Enantioselective behaviors of cis-epoxiconazole in vegetables-soil-earthworms system by liquid chromatography-quadrupole-time-of-flight mass spectrometry.

Cis-epoxiconazole is a widely used triazole fungicide for control and prevention of a series of fungal diseases in fruits, vegetables, teas and grains. The present work aimed at exploring enantioselective behavior of cis-epoxiconazole in the vegetable-soil-earthworm system. Firstly, the absolute configuration of cis-epoxiconazole enantiomers was ascertained. Secondly, enantioselective degradation of cis-epoxiconazole in cabbage, pakchoi and pepper were performed under field trials, which has not been previously reported. Enantioselective degradation occurred in cabbage and pepper samples. 2R, 3S-(+)-cis-epoxiconazole was degraded faster than 2S, 3R-(-)-cis-epoxiconazole in cabbage, while the reversed results were obtained in pepper. No enantioselective degradation was observed in pakchoi. Finally, soil is the principal reservoir of environmental pesticides, so the enantioselective behaviors of cis-epoxiconazole in soil and soil organism (earthworm, Eisenia fetida) were evaluated. Similar bioaccumulation curves in earthworms and degradation curves in soil were observed under the exposure levels of 1 and 10 mg/kg. Accumulation factors (AFs) indicated earthworms had weak bioaccumulation potential to cis-epoxiconazole in the contaminated soil, and no obvious enantioselectivity was observed. The different enantioselectivities in different vegetables illuminated that preferentially enriched enantiomer might impose higher risk on human health than the other one, and the high risk enantiomer required further assessment. These results may reduce the uncertainty of cis-epoxiconazole to the environmental risk assessment.