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Single and joint toxicity of zinc oxide and titanium dioxide nanoparticles for freshwater algae
Received:March 16, 2021  
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KeyWord:combination pollution;nanotoxicity;joint toxicity;freshwater algae;modes of toxic action
Author NameAffiliation
WANG Zhuang School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, China 
JIN Shiguang School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, China 
ZHANG Fan School of Environmental Science and Engineering, Nanjing University of Information Science & Technology, Nanjing 210044, China 
WANG Degao College of Environmental Sciences and Engineering, Dalian Maritime University, Dalian 116026, China 
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Abstract:
      In this work the single and joint toxicity of zinc oxide(ZnO) nanoparticles(NPs) and titanium dioxide(TiO2) NPs to two freshwater green algae, namely Scenedesmus obliquus and Chlorella pyrenoidosa, were investigated. Results showed that at different exposure durations, the growth inhibition toxicity of ZnO NPs to freshwater green algae was significantly higher than that of TiO 2 NPs. In addition, the contribution of dissolved Zn2+-ions to the toxicity of ZnO NPs to S. obliquus was higher than that of dissolved Zn2+-ions to the toxicity to C. pyrenoidosa. The joint toxicity of ZnO and TiO2 NPs to S. obliquus was greater than their joint toxicity to C. pyrenoidosa, and the toxicity of ZnO NPs accounted for a higher contribution to the toxicity of the binary mixtures. The joint toxicity of ZnO and TiO 2 NPs to S. obliquus was additive when the mixed concentration was less than 1 mg·L-1 and was antagonistic when the mixed concentration was more than 1 mg·L-1. The joint toxicity of the binary mixtures to C. pyrenoidosa was synergistic at 24 h and antagonistic at 48 h and 72 h. The prediction power of the independent action model for the joint toxicity of the binary mixtures of ZnO and TiO2 NPs was better than that of the concentration addition model. Furthermore, the mechanism of the joint toxicity of ZnO and TiO2 NPs to the two freshwater green algae species was related to the generation of intracellular reactive oxygen species induced by the NPs, which resulted in oxidative stress on the algal cells.