Multidimensional simulation of PFAS transport and leaching in the vadose zone: impact of surfactant-induced flow and soil heterogeneities

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Jicai Zeng, Bo Guo


PFAS are emergent contaminants of which fate and transport in the environment remain poorly understood. As surfactants, adsorption at air-water interfaces and solid surfaces in soils complicates the retention and leaching of PFAS in the vadose zone. Recent modeling studies accounting for the PFAS-specific nonlinear adsorption processes predicted that the majority of long-chain PFAS remain in the shallow vadose zone decades after contamination ceases—in agreement with many field measurements. However, some field investigations show that long-chain PFAS have migrated to tens to a hundred meters below ground surface. These discrepancies may be attributed to model simplifications such as a one-dimensional (1D) representation of the homogeneous vadose zone. Another potentially critical process that has not been fully examined by the 1D models is how surfactant-induced flow (SIF) influences PFAS leaching in multidimensions. We develop a new three-dimensional model for PFAS transport in the subsurface to investigate the multidimensional effects of SIF and soil heterogeneities. Our simulations and analyses conclude that 1) SIF has a minimal impact on the long-term leaching of PFAS in the vadose zone, 2) preferential flow pathways generated by soil heterogeneities lead to early arrival and accelerated leaching of (especially long-chain) PFAS, 3) the acceleration of PFAS leaching in high water-content preferential pathways or perched water above capillary barriers is more prominent than conventional contaminants due to the destruction of air-water interfaces, and 4) soil heterogeneities are among primary sources of uncertainty for predicting PFAS leaching and retention in the vadose zone.



Environmental Health and Protection, Hydrology, Soil Science


heterogeneity, PFAS, surfactant-induced flow, preferential flow, air-water interfacial adsorption, solid-phase adsorption


Published: 2021-06-30 11:48


CC BY Attribution 4.0 International

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Data Availability (Reason not available):
This is a computational study. All of the model input parameters are presented in the main manuscript and the appendices

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Comment #40 Bo Guo @ 2021-08-18 08:57

This preprint has been published in the journal Advances in Water Resources (DOI: