with the transformation of the malathion molecule, indicating that the intermediate metabolites are chemically more stable than malathion from which they originated.