Atmospheric Physics and Chemistry Group (APCG)


Past Projects

Investigation of the global hydrogen cycle with isotope measurements

Anneke Batenburg


At present, the atmosphere contains approximately 0.5 ppmv of molecular hydrogen (H2). The largest sources of the H2 to the atmosphere are the oxidation of methane and other hydrocarbons, and incomplete combustion of fossil fuels or biomass. Microbial processes constitute minor H2 sources. About three quarters of the H2 thus produced is taken up by soils, and about a quarter is oxidized by the hydroxyl radical (OH). Large uncertainties still exist in the estimates of the magnitudes of these different H2 sources and sinks.

Over the past decades, H2 levels in the atmosphere do not seem to have increased or decreased much. This may change, however, if H2 is used on a large scale as a `clean’ energy carrier. In such a `hydrogen economy’, the inevitable leakage from storage containers and vehicles will lead to increased atmospheric levels of H2. This may have effects on the ozone layer and the lifetimes of greenhouse gases.

This project aims to gain insight into the global hydrogen cycle by combining isotope measurements with modelling. Isotope effects are particularly large in the H2 cycle due to the large relative mass difference between deuterated H2 (HD) and nondeuterated H2 (HH).

The GC-IRMS (Gas Chromatography – Isotope Ratio Mass Spectrometry) system at IMAU is the only system in Europe capable of measuring the deuterium content of H2 (dD-H2). In collaboration with European project partners we measure δD-H2 on air samples from several ground stations around the world, as well as from aircraft samples. These data will be used to validate global chemistry models, and to reduce the uncertainties in our knowledge of the H2 cycle. This will help to assess the effects of increased hydrogen emissions on the atmosphere on a global and regional scale.