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Environ Sci Technol

Title:		Photo-oxidation of low-volatility organics found in motor vehicle emissions: production and chemical evolution of organic aerosol mass
Author(s):		Miracolo MA; Presto AA; Lambe AT; Hennigan CJ; Donahue NM; Kroll JH; Worsnop DR; Robinson AL;
Address:		"Departments of Mechanical Engineering and Chemical Engineering and Center for Atmospheric Particle Studies, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA"
Journal Title:		Environ Sci Technol
Year:		2010
Volume:		44
Issue:		5
Page Number:		1638 - 1643
DOI:		10.1021/es902635c
ISSN/ISBN:		0013-936X (Print) 0013-936X (Linking)
Abstract:		"Recent research has proposed that low-volatility organic vapors are an important class of secondary organic aerosol (SOA) precursors. Mixtures of low-volatility organics were photo-oxidized in a smog chamber under low- and high-NO(x) conditions. Separate experiments addressed emission surrogates (diesel fuel and motor oil) and single components (n-pentacosane). Both diesel fuel and motor oil are major components of exhaust from diesel engines. Diesel fuel is a complex mixture of intermediate volatility organic compounds (IVOCs), whereas motor oil is a complex mixture of semivolatile organic compounds (SVOCs). IVOCs exist exclusively in the vapor phase, while SVOCs exist in both the aerosol and vapor phase. Oxidation of SVOC vapors (motor oil and n-pentacosane) creates substantial SOA, but this SOA is largely offset by evaporation of primary organic aerosol (POA). The net effect is a cycling or pumping of SVOCs between the gas and particle phases, which creates more oxygenated organic aerosol (OA) but little new OA mass. Since gas-phase reactions are much faster than heterogeneous ones, the processing of SVOC vapors likely contributes to the production of highly oxidized OA. The interplay between gas-particle partitioning and chemistry also blurs traditional definitions of POA and SOA. Photo-oxidation of diesel fuel (IVOCs) rapidly creates substantial new OA mass, similar to published aging experiments with dilute diesel exhaust. However, aerosol mass spectrometer (AMS) data indicated that the SOA formed from emission surrogates is less oxidized than either the oxygenated organic aerosol (OOA) measured in the atmosphere or SOA formed from the photo-oxidation of dilute diesel exhaust. Therefore, photo-oxidation of IVOCs helps explain the substantial SOA mass produced from aging diesel exhaust, but some component is missing from these emission surrogate experiments that leads to the rapid production of highly oxygenated SOA"
Keywords:		Aerosols/*analysis Air Pollutants/analysis/*chemistry Biofuels/analysis Environmental Monitoring/methods/standards Gasoline/analysis Organic Chemicals/analysis/*chemistry Oxidation-Reduction Photochemistry Vehicle Emissions/*analysis Volatilization;
Notes:		"MedlineMiracolo, Marissa A Presto, Albert A Lambe, Andrew T Hennigan, Christopher J Donahue, Neil M Kroll, Jesse H Worsnop, Douglas R Robinson, Allen L eng Research Support, U.S. Gov't, Non-P.H.S. 2010/02/04 Environ Sci Technol. 2010 Mar 1; 44(5):1638-43. doi: 10.1021/es902635c"