Degradation of pesticides in soil as influenced by the presence of hydrolysis metabolites

Abstract

The degradation of 8 pesticides was evaluated in a soil pretreated with their respective hydrolysis metabolites. 2,4-Dichlorophenol, p-nitrophenol, and salicylic acid conditioned the soil for enhanced degradation of 2,4-dichlorophenoxyacetic acid (2,4-D), parathion, and isofenphos, respectively. Repeated application of carbofuran phenol, 2-isopropyl-4-methyl-6-hydroxypyrimidine, methyl phenyl sulfone, thiophenol, isopropyl salicylate, and 2,4,5-trichlorophenol had no effect on the rate of degradation of their parent pesticides. Prior exposure of soil to 3,5,6-trichloro-2-pyridinol resulted in increased persistence of its parent compound, chlorpyrifos. Results indicate that pesticide hydrolysis metabolites can effect the induction or inhibition of enhanced microbial degradation of some soil-applied pesticides. 457

Interactions Between Pesticides and Their Major Degradation Products

“…Particularly when applied to the soil repeatedly, 3,5,6-trichloro-2-pyridinol (TCP), a hydrolys is metabolite of chlorpyrifos and trichlopyr, slowed the degradation of chlorpyrifos (8). At 100 ppm, TCP inhibited the degradation of carbofuran and D0WC0 429X in problem soils but did not have any effect at 1 and 10 ppm (19).…”

“…Carbofuran phenol, a hydrolysis product of carbofuran, conditioned soils for enhanced degradation of carbofuran under anaerobic environment (7) but did not have any effect in aerobic conditions (8,18). Although the presence of carbofuran phenol in anaerobic soils accelerated carbofuran hydrolysis, the phenol was not used as an energy source and accumulated in the soil.…”

“…The enhanced biodégradation of some pesticides has been attributed to the substrate value of their degradation products (6)(7)(8). Degradation products of pesticides belonging to different classes such as phenoxyacetic acids, carbamothioates, N-methyl carbamates, and organophosphates have been reported to condition soils for rapid degradation of their respective parent compounds (Table II).…”

“…In that study, pretreatment of soils with closely related compounds such as phenoxyacetic acid and 2-chlorophenol, however, had no effect on the persistence of 2,4-D. Steenson and Walker (15) reported the ability of an Achromobacter strain to use 2,4-dichlorophenol as a substrate. In a recent study in our laboratory, the mineralization rate of 2,4-D increased with the number of pretreatments with 2,4-dichlorophenol (8).…”

“…Laboratory studies have investigated the fate of degradation products as influenced by their prior treatment (8,12). The purpose of these studies was to confirm the substrate value of the degradation products.…”