Adsorption behavior of three triazole fungicides on polystyrene microplastics

Environmental pollution caused by microplastics (MPs) and pesticides has become a global challenge, and increasing evidence shows that MPs can adsorb organic pollutants which may affect their distribution and bioavailability. As widely used pesticides, triazole fungicides with potential environmental and human safety risks often coexist with MPs in the environment. Understanding the adsorption behavior is the basis of risk assessment of co-exposure of MPs and triazole fungicides. In this study, the adsorption behavior of three commonly used triazole fungicides on polystyrene (PS) was studied using adsorption test. The influences of PS particle size and environmental factors on adsorption capacity were evaluated, and the adsorption mechanisms were discussed. Results suggested that the adsorption kinetics and isotherm conformed to the Pseudo-second-order and Freundlich model, respectively. The order of adsorption and desorption capacity was hexaconazole (HEX) > myclobutanil (MYC) > triadimenol (TRI), which was positively correlated with LogKow of pesticides. To a certain extent, the decrease in PS particle size and change in solution pH value and increase in salt ion strength all contribute to increasing adsorption capacity. The main mechanisms of adsorption were hydrophobic and electrostatic interactions. MPs can adsorb and may become the source and sink of triazole fungicides in aqueous environments. Our results demonstrate that more attention should be given to the combined water pollution risk of MPs and triazoles fungicides.