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(15-43) Aromatic Hydrocarbons as Source of Tropospheric Aerosols. Barnes, Ian*,1, Hoffmann, Thorsten2, 1 Bergische University Wuppertal, Physical Chemistry / FB 9, Gauss Str. 20, 42097 Wuppertal, Germany2 Institute of Spectrochemistry and Applied Spectroscopy, Bunsen-Kirchhoff-Str. 11, 44139 Dortmund ABSTRACT- Aromatic compounds are an important class of organic compounds found in particular in urban air because a major source of aromatic hydrocarbons is the car emission. Of the 32 most prevalent non-methane hydrocarbons observed in urban air, seven are aromatics with toluene being the most abundant and accounting for approximately 6% of the observed nonmethane hydrocarbon. Atmospheric oxidation of aromatic hydrocarbons is believed to contribute significantly to the organic aerosol found in polluted urban air. While it has been known for some time that the atmospheric oxidation of aromatic species leads to aerosol formation, the exact mechanism by which aerosol is formed still remains unclear. Seinfeld and co-workers have developed a gas/particle absorption model which they have used to explain SOA yield data. The essence of the gas/particle model is that the gas phase oxidation of the parent compound produces semivolatile products which partition between the gas and absorbing organic aerosol phases. It is now widely accepted that the semivolatile compounds by the aromatic hydrocarbon are secondary reaction products; however, it is unclear whether they are the result of photolysis, OH radical, O3 or NO3 radical reactions. In recent years there have been numerous new studies to investigate the extend of aerosol formation and the nature of the aerosol products from the oxidation of aromatic hydrocarbons and different mechanisms have been postulated. Studies have also been performed on the aerosol formation from individual aromatic oxidation products in order to try and pinpoint some of the important aerosol formation processes. The current knowledge on the aerosol formation from the photooxidation of aromatic hydrocarbons will be reviewed and new developments and future trends will be highlighted. Key words: atmospheric particles, gas-to-particle conversion, aromatic VOCs |
