4.7 Article

A Mathematical Model for the Release, Transport, and Retention of Per- and Polyfluoroalkyl Substances (PFAS) in the Vadose Zone

Journal

WATER RESOURCES RESEARCH
Volume 56, Issue 2, Pages -

Publisher

AMER GEOPHYSICAL UNION
DOI: 10.1029/2019WR026667

Keywords

PFAS; PFOS; air-water interface; variably saturated flow; retardation; transport

Funding

  1. Water, Environmental, and Energy Solutions (WEES) Initiative at the University of Arizona
  2. NIEHS Superfund Research Program [P42 ES 4940]

Ask authors/readers for more resources

Per- and polyfluoroalkyl substances (PFAS) are emerging contaminants of critical concern. As surfactants, PFAS tend to accumulate at air-water interfaces and may stay in the vadose zone for long times before contaminating groundwater. Yet not well understood, the extent of retention in the vadose zone has critical implications for risk management and remediation strategies. We present the first mathematical model that accounts for surfactant-induced flow and solid-phase and air-water interfacial adsorption. We apply the model to simulate PFOS (a PFAS compound of primary concern) transport in the vadose zone at a model fire-training area site impacted by aqueous film-forming foam (AFFF). Air-water interfacial adsorption is shown to have a significant impact-amplified by the low water content due to gravity drainage-total retardation factors range from 233 to 1,355 for the sand and 146 to 792 for the soil used in the study. The simulations illustrate it can take several decades or longer for PFOS to reach groundwater. Counterintuitively, the lower water content in the sand-due to stronger drainage and weaker capillary retention-leads to retardation factors greater than for the soil. Also, most PFOS is adsorbed at air-water interfaces with only 1-2% in the aqueous phase. The implications include (1) fine-texture materials could have lower retardation factors than sand due to higher retained water content, (2) soil PFAS concentrations are likely to be orders of magnitude higher than those in groundwater at source zones. Both implications are consistent with recent field observations at hundreds of AFFF-impacted sites.

Authors

I am an author on this paper
Click your name to claim this paper and add it to your profile.

Reviews

Primary Rating

4.7
Not enough ratings

Secondary Ratings

Novelty
-
Significance
-
Scientific rigor
-
Rate this paper

Recommended

No Data Available
No Data Available