Compared with the widespread and serious heavy metal contamination in soils, microplastic pollution has gained attention only recently. Little is known about how microplastics affect the distribution of heavy metals in soils, especially across soil components level. In this study, a 180-day soil aging experiment and soil density fractionation were performed to investigate the effect of polypropylene (PP) microplastics on the binding behavior of cadmium (Cd) to solid components, i.e. particulate organic matter, organo-mineral complexes (OMC), and mineral. Results showed addition of 2–10% microplastics in soils induced the decomposition of OMC fraction by 10.88–23.10%. Compared to the control, the content of dissolved organic carbon increased, and pH, humic substances, and soil organic matter decreased with microplastics. After 180d of aging, the content of Cd in OMC fraction increased by 17.92%, while microplastics made Cd contents decline by 10.01–19.75%. The impacts strongly depended on the dose and surface characteristic of microplastics. Overall, PP microplastics increased the concentration of bioavailable Cd in soils via decreasing soil retention of Cd by the OMC fraction. These findings based on the solid components level will provide a new perspective for understanding microplastics effects on soil systems and pollutants.

与土壤中广泛而严重的重金属污染相比，微塑料污染直到最近才受到关注。关于微塑料如何影响重金属在土壤中的分布，尤其是在土壤成分水平上的分布，人们知之甚少。在这项研究中，进行了为期 180 天的土壤老化实验和土壤密度分级，以研究聚丙烯 (PP) 微塑料对镉 (Cd) 与固体成分（即颗粒有机物、有机矿物复合物）结合行为的影响（ OMC）和矿物。结果表明，在土壤中添加 2-10% 的微塑料会导致 OMC 部分分解 10.88-23.10%。与对照相比，微塑料溶解有机碳含量增加，pH值、腐殖质和土壤有机质降低。经过180d的老化，OMC组分中Cd含量增加了17.92%，而微塑料使Cd含量下降了10.01-19.75%。这些影响在很大程度上取决于微塑料的剂量和表面特性。总体而言，PP 微塑料通过减少 OMC 部分对 Cd 的土壤保留，增加了土壤中生物可利用 Cd 的浓度。这些基于固体成分水平的发现将为理解微塑料对土壤系统和污染物的影响提供新的视角。