Fate Characterization of Benzene Kresoxim-Methyl (a Strobilurin Fungicide) in Different Aerobic Soils.

Benzene kresoxim-methyl (BKM) is a promising broad-spectrum strobilurin fungicide widely used to control fungal pathogens in crops. However, information on its environmental fate is limited. To broaden our understanding of this fungicide's kinetic fate in aerobic soils, we labeled BKM with C on its benzoate ring and used ultralow-level liquid scintillation counting coupled with high-performance liquid chromatography analysis. Results show that degradation, mineralization, and bound residue (BR) formation of BKM was controlled by soil type and microbial community composition. Degradation of BKM followed first-order dynamics, and the half-lives () were 51.7, 30.8, and 26.8 d for clay, loamy, and saline soils, respectively. After 100 d, about 0.13, 4.35, and 5.94% of the initial C-BKM was mineralized, and 14.43, 19.90, and 28.81% was formed as BRs in the clay, loamy, and saline soils, respectively. About 60 to 85% of the C-BKM residue in soil was extractable; of this fraction, 30 to 50% was composed of incomplete degradation intermediates. Up to 40% of extractable C-BKM in soil was readily available. Our results suggest that BKM and its incomplete intermediates had a relatively long persistence in soil, which may lead to exposure for nontarget organisms. Soil microbes may play a dominant role in controlling the fate of BKM in soil as sterilization sharply decreased its mineralization rate from 4.35 to 0.03%, increased from 30.8 to 85.6 d, and decreased the BR fraction from 19.90 to 3.25%.