Polystyrene microplastics enhance oxidative dissolution but suppress the aquatic acute toxicity of a commercial cadmium yellow pigment under simulated irradiation

Abstract

Commercial cadmium yellow (CdS) pigment widely coexist with microplastics (MPs) in surface water, thus it is important to understand how MPs affect CdS pigment stability and toxicity under irradiation. Herein, the dissolution of CdS pigment (krelease = 0.118 h–1) under irradiation was visibly increased to 0.144 h–1 by polystyrene (PS) MPs, due to reactive species generation such as 1O2, •OH and 3PS* , while O2•− was unimportant to this process. The O2, humic acid, photoaging status of PS MPs could promote PS MPs-related CdS pigment dissolution rate by modifying reactive species generation. However, the CO32−, PO43− and alkaline condition significantly decreased the dissolution rate to 0.091, 0.053 and 0.094 h–1, respectively, through modifying free Cd2+ stability. Comparably, PS MPs-related CdS pigment dissolution was relatively slow in natural water samples (krelease = 0.075 h–1). PS MPs at environmental concentration can also promote CdS pigment dissolution and Cd2+ release, but suppress acute toxicity of CdS pigment to zebrafish larvae as increasing 10 h survival from 65% to 85% by adsorbing the Cd2+ and decreasing Cd2+ bioavailability. This study emphasized the environmental risks and human safety of CdS pigment should be carefully evaluated in the presence of PS MPs in aquatic environments.