A screening model for quantifying PFAS leaching in the vadose zone and mass discharge to groundwater

Bo Guo, Jicai Zeng, Mark L. Brusseau, Yonggen Zhang

Research output: Contribution to journalArticlepeer-review

Abstract

A growing body of site investigations have demonstrated that vadose zones serve as significant long-term sources of PFAS to groundwater. Quantifying PFAS leaching in the vadose zone and mass discharge to groundwater is therefore critical for characterizing, managing, and mitigating long-term contamination risks. Mathematical models representing the PFAS-specific transport and retention processes, including surfactant-induced flow, and rate-limited, nonlinear adsorption at solid–water and air–water interfaces, have been recently developed. While these advanced models provide fundamental insights into the primary processes controlling the long-term retention of PFAS, they are less suitable for screening-type applications due to significant computational cost and the requirement for detailed input parameters. To address this knowledge gap, we develop a simplified model by assuming steady-state infiltration and linear solid-phase and air–water interfacial adsorption; a two-domain model is used to represent kinetic solid-phase adsorption. We derive novel analytical solutions for the simplified model allowing for arbitrary initial conditions. The newly derived analytical solutions are then validated by application to miscible-displacement experiments under a wide range of conditions and by comparisons to a state-of-the-art comprehensive model under both experimental and field conditions applicable to PFAS-contamination sites. Overall, the simplified analytical model provides an efficient and accurate screening-type tool for quantifying long-term PFAS leaching in the vadose zone.

Original languageEnglish (US)
Article number104102
JournalAdvances in Water Resources
Volume160
DOIs
StatePublished - Feb 2022
Externally publishedYes

Keywords

  • Analytical solution
  • Interfacial adsorption
  • Leaching
  • Per- and polyfluoroalkyl substances (PFAS)
  • Rate-limited adsorption
  • Unsaturated zone

ASJC Scopus subject areas

  • Water Science and Technology

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