Enhanced phototransformation of atorvastatin by polystyrene microplastics: Critical role of aging

Reactive oxygen species (ROS) generated from light irradiation of microplastics (MPs) can potentially affect the environmental fate of organic contaminants when they coexist in the same environment. This study investigated the effect of polystyrene (PS) MPs with different aging degrees on the phototransformation of atorvastatin (ATV) under simulated sunlight. Results showed that the presence of PS MPs facilitated the phototransformation of ATV, and the degradation rate was linearly correlated with the aging degree (i.e., carbonyl index) of MPs. The enhanced effects mainly depended on the contents of oxygen-containing functional groups of PS MPs, which increased the absorption of light energy and the generation of ROS (e.g., singlet oxygen ( 1 O 2 ) and triplet-excited state PS ( 3 PS*)). Quenching experiments indicated that 1 O 2 generated from photosensitization of PS was the major contributor to the increased phototransformation of ATV. Additionally, the role of 3 PS* became more important in the photodegradation mediated by higher degree aged MPs because much more 1 O 2 was generated from the 3 PS* . PS MPs also increased the types and yields of degradation products, especially for higher degree aged MPs, despite the low effect on leachate toxicity. The findings provide a novel insight into the critical role of MPs in the fate of organic contaminants in aquatic environments. • Effect of PS MPs with different aging degrees in simulated sunlit water on the photolysis of ATV was probed. • The correlation of ATV photolysis rate constants versus CI values of MPs was developed. • ROS produced by the irradiated PS were involved in ATV photolysis. • Aging changed the phototransformation mechanism of ATV in the presence of MPs. • Critical impacts of aged MPs mainly depended on the oxygen-containing functional groups.