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A smog chamber study on the impact of aerosols on the photodegradation of chemicals in the troposphere

 
: Nolting, F.; Zetzsch, C.; Behnke, W.

Journal of Aerosol Science 18 (1987), Nr.1, S.65-71
ISSN: 0021-8502
Englisch
Zeitschriftenaufsatz
Fraunhofer ITA ( ITEM) ()
adsorption; aerosol; Alkan; Anatas; Aromat; Cycloalkan; Halbleiter; Hydroxylradikal; Kohlenwasserstoff; Photoabbau(heterogen); Smogkammer; TiO2; Titandioxid

Abstract
In the smog chamber the photodegradation of organic compounds (gases and vapours) is observed to be dominated by OH radicals, and rate constants for the reaction of OH with n-alkanes from propane to n-nonane are determined from the simultaneous decay of the hydrocarbons. The presence of SiO2 aerosol at densities up to 4 mg m -3 does not affect the concentration of OH. In the presence of TiO2 aerosol the concentration of OH is increased by one of magnitude to 10 8cm-3. In addition a heterogeneous photodegradation of various alkanes, cycloalkanes, branched-chain alkanes and benzene-aromatics occurs inversely proportional to the vapour pressure. As expected for a heterogeneous process the data can be correlated with gas chromatographic retention times on a column, packed with TiO2. The impact of these processes (which may be due to the formation of OH on the surface of the u.v. absorbing semi-conductor, TiO2) on the chemistry of the troposphere is discussed. (ITA)

: http://publica.fraunhofer.de/dokumente/PX-34011.html