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Polystyrene microplastics enhance oxidative dissolution but suppress the aquatic acute toxicity of a commercial cadmium yellow pigment under simulated irradiation
Summary
Researchers studied how polystyrene microplastics affect the stability and toxicity of cadmium yellow pigment in water exposed to simulated sunlight. They found that the microplastics actually increased the dissolution of the pigment by generating reactive chemical species, but paradoxically reduced its acute toxicity to aquatic organisms. The study reveals that microplastics can alter the environmental behavior of co-existing pollutants in unexpected ways.
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 (k = 0.118 h) under irradiation was visibly increased to 0.144 h by polystyrene (PS) MPs, due to reactive species generation such as O, •OH and PS* , while O was unimportant to this process. The O, humic acid, photoaging status of PS MPs could promote PS MPs-related CdS pigment dissolution rate by modifying reactive species generation. However, the CO, PO and alkaline condition significantly decreased the dissolution rate to 0.091, 0.053 and 0.094 h, respectively, through modifying free Cd stability. Comparably, PS MPs-related CdS pigment dissolution was relatively slow in natural water samples (k = 0.075 h). PS MPs at environmental concentration can also promote CdS pigment dissolution and Cd release, but suppress acute toxicity of CdS pigment to zebrafish larvae as increasing 10 h survival from 65% to 85% by adsorbing the Cd and decreasing Cd 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.