Reduced Accessible Air–Water Interfacial Area Accelerates PFAS Leaching in Heterogeneous Vadose Zones

Zeng, Jicai; Guo, Bo

doi:10.1029/2022gl102655

Cited by 18 publications

(4 citation statements)

References 70 publications

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“…Such behavior may be amplified in the presence of heterogeneous soils and preferential flow phenomena. 63 As noted above, the spatial concentration profiles differ for the three groups of PFAS. The asymmetrical, positively skewed profiles observed for the longest-chain PFAS are likely due to the minimal extents of migration observed for these PFAS.…”

Section: ■ Discussionmentioning

confidence: 84%

“…Such events produce temporarily large increases in water saturation and correspondingly large decreases in air–water interfacial area, which reduces retention associated with air–water interfacial adsorption. , In addition, porewater velocities are increased, which can lead to increased impacts of mass-transfer kinetics and potential mobile air–water interfaces. , One or more of these factors may contribute to inducing accelerated leaching. Such behavior may be amplified in the presence of heterogeneous soils and preferential flow phenomena …”

Section: Discussionmentioning

confidence: 99%

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High-Resolution Depth-Discrete Analysis of PFAS Distribution and Leaching for a Vadose-Zone Source at an AFFF-Impacted Site

Bigler,

Brusseau,

Guo

et al. 2024

Environ. Sci. Technol.

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The long-term leaching of polyfluoroalkyl substances (PFAS) within the vadose zone of an AFFF application site for which the depth to groundwater is approximately 100 m was investigated by characterizing the vertical distribution of PFAS in a high spatial resolution. The great majority (99%) of PFAS mass resides in the upper 3 m of the vadose zone. The depths to which each PFAS migrated, quantified by moment analysis, is an inverse function of molar volume, demonstrating chromatographic separation. The PFAS were operationally categorized into three chain-length groups based on the three general patterns of retention observed. The longest-chain (>∼335 cm3/mol molar volume) PFAS remained within the uppermost section of the core, exhibiting minimal leaching. Conversely, the shortest-chain (<∼220 cm3/mol) PFAS accumulated at the bottom of the interval, which coincides with the onset of a calcic horizon. PFAS with intermediate-chain lengths were distributed along the length of the core, exhibiting differential magnitudes of leaching. The minimal or differential leaching observed for the longest- and intermediate-chain-length PFAS, respectively, demonstrates that retention processes significantly impacted migration. The accumulation of shorter-chain PFAS at the bottom of the core is hypothesized to result from limited deep infiltration and potential-enhanced retention associated with the calcic horizon.

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Section: ■ Discussionmentioning

confidence: 84%

Section: Discussionmentioning

confidence: 99%

High-Resolution Depth-Discrete Analysis of PFAS Distribution and Leaching for a Vadose-Zone Source at an AFFF-Impacted Site

Bigler,

Brusseau,

Guo

et al. 2024

Environ. Sci. Technol.

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“…(2018) found that adsorption at the AWI accounted for approximately 50%–75% of the total retention of perfluorooctanoic acid in sand column experiments. Consequently, quantifying the AWI area is critical for accurately modeling the transport and fate of PFAS in environmental systems (Brusseau & Guo, 2022; Zeng & Guo, 2023). 3.…”

Section: Introductionmentioning

confidence: 99%

Determination of a pedotransfer function for specific air–water interfacial area in sandy soils: A pore network‐informed multigene genetic programming approach

Mirghafari,

Nikooee,

Raoof

et al. 2024

Vadose Zone Journal

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Understanding specific air–water interfacial area (SAWIA) is essential for characterizing and modeling various phenomena in vadose zone hydrology, such as virus and colloid transport, contaminant dissolution, evaporation, and the hydro‐mechanical behavior of unsaturated soils. Traditional measurement methods, including X‐ray imaging and tracer techniques, often encounter challenges, leading to a scarcity of studies that provide a reliable relationship for SAWIA. Currently, no pedotransfer function in the literature links SAWIA with saturation and suction using readily measurable soil properties such as median grain size and porosity. In this study, we initially developed a pore network model capable of predicting SAWIA by calibrating it with corresponding soil‐water retention curves (SWRCs). We then used these models to compile a comprehensive database of SAWIA for six sandy soils, for which experimental SWRCs were available, covering a range of median grain sizes and porosities. Utilizing this database, we established a pedotransfer function through multigene genetic programming. The accuracy of this function was validated against experimental data not previously used in its training and testing. Our parametric study indicated that increases in either porosity or median particle size led to a decrease in the regions exhibiting higher SAWIA in terms of saturation and suction.

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“…20,36 Later on, the model was also used to investigate the heterogeneity effects in two-dimensional (2D) and three-dimensional (3D) conditions, with results displaying preferential flow caused by subsurface heterogeneity-accelerated leaching of PFAS, especially for long-chain PFAS, and this phenomenon is more prominent than conventional contaminants due to the destruction of AWIs. 35,37 While previous studies above have focused on the vadose zone as a critical source of PFAS contamination, surface water is also a main source contributing to PFAS contamination in the groundwater. 9,38 Surface water and groundwater interact within the hyporheic zone along river corridors.…”

Section: ■ Introductionmentioning

confidence: 99%

Sensitivity Analysis and Uncertainty Quantification of PFAS Fate and Transport in Heterogeneous Riparian Sediments

Li,

McGarr,

Moeini

et al. 2024

ACS Earth Space Chem.

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Per-and polyfluoroalkyl substances (PFAS) are surface-active contaminants, which are detected in groundwater globally, presenting serious health concerns. The vadose zone and surface water are recognized as primary sources of PFAS contamination. Previous studies have explored PFAS transport and retention mechanisms in the vadose zone, revealing that adsorption at interfaces and soil/sediment heterogeneity significantly influences PFAS retention. However, our understanding of how surface water− groundwater interactions along river corridors impact PFAS transport remains limited. To analyze PFAS transport during surface water− groundwater interactions, we performed saturated−unsaturated flow and reactive transport simulations in heterogeneous riparian sediments. Incorporating uncertainty quantification and sensitivity analysis, we identified key physical and geochemical sediment properties influencing PFAS transport. Our models considered aqueous-phase transport and adsorption both at the air−water interface (AWI) and the solid-phase surface. We tested different cases of heterogeneous sediments with varying volume proportions of higher permeability sediments, conducting 2000 simulations for each case, followed by global sensitivity and response surface analyses. Results indicate that sediment porosities, which are correlated to permeabilities, are crucial for PFAS transport in riparian sediments during river stage fluctuations. High-permeable sediment (e.g., sandy gravel, sand) is the preferential path for the PFAS transport, and low-permeable sediment (e.g., silt, clay) is where PFAS is retained. Additionally, the results show that adsorption at interfaces (AWI and solid phase) has a small impact on PFAS retention in riparian environments. This study offers insights into factors influencing PFAS transport in riparian sediments, potentially aiding the development of strategies to reduce the risk of PFAS contamination in groundwater from surface water.

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Reduced Accessible Air–Water Interfacial Area Accelerates PFAS Leaching in Heterogeneous Vadose Zones

Cited by 18 publications

References 70 publications

High-Resolution Depth-Discrete Analysis of PFAS Distribution and Leaching for a Vadose-Zone Source at an AFFF-Impacted Site

High-Resolution Depth-Discrete Analysis of PFAS Distribution and Leaching for a Vadose-Zone Source at an AFFF-Impacted Site

Determination of a pedotransfer function for specific air–water interfacial area in sandy soils: A pore network‐informed multigene genetic programming approach

Sensitivity Analysis and Uncertainty Quantification of PFAS Fate and Transport in Heterogeneous Riparian Sediments

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