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| Titel |
D/H Isotope Ratio Measurements of Atmospheric Volatile Organic Compounds |
| VerfasserIn |
Thomas Meisehen, Fred Bühler, Ralf Koppmann, Marc Krebsbach |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250102463
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| Publikation (Nr.) |
 EGU/EGU2015-1779.pdf |
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| Zusammenfassung |
| Analysis of isotope ratios in atmospheric volatile organic compounds (VOC) is a
reliable method to allocate their sources, to estimate atmospheric residence times and
investigate physical and chemical processes on various temporal and spatial scales.
Most investigations yet focus on carbon isotope ratios. Certainly more detailed
information can be gained by the ratio of deuterium (D) to hydrogen (H) in VOC,
especially due to the high mass ratio. Combining measurements of carbon and hydrogen
isotopes could lead to considerable improvement in our understanding of atmospheric
processes.
For this purpose we set up and thoroughly characterised a gas chromatograph pyrolysis
isotope ratio mass spectrometer to measure the D/H ratio in atmospheric VOC. From a
custom-made gas standard mixture VOC were adsorbed on Tenax®TA which has the
advantage that CO2 is not preconcentrated when measuring ambient air samples. Our results
show that the pyrolysis method has significant impact on the D/H ratios. A pyrolysis
temperature of at least 1723 K and conditioning of the ceramic tube on a regular basis is
essential to obtain reproducible D/H isotope ratios. For an independent comparison D/H
ratios of the pure VOC used in the gas standard were determined using elemental
analysis by Agroisolab (Jülich, Germany). Comparisons of 10 VOC show perfect
agreement within the standard deviations of our measurements and the errors given by
Agroisolab, e.g. for n-pentane, toluene, 4-methyl-2-pentanone and n-octane. A
slight mean difference of 5.1 o was obtained for n-heptane while significant mean
differences of 15.5 o and 20.3 o arose for 1,2,4-trimethylbenzene and isoprene,
respectively.
We further demonstrate the stability of our system and show that the sample preparation
does not affect the isotope ratios. Moreover the applicability of our system to ambient air
samples is demonstrated. |
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