A Mechanistic Understanding of PFAS in Source Zones: Characterization and Control
Abstract
Retention of per- and polyfluoroalkyl substances (PFAS) is reported for soils and sediment associated with firefighter training areas (e.g., source zones) where aqueous film forming foams (AFFFs) were routinely applied during firefighter training over decades. Despite the relative water solubility of PFAS, source zones currently retain PFAS though decades have passed since the last AFFF applications. Retention of PFAS when present in complex AFFF mixtures, including successive AFFF applications, is unknown since most transport studies investigate single PFAS or a simple mixtures at low concentrations. Interactions with AFFF and nonaqueous phase liquids (e.g., Jet Fuel) is unknown but they may form thermodynamically stable phases with distinct characteristics. Discharge of chemically complex AFFFs to unsaturated soils involves PFAS interactions with the air-water interface that are not fully understood. The overall objectives of this project are to 1] identify the key PFAS and soil properties that control PFAS interaction with saturated soils when AFFF is applied at near application strength concentrations, 2] characterize the number and type of thermodynamically-stable phases that form when AFFFs are mixed with jet fuel their impact on PFAS transport, and 3] assess PFAS mobility under unsaturated zone conditions in order to identify the key hydraulic parameters and PFAS properties that control PFAS mobility and retention. Under saturated conditions, PFAS introduced as a complex AFFF were retained by clean sand and a natural C2 soil horizon under dynamic flow conditions, indicating significant adsorption, even when organic carbon and surface charge are negligible. PFAS retention was related to PFAS structure and soil properties though a machine learning-based poly-parameter quantitative structure-parameter linear regression model. PFAS retention by clean sand increases over the first three successive AFFF additions, reaching a saturation limit after four
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 15, 2022
- Accession Number
- AD1221403
Entities
People
- Charles E Schaefer
- Christopher P Higgins
- Jennifer Field
- Konstantinos Kostarelos
- Phillip De Blanc
- Stephanie Park
- Tissa H. Illangasekare
Organizations
- CDM Smith
- Colorado School of Mines
- GSI Environmental (United States)
- Jacobs Engineering Group
- Oregon State University
- University of Houston