Polystyrene microplastics facilitated the photoconversion of losartan potassium: The pivotal role of aging and reactive oxygen species

As an emerging class of pollutants, microplastics (MPs) coexisting with organic contaminants (OCs) exhibit environmental behaviors that have raised widespread concerns. This study investigated the influence of aged polystyrene microplastics (PSMPs) on the photoconversion of losartan potassium (LSTP) under irradiation. The experimental results indicated that the presence of PSMPs significantly enhanced the photodegradation of LSTP (from 9.11% to 83.32%) and showed a positive linear relationship with the aging degrees. Characterization of PSMPs and quenching experiments revealed that reactive oxygen species (ROS) induced by oxygen-containing groups on the surface of aged PSMPs were responsible for promoting LSTP photodegradation . Singlet oxygen ( 1 O 2 ) dominated and contributed more than 50% with different aging levels of PSMPs involved. Photoconversion products of LSTP were deduced based on density functional theory calculations and liquid chromatography-time of flight-mass spectrometry analysis. Their relative abundance of supported the positive correlation between ROS variations and aging degrees of PSMPs. This study highlights the critical impact of aging MPs on the fate of OCs in the aquatic environment .