Isotope-abundance variations of selected elements (IUPAC Technical Report)

Abstract

Documented variations in the isotopic compositions of some chemical elements are responsible for expanded uncertainties in the standard atomic weights published by the Commission on Atomic Weights and Isotopic Abundances of the International Union of Pure and Applied Chemistry. This report summarizes reported variations in the isotopic compositions of 20 elements that are due to physical and chemical fractionation processes (not due to radioactive decay) and their effects on the standard atomic-weight uncertainties. For 11 of those elements (hydrogen, lithium, boron, carbon, nitrogen, oxygen, silicon, sulfur, chlorine, copper, and selenium), standard atomic-weight uncertainties have been assigned values that are substantially larger than analytical uncertainties because of common isotope-abundance variations in materials of natural terrestrial origin. For 2 elements (chromium and thallium), recently reported isotope-abundance variations potentially are large enough to result in future expansion of their atomic-weight uncertainties. For 7 elements (magnesium, calcium, iron, zinc, molybdenum, palladium, and tellurium), documented isotope variations in materials of natural ter- restrial origin are too small to have a significant effect on their standard atomic-weight uncertainties. This compilation indicates the extent to which the atomic weight of an element in a given material may differ from the standard atomic weight of the element. For most elements given above, data are graphically illustrated by a diagram in which the materials are specified in the ordinate and the compositional ranges are plotted along the abscissa in scales of (1) atomic weight, (2) mole fraction of a selected isotope, and (3) delta value of a selected isotope ratio.

Modelling the budget of middle atmospheric water vapour isotopes

“…Brasseur and Solomon (1986), with photolysis rate (Luz et al, 1999;Coplen et al, 2002), (ii) O( 3 P) is controlled by the rapid exchange reaction with O 2 (Kaye and Strobel, 1983), which shows significant Talukdar and Ravishankara (1996) a if B = 0, no temperature dependency has been measured so far. et al (1970) fractionation and leads to δ 17 O(O( 3 P))=−27.58‰ and δ 18 O(O( 3 P))=−55.30‰ (Johnston et al, 2000).…”

Tropical Atlantic SST history inferred from Ca isotope thermometry over the last 140ka

“…We present our Ca isotope data re-normalised relative to NIST SRM915a as recently proposed by Eisenhauer et al (2004) and Coplen et al (2002) …”

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

“…Previous Commission studies summarized variations in isotopic composition and atomic weight of elements exhibiting effects of natural isotopic fractionation [13][14][15]. Elements with substantial abundances of radiogenic (or nucleogenic) isotopes were excluded from those studies because ratios of radiogenic/nonradiogenic isotopes can be highly variable and do not conform to common mass-dependent isotopic fractionation relations used to estimate atomic weights from partial isotopic analyses of fractionated samples.…”