Polyethylene microplastics modulate zinc oxide nanoparticle toxicity: Effects on nutrient dynamics and rhizosphere bacterial community in pakchoi

The coexistence of zinc oxide nanoparticles (ZnO NPs) and polyethylene microplastics (PE-MPs), driven by industrial and agricultural activities, raises concerns about their combined impacts on the environment. However, the mechanisms by which PE-MPs influence the biological effects of ZnO NPs remain poorly understood. This study explored the effects of varying doses of PE-MPs and ZnO NPs simultaneously and ZnO NPs alone on pakchoi (Brassica rapa subsp. chinensis), focusing on nutrient uptake, elemental distribution, soil bacterial communities, and environmental risks. Exposure to 900 mg kg⁻¹ ZnO NPs alone significantly reduced pakchoi shoot and root dry weights by 50.3 % and 62.6 %, respectively, while increasing Zn accumulation in both tissues. Conversely, co-exposure with PE-MPs mitigated the phytotoxic effects of ZnO NPs, decreasing Zn uptake in pakchoi. Additionally, ZnO NPs alone significantly reduced soil bacterial α-diversity, with ACE and Chao1 indices decreasing by 34.5 % and 37.5 %, respectively, compared to the control. However, the presence of PE-MPs reversed these adverse effects on microbial diversity. This research uncovers how PE-MPs regulate ZnO NPs biological toxicity, establishing a scientific groundwork for assessing the co-exposure's toxicological mechanisms and environmental risks.