Definition 14.5University Earth and Space Sciences — Year 3 · 第 14 章 — Stable-Isotope Geochemistry
The deuterium excess of a water sample is d=δD−8δ18O, in per mil.
Rayleigh distillation of an air mass cooled at constant pressure from 0∘C, with the ice–vapour fractionation factors and the fraction of vapour left read from the sublimation curve of ice. (a) The vapour (dashed) and the snow (solid) grow lighter ever faster; the dots are the three stations of the weekend problem. (b) The model snow stays close to the meteoric water line down to about −30‰ in oxygen-18, then rises above it.