Oxygen isotopic signature of CO2 from combustion processes
| Autor: | Schumacher, Marcus, Neubert, Rolf E.M., Meijer, Harro A.J., Jansen, Henk G., Brand, Willi A., Geilmann, Heike, Werner, Roland Anton |
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| Jazyk: | angličtina |
| Rok vydání: | 2008 |
| Zdroj: | Atmospheric Chemistry and Physics Discussions, 8 (6) |
| ISSN: | 1680-7375 1680-7367 |
| DOI: | 10.3929/ethz-b-000013862 |
| Popis: | For a comprehensive understanding of the global carbon cycle precise knowledge ofall processes is necessary. Stable isotope (13C and18O) abundances provide infor-mation for the qualification and the quantification of the diverse source and sink pro-cesses. This study focuses on theδ18O signature of CO2from combustion processes, which are widely present both naturally (wild fires), and human induced (fossil fuelcombustion, biomass burning) in the carbon cycle. All these combustion processesuse atmospheric oxygen, of which the isotopic signature is assumed to be constantwith time throughout the whole atmosphere. The combustion is generally presumedto take place at high temperatures, thus minimizing isotopic fractionation. Therefore it is generally supposed that the18O signature of the produced CO2is equal to that ofthe atmospheric oxygen. This study, however, reveals that the situation is much morecomplicated and that important fractionation effects do occur. From laboratory studiesfractionation effects in the order of about 26‰ became obvious, a clear differentiation ofabout 7‰ was also found in car exhausts which were sampled directly under ambient atmospheric conditions.We investigated a wide range of materials (both different raw materials and similarmaterials with different inherent18O signature), sample geometries (e.g. texture andsurface-volume ratios) and combustion circumstances. We found that the main factorinfluencing the specific isotopic signatures of the combustion-derived CO2and of the concomitantly released oxygen-containing side products, is the case-specific rate ofcombustion. This points firmly into the direction of (diffusive) transport of oxygen to thereaction zone as the cause of the isotope fractionation. The original18O signature ofthe material appeared to have little or no influence. Atmospheric Chemistry and Physics Discussions, 8 (6) ISSN:1680-7375 ISSN:1680-7367 |
| Databáze: | OpenAIRE |
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