Impact of water chemistry on the particle-specific toxicity of copper nanoparticles to Daphnia magna.

Toxicity of metallic nanoparticle suspensions (NP) is generally assumed to result from the combined effect of the particles present in suspensions (NP) and their released ions (NP). Evaluation and consideration of how water chemistry affects the particle-specific toxicity of NP are critical for environmental risk assessment of nanoparticles. In this study, it was found that the toxicity of Cu NP to Daphnia magna, in line with the trends in toxicity for Cu NP, decreased with increasing pH and with increasing concentrations of divalent cations and dissolved organic carbon (DOC). Without the addition of DOC, the toxicity of Cu NP to D. magna at the LC50 was driven mainly by Cu NP (accounting for ≥53% of the observed toxicity). However, toxicity of Cu NP in the presence of DOC at a concentration ranging from 5 to 50mg C/L largely resulted from the NP (57%-85%), which could be attributable to the large reduction of the concentration of Cu NP and the enhancement of the stability of Cu NP when DOC was added. Our results indicate that water chemistry needs to be explicitly taken into consideration when evaluating the role of NP and NP in the observed toxicity of NP.