Suspect Screening of Hydrocarbon Surfactants in AFFFs and AFFF-Contaminated Groundwater by High-Resolution Mass Spectrometry

Aqueous
film-forming foams (AFFFs) are proprietary mixtures containing
hydrocarbon surfactants and per- and polyfluoroalkyl substances (PFASs)
that are used to extinguish hydrocarbon-based fuel fires. There is
limited information on hydrocarbon surfactants in AFFFs and AFFF-contaminated
groundwater even though hydrocarbon surfactants are more abundant
(5–10% w/w) than PFASs (0.9–1.5% w/w) in AFFFs. Eight
commercial AFFFs manufactured between 1988 and 2012 and 10 AFFF-contaminated
groundwaters collected from near source zones of fire-fighter training
areas were analyzed for suspect hydrocarbon surfactants by liquid
chromatography quadrupole time-of-flight mass spectrometry. A suspect
list and a homologous series detection computational tool, enviMass,
were combined to screen for hydrocarbon surfactants. Nine classes
of hydrocarbon surfactants were detected in AFFFs including octylphenol
polyethoxylates, linear alcohol ethoxylates, ethoxylated cocoamines,
alkyl ether sulfates, alkyl amido dipropionates, linear alkyl benzenesulfonates,
alkyl sulfates, and polyethylene glycols. Of those, six were also
found in groundwater along with diethanolamines and alkyl amido betaines,
which were not found in the eight archived AFFFs. This indicates that
although aerobically biodegradable, hydrocarbon surfactants likely
persist in groundwater due to anaerobic aquifer conditions. To the
best of our knowledge, this is the first screening for hydrocarbon
surfactants in AFFFs and in AFFF-contaminated groundwater.