FAVOR-HALO: Fast Analysis of Volatile ORganics with gas chromatography/mass spectrometry (GC/MS) on HALO
Zusammenfassung der Projektergebnisse
Within the project a fast GC/MS has been developed which is capable to measure 49 different volatile organic compounds (VOC) with a time resolution of three minutes. The GC/MS operated successfully on a mobile lab and on three Zeppelin campaigns from 2011 to 2013 above Southern and Northern Europe. During these campaigns, more than 300 hours of VOC data from measurements in the planetary boundary layer have been collected and analyzed. While the concentration of oxygenated volatile organic compounds (OVOCs) were high throughout the boundary layer, elevated concentrations of their nonoxygenated precursors where mainly found close to the surface from where they were emitted. This height dependency was especially pronounced with VOC that are rapidly degraded in the troposphere, e.g. isoprene. Both nonoxygenated and oxygenated VOC react with the OH radical and determine the lifetime of OH, the main oxidant of the atmosphere. Since the OH lifetime was directly measured during the Zeppelin campaign we could demonstrate that on average the OH lifetime can be explained from the reactions of the individual compounds measured from the Zeppelin. Only close to the ground, a small portion of the OH loss rate processes remained unexplained. Reactions with oxygenated VOC were found to be the most important loss processes of the OH radicals. After incorporating the individual VOC species in a numerical model it was possible to show that nitrous acid (HONO) was not emitted from the surface but is produced from a volume source. The concentration of nonoxygenated VOC measured during the Zeppelin campaigns was low compared to the data of previous ground-based campaigns. The concentration of oxygenated volatile organic compounds exceeded the concentration of nonoxygenated VOC, especially at high altitudes. Comparisons with numerical simulations will show if the formation of oxygenated VOC can be explained with known processes or if there are other sources for the formation of the OVOC. Nitrous acid was previously thought to be emitted from the ground. At sunlight nitrous acid is photolyzed to produce OH radicals. During the Zeppelin measurements it was found that nitrous acid is a gas phase source and produced from the HO2 radical, NO2 and water. The fact that HONO is not only a radical source but also produced from radicals has not been found before and means that the role of nitrous acid as radical source has been overestimated in the past.
Projektbezogene Publikationen (Auswahl)
- 2010. Development of a fast GC/MS-system for airborne measurements of Volatile Organic Compounds. Geophysical Research Abstracts, Vol. 12.2010, 4254.
Wenk, A.-K., Wegener, R., Hofzumahaus, A., Wahner, A.
- 2013. Measurements of Volatile Organic Compounds (VOCs) on Board of
the Zeppelin NT during the PEGASOS Campaign in 2012. Geophysical Research Abstracts, Vol. 15. 2013, 5297.
Jäger, J., Hofzumahaus, A., Beck, B., Rohrer, F., Broch, S. F., Gomm, S., Holland, F, Lu, K., Kiendler-Scharr, A., Mentel, T. F., Rose, B., Wegener, R., Wahner, A.
- 2014. Airborne VOC measurements on board the Zeppelin NT during the
PEGASOS campaigns in 2012 deploying the improved Fast-GC-MSD System.
Schriften des Forschungszentrums Jülich, Reihe Energie & Umwelt, Bd. 205. Zugl.: Köln, Univ., Department of Mathematics and Science, Diss., 2013, 182 S.
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Jäger, J.
- 2014. Missing Gas-Phase Source of HONO Inferred from Zeppelin
Measurements in the Troposphere. Science, Vol. 344. 2014, Issue 6181, pp. 292-296.
Wahner, A. et al
(Siehe online unter https://doi.org/10.1126/science.1248999) - 2014. Total OH reactivity measurements aboard the Zeppelin NT during the PEGASOS campaign 2012: Contributions of substance classes to the total OH reactivity. Geophysical Research Abstracts, Vol. 16.2014: EGU2014-3429-1.
Wegener, R., Jäger, J, Hofzumahaus, A., Rohrer, F., Bohn, B., Brauers, T., Broch, S., Gomm, S., Häseler, R., Holland, F., Kaiser, J. B., Keutsch, F., Li, X., Lohse, I., Lu, K., Tillmann, R., Wolfe, G. M., Mentel, T. F., Kiendler-Scharr, A., Wahner, A.
