Issues in Regulating Microplastic Content in Soils

Abstract— The growing pollution of soils with microplastics—plastic particles smaller than 5 mm—is one of the pressing anthropogenic threats requiring specific regulatory and control measures. The aim of this review was to analyze the existing regulatory framework and systematize modern data on the sources, scale, and methods of reducing soil microplastics pollution. A pronounced dissonance was identified between the scale of soil microplastics pollution and the state of the legal framework. The absence of maximum permissible concentrations (MPCs), monitoring standards, and obligatory international agreements complicates the regulation. The main sources of microplastics input have been revealed: the primary source of microplastics is agricultural soils due to the application of sewage sludge, compost, controlled-release fertilizers, encapsulated agrochemicals, polymer-coated seeds, and mulching films. The median global concentration of microplastics in soils is 112 particles/kg, but the variation between different countries is enormous–from 12 to 863 particles/kg. If current practices persist, projections indicate a potential increase in concentration up to 6699.8 mg/kg over 50–100 years. Physical, chemical, and biological remediation methods are considered. It is argued that biological remediation method, including phytoremediation, application of soil fauna, and microbial degradation are the most techniques of soil purification from microplastics—polyethylene, polystyrene, polyethylene terephthalate, polylactic acid, etc.