Microplastics in the Land and Soil

Soil is the region of origin and dominant sink for the microplastics and acts as the primary source of plastic pollutants delivered to the fresh, brackish, and saline water ecosystems, besides other spheres such as atmosphere and biosphere. The terrestrial regions act as receptors of microplastics from a myriad ways including sewage sludge and compost, irrigation, plastic mulching, littering, atmospheric deposition, and runoff from road. Studies have shown a decreasing trend of microplastic pollutant concentrations from the top surface towards deeper regions of the soil profile. There is evidence of horizontal movement of microplastics that distributes adsorbed pollutants to groundwater and aquatic ecosystems, playing a catalytic role in the biogeochemical characteristics of the soil biota and affecting biodiversity, which may result in concerns for human health. The soil organisms interact within complex food webs in nature, and changes in one or several groups of soil organisms can have further consequences on the abundance, diversity, and functioning of other groups in the food web. Lack of intensive studies on microplastics in the soil is due to the difficulty of separating and quantifying plastic particles and the paucity of standardized separation methods.