斜生栅藻对全氟辛酸和Zn2+联合胁迫的生理生化响应OACHSSCDCSTPCD

[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.