Aquatic ecotoxicity effect of engineered aminoclay nanoparticles

In the present study the short term aquatic ecotoxicity of water-solubilized aminoclay nanoparticles (ANPs) of ~51±31nm average hydrodynamic diameter was characterized. An ecotoxicological evaluation was carried out utilizing standard test organisms of different phyla and trophic levels namely the eukaryotic microalga Pseudokirchneriella subcapitata, the crustacean Daphnia magna and the bioluminescent marine bacteria Vibrio fisheri. The effective inhibitory concentration (EC₅₀) with 95% confidence limits for the microalga was 1.29mg/L (0.72-1.82) for the average growth rate and 0.26mg/L (0.23-0.31) for the cell yield. The entrapping of algal cells in aggregates of ANP may play a major role in the growth inhibition of algae P. subcapitata. No inhibition was observed for V. fisheri up to 25,000mg/L (no observed effect concentration; NOEC). For D. magna no immobilization was observed in a limit test with 100mg/L in 24h while in 48h a single animal was immobilized (5% inhibition). Correspondingly, the NOEC of ANP in 24h was 100mg/L and the lowest observed effect concentration (LOEC) for 48h was 100mg/L. Therefore it can be considered to use ANP as an algal-inhibition agent at concentrations <100mg/L without affecting or only mildly affecting other organisms including zooplanktons, but further studies on the environmental fate and chronic toxicity of ANP is needed to confirm this.