College of Natural Resources and Environment, Northwest A & F University, Yangling 712100, China.
College of Natural Resources and Environment, Northwest A & F University, Yangling 712100, China; Key Laboratory of Plant Nutrition and the Agri-environment in Northwest China, Ministry of Agriculture, Yangling 712100, China.
Sci Total Environ. 2023 Feb 1;858(Pt 1):159845. doi: 10.1016/j.scitotenv.2022.159845. Epub 2022 Oct 29.
Light irradiation is considered as most important process for the aging of microplastics (MPs); however, which factors drive the process is still unknown. This study investigated the role of typical environmental factors including ultraviolet (UV), oxygen, temperature and physical abrasion in the photoaging of polystyrene (PS) in freshwater. Results showed that UV irradiation and abrasion were dominant factors for affecting photoaging of PS based on dynamic analysis in the property of MP itself and leachate. Especially, when both factors worked together on MPs, they caused more destructive effect. Mechanical exploration revealed that photoaging of MPs was mainly controlled by reactive oxygen species (ROS, O) generated from the reaction of dissolved oxygen/water molecules with polymer radicals initiated by UV energy. As an attacker on MPs, ROS formation was significantly linked with UV intensity, highlighting the important role of UV. The fragmentation was correlated to abrasion intensity, where a higher abrasion generated stronger physical force to tear MPs into fragments. The low roles of oxygen and temperature were presumably related to multiple effects of ROS formation and UV absorption. The findings firstly clarify the drivers in the photoaging of MPs, and contribute our effort to assess their fate and pollution risk in the environment.
光照被认为是导致微塑料（MPs）老化的最重要过程；然而，哪些因素驱动这一过程尚不清楚。本研究调查了包括紫外线（UV）、氧气、温度和物理磨损在内的典型环境因素在淡水中聚苯乙烯（PS）光老化中的作用。结果表明，基于 MP 本身和浸出物性质的动态分析，UV 照射和磨损是影响 PS 光老化的主要因素。特别是当这两个因素同时作用于 MPs 时，它们会造成更具破坏性的影响。机械探索表明，MPs 的光老化主要受溶解氧/水分子与聚合物自由基反应产生的活性氧物种（ROS，O）控制，该反应由 UV 能量引发。ROS 的形成与 UV 强度显著相关，突显了 UV 的重要作用。作为 MPs 的攻击物，ROS 的形成与紫外线强度有关，这表明较高的磨损会产生更强的物理力将 MPs 撕裂成碎片。氧气和温度的作用较低，可能与 ROS 形成和 UV 吸收的多种影响有关。这些发现首次阐明了 MPs 光老化的驱动因素，并有助于我们评估它们在环境中的命运和污染风险。
