Fate characteristics of the chiral pesticide dufulin in flooded anaerobic soils and its interaction with soil microorganisms.

Dufulin (DFL), a plant antiviral agent synthesized in China, has been widely used to control viral diseases in rice, tobacco, tomato, and other crops. However, its fate in flooded anaerobic soils, which is essential for environmental risk assessment, remains unknown. Using the C tracer technique, the fate of C-labeled DFL isomers in flooded anaerobic soils was systematically investigated in this study. Over the 100-day incubation, a small part of C-DFL enantiomer was mineralized to CO (< 10.44 %) or entered the surface water phase (< 6.69 %), with most of the C (> 80.40 %) remaining in the subsoil. The residues in all tested soils were gradually converted from extractable residues (ERs) to nonextractable residues (NERs). At the end of incubation, the fraction of C-NERs reached 5.38-23.77 %. The half-life (t) of the DFL parent in soil is relatively long under submerged anaerobic conditions, especially in Fluvo-aquic soil, up to 277.26-315.07 days, which exceeds the risk threshold recommended by the Stockholm Convention (< 180 days). Soil type and microbial activity influenced the fate of DFL in flooded soils and microbial analysis showed that 2.0 mg kg DFL had no obvious impact on soil bacterial richness and function. Pseudomonas spp. was estimated to be a potentially efficient degrading genus for DFL. No enantioselective behaviors were detected in this study. This research provides a theoretical basis for evaluating the environmental impact and ecological safety of DFL application.