Behaviour, ecological impacts of microplastics and cadmium on soil systems: A systematic review

Owing to their low cost, high plasticity, and corrosion resistance, plastic products are widely used across various industries. However, these plastic products can break down into microplastics (MPs) through several processes, including natural weathering, mechanical wear and tear, industrial activities, such as fine powder production, and other human-induced processes. MPs can contaminate the environment and pose a significant threat to human health and safety. Additionally, MPs can be horizontally and vertically distributed within the soil environment. MPs can interact with cadmium (Cd) in Cd-contaminated soils, thereby forming co-exposed stress risks. Considering the widespread distribution of MPs and Cd in soil, this article reviews their interactions and the ecological effects of combined stress through literature visualization and analysis. The systematic review shows that combined MP–Cd pollution can significantly alter the physico-chemical properties of soil, thus influencing individual contaminants (Cd or MPs) and modifying the soil microbial community. The migration of MPs and Cd can contribute to oxidative stress on soil animals and plants, with potential implications for human health through the aboveground food chain. This paper aims to identify future research directions and priorities in addressing combined stress pollution and provide scientific guidance for the remediation and management of MP-Cd joint exposure site environments.