School of Geography, Earth and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth, PL4 8AA, UK.
School of Geography, Earth and Environmental Sciences, University of Plymouth, Drake Circus, Plymouth, PL4 8AA, UK; School of Biological and Marine Sciences, University of Plymouth, Drake Circus, Plymouth, PL4 8AA, UK.
Water Res. 2020 Apr 15;173:115577. doi: 10.1016/j.watres.2020.115577. Epub 2020 Jan 31.
There are two means by which metals associate with microplastics in the aquatic environment. Firstly, they may be adsorbed to the plastic surface or hydrogenous-biogenic accumulations thereon, and secondly, they may be present in the polymeric matrix as functional additives or as reaction or recyclate residues. In this study, the relative significance of these associations is evaluated with respect to Pb in beached marine microplastics. Thus, adsorbed Pb was determined in <5 mm, neutrally-coloured polyethylene pellets that contained no detectable Pb added during manufacture by digestion in dilute aqua regia, while the bioaccessibility of this association was evaluated using an avian physiologically-based extraction test (PBET). Here, up to about 0.1 μg g of Pb was adsorbed to the plastic and between about 60 and 70% of the metal was accessible. Lead present as additive or residue was determined by x-ray fluorescence analysis of a wider range of beached plastics (polyolefins and polyvinyl chloride), with a selection of positive samples grated to mm-dimensions and subjected to the PBET. Here, total Pb concentrations up to 40,000 μg g and bioaccessibilities up to 16% were observed, with bioaccessible concentrations exceeding equivalent values for adsorbed Pb by several orders of magnitude. Ingestive exposure to Pb, and potentially other toxic metals, is more important through the presence of additives in historical plastics and recyclate residues in contemporary plastics than from adsorption, and it is recommended that future studies focus more on the environmental impacts and fate of metals bound in this form.
在水生环境中，金属与微塑料结合有两种方式。首先，它们可能被吸附到塑料表面或其表面上的氢生物积聚物上；其次，它们可能作为功能添加剂或作为反应或再循环残留物存在于聚合物基质中。在这项研究中，针对海滩上的海洋微塑料中的 Pb，评估了这些结合的相对重要性。因此，通过在稀王水中消化来确定<5mm、中性色聚乙烯颗粒中吸附的 Pb，这些颗粒在制造过程中未添加可检测到的 Pb，而通过禽类生理相关提取测试（PBET）评估了这种结合的生物可利用性。在这里，高达约 0.1μg/g 的 Pb 被吸附到塑料上，并且约 60%至 70%的金属是可利用的。通过对更广泛的海滩塑料（聚烯烃和聚氯乙烯）进行 X 射线荧光分析来确定作为添加剂或残留物存在的 Pb，选择一些阳性样本切成 mm 尺寸并进行 PBET。在这里，观察到总 Pb 浓度高达 40,000μg/g 和生物可利用度高达 16%，而生物可利用浓度超过吸附 Pb 的等效值几个数量级。通过添加剂存在于历史塑料中以及通过吞食摄入 Pb 和潜在其他有毒金属，对环境的影响和这种形式结合的金属的命运更为重要，因此建议未来的研究更侧重于研究这种形式结合的金属的环境影响和命运。
