Monday, 15 January 2007
Linking chemical changes in soot and polyaromatics to cloud droplet formation
Exhibit Hall C (Henry B. Gonzalez Convention Center)
Enhanced levels of products of incomplete combustion, including soot, polycyclic aromatic hydrocarbons (PAHs), and other organics cause reductions in urban air quality, increased levels of absorbing aerosols, and may increase concentrations of cloud condensation nuclei (CCN). When first introduced into the atmosphere, soot is a hydrophobic substance. As soot encounters oxidizing agents in the atmosphere, such as ozone, the soot may become hydrophilic, and subsequently take up water and form CCN . Likewise, other products of incomplete combustion may be oxidized by ozone. Soot samples are generated in the lab using different fuel sources such as diesel and propane. Studies on polycyclic aromatic hydrocarbons such as pyrene, naphthalene, and anthracene are also underway. The goal of our study is to identify the chemical changes in these substances, i.e., the formation of hydrophilic functional groups on the sample surfaces as the surfaces are exposed to ozone. Using a Fourier Transform Infrared (FTIR) Spectrometer equipped with a Horizontal Attenuated Total Reflectance (HATR) accessory, we observe the chemical changes occurring at the surface as it is exposed to ozone. In addition, deliquescence studies on the fresh and exposed samples are conducted using an Environmental Scanning Electron Microscope (ESEM). Experimental results will be presented and atmospheric implications discussed.