Microplastics interfere with sorption–desorption, leaching, and mobility of 14C-diflubenzuron, 14C-fluazinam, and 14C-metribuzin in a tropical soil

Pesticides and microplastics (MPs) are contaminants that coexist in agricultural soils; however, little is known about pesticide dynamics in the presence of MPs. Therefore, this study aimed to investigate the environmental behavior of 14 C-diflubenzuron, 14 C-fluazinam, and 14 C-metribuzin under the influence of MPs in a tropical soil. The results showed that, at MPs concentrations of 1 and 4%, the sorption of 14 C-metribuzin in soil was reduced by 40.79% and 51.12%, respectively. For 14 C-diflubenzuron, 4% MPs addition led to a 20.65% reduction in sorption. For 14 C-fluazinam, no interference in environmental behavior was observed. Desorption occurred for all pesticides. In solution, averages of 11% of 14 C-metribuzin, 71% of 14 C-diflubenzuron, and 68% of 14 C-fluazinam were sorbed by MPs. In the same order, 36–93%, 2–2.8%, and 0.51–0.57% of 14 C-metribuzin, 14 C-diflubenzuron, and 14 C-fluazinam were leached. A reduction in the mobility of 14 C-metribuzin was observed, shifting from intermediate mobility to slightly mobile. Meanwhile, 14 C-diflubenzuron and 14 C-fluazinam remained immobile in soil. The results demonstrate that adding different concentrations of MPs to soil alters the environmental behavior of pesticides, depending on particle concentration, physicochemical properties, and pesticide dosage. This study provides insights into the interactions between MPs and pesticides and highlights the role of MPs as vectors of organic contaminants in soil. In addition, these findings suggest that MPs may influence pesticide retention, mobility, and leaching in tropical agricultural soils, with potential implications for groundwater contamination and environmental risk assessment.