Over the past decades, manufactured nanomaterials (MNMs) have received increasing attention in material science and nanotechnology-based industries due to their unique physical and chemical properties. However, MNMs may enter environment during their manufacturing, transportation, usage and disposal, leading to accumulation of MNMs in the environment. Previous studies show that the physicochemical transformation of MNMs in environment may have a significant impact on the biological toxicity effect, but there is still a lack of in-depth understanding of the toxicity of transformed MNMs to aquatic organisms. The quantitative analysis of the physicochemical transformations is particularly demanded to distinguish their contributions in the accurate toxicity assessment.

Cooperating with Prof. WU Lijun and Prof. XU An, a study team led by Prof. HUANG Qing in Institute of Technical Biology & Agriculture Engineering, Hefei Institutes of Physical Sciences (CAHIPS) made remarkable progress in characterization and quantification of the physicochemical transformations of zinc oxide nanoparticles (ZnO NPs) during the aging process and also in clarification of the contribution of physicochemical transformations in the toxicity of aged ZnO NPs to Chlorella vulgaris. Their study entitled Spectroscopic probe to contribution of physicochemical transformations in the toxicity of aged ZnO NPs to Chlorella vulgaris: new insight into the variation of toxicity of ZnO NPs under aging process has been published in Nanotoxicology.

In the study, the researchers confirmed that the neoformation in the ZnO-aged sample was composed of hydrozincite and zinc hydroxide during the aging process with the aid of spectroscopic tools.

They found that the amount of hydrozincite increased gradually while the content of zinc hydroxide increased from aged for 30 to 90 days and decreased dramatically from 120 to 210 days, based on the quantitative analysis of the Raman spectroscopy data.

So they concluded that in the early stage, the algae toxicity mainly stems from the release of zinc ions, but with longer aging time, the neoformation of the nanoparticles starts to play a critical role in causing the overall reduced toxicity due to the less toxic hydrozincite and zinc hydroxide in the transformed compounds.

The researchers also found the connection between the toxicity of aged ZnO NPs and the physicochemical transformations, with which they can therefore explicitly explain the variation of toxicity of ZnO NPs depending on the aging time.

As such, this work provides a theoretical and experimental basis about the quantitative analysis of the impact of environmental transformation of MNMs on algae toxicity and reasonable evaluation of ZnO NPs in the real environment.

This work was supported by the National Basic Research Program of China, the Natural Science Foundation of China.

Quantitative analysis of the transformation of ZnO NPs under aging process and its effect on algae toxicity (Image by ZHANG Hong)

Contact:

Professor HUANG Qing, Ph.D

Institute of Technical Biology & Agriculture Engineering

NO.350, Shushanhu Road, Hefei, China

Tel & Fax: +86-551-65595261

Email: huangq@ipp.ac.cn