A Review of Microplastics in Soil: Distribution Within Pedosphere Compartments, Environmental Fate, and Effects

Microplastics (MPs) have been detected in various environmental media and have become a global hot environmental issue. However, the current distribution of MPs in soils in different regions, the migration and transformation of MPs, and their effects on soil ecology are still unclear. Therefore, this review summarizes the recent literature on soil MPs and gains the following key insights. The abundance of soil MPs is mainly affected by the land-use type and soil layer. The particle size range observed during the experiment also causes differences in the number of MPs. The migration of MPs is influenced by soil chemical (mineralogical composition, pH, and ionic strength), physical (porosity, water holding capacity, and texture) properties, and biological factors (soil fauna activity and plant root growth). When MPs degrade, the surface cracks, the specific surface area increases, and oxygen-containing functional groups such as carboxyl, aldehyde, and hydroxyl groups are produced. MPs reduce the stability of soil aggregates and change the community structure and functional gene abundance of microorganisms, affecting the organic carbon and nitrogen cycling processes. This review will help enhance the effective control of soil MPs and provide a theoretical reference to the mechanisms of their effects on soil carbon and nitrogen cycles.