New approach sheds light on PFAS in coastal watersheds
NIEHS-funded researchers developed a new tool to identify and characterize previously undetected per- and polyfluoroalkyl substances (PFAS) in watersheds on Cape Cod, Massachusetts. The team identified a distinct signature for PFAS from aqueous film forming foam (AFFF), which is used in firefighting and can contaminate drinking water. However, a large fraction of fluorine could not be explained by AFFF.
PFAS are a large group of compounds that have a carbon-fluorine backbone but vary in other chemical characteristics, such as carbon chain length. In the environment, some PFAS change and transform, making it difficult to identify the parent compound and its source.
The team collected water samples from six coastal watersheds, three of which had known sources of AFFF contamination, and designed an approach to distinguish signatures of PFAS from different sources. First, they analyzed samples for 27 common PFAS compounds using mass spectrometry. Using a method called the total oxidizable precursor (TOP) assay, they developed a new statistical approach to reconstruct the chain length, and therefore source, of the parent compound.
They detected 13 of the 27 common PFAS in more than 70% of the samples. Concentrations of these PFAS were 17 times higher in watersheds with a known AFFF source compared to those without one. The researchers saw distinct clustering in PFAS signatures based on the presence or absence of known AFFF sources. To identify PFAS not captured by TOP analysis, they measured organofluorines, or compounds that contain the carbon-fluorine bond, revealing high concentrations of unexplained organofluorine that did not originate from AFFF.
According to the authors, traditional approaches fail to explain substantial fractions of organofluorine in watersheds, representing a gap in our understanding of PFAS sources that could affect aquatic life and seafood consumers.
Citation: Ruyle BJ, Pickard HM, LeBlanc DR, Tokranov AK, Thackray CP, Hu XC, Vecitis CD, Sunderland EM. 2021. Isolating the AFFF signature in coastal watersheds using oxidizable PFAS precursors and unexplained organofluorine. Environ Sci Technol 55(6):3686-3695.