Department of Environment and Energy, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 05006, South Korea.
Department of Environment and Energy, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 05006, South Korea.
Water Res. 2020 Dec 15;187:116426. doi: 10.1016/j.watres.2020.116426. Epub 2020 Sep 19.
Microplastic (MP) pollution is an increasing global problem due to the ubiquity of these particles in the environment and the uncertainty surrounding their fate. Most MPs undergo extensive weathering in the environment, which may result in the release of dissolved organic matter (DOM) into the aqueous phase. In this study, for the first time, we examined the adsorptive behavior of MP-derived DOM (MP-DOM) on minerals (kaolinite and goethite) using DOM samples leached from commercial plastics including polyvinylchloride (PVC) and polystyrene (PS) under dark and ultraviolet (UV) irradiation conditions. MP-DOM was characterized by a higher distribution of relatively smaller-sized molecules than natural organic matter (NOM). The PS-derived DOM (PS-DOM) leached under UV treatment exhibited more oxygen-containing groups than their counterparts in the dark. MP-DOM also exhibited net negative charges at neutral pH ranges. Adsorption isotherm experiments revealed that the mineral surfaces had high adsorption affinities for both types of MP-DOM, which is likely associated with both electrostatic attraction and ligand exchange. The extent of adsorption was greater for the UV-irradiated than the dark-treated DOM, and on goethite compared to kaolinite. The Fourier-transform infrared (FTIR) spectra of the residual PS-DOM after adsorption revealed differences in the adsorption affinities between its functional groups. Two-dimensional correlation spectroscopy for the irradiated PS-DOM showed that preferential adsorption occurred on minerals in the sequential order of oxidized structures → (PS monomers) → carboxylates in additives → carbonyl groups. The adsorption isotherm model parameters for MP-DOM were comparable to those obtained from aquatic/terrestrial NOM, which suggests that plastic-derived DOM can interact with minerals as strongly as NOM. This study highlights the overlooked role played by plastic-derived DOM in mineral-enriched environments, opening new opportunities for improving our understanding of the fate and environmental impacts of MPs.
微塑料（MP）污染是一个日益严重的全球性问题，这是由于这些颗粒在环境中的普遍存在以及它们命运的不确定性所致。大多数 MPs 在环境中会经历广泛的风化，这可能导致溶解有机物（DOM）释放到水相。在这项研究中，我们首次研究了从商业塑料（包括聚氯乙烯（PVC）和聚苯乙烯（PS））中浸出的 DOM 样品在黑暗和紫外（UV）照射条件下对矿物（高岭土和针铁矿）的 MP 衍生 DOM（MP-DOM）的吸附行为。与天然有机物（NOM）相比，MP-DOM 的特征是分布着相对较小的分子。在 UV 处理下浸出的 PS 衍生 DOM（PS-DOM）比在黑暗条件下的同类物含有更多的含氧基团。MP-DOM 在中性 pH 范围内也表现出净负电荷。吸附等温线实验表明，矿物表面对两种类型的 MP-DOM 都具有高吸附亲和力，这可能与静电吸引和配体交换有关。与黑暗处理的 DOM 相比，UV 辐照的 DOM 的吸附程度更大，并且在针铁矿上的吸附程度大于高岭土。吸附后残留 PS-DOM 的傅里叶变换红外（FTIR）光谱显示了其官能团吸附亲和力的差异。辐照 PS-DOM 的二维相关光谱表明，在矿物上优先吸附的顺序为氧化结构→（PS 单体）→添加剂中的羧酸盐→羰基。MP-DOM 的吸附等温线模型参数与水生/陆地 NOM 获得的参数相当，这表明塑料衍生 DOM 可以与矿物相互作用，与 NOM 一样强烈。这项研究强调了塑料衍生 DOM 在富含矿物质的环境中被忽视的作用，为改善我们对 MPs 的命运和环境影响的理解提供了新的机会。
