Inorganic anions influenced the photoaging kinetics and mechanism of polystyrene microplastic under the simulated sunlight: Role of reactive radical species

•The presence of inorganic anions promoted indirect photoaging of PS-MP.••OH dominated the indirect photoaging of PS-MP in the anion solution.•CO3•- induced by the reaction of HCO3- and •OH oxidated PS-MP.••OH and RHS were responsible for PS-MP indirect photoaging in the halide solution.