21 August 2003

D/H ratio: Hydrogen budget

Molecular hydrogen (H2) is the second most abundant trace gas in the atmosphere (after methane), and is present in the troposphere at about 530 parts per billion. In the troposphere, the deuterium-to-hydrogen (D/H) ratio of molecular hydrogen is enriched relative to the worldÕs oceans. This cannot be explained by the sources of H2 for which the D/H ratio has been measured to date. High-precision measurements of the deuterium content of H2 in the stratosphere now reveal that it becomes remarkably deuterium-rich owing to the production of molecular hydrogen from methane oxidation. At 440 parts per thousand, it is the most extreme D/H ratio observed in a terrestrial material. This enrichment is estimated to be similar in the troposphere and could explain the enigmatic D/H ratio of tropospheric H2.

Extreme deuterium enrichment in stratospheric hydrogen and the global atmospheric budget of H₂
THOM RAHN, JOHN M. EILER, KRISTIE A. BOERING, PAUL O. WENNBERG, MICHAEL C. MCCARTHY, STANLEY TYLER, SUE SCHAUFFLER, STEPHEN DONNELLY & ELLIOT ATLAS
Nature 424, 918–921 (2003); doi:10.1038/nature01917
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