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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.
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