Potential Impacts of Microplastic Particle Size and Type on Soil Properties and Buckwheat Performance

Microplastics (MPs), as emerging pollutants, have elicited global concerns. However, few studies have evaluated MPs with varying sizes and their adverse effects on plant growth in farmland soils. In this study, a greenhouse pot experiment was conducted to evaluate the effects of polyethylene (PE) and polybutylene adipate terephthalate (PBAT) with two particle sizes (100 μm and 1000 μm) on the growth, photosynthetic properties, and antioxidant enzyme activity of buckwheat (Fagopyrum esculentum Moench), as well as soil properties. Overall, the results showed that MPs had a certain inhibitory effect on buckwheat growth, especially with the PE treatment of 100 μm particle size. The addition of PE and PBAT inhibited photosynthesis, induced oxidative stress, and decreased soil nutrient availability (specifically ammonium nitrogen, nitrate nitrogen, available potassium, and available phosphorus content), reducing above and belowground biomass. In addition, we observed that the type and size of MPs had a significant effect on buckwheat growth parameters. Degradable MPs (PBAT) showed less toxicity than non-degradable MPs (PE), and MPs with a smaller microplastic particle size (100 μm) displayed a greater inhibitory effect than larger ones (1000 μm). In conclusion, MPs showed significant inhibitory effects on the growth of buckwheat plants, highlighting the necessity for further research in this area.