Microplastics in the soil: A review of distribution, anthropogenic impact, and interaction with soil microorganisms based on meta-analysis

Microplastics (MPs) are widespread anthropogenic pollutants that contaminate the terrestrial environment and serve as vectors of other contaminants. They trigger toxic effects during their migration and transmission, affecting the soil ecosystem and eventually presenting a serious threat to human health via the food chain. However, comprehensive studies on the distribution of MPs in soil and their correlation with human activities and terrestrial ecosystems are still lacking. In this study, we detected a significant difference in the MP size (both for the size <1 mm (P < 0.01) and the size 1-2 mm (P < 0.05)) in China and other countries based on bibliometric and meta-analysis. Principal component analysis revealed regional variations in MP distribution. The correlation analysis between MP characteristics and anthropogenic activities in China further revealed that industrial production was linked to polypropylene microplastics (PP-MPs) abundance (P < 0.01). We also discussed the interaction between soil MPs and ecosystems, such as soil microbial community, since the transportation of MPs was associated with its distribution and environmental factors in the soil. Linear regression analysis further showed that environmental variables, such as culture temperature, were negatively related to MPs' degradation efficiency by the fungi (P < 0.05). This study aims to evaluate the distribution, transfer, and impact of MPs, and their interaction with the soil ecosystem and provides information on the prevention and management of MP pollution in the terrestrial environment.