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Hearon SE, Orr AA, Moyer H, Wang M, Tamamis P, Phillips TD. Montmorillonite clay-based sorbents decrease the bioavailability of per- and polyfluoroalkyl substances (PFAS) from soil and their translocation to plants. Environ Res 2022; 205:112433. [PMID: 34875259 PMCID: PMC8760172 DOI: 10.1016/j.envres.2021.112433] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2021] [Revised: 10/06/2021] [Accepted: 11/23/2021] [Indexed: 05/23/2023]
Abstract
Consumption of food and water contaminated with per- and polyfluoroalkyl substances (PFAS) presents a significant risk for human exposure. There is limited data on high affinity sorbents that can be used to reduce the bioavailability of PFAS from soil and translocation to plants and garden produce. To address this need, montmorillonite clay was amended with the nutrients carnitine and choline to increase the hydrophobicity of the sorbent and the interlayer spacing. In this study, the binding of PFOA (perfluorooctanoic acid) and PFOS (perfluorooctanesulfonic acid) to parent and amended clays was characterized. Isothermal analyses were conducted at pH 7 and ambient temperature to simulate environmentally-relevant conditions. The data for all tested sorbents fit the Langmuir model indicating saturable binding sites with high capacities and affinities under neutral conditions. Amended montmorillonite clays had increased capacities for PFOA and PFOS (0.51-0.71 mol kg-1) compared to the parent clay (0.37-0.49 mol kg-1). Molecular dynamics (MD) simulations suggested that hydrophobic and electrostatic interactions at the terminal fluorinated carbon chains of PFAS compounds were major modes of surface interaction. The safety and efficacy of the clays were confirmed in a living organism (Lemna minor), where clays (at 0.1% inclusion) allowed for increased growth compared to PFOA and PFOS controls (p ≤ 0.01). Importantly, soil studies showed that 2% sorbent inclusion could significantly reduce PFAS bioavailability from soil (up to 74%). Studies in plants demonstrated that inclusion of 2% sorbent significantly reduced PFAS residues in cucumber plants (p ≤ 0.05). These results suggest that nutrient-amended clays could be included in soil to decrease PFAS bioavailability and translocation of PFAS to plants.
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Affiliation(s)
- Sara E Hearon
- Veterinary Integrative Biosciences Department, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, 77845, USA
| | - Asuka A Orr
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX, 77843, USA
| | - Haley Moyer
- Veterinary Integrative Biosciences Department, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, 77845, USA
| | - Meichen Wang
- Veterinary Integrative Biosciences Department, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, 77845, USA
| | - Phanourios Tamamis
- Artie McFerrin Department of Chemical Engineering, Texas A&M University, College Station, TX, 77843, USA; Department of Materials Science and Engineering, Texas A&M University, College Station, TX, 77843, USA
| | - Timothy D Phillips
- Veterinary Integrative Biosciences Department, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX, 77845, USA.
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