TiO₂ nanoparticles in the marine environment: Impact on the toxicity of phenanthrene and Cd^{2 +} to marine zooplankton Artemia salina

The impact of manufactured nanoparticles on the toxicity of co-existing pollutants in aquatic environments has raised increasing concerns. However, the toxicity of polycyclic aromatic hydrocarbons or metal ions in the presence of titanium dioxide nanoparticles (nTiO₂) to marine zooplankton has been rarely reported. In the present study, the impacts of nTiO₂ on the toxicity of phenanthrene (Phe) and cadium (Cd^{2 +}) to Artemia salina, a model marine zooplankton, were investigated. Although nTiO₂ alone exerted a limited toxicity to A. salina within 48 h of exposure, nTiO₂ strongly altered the toxicity of Phe and Cd^{2 +} to A. salina. Compared with the individual toxicities of pollutants to A. salina, the toxicities of Phe and Cd^{2 +} increased by 2.0% and 12.2%, respectively, in the presence of 5 mg/L nTiO₂ but decreased by 24.5% and 57.1%, respectively, in the presence of 400 mg/L nTiO₂. These concentration-dependent impacts of nTiO₂ on the toxicity of Phe or Cd^{2 +} might be attributed to the concurrent functions of several interrelated factors including the adsorption of pollutants on nTiO₂, the nTiO₂-faciliated bioaccumulation of pollutants, the limited gut volume in organisms, and the aggregation and sedimentation behaviors of nTiO₂. These results presented in the study could help understand the effects of manufactured nanomaterials in marine environments.