Non-monotonic concentration-response relationship of TiO₂ nanoparticles in freshwater cladocerans under environmentally relevant UV-A light

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• 作者：Jungkon Kim ; Sangwoo Lee ; Chul-min Kim ; Jihyun Seo ; Yena Park ; Dongwook Kwon ; Song-Hee Lee ; Tae-Hyun Yoon ; Kyungho Choi
• 关键词：Filter apparatus ; Non-monotonicity ; Oxidative stress ; Reactive oxygen species
• 刊名：Ecotoxicology and Environmental Safety
• 出版年：March, 2014
• 年：2014
• 卷：101
• 期：Complete
• 页码：240-247
• 全文大小：3947 K

文摘

The effects of UV-A on the toxicity of TiO₂ nano-particles (NPs) were evaluated using Moina macrocopa and Daphnia magna under environmentally relevant level of UV-A. The waterfleas were exposed to TiO₂ NPs with different sizes of ~298 nm, ~132 nm, or ~72 nm for up to 48 h, with or without UV-A light. Whole body reactive oxygen species and transcription of antioxidant enzyme genes were measured, as well as the survival of the waterflea. In the presence of UV-A, the survival rates of M. macrocopa significantly decreased in concentration dependent way until ~1 mg/L TiO₂ NPs, but the survivals were reversed at greater concentrations. This peculiar non-monotonic trend of concentration-response relationship might be explained by changes of particle size under different light conditions. TiO₂ NPs within a certain size range could be trapped in the filter apparatus and exert toxicity, and the NPs of greater size were subject to either precipitation or ingestion leading to no or little toxicity. Observed TiO₂ toxicity was associated with oxidative stress in the filter apparatus. The results of this study showed that the size change due to UV-A irradiation should be considered in evaluation of ecological risks of TiO₂ NP.