Most studies assessing the effects of microplastics (MPs) on freshwater ecosystems use reference materials of a certain size, shape, and polymer type. However, in the environment, aquatic organisms are exposed to a mixture of different polymers with different sizes and shapes, resulting in different bioaccessible fractions and effects. This study assesses the fate and effects of an environmentally relevant mixture of high-density polyethylene (HDPE) fragments, polypropylene (PP) fragments, and polyester (PES) fibres in indoor freshwater microcosms over 28 days. The MP mixture contained common polymers found in freshwater ecosystems, had a size range between 50 and 3887 µm, and was artificially aged using a mercury lamp. The invertebrate species included in the microcosms, Lymnea stagnalis (snail) and Lumbriculus variegatus (worm), were exposed to four MP concentrations: 0.01, 0.05, 0.1 and 1 % of sediment dry weight. MPs fate was assessed by performing a balance of the MPs in the surface water, water column, and sediment after a stabilization period and at the end of the experiment. Sedimentation rates per day were calculated (2.13 % for PES, 1.46 % for HDPE, 1.87 % for PP). The maximum size of MPs taken up by the two species was determined and compared to the added mixture and their mouth size. The size range taken up by L. variegatus was smaller than L. stagnalis and significantly different from the size range in the added mixture. The No Observed Effect Concentrations (NOECs) for the reproduction factor of L. variegatus and the number of egg clutches produced by L. stagnalis were 0.01 % and 0.1 % sediment dry weight, respectively. The EC10 and EC50 for the same endpoint for L. stagnalis were 0.25 % and 0.52 %, respectively. This study shows that current MP exposure levels in freshwater sediments can result in sub-lethal effects on aquatic organisms, highlighting the importance of testing MP mixtures.

中文翻译：

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在简单的淡水微观世界中，与环境相关的塑料微粒混合物的归宿和影响


大多数评估微塑料 （MP） 对淡水生态系统影响的研究都使用一定大小、形状和聚合物类型的参考材料。然而，在环境中，水生生物会暴露于不同大小和形状的不同聚合物的混合物中，从而产生不同的生物可及部分和效果。本研究评估了高密度聚乙烯 （HDPE） 碎片、聚丙烯 （PP） 碎片和聚酯 （PES） 纤维在 28 天内在室内淡水微观世界中的环境相关混合物的归宿和影响。MP 混合物包含在淡水生态系统中发现的常见聚合物，尺寸范围在 50 至 3887 μm 之间，并使用汞灯人工老化。微观世界中包含的无脊椎动物物种 Lymnea stagnalis（蜗牛）和 Lumbriculus variegatus（蠕虫）暴露于四种 MP 浓度：沉积物干重的 0.01、0.05、0.1 和 1 %。通过在稳定期后和实验结束时对地表水、水柱和沉积物中的 MPs 进行平衡来评估 MP 的命运。计算每天的沉降率（PES 为 2.13 %，HDPE 为 1.46 %，PP 为 1.87 %）。确定两个物种占据的 MP 的最大大小，并与添加的混合物和它们的嘴大小进行比较。L. variegatus 占据的大小范围小于 L. stagnalis，并且与添加的混合物中的大小范围显着不同。栓塞乳杆菌繁殖因子的无观察效应浓度 （NOECs） 和 L. stagnalis 产生的卵窝数分别为 0.01 % 和 0.1 % 沉积物干重。L. stagnalis 相同终点的 EC10 和 EC50 分别为 0.25 % 和 0。52 % 这项研究表明，目前淡水沉积物中的 MP 暴露水平会对水生生物产生亚致死影响，这凸显了测试 MP 混合物的重要性。