Feedback, synergy and antagonism between microplastics and soil organisms

Soil organisms are key connectors within ecosystems. In recent years, large amounts of pollutants, such as microplastics (MPs), from various sources including industrial emissions and vehicle exhaust, have been released into the soil. MPs are characterized by strong hydrophobicity, and high specific surface area, thus posing various potential issues. However, current research on MPs mainly focuses on aquatic ecosystems, with relatively few studies on the effects of soil biological factors. Furthermore, due to the complexity and diversity of soil biotic environments, the responses to MPs may vary, presenting either positive or negative outcomes. For example, MPs increased the content of nitrogen-fixing bacteria and aerobic microorganisms, but decreased the abundance of soil ascomyces; MPs may be ingested by soil animals, potentially causing toxic effects, or nutritional disturbances, especially earthworms; MPs can also affect plant growth through direct contact with roots or by affecting chemicals in soil, such as wheat and tomatoes. Of concern is that MPs may accumulate in soil over a long period of time, which could lead to a biomagnification effect, with wider impacts on the entire ecosystem through the food chain. Therefore, to further elucidate the processes and mechanisms of interaction between MPs and soil biological factors, this paper reviews the effects of MPs on the soil biotic environment. Additionally, It compares the synergistic or antagonistic effects, and possible mechanisms of different biological indicators under MPs stress. However, these mechanisms of action are still not fully understood and need further research and exploration.