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-1 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-1 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.

中文翻译：

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金属和海洋微塑料：环境中的吸附与制造过程中的添加相比，以铅为例。

在水生环境中，金属与微塑料缔合有两种方法。首先，它们可以被吸附到塑料表面或在其上的氢-生物累积物，其次，它们可以作为功能添加剂或反应或循环残留物存在于聚合物基质中。在这项研究中，对滩涂海洋微塑料中铅的相关性进行了评估。因此，在小于5 mm的中性彩色聚乙烯颗粒中测定了吸附的Pb，该颗粒中没有在稀王水中通过消化在制造过程中添加的可检测到的Pb，同时使用禽类基于生理的提取试验（PBET）评估了这种缔合的生物可及性。 。在这里，最多约0。1μgg-1的Pb吸附到塑料上，大约60％至70％的金属可接触到。通过对更广泛的滩涂塑料（聚烯烃和聚氯乙烯）进行X射线荧光分析，确定了作为添加剂或残留物存在的铅，并选择了若干磨碎成mm尺寸的阳性样品并进行了PBET。在此，观测到的总Pb浓度高达40,000μgg-1，生物利用度高达16％，生物可利用浓度超过吸附的Pb的当量值几个数量级。与历史性塑料相比，通过摄入历史性塑料中的添加剂和当代塑料中的可回收残留物，对铅和可能有其他有毒金属的摄入更为重要，