Degradation of O, O-dimethyl S-[alpha-(carboethoxy)-benzyl] phosphorodithioate (phenthoate) in soil.

The degradation of ring-labeled 14C-phenthoate in a moist sandy loam and silty clay loam soil was studied. Phenthoate degradation was attributed to the action of extracellular heat-labile soil enzymes which converted to its carbon ester hydrolysis product, phenthoate acid. Thus, rate of phenthoate degradation was greatly retarded in autoclaved soil, but was equally rapid in nonsterile soil under both aerobic and anaerobic conditions. Degradation was also rapid even at a soil treatment of 100 ppm. Phenthoate acid was extensively degraded to 14CO2 by soil organisms under aerobic conditions, but due to unfavorable factors, degraded only by slow first-order kinetics under anaerobic conditions and at the 100 ppm fortification level under aerobic conditions. Phenthoate and phenthoate acid were confirmed as the principal soil components by isolation and identification by IR and NMR data.