State Environmental Protection Key Laboratory of Wetland Ecology and Vegetation Restoration, School of Environment, Northeast Normal University, Changchun 130117, P. R. China.
Key Laboratory of Industrial Ecology and Environmental Engineering (MOE), School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, P. R. China.
Environ Sci Technol. 2022 Mar 1;56(5):3085-3095. doi: 10.1021/acs.est.1c07129. Epub 2022 Feb 17.
Nanoplastics (NPs) have become a new type of pollutant of high concern that is ubiquitous in aqueous environments. However, the transport and transformation of NPs in natural waters are not yet fully understood. In this study, the aggregation and photooxidation of NPs were assessed with nanosized polystyrene (PS) as an example, and the effects of dissolved organic matter (DOM) were investigated with Suwannee River fulvic acid (SRFA) as representative DOM. The results showed that simulated sunlight irradiation exhibited negligible effects on the aggregation of PS, while SRFA enhanced its heteroaggregation through hydrophobic interactions. In SRFA solutions, photooxidation of PS with a particle size of 200 nm was observed, which led to an increase in the O/C ratio on its surface at a rate of (2.20 ± 0.40) × 10 h. This indicates the promotional effect of SRFA on the oxidation of nanosized PS, which is attributed to the generation of the excited triplet state (SRFA*), hydroxyl radicals (OH), and singlet oxygen (O). Among these reactive species, O played a crucial role in the oxidation of PS. The findings in this study are helpful for an in-depth understanding of the environmental behavior of NPs in natural waters.
纳米塑料（NPs）已成为一种新型的高关注污染物，广泛存在于水环境中。然而，NPs 在天然水中的迁移和转化过程仍未被充分了解。本研究以纳米级聚苯乙烯（PS）为例，评估了 NPs 的聚集和光氧化作用，并以苏万尼河腐殖酸（SRFA）作为代表性的溶解有机质（DOM），研究了 DOM 的影响。结果表明，模拟太阳光照射对 PS 的聚集几乎没有影响，而 SRFA 通过疏水相互作用促进了其异质聚集。在 SRFA 溶液中，观察到粒径为 200nm 的 PS 发生光氧化，其表面的 O/C 比值以（2.20±0.40）×10-1 h-1 的速率增加。这表明 SRFA 对纳米级 PS 氧化具有促进作用，这归因于激发三重态（SRFA*）、羟基自由基（OH）和单线态氧（O）的生成。在这些活性物质中，O 在 PS 的氧化过程中起着关键作用。本研究的结果有助于深入了解 NPs 在天然水中的环境行为。
