Evaluation of degradation of a novel sulfone bactericide in soils: identification of degradation product and kinetics study

Abstract

Fubianezuofeng is a novel bactericide that shows good inhibitory activity on rice bacterial leaf streak and leaf blight. In this study, the probable influencing factors such as light, soil moisture, soil types, temperature, soil sterilization, and soil organic matter on this bactericide degradation were investigated. The results showed that the degradation experiments of Fubianezuofeng follow the first-order kinetics equation. The rate of degradation was remarkably affected by the types of soil with the degradation half-life t1/2 3.89, 5.21, 4.56, 7.22, 213.05, and 137.29 h for Tianjin, Hefei, Guiyang, Nanning, Harbin, and Changsha soils, respectively. The high moisture and increased temperature can accelerate its degradation rate in soil. Moreover, the degradation rate was faster under non-sterilized condition (t1/2 9.24 days) than under sterilized condition (t1/2 31.51 days) and removed organic matter from soil (t1/2 57.76 days). And the degradation under ultraviolet light (t1/2 0.47 days) was the fastest followed by xenon light (t1/2 5.42 days) and dark condition (t1/2 9.24 days). Finally, the major degradation product, named 2-(4-fluorobenzyl)-5-methoxy-1,3,4-oxadiazole, was identified by ultra-high-performance liquid chromatography equipped with high-resolution mass spectrometry, and the probable mechanism and degradation pathway of FBEZF under the present experimental conditions were proposed in soil. This research can be helpful for the security evaluation of FBEZF and provide some useful data for further investigations and developments on sulfone pesticides in the agricultural and environmental field.