Developing antimony stable isotope methods as a new geochemical redox indicator: computational isotopic fractionation studies
Shay, Hannah
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https://hdl.handle.net/2142/110674
Description
Title
Developing antimony stable isotope methods as a new geochemical redox indicator: computational isotopic fractionation studies
Author(s)
Shay, Hannah
Issue Date
2021-04-26
Director of Research (if dissertation) or Advisor (if thesis)
Johnson, Thomas M.
Murphy, Catherine J.
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Keyword(s)
Isotope Fractionation
Paleoredox proxies
computational chemistry
ab intio DFT
geochemistry
Abstract
Understanding and tracing redox conditions is an important question in many geochemical applications in modern and ancient environments. The stable isotope variations that occur as a result of redox reactions can be used as proxy systems to elucidate these processes. Preliminary experiments involving antimony have shown that it may be promising for applications to contaminant tracing or as a paleoredox proxy. However, currently there is limited work done to understand the isotope fractionation behavior of antimony.
Using ab initio and density functional methods, the work here reports equilibrium Sb-isotope ratio fractionations for 123Sb/121Sb. The reduced partition function ratios for several geochemically relevant species are calculated and presented. The calculations predict significant, measurable fractionations ranging from 1-4‰ between coexisting species with different oxidation states. This study also indicates that the more oxidized the antimony species is, the larger the fractionation relative to similarly charged but less oxidized equivalents. The results indicate the potential use of the 123Sb/121Sb isotope system as a redox proxy and tracer in modern and ancient environments.
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