Bridging Science and Practice: Literature Review and Expert Insights on Per‐ and Polyfluoroalkyl Substances Transport Modeling

Le résumé fourni par la source

ABSTRACT Per‐ and polyfluoroalkyl substances (PFAS) present significant challenges in modeling fate and transport within the subsurface, including both unsaturated and saturated zone, due to their amphiphilic nature, complex partitioning behavior, and partial transformation. Their transport within porous media is highly complex and is governed by dynamic sorption processes at fluid–fluid interfaces and solid surfaces. Furthermore, competitive sorption, nonlinear and rate‐limited sorption, desorption hysteresis, and partial transformation of some polyfluorinated PFAS (aka “precursors”) further complicate accurate transport predictions. These processes are also influenced by site‐specific solution chemistry, minerology and soil type, and hydraulic dynamics. As a result, transport simulation of PFAS is complex and can be more challenging than other contaminants. Traditional equilibrium‐based models, relying on simple empirical partitioning coefficients (K d ), often fail to capture these complexities, leading to uncertainties in risk assessments and remediation strategies. This review synthesizes key advancements and remaining knowledge gaps in PFAS modeling, emphasizing uncertainty in air–water interfacial (AWI) retention, non‐equilibrium transport, and precursor transformation pathways and kinetics. While equilibrium assumptions can provide useful approximations, they often misrepresent transients, such as AWI area (a function of soil moisture content) and fluctuating groundwater levels. Additionally, field data on the effects of competitive interactions, solution chemistry, and rate‐limited sorption and desorption remain scarce, hindering model calibration. To improve transport simulation accuracy, we propose expanding the use of mechanistic adsorption models and empirical data sets to include direct porewater samples in the unsaturated zone. Enhanced parameterization of sorption and transformation processes, coupled with refined multiphase transport models, will provide increased understanding of key site‐specific mechanisms.

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