The overall goal of this project is to assess and validate the use of per- and polyfluoroalkyl substance (PFAS)-related analytical tools with respect to their ability to provide information critical to overall PFAS mass discharge, perfluoroalkyl acid formation potential, and overall organic fluorine mass balance. Such information is critical for designing site investigations and overall site management. Specific objectives include:

• Thorough comparison of total PFAS and organic fluorine levels via PFAS analysis (target+suspect via liquid chromatography with high resolution mass spectrometry [LC-HRMS]), total oxidizable precursor (TOP) assay, and extractable organic fluorine via combustion ion chromatography (EOF).
• Evaluate changes in PFAS and EOF composition ranging from the source area soils to the down-gradient plume.
• Assess the extent to which the analytical tools being evaluated are predictive of potential precursor transformation.
• Determine the site conditions (PFAS concentrations and compositions, geochemical conditions) for which the analytical tools are best suited.
• Provide a preliminary assessment on the repeatability and accuracy of EOF and PFAS (suspect analytes) analyses over a wide range of PFAS and groundwater conditions.

The overall approach is to assess the current PFAS-related analytical tools (PFAS via LC-HRMS, TOP assay, and EOF) by performing in-depth groundwater analyses at up to 12 aqueous film-forming foam (AFFF)-impacted Department of Defense (DoD) sites. Sites will be selected to assess an appropriate range of AFFF sources (different AFFF compositions and/or differences in the extent of weathering), PFAS concentrations, and geochemical conditions that will facilitate validation of these tools at a broad range of the DoD’s AFFF-impacted sites. These analyses will be performed on samples from each of the 12 selected sites at a source area groundwater monitoring location, a source area soil core, and at a downgradient groundwater monitoring location.

Collected data will be used to assess the overall fluorine balances both within and downgradient of the AFFF source area, to determine how the analytical tools can be applied to assess potential and actual precursor transformation in the field, and to attain a preliminary assessment on the repeatability and accuracy of EOF and PFAS (suspect analytes) analyses over a wide range of PFAS and groundwater conditions.

This demonstration is expected to provide the DoD with valuable and novel information regarding the utility of PFAS (target+suspect) analysis, TOP assay, and EOF in AFFF-impacted groundwater and soil. Comparison and quality assurance data across a range of conditions is desperately needed as these methods become more commonly used. By demonstrating the applicability of these tools at up to 12 sites with various PFAS and geochemical conditions, site managers will have a basis to determine if/when such tools are needed. This project also is expected to provide an improved quantitative understanding of PFAS and fluorine molar balances associated with AFFF source areas. Such information is critical for evaluating potential treatment options, and for developing appropriate conceptual site models.

Key data collected during this project include coupled PFAS (target+suspect), TOP, and EOF results under a wide range of conditions for both soil and groundwater. Such a comprehensive accounting exercise for the total fluorine mass budget has not been previously undertaken. Thus, data collected during this project will fill critical data gaps with respect to site characterization, and the utility of these analytical tools. The project team also expects that this information will highlight the limitations of the commercially available analytical tools that are currently available. (Anticipated Project Completion - 2025)

Zhang, C., S. Hao, N. Gonda, Y. Zhi, T.J. Strathmann, C.E. Schaefer, and C.P. Higgins. 2024. Quantification of Long-Chain, Short-Chain, and Ultrashort-Chain Liquid Chromatography-Amenable PFASs in Water: Evaluation of Approaches and Tradeoffs for AFFF-Impacted Water. Journal of Hazardous Materials, 466:133591. doi.org/10.1016/j.jhazmat.2024.133591.