Insights into microplastics in the soil environment: Migration, biodegradation, toxicity and risk assessment

Abstract

Microplastics (MPs) are a growing environmental concern, with expanding areas of harm. The soil environment is the main site for the production, consumption and even disposal of plastics and plastic products, and thus faces the serious issue of microplastic contamination. This article reviews the migration, biodegradation, toxicity and risk assessment of MPs in soil environment. Biological action and abiotic action jointly cause the migration of MPs in the soil, and their migration path is also influenced by the soil properties, microplastic self-structure, and natural factors. The diversity of microplastic migration may pose a challenge in detecting MPs. Biodegradation of MPs in soil includes microbial degradation and soil microfauna degradation. The mechanism of biodegradation relies on enzymes that break down MPs within the organism. It has been demonstrated that MPs can exert toxic effects on plants, which include the alteration of external soil conditions or the hazard on the plant itself, occurring at various stages of plant growth and development. The Pollution Load Index (PLI) and the Polymer Hazard Index (PHI) are the most commonly used methods for assessing the environmental risk of MPs.