Graduate Institute of Environmental Engineering, National Taiwan University, 71, Chou-Shan Rd., Taipei, 106, Taiwan.
Graduate Institute of Environmental Engineering, National Taiwan University, 71, Chou-Shan Rd., Taipei, 106, Taiwan.
Chemosphere. 2022 Mar;290:133352. doi: 10.1016/j.chemosphere.2021.133352. Epub 2021 Dec 16.
Microplastics (MPs) have received much attention in recent years because of their continuous photoaging process in aquatic environments. However, little research has been conducted on the photochemistry of aged microplastics and the associated effects on coexisting pharmaceuticals. This study investigated the photodegradation of cimetidine via aged polystyrene microplastics (PS-MPs) with different aging times (0-7 d) under simulated sunlight irradiation (700 W/m). PS-MPs with 5 d of aging time resulted in much faster cimetidine degradation (>99%) after 2 h of irradiation than pristine PS-MPs (<8%). The enhanced photodegradation of cimetidine by aged PS-MPs was related to the increase in chromophoric oxygenated groups (CO, C-O) followed by redshifted absorbance through the photoaging process, which induced the formation of the environmentally persistent free radicals (EPFRs) OH, O and PS*. However, only O and PS* contributed to enhanced cimetidine photodegradation, with O playing a more important role in our case. This work also demonstrated that other compounds that are susceptible to indirect photolysis, such as codeine and morphine, are likewise significantly degraded under irradiation in the presence of aged PS-MPs. Although previous studies have reported how MPs can increase the persistence of contaminants, this study demonstrates that MPs can serve as photosensitizers and alter the fate of coexisting pharmaceuticals in aquatic environments.
近年来，由于微塑料（MPs）在水生环境中的持续光老化过程，它们受到了广泛关注。然而，对于老化微塑料的光化学反应及其对共存药物的相关影响的研究甚少。本研究通过模拟太阳光照射（700 W/m），考察了不同老化时间（0-7 d）的老化聚苯乙烯微塑料（PS-MPs）对西咪替丁的光降解作用。结果表明，老化 5 d 的 PS-MPs 在辐照 2 h 后可使西咪替丁的降解速度（>99%）明显快于原始 PS-MPs（<8%）。老化 PS-MPs 增强西咪替丁光降解与其光老化过程中发色含氧基团（CO、C-O）增加和吸光度红移有关，这诱导了环境持久性自由基（EPFRs）OH、O 和 PS的形成。然而，只有 O 和 PS对增强西咪替丁的光降解有贡献，在我们的研究中 O 起了更重要的作用。本研究还表明，其他易发生间接光解的化合物，如可待因和吗啡，在存在老化 PS-MPs 的情况下，辐照下也会显著降解。虽然先前的研究报告了 MPs 如何增加污染物的持久性，但本研究表明 MPs 可以作为光增感剂，改变共存药物在水生环境中的命运。
