Objective Soil colloids play important roles in the adsorption and migration process of microplastic particles due to their huge specific surface areas, small particle sizes and large amount of charges. However, the influence of soil colloids, especially in agricultural soils, on the migration of microplastic particles, and the mechanism of their co-migration are still unclear. The nebulous definitions of soil colloids and microplastic particles, and the varied classification criteria have hindered the deep research on them as well. Reviewing the relative researches at home and abroad aimed to clarify the interaction between soil colloids and microplastic particles during the downward migration of soil, and to provide scientific foundation for the formulation of relevant policies and measures in the remediation of microplastic particle contaminated soil.

Major advances Agricultural practices has changed the composition of soil colloids and the migration of microplastic particles. The soil colloids and microplastic particle themselves and their porous character, soil physicochemical properties as well as environmental conditions are the main factors, through their co-facilitation and co-inhibition to influence the migration of colloids and microplastic particles in agricultural soils. Soil colloid composition is the dominant factor in the migration process, and the stability of soil colloid particles determines their co-migration status with microplastic particles. The adsorption behavior of soil colloid particles alters the migration pathways and rates of microplastic particles; the presence of microplastic particles can in turn affect the stability of soil colloid particles, therefrom change their aggregation potential and affect the migration capacity of colloid particles.

Outlook In the future, specific research should be carried out about the details of the migration mechanisms of colloids and microplastic particles in different agricultural soils. Quantitative analysis methods should be studied to assess the environmental risks of the co-migration, and the interaction of soil colloids-microplastics particles-micorganism, so to provide new ideas and references for the remediation of contaminated soils and the maintenance of soil health.