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:

Although PM2.5 can be directly introduced into the atmosphere through primary emissions, its mass concentration is also strongly affected by secondary processes such as nucleation or condensation of nonvolatile and semivolatile compounds on pre-existing aerosols. Chemical modules based on accurate representations of the key chemical processes that determine the contributions of secondary processes to the overall mass concentrations of PM2.5 are required to evaluate strategies for reducing exposure levels. Because only about 10% of the organic compounds in ambient aerosols has been identified, research is needed to identify the remaining organic compounds, some of which are likely to be multi-functional highly oxygenated reactive compounds. The focus of the task is to develop the chemical information necessary to build chemical modules for predicting ambient concentrations of secondary organic aerosols. Chamber studies will be carried out to investigate aerosol formation under real world concentration conditions. Emphasis will be placed on addressing important issues identified by the National Research Council including (1) determining the yields of atmospherically relevant hydrocarbons under near ambient concentrations over a range of relative humidities and (2) identifying organic multifunctional oxygenates in PM2.5. This information, which constituted FY00 GPRA APM 443, will be used to develop a first generation chemical module for predicting PM2.5 concentrations. The module will be evaluated and refined under a follow on task to develop a secondary organic aerosol module in FY04

Record Details:

Record Type:PROJECT

Start Date:10/01/1998

Completion Date:09/01/2001

Record ID: 56141

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Project Information:

Progress :A series of laboratory chamber experiments were conducted at near ambient levels and real world relative humidity conditions to determine the SOA yields of biogenic hydrocarbons. A short term field study was also completed to determine if the newly identified multi-functional oxygenates found in the chamber studies could be observed in the ambient PM2.5 samples. A number of articles and presentations have resulted from this work, as described below. These documents comprised APG 004 / APM 443 for FY00.

ABSTRACT/ORAL: Date Cleared :10-DEC-99

Edney, E.O., Swartz, E.C., Driscoll, D.J., Kleindienst, T.E., Li, W., Conver, T.S., and McIver, C.D. EPA PM chemistry studies: Smog chamber studies of secondary organic aerosols from irradiated hydrocarbons under ambient conditions. American Geophysical Union Fall Meeting 1999, San Francisco, CA, December 11-17, 1999.

ABSTRACT/ORAL: Date Cleared: 01-MAR-00

Conver, T.S., Kleindienst, T.E., Li, W., McIver, C.D., Corse, E.W., and E.O. Edney. SOA yields and organic product distribution from natural hydrocarbon/NOx irradiations. Abstract presented at: 19th Annual AAA Conference, St. Louis, MO, November 6-10, 2000.

JOURNAL ARTICLE: Date Cleared: 26-MAY-99

Kleindienst, T.E., D.F. Smith, W. Li, E.O. Edney, D.J. Driscoll, R.E. Speer, and W.S. Weathers. Secondary organic aerosol formation from the oxidation of aromatic hydrocarbons in the presence of dry submicron ammonium sulfate aerosol. Atmospheric Environment, 33, 3669, 1999.

JOURNAL ARTICLE: Date Cleared: 30-MAY-00

Edney, E.O., Driscoll, D.J., Speer, R.E., Weathers, W.S., Kleindienst, T.E., Li, W., and D.F. Smith. Impact of aerosol liquid water on secondary organic aerosol yields of irradiated toluene/propylene/NOx(NH4)2SO4/air mixtures. Atmospheric Environment 34:3907, 2000.

JOURNAL ARTICLE: Date Cleared:

Edney, E.O., D.J. Driscoll, W.S. Weathers, T.E. Kleindienst, T.S. Conver, W. Li, and C.D. McIver. Formation of polyketones in irradiated toluene/propylene/NOx/air mixtures. Aerosol Science and Technology (submitted) 2000.

JOURNAL ARTICLE: Date Cleared:

Kleindienst, T.E., D.F. Smith, W. Li, E.O. Edney, D.J. Driscoll, R.E. Speer, and W.S. Weathers. Secondary organic aerosol formation from the irradiation of simulated automobile exhaust. Journal of Air and Waste Management Association (submitted) 2000.

EPA Report: Date Cleared:

Edney, E.O., D.J. Driscoll, W.S. Weathers, T.E. Kleindienst, T.S. Conver, W. Li, and C.D. McIver. APM 443 Report: Atmospheric Chemistry of Secondary Organic Aerosol Formation. 2000.



Relevance :The laboratory results clearly demonstrate emissions of aromatic and biogenic hydrocarbons compounds followed by reactions with OH and O3 form oxidation products that increase the mass of organic constituents in PM2.5 by nucleation reactions and condensation onto pre-existing aerosol. The results of the smog chamber experiments have also been used to identify a large number of secondary organic aerosol compounds that contribute to the mass loading of PM2.5. Additional studies have shown that secondary organic aerosol formation of aromatic compounds is not affected significantly by relative humidity. These data along with results obtained in FY01 will serve as the foundation for developing a first generation chemical module for predicting SOA yields from oxidation of biogenics and aromatics. The preliminary module will be evaluated and expanded to predict SOA yields and chemical compositions from photooxidation of atmospheric relevant hydrocarbon mixtures typical of rural, suburban and urban conditions under a follow on task to begin in FY02

Clients :OAQPS, National Research Council

Project IDs:

ID Code :3897

Project type :OMIS