Formatted Title:

PFAS Forensic Investigations: Sources, Tools, and Case Studies

Background/Objectives:

Forensic investigations of per- and polyfluoroalkyl substances (PFAS) in the environment are challenged by a combination of the dynamic landscape of PFAS chemicals, their transformation in the environment, and that standard methods only measure a few dozen individual compounds. This presentation will discuss selected results from a SERDP-funded project as well as case studies to describe the state of PFAS forensic investigations. Ultimately, PFAS forensic investigations will rely on some amount of site-specific information. This presentation will help the audience understand what forensic information or technical approaches may be most useful for their investigation.

Approach/Activities:

This presentation will draw upon two sources of information. First, selected results from a SERDP-funded research project will be presented to describe the nature of different source materials or source signatures. This information will include both target PFAS data (measured by standard methods) as well as suspect data (measured by high resolution mass spectrometry [HRMS]) for several different aqueous film-forming foams (AFFFs) and other legacy or modern products used in high volumes that contain PFAS (e.g., Scotchgard^TM, fluoropolymers, etc.).

Second, soil and groundwater data from selected PFAS-contaminated sites, including AFFF and non-AFFF impacted sites, will be discussed. Historical field data as well as forensic-informed sampling results are used to show how PFAS data comport with their known or suspected source, and to highlight the changes in PFAS that can occur due to transformation or subsurface migration.

Results/Lessons Learned:

Comparing the results from the analysis of AFFFs and other source materials as well as the soil and groundwater data from different PFAS-impacted sites, this presentation will highlight markers that can help distinguish AFFF-derived PFAS contamination from other sources. This presentation will also discuss how these types of signatures change as PFAS transform or migrate in the environment. Importantly, PFAS signatures are easier to distinguish in source areas, but become more difficult to distinguish as one moves towards the periphery of a contaminant plume. Discussion will include; 1) using visual patterns of data to distinguish changes due to environmental fate and transport from changes due to the presence of different sources; 2) diagnostic ratios of PFAS; 3) the relative abundance of branched and linear isomers; and 4) the use of chemometrics to uncover PFAS fingerprints and other underlying chemical patterns. By integrating these tools into a site-specific GIS, PFAS forensics can provide a range of interpretations of environmental data. Interpretations can include identifying changes in PFAS due to environmental fate and transport, identifying or ruling out particular sources, and quantitatively allocating contamination amongst different sources.

Trever Schwichtenberg

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PFAS Forensic Investigations: Sources, Tools, and Case Studies