9508051 Pandis Organic aerosol is an important component of ambient particulate matter, whether in urban, rural, or remote areas. Organic compounds represent on average 35% of the fine aerosol mass in urban polluted areas like Los Angeles and their sources on a global scale are estimated to be similar to those of sulfate. They are an integral part of the direct and indirect radiative forcing of climate by aerosols. Atmospheric aerosol pose significant environmental risks (health problems, visibility degradation) in part because of these organic compounds. The in-situ formation of secondary organic aerosol by condensation of low volatility products of the photooxidation of hydrocarbons remains poorly understood. This project will investigate the mass transfer of organic compounds from the gas to the aerosol phase. The equilibrium partitioning of the major organic aerosol components between the gas and aerosol phases will be studied by measuring the vapor pressures of their mixtures. The condensation rates of these organic compounds will be quantified on a variety of model inorganic and organic aerosol substrates and the accommodation coefficients calculated. The effects of the organic compounds on the evaporation rate of NH4NO3 will be determined, as well as the influence of organic films on the rate of growth of organic and inorganic aerosols. The proposed experimental system is based on the Tandem Differential Mobility Analyzer technique. The results will be incorporated into a state-of-the-art aerosol model and the model output will be tested with the best available urban air quality data set. The educational efforts of this project will focus on the development of environmental classes for engineers. A textbook in atmospheric chemistry will be developed and used for one of these classes. The application of computer technology to the education of chemical engineers will be explored. Undergraduate students will be involved in research both directly through year long senior research projects and indirectly through the Engineering and Public Policy project courses. Finally, the development of environmental modules through the Environment Across the Curriculum program of Carnegie Mellon University will contribute to the environmental education of all engineers.
