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| Titel |
Contrasting online MSn spectra of organic acids in ambient aerosol from the boreal forest at Hyytiälä, Finland and from the mixed forest at the Taunus observatory, Germany |
| VerfasserIn |
Alexander L. Vogel, Mikko Äijälä, Mikael Ehn, Heikki Junninen, Tuukka Petäjä, Douglas R. Worsnop, Markku Kulmala  , Jonathan Williams, Johannes Schneider, Thorsten Hoffmann |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250081193
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| Zusammenfassung |
| Emission of biogenic volatile organic compounds (BVOCs) by the vegetation and subsequent
atmospheric oxidation leads to the formation of secondary organic aerosol (SOA). Therefore,
forests are a main source of aerosols which have significant impact on the earth´ s
climate.[1]
The oxidation of BVOCs results in a variety of mostly unidentified organic species in trace
level concentrations, which partition between gas- and particle-phase. Organic acids are of
particular importance for the particle-phase fraction, since the higher oxidation state and
molecular mass, compared to the corresponding precursors, is accompanied by a much lower
volatility. Until now, only limited instrumentation exists for the simultaneous online analysis
of organic acids in gas- and particle-phase.
Here we show the first field application of an Atmospheric Pressure Chemical Ionization Ion
Trap Mass Spectrometer (APCI-IT-MS) in combination with a miniature Versatile Aerosol
Concentration Enrichment System (mVACES) for measuring organic acids in gas- and
particle-phase[2]. The benefits of the online APCI-IT-MS are soft ionization with low
fragmentation, high time resolution and less sampling artifacts than in the common procedure
of taking filter samples, extraction and subsequent detection with LC-MS. Furthermore, the
capability to perform online MSn of isolated m/z ratios from ambient and laboratory
generated aerosol leads to an improved understanding of the composition of secondary
organic aerosol.
The here described measurements were conducted during the HUMPPA-COPEC 2010
campaign at Hyytiälä, Finland and during the INUIT campaign 2012 on Mt. Kleiner
Feldberg, Germany. By merging APCI-IT-MS data with data from the Aerodyne´ s
C-ToF-AMS, it can be observed that the gas- to particle-partitioning of organic acids strongly
depends on the fraction of aerosol which is organic matter, as it is predicted by a partitioning
model[3]. High observed gas-phase concentrations of organic acids at Hyytiälä are a strong
hint for unidentified species. This can be supported by MSn observations, where the
fragmentation pattern from Hyytiälä show different signals compared to the fragmentation
pattern from the same m/z ratio at the Taunus Observatory and from chamber terpene
ozonolysis.
Literature:
  [1] Tunved, P. et al. (2006) Science 312, 261-263.
  [2] Vogel, A. L. et al. (2012) Atmos. Meas. Tech. Discuss. 5, 6147-6182.
  [3] Pankow, J. F. (1994) Atmos. Env. 28, 189-193. |
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