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Hort HM, Robinson CE, Sawyer AH, Li Y, Cardoso R, Lee SA, Roff D, Adamson DT, Newell CJ. Conceptualizing Controlling Factors for PFAS Salting Out in Groundwater Discharge Zones Along Sandy Beaches. GROUND WATER 2024. [PMID: 38940354 DOI: 10.1111/gwat.13428] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 02/18/2024] [Accepted: 06/04/2024] [Indexed: 06/29/2024]
Abstract
Understanding fate and transport processes for per- and poly-fluoroalkyl substances (PFAS) is critical for managing impacted sites. "PFAS Salting Out" in groundwater, defined herein, is an understudied process where PFAS in fresh groundwater mixes with saline groundwater near marine shorelines, which increases sorption of PFAS to aquifer solids. While sorption reduces PFAS mass discharge to marine surface water, the fraction that sorbs to beach sediments may be mobilized under future salinity changes. The objective of this study was to conceptually explore the potential for PFAS Salting Out in sandy beach environments and to perform a preliminary broad-scale characterization of sandy shoreline areas in the continental U.S. While no site-specific PFAS data were collected, our conceptual approach involved developing a multivariate regression model that assessed how tidal amplitude and freshwater submarine groundwater discharge affect the mixing of fresh and saline groundwater in sandy coastal aquifers. We then applied this model to 143 U.S. shoreline areas with sandy beaches (21% of total beaches in the USA), indirectly mapping potential salinity increases in shallow freshwater PFAS plumes as low (<10 ppt), medium (10-20 ppt), or high (>20 ppt) along groundwater flow paths before reaching the ocean. Higher potential salinity increases were observed in West Coast bays and the North Atlantic coastline, due to the combination of moderate to large tides and large fresh groundwater discharge rates, while lower increases occurred along the Gulf of Mexico and the southern Florida Atlantic coast. The salinity increases were used to estimate potential perfluorooctane sulfonic acid (PFOS) sorption in groundwater due to salting out processes. Low-category shorelines may see a 1- to 2.5-fold increase in sorption of PFOS, medium-category a 2.0- to 6.4-fold increase, and high-category a 3.8- to 25-fold increase in PFOS sorption. The analysis presented provides a first critical step in developing a large-scale approach to classify the PFAS Salting Out potential along shorelines and the limitations of the approach adopted highlights important areas for further research.
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Affiliation(s)
- Hiroko M Hort
- GSI Environmental Inc, 7595 Irvine Center Dr, Suite 250, Irvine, CA, USA
| | - Clare E Robinson
- Department of Civil and Environmental Engineering, Western University, London, ON, Canada
| | - Audrey H Sawyer
- School of Earth Sciences, The Ohio State University, Columbus, OH
| | - Yue Li
- GSI Environmental Inc., Houston, TX, USA
| | - Rebecca Cardoso
- Navy Facilities Engineering Systems Command Southwest, San Diego, CA, USA
| | - Sophia A Lee
- Navy Facilities Engineering Systems Command Southwest, San Diego, CA, USA
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Rudani BA, Jakubowski A, Kriegs H, Wiegand S. Deciphering the guanidinium cation: Insights into thermal diffusion. J Chem Phys 2024; 160:214502. [PMID: 38828819 DOI: 10.1063/5.0215843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2024] [Accepted: 05/16/2024] [Indexed: 06/05/2024] Open
Abstract
Thermophoresis, or thermodiffusion, is becoming a more popular method for investigating the interactions between proteins and ligands due to its high sensitivity to the interactions between solutes and water. Despite its growing use, the intricate mechanisms behind thermodiffusion remain unclear. This gap in knowledge stems from the complexities of thermodiffusion in solvents that have specific interactions as well as the intricate nature of systems that include many components with both non-ionic and ionic groups. To deepen our understanding, we reduce complexity by conducting systematic studies on aqueous salt solutions. In this work, we focused on how guanidinium salt solutions behave in a temperature gradient, using thermal diffusion forced Rayleigh scattering experiments at temperatures ranging from 15 to 35 °C. We looked at the thermodiffusive behavior of four guanidinium salts (thiocyanate, iodide, chloride, and carbonate) in solutions with concentrations ranging from 1 to 3 mol/kg. The guanidinium cation is disk-shaped and is characterized by flat hydrophobic surfaces and three amine groups, which enable directional hydrogen bonding along the edges. We compare our results to the behavior of salts with spherical cations, such as sodium, potassium, and lithium. Our discussions are framed around how different salts are solvated, specifically in the context of the Hofmeister series, which ranks ions based on their effects on the solvation of proteins.
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Affiliation(s)
- Binny A Rudani
- IBI-4:Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, D-52428 Jülich, Germany
| | - Andre Jakubowski
- IBI-4:Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, D-52428 Jülich, Germany
| | - Hartmut Kriegs
- IBI-4:Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, D-52428 Jülich, Germany
| | - Simone Wiegand
- IBI-4:Biomacromolecular Systems and Processes, Forschungszentrum Jülich GmbH, D-52428 Jülich, Germany
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Hervø-Hansen S, Lin D, Kasahara K, Matubayasi N. Free-energy decomposition of salt effects on the solubilities of small molecules and the role of excluded-volume effects. Chem Sci 2024; 15:477-489. [PMID: 38179544 PMCID: PMC10763565 DOI: 10.1039/d3sc04617f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Accepted: 11/20/2023] [Indexed: 01/06/2024] Open
Abstract
The roles of cations and anions are different in the perturbation on solvation, and thus, the analyses of the separated contributions from cations and anions are useful to establish molecular pictures of ion-specific effects. In this work, we investigate the effects of cations, anions, and water separately in the solvation of n-alcohols and n-alkanes by free-energy decomposition. By utilising energy-representation theory of solvation, we address the contributions arising from the direct solute-solvent interactions and the excluded-volume effects. It is found that the change in solvation of n-alcohols and n-alkanes upon addition of salt depends primarily on the anion species. The direct interaction between the anion and solute is in agreement with the Setschenow coefficient in terms of the ranking of salting-in and salting-out for n-alkanes, which corresponds to the extent of accumulation of the anion on the solute surface. For each of the n-alcohols and n-alkanes examined, the excluded-volume component in the Setschenow coefficient is well correlated to the (total) Setschenow coefficient when the salt effects are concerned. The ranking of the excluded-volume component in the variation of the salt species is parallel to the water contribution, which is correlated further to the change in the water density upon the addition of the salt.
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Affiliation(s)
- Stefan Hervø-Hansen
- Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University Toyonaka Osaka 560-8531 Japan
| | - Daoyang Lin
- Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University Toyonaka Osaka 560-8531 Japan
| | - Kento Kasahara
- Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University Toyonaka Osaka 560-8531 Japan
| | - Nobuyuki Matubayasi
- Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University Toyonaka Osaka 560-8531 Japan
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Hervø-Hansen S, Polák J, Tomandlová M, Dzubiella J, Heyda J, Lund M. Salt Effects on Caffeine across Concentration Regimes. J Phys Chem B 2023; 127:10253-10265. [PMID: 38058160 DOI: 10.1021/acs.jpcb.3c01085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/08/2023]
Abstract
Salts affect the solvation thermodynamics of molecules of all sizes; the Hofmeister series is a prime example in which different ions lead to salting-in or salting-out of aqueous proteins. Early work of Tanford led to the discovery that the solvation of molecular surface motifs is proportional to the solvent accessible surface area (SASA), and later studies have shown that the proportionality constant varies with the salt concentration and type. Using multiscale computer simulations combined with vapor-pressure osmometry on caffeine-salt solutions, we reveal that this SASA description captures a rich set of molecular driving forces in tertiary solutions at changing solute and osmolyte concentrations. Central to the theoretical work is a new potential energy function that depends on the instantaneous surface area, salt type, and concentration. Used in, e.g., Monte Carlo simulations, this allows for a highly efficient exploration of many-body interactions and the resulting thermodynamics at elevated solute and salt concentrations.
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Affiliation(s)
- Stefan Hervø-Hansen
- Division of Computational Chemistry, Department of Chemistry, Lund University, Lund SE 221 00, Sweden
- Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Jakub Polák
- Department of Physical Chemistry, University of Chemistry and Technology, Technická 5, Praha 6, Prague CZ-16628, Czech Republic
| | - Markéta Tomandlová
- Department of Physical Chemistry, University of Chemistry and Technology, Technická 5, Praha 6, Prague CZ-16628, Czech Republic
| | - Joachim Dzubiella
- Physikalisches Institut, Albert-Ludwigs Universität Freiburg, Hermann-Herder-Straße 3, Freiburg Im Breisgau D-79104, Germany
| | - Jan Heyda
- Department of Physical Chemistry, University of Chemistry and Technology, Technická 5, Praha 6, Prague CZ-16628, Czech Republic
| | - Mikael Lund
- Division of Computational Chemistry, Department of Chemistry, Lund University, Lund SE 221 00, Sweden
- Lund Institute of Advance Neutron and X-ray Science (LINXS), Lund SE 223 70, Sweden
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