MODELING ENVIRONMENTAL-EFFECTS ON ENHANCED CARBOFURAN DEGRADATION

Prediction of the fate of pesticides in soil is of interest from an en vironmental (pollution) as well as an agricultural (efficacy, carryove r) viewpoint. Two environmental parameters that control microbial degr adation of pesticides in soil are moisture and temperature. This study was designed to quantify the impact of soil water content and tempera ture on microbial degradation rates of the insecticide carbofuran (2,3 -dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate). Carbofuran degr adation was determined by monitoring the [C-14] carbondioxide producti on from soils amended with [carbonyl-C-14]carbofuran. Soils were incub ated at seven soil-water tensions over the range of 0.03 to 1.5 MPa, a nd at five temperatures (10-degrees-C to 30-degrees-C). The sigmoidal degradation kinetics observed from these incubations were modeled usin g a general saturation model. For the moisture experiments, maximum ra te of hydrolysis and half-life (DT50) were accurately modeled by an ex ponential relationship. The response of carbofuran degradation to temp erature was also well described by an exponential relationship, from w hich it was estimated that the Q10 associated with the maximum rate wa s 1.68, and the Q10 for DT50 was 1.89.