Removal technologies of microplastics in soil and water environments: review on sources, ecotoxicity, and removal technologies

Microplastics (MP) in the environment has attracted extensive attention due to their ubiquitous occurrence and potential toxic effects; but less attention has been given to the removal technologies of MP in different environmental media. This review covers the sources, ecotoxicities, and removal technologies of MP in soil and water environments reported in previous studies to derive the future research directions for MP removal technologies. Previous studies reported various sources contribute to MP present in soil and water environments, indicating that the source control may be a better strategy than contaminated media treatment for management of MP contamination. Similarly, different terrestrial and aquatic organisms have been used to determine the toxic effects of MP with different characteristics. Previous ecotoxicity studies of MP on soil organisms cover only a small number of species compared to that of MP on aquatic organisms. Therefore, further studies are necessary to investigate the ecotoxic effects of MP on a broader range of soil organisms. Also, since the characteristics of MP are diverse, more ecotoxicity studies in both water and soil environments are required. The review provides an overview of various removal technologies for MP in soil and water and identifies gaps in existing studies. Although more studies have been conducted for removal of MP in water than in soil, they remain in their early stages. More studies are needed for removal of MP removal in soil than in water. With MP in water, most studies have been carried out on a lab scale with artificial wastewaters, thus, studies with natural waters in a pilot or field scale are required. Overall, this review highlights the need for further studies on MP removal technologies for real world applications.