Date of Award

1-1-2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Environmental Engineering

First Advisor

Feng Xiao

Abstract

The extraordinary number of unknown per- and polyfluoroalkyl substances (PFAS) necessitates identifying the substances as a first step to understanding them and their risks. From an environmental engineering perspective (preventing, controlling, and remediating), PFAS remediation and control measures are only as effective as the tools used to detect them. Focusing on aqueous film-forming foam (AFFF), several researchers have elucidated the structures of unknown PFAS, with each study accomplishing PFAS identification differently. A range of software and practices were used to improve mass spectrometry (MS) results or elucidate chemical structures. Different identification approaches were compared in the current research, including suspected identification and a Kendrick mass defect (KMD) method. Focusing on the interpretation of MS results methods, several commonalities appeared, including suspect identification (exact/accurate mass), fragmentation identification, and KMD. These three identification methods were employed in this study for analyzing several legacy AFFF samples manufactured by the 3M Company from 1979 to 2002 and soil samples collected from past AFFF release sites. The results obtained indicated how AFFF composition has changed over time. Other PFAS were found, i.e., beyond those targeted by the United States Environmental Protection Agency (USEPA) and the new 40 classes of PFAS identified by Brazen-Hanson et al. (2017). The suspect identification method identified most, if not all, PFAS in the 40 classes detected by Brazen-Hanson et al. (2017). However, the KMD approach detected a much smaller number of PFAS compounds in the AFFF samples. Continuous MS scanning enables identifying new PFAS from other PFAS elucidation studies, i.e., non-targeted analysis (NTA). The NTA approach of complete scan data could facilitate future standards without having to resample and thereby having to expand on past efforts. The current study shows the strengths and limitations of three PFAS identification methods of soils and legacy AFFF products at known AFFF release sites. Overall, this study shows that multiple methods are required to identify PFAS because of the inherent disadvantages associated with each particular method

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