Comprehensive study of flusulfinam in paddy water-sediment microcosms: Enantioselective fate, degradation pathways, and toxicity assessment.

Flusulfinam, a novel chiral herbicide, demonstrates effective weed control in paddy fields. Nevertheless, a comprehensive investigation into its environmental fate in paddy systems, particularly at the enantiomeric level, remains deficient. Herein, paddy water-sediment microcosms were constructed across four sites to explore the enantiomeric behavior of flusulfinam. Enantioselective environmental behavior results show S-flusulfinam was found to preferentially accumulate in sediment, while R-flusulfinam showed preferential degradation in water and the overall system. Following this, the metabolic pathway of flusulfinam in the microcosms was also proposed. Eight metabolites were identified for the first time, and the synthesis and quantification of main metabolites M299 and M100 further substantiated the proposed flusulfinam metabolic pathways. In addition, enantioselective of R-M299 was also found in the Anhui microcosms. As predicted by Toxicity Estimation Software Tool, acute toxicity assessments revealed that M299 and M100 exhibit lower toxicity toward Danio rerio larvae and Selenastrum capricornutumwere compared to flusulfinam. Then, Illumina sequencing revealed that the degradation of flusulfanam had a significant impact on the abundance of key microbial genera, including Anaeromyxobacter, Nitrospira, Reyranella, and Sphingomonas. Overall, this study offers novel insights into the enantioselective fate of flusulfinam in paddy water-sediment ecosystems, provides a valuable reference for the assessment of environmental and ecological risks associated with flusulfinam. Finally, the R-flusulfinam is considered the safer enantiomer, as evidenced by its preferential degradation in microcosms systems and our prior research highlighting the high efficacy and low toxicity characteristic of R-flusulfinam.