Microplastics (MPs) are considered to influence the bioavailability of heavy metals through direct adsorption, but this neglects the distribution of heavy metal chemical speciation indirectly influenced by MPs by altering geochemical properties. The present study aims to explore the link between the fractionation distribution of cadmium (Cd²⁺) and changes in geochemical properties in sediments induced by polyethylene terephthalate microplastics (PET-MPs). The PET-MPs reduced the acid-soluble fraction of Cd²⁺ in sediments and increased its organically bound fraction. In addition, the concentration of bioavailable Cd²⁺ in the sediment decreased by 4.09 to 25.96% with increasing PET-MPs doses and aging. Whereas the thermal aging of PET-MPs led to a decrease in the molar ratio of oxygen-containing functional groups and the BET surface area, which is not favorable for improving the adsorption capacity of PET-MPs. On the other hand, the correlation analysis demonstrated the key role of PET-MPs in increasing the content of sediment organic matter and its humification level, which indirectly led to a decrease in Cd²⁺ bioavailability. The microbial analysis demonstrated that PET-MPs increase the relative abundances of Chloroflexi, hexokinase, and 6-phosphofructose kinase in sediments, thereby increasing the humification level of sediment organic matter. The present study provides a new perspective for understanding the environmental risks of MPs-altered heavy metals.

微塑料 (MPs) 被认为通过直接吸附影响重金属的生物利用度，但这忽略了 MPs 通过改变地球化学性质间接影响的重金属化学形态分布。本研究旨在探讨镉（Cd ²⁺）的分馏分布与聚对苯二甲酸乙二醇酯微塑料（PET-MPs）引起的沉积物地球化学性质变化之间的联系。^{PET-MPs降低了沉积物中Cd 2+}的酸溶性分数并增加了其有机结合分数。此外，生物可利用 Cd ^2+的浓度随着 PET-MPs 剂量的增加和老化，沉积物中的含量下降了 4.09% 至 25.96%。而PET-MPs的热老化导致含氧官能团摩尔比和BET表面积下降，不利于提高PET-MPs的吸附能力。另一方面，相关性分析表明PET-MPs在增加沉积物有机质含量及其腐殖化水平方面的关键作用，间接导致Cd ²⁺生物利用度的降低。微生物分析表明 PET-MP 增加了Chloroflexi的相对丰度、己糖激酶和沉积物中的 6-磷酸果糖激酶，从而增加沉积物有机质的腐殖化水平。本研究为了解 MPs 改变的重金属的环境风险提供了新的视角。