Department of Environment and Energy, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 05006, South Korea.
Department of Marine Environmental Science, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon 34134, South Korea.
Water Res. 2021 Dec 1;207:117833. doi: 10.1016/j.watres.2021.117833. Epub 2021 Nov 3.
Recently, studies have increasingly focused on the occurrence of plastic leachate and its effects on aquatic environments. However, few studies have aimed to identify microplastic-derived dissolved organic matter (MP-DOM) from environmental samples that are often enriched with natural organic matter (NOM). In this study, three MP-DOM (EPS-DOM, PVC-DOM, and PET-DOM) and eight aquatic NOM samples, and their mixtures, were used to identify a unique optical surrogate for MP-DOM within background NOM. Three major fluorescence peaks (peaks P, H, and L) were identified in the excitation emission matrix (EEM) spectra of both DOM sources (i.e., MP-DOM and NOM). The first two peaks were more pronounced for MP-DOM than for aquatic NOM, whereas peak L showed the opposite trend. The summed intensity ratio of the ranges of the first two peaks relative to peak L, namely, (H + P)/L, clearly distinguished between MP-DOM and NOM samples. The MP-DOM source discrimination capability was compared for several selected spectroscopic indices by tracking their changes in the mixtures of two source groups with increasing fraction of MP-DOM via end-member mixing analysis. This was further evaluated based on the three criteria built on the significance of the difference between the two groups, the correlation coefficients of the regressions, and the minimum fraction of MP-DOM in mixtures that can be distinguished from 100% NOM samples. Irrespective of the plastic type and leaching conditions (i.e., UV-irradiated or not), the new optical index, (H + P)/L, was superior at distinguishing MP-DOM from the mixtures when compared to other commonly used optical indices. The new index can serve as a sensitive, robust, and reliable fluorescence indicator with minimal interference from NOM for detecting plastic leachate in aquatic samples.
最近，越来越多的研究关注塑料浸出物的发生及其对水生环境的影响。然而，很少有研究旨在从通常富含天然有机物（NOM）的环境样品中鉴定出微塑料衍生的溶解有机物（MP-DOM）。在这项研究中，使用了三种 MP-DOM（EPS-DOM、PVC-DOM 和 PET-DOM）和八种水生 NOM 样品及其混合物，以确定背景 NOM 中 MP-DOM 的独特光学替代物。在 DOM 源（即 MP-DOM 和 NOM）的激发发射矩阵（EEM）光谱中鉴定出三个主要荧光峰（峰 P、H 和 L）。前两个峰在 MP-DOM 中比在水生 NOM 中更为明显，而峰 L 则相反。前两个峰的总和强度比相对于峰 L 的范围，即（H + P）/L，清楚地区分了 MP-DOM 和 NOM 样品。通过端元混合分析跟踪两个源组混合物中 MP-DOM 分数增加时几种选定光谱指数的变化，比较了 MP-DOM 源的区分能力。根据两个组之间差异的显著性、回归的相关系数和可以从 100% NOM 样品中区分出来的混合物中 MP-DOM 的最小分数这三个标准，进一步评估了该能力。无论塑料类型和浸出条件（即是否经过 UV 照射）如何，与其他常用光学指数相比，新的光学指数（H + P）/L 在区分 MP-DOM 与混合物方面更为优越。该新指数可作为一种敏感、稳健且可靠的荧光指示剂，在检测水生样品中的塑料浸出物时，受 NOM 的干扰最小。
