The effect of biochar on the mitigation of the chiral insecticide fipronil and its metabolites burden on loach (Misgurnus.anguillicaudatus).

In this work, the enantioselective toxicity, enrichment, and distribution of fipronil and its main metabolites (fipronil sulfone, fipronil sulfide, and fipronil desulfinyl) in loach (Misgurnus anguillicaudatus) were studied. The influence of maize-straw derived biochar on acute toxicity and bioaccumulation of contaminants were also investigated. The three main metabolites were more toxic to loach than parent fipronil. Meanwhile, loach exhibited more sensitive to S-enantiomer. The alleviated toxic response of loach was observed in the presence of biochar during 72-h acute toxicity test. Fipronil was readily metabolized to sulfone and sulfide with enantioselectivity in loach liver, and it was also found R-fipronil could transform into S-fipronil. The metabolites profile indicated that oxidation processes was the most predominant pathway in loach. Bioaccumulation factors showed the metabolites could be enriched in loach and they were relatively persistent. The bioaccessibility of fipronil and its metabolite decreased significantly when biochar was applied to the ecosystem. The present study provided basic data and outlines of enantioselective toxicity, biotransformation and metabolism of chiral pesticide fipronil and its main derivatives along with biochar in loach-water ecosystem, and further provide an alternative approach for field remediation to mitigate environmental adverse effects of fipronil.