The potential of microplastics to act as a vector for anthropogenic contaminants is of rising concern. However, directly quantitatively determining the vector effects of microplastics has been rarely studied. Here, we present a dual-dosing method that simulates the chemical bioaccumulation from soil and microplastics simultaneously, wherein unlabeled hydrophobic organic contaminants (HOCs) were spiked in the soil and their respective isotope-labeled reference compounds were spiked on the polyethylene microplastics. The comparison of the bioavailability, i.e., the freely dissolved concentration in soil porewater and bioaccumulation by earthworm, between the unlabeled and isotope-labeled HOCs was carried out. Relatively higher level of bioavailability of the isotope-labeled HOCs was observed compared to the unlabeled HOCs, which may be attributed to the irreversible desorption of HOCs from soil particles. The average relative fractions of bioaccumulated isotope-labeled HOCs in the soil treated with 1 % microplastics ranged from 6.9 % to 46.4 %, which were higher than those in the soil treated with 0.1 % microplastics. Treatments with the smallest microplastic particles were observed to have the highest relative fractions of bioaccumulated isotope-labeled HOCs, with the exception of phenanthrene, suggesting greater vector effects of smaller microplastic particles. Biodynamic model analysis indicated that the contribution of dermal uptake to the bioaccumulation of isotope-labeled HOCs was higher than that for unlabeled HOCs. This proposed method can be used as a tool to assess the prospective vector effects of microplastics in complex environmental conditions and would enhance the comprehensive understanding of the microplastic vector effects for HOC bioaccumulation.

中文翻译：

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微塑料对蚯蚓疏水性有机污染物生物累积的尺寸依赖性载体效应：双剂量研究

微塑料作为人为污染物载体的潜力日益引起人们的关注。然而，直接定量确定微塑料的矢量效应的研究很少。在这里，我们提出了一种双剂量方法，同时模拟土壤和微塑料的化学生物累积，其中将未标记的疏水性有机污染物（HOC）添加到土壤中，并将其各自的同位素标记的参考化合物添加到聚乙烯微塑料上。对未标记和同位素标记的 HOC 的生物利用度（即土壤孔隙水中的自由溶解浓度​​和蚯蚓的生物积累）进行了比较。与未标记的 HOC 相比，同位素标记的 HOC 具有相对较高水平的生物利用度，这可能归因于 HOC 从土壤颗粒中不可逆解吸。用 1% 微塑料处理的土壤中生物累积同位素标记的 HOCs 的平均相对分数范围为 6.9% 至 46.4%，高于用 0.1% 微塑料处理的土壤中的相对分数。据观察，使用最小的微塑料颗粒进行处理时，生物累积的同位素标记的 HOC 的相对分数最高（菲除外），这表明较小的微塑料颗粒的载体效应更大。生物动力学模型分析表明，真皮摄取对同位素标记的HOCs生物累积的贡献高于未标记的HOCs。该方法可用作评估复杂环境条件下微塑料的预期矢量效应的工具，并将增强对 HOC 生物累积的微塑料矢量效应的全面理解。