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| Titel |
Determination of the biogenic secondary organic aerosol fraction in the boreal forest by NMR spectroscopy |
| VerfasserIn |
E. Finessi, S. Decesari, M. Paglione, L. Giulianelli, C. Carbone, S. Gilardoni, S. Fuzzi, S. Saarikoski, T. Raatikainen, R. Hillamo, J. Allan, Th. F. Mentel, P. Tiitta, A. Laaksonen, T. Petäjä, M. Kulmala  , D. R. Worsnop, M. C. Facchini |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 2 ; Nr. 12, no. 2 (2012-01-19), S.941-959 |
| Datensatznummer |
250010540
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| Publikation (Nr.) |
 copernicus.org/acp-12-941-2012.pdf |
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| Zusammenfassung |
The study investigates the sources of fine organic aerosol (OA) in the
boreal forest, based on measurements including both filter sampling
(PM1) and online methods and carried out during a one-month campaign
held in Hyytiälä, Finland, in spring 2007. Two aerosol mass
spectrometers (Q-AMS, ToF-AMS) were employed to measure on-line
concentrations of major non-refractory aerosol species, while the water
extracts of the filter samples were analyzed by nuclear magnetic resonance
(NMR) spectroscopy for organic functional group characterization of the
polar organic fraction of the aerosol. AMS and NMR spectra were processed
separately by non-negative factorization algorithms, in order to apportion
the main components underlying the submicrometer organic aerosol composition
and depict them in terms of both mass fragmentation patterns and functional
group compositions.
The NMR results supported the AMS speciation of oxidized organic aerosol
(OOA) into two main fractions, which could be generally labelled as more and
less oxidized organics. The more oxidized component was characterized by a
mass spectrum dominated by the m/z 44 peak, and in parallel by a NMR
spectrum showing aromatic and aliphatic backbones highly substituted with
oxygenated functional groups (carbonyls/carboxyls and hydroxyls). Such
component, contributing on average 50% of the OA mass throughout the
observing period, was associated with pollution outbreaks from the Central
Europe. The less oxidized component was enhanced in concomitance with air
masses originating from the North-to-West sector, in agreement with previous
investigations conducted at this site. NMR factor analysis was able to
separate two distinct components under the less oxidized fraction of OA. One
of these NMR-factors was associated with the formation of terrestrial
biogenic secondary organic aerosol (BSOA), based on the comparison with
spectral profiles obtained from laboratory experiments of terpenes
photo-oxidation. The second NMR factor associated with western air masses
was linked to biogenic marine sources, and was enriched in low-molecular
weight aliphatic amines. Such findings provide evidence of at least two
independent sources originating biogenic organic aerosols in
Hyytiälä by oxidation and condensation mechanisms: reactive terpenes
emitted by the boreal forest and compounds of marine origin, with the latter
relatively more important when predominantly polar air masses reach the
site.
This study is an example of how spectroscopic techniques, such as proton
NMR, can add functional group specificity for certain chemical features
(like aromatics) of OA with respect to AMS. They can therefore be profitably
exploited to complement aerosol mass spectrometric measurements in organic
source apportionment studies. |
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