 |
| Titel |
Complex chemical composition of colored surface films formed from reactions of propanal in sulfuric acid at upper troposphere/lower stratosphere aerosol acidities |
| VerfasserIn |
A. L. Van Wyngarden, S. Pérez-Montaño, J. V. H. Bui, E. S. W. Li, T. E. Nelson, K. T. Ha, L. Leong, L. T. Iraci |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 8 ; Nr. 15, no. 8 (2015-04-24), S.4225-4239 |
| Datensatznummer |
250119662
|
| Publikation (Nr.) |
 copernicus.org/acp-15-4225-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| Particles in the upper troposphere and lower stratosphere (UT/LS) consist
mostly of concentrated sulfuric acid (40–80 wt%) in water. However,
airborne measurements have shown that these particles also contain a
significant fraction of organic compounds of unknown chemical composition.
Acid-catalyzed reactions of carbonyl species are believed to be responsible
for significant transfer of gas phase organic species into tropospheric
aerosols and are potentially more important at the high acidities
characteristic of UT/LS particles. In this study, experiments combining
sulfuric acid (H2SO4) with propanal and with mixtures of propanal
with glyoxal and/or methylglyoxal at acidities typical of UT/LS aerosols
produced highly colored surface films (and solutions) that may have
implications for aerosol properties. In order to identify the chemical
processes responsible for the formation of the surface films, attenuated
total reflectance–Fourier transform infrared (ATR-FTIR) and 1H nuclear magnetic
resonance (NMR) spectroscopies were used to analyze the chemical composition of the
films. Films formed from propanal were a complex mixture of aldol
condensation products, acetals and propanal itself. The major aldol
condensation products were the dimer (2-methyl-2-pentenal) and
1,3,5-trimethylbenzene that was formed by cyclization of the linear aldol
condensation trimer. Additionally, the strong visible absorption of the films
indicates that higher-order aldol condensation products must also be present
as minor species. The major acetal species were
2,4,6-triethyl-1,3,5-trioxane
and longer-chain linear polyacetals which are likely to separate from the
aqueous phase. Films formed on mixtures of propanal with glyoxal and/or
methylglyoxal also showed evidence of products of cross-reactions. Since
cross-reactions would be more likely than self-reactions under atmospheric
conditions, similar reactions of aldehydes like propanal with common aerosol
organic species like glyoxal and methylglyoxal have the potential to produce
significant organic aerosol mass and therefore could potentially impact
chemical, optical and/or cloud-forming properties of aerosols, especially if
the products partition to the aerosol surface. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|