The objectives of this project were to demonstrate the application of three real-time mobile laboratory methods for per- and polyfluoroalkyl substances (PFAS) including a Department of Defense (DoD) Quality Systems Manual (QSM)-compliant liquid chromatography tandem mass spectroscopy (LC/MS/MS) method, an accelerated LC/MS/MS method for quantitative screening, and methylene blue active substances (MBAS) assay for semi-quantitative screening at source areas. The specific objectives of this project were to demonstrate application the following:

1. Definitive on-site PFAS analyses – solid-phase extraction (SPE) with LC/MS/MS – provided by a DoD Environmental Laboratory Accreditation Program (ELAP)-certified laboratory in the field using DoD QSM 5.3 protocol for 24 PFAS which provides definitive results. While not an analytical method, the term “DoD ELAP Method” is used herein for simplicity.
2. An accelerated LC/MS/MS method focusing on quantitation of a limited number of target PFAS based on site-specific data as indicators of PFAS plume distribution. This method is referred to as the Accelerated Method, which provides quantitative screening results.
3. MBAS assay to evaluate relative amounts of total anionic PFAS and to determine its utility as a pre-LC/MS/MS screening tool to protect the instrumentation.
4. Systematic combination of methods to adaptively and accurately resolve PFAS impacts.

The PFAS mobile lab builds on decades of mobile lab application for chlorinated solvents and petroleum hydrocarbons by providing near real-time analysis of PFAS. The PFAS mobile lab is the only tool capable of providing compound-specific selectivity over a range of concentrations (down to part per trillion levels) to enable source characterization and delineation of PFAS in soil and groundwater. The mobile lab is currently DoD ELAP-certified for soil and groundwater analyses by DoD QSM 5.3. Pace developed the Accelerated LC/MS/MS Method to increase the daily sample testing throughput and used a site-specific list of target PFAS to streamline the analysis, which enables testing of up to 25 soil and groundwater samples per day. The MBAS screening technique was evaluated to determine if the method was sensitive and selective enough to provide utility in prescreening samples for the mobile lab and determine its utility for source area screening. The results were combined using a TRIAD approach for adaptive high-resolution site characterization based on the stratigraphic flux approach developed under Air Force Civil Engineer Center Broad Agency Announcement 927.

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Top: Interior view of PFAS Mobile Lab

Bottom: PFAS mobile lab chemist conducting off-line SPE on water samples

The forgoing examples illustrate the total costs and cost per sample for completing an adaptive high-resolution site characterization (HRSC) project using the three scenarios. Full details of this evaluation are included in the report. A summary of this hypothetical project is offered below.

Scenario #1 - All Fixed-Lab Definitive Analyses. Total estimated cost is $322,000, and the analytical cost per sample is $514. Project duration is 16 days. This is the most expensive of the three approaches and, due to the longer turnaround times of the fixed lab (expected to be 3 days), it would be more difficult to conduct an efficient adaptive work strategy for the entire project.

Scenario # 2 - All Definitive Mobile Lab Analyses. Total estimated cost is $291,000, and the analytical cost per sample is $450. Project duration is 31 days. This is less expensive than Scenario #1 but requires a longer project duration. As mentioned above, the mobile lab in definitive analyses mode is more suited to sampling projects for which the sampling load is fewer than 15 samples per day and the decisions being made at the site are final in nature.

Scenario #3 – Collaborative Approach. Total estimated cost is $234,000, and the analytical cost per sample is $292. Project duration is 16 days. This collaborative dataset approach provides the lowest cost solution for conducting an adaptive HRSC investigation. It provides equal sampling coverage to those of the other two scenarios and with sufficient definitive data to address the compliance requirements for the site. Because this approach can provide data much faster, the collaborate approach facilitates the most adaptive result. Based on a $88k cost difference between Scenarios 1 and 3, this approach could facilitate more than 6 extra days of sampling, or 550 samples total – 38 percent more than Scenario 1 at the same total cost.

In summary, for the given set of project conditions, Scenario #3 – Collaborative Approach, will likely provide the best value for conducting this type of investigation.

It is increasingly recognized that chemical mass flux and discharge may represent the most appropriate measure of plume strength and potential migration risk. Application of the PFAS mobile lab approach supports development of a flux-based conceptual site model in real time and enables implementation of more cost-effective remedies by ranking and prioritizing sources and focusing remedial efforts primarily on long-term mass discharge reduction. The PFAS mobile lab and stratigraphic flux approach are well suited to remedial investigation activities for which accelerated timelines are needed to address potential sources of drinking water impacts as well as developing holistic remedial strategies at DoD sites involving multiple sources of PFAS impacts.

Quinnan, J., M. Rossi, P. Curry, M. Lupo, M. Miller, H. Korb, C. Orth, and K. Hasbrouck. 2021. Application of PFAS‐Mobile Lab to Support Adaptive Characterization and Flux‐Based Conceptual Site Models at AFFF Releases. Remediation, 2021:1-20.