Visualization of the Distribution of PFOS and PFHxS in Concrete by DESI MSI

Abstract

Firefighting training grounds (FTGs) may serve as a potential secondary source for the release of per- and polyfluoroalkyl substances (PFAS) due to historic use of aqueous film-forming foams (AFFFs). Understanding the heterogenicity and vertical distribution of PFAS in AFFF-impacted concrete is important for risk management and potential remediation. This study assessed whether desorption electrospray ionization mass spectrometry imaging (DESI MSI) can be used to analyze PFAS in a concrete core from an AFFF-impacted FTG to provide the vertical distribution of PFAS. PFOS and PFHxS were detected and observed to be distributed in the core mapped by DESI MSI in a manner consistent with data obtained using a conventional method of drilling samples along the depth of a concrete core (i.e., core sidewall drilling) followed by extraction into methanol and analysis by liquid chromatography mass spectrometry. Visualization by DESI MSI provided the mass distribution in greater detail at a resolution of 30–200 μm pixel size. DESI can provide location mapping at PFAS concentrations of >2.7 pg/mm2 (PFHxS) and 3.6 pg/mm2 (PFOS) with a spatial resolution much greater than that of the previously used core sidewall drilling method.