Persistence, mobility, and leaching risk of flumioxazin in four Chinese soils

Flumioxan was used to control annual broad-leaved and dicotyledonous weeds. Considering the limited information available, comprehensive investigation of persistence and mobility of flumioxazin in Chinese soil is very important. The degradation, adsorption-desorption, mobility, and leaching risk of flumioxazin in four Chinese soils were investigated under laboratory conditions. The degradation rates of flumioxazin, which correlated with soil moisture, microorganisms, organic matter and pH, were 8.2−50.6 days in the four soils under different conditions. Microorganisms influenced these rates greatly, with half-lives increasing 1.67−2.39-fold. Three possible metabolites were detected by ultrahigh-performance liquid chromatography with high-resolution mass spectrometry, and the metabolic pathways were cleavage of the imide and amide linkages and opening of the cyclic imide. The adsorption capacity of flumioxazin in soil was strongly positively correlated with the soil’s cation exchange capacity (CEC) and organic matter (OM) content, which had correlation coefficients > 0.83. Negative and positive desorption hysteresis effects were observed in Guizhou soil and the other three soils, respectively, which might be related to the different soil constitutions. The mobility was relatively weak in the four Chinese soils and negatively related to CEC and OM content, with correlation coefficients > 0.86. Moreover, the leaching risk of flumioxazin was uncertain for the underground water. The results indicated that flumioxazin was a low-risk herbicide and could be used to evaluate the environmental fate and risk of flumioxazin in soil.