Compost as a carrier for microplastics and plastic-bound toxic metals into agroecosystems

Research on microplastics (MPs) primarily focuses on the abundance in different ecosystems, ecotoxicology, and health aspects. The primary focus is now on structural and physicochemical changes in soil, ecotoxicology, and influence on plant growth performance. Compost is considered one of the prime sources of MPs in agricultural environments, where MPs in compost can influence the carbon cycle in copious ways, such as soil microbial processes, plant growth, or litter decomposition. Microplastics are reported in the range of 10–2800 item kg−¹ in compost from various countries. Most importantly, compost can be a carrier for MP-bound toxic trace metals into the agroecosystems. It has been identified that different toxic metals are associated with the MPs in compost, i.e. Cr, Pb, Cu and Ni; however, no considerable attention is given to the study of their concentrations, translocation, and fate. As the addition of MPs changes the physical, chemical, and biological properties of soil, which leads to a change in toxic trace metal fractionation and partitioning, as reported in the literature. Importantly, future research needs to capture the toxic metal mobilization and immobilization in terms of chemistry, aging, size, aggregation, and shape of MPs.