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| Titel |
Aging induced changes on NEXAFS fingerprints in individual combustion particles |
| VerfasserIn |
V. Zelenay, R. Mooser, T. Tritscher, A. Křepelová, M. F. Heringa, R. Chirico, A. S. H. Prévôt, E. Weingärtner, U. Baltensperger, J. Dommen, B. Watts, J. Raabe, T. Huthwelker, M. Ammann |
| 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 ; 11, no. 22 ; Nr. 11, no. 22 (2011-11-24), S.11777-11791 |
| Datensatznummer |
250010220
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| Publikation (Nr.) |
 copernicus.org/acp-11-11777-2011.pdf |
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| Zusammenfassung |
| Soot particles can significantly influence the Earth's climate by absorbing
and scattering solar radiation as well as by acting as cloud condensation
nuclei. However, despite their environmental (as well as economic and
political) importance, the way these properties are affected by atmospheric
processing of the combustion exhaust gases is still a subject of discussion.
In this work, individual soot particles emitted from two different vehicles,
a EURO 2 transporter, a EURO 3 passenger car, and a wood stove were
investigated on a single-particle basis. The emitted exhaust, including the
particulate and the gas phase, was processed in a smog chamber with
artificial solar radiation. Single particle specimens of both unprocessed and
aged soot were characterized using near edge X-ray absorption fine structure
spectroscopy (NEXAFS) and scanning electron microscopy. Comparison of NEXAFS
spectra from the unprocessed particles and those resulting from exhaust
photooxidation in the chamber revealed changes in the carbon functional group
content. For the wood stove emissions, these changes were minor, related to
the relatively mild oxidation conditions. For the EURO 2 transporter
emissions, the most apparent change was that of carboxylic carbon from
oxidized organic compounds condensing on the primary soot particles. For the
EURO 3 car emissions oxidation of primary soot particles upon photochemical
aging has likely contributed as well. Overall, the changes in the NEXAFS
fingerprints were in qualitative agreement with data from an aerosol mass
spectrometer. Furthermore, by taking full advantage of our in situ
microreactor concept, we show that the soot particles from all three
combustion sources changed their ability to take up water under humid
conditions upon photochemical aging of the exhaust. Due to the selectivity
and sensitivity of the NEXAFS technique for the water mass, also small
amounts of water taken up into the internal voids of agglomerated particles
could be detected. Because such small amounts of water uptake do not lead to
measurable changes in particle diameter, it may remain beyond the limits of
volume growth measurements, especially for larger agglomerated particles. |
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