A new perspective on understanding soil microplastics: Composition, influencing factors of the soil plastisphere, and its impacts on the environmental behavior of co-existing contaminants

Abstract

Microplastics (MPs), as emerging contaminants, threaten ecosystems, with their soil ecological risks becoming a global concern. When we try to understand the MPs-soil-microbial system and assess the ecological effects of MPs, we cannot ignore the role of soil plastisphere. The presence of MPs in soil may create a unique ecological niche for microorganisms, thereby altering the environmental behavior of MPs. Current review articles on the soil plastisphere remain incomplete. This review comprehensively summarizes existing detection methods for soil MPs and plastisphere communities, including their advantages and limitations. It details the formation mechanisms of the soil plastisphere and its impacts on MPs transport and degradation, where microorganisms play a dominant role. The analysis covers plastisphere-associated bacteria (e.g., Actinobacteria, Proteobacteria and Bacteroidetes) and fungi (Ascomycota and Basidiomycota), as well as key determinants of their community composition (plastic properties and environmental factors). The soil plastisphere may exacerbate ecotoxicological risks posed by co-existing contaminants (e.g., heavy metals, organic contaminants, pathogens, and antibiotic resistance genes) through mechanisms such as enhancing microplastic adsorption/desorption capacities for these contaminants and facilitating horizontal gene transfer of antibiotic resistance genes, thereby altering their environmental behaviors. This review also synthesizes plastisphere-associated remediation technologies for soil MPs pollution. As research on soil MPs grows, the soil plastisphere's role in ecological processes is crucial. Its multifaceted impacts may exacerbate soil MPs risks. This review bridges knowledge gaps by understanding MPs contamination mechanisms through a new perspective–the soil plastisphere. Furthermore, it proposes priority and long-term research directions for pollution assessment and remediation.