Regulation strategies of microplastics with different particle sizes on cadmium migration processes and toxicity in...

It is still unclear whether there are differences in the effects of microplastics with different particle sizes on the environmental behavior of cadmium (Cd) in the soil-crop system. By introducing the polystyrene microplastics (PS-MPs) with 0.2, 2, and 20 μm, this study explored the regulation strategies of different-sized MPs on the migration and toxicity of Cd in the soil-pakchoi system. Compared to the Cd treatment, the mobility factor of Cd in the soil decreased by 12.97 %, 34.73 %, and 40.12 % with increasing particle sizes of PS-MPs, while the relative binding intensity increased significantly. The 0.2 μm PS-MPs had no effect on Cd content in pakchoi, however, 2 and 20 μm PS-MPs significantly reduced the Cd content in shoots and roots of pakchoi by 47.40 %-29.67 % and 44.56 %-20.92 %, respectively. Additionally, 20 μm PS-MPs reduced the enrichment of the heavy Cd isotope in pakchoi. The results of principal component analysis (PCA) and structural equation modeling (SEM) indicated that 2 and 20 μm PS-MPs may promote the growth of pakchoi by regulating soil properties, nutrient uptake, Cd accumulation, and antioxidant system activity. This study provides evidence for the importance of particle size of MPs in regulating the environmental behavior of heavy metals.