Carbon Isotope Fractionation during Chlorothalonil Dissipation in an Upland Soil

Abstract

We investigated changes in the δ¹³C value of a pesticide during its dissipation in an upland soil. Chlorothalonil (2,4,5,6 tetrachloro-1,3-isophthalonitrile) as a test chemical was added to the soil (Light-colored Andosol) and incubated at 30°C in the dark. The pesticide was periodically extracted from the soil and subjected to analysis with an isotope ratio mass spec spectometer. The δ¹³C value of chlorothalonil in the soil increased from −26.5 to −22.5‰ during the incubation period of 70 days. The enrichment factor in this study was −2.6‰. These results suggest the occurrence of carbon isotope fractionation during the dissipation of chlorothalonil in the soil environment.