[Zurück]

J. Ofner, H.-U. Krüger, H. Grothe, C. Zetzsch:
"Spectroscopy and electron microscopy of nanostructured particles from nucleation by oxidation of phenols as a model for atmospheric HULIS";
Poster: 109. Hauptversammlung der Deutschen Bunsen-Gesellschaft für Physikalische Chemie, Bielefeld, Germany; 13.05.2010 - 15.05.2010; in: "Interfacial Systems Chemistry: Out of the Vacuum, Through the Liquid, Into the Cell", (2010), S. 292.

The Earth's atmosphere, considered as a large photochemical reactor, forms secondary organic aerosol (SOA) particles by abiotic oxidation and gas-to-particle conversation of volatile organic compounds originating from biogenic emissions. So-called HUmic LIke Substances (HULlS) have attracted attention in atmospheric science only recently, initiating a discourse about their aromaticity and surface properties. Thus, aerosol smog-chamber studies with appropriate precursors have been employed to generate SOA with natural HULIS properties in situ inside the simulation chamber. Catechol and guaiacol were chosen as model substances for, emissions from plants and forest fires and as intermediates for formation of SOA. The SOA was produced in a 700 L aerosol smog chamber, equipped with a solar simulator. SOA formation from each precursor was investigated at simulated, environmental conditions (humidity, light, and presence of oxidizers) and characterized with respect to HULIS properties by particle classifiers, long-path-FTIR, ATR-FTIR, UVNIS spectroscopy and temperature-programmed-desorption mass spectrometry
(TPD-MS). High-resolution imaging was obtained using FEG-SEM. These laboratory-scale measurements provide evidence that gaseous organic precursors form monodisperse primary organic carbon particles (HULlS) of 20nm size, agglomerating to larger aggregates. However, sunlight and relative humidity play a crucial role in the particle production and influence the composition of surface functional groups, which are the anchor points for heterogeneous atmospheric chemistry.