A review of microplastics in the soil environment

Microplastics are plastic particles widely distributed in the environment. In recent years, environmental pollution caused by microplastics has attracted widespread attention. Many studies have reported the negative effects of microplastics on the aquatic environment, but the impact of microplastics on the terrestrial environment, especially on soils, has not been extensively investigated. This study systematically reviewed the recent researches on the sources, distribution, pollution characteristics, analysis methods, ecological effects, environmental effects, and control measures of soil microplastics, and proposed relevant countermeasures for research and governance. This review showed that 1) the sources of soil microplastics included residues of agricultural plastic film, land use of sludge, organic fertilizer application, surface runoff, sewage irrigation, and atmospheric deposition. 2) The methods of separation, extraction, identification, and their advantages and disadvantages for determining soil microplastics were summarized, but standardized detection and quantitative technologies were lacking. 3) Microplastics could affect the soil structure and physical and chemical properties, threatened the growth of plants and animals, and changed the diversity of microbial communities. 4) Microplastics could adhere to pollutants on the surface, causing physical and chemical environmental pollution, endogenous toxic substances releasing, and inducing compound pollution. 5) The prevention and control measures of microplastic pollution were mainly focused on three factors:research and development of biodegradable plastic products, input control of microplastics from the source, and strengthening international cooperation. This study also proposed three areas in need of further development:a standard unified quantitative analysis method, more accurate traceability analysis technology, and better scientific research on microplastic pollution in the soil. The results presented here provided a better understanding of the environmental behavior of microplastics in the soil and proposed ideas for further exploration. This review also provided a theoretical basis and reference for the ecological risk assessment of soil microplastics and prevention of pollution caused by them.