文档介绍：Lectured by : Zeqin Li
Department Environmental Science & Engineering
Chengdu University of Technology
Chengdu, Sichant (K) for isotopic
differentiation of complex
molecules
Example:
For water (l) in EQ with vapour (v), the fractionation of O isotopes in water molecules is:

 lv = Rl/Rv = at 25oC
for H in water:
 lv = Rl/Rv = at 25oC
General Rules for αab
T:  is T dependent, eg.  = f (T). Isotope fractionation factors are greater at lower temperatures (vibration frequency gos to up limit)
Reduced- oxidised: Light isotopes are enriched in reduced species and heavy isotopes are enriched in oxidised species. S
Biogenic: Light isotopes are enriched in biogenic compounds, S &C
Example:
δ spl = (Rspl - Rstd)/Rstd x 1000‰
for O: δ18Ospl = [Rspl-Rstd/R std] x 103 ‰
Isotope δ Value
the isotopeδ to express
a sample’s isotope composition
The data in Table indicate that 18O/16O ratio of average terrestrial is = and that D/H ration is . Because it is difficult to measure small differences in such small ratios, the isotope composition of H, O, C and S are expressed as the per mille difference of the isotope ratios of a sample(spl) and a standard(std).
δ18Ospl = [(18O/16O)spl - (18O/16O)std/(18O/16O) std] x 103 ‰
δ34Sspl = [(34S/32S)spl-(34S/32S)std/(34S/32S) std] x 103
for S: δ34Sspl = [Rspl-Rstd/R std] x 103 ‰
Positive δ values indicate that the sample is enriched in heavy isotopes relative to standard or depleted in light.
Negative δ values indicate that the sample is depleted in heavy isotopes relative to standard or enriched in light.
 values express the deviation of Rspl from Rstd in ‰,
δ18Ospl = [(18O/16O)spl - (18O/16O)std/(18O/16O) std] x 103 ‰
Again: δ spl = (Rspl - Rstd)/Rstd x 1000‰
Stable Isotope Standards
H, O: Standard Mean Ocean Water (SMOW) by Craig (1961).
SMOW: D/H=; 18O/16O=

C, O: Belemnite from the P