posted on 2015-07-07, 00:00authored byKatie
C. Harding-Marjanovic, Erika F. Houtz, Shan Yi, Jennifer A. Field, David L. Sedlak, Lisa Alvarez-Cohen
The aerobic biotransformation pathways
of 4:2, 6:2, and 8:2 fluorotelomer
thioether amido sulfonate (FtTAoS) were characterized by determining
the fate of the compounds in soil and medium microcosms amended with
an aqueous film-forming foam (AFFF) solution. The biotransformation
of FtTAoS occurred in live microcosms over approximately 40 days and
produced 4:2, 6:2, and 8:2 fluorotelomer sulfonate (FtS), 6:2 fluorotelomer
unsaturated carboxylic acid (FtUCA), 5:3 fluorotelomer carboxylic
acid (FtCA), and C4 to C8 perfluorinated carboxylic
acids (PFCAs). Two biotransformation products corresponding to singly
and doubly oxygenated forms of 6:2 FtTAoS were also identified through
high resolution mass spectrometry (MS) analysis and liquid chromatography
tandem-MS. An oxidative assay was used to indirectly quantify the
total concentration of polyfluorinated compounds and check the mass
balance. The assay produced near complete mass recovery of FtTAoS
after biotransformation, with 10% (mol/mol) of the amended FtTAoS
accounted for in FtS, FtCA, and PFCA products. The transformation
rates of identified products appear to be slow relative to FtTAoS,
indicating that some intermediates may persist in the environment.
This study confirms some of the sources of FtS and PFCAs in groundwater
and soil at AFFF-impacted sites and suggests that fluorinated intermediates
that are not routinely measured during the biotransformation of PFASs
may accumulate.