Toxicity and bioconcentration properties of Perfluorosulfonic acids (PFSAs) on the microalgae Scenedesmus obliquus UTEX 393
Type of DegreeMaster's Thesis
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Recently, it has been found that Perfluorinated Alkyl Acids (PFAAs) are 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 suspected 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 bioconcentration of a mixture of three Perfluorosulfonic acids (PFSAs) substances, a subclass of PFAAs, on the green algae Scenedesmus obliquus using a set of standard approaches. Bioconcentration of the PFSA mixture was investigated by exposing a growing culture of S. obliquus to two different starting concentrations of PFSAs. Sampling over time of the aquatic concentrations, and measurements of adsorbed and absorbed concentrations of PFSAs of algae biomass samples from the end of the growth trial, was performed to allow a mass balance on PFSA fractions. The Scenedesmus obliquus Half Maximal Effect Concentration (EC50) for mixed PFOS, PFBS, and PFHxS is 120.35 mg/L. The concentration of Chlorophyll a, Chlorophyll b, and total Chlorophyll gauge the cellular health, and the results show the PFSAs mixture does stress algae cells after seven days of exposure, as seen through declining chlorophyll concentration compared with the control group. In PFSAs mixture bioconcentration test, 0.733 μg/g PFOS, 0.653 μg/g PFHxS, and 1.33 μg/g PFBS were found on the algae cell, and 0.0248 μg/g PFOS, 0.00199 μg/g PFHxS, and 0 μg/g PFBS were detected in the algae cell from 0.01 mg/L PFSAs mixture concentration. At higher exposure concentrations of 0.1 mg/L PFSAs mixture, 13.8 μg/g PFOS and 16.54 μg/g PFHxS were found on the algae cell, and 0.184 μg/g PFOS and 0.127 μg /g PFHxS were detected in the algae. Bioconcentration factors calculated to be 2.79 mL/g, 0 mL/g, and 0.23 mL/g for PFOS, PFBS and PFHxS, respectively, at the 0.01 mg/L PFSAs exposure concentration; and 2.63 mL/g and 1.83 mL/g PFOS and PFHxS, respectively, at the 0.1 mg/L PFSAs exposure concentration. All of the results from this experiment provided some basic knowledge about the PFSAs and inform further studies on ecological transfer in food webs of these and other PFAAs compounds.