Biodegradation of carbofuran in enhanced and non-enhanced soils

Abstract

The enhanced degradation of the insecticide carbofuran limits its use as a corn root worm control. The degradation of carbofuran in soils with (enhanced) and without (non-enhanced) a history of carbofuran usage was studied. Experiments showed a rapid breakdown of carbofuran, at starting concentrations of either 10 or 100μg g −. in previously-exposed soils. Degradation in the unexposed soils was minimal. When degradation of ring and carbonyl 14C-labelled carbofuran was compared in enhanced soils, as much as 68% of the applied [ 14C]carbonyl was evolved as 14C-CO 2. In contrast conversion of 14C-ring labeled material to 14C-CO 2 was minimal. Conversion of either labeled site was minimal in non-exposed soils. In enhanced soils the rapid breakdown of carbofuran was correlated to a decrease in the size of the microbial biomass. From our results, enhanced biodégradation apparently is a two-step process. Hydrolysis of the carbonyl side-chain is followed by adsorption of the primary metabolite to soil. Biomass returned to near control size following removal of the pesticide from the system. However, the rapid breakdown could be slowed by introduction of an adsorptive surface, charcoal.