Dissolved organic matter (DOM) originating from microplastics (MPs-DOM) is increasingly recognized as a substantial component of aquatic DOM. The photochemistry of MPs-DOM, essential for understanding its environmental fate and impacts, remains largely unexplored. This study investigates the photochemical behaviors of MPs-DOM derived from two common plastics: polystyrene (PS) and polyvinyl chloride (PVC), which represent aromatic and aliphatic plastics, respectively. Spectral and high-resolution mass spectrometry analyses demonstrated that photoreactions preferentially targeted poly-aromatic compounds within the MPs-DOM, leading to degradation products that predominantly form N-aliphatic/lipid-like substances. This transformation is characterized by decreased aromaticity and unsaturation. Additionally, irradiation of MPs-DOM generated reactive species (RS), including triplet intermediates (³DOM*) and singlet oxygen (¹O₂), with apparent quantum yields of 0.06–0.16% and 0.16–0.35%, respectively—values considerably lower than those for conventional DOM (1.19–1.56% for ³DOM* and 1.34–1.90% for ¹O₂). Despite this, the RS generated from MPs-DOM significantly enhance the degradation of coexisting organic pollutants, such as antibiotic resistance genes (ARGs). The findings shed light on the photoinduced transformation of MPs-DOM and suggest that MPs-DOM functions as a natural photocatalyst, mediating redox reactions of pollutants in sunlit aquatic settings. This highlights its previously underestimated role in natural attenuation and aquatic photochemistry.

中文翻译：

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微塑料衍生的溶解有机物的光化学：反应性物质的产生和有机污染物的降解


源自微塑料的溶解有机物 （DOM） （MPS-DOM） 越来越被认为是水生 DOM 的重要组成部分。MPS-DOM 的光化学对于了解其环境命运和影响至关重要，但在很大程度上仍未得到探索。本研究研究了源自两种常见塑料的 MPs-DOM 的光化学行为：聚苯乙烯 （PS） 和聚氯乙烯 （PVC），它们分别代表芳香族和脂肪族塑料。光谱和高分辨率质谱分析表明，光反应优先靶向 MPS-DOM 内的多芳香族化合物，导致主要形成 N-脂肪族/脂质类物质的降解产物。这种转变的特点是芳香性降低和不饱和度。此外，MPS-DOM 辐照产生的反应性物质 （RS），包括三重态中间体 （³DOM*） 和单重态氧 （¹O₂），表观量子产率分别为 0.06-0.16% 和 0.16-0.35%，远低于传统 DOM 的值（³DOM 为 1.19-1.56%，¹O₂ 为 1.34-1.90%）).尽管如此，MPS-DOM 产生的 RS 显着增强了共存有机污染物的降解，例如抗生素耐药基因 （ARG）。这些发现阐明了 MPs-DOM 的光诱导转化，并表明 MPs-DOM 起着天然光催化剂的作用，介导阳光充足的水生环境中污染物的氧化还原反应。这凸显了它以前被低估在自然衰减和水生光化学中的作用。