Stable carbon isotope fractionation during the biodegradation of lambda-cyhalothrin

Abstract

In this study, the microbial degradation of lambda-cyhalothrin in soil was investigated using compound-specific stable isotope analysis. The results revealed that lambda-cyhalothrin was biodegraded in soil under laboratory conditions. The half-lives of lambda-cyhalothrin were determined to be 49 and 161days in non-sterile and sterile soils spiked with 2mg/kg lambda-cyhalothrin and 84 and 154days in non-sterile and sterile soils spiked with 10mg/kg lambda-cyhalothrin, respectively. The biodegradation of lambda-cyhalothrin resulted in carbon isotope fractionation, which shifted from −29.0‰ to −26.5‰ in soil spiked with 2mg/kg lambda-cyhalothrin, and to −27.5‰ with 10mg/kg lambda-cyhalothrin. A relationship was established between the stable carbon isotope fraction and the residual concentrations of lambda-cyhalothrin by the Rayleigh equation in which the carbon isotope enrichment factor ε of the microbial degradation of lambda-cyhalothrin in the soil was calculated as −2.53‰. This study provides an approach to quantitatively evaluate the biodegradation of lambda-cyhalothrin in soil in field studies.