Deuterium, Deuterium Excess

Measurements

Deuterium is the heavy stable isotope of hydrogen, ²H or D, with a natural occurrence on Earth (²H/¹H isotopic ratio, hereafter D/H) of ∼153 × 10⁻⁶ (Lécuyer et al., 1998). For the purpose of reconstructing paleoenvironments, it is commonly measured in paleowaters (e.g., groundwaters, ice, fluid inclusions), organic matter (e.g., tree cellulose), and hydroxylated minerals (e.g., clays, hydroxides), in which the D/H ratio ranges between approximately 160 × 10⁻⁶ and 80 × 10⁻⁶ (Mook, 2001; Jouzel, 2003).

The D/H ratio of a sample is measured by mass spectrometry on H₂ (hydrogen gas), after either a total reduction of the water, or a catalytic equilibration with H₂. Both techniques allow some automation, but the latter requires larger sample volume (few ml, compared with few μl for the former). A new laser spectrometric technique is achieving promising results (Kerstel et al., 1999). The isotopic composition is usually expressed relative to a standard, currently the Vienna...