Combined toxic effects of polystyrene nanoplastics and lead on Chlorella vulgaris growth, membrane lipid peroxidation, antioxidant capacity, and morphological alterations

In recent years, there has been a significant rise in the utilization of amino-functionalized polystyrene nanoplastics (PS-NH). This surge in usage can be attributed to their exceptional characteristics, including a substantial specific surface area, high energy, and strong reactivity. These properties make them highly suitable for a wide range of industrial and medical applications. Nevertheless, there is a growing apprehension regarding their potential toxicity to aquatic organisms, particularly when considering the potential impact of heavy metals like lead (Pb) on the toxicity of PS-NH. Herein, we examined the toxic effects of sole PS-NH (90 nm) at five concentrations (e.g., 0, 0.125, 0.25, 0.5, and 1 mg/L), as well as the simultaneous exposure of PS-NH and Pb (using two environmental concentrations, e.g., 20 μg/L for Pb (Pb) and 80 μg/L for Pb (Pb)) to the microalga Chlorella vulgaris. After a 96-h exposure, significant differences in chlorophyll a content and algal growth (biomass) were observed between the control group and other treatments (ANOVA, p < 0.05). The algae exposed to PS-NH, PS-NH + Pb, and PS-NH + Pb treatment groups exhibited dose-dependent toxicity responses to chlorophyll a content and biomass. According to the Abbott toxicity model, the combined toxicity of treatment groups of PS-NH and Pb showed synergistic effects. The largest morphological changes such as C. vulgaris' size reduction and cellular aggregation were evident in the medium treated with elevated concentrations of both PS-NH and Pb. The toxicity of the treatment groups followed the sequence PS-NH < PS-NH + Pb < PS-NH + Pb. These results contribute novel insights into co-exposure toxicity to PS-NH and Pb in algae communities.