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| Titel |
IUPAC Project: Terminology and definition of quantities related to the isotope distribution in elements with more than two stable isotopes |
| VerfasserIn |
J. Kaiser, A. Angert, B. Bergquist, W. Brand, S. Ono, T. Röckmann, J. Savarino |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250071396
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| Zusammenfassung |
| The objective of IUPAC Project 2009-046-2-200 (http://www.iupac.org/web/ins/2009-046-2-200)
is to define terminology and to identify the most suitable definitions of quantities that
characterise the isotope distribution in elements with more than two stable isotopes, including
so-called mass-independent fractionation, non-mass dependent fractionation, isotope
anomaly, 17O excess, etc.
Most atmospheric oxygen-bearing species show deviations in their triple oxygen isotope
ratios from mass-dependent fractionation (MDF) relationships predicted by the theories of
Urey, Bigeleisen and Mayer. Similar deviations have also been found in sulphur
and other elements with more than two stables isotopes (e.g. Hg, Cd, Zn), often
preserved in non-atmospheric reservoirs, including rocks, minerals, soils, ice and
waters.
Despite the ubiquity of this type of isotope anomaly, there has never been an attempt
to clearly define the terminology and physical quantities used to measure these
anomalies and the processes that lead to their formation. Terms like mass-independent
fractionation, non-mass dependent fractionation, isotope anomaly, isotope excess
etc. have been used in the historic and recent literature, but are often not carefully
distinguished. The realisation that MDF comprises a range of possible relationships
between the isotopes of one element led to further complications because it meant that
apparent isotope anomalies could be created by a combination of different MDF
processes.
At the moment, at least four different definitions to quantify isotope anomalies are being
used. Furthermore, coefficients used in these definitions vary, which makes the comparison of
data from different sources very difficult, even for experts.
A consistent set of recommendations on how to express and quantify the isotope
distribution in elements with more than two stable isotopes is highly warranted. From our
experience as academic teachers, we are woefully aware how impenetrable the
field is for young researchers at the moment because of the lack of consistency and
the lack of understanding between different groups. This project seeks to alleviate
this. |
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