[Zurück]

J. Ofner, C. Zetsch, B. Lendl:
"2D correlation spectroscopy of atmospheric reactions, measured with an aerosol flow-reactor in the mid infrared spectral region";
Poster: 2DCOS-7, Seoul; 21.08.2013 - 24.08.2013.

Mechanistic details on atmospheric reactions of reactive halogen species (RHS) with organic compounds are still poorly known. The reaction of RHS with typical precursors of secondary organic aerosol (SOA) like terpenes forms so-called halogen-induced organic aerosol (XOA). On the other hand, RHS are also able to change the composition of functional groups, e.g. to initiate the decarboxylation of carboxylic acids1. A detailed understanding of these reactions is important to understand and model the global impact of the reactivity of RHS with organic species on radiativ forcing, global warming and various other physico-chemical properties of the troposphere.
The present study uses a 50 cm aerosol flow-reactor2, equipped with a solar simulator to investigate the time-resolved evolution and transformation of vibrational features in the mid-infrared region. The aerosol flow-reactor is coupled to a home-made multi-reflection cell3, integrated into a Bruker IFS 113v FTIR spectrometer. The reactor is operated with an inlet feed (organic compound) and a surrounding feed (reactive halogen species). The moveable inlet of the flow reactor allows us to vary reaction times between a few seconds and up to about 3 minutes. Saturated vapours of different SOA precursors and carboxylic acids were fed into the flow reactor and mixed with molecular chlorine as a source for RHS.
Synchronous and asynchronous 2D correlation spectroscopy4,5 was applied to the time-resolved dataset to obtain a mechanistic picture. Single reaction steps of XOA formation and decarboxylation of carboxylic acids could be clarified.
1. J. Ofner, N. Balzer, J. Buxmann, H. Grothe, P. Schmitt-Kopplin, U. Platt, and C. Zetzsch, Atmos. Chem. Phys., 2012, 12, 5787-5806.
2. J. Ofner, H.-U. Krüger, and C. Zetzsch, Zeitschrift für Physikalische Chemie, 2010, 224, 1171-1183.
3. J. Ofner, H.-U. Krüger, and C. Zetzsch, Applied Optics, 2010, 49, 5001.
4. I. Noda, A. Dowrey, and C. Marcott, Appl. Spectrosc, 2000, 54, 236A-248A.
5. B. Muik, B. Lendl, A. Molina-Diaz, M. Valcarcel, and M. J. Ayora-Cañada, Analytica chimica acta, 2007, 593, 54-67.