Toxicity of iron-based nanoparticles to green algae: Effects of particle size, crystal phase, oxidation state and environmental aging

• Published in: Environmental pollution (1987) 2016-11, Vol.218, p.505-512
• Main Authors: Lei, Cheng, Zhang, Luqing, Yang, Kun, Zhu, Lizhong, Lin, Daohui
• Format: Article
• Language: English
• Subjects: Algal toxicity; Chlorella - drug effects; Chlorella pyrenoidosa; Environmental aging; Iron - chemistry; Iron - toxicity; Nanomaterial; Nanoparticles - chemistry; Nanoparticles - toxicity; Oxidation; Oxidation-Reduction; Particle Size; Water - chemistry; Water Pollutants, Chemical - toxicity; Zero-valent iron
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2016.07.030

With the increasing environmental application and discharge of iron-based nanoparticles (NPs), a comprehensive understanding of their fate and ecotoxicological effect in the aquatic environment is very urgent. In this study, toxicities of 4 zero-valent iron NPs (nZVI) of different sizes, 2 Fe2O3 NPs of different crystal phases, and 1 type of Fe3O4 NPs to a green alga (Chlorella pyrenoidosa) were investigated, with a focus on the effects of particle size, crystal phase, oxidation state, and environmental aging. Results show that the algal growth inhibition of nZVI increased significantly with decreasing particle size; with similar particle sizes (20–30 nm), the algal growth inhibition decreased with oxidation of the NPs with an order of nZVI > Fe3O4 NPs > Fe2O3 NPs, and α-Fe2O3 NPs presented significantly higher toxicity than γ-Fe2O3 NPs. The NP-induced oxidative stress was the main toxic mechanism, which could explain the difference in algal toxicity of the NPs. The NP-cell heteroagglomeration and physical interactions also contributed to the nanotoxicity, whereas the effect of NP dissolution was negligible. The aging in distilled water and 3 surface water samples for 3 months increased surface oxidation of the iron-based NPs especially nZVI, which decreased the toxicity to algae. These findings will be helpful for the understanding of the fate and toxicity of iron-based NPs in the aquatic environment. [Display omitted] •The algal toxicity of nZVI decreased with increasing particle size.•α-Fe2O3 NPs exhibited higher algal toxicity than γ-Fe2O3 NPs.•The iron-based NPs with higher oxidation presented lower algal toxicity.•The aging in the water samples increased surface oxidation of nZVI.•The aging in the water samples mitigated algal toxicity of iron-based NPs. The algal toxicity of nZVI decreased with increasing particle size, surface oxidation, and environmental aging.