Key Laboratory of Water and Sediment Sciences of Ministry of Education, State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, People's Republic of China.
Key Laboratory of Water and Sediment Sciences of Ministry of Education, State Key Laboratory of Water Environment Simulation, School of Environment, Beijing Normal University, Beijing 100875, People's Republic of China.
Water Res. 2022 Jun 1;216:118320. doi: 10.1016/j.watres.2022.118320. Epub 2022 Mar 17.
Reactive oxygen species (ROS) generation is considered as an important photoaging mechanism of microplastics (MPs) and nanoplastics (NPs). To elucidate the ROS-induced MP/NP aging processes in water under UV irradiation, we examined the effects of surface coatings, polymer types and grain sizes on ROS generation and photoaging intermediates. Bare polystyrene (PS) NPs generated hydroxyl radicals (•OH) and singlet oxygen (O), while coated PS NPs (carboxyl-modified PS (PS-COOH), amino-modified PS (PS-NH)) and PS MPs generated fewer ROS due to coating scavenging or size effects. Polypropylene, polyethylene, polyvinyl chloride, polyethylene terephthalate and polycarbonate MPs only generated •OH. For aromatic polymers, •OH addition preferentially occurred at benzene rings to form monohydroxy polymers. Excess •OH resulted in H abstraction, CC scission and phenyl ring opening to generate aliphatic ketones, esters, aldehydes, and aromatic ketones. For coated PS NPs, •OH preferentially attacked the surface coatings to result in decarboxylation and deamination reactions. For aliphatic polymers, •OH attack resulted in the formation of carbonyl groups from peracid, aldehyde or ketone via H abstraction and CC scission. Moreover, O might participate in phenyl ring opening for PS NPs and coating degradation for coated PS NPs. This study facilitates understanding the ROS-induced weathering process of NPs/MPs in water under UV irradiation.
活性氧物种（ROS）的产生被认为是微塑料（MPs）和纳米塑料（NPs）光老化的重要机制。为了阐明紫外线照射下水体中 ROS 诱导的 MP/NP 老化过程，我们研究了表面涂层、聚合物类型和粒径对 ROS 生成和光老化中间体的影响。裸露的聚苯乙烯（PS）纳米颗粒产生了羟基自由基（•OH）和单线态氧（O），而经过羧基改性 PS（PS-COOH）和氨基改性 PS（PS-NH）修饰的 PS 纳米颗粒和 PS 微塑料由于涂层清除或尺寸效应生成的 ROS 较少。聚丙烯、聚乙烯、聚氯乙烯、聚对苯二甲酸乙二醇酯和聚碳酸酯 MPs 仅产生•OH。对于芳香族聚合物，•OH 优先加成在苯环上形成单羟基聚合物。过量的•OH 导致 H 提取、CC 断裂和苯环开环，生成脂肪族酮、酯、醛和芳香族酮。对于经过修饰的 PS 纳米颗粒，•OH 优先攻击表面涂层，导致脱羧和脱氨反应。对于脂肪族聚合物，•OH 攻击导致过酸、醛或酮中的羰基通过 H 提取和 CC 断裂形成。此外，O 可能参与 PS NPs 的苯环开环和 PS NPs 涂层的降解。本研究有助于理解紫外线照射下水体中 NPs/MPs 中 ROS 诱导的风化过程。
