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

Topic Area: 7m. PFAS Site Characterization

Formatted Title:

PFAS: Challenges in Sampling, Analysis, and Data Assessment of High Sediment Groundwater

Background/Objectives:

Per- and polyfluoroalkyl substances (PFAS) are a set of chemical compounds that are spurring State regulatory agencies into taking action to protect public health and the environment. PFAS are ubiquitous in the environment given their widespread use in a variety of products since the 1940s and their persistence in the environment. In anticipation of regulatory standards for PFAS, groundwater was assessed at both upgradient and downgradient locations at a redevelopment site to assess whether PFAS impacts from an off-site or on-site source might be present. With the EPA proposing drinking water maximum contaminant levels for select PFAS compounds in the parts per trillion (ppt) range, a number of challenges arise during PFAS sampling, analysis, and assessment of data. Given the wide-spread use of PFAS in common products, cross-contamination would be likely if typical sampling methods were implemented; laboratories may also face challenges in achieving reporting limits low enough such that nanogram per liter (ng/L) concentrations can be assessed and it may be difficult to differentiate and identify discrete sources of PFAS.

Approach/Activities:

This paper describes the challenges that were faced during PFAS sampling, laboratory analysis, and data assessment. Sampling methods were modified to use only PFAS-free equipment and materials in an effort to avoid cross-contamination. However, site conditions resulted in high sediment content (up to 30 percent) in grab groundwater samples, which resulted in the laboratory classifying and analyzing the samples as a sludge. This led to analytical results being reported in units associated with a solid (microgram per kilogram) rather than a liquid (ng/L). While all PFAS results were reported as non-detect, a more extensive review of the site history and off-site activities was conducted to further support the conclusion, based on a sludge sample, that the presence of PFAS in groundwater that would require remediation was unlikely.

Results/Lessons Learned:

The lessons learned from this groundwater sampling event are that cross-contamination can be limited by implementing PFAS-free equipment, tubing, containers, and clothing. High sediment content or other contaminants in the matrix are likely to cause interference during laboratory analysis, resulting in reporting limits that are too high or change how the sampling media is reported. Though not always achievable based on available documents, additional review of on- and off-site activities can be used to rule out certain sites or facilities as being a significant sources PFAS.

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Nelson Pi