AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Gas-phase Oxidation of Naphthalene, Acenaphthylene and Acenaphthene Initiated by the Nitrate Radical: Mechanistic Study and SOA Formation
MATTHIEU RIVA, Manuela Cirtog, Emilie Perraudin, Bénédicte Picquet-Varrault, Eric Villenave, EPOC, Université Bordeaux, France
Abstract Number: 617 Working Group: Aerosol Chemistry
Abstract The aerosol organic fraction constitutes a significant part of urban particulate matter and may play a major role in all air pollution processes. In the atmosphere, the main origin of organic aerosol may often arise from secondary sources. It is well-known that volatile organic compounds (VOCs) such as monoterpenes or monoaromatics are involved in the formation of secondary organic aerosols (SOA). However, the total mass of SOA measured on several sampling sites cannot be explained by the simple presence of such VOCs. Recent studies indicate that PAHs such as naphthalene, acenaphthene and acenaphthylene could be one of the "missing" sources of SOA, particularly in urban areas. NO3 radical is known to be the main oxidant of VOCs during night time. Different studies have demonstrated the large reactivity of nitrate radicals with volatile organic compounds, especially with unsaturated species. Such high reactivity of NO3 with some VOCs may lead to significant impact in the formation of SOA.
Reactions of naphthalene, acenaphthene and acenaphthylene with nitrate radicals were carried out in the CSA chamber, at room temperature and atmospheric pressure. Gas-phase products were followed in real time using both a proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS) and FTIR. A SMPS was used to measure the aerosol concentration, the size distribution and to quantify aerosol formation yields.
This work presents the first exploration of the impact of nitrate radicals on SOA arising from PAH oxidation. Kinetics measurements were also performed in order to determine the reaction rate constants of the three PAHs and the impact of NO2. Based on the gas-phase identified products, new insights on chemical mechanisms are proposed.