Fate of microplastics in soil-water systems: View from free radicals driven by global climate change

Microplastics are ubiquitously distributed and persistently present in soil-water systems, posing potential ecological and health risks worldwide. Free radicals are highly reactive in soil-water systems, particularly at soil-water-air interface. The dynamic changes of free radicals sensitive to environmental conditions may greatly impact the fate of microplastics. However, the pathways, reaction kinetics, or transformation products of microplastic degradation by free radicals in soil-water systems remains unclear. Climate change alters the physical and chemical environment of soil-water systems and this transformation can directly affect the degradation of microplastics, or indirectly influence it by altering the generation and species of free radicals. Here, we summarized and analyzed the impact of fluctuations in free radicals (such as superoxide radicals, hydrogen peroxide, peroxyl radicals, and hydroxyl radicals) in soil-water systems on the degradation of microplastics and their derivants. We also discussed how changes in free radicals driven by climate change affect the fate of microplastics. By integrating aspects such as climate change, free radical chemistry, and microplastic pollution, this work delineates the critical issues of microplastic pollution exacerbated by environmental condition changes. In response to the existing challenges and deficiencies in current research, feasible countermeasures are proposed. This work offers valuable insights for future research on predicting and controlling ecotoxicity and health risks caused by microplastics associated with global climate change.