Abstract：
The fate of ubiquitous microplastics (MPs) is largely influenced by dissolved organic matter (DOM) in aquatic environments, which has garnered significant attention. The reactivity of DOM is reported to be greatly regulated by molecular weights (MWs), yet little is known about the effects of different MW DOM on MP aging. Here, the aging behavior of polystyrene MPs (PSMPs) in the presence of different MW fulvic acids (FAs) and humic acids (HAs) was systematically investigated. Under ultraviolet (UV) illumination, O/C of PSMPs aged for 96 h surged from 0.008 to 0.146 in the lower MW FA (FA<1kDa) treatment, suggesting significant PSMP aging. However, FA exhibited a stronger effect on facilitating PSMP photoaging than HA, which can be attributed to the fact that FA<1kDa contains more quinone and phenolic moieties, demonstrating a higher redox capacity. Meanwhile, compared to other fractions, FA<1kDa was more actively involved in the increase of different reactive species yields by 50-290%, including •OH, which plays a key role in PSMP photoaging, and contributed to a 25% increase in electron-donating capacity (EDC). This study lays a theoretical foundation for a better understanding of the environmental fate of MPs.
摘要：
无处不在的微塑料（MPs）的命运在很大程度上受到水生环境中溶解有机物（DOM）的影响。这引起了极大的关注。据报道，DOM的反应性受分子量（MWs）的极大调节，然而，关于不同MWDOM对MP老化的影响知之甚少。这里,系统研究了聚苯乙烯MPs（PSMPs）在不同MW富里酸（FAs）和腐殖酸（HAs）存在下的老化行为。在紫外线(UV)照射下,在较低MWFA（FA<1kDa）处理中，老化96h的PSMPs的O/C从0.008激增至0.146，提示PSMP显著老化。然而,FA对促进PSMP光老化的作用比HA更强，这可以归因于FA<1kDa含有更多的醌和酚部分，显示更高的氧化还原能力。同时,与其他分数相比，FA<1kDa更积极地参与不同反应性物种产量增加50-290％，包括•OH,在PSMP光老化中起着关键作用，并贡献了25％的电子供给能力（EDC）增加。本研究为更好地理解国会议员的环境命运奠定了理论基础。
