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Variation in the terrestrial isotopic composition and atomic weight of argon (IUPAC Technical Report)

Published/Copyright: November 18, 2014
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Chemistry International
From the journal Chemistry International Volume 36 Issue 6

Pure and Applied Chemistry, 2014Volume 86, Issue 9, pp. 1421–1432

The isotopic composition and atomic weight of argon (Ar) are variable in terrestrial materials. Those variations are a source of uncertainty in the assignment of standard properties for Ar, but they provide useful information in many areas of science. Variations in the stable isotopic composition and atomic weight of Ar are caused by several different processes, including (1) isotope production from other elements by radioactive decay (radiogenic isotopes) or other nuclear transformations (e.g., nucleogenic isotopes), and (2) isotopic fractionation by physical-chemical processes such as diffusion or phase equilibria. Physical-chemical processes cause correlated mass-dependent variations in the Ar isotope-amount ratios (40Ar/36Ar, 38Ar/36Ar), whereas nuclear transformation processes cause non-mass-dependent variations. While atmospheric Ar can serve as an abundant and homogeneous isotopic reference, deviations from the atmospheric isotopic ratios in other Ar occurrences limit the precision with which a standard atomic weight can be given for Ar. Published data indicate variation of Ar atomic weights in normal terrestrial materials between about 39.7931 and 39.9624. The upper bound of this interval is given by the atomic mass of 40Ar, as some samples contain almost pure radiogenic 40Ar. The lower bound is derived from analyses of pitchblende (uranium mineral) containing large amounts of nucleogenic 36Ar and 38Ar. Within this interval, measurements of different isotope ratios (40Ar/36Ar or 38Ar/36Ar) at various levels of precision are widely used for studies in geochronology, water–rock interaction, atmospheric evolution, and other fields.

This report is part of the output of IUPAC project 2009-023-1-200, “Evaluation of radiogenic isotopic abundance variations in selected elements,” chaired by M. E. Wieser.

http://dx.doi.org/10.1515/pac-2013-0918

Online erschienen: 2014-11-18
Erschienen im Druck: 2014-11-1

©2014 by Walter de Gruyter Berlin/Boston

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https://doi.org/10.1515/ci-2014-0624

Articles in the same Issue

  1. Masthead - Full issue pdf
  2. From the Editor
  3. Contents
  4. Features
  5. Planetary Boundaries and Chemical Pollution: A Grail Quest?
  6. Research Integrity: Science Community Needs to Address Threats by Research Assessments
  7. IUPAC and ICSU—A Comment
  8. Invitation to host the ICSU Secretariat for the Committee on Freedom and Responsibility in the conduct of Science (CFRS)
  9. Drug Design and Development: A Research Center More Than Twenty Years in the Making
  10. Youth Views on Sustainability: Size Matters, But So Does Speed
  11. IUPAC Wire
  12. Mort Hoffman Receives Chemistry Education Award
  13. Vânia G. Zuin is awarded the CHEMRAWN VII Prize for Atmospheric and Green Chemistry
  14. Sébastien Perrier received the 2014 IUPAC- Samsung Young Polymer Scientist Award
  15. DSM Materials Sciences Award 2014 goes to Prof. Jian Ping Gong
  16. 2015 IUPAC-SOLVAY International Award for Young Chemists announced
  17. In Memoriam: Gerrit den Boef
  18. The Project Place
  19. Critically evaluated rate parameters for chain-length-dependent termination in radical polymerization of styrene and n-alkyl methacrylates
  20. Guidelines for assigning values and calculating uncertainties to the standard atomic weights
  21. Nano-pesticides in the Environment
  22. Medicinal Chemistry in Drug Discovery, India
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  27. Single-molecule fluorescence imaging by total internal reflection fluorescence microscopy (IUPAC Technical Report)
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