Biodegradation of fenitrothion in soil

The biodegradation of fenitrothion (an organophosphorus pesticide) in garden soil of western Uttar Pradesh in northern India has been studied. Both natural and autoclaved soil were treated with 10 p.p.m. of fenitrothion at field capacity moisture and incubated for 90 days in glass containers at 25 and 40 degrees C. The soil samples were collected at various intervals between 0 and 90 days and analysed by HPLC for the residual pesticide and metabolites formed. At 0 days the recovery of the pesticide was 98% and the pesticide then degraded linearly with incubation time. The concentration of pesticide in the natural soil decreased with incubation time with concomitant formation of two metabolites at 25 degrees C and three metabolites at 40 degrees C. These metabolites were purified to homogeneity by HPLC and characterized by IR spectroscopy. The results showed oxidative desulphuration of the pesticide at the first step followed by hydrolytic cleavage of P-O-aryl linkage and demethylation at the second and third step, respectively.