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Mercury Isotope Fractionation during Dark Abiotic Reduction of Hg(II) by Dissolved, Surface-Bound, and Structural Fe(II)
[Image: see text] Stable mercury (Hg) isotope ratios are an emerging tracer for biogeochemical transformations in environmental systems, but their application requires knowledge of isotopic enrichment factors for individual processes. We investigated Hg isotope fractionation during dark, abiotic red...
Autores principales: | , , , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
American Chemical Society
2023
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Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10569049/ https://www.ncbi.nlm.nih.gov/pubmed/37748105 http://dx.doi.org/10.1021/acs.est.3c03703 |
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author | Schwab, Lorenz Gallati, Niklas Reiter, Sofie M. Kimber, Richard L. Kumar, Naresh McLagan, David S. Biester, Harald Kraemer, Stephan M. Wiederhold, Jan G. |
author_facet | Schwab, Lorenz Gallati, Niklas Reiter, Sofie M. Kimber, Richard L. Kumar, Naresh McLagan, David S. Biester, Harald Kraemer, Stephan M. Wiederhold, Jan G. |
author_sort | Schwab, Lorenz |
collection | PubMed |
description | [Image: see text] Stable mercury (Hg) isotope ratios are an emerging tracer for biogeochemical transformations in environmental systems, but their application requires knowledge of isotopic enrichment factors for individual processes. We investigated Hg isotope fractionation during dark, abiotic reduction of Hg(II) by dissolved iron(Fe)(II), magnetite, and Fe(II) sorbed to boehmite or goethite by analyzing both the reactants and products of laboratory experiments. For homogeneous reduction of Hg(II) by dissolved Fe(II) in continuously purged reactors, the results followed a Rayleigh distillation model with enrichment factors of −2.20 ± 0.16‰ (ε(202)Hg) and 0.21 ± 0.02‰ (E(199)Hg). In closed system experiments, allowing reequilibration, the initial kinetic fractionation was overprinted by isotope exchange and followed a linear equilibrium model with −2.44 ± 0.17‰ (ε(202)Hg) and 0.34 ± 0.02‰ (E(199)Hg). Heterogeneous Hg(II) reduction by magnetite caused a smaller isotopic fractionation (−1.38 ± 0.07 and 0.13 ± 0.01‰), whereas the extent of isotopic fractionation of the sorbed Fe(II) experiments was similar to the kinetic homogeneous case. Small mass-independent fractionation of even-mass Hg isotopes with 0.02 ± 0.003‰ (E(200)Hg) and ≈ −0.02 ± 0.01‰ (E(204)Hg) was consistent with theoretical predictions for the nuclear volume effect. This study contributes significantly to the database of Hg isotope enrichment factors for specific processes. Our findings show that Hg(II) reduction by dissolved Fe(II) in open systems results in a kinetic MDF with a larger ε compared to other abiotic reduction pathways, and combining MDF with the observed MIF allows the distinction from photochemical or microbial Hg(II) reduction pathways. |
format | Online Article Text |
id | pubmed-10569049 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2023 |
publisher | American Chemical Society |
record_format | MEDLINE/PubMed |
spelling | pubmed-105690492023-10-13 Mercury Isotope Fractionation during Dark Abiotic Reduction of Hg(II) by Dissolved, Surface-Bound, and Structural Fe(II) Schwab, Lorenz Gallati, Niklas Reiter, Sofie M. Kimber, Richard L. Kumar, Naresh McLagan, David S. Biester, Harald Kraemer, Stephan M. Wiederhold, Jan G. Environ Sci Technol [Image: see text] Stable mercury (Hg) isotope ratios are an emerging tracer for biogeochemical transformations in environmental systems, but their application requires knowledge of isotopic enrichment factors for individual processes. We investigated Hg isotope fractionation during dark, abiotic reduction of Hg(II) by dissolved iron(Fe)(II), magnetite, and Fe(II) sorbed to boehmite or goethite by analyzing both the reactants and products of laboratory experiments. For homogeneous reduction of Hg(II) by dissolved Fe(II) in continuously purged reactors, the results followed a Rayleigh distillation model with enrichment factors of −2.20 ± 0.16‰ (ε(202)Hg) and 0.21 ± 0.02‰ (E(199)Hg). In closed system experiments, allowing reequilibration, the initial kinetic fractionation was overprinted by isotope exchange and followed a linear equilibrium model with −2.44 ± 0.17‰ (ε(202)Hg) and 0.34 ± 0.02‰ (E(199)Hg). Heterogeneous Hg(II) reduction by magnetite caused a smaller isotopic fractionation (−1.38 ± 0.07 and 0.13 ± 0.01‰), whereas the extent of isotopic fractionation of the sorbed Fe(II) experiments was similar to the kinetic homogeneous case. Small mass-independent fractionation of even-mass Hg isotopes with 0.02 ± 0.003‰ (E(200)Hg) and ≈ −0.02 ± 0.01‰ (E(204)Hg) was consistent with theoretical predictions for the nuclear volume effect. This study contributes significantly to the database of Hg isotope enrichment factors for specific processes. Our findings show that Hg(II) reduction by dissolved Fe(II) in open systems results in a kinetic MDF with a larger ε compared to other abiotic reduction pathways, and combining MDF with the observed MIF allows the distinction from photochemical or microbial Hg(II) reduction pathways. American Chemical Society 2023-09-25 /pmc/articles/PMC10569049/ /pubmed/37748105 http://dx.doi.org/10.1021/acs.est.3c03703 Text en © 2023 The Authors. Published by American Chemical Society https://creativecommons.org/licenses/by/4.0/Permits the broadest form of re-use including for commercial purposes, provided that author attribution and integrity are maintained (https://creativecommons.org/licenses/by/4.0/). |
spellingShingle | Schwab, Lorenz Gallati, Niklas Reiter, Sofie M. Kimber, Richard L. Kumar, Naresh McLagan, David S. Biester, Harald Kraemer, Stephan M. Wiederhold, Jan G. Mercury Isotope Fractionation during Dark Abiotic Reduction of Hg(II) by Dissolved, Surface-Bound, and Structural Fe(II) |
title | Mercury Isotope
Fractionation during Dark Abiotic
Reduction of Hg(II) by Dissolved, Surface-Bound, and Structural Fe(II) |
title_full | Mercury Isotope
Fractionation during Dark Abiotic
Reduction of Hg(II) by Dissolved, Surface-Bound, and Structural Fe(II) |
title_fullStr | Mercury Isotope
Fractionation during Dark Abiotic
Reduction of Hg(II) by Dissolved, Surface-Bound, and Structural Fe(II) |
title_full_unstemmed | Mercury Isotope
Fractionation during Dark Abiotic
Reduction of Hg(II) by Dissolved, Surface-Bound, and Structural Fe(II) |
title_short | Mercury Isotope
Fractionation during Dark Abiotic
Reduction of Hg(II) by Dissolved, Surface-Bound, and Structural Fe(II) |
title_sort | mercury isotope
fractionation during dark abiotic
reduction of hg(ii) by dissolved, surface-bound, and structural fe(ii) |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10569049/ https://www.ncbi.nlm.nih.gov/pubmed/37748105 http://dx.doi.org/10.1021/acs.est.3c03703 |
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