AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Investigation of SOA Composition from the Photolysis of 1-Nitronaphthalene using Single Particle Mass Spectrometry
ROBERT HEALY, Yang Chen, Ivan Kourtchev, Markus Kalberer, John Wenger, University College Cork
Abstract Number: 91 Working Group: Aerosol Chemistry
Abstract Nitro-substituted polycyclic aromatic hydrocarbons are of interest due to their associated mutagenic and carcinogenic effects. 1-nitronaphthalene is emitted directly from combustion processes such as vehicle exhaust, but is also formed through the reaction of naphthalene with the hydroxyl or nitrate radical in the presence of NOx. Photolysis has previously been demonstrated to be the major degradation pathway for 1-nitronaphthalene in the troposphere. A series of simulation chamber experiments has been performed to investigate the chemical composition of SOA formed through the direct photolysis of 1-nitronaphthalene using an Aerosol Time-Of-Flight Mass Spectrometer (ATOFMS, TSI). SOA forms rapidly with a yield of up to 50% depending on precursor concentration and photolysis rate. Along with expected products such as naphthoquinone and nitronaphthol, condensed species exhibiting mass spectra consistent with the presence of four aromatic rings were also observed. It is proposed that these species may be formed through dimerization of naphthoxy radicals generated during the photolysis process. Further evidence to support this mechanism was obtained when 1-nitronaphthalene was photolyzed in the presence of excess nitrobenzene. Dimers were then formed containing three aromatic rings, consistent with the reaction of phenoxy and naphthoxy radicals. The molecular formulae of the dimers were also confirmed by collecting SOA on filters and analysing the extracts off-line using an LTQ Orbitrap Velos mass spectrometer (Thermo-Fisher Scientific), fitted with a TriVersa NanoMate chip-based electrospray ionization source (Advion Biosystems). These findings demonstrate the advantages of single particle mass spectrometry as a tool for the investigation of SOA products in simulation chamber studies.