Grant: Research Tools and Instruments - Category 1 (<$150,000)

The formation of secondary organic aerosols is a major source of particulate matter (such as smog) in the atmosphere. Secondary organic aerosols are generated by the oxidation of volatile organic compounds and can affect visibility, climate, and human and ecological health. We have recently constructed a photoreaction chamber (""smog chamber"") to simulate atmospheric conditions and to study the reactions that lead to aerosol formation. A unique feature of our instrument is the availability of a mid-infrared semiconductor laser based trace gas sensing system. This sensor allows us to monitor the concentrations of reactants, for example, BTEX compounds (benzene, toluene, ethylbenzene, xylene) in real time. We have also succeeded in detecting product species during the ultra-violet light induced oxidation reactions. We are proposing now to apply this powerful method to the study of more complex precursor mixtures, to better simulate real atmospheric conditions. A detailed interpretation of the collected data, in particular an identification of reaction products, requires careful theoretical modeling. Aerosol particle size and surface area are important input data for these modeling studies. Currently, our instrument does not have the capability to collect these crucial data and we are therefore unable to fully interpret the results from our experiments. The availability of a scanning mobility particle sizer would greatly enhance our capabilities and would allow us to make significant contributions to the area of atmospheric aerosol chemistry. Funds are requested for the purchase of a scanning mobility particle sizer.