Polyethylene Microplastic-Induced Changes in Soil Properties Mediate Nutrient Accumulation and Growth of Amaranthus...

The impact of microplastic pollution on soil functions and the ecological toxicity to crops is a hotspot in agronomy and environmental science. In this study, a pot experiment was conducted to examine the effects of polyethylene microplastics (PE-MPs) at concentrations of 0.25%, 0.5%, 2.5%, and 5% on the growth, physiological indicators, soil physical and chemical properties, and soil bacterial community diversity of Amaranthus tricolor L. The results showed that adding PE-MPs inhibited the growth of A. tricolor L. stems and leaves, and as the dosage increased, the aboveground fresh weight decreased by 13.5% to 60.7%. At the same time, the chlorophyll content in A. tricolor L. leaves decreased, whereas the malondialdehyde (MDA) content increased by up to 11.8%. When the added dosage of PE-MPs was ≥0.5%, soil porosity and available phosphorus (AP) content significantly decreased, resulting in a significant reduction of 22.1% to 31.3% in the phosphorus content of the aboveground parts of A. tricolor L. compared with controls (CK). High-throughput sequencing results indicated that adding PE-MPs could reduce the Shannon index of the soil bacterial community and increase the Simpson index, suggesting a decrease in diversity. The addition of PE-MPs also altered the structure of the soil bacterial community, increasing the relative abundance of the Acidobacteriota, while the abundance of the Planctomycetota significantly decreased. This study provides a numerical and theoretical basis for evaluating the impact of microplastics on vegetable production and soil ecological environment effects.