Combined ecotoxicity of binary zinc oxide and copper oxide nanoparticles to Scenedesmus obliquus

ABSTRACT

A combined ecotoxicity study was carried out with nano-zinc oxide (nZnO) and nano-copper oxide (nCuO) to freshwater algae Scenedesmus obliquus. Concentration–response analysis indicated that the dissolved metal fraction was not the major source of individual and combined toxicity of the metal-oxide nanoparticles (MONPs). Moreover, the contribution of the nCuO (based on metallic mass) to the combined toxicity was greater than that of the nZnO. The observed combined toxicity can be predicted by the pharmacological concepts of concentration addition (CA) and independent action (IA). Combined toxicity prediction (in terms of median effect concentration) based on both concepts tends to overestimate the overall observed toxicity of the MONP mixtures. CA was more accurate for predicting the combined toxicity than IA. It may be concluded that CA gives a valid estimation of the overall ecotoxicity for mixtures comprising of similar acting MONPs.

KEYWORDS:

• Algal toxicity
• combined effect
• nano-copper oxide
• nano-zinc oxide
• predictive model

Acknowledgments

The authors thank the anonymous reviewers for helping to improve the manuscript.

Funding

This work was supported by the National Natural Science Foundation of China (21407080 and 41601519) and the Natural Science Foundation of Jiangsu Province (BK20140987 and BK20150891).