Toxic mechanisms of environmentally relevant titanium dioxide nanoparticles to Chlorella under coupled...

The toxicity of titanium dioxide nanoparticles (TiO₂ NPs) to Chlorella at environmentally relevant concentrations under multiple coexisting environmental conditions remains poorly understood. Here, a full factorial design was employed to assess the main and interactive effects of major environmental factors on the behavior and toxicity of TiO₂ NPs under controlled multifactor conditions. TiO₂ NPs exhibited concentration-dependent effects, shifting from marked growth inhibition at high concentrations to growth stimulation at an environmentally relevant concentration. Dissolved organic matter (DOM), Illumination, Salinity, and nitrogen availability all modified NP behavior and algal responses. In particular, Illumination and DOM showed a significant interactive effect, with increases in biomass, chlorophyll content, and ROS but no detectable lipid peroxidation, indicating an adaptive cellular response of Chlorella to TiO₂ NPs exposure. Overall, these results suggest that TiO₂ NPs toxicity to Chlorella is highly context dependent and associated with changes in heteroaggregation behavior, photosynthesis, oxidative stress, and metabolic processes. This study provides insights for the ecological risk assessment of NPs in natural aquatic environments.