AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
SOA Formation from Photooxidation of Individual PAHs and Mixtures
CHIA-LI CHEN, Mary Kacarab, Ping Tang, David R. Cocker III, University of California, Riverside
Abstract Number: 280 Working Group: Aerosol Chemistry
Abstract Polycyclic aromatic hydrocarbons (PAHs) play a significant role in semivolatile gas-phase emissions from anthropogenic sources, which include incomplete combustion emissions from spark and compression ignition engines, wood-burning, and cooking, and may be a major “missing” source of SOA. Individual PAHs SOA experiments such as naphthalene and methylnaphthalene were conducted at the UCR CE-CERT environmental chamber and compared to previous researchers. Measurements were made with a suite of instrumentation that includes a HR-ToF-AMS, VTDMA, and APM-SMPS to comprehensively understand the chemical composition characteristics, volatility and density of particles. Our results show that the SOA yield from PAHs is large and that the f44 and O/C increases with irradiation time. However, in the ambient atmosphere, there are numerous chemical compounds simultaneously reacting. Therefore, the sensitivity of SOA formation to varying HC mixtures is further explored. Serial mixtures of PAHs photooxidation experiments were conducted. Mixtures include naphthalene, 1-methylnapthalene, 2-methylnaphtalene with m-xylene, alpha-pinene, and/or the surrogate mixture used for the Carter O$_3 reactivity scales. The mixture SOA yield was evaluated by combining the SOA yield of PAHs and the SOA yield of m-xylene or other select compounds. Preliminary results show that the SOA formation from m-xylene and naphthalene mixture photooxidation was found to be suppressed by m-xylene, and the volatility measured as volume remaining fraction (VRF) of the m-xylene and naphthalene mixture increases from 0.2 to 0.4, which indicates the volatility of mixture SOA is dominated by m-xylene SOA. We expect that adding gas-phase and SOA formation from PAHs into the PM-SAPRC will allow for more accurate prediction of SOA formation from the aromatic-PAH mixtures by accounting for changes in the gas-phase chemical reactivity created by mixing the precursors together.