Perfuorocarboxylate Isomer Aanalysis as a Tool for Source Elucidation

Perfluorocarboxylates (PFCAs) are a class of anthropogenic compounds ubiquitously found in the environment. PFCAs and their precursors are largely manufactured by electrochemical fluorination (ECF) or telomerization. ECF products are mixtures of isomers with linear (70-80%) and branched perfluoroalkyl moiety. Telomerization does not produce isomer mixtures and is predominantly n-perfluorocarbons. This thesis examined the environmental fate and disposition of PFCAs from a relevant and novel perspective of industrial isomer signature. Potential influences of physical and biological properties of isomers on the environmental PFCA isomer pattern were investigated. Branched isomers were more water soluble than n-isomer, however, KOW did not indicate any appreciable differences among isomers. It is possible that the similarity in KOW is due to a balancing effect between elevated activity coefficients in both water and n-octanol. In fish and rats, the major branched isomers of ECF PFOA were eliminated faster than n-isomer. In comparison, PFOS isomer pharmacokinetics were indistinguishable. These findings highlight the need to understand underlying mechanisms mediating PFCA and PFOS isomer pharmacokinetics which may constrain extrapolation from animal-based models to humans. Environmental monitoring revealed PFCA isomers in both abiotic and biotic environment, in temperate regions and remote Arctic. Branched PFOA isomers were consistent with ECF production. In temperate regions, industrially produced ECF PFOA was expected to be a major source of these isomers, given its legacy and volume of production. In the Arctic, PFOA isomers consistent with an ECF signature were attributed to ECF perfluorooctylsulfonamides which likely undergo long range atmospheric transport and atmospheric reactions. The major difference in ECF signature between remote and temperate regions is the presence of ECF PFNA isomers compared to their absence in the Arctic. ECF PFNA is an impurity in ECF PFOA, comprising 0.2%. Input from a linear source, such as fluorotelomer compounds, was also suggestive as both PFOA and PFNA were >95% linear, much more than in technical ECF. Furthermore, longer chain ECF impurities do not account for the PFNA, PFDA, PFUnA, etc. in the Arctic.

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