Visualization of the Distribution of PFOS and PFHxS in Concrete by DESI MSI
Hoang Nhat Phong Vo, Brett R. Hamilton, Roger Wepf, Trent A. Key, Thi Minh Hong Nguyen, Phong K. Thai, Kevin V. Thomas, Jochen F. Mueller
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/mm 2 (PFHxS) and 3.6 pg/mm 2 (PFOS) with a spatial resolution much greater than that of the previously used core sidewall drilling method.