Environ. Sci. Technol. 2010, 44, 8134–8139
Secondary Organic Aerosol from Photooxidation of Polycyclic Aromatic Hydrocarbons KABINDRA M. SHAKYA AND ROBERT J. GRIFFIN* Department of Civil and Environmental Engineering, Rice University, 6100 Main St., Houston, Texas 77005, United States Climate Change Research Center, University of New Hampshire, Durham, New Hampshire 03824, United States
Received June 8, 2010. Revised manuscript received September 10, 2010. Accepted September 21, 2010.
emission sources are coal, oil, gas, wood, tobacco, and refuse combustion and domestic heating (5, 6). Naphthalene, 1and 2-methylnaphthalene, acenaphthylene, and acenaphthene are often the dominant PAHs found in an urban environment (7, 8), and their gas-phase oxidation forms products, some toxic, that partition into the aerosol phase (9–15). A large fraction of photooxidation products from PAHs are reported to form SOA in chamber experiments (10, 11). PAHs could contribute an important fraction of urban SOA based on using phthalic acid and 4-nitro-1-naphthol as naphthalene SOA tracers (13). Conventionally, SOA formation has been described by a dimensionless fractional aerosol yield, Y (16), defined as the ratio of the mass concentration of SOA formed (∆M) to the mass concentration of ROG consumed (∆ROG): Y)
Secondary organic aerosol (SOA) formation from the photooxidation of five polycyclic aromatic hydrocarbons (PAHs, naphthalene, 1- and 2-methylnaphthalene, acenaphthylene, and acenaphthene) was investigated in a 9-m3 chamber in the presence of nitrogen oxides and the absence of seed aerosols. Aerosol size distributions and PAH decay were monitored by a scanning mobility particle sizer and a gas chromatograph with a flame ionization detector. Over a wide range of conditions, the aerosol yields for the investigated PAHs were observed to be in the range of 2-22%. The observed evolution of aerosol and PAH decay indicate that light and oxidant sources influence the time required to form aerosol and the required threshold reacted concentration of the PAHs. The SOA yields also were related to this induction period and the hydroxyl radical concentrations, particularly for smaller aerosol loadings (
