Accumulation and fate of microplastics in soils after application of biosolids on land: A review

The recent discovery of microplastic occurrence in most ecosystems is raising health concerns globally, yet the fate of microplastics is poorly known, particularly in the terrestrial environment. Here, we review the effect of land applications of biosolids on microplastic contamination in agricultural soils. We focus on separation and identification methods, distribution in wastewater, and retention, migration and degradation in soils. We also discuss the uptake of microplastics by microorganisms. The number of microplastic particles in biosolids ranges from 506 to 15,385 per kg of biosolids. After biosolid application on land, microplastic number ranges from 18 to 6.9 × 105 particles per kg of soil, depending on the soil composition. Microplastic retention in soils increases with soil organic carbon concentration, Fe and Al oxide concentrations, and soil ionic strength. Biodegradation of microplastics causes mass loss, changes in chemical composition, reduction in molecular weight and mechanical strength, and gas production of carbon dioxide and methane.