Modeling Environmental Effects on Enhanced Carbofuran Degradation

Prediction of the fate of pesticides in soil is of interest from an environmental (pollution) as well as an agricultural (efficacy, carryover) viewpoint. Two environmental parameters that control microbial degradation of pesticides in soil are moisture and temperature. This study was designed to quantify the impact of soil water content and temperature on microbial degradation rates of the insecticide carbofuran (2,3-dihydro-2,2-dimethylbenzofuran-7-yl methylcarbamate). Carbofuran degradation was determined by monitoring the ["C] carbondioxide production from soils amended with [c~rbonyl-'~Cjcarbofuran. Soils were incubated at seven soil-water tensions over the range of 0.03 to 1.5 MPa, and at five temperatures (lOOC to 30°C). The sigmoidal degradation kinetics observed from these incubations were modeled using a general saturation model. For the moisture experiments, maximum rate of hydrolysis and half-life (DT,,) were accurately modeled by an exponential relationship. The response of carbofuran degradation to temperature was also well described by an exponential relationship, from which it was estimated that the Qlo associated with the maximum rate was 1.68, and the Qlo for DTso was 1.89.