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Physicochemical Transformations of ZnO NPs in Aquatic Environment

Discover the transformative effects of aging on ZnO nanoparticles in water and their impact on green algae. Explore the relationship between ZnO NP neoformations and toxicity, assessed through morphological changes, interactions, and toxicity levels. Gain insights into physiological alterations in algae cells treated with aged ZnO NPs. Utilize advanced spectroscopic techniques to quantify and identify the evolved compounds. Uncover strategies to reduce toxicity using zinc ion inhibitors.

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Physicochemical Transformations of ZnO NPs in Aquatic Environment

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  1. 4th Global Summit on Toxicology Physicochemical transformations of ZnO NPs under aging process in aquatic environment and the toxicity to green algae Hong Zhang, Qing Huang* Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, China Email: huangq@ipp.ac.cn August 24-26, 2015 Philadelphia, USA

  2. Background • Nanomaterials and nanotechnology have attracted the attention of the scientific community globally and emerged as a fast developing and fascinating area of research • Nanoparticles (NPs) potentially undergo physicochemical transformation in the environment, which may lead to unexpected environmental and health risks • ZnO NPs are one of the most abundantly used nanomaterials in materials science and nanotechnology-based industries, and the physicochemical properties can be affected by water chemistry and thus the toxicity of ZnO NPs may be changed in the aquatic environment • Microalgae are the primary producers in the aquatic food chain and they are more sensitive to contaminants than fish and invertebrates,a model for evaluating the ecological impact of toxicants and NPs in aquatic environment • Lack of quantitative assessment of the neoformation of ZnO NPs and clear understanding of the relationship between the neoformation and the toxicity of ZnO NPs under aging process on the aquatic organisms such as green algae

  3. Outline • Morphological and qualitative changes of ZnO NPs under aging process in aquatic environment • Interactions of ZnO NPs and algal cell surface • Effects of aging process on the toxicity of ZnO NPs to green algae cells • Identification and quantification of the neoformations transformed from ZnO NPs under aging process • Contribution of the neoformations in aged ZnO NPs to the toxicity on green algae C. vulgaris • Identification of the difference in toxicity between fresh and aged ZnO NPs by infrared spectroscopy

  4. (a) (b) (d) (c) Morphological and qualitative changes of ZnO NPs ZnO NPs-fresh ZnO NPs-aged SEM TEM SEM: spherical and short-rod, no obvious changes TEM: sheet-like neoformations

  5. Interactions of ZnO NPs and algal cell surface(C. vulgaris) Control Time： 7days ZnONPs： 50 μg/ml ZnO NPs-fresh ZnO NPs-aged ZnO NPs attached to the surface of the algal cells: distorted morphological features

  6. Toxicity of aged ZnO NPs to green algae (C. vulgaris) chlorophyll a Specific growth rate ZnO suppressed the growth of algea The growth rate and chlorophyll a contents in group ZnO-120 days and ZnO-210 days are higher than that in group ZnO-30 days.

  7. Changes in physiological status of algal cells The integrality of algal cell membrane Photosynthetic activity Intracellular ROS content • Comparisons in membrane damage, • photosynthetic activity, intracellar ROS • content in five groups: • Control without ZnO NPs • ZnO NPs fresh • ZnO-30 NPs days • ZnO-120 NPs days • ZnO-210 NPs days

  8. Identification of the neoformations transformed from ZnO NPs under aging process FTIR XRD Raman FTIR, Raman and XRD spectroscopic analysis confirmed that the main components were Zn (OH) 2, Hydrozincite and ZnO NPs during aging process

  9. Quantification of the neoformations transformed from ZnO NPs (two compounds)

  10. Quantification of the neoformations transformed from ZnO NPs (three compounds) P145/P437 P830/P437

  11. Molar ratios of neoformations and zinc ions concentration in ZnO NPs during aging process Molar ratios of neoformations in ZnO NPs during aging process Zinc ions concentration in the different aged ZnO NPs

  12. Zinc ion inhibitor (TPEN) influence on the effect of ZnO NPs toxicity on green algae C. vulgaris TPEN：10 μM ZnO NPs：10 μg/ml TPEN can significantly reduce the toxicity of the fresh or aged ZnO NPs

  13. Distinguishing the species and components in algal cells by FTIR

  14. Changes of components in algal cells treated by fresh or aged ZnO NPs detected by FTIR lipid band 3000–2800 cm−1 carbohydrate band 1200–950 cm−1 protein amide I (1724–1585 cm−1) amide II (1585–1490 cm−1) Bioresource Technology, 2014, 347–354 carbohydrate Protein Lipid

  15. Discrimination of toxicity of the fresh or aged ZnO NPs by FITR combined with Principal component analysis(PCA)

  16. Conclusions • ZnO NPs undergoing aging process in water were transformed into basic zinc carbonate and zinc hydroxide and other substances, and these neoformations can be quantitatively determined by Raman spectroscopy. • The toxicity of ZnO NPs aged for 30 days is larger than that for fresh ZnO NPs, but smaller than that of ZnO NPs aged for longer time (e.g. 120, 210 days). • The toxicity of aged ZnO NPs on Chlorella vulgaris weredecreased during the aging process due to less toxic zinc hydroxide and basic zinc carbonate transformed from ZnO NPs in aquatic environment . • Physiological status changes of Chlorella vulgaris treated by fresh or aged ZnO NPs can be discriminated by infrared spectroscopy combined with chemometric methods.

  17. Thanks for your attention! Hefei Institutes of Physical Science, Chinese Academy of Sciences (CAS)

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