It is well known that microplastics (MPs) may experience weathering and aging under ultraviolet light (UV) irradiation, but it remains unclear if these processes are impacted by natural components, such as clay minerals. In this study, we systematically investigated the photodegradation behaviors of polyvinyl chloride (PVC) and poly (ethylene terephthalate) (PET), two utmost used plastics, in the presence of clay minerals (kaolinite and montmorillonite). The results demonstrated that the clay minerals, particularly kaolinite, significantly promoted the MPs photodegradation, and the aging of PET was more prominent. The photodegradation was the most distinct at pH 7.0, regardless of the presence or absence of the clay minerals. The results of electron paramagnetic resonance and inhibition experiments of reactive oxygen species indicated that the minerals, particularly kaolinite, remarkably facilitated production of •OH, which was the key species contributing to the photodegradation of MPs. Specifically, UV irradiation facilitated the photo-ionization of MPs, producing hydrated electrons and MP radical cations (MP⁺). The Lewis base sites prevalent on the clay siloxane surfaces could stabilize the MP radical cations and prevent their recombination with hydrated electrons, which promoted the generation of •OH under aerobic conditions, and facilitated the degradation of MP. Two-dimensional (2D) Fourier transformation infrared (FTIR) correlation spectroscopy (COS) analysis and ultra-high-performance liquid chromatography coupled to a Q Exactive Orbitrap HF mass spectrometer were used to identify the sequential changes of functional groups, and the degradation products of the MPs. This study improves our understanding on the aging of MPs in the complex natural environment.

众所周知，微塑料 (MP) 可能会在紫外线 (UV) 照射下经历风化和老化，但这些过程是否受到粘土矿物等天然成分的影响尚不清楚。在这项研究中，我们系统地研究了聚氯乙烯 (PVC) 和聚对苯二甲酸乙二醇酯 (PET) 这两种最常用的塑料，在粘土矿物（高岭石和蒙脱石）存在下的光降解行为。结果表明，粘土矿物，特别是高岭石，显着促进了 MPs 的光降解，而 PET 的老化更为突出。无论是否存在粘土矿物，光降解在 pH 7.0 时最为明显。电子顺磁共振和活性氧抑制实验结果表明，矿物，特别是高岭石，显着促进了•OH的产生，这是促进MPs光降解的关键物种。具体而言，紫外线照射促进了 MP 的光电离，产生了水合电子和 MP 自由基阳离子（MP⁺ )。粘土硅氧烷表面普遍存在的路易斯碱位可以稳定 MP 自由基阳离子并防止它们与水合电子复合，这促进了在有氧条件下的 •OH 的生成，并促进了 MP 的降解。二维 (2D) 傅里叶变换红外 (FTIR) 相关光谱 (COS) 分析和超高效液相色谱与 Q Exactive Orbitrap HF 质谱联用，用于鉴定官能团的连续变化和降解产物议员。这项研究提高了我们对复杂自然环境中 MP 老化的理解。