Abstract:Cycloxaprid, a novel neonicotinoid insecticide developed independently in China, has two optical stereoisomers, 1S2R-cycloxaprid and 1R2S-cycloxaprid. The environmental behavior and fate of chiral pesticides in antipode level had great significance to the scientific use and risk assessment of cycloxaprid. The stereoisomer-specific mineralization and bound residue (BR) of cycloxaprid in aerobic soils and flooded paddy soils were studied using14C-isotope tracing, respectively in this study. The results were as follows: No significant difference was observed between the two optical isomers for the mineralization, BR and its distribution in humus at 100 days after the application. Significant difference in the mineralization of the stereoisomers was observed between aerobic and anoxic condition in soils (p<0.05). Under aerobic condition, and the mineralization of cycloxaprid in S1 was the lowest (0.21% to 0.23% of the applied amount), and the highest in S3 (16.45% to 17.06% of the applied). Under anoxic condition, the mineralization of cycloxaprid was less than 1% in all tested soils. Significant difference in the BR of cycloxaprid was observed between aerobic and anoxic conditions in S2 and S3 (p<0.05), while no significant difference was found in S1. The BR in S1 was the lowest under both aerobic and anoxic conditions (56.84% to 64.38% of the applied amount), while the highest in aerobic S2 (79.55% to 82.99% of the applied amount) and in anoxic S3 (73.85% to 84.11% the applied amount), respectively. Bound residue of14C-cycloxaprid distributed in humus showed a tendency of fulvic acid>humin>humic acid in three soils under both aerobic condition and anoxic condition. The results indicated that no significant selectivity difference has been found in the environmental behavior and fate of chiral insecticide, cycloxaprid in soil.