Theme: 07. Per- and Polyfluorinated Alkyl Substances (PFAS)

Topic Area: 7n. PFAS Source and Forensic Considerations

Formatted Title:

Is This Your PFAS? Forensics and Data Analytics to Identify PFAS Sources Near and Far

Background/Objectives:

The extensive detection of per- and polyfluoroalkyl substances (PFAS) throughout the globe and ongoing rise of stringent state and federal environmental regulations have driven the need for enhanced forensic approaches to source attribution. Recently, the USEPA proposed perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) as CERCLA Hazardous Substances, and the ruling, if accepted, would require facilities to immediately report releases that meet or exceed the reportable quantity. The proposed maximum contaminant levels (MCLs) for PFOA and PFOS have also markedly decreased over the past decade to levels that could potentially surpass the concentrations found in local rainwater. Due to the large number of potential sources of PFAS, it can be important for facilities with potential impacts to differentiate their contribution from ambient/ background levels and/or discrete releases of PFAS from other co-located facilities (e.g., landfills, airports). Analytical techniques are the basis of understanding the presence of PFAS in the environment, and quantifying PFAS concentrations in different environmental matrices are key to understanding source fingerprinting. However, the detection of many PFAS in environmental matrices is only one step in understanding source attribution from areas with mixed industrial and urban environments. Enhanced statistical tools, knowledge of local ambient/background from surrounding sites, site hydrogeology, and geochemistry are all needed to create a holistic understanding of PFAS at the site of interest and differentiate from other potential sources. The objective of this presentation is to communicate real-world case studies, summarize ambient/background investigations within the US, and compare advanced statistical techniques for PFAS forensic analysis.

Approach/Activities:

Ambient/background PFAS characterization results from several public databases and government investigations were assembled to evaluate a statistical distribution of PFAS with environmental media throughout the US. Descriptive statistics (geometric mean, median, etc.) are described for the type of PFAS found in various environmental media (soil, surface water, groundwater). This study also explores the utilization of ambient/background PFAS levels in real-world cases to aid in PFAS forensics investigations and the decision-making process for remediation. Furthermore, it delves into an examination of the disparities among data analytics tools, like principal component analysis and positive matrix factorization, when it comes to PFAS source identification, and examines the advantages and disadvantages associated with each tool.

Results/Lessons Learned:

PFAS forensic investigations are difficult at complex sites and require the use of a weight-of-evidence approach for source attribution. Descriptions of the importance of ambient/background studies for site investigations are emphasized, as local PFAS concentrations in surrounding media are observed higher in mixed urban vs rural areas. Differences in PFAS fingerprints to source attribution are detailed at sites with unique chemistry, and the use of specific statistical tools combined with GIS visualizations are highlighted. Finally, the significance of integrating hydrogeology and geochemistry is explored within the context of PFAS forensic investigations.

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Bethany Parker