Organic fluorine content in aqueous film forming foams (AFFFs) and biodegradation of the foam component 6 : 2 fluorotelomermercaptoalkylamido sulfonate (6 : 2 FTSAS)

Abstract

Environmental context Total organofluorine and known fluorosurfactants were quantified in 11 aqueous film forming foams (AFFFs) used to extinguish fires in Ontario, Canada, and one commercial AFFF product. By comparing the concentrations of known fluorosurfactants with the total organofluorine, less than 10% of the fluorosurfactants were identified in half of the samples. Our biodegradation experiment with one of the fluorosurfactants using waste-water treatment plant sludge showed that it was a potential source of perfluoroalkyl carboxylates, which are persistent in the environment. Abstract Eleven aqueous film forming foam (AFFF) samples that were used to extinguish fires in Ontario, Canada, and one commercial product, were analysed using a variety of analytical techniques to obtain structural information and quantities of organofluorine and known perfluoroalkyl and polyfluoroalkyl substances (PFASs). The NMR spectra of the foams distinguished the fluorosurfactants that were synthesised by either electrochemical fluorination or telomerisation. Total organofluorine content was quantified using total organofluorine–combustion ion chromatography (TOF-CIC), which revealed that the samples contained from 475 to 18 000µgFmL–1. The common AFFF component 6 : 2 fluorotelomermercaptoalkylamido sulfonate (FTSAS) was quantified by liquid chromatography tandem mass spectrometry (LC-MS/MS) together with perfluoroalkane sulfonates (PFSAs), perfluoroalkyl carboxylates (PFCAs) and fluorotelomer sulfonates (FTSAs); in five samples, 6 : 2 FTSAS was present in concentrations greater than 1000µgmL–1. By comparing the concentrations of these quantifiable fluorochemicals with the total organofluorine content, it was evident that in half of the AFFF samples, less than 10% of the fluorochemicals were identified; in two of the samples, perfluorooctane sulfonate (PFOS) accounted for ~50% of the total organofluorine content. Our degradation experiment with 6 : 2 FTSAS using waste-water treatment plant sludge showed that 6 : 2 FTSAS was a potential source of FTSAs, fluorotelomer alcohols and PFCAs in the environment.