Department of Environment and Energy, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 05006, South Korea.
Department of Ocean Environmental Sciences, Chungnam National University, Daejeon, 34134, South Korea.
Water Res. 2021 Feb 15;190:116775. doi: 10.1016/j.watres.2020.116775. Epub 2020 Dec 23.
Despite numerous studies on microplastics (MPs), little attention has been paid to the dissolved organic substances leached from MPs and their environmental fate. In this study, we explored the copper-binding characteristics of MP-derived dissolved organic matter (MP-DOM) leached from several MP types, including commercial polypropylene, polyvinylchloride, and expanded polystyrene, under dark and UV irradiation conditions. The copper-binding affinity of MP-DOM was examined using fluorescence quenching method based on different fluorophores identified via the excitation emission matrix-parallel factor analysis (EEM-PARAFAC). The heterogeneous distribution of binding sites across the functional groups of MP-DOM was further elucidated by utilizing two-dimensional correlation spectroscopy (2D-COS) based on Fourier transform infrared spectroscopy (FTIR). Phenol/protein-like fluorescence prevailed in all MP-DOM samples, whereas humic-like fluorescence was more pronounced in the irradiated MP-DOM. For all tested plastic types, two plastic-derived fluorescent components (C2 and C3) exhibited substantial fluorescence quenching with increasing copper concentrations. The calculated stability constants showed larger differences between the two leaching conditions than between the three MP types with higher log K values for the UV-irradiated (4.08-5.36) than dark-treated MP-DOM (1.05-3.60). The binding constants were comparable to those of natural organic matter with aquatic/terrestrial origins. The 2D-COS results further revealed that the oxygen-containing structures in MP-DOM generated by UV irradiation might be responsible for the higher binding affinity of the irradiated MP-DOM. This is the first study demonstrating the environmental reactivity of MP-DOM towards metal binding, highlighting the importance of leaching conditions for the metal-binding behavior of MP-DOM.
尽管已经有大量关于微塑料 (MPs) 的研究，但很少有人关注从 MPs 浸出的溶解有机物及其环境归宿。在这项研究中，我们在黑暗和紫外光照射条件下，探索了从几种 MPs 类型（包括商用聚丙烯、聚氯乙烯和膨胀聚苯乙烯）浸出的 MPs 衍生的溶解有机物（MP-DOM）的铜结合特性。我们使用荧光猝灭法，根据通过激发发射矩阵平行因子分析（EEM-PARAFAC）鉴定的不同荧光团，研究了 MP-DOM 的铜结合亲和力。通过利用基于傅里叶变换红外光谱（FTIR）的二维相关光谱（2D-COS），进一步阐明了 MP-DOM 中功能基团之间结合位点的非均相分布。所有 MP-DOM 样品中都存在酚/蛋白质样荧光，而辐照 MP-DOM 中则更明显地存在类腐殖质荧光。对于所有测试的塑料类型，两种塑料衍生的荧光成分（C2 和 C3）随着铜浓度的增加，表现出显著的荧光猝灭。计算得到的稳定常数在两种浸出条件之间的差异大于三种 MPs 类型之间的差异，紫外光照射的 MP-DOM（4.08-5.36）的 log K 值高于黑暗处理的 MP-DOM（1.05-3.60）。结合常数与水生/陆生来源的天然有机物相当。2D-COS 结果进一步表明，紫外光照射下 MP-DOM 中含氧结构的生成可能是辐照 MP-DOM 具有更高结合亲和力的原因。这是首次证明 MPs 衍生的溶解有机物对金属结合的环境反应性的研究，强调了浸出条件对 MPs-DOM 金属结合行为的重要性。
