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Stable Isotopes

Hydrogen Isotopes

Hydrogen has two naturally occurring stable isotopes (1H or just H, and 2H or D for Deuterium), and one naturally occurring radioactive isotope (3H, or T for Tritium). For studies of stable isotope biogeochemistry we measure the ratio of D to H in samples of interest, expressed relative to the ratio in a standard of known isotopic composition, usually "Vienna Standard Mean Ocean Water" as prepared by the International Atomic Energy Agency in Vienna (V-SMOW; D/H = 0.00015595 (1)(2)).

Formula for delta 2H

The dD values of terrestrial hydrogen samples (as in water) typically range from -450 to +50 per mil relative to V-SMOW (1).

The KSC Center for Environmental BioGeoChemistry is not equipped to measure Tritium concentrations.

Isotope Atomic mass
Natural abundance
(atom %)
1H 1.007825035 99.9885
2H or
D (Deuterium)
2.014101779 0.0115
3H or
T (Tritium)
3.01604927 half-life of 12.32 years
decays by b- to 3He

See the WebElements page on the Isotopes of Hydrogen.
and the Chart of the Nuclides centered on H.

(1)From Table 9-1, p. 154, of David P. Mattey, 1997, Gas source mass spectrometry: isotopic composition of lighter elements, pages 154-170 in Robin Gill (editor), Modern Analytical Geochemistry, Longman (UK).

(2)The uncertainty in this value is much larger than the precision with which we can measure relative ratios, which is one reason for the use the "delta" notation; page 32 in Robert E. Criss, 1999, Principles of Stable Isotope Distribution, Oxford University Press.

KSC Center for Environmental BioGeoChemistry

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January 2009