The use of aqueous film forming foam (AFFF) in fire suppression over many decades has resulted in hundreds of Department of Defense (DoD) fire training areas being impacted with per- and polyfluoroalkyl substances (PFAS), often in the presence of co-occurring chemicals, such as chlorinated solvent and fuel hydrocarbon. Significant attention is now being focused on PFAS with the recent U.S. Environmental Protection Agency (EPA) issue of a drinking water health advisory for two ubiquitous PFAS, perfluorooctanoic acid and perfluorooctanesulfonic acid. Although PFAS-impacted groundwater source areas typically exist as complex chemical mixtures, few studies have examined the mechanisms controlling partitioning or sorption/desorption processes and rates in such mixtures. Furthermore, despite a demonstrated potential for defluorination, the biotransformation of PFAS under conditions representative of natural groundwater systems remains largely unexplored. In addition, there is an absence of PFAS transport and transformation studies in flowing systems, which are necessary for the development and validation of predictive mathematical modeling tools. The primary objectives of this integrated experimental and modeling research are: (1) to improve the understanding of sequestration mechanisms (e.g., sorption, partitioning) and abiotic/biotic (aerobic/anaerobic) transformations that control the transport and persistence of selected PFAS (including representative perfluoroalkyl acids, as well as their precursors and transformation products) in natural aquifer materials; and (2) to develop and validate mathematical models and decision tools that describe the key processes governing transformation, transport, and retention of these selected PFAS in complex AFFF source areas.

This research is organized around four tasks, encompassing (1) transport and partitioning experiments; (2) coupled abiotic and biotic transformation experiments; (3) mathematical modeling and decision tool development; and (4) research translation and project reporting. A matrix of batch, column, and aquifer cell experiments of increasing scale and complexity will be undertaken with the selected PFAS individually and within mixtures, employing reference media and natural aquifer materials collected from PFAS-impacted sites. In selected experiments, sodium dodecyl sulfate and three representative nonaqueous phase liquids (NAPLs) (chlorinated solvents/fuel hydrocarbons) will be employed as representative of AFFF synthetic foaming agents and organic co-occurring chemicals, respectively. Experiments will support the development and calibration/validation of mathematical modeling tools, designed to predict sorption, partitioning, and natural attenuation processes under flowing conditions in natural porous media. These modeling tools will also be used to explore potential PFAS transport and fate under representative field conditions, identified in collaboration with the Air Force Civil Engineering Center, and to develop screening level models and a decision matrix for use by site managers.

In addition to customary project outcomes (project reports, presentations and seminars, scientific publications in peer-reviewed journals, and the education of students trained with the knowledge and skills to address this important problem), this project will make several unique contributions that will aid the DoD in AFFF site management: (i) the elucidation of new scientific knowledge of PFAS retention and transformation behavior that will be integrated into a transport simulator, filling a significant gap by providing the data and insight necessary to make scientifically-informed decisions; (ii) the development of a screening model that will provide a useful tool for DoD decision-makers to make order-of-magnitude estimates of site characteristics, such as chemical longevity and mobility; and (iii) the creation of a decision matrix that will serve as a quick-reference guide, linking site characteristics, and chemical and co-occurring chemical properties with the likelihood of attenuation, so that the DoD can better target their programs to minimize risk. These unique contributions will facilitate the translation of rigorous academic results to field-applicable tools that may be readily used by consultants and field contractors, ultimately ensuring the best allocation of resources in a fiscally constrained environment. (Project Completion - 2023)

Arshadi, M., J. Costanza, L. M. Abriola, and K. D. Pennell. 2020. Comment on “Uptake of Poly- and Perfluoroalkyl Substances at the Air−Water Interface” by Schaefer et al. (2019). Environmental Science & Technology, 54(11):7019-7020. doi.org/10.1021/acs.est.0c01838.   

Costanza, J., M. Arshadi, L. M. Abriola, and K. D. Pennell. 2019. Accumulation of PFOA and PFOS at the Air-Water Interface. Environmental Science and Technology Letters, 6(8):487-491. doi.org/10.1021/acs.estlett.9b00355.

Costanza, J., L. M. Abriola, and K. D. Pennell. 2020.  Aqueous Film-Forming Foams Exhibit Greater Interfacial Activity than PFOA, PFOS, or FOSA. Environmental Science & Technology, 54(21):13590-13597. doi.org/10.1021/acs.est.0c03117.

Liao, S., Z. Saleeba, J. D. Bryant, L. M. Abriola, and K. D. Pennell. 2021. Influence of Aqueous Film Forming Foams on the Solubility and Mobilization of Non-Aqueous Phase Liquid Contaminants in Quartz Sands. Water Research, 195:116975. doi.org/10.1016/j.watres.2021.116975.