Microplastics (MPs) and heavy metals are ubiquitous pollutants in the aquatic environment. In this study, the sorption behavior of two typical MPs (PVC and PE) to bivalent zinc ions (Zn(II)) and their combined toxic effects on Chlorella vulgaris were systemically studied. The growth inhibition rate, the activities of photosynthesis and antioxidant enzymes (SOD and CAT), the cell membrane integrity and the cell apoptosis rate were employed to evaluate the toxicity. Our result showed that PVC and PE have different adsorption capacities for Zn(II), and the combined exposure to Zn(II) and MPs had distinct patterns on the inhibition of the cell growth and induction of oxidative stress. Under our experimental concentrations, PE and Zn(II) showed a synergistic effect, while PVC and Zn(II) exhibited an antagonistic effect. Finally, an action mechanism was proposed to explain the experimental phenomena. This study demonstrated that flow cytometry can be a powerful tool to study the toxic effect of MP composites, and MPs can not only allow a free ride for the water contaminants, but also remarkably alter their toxic effects on phytoplankton. These effects deserve further consideration during evaluation of ecological risks of MPs in the water environment.

微塑料 (MPs) 和重金属是水环境中普遍存在的污染物。在这项研究中，两种典型的 MPs（PVC 和 PE）对二价锌离子（Zn(II)）的吸附行为及其对小球藻的综合毒性作用进行了系统的研究。采用生长抑制率、光合作用和抗氧化酶（SOD和CAT）活性、细胞膜完整性和细胞凋亡率来评价毒性。我们的结果表明，PVC 和 PE 对 Zn(II) 具有不同的吸附能力，并且 Zn(II) 和 MPs 的联合暴露对细胞生长的抑制和氧化应激的诱导具有不同的模式。在我们的实验浓度下，PE 和 Zn(II) 表现出协同作用，而 PVC 和 Zn(II) 表现出拮抗作用。最后，提出了一种作用机制来解释实验现象。这项研究表明，流式细胞仪可以成为研究 MP 复合材料毒性作用的有力工具，而且 MP 不仅可以让水污染物搭便车，但也显着改变了它们对浮游植物的毒性作用。在评估水环境中 MPs 的生态风险时，这些影响值得进一步考虑。