The Fate Of Cyclosapird In Arobic Soils And The Influence On Microbial Diversity

In recent years, the environmental behavior and fate of chiral pesticides in antipode level have received much attention. Cycloxaprid, a novel neonicotinoid insecticide developed independently in China with good industrialisation prospects for its high activities, has two optical stereoisomers, lS2R-cycloxaprid and lR2S-cycloxaprid.In this study,the stereoisomer-specific fate of cycloxaprid in three tested soils was studied using14C-isotope tracing, and the effect on soil microbial diversity of the two cycloxaprid isomers was studied by high-throughput sequencing techniques. The results were as follows:(1) No significant difference was observed between the two optical isomers inER, BR and mineralization in three tested aerobic soils. Duringthe whole incubation, ER decreased with time, and showed a tendency of S1>S3>S2, while BR and mineralization increased with time, and showed a tendency of S2>S3>S1and S3> S2>S1, respectively. After100d of incubation, the contents of ER reduced to36.44%-38.08%,10.07%-10.81%,9.54%-15.47%of applied amount, while the formation of BR reached to56.84%-61.22%,79.55%-82.99%,66.80%-68.90%of applied amountand the mineralization were0.22%-0.23%,6.69%-7.31%,14.82%-17.06%of appliedamount, respectively.(2) No significant difference was observed beween the two optical isomers in mineralization, ER, BR and itsdistribution in humus in three tested aerobic and flooded soils after100days ofincubation. In S2and S3, the mineralization of cycloxapridunder aerobic condition was apparently higher thananoxic condition, and the residue was more inclined to form BR in aerobic soils.In aerobic and anoxic S1, the mineralization was less than1%of applied amountand the formation of BR was the lowest and showed no difference. The distribution of BR of cycloxaprid in humus showed a tendency of fulvic acid>humin>humic acid in three soils under both aerobic anoxic conditions.(3) No significant difference was observed between the two optical isomers in their effect on soil microbial diversity after100days ofincubation. The difference of bacterial diversityamong the three tested soils was siginificant.The species and relative abundance of mcrobial community in S1were changed significantly by the application of cycloxaprid, while slight change was found in S2and S3.The results indicated no significantenantioselectivitydifference was found in the environmental fate in soil and the effect on soil microbial diversity of the chiral insecticide, cycloxaprid.