Degradation, adsorption, and migration characteristics of fluridone in three types of soils

Fluridone is a widely used herbicide in cotton fields in Xinjiang, but its environmental fate in local typical soils remains unclear. To address this knowledge gap, this study selected three representative cotton field soils (sandy soil, loamy soil, and clay soil) from Xinjiang as test materials and systematically investigated the degradation, adsorption, and migration characteristics of fluridone using the batch equilibrium method, soil thin-layer chromatography, and laboratory-simulated soil column leaching experiments. The results demonstrated that the degradation of fluridone in all three soils followed first-order kinetics, with a half-life of 110.02-161.20 days, classifying it as a moderately persistent pesticide. The degradation rate was co-regulated by temperature, soil moisture content, organic matter content, and microorganisms, with soil microorganisms being the dominant factor-sterilization treatment significantly prolonged the degradation half-life of fluridone to 266.60 days. Regarding migration behavior, the retardation factor (R_f) values for horizontal migration of fluridone ranged from 0.243 to 0.309, indicating that fluridone was immobile in the three soils. For vertical leaching, fluridone was detected only in the leachate of sandy soil at a low concentration, while no leaching loss was observed in loamy and clay soils, suggesting a relatively higher leaching risk in sandy soil. Adsorption kinetic analysis revealed that the adsorption equilibrium of fluridone in soils was reached within 24 h, and the adsorption capacity followed the order of clay soil > loamy soil > sandy soil, which was positively correlated with soil clay and organic matter contents. In summary, fluridone degrades slowly in Xinjiang cotton field soils, its adsorption capacity is increases with soil clay and organic matter content, and its overall migration ability is weak but presents a leaching risk in sandy soil. This study provides key theoretical support for the environmental risk assessment of fluridone, the safe planting of subsequent crops, and the scientific and rational application of fluridone in Xinjiang cotton fields.