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Chen D, Hu X, Chen C, Gao Y, Zhou Q, Feng X, Xu X, Lin D, Xu J. Impacts of Perfluoroalkyl Substances on Aqueous and Nonaqueous Phase Liquid Dechlorination by Sulfidized Nanoscale Zerovalent Iron. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:11193-11202. [PMID: 38859757 DOI: 10.1021/acs.est.4c04466] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2024]
Abstract
Per- and poly fluoroalkyl substances (PFASs) are often encountered with nonaqueous phase liquid (NAPL) in the groundwater at fire-fighting and military training sites. However, it is unclear how PFASs affect the dechlorination performance of sulfidized nanoscale zerovalent iron (S-nFe0), which is an emerging promising NAPL remediation agent. Here, S-nFe0 synthesized with controllable S speciation (FeS or FeS2) were characterized to assess their interactions with PFASs and their dechlorination performance for trichloroethylene NAPL (TCE-NAPL). Surface-adsorbed PFASs blocked materials' reactive sites and inhibited aqueous TCE dechlorination. In contrast, PFASs-adsorbed particles with improved hydrophobicity tended to enrich at the NAPL-water interface, and the reactive sites were re-exposed after the PFASs accumulation into the NAPL phase to accelerate dechlorination. This PFASs-induced phenomenon allowed the materials to present a higher reactivity (up to 1.8-fold) with a high electron efficiency (up to 99%) for TCE-NAPL dechlorination. Moreover, nFe0-FeS2 with a higher hydrophobicity was more readily enriched at the NAPL-water interface and more reactive and selective than nFe0-FeS, regardless of coexisting PFASs. These results unveil that a small amount of yet previously overlooked coexisting PFASs can favor selective reductions of TCE-NAPL by S-nFe0, highlighting the importance of materials hydrophobicity and transportation induced by S and PFASs for NAPL remediation.
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Affiliation(s)
- Du Chen
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China
| | - Xiaohong Hu
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China
| | - Chaohuang Chen
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China
| | - Yiman Gao
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China
| | - Qianhai Zhou
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China
| | - Xia Feng
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China
| | - Xinhua Xu
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China
| | - Daohui Lin
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China
- Zhejiang Provincial Key Laboratory of Organic Pollution Process and Control, Zhejiang University, Hangzhou 310058, China
| | - Jiang Xu
- College of Environmental and Resource Sciences, Zhejiang University, Hangzhou 310058, China
- Zhejiang Provincial Key Laboratory of Organic Pollution Process and Control, Zhejiang University, Hangzhou 310058, China
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2
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Rasmusson K, Fagerlund F. Per- and polyfluoroalkyl substances (PFAS) as contaminants in groundwater resources - A comprehensive review of subsurface transport processes. CHEMOSPHERE 2024; 362:142663. [PMID: 38908440 DOI: 10.1016/j.chemosphere.2024.142663] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2024] [Revised: 06/17/2024] [Accepted: 06/18/2024] [Indexed: 06/24/2024]
Abstract
Per- and polyfluorinated alkyl substances (PFAS) are persistent contaminants in the environment. An increased awareness of adverse health effects related to PFAS has further led to stricter regulations for several of these substances in e.g. drinking water in many countries. Groundwater constitutes an important source of raw water for drinking water production. A thorough understanding of PFAS subsurface fate and transport mechanisms leading to contamination of groundwater resources is therefore essential for management of raw water resources. A review of scientific literature on the subject of processes affecting subsurface PFAS fate and transport was carried out. This article compiles the current knowledge of such processes, mainly focusing on perfluoroalkyl acids (PFAA), in soil- and groundwater systems. Further, a compilation of data on transport parameters such as solubility and distribution coefficients, as well as, insight gained and conclusions drawn from the reviewed material are presented. As the use of certain fire-fighting foams has been identified as the major source of groundwater contamination in many countries, research related to this type of pollution source has been given extra focus. Uptake of PFAS in biota is outside the scope of this review. The review showed a large spread in the magnitude of distribution coefficients and solubility for individual PFAS. Also, it is clear that the influence of multiple factors makes site-specific evaluation of distribution coefficients valuable. This article aims at giving the reader a comprehensive overview of the subject, and providing a base for further work.
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Affiliation(s)
- Kristina Rasmusson
- Uppsala Water and Waste AB, Virdings allé 32B, SE-75450, Uppsala, Sweden.
| | - Fritjof Fagerlund
- Uppsala University, Department of Earth Sciences, Villavägen 16, 75236, Uppsala, Sweden
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3
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Bigler MC, Brusseau ML, Guo B, Jones SL, Pritchard JC, Higgins CP, Hatton J. High-Resolution Depth-Discrete Analysis of PFAS Distribution and Leaching for a Vadose-Zone Source at an AFFF-Impacted Site. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024; 58:9863-9874. [PMID: 38780413 DOI: 10.1021/acs.est.4c01615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2024]
Abstract
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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Affiliation(s)
- Matthew C Bigler
- Department of Environmental Science, The University of Arizona Tucson, Arizona 85721, United States
| | - Mark L Brusseau
- Department of Environmental Science, The University of Arizona Tucson, Arizona 85721, United States
- Hydrology and Atmospheric Sciences Department, The University of Arizona, Tucson, Arizona 85721, United States
| | - Bo Guo
- Hydrology and Atmospheric Sciences Department, The University of Arizona, Tucson, Arizona 85721, United States
| | - Sara L Jones
- Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, Colorado 80401, United States
| | - J Conrad Pritchard
- Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, Colorado 80401, United States
| | - Christopher P Higgins
- Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, Colorado 80401, United States
| | - James Hatton
- Jacobs Engineering Group, Greenwood Village, Colorado 80111, United States
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4
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Lehmann A, Flaig M, Dueñas JF, Rillig MC. Surfactant-Mediated Effects on Hydrological and Physical Soil Properties: Data Synthesis. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:19849-19859. [PMID: 37978924 DOI: 10.1021/acs.est.3c05273] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2023]
Abstract
Soils are under the threat of a multitude of anthropogenic factors affecting the complex interplay of various physical and hydrological soil processes and properties. One such factor is the group of surface-active compounds. Surfactants have a broad range of applications and can reduce solid-liquid interfacial forces and increase wettability and dispersion of particles. Surfactant effects are context-dependent, giving rise to a wide range of reported effects on different soil processes and properties. Here, we evaluate the evidence base of surfactant research on 11 hydrological and physical soil variables. Our goal was to identify knowledge gaps and test the robustness of the proposed surfactant effects. We found that the current knowledge base is insufficient to reach strong data-backed conclusions about the effects of surfactants in soils. We identified a unique case of bias in the data as a result of conflated patterns from laboratory and field studies. We could not support the hypothesis that the surfactant charge determines soil effects for any of the tested soil variables. We believe that further experiments on surfactant-mediated effects on soil properties and processes are urgently required, paying attention, in particular, to improving experimental design and data reporting standards.
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Affiliation(s)
- Anika Lehmann
- Institute of Biology, Freie Universität Berlin, 14195 Berlin, Germany
- Berlin-Brandenburg Institute of Advanced Biodiversity Research, 14195 Berlin, Germany
| | - Maximilian Flaig
- Institute of Biology, Freie Universität Berlin, 14195 Berlin, Germany
| | - Juan F Dueñas
- Institute of Biology, Freie Universität Berlin, 14195 Berlin, Germany
- Berlin-Brandenburg Institute of Advanced Biodiversity Research, 14195 Berlin, Germany
| | - Matthias C Rillig
- Institute of Biology, Freie Universität Berlin, 14195 Berlin, Germany
- Berlin-Brandenburg Institute of Advanced Biodiversity Research, 14195 Berlin, Germany
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5
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Brusseau ML, Guo B. Revising the EPA Dilution-Attenuation Soil Screening Model for PFAS. JOURNAL OF HAZARDOUS MATERIALS LETTERS 2023; 4:100077. [PMID: 37990738 PMCID: PMC10662647 DOI: 10.1016/j.hazl.2023.100077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2023]
Abstract
Per and polyfluoroalkyl substances (PFAS) have been shown to be ubiquitous in the environment, and one issue of critical concern is the leaching of PFAS from soil to groundwater. The risk posed by contaminants present in soil is often assessed in terms of the anticipated impact to groundwater through the determination of soil screening levels (SSLs). The U.S. Environmental Protection Agency (EPA) established a soil screening model for determining SSLs. However, the model does not consider the unique retention properties of PFAS and, consequently, the SSLs established with the model may not represent the actual levels that are protective of groundwater quality. The objective of this work is to revise the standard EPA SSL model to reflect the unique properties and associated retention behavior of PFAS. Specifically, the distribution parameter used to convert soil porewater concentrations to soil concentrations is revised to account for adsorption at the air-water interface. Example calculations conducted for PFOS and PFOA illustrate the contrasting SSLs obtained with the revised and standard models. A comparison of distribution parameters calculated for a series of PFAS of different chain length shows that the significance of air-water interfacial adsorption can vary greatly as a function of the specific PFAS. Therefore, the difference between SSLs calculated with the revised versus standard models will vary as a function of the specific PFAS, with greater differences typically observed for longer-chain PFAS. It is anticipated that this revised model will be useful for developing improved SSLs that can be used to enhance site investigations and management for PFAS-impacted sites.
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Affiliation(s)
- Mark L. Brusseau
- Environmental Science Department, The University of Arizona, Tucson, AZ 85721
- Hydrology and Atmospheric Sciences Department, The University of Arizona, Tucson, AZ 85721
| | - Bo Guo
- Hydrology and Atmospheric Sciences Department, The University of Arizona, Tucson, AZ 85721
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6
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Brusseau ML. QSPR-based prediction of air-water interfacial adsorption coefficients for nonionic PFAS with large headgroups. CHEMOSPHERE 2023; 340:139960. [PMID: 37633613 DOI: 10.1016/j.chemosphere.2023.139960] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Revised: 08/15/2023] [Accepted: 08/23/2023] [Indexed: 08/28/2023]
Abstract
Air-water interfacial adsorption has been demonstrated to be an important process affecting the retention and distribution of PFAS in soil, surface waters, and the atmosphere, as well as being central to certain remediation methods. Measured or estimated air-water interfacial adsorption coefficients are needed for quantifying and modeling the interfacial adsorption of PFAS. A single-descriptor QSPR model developed in prior work for predicting air-water interfacial adsorption coefficients of PFAS was demonstrated to successfully represent more than 60 different PFAS, comprising all headgroup types and a wide variety of tail structures. However, the model overpredicted values for nonionic PFAS with very large headgroups. A revised QSPR model was developed in the present study to predict air-water interfacial adsorption coefficients for nonionic PFAS with large headgroups. A two-descriptor QSPR model employing molar volume and headgroup-to-tail molar-volume ratio successfully represented measured data for both nonionic PFAS and nonionic hydrocarbon surfactants. This new model provides a means to produce estimates of air-water interfacial adsorption coefficients for nonionic PFAS for which measured values are typically not available.
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Affiliation(s)
- Mark L Brusseau
- Environmental Science Department, University of Arizona, Tucson, AZ, 85710, USA.
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7
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Brusseau ML. Determining air-water interfacial areas for the retention and transport of PFAS and other interfacially active solutes in unsaturated porous media. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 884:163730. [PMID: 37120024 PMCID: PMC10330266 DOI: 10.1016/j.scitotenv.2023.163730] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2022] [Revised: 04/20/2023] [Accepted: 04/21/2023] [Indexed: 05/03/2023]
Abstract
The objective of this work was to determine the methods that produce the most representative measurements and estimations of air-water interfacial area specifically for the retention and transport of PFAS and other interfacially active solutes in unsaturated porous media. Published data sets of air-water interfacial areas obtained with multiple measurement and prediction methods were compared for paired sets of porous media comprising similar median grain diameters, but one with solid-surface roughness (sand) and one without roughness (glass beads). All interfacial areas produced with the multiple diverse methods were coincident for the glass beads, providing validation of the aqueous interfacial tracer-test methods. The results of this and other benchmarking analyses demonstrated that the differences in interfacial areas measured for sands and soil by different methods are not due to errors or artifacts in the methods but rather the result of method-dependent differential contributions of solid-surface roughness. The contributions of roughness to interfacial areas measured by interfacial tracer-test methods were quantified and shown to be consistent with prior theoretical and experiment-based investigations of air-water interface configurations on rough solid surfaces. Three new methods for estimating air-water interfacial areas were developed, one based on the scaling of thermodynamic-determined values and the other two comprising empirical correlations incorporating grain diameter or NBET solid surface area. All three were developed based on measured aqueous interfacial tracer-test data. The three new and three existing estimation methods was tested using independent data sets of PFAS retention and transport. The results showed that the method based on treating air-water interfaces as smooth surfaces as well as the standard thermodynamic method produced inaccurate air-water interfacial areas that failed to reproduce the multiple measured PFAS retention and transport data sets. In contrast, the new estimation methods produced interfacial areas that accurately represented air-water interfacial adsorption of PFAS and associated retention and transport. The measurement and estimation of air-water interfacial areas for field-scale applications is discussed in light of these results.
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Affiliation(s)
- Mark L Brusseau
- Environmental Science Department, University of Arizona, Tucson, AZ 85721, USA.
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8
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Guo B, Saleem H, Brusseau ML. Predicting Interfacial Tension and Adsorption at Fluid-Fluid Interfaces for Mixtures of PFAS and/or Hydrocarbon Surfactants. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:8044-8052. [PMID: 37204869 DOI: 10.1021/acs.est.2c08601] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Many per- and polyfluoroalkyl substances (PFAS) are surface-active and adsorb at fluid-fluid interfaces. The interfacial adsorption controls PFAS transport in multiple environmental systems, including leaching through soils, accumulation in aerosols, and treatment methods such as foam fractionation. Most PFAS contamination sites comprise mixtures of PFAS as well as hydrocarbon surfactants, which complicates their adsorption behaviors. We present a mathematical model for predicting interfacial tension and adsorption at fluid-fluid interfaces for multicomponent PFAS and hydrocarbon surfactants. The model is derived from simplifying a prior advanced thermodynamic-based model and applies to nonionic and ionic mixtures of the same charge sign with swamping electrolytes. The only required model inputs are the single-component Szyszkowski parameters obtained for the individual components. We validate the model using literature interfacial tension data of air-water and NAPL (non-aqueous phase liquid)-water interfaces covering a wide range of multicomponent PFAS and hydrocarbon surfactants. Application of the model to representative porewater PFAS concentrations in the vadose zone suggests competitive adsorption can significantly reduce PFAS retention (up to 7 times) at some highly contaminated sites. The multicomponent model can be readily incorporated into transport models to simulate the migration of mixtures of PFAS and/or hydrocarbon surfactants in the environment.
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Affiliation(s)
- Bo Guo
- Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, Arizona 85721, United States
| | - Hassan Saleem
- Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, Arizona 85721, United States
| | - Mark L Brusseau
- Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, Arizona 85721, United States
- Department of Environmental Science, University of Arizona, Tucson, Arizona 85719, United States
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9
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Buckley T, Vuong T, Karanam K, Vo PHN, Shukla P, Firouzi M, Rudolph V. Using foam fractionation to estimate PFAS air-water interface adsorption behaviour at ng/L and µg/L concentrations. WATER RESEARCH 2023; 239:120028. [PMID: 37209512 DOI: 10.1016/j.watres.2023.120028] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 04/27/2023] [Accepted: 04/30/2023] [Indexed: 05/22/2023]
Abstract
PFAS are biologically recalcitrant compounds that are persistent in the environment and have subsequently contaminated groundwater, landfill leachate and surface water. Due to their persistence and toxicity, there are environmental concentration limits imposed on some PFAS compounds that extend down to a few nanograms per litre and even proposals for reducing these to picogram per litre levels. Since PFAS concentrates at water-air interfaces as a result of their amphiphilic nature, this characteristic is important for the successful modelling and prediction of transport behaviour of PFAS through various systems. Here we present a procedure for using a foam fractionation method to experimentally determine the PFAS adsorption behaviour at ng/L and µg/L concentrations in the presence of salts. The equilibrium air-water adsorption coefficients for PFHxS and PFOA at different salinities and concentrations are experimentally shown to be constant across the range of PFAS concentrations investigated (approx. 0.1-100 µg/L). The adsorption isotherms may consequently be modelled by Henry or Langmuir style equations at these low concentrations.
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Affiliation(s)
- Thomas Buckley
- School of Chemical Engineering, The University of Queensland, Brisbane, Australia, 4067.
| | - Thinh Vuong
- School of Chemical Engineering, The University of Queensland, Brisbane, Australia, 4067
| | - Kavitha Karanam
- Queensland Alliance of Environmental Health Sciences, The University of Queensland, Brisbane, Australia, 4067
| | - Phong H N Vo
- Queensland Alliance of Environmental Health Sciences, The University of Queensland, Brisbane, Australia, 4067
| | - Pradeep Shukla
- Queensland Alliance of Environmental Health Sciences, The University of Queensland, Brisbane, Australia, 4067
| | - Mahshid Firouzi
- College of Engineering Science and Environment, The University of Newcastle, Callaghan, Australia, 2308
| | - Victor Rudolph
- School of Chemical Engineering, The University of Queensland, Brisbane, Australia, 4067
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10
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Adu O, Ma X, Sharma VK. Bioavailability, phytotoxicity and plant uptake of per-and polyfluoroalkyl substances (PFAS): A review. JOURNAL OF HAZARDOUS MATERIALS 2023; 447:130805. [PMID: 36669401 DOI: 10.1016/j.jhazmat.2023.130805] [Citation(s) in RCA: 28] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2022] [Revised: 01/12/2023] [Accepted: 01/14/2023] [Indexed: 06/17/2023]
Abstract
Per- and polyfluoroalkyl substances (PFAS) are a group of legacy and emerging contaminants containing at least one aliphatic perfluorocarbon moiety. They display rapid and extensive transport in the environment due to their generally high water-solubility and weak adsorption onto soil particles. Because of their widespread presence in the environment and known toxicity, PFAS has become a serious threat to the ecosystem and public health. Plants are an essential component of the ecosystem and their uptake and accumulation of PFAS affect the fate and transport of PFAS in the ecosystem and has strong implications for human health. It is therefore imperative to investigate the interactions of plants with PFAS. This review presents a detailed discussion on the mechanisms of the bioavailability and plant uptake of PFAS, and essential factors affecting these processes. The phytotoxic effects of PFAS at physiological, biochemical, and molecular level were also carefully reviewed. At the end, key research gaps were identified, and future research needs were proposed.
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Affiliation(s)
- Olatunbosun Adu
- Department of Water Management and Hydrological Science, Texas A&M University, College Station, TX 77843, USA; Program for the Environment and Sustainability, Department of Environmental and Occupational Health, School of Public Health, Texas A&M University, 212 Adriance Lab Rd., 1266 TAMU, College Station, TX 77843, USA
| | - Xingmao Ma
- Department of Civil and Environmental Engineering, Texas A&M University, College Station, TX 77843, USA.
| | - Virender K Sharma
- Program for the Environment and Sustainability, Department of Environmental and Occupational Health, School of Public Health, Texas A&M University, 212 Adriance Lab Rd., 1266 TAMU, College Station, TX 77843, USA.
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11
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Stults JF, Choi YJ, Rockwell C, Schaefer CE, Nguyen DD, Knappe DRU, Illangasekare TH, Higgins CP. Predicting Concentration- and Ionic-Strength-Dependent Air-Water Interfacial Partitioning Parameters of PFASs Using Quantitative Structure-Property Relationships (QSPRs). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:5203-5215. [PMID: 36962006 DOI: 10.1021/acs.est.2c07316] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Air-water interfacial retention of poly- and perfluoroalkyl substances (PFASs) is increasingly recognized as an important environmental process. Herein, column transport experiments were used to measure air-water interfacial partitioning values for several perfluoroalkyl ethers and for PFASs derived from aqueous film-forming foam, while batch experiments were used to determine equilibrium Kia data for compounds exhibiting evidence of rate-limited partitioning. Experimental results suggest a Freundlich isotherm best describes PFAS air-water partitioning at environmentally relevant concentrations (101-106 ng/L). A multiparameter regression analysis for Kia prediction was performed for the 15 PFASs for which equilibrium Kia values were determined, assessing 246 possible combinations of 8 physicochemical and system properties. Quantitative structure-property relationships (QSPRs) based on three to four parameters provided predictions of high accuracy without model overparameterization. Two QSPRs (R2 values of 0.92 and 0.83) were developed using an assumed average Freundlich n value of 0.65 and validated across a range of relevant concentrations for perfluorooctane sulfonate (PFOS), perfluorooctanoate (PFOA), and hexafluoropropylene oxide-dimer acid (i.e., GenX). A mass action model was further modified to account for the changing ionic strength on PFAS air-water interfacial sorption. The final result was two distinct QSPRs for estimating PFAS air-water interfacial partitioning across a range of aqueous concentrations and ionic strengths.
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Affiliation(s)
- John F Stults
- Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, Colorado 80401, United States
- CDM Smith, 14432 SE Eastgate Way Suite 100, Bellevue, Washington 98007, United States
| | - Youn Jeong Choi
- Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, Colorado 80401, United States
| | - Cooper Rockwell
- Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, Colorado 80401, United States
| | - Charles E Schaefer
- CDM Smith, 110 Fieldcrest Avenue, #8, 6th Floor, Edison, Edison, New Jersey 08837, United States
| | - Dung D Nguyen
- CDM Smith, 14432 SE Eastgate Way Suite 100, Bellevue, Washington 98007, United States
| | - Detlef R U Knappe
- Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States
| | - Tissa H Illangasekare
- Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, Colorado 80401, United States
| | - Christopher P Higgins
- Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, Colorado 80401, United States
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12
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Buckley T, Karanam K, Han H, Vo HNP, Shukla P, Firouzi M, Rudolph V. Effect of different co-foaming agents on PFAS removal from the environment by foam fractionation. WATER RESEARCH 2023; 230:119532. [PMID: 36584659 DOI: 10.1016/j.watres.2022.119532] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 12/09/2022] [Accepted: 12/23/2022] [Indexed: 06/17/2023]
Abstract
Per- and poly-fluoroalkyl substances (PFAS) are recalcitrant, synthetic chemicals that are ubiquitous in the environment because of their widespread use in a variety of consumer and industrial products. PFAS contamination has become an increasing issue in recent years, which needs to be urgently addressed. Foam fractionation is emerging as a potential remediation option that removes PFAS by adsorption to the surface of rising air bubbles which are removed from the system as a foam. PFAS concentrations in the environment are often not sufficient to allow for formation of a foam by itself and often a co-foaming agent is required to be added to enhance the foamability of the solution. In this study, the effect of different classes of co-foaming agents, anionic, non-ionic, zwitterionic and cationic surfactants on the removal of PFAS with varying fluorocarbon chain length from 3 to 8 in a foam fractionation process have been investigated. Evaluation of the air-water interface partitioning coefficient (k') in addition with surface tension and PFAS removal results support the contention that using a co-foaming agent with the opposite charge to the PFAS in question significantly facilitates the adsorption of PFAS to the air-water interface, enhancing the efficiency of the process. Using the non-ionic surfactant (no headgroup electrostatic interaction with PFAS), as a reference, it was observed, in terms of PFAS separation and rate of PFAS removal, that anionic co-surfactant performed worst, zwitterionic was better, and cationic co-surfactant performed best. All of the PFAS species were able to be removed below the limit of detection (0.05 µg/L) after 45 minutes of foaming time with the cationic surfactant.
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Affiliation(s)
- Thomas Buckley
- School of Chemical Engineering, The University of Queensland, Brisbane 4067, Australia.
| | - Kavitha Karanam
- Queensland Alliance for Environmental Health Sciences, The University of Queensland, Brisbane 4067, Australia
| | - Han Han
- School of Chemical Engineering, The University of Queensland, Brisbane 4067, Australia
| | - Hoang Nhat Phong Vo
- Queensland Alliance for Environmental Health Sciences, The University of Queensland, Brisbane 4067, Australia
| | - Pradeep Shukla
- Queensland Alliance for Environmental Health Sciences, The University of Queensland, Brisbane 4067, Australia
| | - Mahshid Firouzi
- Newcastle Institute for Energy and Resources, The University of Newcastle, Newcastle 2308, Australia
| | - Victor Rudolph
- School of Chemical Engineering, The University of Queensland, Brisbane 4067, Australia
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13
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Brusseau ML, Guo B. PFAS concentrations in soil versus soil porewater: Mass distributions and the impact of adsorption at air-water interfaces. CHEMOSPHERE 2022; 302:134938. [PMID: 35568214 PMCID: PMC9667730 DOI: 10.1016/j.chemosphere.2022.134938] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 04/29/2022] [Accepted: 05/08/2022] [Indexed: 05/14/2023]
Abstract
Determining the risk posed by PFAS leaching from soil to groundwater requires quantification of the magnitude and temporal/spatial variability of PFAS mass discharge from the vadose zone, which is governed in part by the concentrations of PFAS in soil porewater. Porewater concentrations are impacted and mediated by the properties of the PFAS and soil, multiple transport and fate processes, and site conditions. The objective of this research was to delineate the relationship between soil porewater concentrations and soil concentrations, based on a comprehensive model of PFAS mass distribution within a soil sample volume. Measured parameters representing solid-phase sorption and air-water interfacial adsorption are used to illustrate the impact of soil and PFAS properties on the distribution of representative PFAS between soil and soil porewater. Literature data reported for soil and soil porewater concentrations of several PFAS obtained from outdoor lysimeter experiments are used to test the distribution model. Soil-to-porewater concentration ratios predicted with the model compared very well to the measured concentration ratios. The nondimensional distribution coefficient that describes the distribution of PFAS mass amongst all domains within a soil sample was observed to be a function of PFAS molecular size. Numerical simulations conducted for a model fire-training source area were used to illustrate the ranges in magnitude of soil versus porewater concentrations for representative field conditions. The results of the measured and simulated data sets demonstrated the importance of air-water interfacial adsorption for the distribution of the longer-chain PFAS within soil samples. PFAS soil porewater concentrations are anticipated to range from ng/L to mg/L depending upon soil concentrations, which in turn depend upon the nature of the site.
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Affiliation(s)
- M L Brusseau
- Environmental Science Department, The University of Arizona, Tucson, AZ, 85721, United States; Hydrology and Atmospheric Sciences Department, The University of Arizona, Tucson, AZ, 85721, United States.
| | - B Guo
- Hydrology and Atmospheric Sciences Department, The University of Arizona, Tucson, AZ, 85721, United States
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14
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Lyu Y, Wang B, Du X, Guo B, Brusseau ML. Air-water interfacial adsorption of C4-C10 perfluorocarboxylic acids during transport in unsaturated porous media. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 831:154905. [PMID: 35364184 PMCID: PMC9645406 DOI: 10.1016/j.scitotenv.2022.154905] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 03/23/2022] [Accepted: 03/25/2022] [Indexed: 05/11/2023]
Abstract
The impact of chain length on air-water interfacial adsorption of perfluorocarboxylic acids (PFCAs) during transport in unsaturated quartz sand was investigated. Short-chain (C4-C7: PFBA, PFPeA, PFHxA, PFHpA) and long chain (C8-C10: PFOA, PFNA, PFDA) PFCAs were selected as a representative homologous series. Surface tensions were measured to characterize surface activities of the selected PFCAs. Miscible-displacement column experiments were conducted for each of the PFCAs to characterize the magnitudes of air-water interfacial adsorption under transport conditions. The transport of the long-chain PFCAs exhibited greater retardation than the short-chain PFCAs. Air-water interfacial adsorption (AWIA) was the predominant source of retention (≥63%) for the long-chain PFCAs. Conversely, AWIA contributed less to retention than did solid-phase sorption for the short-chain PFCAs, with the former contributions ranging from 4% to 40%. Direct examination of the breakthrough-curve profiles as well as mathematical-modeling results demonstrated that transport of the two longest-chain PFCAs was influenced by nonlinear AWIA, whereas that of the shorter-chain PFCAs was not. This disparate behavior is consistent with the input concentration used for the transport experiments in comparison to the respective surface activities and critical reference concentrations of the different PFCAs. Quantitative-structure/property-relationship (QSPR) analysis was applied to characterize the influence of molecular size on air-water interfacial adsorption. The logs of the air-water interfacial adsorption coefficients (Kia) determined from the transport experiments are a monotonic function of molar volume, consistent with prior QSPR analyses of surface-tension measured values. The Kia values determined from the transport experiments are very similar to those measured from surface-tension data, indicating that the transport experiments produced robust measurements of AWIA.
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Affiliation(s)
- Ying Lyu
- Key Lab of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130026, PR China; Jilin Provincial Key Laboratory of Water Resources and Environment, Jilin University, Changchun 130026, PR China; Institute of Water Resources and Environment, Jilin University, Changchun 130026, PR China.
| | - Baohua Wang
- Key Lab of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130026, PR China; Jilin Provincial Key Laboratory of Water Resources and Environment, Jilin University, Changchun 130026, PR China
| | - Xinqiang Du
- Key Lab of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun 130026, PR China; Jilin Provincial Key Laboratory of Water Resources and Environment, Jilin University, Changchun 130026, PR China
| | - Bo Guo
- Department of Hydrology and Atmospheric Sciences, University of Arizona, 429 Shantz Bldg., USA
| | - Mark L Brusseau
- Department of Hydrology and Atmospheric Sciences, University of Arizona, 429 Shantz Bldg., USA; Department of Environmental Science, University of Arizona, 429 Shantz Bldg., USA.
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15
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Stults JF, Choi YJ, Schaefer CE, Illangasekare TH, Higgins CP. Estimation of Transport Parameters of Perfluoroalkyl Acids (PFAAs) in Unsaturated Porous Media: Critical Experimental and Modeling Improvements. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:7963-7975. [PMID: 35549168 DOI: 10.1021/acs.est.2c00819] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Predicting the transport of perfluoroalkyl acids (PFAAs) in the vadose zone is critically important for PFAA site cleanup and risk mitigation. PFAAs exhibit several unusual and poorly understood transport behaviors, including partitioning to the air-water interface, which is currently the subject of debate. This study develops a novel use of quasi-saturated (residual air saturation) column experiments to estimate chemical partitioning parameters of both linear and branched perfluorooctane sulfonate (PFOS) in unsaturated soils. The ratio of linear-to-branched air-water interfacial partitioning constants for all six experiments was 1.62 ± 0.24, indicating significantly greater partitioning of linear PFOS isomers at the air-water interface. Standard breakthrough curve analysis and numerical inversion of HYDRUS models support the application of a Freundlich isotherm for PFOS air-water interfacial partitioning below a critical reference concentration (CRC). Data from this study and previously reported unsaturated column data on perfluorooctanoate (PFOA) were reevaluated to examine unsaturated systems for transport nonidealities. This reanalysis suggests both transport nonidealities and Freundlich isotherm behavior for PFOA below the CRC using drainage-based column methods, contrary to the assertions of the original authors. Finally, a combined Freundlich-Langmuir isotherm was proposed to describe PFAA air-water interfacial partitioning across the full range of relevant PFAA concentrations.
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Affiliation(s)
- John F Stults
- Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, Colorado 3557, United States
| | - Youn Jeong Choi
- Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, Colorado 3557, United States
| | - Charles E Schaefer
- CDM Smith, 110 Fieldcrest Avenue, #8, 6th Floor, Edison, New Jersey 08837, United States
| | - Tissa H Illangasekare
- Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, Colorado 3557, United States
| | - Christopher P Higgins
- Department of Civil and Environmental Engineering, Colorado School of Mines, Golden, Colorado 3557, United States
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16
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Le ST, Gao Y, Kibbey TCG, Glamore WC, O'Carroll DM. Predicting the impact of salt mixtures on the air-water interfacial behavior of PFAS. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 819:151987. [PMID: 34843785 DOI: 10.1016/j.scitotenv.2021.151987] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Revised: 11/22/2021] [Accepted: 11/22/2021] [Indexed: 06/13/2023]
Abstract
Salts are known to have strong impacts on environmental behavior of per- and polyfluoroalkyl substances (PFAS) including air-water interfacial adsorption. Multivalent salts impact interfacial adsorption to a greater extent than monovalent salts. Models to make a priori predictions of PFAS interfacial adsorption in the presence of multiple salts with different ionic charges are needed given the need to predict PFAS environmental fate. This study further develops a mass-action model to predict the interfacial behavior of PFAS as a function of both salt valency and concentration. The model is validated using surface tension data for a series of monovalent and divalent salt mixtures over a wide range of ionic strengths (i.e., from no added salt to 0.5 M) as well as comparison to data from literature. This model highlights the disproportionate impact of multivalent salts on interfacial adsorption and the practical utility of the model for predicting interfacial adsorption in the presence of multiple monovalent and multivalent inorganic salts. Results suggest that failure to account for divalent salt, even when concentrations are much smaller than monovalent salt, under most environmentally relevant aqueous phase conditions will result in significant underpredictions of PFAS interfacial adsorption. Simple examples of PFAS distribution in a range of salt conditions in the vadose zone and in aerated-water treatment reactors highlight the predictive utility of the model.
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Affiliation(s)
- Song-Thao Le
- School of Civil and Environmental Engineering, Water Research Centre, University of New South Wales, Sydney, NSW 2052, Australia
| | - Yi Gao
- School of Civil and Environmental Engineering, Water Research Centre, University of New South Wales, Sydney, NSW 2052, Australia
| | - Tohren C G Kibbey
- School of Civil Engineering and Environmental Science, University of Oklahoma, Norman, OK 73019, USA
| | - William C Glamore
- School of Civil and Environmental Engineering, Water Research Centre, University of New South Wales, Sydney, NSW 2052, Australia
| | - Denis M O'Carroll
- School of Civil and Environmental Engineering, Water Research Centre, University of New South Wales, Sydney, NSW 2052, Australia.
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17
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Huang D, Saleem H, Guo B, Brusseau ML. The impact of multiple-component PFAS solutions on fluid-fluid interfacial adsorption and transport of PFOS in unsaturated porous media. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 806:150595. [PMID: 34592291 PMCID: PMC8633151 DOI: 10.1016/j.scitotenv.2021.150595] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Revised: 09/17/2021] [Accepted: 09/22/2021] [Indexed: 05/29/2023]
Abstract
The objective of this research was to investigate the impact of multiple-component PFAS solutions on the retention of PFOS during transport in unsaturated porous media. Surface tensions were measured to characterize the impact of co-PFAS on the surface activity of PFOS. Miscible-displacement experiments were conducted to examine the air-water interfacial adsorption of PFOS during transport in single and multi-PFAS systems. Literature data for transport of PFOS in NAPL-water systems were also investigated for comparison. A mathematical model incorporating surfactant-induced flow, nonlinear rate-limited sorption, nonlinear rate-limited fluid-fluid interfacial adsorption, and competitive adsorption at the fluid-fluid interface was used to simulate the transport of PFOS. The results indicate that the presence of co-PFAS had no measurable impact on solid-phase sorption of PFOS during transport under the extant conditions of the experiments. Conversely, the air-water interfacial adsorption of PFOS was decreased by the presence of co-PFAS during transport under unsaturated-flow conditions for relatively high input concentrations. The multiple-component Langmuir model could not predict the competitive adsorption behavior observed during transport. Conversely, competitive interactions were not observed for transport with a lower input concentration. The results indicate that the retention and transport of individual PFAS in mixtures may in some cases be impacted by the presence of co-PFAS due to competitive fluid-fluid interfacial adsorption effects. Reduced retention due to competitive interfacial-adsorption interactions has the potential to decrease PFOS retardation during transport, thereby increasing migration rates in sources zones and enhancing groundwater-pollution risks. SYNOPSIS: The impact of PFAS mixtures on the retention and transport of PFOS in unsaturated porous media is examined with a series of experiments and mathematical modeling.
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Affiliation(s)
- Dandan Huang
- School of Water Resources & Environment, China University of Geosciences (Beijing), Beijing 100083, PR China; Environmental Science Department, University of Arizona, Tucson, AZ 85721, United States
| | - Hassan Saleem
- Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ 85721, United States
| | - Bo Guo
- Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ 85721, United States
| | - Mark L Brusseau
- Environmental Science Department, University of Arizona, Tucson, AZ 85721, United States; Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ 85721, United States.
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18
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Brusseau ML, Guo B. Air-water interfacial areas relevant for transport of per and poly-fluoroalkyl substances. WATER RESEARCH 2021; 207:117785. [PMID: 34731664 PMCID: PMC8665086 DOI: 10.1016/j.watres.2021.117785] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Revised: 10/12/2021] [Accepted: 10/15/2021] [Indexed: 05/15/2023]
Abstract
Per and polyfluoroalkyl substances (PFAS) present in the soil pose a long-term threat to groundwater. Robust characterization and modeling of PFAS retention and transport in unsaturated systems requires an accurate determination of the magnitude of air-water interfacial area (AWIA). Multiple methods are available for measuring or estimating air-water interfacial area, including x-ray microtomography (XMT), various aqueous and gas-phase interfacial tracer-test (ITT) methods, and thermodynamic-based estimation methods. AWIAs determined with the different methods can vary significantly. Therefore, it is critical to determine which measurement methods are relevant for application to PFAS retention and transport. This is achieved by employing AWIAs determined with different methods to simulate the results of miscible-displacement experiments reported in the literature for the transport of perfluorooctanoic acid (PFOA) in an unsaturated quartz sand. Measured PFOA breakthrough curves were successfully predicted using AWIA values measured by aqueous ITT methods. Conversely, AWIAs measured with the XMT method and estimated with the thermodynamic method under-predicted the magnitude of retardation and could not successfully simulate the measured transport data. These results indicate that the ITT method appears to provide the most appropriate AWIA values for robust characterization and modeling of PFAS transport in unsaturated systems. The long-term impact of employing different AWIA values on PFOA leaching in the vadose zone was simulated for a representative AFFF application scenario. The predicted timeframes for PFOA migration to groundwater varied from 3 to 6 to 20 years depending on which AWIA was used in the simulation. These relatively large differences would result in significantly different risk-assessment outcomes. These results illustrate that it is critical to employ the AWIA that is most representative of PFAS retention for accurate predictions of PFAS leaching in the vadose zone.
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Affiliation(s)
- Mark L Brusseau
- Environmental Science Department; Hydrology and Atmospheric Sciences Department, University of Arizona, Tucson, AZ 85721, United States.
| | - Bo Guo
- Hydrology and Atmospheric Sciences Department, University of Arizona, Tucson, AZ 85721, United States
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19
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Brusseau ML, Van Glubt S. The influence of molecular structure on PFAS adsorption at air-water interfaces in electrolyte solutions. CHEMOSPHERE 2021; 281:130829. [PMID: 33992851 PMCID: PMC8544795 DOI: 10.1016/j.chemosphere.2021.130829] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 05/04/2021] [Accepted: 05/05/2021] [Indexed: 05/19/2023]
Abstract
Fluid-fluid interfacial adsorption has been demonstrated to be an important retention process for per and polyfluoroalkyl substances (PFAS) in porous media with air or non-aqueous phase liquids (NAPLs) present. The objective of this study was to characterize the influence of PFAS molecular structure on air-water interfacial adsorption in electrolyte solutions. Measured and literature-reported surface-tension data sets were aggregated to generate the largest compilation of interfacial adsorption coefficients measured in aqueous solutions comprising environmentally representative ionic strengths. The surface activities and interfacial adsorption coefficients (Ki) exhibited chain length trends, with greater surface activities and larger Ki values corresponding to longer chain length. The impact of multiple-component PFAS solutions on the surface activity of a select PFAS was a function of the respective surface activities and concentrations. Quantitative structure-property relationship analysis (QSPR) employing a single molecular descriptor (molar volume) was used successfully to characterize the impact of PFAS molecular structure on air-water interfacial adsorption. A previously reported QSPR model based on PFAS data generated for deionized-water solutions was updated to include more than 60 different PFAS, comprising all head-group types and a wide variety of tail structures. The QSPR model developed for PFAS in electrolyte solution compared favorably to the model developed for deionized water. Additionally, the magnitude of ionic strength for non-zero ionic strength systems was determined to have relatively minimal impact on interfacial adsorption coefficients. The new QSPR model is therefore anticipated to be representative for a wide variety of PFAS and for a wide range of ionic compositions.
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Affiliation(s)
- Mark L Brusseau
- Environmental Science Department, University of Arizona, Tucson, AZ, 85721, United States.
| | - Sarah Van Glubt
- Environmental Science Department, University of Arizona, Tucson, AZ, 85721, United States
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20
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Brusseau ML, Guo B, Huang D, Yan N, Lyu Y. Ideal versus Nonideal Transport of PFAS in Unsaturated Porous Media. WATER RESEARCH 2021; 202:117405. [PMID: 34273774 PMCID: PMC8559529 DOI: 10.1016/j.watres.2021.117405] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2021] [Revised: 06/23/2021] [Accepted: 06/30/2021] [Indexed: 05/11/2023]
Abstract
Per- and poly-fluoroalkyl substances (PFAS) adsorb at air-water interfaces during transport in unsaturated porous media. This can cause surfactant-induced flow and enhanced retention that is a function of concentration, which complicates characterization and modeling of PFAS transport under unsaturated conditions. The influence of surfactant-induced flow and nonlinear air-water interfacial adsorption (AWIA) on PFAS transport was investigated with a series of miscible-displacement transport experiments conducted with a several-log range in input concentrations. Perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and ammonium perfluoro 2-methyl-3-oxahexanoate (GenX) were used as model PFAS. The results were interpreted in terms of critical reference concentrations associated with PFAS surface activities and their relationship to the relevancy of transport processes such as surfactant-induced flow and nonlinear AWIA for concentration ranges of interest. Analysis of the measured transport behavior of PFAS under unsaturated-flow conditions demonstrated that AWIA was linear when the input concentration was sufficiently below the critical reference concentration. This includes the absence of significant arrival-front self-sharpening and extended elution tailing of the breakthrough curves, as well as the similarity of retardation factors measured for a wide range of input concentrations. Independently-predicted simulations produced with a comprehensive flow and transport model that accounts for transient variably-saturated flow, surfactant-induced flow, nonlinear rate-limited solid-phase sorption, and nonlinear rate-limited AWIA provided excellent predictions of the measured transport. A series of simulations was conducted with the model to test the specific impact of various processes potentially influencing PFOS transport. The simulation results showed that surfactant-induced flow was negligible and that AWIA was effectively linear when the input concentration was sufficiently below the critical reference concentration. PFAS retention associated with AWIA can be considered to be ideal in such cases, thereby supporting the use of simplified mathematical models. Conversely, apparent nonideal transport behavior was observed for experiments conducted with input concentrations similar to or greater than the critical reference concentration.
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Affiliation(s)
- Mark L Brusseau
- Environmental Science Department, University of Arizona, Tucson, AZ, USA; Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ, USA.
| | - Bo Guo
- Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ, USA
| | - Dandan Huang
- Environmental Science Department, University of Arizona, Tucson, AZ, USA; School of Water Resources & Environment, China University of Geosciences, Beijing 100083, P.R. China
| | - Ni Yan
- Environmental Science Department, University of Arizona, Tucson, AZ, USA; Key Lab of Marine Environmental Science and Ecology, College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, P.R. China
| | - Ying Lyu
- Environmental Science Department, University of Arizona, Tucson, AZ, USA; Key Lab of Groundwater Resources and Environment, Jilin Provincial Key Laboratory of Water Resources and Environment, and Institute of Water Resources and Environment, Jilin University, Changchun, 130026, PR China
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21
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Ji Y, Yan N, Brusseau ML, Guo B, Zheng X, Dai M, Liu H. Impact of a Hydrocarbon Surfactant on the Retention and Transport of Perfluorooctanoic Acid in Saturated and Unsaturated Porous Media. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:10480-10490. [PMID: 34288652 PMCID: PMC8634892 DOI: 10.1021/acs.est.1c01919] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
The transport and retention behavior of perfluorooctanoic acid (PFOA) in the presence of a hydrocarbon surfactant under saturated and unsaturated conditions was investigated. Miscible-displacement transport experiments were conducted at different PFOA and sodium dodecyl sulfate (SDS) input ratios to determine the impact of SDS on PFOA adsorption at solid-water and air-water interfaces. A numerical flow and transport model was employed to simulate the experiments. The PFOA breakthrough curves for unsaturated conditions exhibited greater retardation compared to those for saturated conditions in all cases, owing to air-water interfacial adsorption. The retardation factor for PFOA with a low concentration of SDS (PFOA-SDS ratio of 10:1) was similar to that for PFOA without SDS under unsaturated conditions. Conversely, retardation was greater in the presence of higher levels of SDS (1:1 and 1:10) with retardation factors increasing from 2.4 to 2.9 and 3.6 under unsaturated conditions due to enhanced adsorption at the solid-water and air-water interfaces. The low concentration of SDS had no measurable impact on PFOA air-water interfacial adsorption coefficients (Kia) determined from the transport experiments. The presence of SDS at the higher PFOA-SDS concentration ratios increased the surface activity of PFOA, with transport-determined Kia values increased by 27 and 139%, respectively. The model provided very good independently predicted simulations of the measured breakthrough curves and showed that PFOA and SDS experienced various degrees of differential transport during the experiments. These results have implications for the characterization and modeling of poly-fluoroalkyl substances (PFAS) migration potential at sites wherein PFAS and hydrocarbon surfactants co-occur.
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Affiliation(s)
- Yifan Ji
- Key Lab of Marine Environmental Science and Ecology, Ministry of Education, College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, P.R. China
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
| | - Ni Yan
- Key Lab of Marine Environmental Science and Ecology, Ministry of Education, College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, P.R. China
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
- Corresponding author
| | - Mark L. Brusseau
- Environmental Science Department, University of Arizona, Tucson, AZ 85721, United States
- DepartmentDepartment of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ 85721, United States
- Corresponding author
| | - Bo Guo
- DepartmentDepartment of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, AZ 85721, United States
| | - Xilai Zheng
- Key Lab of Marine Environmental Science and Ecology, Ministry of Education, College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, P.R. China
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
| | - Mengfan Dai
- Key Lab of Marine Environmental Science and Ecology, Ministry of Education, College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, P.R. China
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
| | - Hejie Liu
- Key Lab of Marine Environmental Science and Ecology, Ministry of Education, College of Environmental Science and Engineering, Ocean University of China, Qingdao, 266100, P.R. China
- College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China
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22
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Van Glubt S, Brusseau ML. Contribution of Nonaqueous-Phase Liquids to the Retention and Transport of Per and Polyfluoroalkyl Substances (PFAS) in Porous Media. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:3706-3715. [PMID: 33666425 PMCID: PMC8634874 DOI: 10.1021/acs.est.0c07355] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Per and polyfluoroalkyl substances (PFAS) cocontamination with nonaqueous-phase organic liquids (NAPLs) has been observed or suspected at various sites, particularly at fire-training areas at which aqueous film-forming foams (AFFFs) were applied. The objectives of this study are to (1) delineate the relative significance of specific PFAS-NAPL processes on PFAS retention, including partitioning into the bulk NAPL phase and adsorption to the NAPL-water interface; (2) investigate the influence of NAPL properties, saturation, and mass-transfer constraints on PFAS retention; and (3) determine whether PFAS may impact NAPL distribution through mobilization or dissolution. Perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) are used as representative PFAS, and trichloroethene (TCE) and decane are used as representative NAPLs. NAPL-water interfacial adsorption was quantified with NAPL-water interfacial-tension measurements; partitioning into NAPL was quantified with batch experiments, and retardation factors (R) in the absence and presence of residual NAPL were determined with miscible-displacement transport experiments. R values increased in the presence of residual NAPL, with adsorption to the NAPL-water interface accounting for as much as ∼77% of retention and solid-phase adsorption also significantly contributing to retention. Additionally, this study provides the first QSPR analysis focused on NAPL-water interfacial adsorption coefficients, with results consistent with those from previous air-water studies. Lastly, this initial investigation into PFAS impacts on NAPL behavior determined that PFOS/PFOA are unlikely to enhance solubilization or mobilization of NAPL under the conditions present at many AFFF legacy sites.
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Affiliation(s)
- Sarah Van Glubt
- Environmental Science Department, University of Arizona, Tucson, AZ 85721, United States
| | - Mark L. Brusseau
- Environmental Science Department, University of Arizona, Tucson, AZ 85721, United States
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