Nano-TiO₂ enhances the toxicity of copper in natural water to Daphnia magna
2011
Fan, Wenhong | Cui, Minming | Liu, Hong | Wang, Chuan | Shi, Zhiwei | Tan, Cheng | Yang, Xiuping
The acute toxicity of engineered nanoparticles (NPs) in aquatic environments at high concentrations has been well-established. This study demonstrates that, at a concentration generally considered to be safe in the environment, nano-TiO₂ remarkably enhanced the toxicity of copper to Daphnia magna by increasing the copper bioaccumulation. Specifically, at 2mgL⁻¹ nano-TiO₂, the (LC₅₀) of Cu²⁺ concentration observed to kill half the population, decreased from 111μgL⁻¹ to 42μgL⁻¹. Correspondingly, the level of metallothionein decreased from 135μgg⁻¹ wet weight to 99μgg⁻¹ wet weight at a Cu²⁺ level of 100μgL⁻¹. The copper was found to be adsorbed onto the nano-TiO₂, and ingested and accumulated in the animals, thereby causing toxic injury. The nano-TiO₂ may compete for free copper ions with sulfhydryl groups, causing the inhibition of the detoxification by metallothioneins.
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