ydrogen 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⁾).

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 (ma/u)	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 page on the Isotopes of Hydrogen.
and the 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.