This presentation will cover the investigation and assessment of Per- and Polyfluoroalkyl Substances (PFAS). It will focus on the laboratory techniques that available to determine PFAS in the environment.

PFAS comprise a broad group of over seven million persistent synthetic chemicals (Schymanski, 2023). Our understanding of the presence, toxicity and potential effects of this group of contaminants continues to advance. Although PFAS have been used for decades, only recently, due to advances in laboratory techniques, has it been possible to reliably quantify the presence and potential impact of a wider class of PFAS. Key uncertainties, however, still remain. This talk will address these uncertainties.

6:2 FTAB
While PFAS sources are varied, the release of AFFF is a common source of PFAS contamination at airports, military bases, major oil and gas facilities and many other affected sites in Europe. The combination of complex AFFF compositions and numerous types of foams used throughout decades of fire training, and emergency response scenarios has resulted in highly diverse mixtures of PFAS being present in the subsurface. The presence of cationic and zwitterionic precursors in many Class B firefighting foams (used for the extinguishment of flammable liquid fires) can act as an on-going source of the more frequently regulated and measured PFAS.

Recent studies have highlighted the importance of analysis of 6:2 fluorotelomer alkylbetaine (6:2 FTAB) (UK Environment Agency 2021, UK Water Industry Research (UKWIR)(2023)) in surface water, groundwater and effluent. In 2022, this substance was also subject to further toxicological review by the US Environmental Protection Agency (USEPA) under their Toxic Substances Control Act (TSCA) (USEPA 2022).

FTOHs
Fluorotelomer alcohols (FTOHs) are one of the major classes PFAS, but conventional liquid chromatography tandem mass spectrometry (LC−MS/MS) methods do not provide reliable data for volatile PFAS. It has therefore been essential to develop both an appropriate sampling and analytical method.

Their presence in surface water, groundwater and drinking water supplies represents a potential risk to human health and the environment. For this reason, two FTOHs (8:2 FTOH and 6:2 FTOH) have been included in the proposed updated Environmental Quality Standard (EQS) (European Commission, 2022).

PFAS in Concrete
Concrete at fire training areas can act as a long-term secondary source of PFAS contamination. These sites were subject to historic and repeated application of aqueous film forming foams (AFFF) over many years or decades. PFAS can diffuse and partition into concrete over time and self-assemble on surfaces. AFFF impacted concrete slabs that store and retain PFAS, represent an on-going risk to potential receptors such as groundwater and surface waters during release events.

Analysis of concrete itself has been undertaken to determine the extent of PFAS penetration. This is from targeted near surfaces of the concrete where the dust is submitted for analysis. The remaining concrete is re-cored, cut and crushed at pre-determined depths. Leaching tests can also be carried to assess the risk to groundwater.

Conclusion
The implementation of new sampling and analytical methods is required to assess different classes of PFAS such as zwitterions and the volatile FTOHs which are PFAA-precursors. These PFAS exhibit very different fate and transport characteristics. Consideration of concrete as a potential secondary source of contamination is also required when developing a reliable and robust CSM for sites with fire training areas or those that have experienced AFFF discharge to ground.

Using these new techniques improves the quality of site investigation, provides confidence in the subsequent risk assessment, and will better inform the potential remediation options.