Toxic Effects Of Nano Fe₂O₃ And Tetracycline On Selenastrum Capricornutum

In this study,nano-Fe2O3 and tetracycline were used as experimental materials,and Selenastrum capricornutum was used as test organisms.Laboratory experiments were performed under different concentrations of nano-Fe2O3 and tetracycline.In order to study single and combined toxic effects of nano-Fe2O3 and tetracycline,experiments measured the Selenastrum capricornutum's growing situation,chlorophyll a content,reactive oxygen species?ROS?level,superoxide dismutase?SOD?activity,malondialdehyde?MDA?content and glutathione?GSH?content.Toxicity unit method?TU?was used to judge the type of complex effect under stress of nano-Fe2O3 and tetracycline on Selenastrum capricornutum.The experimental results are as follows:1)Nano-Fe₂O₃ can strongly inhibit the growth of Selenastrum capricornutum.The median effective concentration(EC₅₀)is 16.581mg·L^-1 during 96h exposure period.Nano-Fe2O3 treatment inhibited the content of chlorophyll a in cells of Selenastrum capricornutum.Nano-Fe2O3 induces ROS levels in Selenastrum capricornutum cells;higher concentrations(?8mg·L^-1)of nano-Fe₂O₃ induce SOD activity and MDA content in Selenastrum capricornutum cells;medium-high concentrations(?4mg·L^-1)of nano-Fe₂O₃induce GSH content in Selenastrum capricornutum cells.2)Tetracycline can strongly inhibit the growth of Selenastrum capricornutum.The highest concentration of tetracycline exerted the most significant inhibitions on the growth of Selenastrum capricornutum cells.The EC₅₀ is 3.142mg·L^-1 during 96h exposure period.Tetracycline inhibited the content of chlorophyll a in cells of Selenastrum capricornutum.The higher concentrations(?1.6mg·L^-1)of tetracycline induced the ROS level in Selenastrum capricornutum cells;the highest concentration(3.2mg·L^-1)of tetracycline induced the SOD activity of Selenastrum capricornutum cells for 24h,and the GSH content in Selenastrum capricornutum cells were also induced.Tetracycline induces MDA content in Selenastrum capricornutum cells.3)The type of complex effect of nano-Fe2O3 and tetracycline's stress on Scenedesmus obliquus is antagonistic.In the joint toxicity experiments,the inhibition rate of Selenastrum capricornutum in the No.5 experimental group,the inhibition rate reached21.65%at 96h.It was lower than that of the respectively use of nano-Fe2O3 and tetracycline;the content of chlorophyll a decreased by 20%compared with that of the control group,and the result was lower than that of the use of tetracycline alone,but higher than that of nano-Fe2O3 alone.During the experiment,the combined stress induced the ROS level and MDA content in Selenastrum capricornutum cells.The SOD activity of Selenastrum capricornutum cells was inhibited under the combined stress of higher concentrations of nano-Fe2O3 and tetracycline.The GSH content of Selenastrum capricornutum cells were induced under high concentration of nano-Fe2O3 and tetracycline stress at 48h.