聚苯乙烯微塑料（Polystyrene Microplastics，PS）是环境中常见的微塑料，在环境中很容易破碎成更小的纳米塑料。本文通过柱迁移实验研究了离子强度、腐殖酸和粘土矿物对微塑料在多孔介质中迁移的影响。通过共迁移实验，进一步探究了微塑料与Pb/Cr在多孔介质中的共迁移行为。最后通过全细胞生物传感器耦合生物光谱，探究微塑料-重金属复合污染的毒性效应。本文取得以下认识:
（1）离子强度增加，微塑料Zeta电位负电性减弱，同时粒径增加，微塑料与石英砂间的有效排斥力减弱，微塑料的迁移受到抑制。腐殖酸导致微塑料与石英砂之间的排斥力增大，通过抑制团聚来减小悬浮液中微塑料胶体的尺寸，从而促进微塑料迁移。粘土矿物的存在抑制了微塑料的迁移，一方面是由于高岭石边缘存在带正电荷的位点，可以吸附带负电的微塑料，从而阻碍微塑料的迁移。另一方面粘土矿物的存在导致多孔介质孔隙减小或堵塞，从而抑制微塑料在多孔介质中的迁移性。
（2）微塑料与Pb混合后，PS的迁移受到抑制，而APS的迁移能力提高。与Cr混合后，PS的迁移能力提高，而APS的迁移受到抑制。这是由于微塑料与重金属混合后，混合液的Zeta电位发生改变，导致混合液与石英砂间的相互作用力发生变化。在Pb污染的多孔介质中，PS和APS的加入促进介质中滞留的Pb再次释放。而在Cr污染的多孔介质中，PS和APS的加入未导致Cr的活化再释放。在微塑料污染的介质中，Pb和Cr的加入对多孔介质中滞留的PS和APS无明显影响。
（3）全细胞生物传感器的测试表明，PS和Pb单独存在时主要表现为细胞毒性，Cr在中低浓度时主要诱导遗传毒性，在中高浓度下产生细胞毒性。微塑料与Pb复合后，在所有浓度下均表现为细胞毒性，且毒性作用高于其单独存在时的毒性，表明PS对Pb的毒性作用为协同效应。微塑料与Cr复合后，毒性趋势与Cr单独存在时类似。
综上所述，本文对微塑料-重金属复合污染在多孔介质中的迁移规律和毒性效应进行了创新性研究，为地下水微塑料-重金属复合污染的生态风险评估及修复提供理论依据。

Polystyrene Microplastics (PS) are common microplastics in the environment, and PS is easier to break into smaller nanoplastics in the environment than other types of plastics. The effects of ionic strength, humic acid and clay minerals on the migration of microplastics in porous media were studied by column migration experiments The interaction between microplastics and heavy metals in the process of migration was investigated through co-migration experiments of microplastics and Pb/Cd in porous media. Finally, the toxicity effects of microplastics-heavy metal combined pollution were investigated by whole-cell biosensor coupled biospectrum. The main conclusions of this study are as follows:
(1)With the increase of ionic strength, the potential electronegativity of microplastics Zeta decreases, while the particle size increases, and the effective repulsion between microplastics and quartz sand decreases. Humic acid increases the repulsive force between microplastics and quartz sand, and reduces the size of microplastic colloids in the suspension by inhibiting agglomeration, thus promoting microplastics migration. The presence of clay minerals inhibits the migration of microplastics, on the one hand, because there are positively charged sites on the edge of kaolinite, which can adsorb negatively charged microplastics, thus hindering the migration of microplastics. On the other hand, the presence of clay minerals causes the porosity of porous media to decrease or block, thus inhibiting the migration of microplastics in porous media.
(2)After microplastics were mixed with Pb, the migration of PS was inhibited, while the migration ability of APS was improved. After mixing with Cr, the migration ability of PS was improved, while the migration of APS was inhibited. This is because when microplastics are mixed with heavy metals, the Zeta potential of the mixture changes, resulting in a change in the interaction force between the mixture and quartz sand. After microplastics were mixed with Pb, the migration of PS was inhibited,  while the migration ability of APS was improved. After mixing with Cr, the migration ability of PS was improved,  while the migration of APS was inhibited. This is because when microplastics are mixed with heavy metals,  the Zeta potential of the mixture changes,  resulting in a change in the interaction force between the mixture and quartz sand.
(3)Whole cell biosensor tests showed that PS and Pb were mainly cytotoxic when they were alone, Cr induced genotoxicity at low and medium concentrations, and cytotoxicity at high and medium concentrations. When microplastics were combined with Pb, they showed cytotoxicity at all concentrations, and the toxicity was higher than that when the microplastics were alone, indicating that the toxic effect of PS on Pb was synergistic. After microplastics were combined with Cr, the toxicity trend was similar to that when Cr was alone.
In summary, this paper innovatively studies the migration rules and toxic effects of microplastics-heavy metal composite pollution in porous media, providing theoretical basis for ecological risk assessment and remediation of microplastics-heavy metal composite pollution in groundwater.