Ecotoxicity of non-aged and aged CeO2 nanomaterials towards freshwater microalgae.

The ecotoxicity of artificially alterated cerium dioxide nanoparticles (nano-CeO2) suspensions was determined using the freshwater microalgae growth inhibition test. The agglomeration or aggregation state of the alterated suspensions was followed because it represents one of the obvious modifications when nanoparticles reached the environment. In addition, its influence on the ecotoxicity of nanoparticles is currently not well-addressed. Our results showed that the suspensions were stable within the first 24 h and then agglomerate up to 10 μm after 3 and 30 days. The inhibitory effect on the growth of exposed algae was however similar whatever the tested suspension. This supports the fact that the agglomeration state of nano-CeO2, in our conditions, has few influences on the ecotoxicity toward these organisms. The EC50 values were 5.6; 4.1 and 6.2 mg L(-1), after exposure to non aged, 3 and 30 days aged suspensions respectively. The interaction between algal cells and nano-CeO2 was also addressed.