From the Smog Chamber to the 2D-VBS Parameterization of Secondary Organic Aerosol Formation

DAMIANOS PAVLIDIS, Petro Uruci, Angeliki Matrali, Spyros Ν. Pandis, University of Patras Greece

     Abstract Number: 183
     Working Group: Aerosol Chemistry

Abstract
A new measurement approach during smog chamber experiments is developed to facilitate the translation of the corresponding results to secondary organic aerosol (SOA) parameterizations that can be used in atmospheric chemical transport models (CMTs). The SOA concentration and composition is measured, at both ambient conditions and after heating with a thermodenuder at a range of temperatures, using a high-resolution proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) coupled to a CHARON inlet (Ionicon Analytik Inc.), a high-resolution time of flight aerosol mass spectrometer (HR-ToF-AMS) and an SMPS. At the same time the SOA is isothermally diluted in a second chamber to better constrain its volatility distribution. The gas-phase composition is also measured by the PTR-ToF-MS. The combined measurements are then used for the parameterization of the results both in the 2D- and the 1D-Volatility Basis Set frameworks (VBS).

The system was applied for the study of the SOA produced during the oxidation of large anthropogenic volatile (VOCs) and intermediate volatility organic compounds (IVOCs) by hydroxyl radicals, under high NOx conditions. The precursors used include aromatic compounds of increasing size (1,3,5-trimethylbenzene, 1,3,5-triethylbenzene and 1,3,5-tri-tert-butylbenzene) and cyclic alkanes (amylcyclohexane, hexylcyclohexane, nonylcyclohexane and decylcyclohexane). A significant quantity of SOA originated from all compounds investigated. While the large cyclohexanes exhibited higher yields compared to the aromatic compounds, the aromatic precursors generated more oxidized SOA. Most oxidation products of the cyclohexanes were semivolatile organics, while of the aromatics are IVOCs.