Ecotoxicological Impacts of Microplastics and Cadmium Pollution on Wheat Seedlings

As plastic and heavy metal pollution continue to escalate, the co-occurrence of microplastics and heavy metals in the environment poses significant threats to ecosystems and human health. This study was designed to explore the combined effects of polyethylene microplastics (PE-MPs) and cadmium (Cd) pollution on wheat seedlings, focusing on antioxidant enzyme activity and Cd bioaccumulation. At low concentrations of PE (1mg·L-1), peroxidase (POD) activity in wheat shoots slightly increased without significance, while at higher concentrations (50mg·L-1 and 100mg·L-1) of PE, POD activity was significantly inhibited compared to 0mg·L-1 PE treatment. At Cd exposure activity, with POD activity in the shoots increasing by 73.7% at 50μmol·L-1Cd2+ compared to 0μmol·L-1 Cd treatment. When wheat seedlings were exposed to a combination of 50 mg·L-1 PE and Cd at different concentrations Cd, significant differences in POD activity were observed in the shoots compared to the control group, showing an upward trend with increasing Cd concentration. However, the addition of PE suspension generally reduced POD activity in wheat shoots compared to Cd treatment alone. Specifically, the presence of 50mg·L-1 PE did not significantly alter POD activity in the wheat shoots (p>0.05). Furthermore, exposure to different concentrations of Cd resulted in a general increase in POD activity of roots, with significant differences observed at 5μmol·L-1 and 25μmol·L-1 Cd (p<0.05). Regarding Cd bioaccumulation, at Cd low concentrations (1μmol·L-1 and 5μmol·L-1), PE significantly promoted Cd accumulation in the shoots. However, at high Cd concentrations (50μmol·L-1), PE microplastics reduced Cd accumulation in the shoots but promoted its accumulation in the roots.These results suggest that PE microplastics influence the bioavailability of Cd, mitigating the toxic effects of high Cd concentrations. This paper scientifically elucidates the ecotoxicological effects of co-contamination for microplastics and heavy metals, also their potential impacts on agricultural production are discussed.