Atmos. Chem. Phys. Discuss., 13, 11213-11245, 2013
www.atmos-chem-phys-discuss.net/13/11213/2013/
doi:10.5194/acpd-13-11213-2013
© Author(s) 2013. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Emission ratio and isotopic signatures of molecular hydrogen emissions from tropical biomass burning
F. A. Haumann1,2, A. M. Batenburg1, G. Pieterse1, C. Gerbig3, M. C. Krol1,4, and T. Röckmann1
1Institute for Marine and Atmospheric research Utrecht, Utrecht University, Utrecht, the Netherlands
2Environmental Physics, Institute of Biogeochemistry and Pollutant Dynamics, ETH Zurich, Zurich, Switzerland
3Max Planck Institute for Biogeochemistry, Jena, Germany
4Department of Meteorology and Air Quality, Wageningen University, Wageningen, the Netherlands

Abstract. In this study, we identify a biomass-burning signal in molecular hydrogen (H2) over the Amazonian tropical rainforest. To quantify this signal, we measure the mixing ratios of H2 and several other species as well as the H2 isotopic composition in air samples that were collected in the BARCA (Balanço Atmosférico Regional de Carbono na Amazônia) aircraft campaign during the dry season. We derive a relative H2 emission ratio with respect to carbon monoxide (CO) of 0.31 ± 0.04 ppb/ppb and an isotopic source signature of −280 ± 41‰ in the air masses influenced by tropical biomass burning. In order to retrieve a clear source signal that is not influenced by the soil uptake of H2, we exclude samples from the atmospheric boundary layer. This procedure is supported by data from a global chemistry transport model. The ΔH2/ΔCO emission ratio is significantly lower than some earlier estimates for the tropical rainforest. In addition, our results confirm the lower values of the previously conflicting estimates of the H2 isotopic source signature from biomass burning. These values for the emission ratio and isotopic source signatures of H2 from tropical biomass burning can be used in future bottom-up and top-down approaches aiming to constrain the strength of the biomass-burning source for H2. Hitherto, these two quantities relied only on combustion experiments or on statistical relations, since no direct signal had been obtained from in-situ observations.

Citation: Haumann, F. A., Batenburg, A. M., Pieterse, G., Gerbig, C., Krol, M. C., and Röckmann, T.: Emission ratio and isotopic signatures of molecular hydrogen emissions from tropical biomass burning, Atmos. Chem. Phys. Discuss., 13, 11213-11245, doi:10.5194/acpd-13-11213-2013, 2013.
 
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