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SECONDARY ORGANIC AEROSOL FORMATION FROM THE IRRADIATION OF SIMULATED AUTOMOBILE EXHAUST
Citation:
Kleindienst, T. E., E. W. Corse, W. Li, C. D. McIver, T. S. Conver, E O. Edney, D J. Driscoll, R E. Speer, W S. Weathers, AND S B. Tejada. SECONDARY ORGANIC AEROSOL FORMATION FROM THE IRRADIATION OF SIMULATED AUTOMOBILE EXHAUST. JOURNAL OF THE AIR & WASTE MANAGEMENT ASSOCIATION 52(3):259-272, (2002).
Impact/Purpose:
1. Determine the secondary organic aerosol (SOA) yields of biogenic and aromatic hydrocarbons under real world concentration and relative humidity conditions.
2. Determine the organic composition of SOA from photooxidation of biogenic and aromatic compounds.
3. Measure the partitioning coefficients of atmospherically relevant semivolatile SOA.
4. Investigate the impact of the chemical composition of the organic fraction of the PM2.5 on the partitioning of SOA compounds.
5. Develop a first generation SOA chemistry module.
Description:
A laboratory study was conducted to evaluate the potential for secondary organic aerosol formation from emissions from automotive exhaust. The goal was to determine to what extent photochemical oxidation products of these hydrocarbons contribute to secondary organic aerosol (SOA) and how well their formation is described by recently developed models for SOA formation. The quality of the surrogate was tested by comparing its reactivity with that from irradiations of authentic automobile exhaust. Experiments for secondary particle formation using the surrogate were conducted in a fixed volume reactor operated in a dynamic mode. The mass concentration of the aerosol was determined from measurements of organic carbon collected on quartz filters which was corrected for the presence of hydrogen, nitrogen, and oxygen atoms in the organic species.
A functional group analysis of the aerosol made by FTIR indicated that carbonyl groups dominated the aerosol with relatively little aliphatic or aromatic C-H functionality. This result is consistent with the presence of polycarbonyl compounds measured in the aerosol. The hygroscopic potential of the aerosol was determined with the use of a liquid water content analyzer and the analysis indicated that the aerosol uptake of water was minor at relative humidities below 70%. The yield for the formation of secondary organic aerosol yield was found to be 1.8% when measured for an aerosol mass of 7.38 ug m-3. These results were compared to an aerosol model developed by Odum and co-workers and suggested that 75-85% of the fine particulate matter was due to reaction products of aromatic precursors. Organic analysis of the collected aerosol from this complex system indicates that the identified oxidation products were identical to those found in the toluene oxidation system.
The U. S. Environmental Protection Agency through its Office of Research and Development funded and collaborated in the research described here under Contract 68-D5-0049 to Man Tech Environmental Technology, Inc. It has been subject to Agency review and approved for publication. Mention of trade names or commercial products does not constitute or endorsement or recommendation for use.