The toxicity of zinc oxide nanoparticles to Lemna minor (L.) is predominantly caused by dissolved Zn

•The main reason for nano-ZnO toxicity to Lemna minor is dissolved Zn from particles.•pH affects the concentration of Zn dissolved from nano-ZnO, results in changes in the toxicity.•Coating of nano-ZnO prevents particle dissolution, causes lower concentration of Zn, leading to a reduce in the toxici...

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Bibliographic Details
Published in:Aquatic toxicology 2016-05, Vol.174, p.46-53
Main Authors: Chen, Xiaolin, O’Halloran, John, Jansen, Marcel A.K.
Format: Article
Language:English
Subjects:
Araceae - drug effects
Coating
Dissolved Zn
Lemna minor
Nano-ZnO
Nanoparticles - chemistry
Nanoparticles - toxicity
Toxicity
Water Pollutants, Chemical - chemistry
Water Pollutants, Chemical - toxicity
Zinc - toxicity
Zinc Oxide - chemistry
Zinc Oxide - toxicity
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Summary:•The main reason for nano-ZnO toxicity to Lemna minor is dissolved Zn from particles.•pH affects the concentration of Zn dissolved from nano-ZnO, results in changes in the toxicity.•Coating of nano-ZnO prevents particle dissolution, causes lower concentration of Zn, leading to a reduce in the toxicity. Nano-ZnO particles have been reported to be toxic to many aquatic organisms, although it is debated whether this is caused by nanoparticles per sé, or rather dissolved Zn. This study investigated the role of dissolved Zn in nano-ZnO toxicity to Lemna minor. The technical approach was based on modulating nano-ZnO dissolution by either modifying the pH of the growth medium and/or surface coating of nano-ZnO, and measuring resulting impacts on L. minor growth and physiology. Results show rapid and total dissolution of nano-ZnO in the medium (pH 4.5). Quantitatively similar toxic effects were found when L. minor was exposed to nano-ZnO or the “dissolved Zn equivalent of dissolved nano-ZnO”. The conclusion that nano-ZnO toxicity is primarily caused by dissolved Zn was further supported by the observation that phytotoxicity was absent on medium with higher pH-values (>7), where dissolution of nano-ZnO almost ceased. Similarly, the reduced toxicity of coated nano-ZnO, which displays a slower Zn dissolution, is also consistent with a major role for dissolved Zn in nano-ZnO toxicity.
ISSN:0166-445X
1879-1514
DOI:10.1016/j.aquatox.2016.02.012