A critical review of co-pollution of microplastics and heavy metals in agricultural soil environments.

The soil environment is a primary destination for contaminants such as microplastics (MPs) and heavy metals (HMs), which are frequently detected simultaneously. The long-term coexistence of MPs and HMs in the soil necessitates unavoidable interactions, affecting their environmental chemical behavior and bioavailability. These co-contaminants pose potential threats to soil organism growth and reproduction, crop productivity, food security, and may jeopardize human health via the food chain. This paper summarizes the sources and trends of MPs in the soil environment, along with the mechanisms and current research status of MP adsorption or desorption of HMs. Additionally, this paper reviews factors affecting HM adsorption on MPs, including MP properties, HM chemical properties, and other environmental factors. Lastly, the effects of MPs and HMs on soil ecology and human health are summarized. The interaction mechanisms and potential biological effects of their co-contamination require further exploration. Future research should delve deeper into the ecotoxic effects of MP–HM co-contamination at cellular and molecular levels, to provide a comprehensive reference for understanding the environmental behavior of their co-contamination in soil. [Display omitted] • MP–HM co-contamination significantly spatially overlaps in Chinese agricultural soils. • Formation mechanisms and factors influencing MP–HM co-contamination are discussed. • MPs can serve as "Trojan horse" for HMs, leading to co-toxicity. • Effects of MP–HM co-contamination on soil ecological environment are reviewed. • Research gaps of soil MPs and co-contamination of other pollutants are elucidated. [ABSTRACT FROM AUTHOR]