Atmospheric Chemistry of Low Volatility Organic Compounds

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The objective of the proposed research is to improve the understanding of the chemical and microphysical properties of atmospheric organic aerosols. These aerosols play important roles in the atmosphere: their impacts range from human health effects in urban and regional air pollution to scattering of solar radiation in climate change.The work proposed here is designed to provide quantitative measurements on heterogeneous chemical processes involving prototype low volatility organic compounds. The technique to be employed utilizes a low pressure flow tube with a moveable injector coupled to a chemical ionization mass spectrometer for analysis of gaseous reactants and products; the low volatility organic reactants will be deposited as films on the flow tube surface. The composition of the films will be monitored by infrared and/or Raman spectroscopy.Specific projects to be carried out include investigations of the reactions of the low volatility organic species with OH, O2, NO and NO2, to be injected into the flow tube sequentially and/or simultaneously. The organic species to be studied are alkanes, polycyclic aromatic hydrocarbons (PAHs) and acids. The reaction of isoprenoids with ozone will also be studied. The hygroscopic behavior of the organic films will be investigated before and after exposure to the various gaseous reactants by monitoring the uptake of water vapor. Furthermore, the adsorption properties of the various types of organic compounds under study will be investigated on several different substrates.