The early 21st century is witnessing a transition of nanotechnology from discovery to commercialization, raising growing concerns about the environmental risks posed by engineered nanomaterials (ENMs). Herein, we present our study on the potential ecological consequences of nanostructured titania (nano-TiO2), one of the most extensively used ENMs, to aquatic systems. In the first part, we focus on how the physicochemical properties of nano-TiO2 and the environmental factors regulate nano-TiO2 toxicity. Despite of inevitable aggregation in natural aqueous matrices, common commercial nano-TiO2 are found to exhibit significant acute phototoxicity towards bacteria and microbial communities. This phototoxicity varies among material phases, exposed bacterial species and is likely mitigated by UV attenuation and natural organic matter in natural aquatic environments. By examining the effects of material morphology on nano-TiO2 toxicity, we demonstrate that nano-TiO2 phototoxicity is not a simple function of photocatalytic reactivity or ROS production. Instead, the geometry, density and alignment of nano-TiO2 aggregates at the bacterial surface play a mediating role. In the second part, we expand our horizon from a TiO2-exclusive system to a multi-ENMs system where nano-TiO2 and nano-ZnO coexist. We show that the level of dissolved zinc ions released from nano-ZnO is synergistically controlled by both nano-ZnO dissolution and Zn adsorption onto nano-TiO2. This suggests that the fate and toxicity potential of soluble ENMs, such as nano-ZnO, are influenced by the presence of other stable ENMs, such as nano-TiO2. A simple kinetic model will be presented to explain our experimental observation and successfully predict the dissolved Zn concentration in solution. Finally, our ongoing study on the photoactivity and phototoxicity of the nano-TiO2/nano-ZnO systems will be also discussed.

Ecological consequences of nano-TiO<sub>2 </sub>released into aquatic systems: From a single-ENM system to multi-ENM systems

248th National Meeting (2014)

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Ecological consequences of nano-TiO2 released into aquatic systems: From a single-ENM system to multi-ENM systems

Ecological consequences of nano-TiO₂released into aquatic systems: From a single-ENM system to multi-ENM systems