AlO nanoparticle impact on the toxic effect of Pb on the marine microalga Isochrysis galbana.

The rapid development and application of nanotechnology have led to increasing concern about the environmental implications of released nanomaterials and potential risks to public health and aquatic ecosystems. Information on the joint effect of nanomaterials and co-existing contaminants such as heavy metals is still inadequate. Our work investigated the effect of Al2O3 nanoparticles (NPs; nano-Al2O3) on the toxic effect of Pb in the unicellular marine phytoplankton Isochrysis galbana. Results showed that a dose–response effect of nano-Al2O3 was found. Significant enhancement of fluorescence in cell cytoplasm rather than cell membrane occurred in the presence of nano-Al2O3, indicating that nano-Al2O3 can penetrate cells and affect the fluorescence emitted from the chloropigments inside them. The presence of nano-Al2O3 has no impact on the toxic effect of Pb at an NP concentration of 1 mg/L but increased that at NP concentrations of 10 mg/L and 100 mg/L. A synergistic effect was also found for the toxic effect of Pb in the presence of 10 mg/L nano-Al2O3. The presence of 100 mg/L nano-Al2O3 significantly increased the bio-uptake of Pb in the range of 0.25 mg/L to 2.0 mg/L Pb, and the maximum accumulated Pb in algae can reach up to 18.22 ng/105 cells with 100 mg/L nano-Al2O3 compared with Pb alone at 2.0 mg/L(12.53 ng/105 cells). Inside cells, Pb loaded onto nano-Al2O3 can be more toxic than the same amount of free Pb species. The results of toxicity tests and accumulated Pb in algae imply that, in addition to the total Pb cell content, the bioavailability of Pb inside algae should be taken into consideration in evaluating the joint toxicity effect. Our work enhances understanding of the combined toxicity of NPs and co-existing heavy metals and is of practical significance in the natural environment.