Enantiomer-Specific Study of Fenpropathrin in Soil-Earthworm Microcosms: Enantioselective Bioactivity, Bioaccumulation, and Toxicity

Abstract

In this study, the enantiomer-specific bioactivity, bioaccumulation, and toxicity of fenpropathrin (FEN) enantiomers were investigated in soil-earthworm microcosms. The bioactivity order was <i>S</i>-FEN > <i>rac</i>-FEN > <i>R</i>-FEN for <i>Spodoptera litura</i> and <i>Conogethes punctiferalis</i>. Moreover, <i>S</i>-FEN was 12.0 and 32.2 times more toxic than <i>rac</i>-FEN and <i>R</i>-FEN to earthworms, respectively. <i>S</i>-FEN degraded faster than <i>R</i>-FEN with the enrichment of <i>R</i>-FEN in the soil environment. Furthermore, the peak-shaped accumulation curves for FEN enantiomers were observed, and <i>R</i>-FEN was preferentially bioaccumulated by earthworms. As compared to <i>R</i>-FEN, <i>S</i>-FEN induced greater changes in the activities of detoxification enzymes, antioxidant enzymes, and malondialdehyde content, which suggested that earthworms exhibited enantioselective defense responses to <i>S</i>-FEN and <i>R</i>-FEN. Integrated biomarker response results indicated that <i>S</i>-FEN exhibited higher toxic effects on earthworms than <i>R</i>-FEN. Finally, molecular simulation revealed that the greater interaction forces between <i>S</i>-FEN and sodium channel protein could be the primary reason for the enantioselective bioactivity and toxicity of FEN enantiomers. This study comprehensively highlights the enantiomer-specific bioactivity, bioaccumulation, toxicity, and mechanism of FEN in soil-earthworm microcosms at the enantiomer level. Our findings will contribute to a better risk assessment of FEN in the soil ecosystem.