Physiological and Biochemical Responses of Scenedesmus obliquus under the Stress of PFOA and Zn2+
[Objective]The aim of this study is to explore the acute joint toxic effects and mechanisms of perfluorooctanoic acid(PFOA)and heavy metal zinc(Zn2+)on Scenedesmus obliquus,and to provide a theoretical basis for the joint risk assessment of perfluorinated compounds(PFCs)and heavy metals in aquatic ecosystems.[Method]1×106 mL-1S.obliquus was exposed to 0-16 mg/L Zn2+,0-350 mg/L PFOA and 0-1.5 TU for 96 h.The effects of different exposure conditions on the cell density,Chl a,total protein(TP)content,antioxidant system,cell external morphology,ammonia nitrogen conversion,Zn2+ and PFOA removal rate of S.obliquus were analyzed.[Result and Conclusion]The results showed that the 96 h-EC50 of single stress of Zn2+ or PFOA on S.obliquus was 14.17 mg/L and 198.98 mg/L,respectively,and the 96 h-EC50 of combined stress of Zn2+ and PFOA on S.obliquus was 0.97 TU,and the mode of action was partly additive.Both Chl a content and total protein(TP)content decreased significantly under single and combined stress of Zn2+ and PFOA,it indicated that the photosynthesis of algal cells was blocked.Reactive oxygen species(ROS)and malondialdehyde(MDA)content significantly increased,resulting in increased cell membrane permeability and decreased mitochondrial membrane potential.The antioxidant system(T-AOC and SOD)was also disturbed by excessive accumulation of ROS.Scanning electron microscope(SEM)results showed that combined stress could destroy the internal structure.Both TN and NH4+-N in the exposed solution increased with the increase of pollutant exposure concentration,and the difference between the combined stress group and the control group was more obvious.NO3--N content remained at a low level.The removal rate of PFOA by S.obliquus was only 2%,and the removal rate of Zn2+ was higher and gradually decreased with the increase of concentration,the results show that S.obliquus can effectively remove zinc pollution,but the removal effect of perfluorooctanoic acid pollution is not good.
heavy metal zincperfluorooctanoic acidexposureScenedesmus obliquusacute toxic effecttransformation of ammonium nitrogenremove
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