Toxic Effects Of Nano TiO₂ And Oxytetracycline On Scenedesmus Obliquus

In order to study the toxic effects of nano-titanium dioxide?Nano-TiO₂?and oxytetracycline on Scenedesmus obliquus?S.obliquus?,its growth inhibition,chlorophyll a content,superoxide dismutase?SOD?activity,malondialdehyde?MDA?content and free radical?ROS?level determined the toxic effects under stress of Nano-TiO₂ and oxytetracycline alone and in combination on S.obliquus.Toxicity unit method?TU?was used to judge the type of complex effect caused by Nano-TiO₂ and oxytetracycline on S.obliquus.The results are as follows:1)Both single stress and combined stress of Nano-TiO₂ and oxytetracycline implied toxic effects on S.obliquus.The growth inhibition rate of S.obliquus increased with increasing concentration.The half-effect concentrations(96h-EC₅₀)of Nano-TiO₂ and oxytetracycline were 53.4 mg·L^-1 and 21.3 mg·L^-1,respectively.Chlorophyll a content was positively correlated with algal cell density.2)Both single stress and combined stress of Nano-TiO₂ and oxytetracycline implied effects on the hydrophobicity of S.obliquus.The stress of Nano-TiO₂ alone and the combined stress of Nano-TiO₂ and oxytetracycline on the surface hydrophobicity of S.obliquus was less.The surface hydrophobicity of S.obliquus increased with the increasing concentration of oxytetracycline.3)Through measuring biological indicators related to oxidative damage and combining N-acetyl-L-cysteine?NAC?experiments results,both single and combined stress of Nano-TiO2 and oxytetracycline can increase the degree of S.obliquus's cells internal ROS content and MDA content but inhibit SOD activity.Therefore,both the single and combined stress of Nano-TiO₂ and oxytetracycline caused oxidative damage to S.obliquus.Among them,oxytetracycline had the most severe oxidative damage to S.obliquus.4)According to the toxicity unit method?TU?,when the inhibition rate is 50%,TU=1.24?TU>1.2?.Therefore,the type of complex effect of Nano-TiO₂ and oxytetracycline stressing on S.obliquus is antagonistic.