Department of Environment and Energy, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul, 05006, South Korea.
Department of Marine Biology and Oceanography, Institut de Ciències del Mar-CSIC, Barcelona, 08003, Spain.
Water Res. 2020 May 15;175:115678. doi: 10.1016/j.watres.2020.115678. Epub 2020 Mar 4.
Although there are numerous studies concerning the occurrence of microplastics (MP) in the environment and its impact on the ecosystem, dissolved organic matter (DOM) leached from MP (MP-DOM) has received little attention, and its characteristics have been rarely examined. It is presumed that the DOM leaching from plastics could be accelerated when plastics lost their protective additives during their transport and weathering processes in aquatic systems. In this study, two additive-free MPs (or micro-sized plastic polymers) were leached in artificial freshwater under UV irradiation and dark conditions. The leached DOM was characterized by typical analyses for naturally occurring DOM (N-DOM) such as dissolved organic carbon (DOC), size exclusion chromatography (SEC), and Fourier-transform infrared spectroscopy (FTIR). The potential to generate trihalomethanes (THMs), a well-known environmental impact of N-DOM, was also explored for the DOM with plastic origins for the first time. The leaching results demonstrated that UV irradiation promoted the leaching of DOM from the plastic polymers with an amount corresponding to ∼3% of the total mass of the polymers. The leached amounts were much greater than those previously reported using commercial plastics which presumably contained protective additives. The SEC results revealed that, different from typical aquatic N-DOM, MP-DOM is mostly composed of low molecular weight fractions <350 Da. For the two polymer types (polyethylene and polypropylene), the MP-DOM exhibited a high potential to form THMs upon chlorination, which was comparable to those of typical aquatic N-DOM. This study highlighted an overlooked contribution of UV irradiation to the DOM leaching from additive-free plastics and the potential risk of MP-DOM to produce toxic disinfection byproducts (DBPs) upon chlorination.
尽管有许多关于环境中微塑料（MP）的发生及其对生态系统的影响的研究，但从 MP 中浸出的溶解有机物质（MP-DOM）却很少受到关注，其特性也很少被研究。据推测，当塑料在水生系统中运输和风化过程中失去保护添加剂时，从塑料中浸出的 DOM 可能会加速。在这项研究中，在 UV 照射和黑暗条件下，将两种无添加剂的 MP（或微塑料聚合物）浸提在人工淡水中。用典型的天然存在的 DOM（N-DOM）分析方法，如溶解有机碳（DOC）、尺寸排阻色谱（SEC）和傅里叶变换红外光谱（FTIR）对浸出的 DOM 进行了表征。还首次探索了源自塑料的 DOM 产生三卤甲烷（THMs）的潜力，THMs 是 N-DOM 的一种众所周知的环境影响。浸出结果表明，UV 照射促进了塑料聚合物中 DOM 的浸出，其浸出量相当于聚合物总质量的约 3%。浸出量远大于以前使用含有保护添加剂的商业塑料所报道的量。SEC 结果表明，与典型的水生 N-DOM 不同，MP-DOM 主要由 <350 Da 的低分子量部分组成。对于两种聚合物类型（聚乙烯和聚丙烯），MP-DOM 在氯化时表现出很高的形成 THMs 的潜力，与典型的水生 N-DOM 相当。本研究强调了 UV 照射对无添加剂塑料中 DOM 浸出的被忽视的贡献，以及 MP-DOM 在氯化时产生有毒消毒副产物（DBPs）的潜在风险。
