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Chronic toxicity of ZnO nanoparticles, non-nano ZnO and ZnCl₂ to Folsomia candida (Collembola) in relation to bioavailability in soil

Kool, Pauline L., Ortiz, Maria Diez, van Gestel, Cornelis A.M.
Environmental pollution 2011 v.159 no.10 pp. 2713-2719
Folsomia candida, bioavailability, chronic toxicity, ions, nanoparticles, particle size, reproduction, soil, sorption, zinc, zinc oxide
The chronic toxicity of zinc oxide nanoparticles (ZnO-NP) to Folsomia candida was determined in natural soil. To unravel the contribution of particle size and free zinc to NP toxicity, non-nano ZnO and ZnCl₂ were also tested. Zinc concentrations in pore water increased with increasing soil concentrations, with Freundlich sorption constants Kf of 61.7, 106 and 96.4 l/kg (n = 1.50, 1.34 and 0.42) for ZnO-NP, non-nano ZnO and ZnCl₂ respectively. Survival of F. candida was not affected by ZnO-NP and non-nano ZnO at concentrations up to 6400 mg Zn/kg d.w. Reproduction was dose-dependently reduced with 28-d EC50s of 1964, 1591 and 298 mg Zn/kg d.w. for ZnO-NP, non-nano ZnO and ZnCl₂, respectively. The difference in EC50s based on measured pore water concentrations was small (7.94–16.8 mg Zn/l). We conclude that zinc ions released from NP determine the observed toxic effects rather than ZnO particle size.