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| Titel |
Ultraviolet and visible complex refractive indices of secondary organic material produced by photooxidation of the aromatic compounds toluene and m-xylene |
| VerfasserIn |
P. F. Liu, N. Abdelmalki, H.-M. Hung, Y. Wang, W. H. Brune, S. T. Martin |
| 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 ; 15, no. 3 ; Nr. 15, no. 3 (2015-02-10), S.1435-1446 |
| Datensatznummer |
250119400
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| Publikation (Nr.) |
 copernicus.org/acp-15-1435-2015.pdf |
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| Zusammenfassung |
| Secondary organic material (SOM) produced by the oxidation of anthropogenic
volatile organic compounds can be light-absorbing (i.e., brown carbon).
Spectral data of the optical properties, however, are scarce. The present
study obtained the continuous spectra of the real and imaginary refractive
indices (m = n-i k) in the ultraviolet (UV)-to-visible region using
spectroscopic ellipsometry for n and UV–visible spectrometry for k. Several
different types of SOM were produced in an oxidation flow reactor by
photooxidation of toluene and m-xylene for variable concentrations of
nitrogen oxides (NOx). The results show that the k values of the
anthropogenically derived material were at least 10 times greater than
those of the biogenically derived material. The presence of NOx was
associated with the production of organonitrogen compounds, such as
nitro-aromatics and organonitrates, which enhanced light absorption.
Compared with the SOM derived from m-xylene, the toluene-derived SOM had
larger k values, as well as a greater NOx-induced enhancement,
suggesting different brown-carbon-forming potentials of different aromatic
precursor compounds. The results imply that anthropogenic SOM produced
around urban environments can have an important influence on ultraviolet
irradiance, which might consequently influence photochemical cycles of urban
pollution. |
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