Meizhu Liu
Auburn University
Co-Authors:
Recently, it has been found that Perfluorinated Alkyl Acids (PFAAs) are toxic substances and potentially harmful to humans and the environment. Used in some industrial applications for many years, these compounds are very persistent and do not easily degrade in the environment. Furthermore, they are known to be carcinogenic and endocrine disruptors in higher animals. Further evidence has shown the potential for bioaccumulation or transmission through food webs in aquatic systems. The purpose of this study is to test the toxicity and bioaccumulation of three Perfluorosulfonic acids (PFSAs) substances which is a subclass of PFAAs on algae using a standard test on the green algae Scenedesmus obliquus. Multiple cultures of S. obliquus was exposed to a 0.01 mg/L PFSAs mixture over time, and sampled for presence and location of PFSA compounds in the biomass through washing and extraction with methanol. Results showed that the concentration of PFOS decreased dramatically by time in solution water, especially compared to PFHxS and PFBS in the mixture. In addition, the level of PFBS was seen to remain constant for 13 days of exposure. At the end of this time, the total PFSAs concentration found on the Scenedesmus obliquus was 0.0248 μg/L of PFOS, and 0.00199 μg/L of PFHxS, with no amounts of PFBS on the algae. For future work, the Half Maximal Effect Concentration (EC50) for PFOS, PFBS and PFHxS on S. obliquus will provide information about the fate of the mixture of the compounds in the water system and algal cell system. The concentration of Chlorophyll-a and Pheophytin will gauge the cellular health, and measures of bioaccumulation will inform about the fate of PFOS and PFHxS. Results from these experiments will provide some basic knowledge about the fate and transport of PFSAs in aquatic systems, and inform further studies on ecological transfer in food webs of these and other PFAAs compounds.
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Hi Meizhu, great work on an emerging issue! A couple questions came to my mind, first is there a water quality standard in any countries or states for these chemicals yet? Secondly, how did you choose the time frame for your exposure studies and if you were to carry them out longer, what would you suspect would be the resulting trend? Finally, do you know of any work looking at seasonal trends of these chemicals in the environment?
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Hi! Thank you! Yes, US EPA has a government document that said no more than 70 ng/L of PFASs allowed in the drinking water. About the experiment period, I had tried to do it like 13 days, and it terms out that the PFASs concentration is saturated in the algae cell on the 7th day. For the last question, I didn’t find any papers study about the seasonal trends of the PFASs. Sorry about that.
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Great, thanks for the response!
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