Background

The contamination of aquatic ecosystems with both anthropogenic pollutants and particles in particular (microscopic) plastic debris items is of emerging concern. Since plastic particles can accumulate contaminants and potentially facilitate their transport, it is important to properly investigate sorption mechanisms. This is especially required for a large variety of chemicals that can be charged under environmental conditions and for which interactions with particles may hence go beyond mere partitioning.

Results

In this study, sorption experiments with two types of microplastic particles (polyethylene and polystyrene) and 19 different contaminants (pesticides, pharmaceuticals, and personal care products) were performed at three different pH values. We could show that sorption to plastic particles is stronger for hydrophobic compounds and that neutral species usually contribute more to the overall sorption. Bulk partitioning coefficients were in the same order of magnitude for polyethylene and polystyrene. Furthermore, our results confirm that partition coefficients for polar compounds can only be accurately determined if the solid-to-liquid ratio in batch experiments is more than 6–7 orders of magnitude higher than any plastic concentration detected in the environment. Consequently, only a minor fraction of pollutants in water bodies is associated with microplastics.

Conclusions

Although neutral species primarily dominate the overall sorption, hydrophobic entities of ionic species cannot be neglected for some compounds. Notwithstanding, our results show that since microplastic concentrations as currently observed in the environment are very low, they are only a relevant sorbent for strongly hydrophobic but not for polar compounds.

中文翻译：

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一项结合实验和建模研究，以评估极性和非极性化合物对聚乙烯和聚苯乙烯微塑料的 pH 依赖性吸附。

背景

人为污染物和颗粒特别是（微观）塑料碎片对水生生态系统的污染引起了人们的关注。由于塑料颗粒会积聚污染物并可能促进其运输，因此正确研究吸附机制非常重要。这对于在环境条件下可以带电的多种化学物质尤其需要，因此与颗粒的相互作用可能超出单纯的分配范围。

结果

在这项研究中，在三种不同的 pH 值下对两种类型的微塑料颗粒（聚乙烯和聚苯乙烯）和 19 种不同的污染物（农药、药品和个人护理产品）进行了吸附实验。我们可以证明，疏水化合物对塑料颗粒的吸附更强，而中性物质通常对整体吸附的贡献更大。聚乙烯和聚苯乙烯的体积分配系数在同一数量级。此外，我们的结果证实，只有当批量实验中的固液比比环境中检测到的任何塑料浓度高 6-7 个数量级以上时，才能准确确定极性化合物的分配系数。所以，

结论

尽管中性物质主要主导整体吸附，但对于某些化合物，离子物质的疏水实体不能忽略。尽管如此，我们的结果表明，由于目前在环境中观察到的微塑料浓度非常低，它们仅是强疏水性的相关吸附剂，而不是极性化合物的相关吸附剂。