This proof-of-concept project will assess the transformation of perfluoroalkyl acids (PFAA) and their precursors during enzyme-catalyzed oxidative humification reactions (ECOHR) mediated by ligninolytic enzymes and enzyme-producing fungi in water and soil, and survey the ECOHR activities at aqueous film-forming foam (AFFF)-impacted sites. It will identify and elucidate an important process capable of transforming AFFF-relevant PFAS under different environmental conditions, hence improving understanding of the transformation of PFAA and their precursors in the subsurface at AFFF-impacted sites. The overarching objective of this project is to examine the rates, pathways, and governing factors of ECOHR that convert PFAA and their precursors into compounds having molecular features amenable to subsequent aerobic/anaerobic microbial degradation.

Three research tasks are planned: 1) to examine the transformation of PFAAs and their precursors in water via ECOHR in selected enzyme-mediator systems and related fungal culture systems; 2) to investigate the transformation of PFAAs and their precursors in AFFF-impacted soil samples; and 3) to survey AFFF-impacted field-collected soil samples for ECOHR activities by enzyme activity assays and molecular biological tools. The study will investigate the key factors that impact the transformation of representative AFFF components in ECOHR, and identify the products and pathways using rigorous chemical analysis and advanced non-target PFAS identification tools. In addition, the ECOHR activities will be assessed in AFFF-impacted soil samples from Department of Defense sites. These results will allow for the assessment of potential PFAS transformation through ECOHR pathways at AFFF-impacted sites under field conditions.

The study will enhance understanding of the transformation of PFAAs and their precursors through ECOHR at AFFF-impacted sites, thus improving site risk assessment and management decision-making. The results are also expected to provide tools supplementary to monitored natural attenuation programs to enhance PFAS transformation by stimulating ECOHR in situ. It may further lead to development of in situ biological remediation strategies by coupling ECOHR that perturb the perfluoroalkyl structures with subsequent aerobic/anaerobic microbial degradation processes. (Anticipated Project Completion - 2024)