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Title of Talk:
Short-term Chronic Toxicity of Photocatalytic Nanoparticles to Bacteria, Algae, and Zooplankton

Abstract of Talk:
The unique physical and chemical properties of photocatalysts can stress the aquatic environment. This proposed research will evaluate the short-term chronic toxicity of photocatalytic nanoparticles to bacteria, algae and daphnia. Properties such as particle size, location and level of the band gap energy, surface charge, and chemical composition are keys to the ecotoxicity of photocatalytic nanoparticles. Generally as the particle size decreases, the toxicity of the photocatalysts increases and the band gap energy may shift toward the visible end of the light spectrum, making smaller photocatalysts more sensitive to visible light. Photocatalysts can exhibit oxidation or reduction reactions or both. Photooxidation and photoreduction can have significant impacts on microorganisms. Nanoparticles in an the aqueous environment can also acquire surface charges, which can affect specific chemical interactions between the nanoparticles and the microorganisms of interest.

This proposed research project is to assess the short-term chronic toxicity of photocatalytic nanoparticles to selected aquatic microorganisms. Nanoparticles possessing photocatalytic or semiconducting properties ncluding infrared (IR) sensitive CdSe and MoS2, visible light sensitive GaP, CdS, and ultraviolet (uv) light sensitive TiO2, ZnO and SnO2 will be studied. Testing organisms will cover three trophic levels: bacteria, algae, and primary consumers(e.g., zooplankton). E coli and a mixed commercial bacterial culture, Selenastrum capricornutum (green algae) and Cericodaphnia bubia (daphnia) will be selected as the testing organisms. The specific objectives are (1) to determine the acute toxicity of photocatalytic nanoparticles to a mixed bacterial culture, (2) to determine the short-term chronic toxicity of photocatalytic nanoparticles to a pure bacterial culture of E. coli, (3) to determine the short-term chronic toxicity of photocatalytic nanoparticles to Ceriodaphnia dubia, (4) to determine the short-term chronic toxicity of photocatapytic nanoparticles to Selenastrum capricornutum, (5) to determine the short-term chronic toxicity of copper(II) to Selenastrum capricornutum in the presence of photocatalytic nanoparticles, (6) to determine the short-term chronic toxicity of chlorinated phenols to E. coli and Ceriodaphnia dubia in the presence of photocatalytic nanoparticles, and (7) to determine the short-term toxicity of photocataytic nanoparticles to freshwater algal assemblages.

As a result of the proposed study, it is expected to establish systematic information on the short-term chronic toxicity of photocatalytic nanoparticles to bacteria, algae, and daphnia which covers three successive trophic levels in the ecosystem.

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