Detection technology and ecological effects of microplastics in soil

Microplastics (MPs), as an emerging environmental pollutant, refers to plastic particles with length or width less than 5 mm. Due to the small particle size, stable properties and difficult degradation, they are widely present in various environmental media. Plastic pollution has become one of the major threats to the function of the earth system. The greatest attention to date has been on their potential effect in marine ecosystems. However, a growing number of studies are examining their potential impact on soil ecosystems. In this paper, worldwide research progress on the separation, extraction, identification and ecological impacts of MPs in soil is reviewed. Finally, the development direction of future research on the microplastics is suggested. At present, the separation methods of microplastics in soil mainly include screening method, density separation, and foam flotation. The common strategy is to first identify obvious/possible microplastics with a microscope and then confirm by spectroscopy and thermodynamic methods such as Fourier transform infrared spectroscopy (FTIR) or Raman spectroscopies. These methods have some shortcomings, such as time consuming and destroying the structure of microplastics. Appropriate combination and improvement of these methods are expected to make up the deficiency. The ecological impact of microplastics is mainly reflected in the growth, development and reproduction of animals. Furthermore, the presence of microplastics will cause changes in soil physical and chemical parameters, which will change vegetative stage, plant photosynthesis and oxidative stress. In addition, nanoscale microplastics can get across plant’s membranes and cell wall barriers and enriched by plants, and poses an additional risk to humans via trophic food chain transfer. The prospects for future research include: (1) standardized analytical methods; (2) dose-responds relationship of microplastics in soil; (3) the ecological of combination and interaction of microplastics with contaminants.