Accelerated parathion degradation in soil inoculated with acclimated bacteria under field conditions

The feasibility of decontaminating soil at parathion spillage or disposal sites by inoculation with a highly acclimated culture of parathion-degrading bacteria was demonstrated under in situ field conditions. The acclimated culture (AC), capable of utilizing parathion as a sole carbon and energy source, was inoculated into Yolo silt loam soil in which parathion was applied at rates up to 5000 kg/ha. The AC was shown to be capable of completely degrading parathion in soil containing up to 1250 kg/ha of parathion within 35 days. A slower rate of parathion degradation by the AC was observed when the pesticide was applied as the commercial 46.5% emulsifiable concentrate than when applied as the 98% technical grade. The ability of the AC to degrade parathion deteriorated at application rates greater than 1250 kg/ha. The AC may have been adversely affected by the accumulation of the parathion hydrolytic products, p-nitrophenol and ionic diethyl thiophosphate, which were tentatively identified in soil samples.