A better understanding of site-specific biotransformation rates and extent of per- and polyfluoroalkyl substance (PFAS) precursors is critical to PFAS site management since many terminal biotransformation products are regulated drinking water and groundwater chemicals. The main objectives of this project are to: (1) develop a molecular biological tool using activity-based labeling techniques that can associate biomarkers such as monooxygenases with the biotransformation rate of PFAS precursors under conditions relevant to aqueous film-forming foam (AFFF)-impacted sites and (2) assess the potential for sequestration/accumulation of terminal PFAS biotransformation products into microorganisms in the form of intracellular storage polymers.

Periodic additions of hydrocarbon fuels, non-fluorinated surfactants, and water in firefighting training areas can stimulate the growth of indigenous microorganisms in PFAS source zones. The project team hypothesizes that the in situ biotransformation rate of PFAS precursors is closely correlated with enzymatic activities stimulated by hydrocarbon fuels and non-fluorinated surfactants. This project will first use a series of batch tests to assess the extent of precursor transformation under aerobic conditions using various pure microbial strains that are known for their capability of hydrocarbon degradation and intracellular polymer synthesis to evaluate correlations between stimulated monooxygenase activities (monitored through activity-based fluorescence-dye labeling) and precursor transformation rates. Then, enrichment cultures originating from AFFF-impacted groundwater and soil will be used to assess the correlation between monooxygenase activities and precursor transformation rates; fluorescence-dye labeled microorganisms in the environmental samples will be separated from non-labeled microorganisms using a fluorescence-activated cell sorting cytometry instrument for further metagenomic evaluation. During both the pure culture and enrichment culture tests, the extent of fluorinated intracellular polymer in biomass will also be determined using the fluorine-19 nuclear magnetic resonance spectroscopy method.

The results of this project will benefit the broader community by: (1) developing a molecular biological tool that can be applied to assess the PFAS precursor transformation activity/potential at AFFF-impacted sites under natural/engineered conditions; and (2) advancing the knowledge on PFAS fate and transport in the source zone through a better understanding of the role of sequestration/accumulation of PFAS precursor transformation products into microbial intracellular storage polymers. The outcomes are expected to provide insights on how to factor in PFAS precursor biotransformation for overall site management and remediation decisions. (Anticipated Project Completion - 2024)