The combined microplastics and heavy metals contamination between the soil and aquatic media: A review

Microplastics (MPs) and heavy metals (HMs) are pervasive pollutants in both soil and aquatic environments, where they interact to form composite contaminants that pose significant ecological risks. Although some progress has been made in understanding MPs-HMs composite pollution within a single environmental medium, their concentrations can vary by up to three orders of magnitude across different matrices, leading to differing ecological impacts. Furthermore, the mechanisms underlying their interactions and their biological effects remain poorly understood. Therefore, this paper reviews recent progress in domestic and international research and provides an overview of the effects of variations in soil and aquatic environments (acidity, salinity, temperature, organic matter, and other contaminants) and the MP characteristics (types, particle diameter, and aging) on MPs-HMs composite pollution, compares the interaction mechanisms and biological effects of MPs-HMs across different environmental media, and assesses the potential environmental risks associated with MPs-HMs contamination in both soil and aquatic systems. The overall aim of this review is to improve our understanding of the differences in MPs-HMs complex pollution in different environmental media and to provide a theoretical basis for developing innovative strategies for the integrated prevention and management of emerging and legacy pollutants across multiple environmental media.