Evaluating air-water and NAPL-water interfacial adsorption and retention of Perfluorocarboxylic acids within the Vadose zone

Silva, Jeff A.K.; Martin, William A.; Johnson, Jesse W.; McCray, J. E.

doi:10.1016/j.jconhyd.2019.03.004

Cited by 77 publications

(96 citation statements)

References 40 publications

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“…The influence of processes, other than solid-phase adsorption, on PFAS fate and transport has been identified in other PFAS characterization studies (Xiao et al 2015;Weber et al 2017;Brusseau et al 2020). In unsaturated systems, many PFAS will strongly adsorb to the air-water interfaces in vadose zone soils (Brusseau 2018;Lyu et al 2018;Silva et al 2019) and to NAPL-water interfaces for conventional NAPLs in the vadose and saturated zones (Nelson and Brusseau 1996;Saripalli et al 1998;Cain et al 2000;Brusseau et al 2003;Silva et al 2019). Accumulation at air-water interfaces can be particularly important for PFAS MNA as it can result in long-term retention of a large fraction of the PFAS mass, especially in fine-grained soils (Brusseau et al 2019;Costanza et al 2019).…”

Section: Partitioning/retentionmentioning

confidence: 97%

“…The degree of retention by these mechanisms is a function of the partition coefficient of a particular PFAS compound and the interfacial area between the two phases of interest. Reasonable estimates of air: water and NAPL:water partitioning can be made for many PFAS (Brusseau 2018;Schaefer et al 2019;Silva et al 2019) and the NAPL literature provides several methods to measure and predict air:water as well as NAPL:water interfacial areas in the subsurface (Karkare and Fort 1996;Saripalli et al 1998;Cho and Annable 2005;Brusseau et al 2006;Chen and Kibbey 2006;Dobson et al 2006).…”

Section: Partitioning/retentionmentioning

confidence: 99%

“…That is, increased salinity enhances the retention of certain organic compounds on the solid matrix. Similarly, the ionic strength of groundwater has been observed to impact PFAS sorption (Brusseau et al 2019;Silva et al 2019;Li et al 2020;Lyu and Brusseau 2020). Several researchers have reported the salting out of PFAS in estuarine systems as freshwater PFAS plumes mix with salt water, resulting in increased plume salinity and increased sorption of PFAS to solids, with a commensurate decrease in the aqueous phase concentrations.…”

Section: Pfas Salting Outmentioning

confidence: 99%

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Monitored Natural Attenuation to Manage PFAS Impacts to Groundwater: Scientific Basis

Newell¹,

Adamson²,

Kulkarni³

et al. 2021

Groundwater Monitoring Rem

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This column reviews the general features of PHT3D Version 2, a reactive multicomponent transport model that couples the geochemical modeling software PHREEQC-2 (Parkhurst and Appelo 1999) with three-dimensional groundwater flow and transport simulators MODFLOW-2000 and MT3DMS (Zheng and Wang 1999). The original version of PHT3D was developed by Henning Prommer and Version 2 by Henning Prommer and Vincent Post (Prommer and Post 2010). More detailed information about PHT3D is available at the website http://www.pht3d.org.The review was conducted separately by two reviewers. This column is presented in two parts.

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Section: Partitioning/retentionmentioning

confidence: 97%

Section: Partitioning/retentionmentioning

confidence: 99%

Section: Pfas Salting Outmentioning

confidence: 99%

See 1 more Smart Citation

Monitored Natural Attenuation to Manage PFAS Impacts to Groundwater: Scientific Basis

Newell¹,

Adamson²,

Kulkarni³

et al. 2021

Groundwater Monitoring Rem

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“…The impact of fluid‐fluid interfacial adsorption on PFAS retention and transport in soil was examined initially by Brusseau (), who employed surface tension data for PFAS including two of primary concern—perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS)—and measured air‐water interfacial areas along with a comprehensive retention model to conduct a theoretical assessment. Additional surface‐tension‐based theoretical analyses of PFAS retention have since been reported (Brusseau, , ; Brusseau & Van Glubt, ; Costanza et al, ; Silva et al, ). Miscible‐displacement laboratory experiments demonstrating that adsorption of PFAS at air‐water and NAPL‐water interfaces can be an important retention process in soil and sand materials have also been reported (Brusseau et al, ; Lyu et al, ).…”

Section: Introductionmentioning

confidence: 99%

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

Guo

Zeng

Brusseau

2020

Water Resources Research

136

119

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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.

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“…Using surface tension data of two primary PFAS and measured air-water interfacial (AWI) areas in soil materials, Brusseau (2018) examined the impact of PFAS adsorption at air-water interfaces as a potential retention process in soils. More surface-tension-based theoretical analyses covering a wider range of PFAS and solution chemistry conditions have since been reported (Brusseau et al, 2019a(Brusseau et al, , 2019bBrusseau & Van Glubt, 2019;Costanza et al, 2019;Silva et al, 2019;Schaefer et al, 2019;Costanza et al, 2020). The impact of AWI adsorption has also been investigated by miscible-displacement experiments using packed columns of different soil media and water saturation conditions (Brusseau, et al, 2019a;Lyu & Brusseau, 2020;Lyu et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

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

Zeng¹,

Guo²

2021

Preprint

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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.

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Evaluating air-water and NAPL-water interfacial adsorption and retention of Perfluorocarboxylic acids within the Vadose zone

Cited by 77 publications

References 40 publications

Monitored Natural Attenuation to Manage PFAS Impacts to Groundwater: Scientific Basis

Monitored Natural Attenuation to Manage PFAS Impacts to Groundwater: Scientific Basis

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

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

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