Wang Qiongjie, Gu Wanqing, Chen Huijuan, Wang Shurui, Hao Zijing
School of Energy and Environment, Anhui University of Technology, Maanshan, Anhui 243002, China.
J Hazard Mater. 2024 Dec 5;480:136154. doi: 10.1016/j.jhazmat.2024.136154. Epub 2024 Oct 12.
The occurrence of dissolved organic matter (DOM) derived from microplastics (MPs) and its effect on aquatic systems has attracted great interest recently. However, the photoaging effect on the molecular structure of MP-derived DOM (MP-DOM) remains unclear. This paper presents the characteristics of DOM leached from three commercial MPs, i.e., polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET) under UV irradiation. With prolonged aging periods, the surface roughness and oxygen-containing groups on the surface of MPs increase as more DOM leachate is generated. Moreover, the dissolved organic carbon (DOC) content of the leached DOM from PET MPs varies from 0.52 mg/L to 2.25 mg/L, which is higher than PE and PP MPs, due to the larger increased surface reaction area and the cleavage of the benzene ring. According to the excitation-emission matrix and parallel factor analysis (EEM-PARAFAC), the plastic-derived protein/phenolic-like components (C1 and C3) in MP-DOM were changed into photo-induced humic-like components (C2), which were closely related to the intermediates during photo-oxidation. High-performance liquid chromatography-mass spectrometry (HPLC-MS) analysis further identified that the highest proportion of antioxidants (24.8 %∼34.6 %) was contained in MP-DOM. Plasticizers, intermediate additives, and antimicrobial agents were also detected in DOM leachate. Correlation analysis identified that the composition of leached DOM was positively correlated with the surface roughness, the carbonyl index (CI), and the chemical groups of MPs. Moreover, a partial least square structural equation model (PLS-SEM) analysis further verified that the change of morphology and the chemical structure of MPs could affect the DOM structures and fractions directly. This study provides an in-depth understanding of the composition of MP-derived DOM during the aging process, as well as a comprehensive environmental impact assessment of MPs.
微塑料（MPs）衍生的溶解有机物（DOM）的产生及其对水生系统的影响最近引起了极大关注。然而，光老化对MP衍生DOM（MP-DOM）分子结构的影响仍不清楚。本文介绍了三种商用MPs，即聚乙烯（PE）、聚丙烯（PP）和聚对苯二甲酸乙二酯（PET）在紫外线照射下浸出的DOM的特性。随着老化时间的延长，MPs表面粗糙度和含氧基团增加，同时产生更多的DOM渗滤液。此外，PET MPs浸出的DOM的溶解有机碳（DOC）含量在0.52mg/L至2.25mg/L之间变化，高于PE和PP MPs，这是由于表面反应面积增加较大以及苯环的裂解。根据激发-发射矩阵和平行因子分析（EEM-PARAFAC），MP-DOM中塑料衍生的蛋白质/酚类成分（C1和C3）转变为光诱导的腐殖质类成分（C2），这与光氧化过程中的中间体密切相关。高效液相色谱-质谱（HPLC-MS）分析进一步确定，MP-DOM中抗氧化剂的比例最高（24.8%∼34.6%）。在DOM渗滤液中还检测到了增塑剂、中间添加剂和抗菌剂。相关性分析表明，浸出DOM的组成与MPs的表面粗糙度、羰基指数（CI）和化学基团呈正相关。此外，偏最小二乘结构方程模型（PLS-SEM）分析进一步验证了MPs的形态和化学结构变化可直接影响DOM的结构和组分。本研究深入了解了老化过程中MP衍生DOM的组成，以及对MPs的综合环境影响评估。
