HR: 1330h
AN: A32B-0138    [PDF]
TI: Ozone Decomposition Kinetics on Aluminum Oxide: Effects of Relative Humidity, Ozone Partial Pressure and the State of Film Oxidation
AU: * Sullivan, R C
EM: ryans@sympatico.ca
AF: Department of Chemistry, University of Toronto, Lash Miller Chemical Laboratories, Toronto, ON M5S 3H6 Canada
AU: Thornberry, T D
EM: tthornbe@chem.utoronto.ca
AF: Department of Chemistry, University of Toronto, Lash Miller Chemical Laboratories, Toronto, ON M5S 3H6 Canada
AU: Abbatt, J P
EM: jabbatt@chem.utoronto.ca
AF: Department of Chemistry, University of Toronto, Lash Miller Chemical Laboratories, Toronto, ON M5S 3H6 Canada
AB: To investigate the role that mineral dust plays in affecting the concentrations of trace gases in the troposphere, the kinetics of ozone decomposition on aluminum oxide surfaces were studied at room temperature in a static ozone absorption chamber. The rate of ozone destruction was first order on fresh films but decreased with extent of ozone exposure. Passivation of the alumina surfaces was also observed if the films were not kept in a dry, purged environment. A linear relationship between the film specific surface area (measured by gas adsorption) and film mass was found which allowed us to use the mass of the film to normalize our uptake coefficients to the actual surface area of each sample. The initial rate of ozone destruction increased linearly with alumina mass, indicating full accessibility to the gas phase, and it increased with decreasing ozone partial pressure. In particular, the ozone concentration was varied from 8 x10$^{12}$ to 1 x10$^{14}$ molecules cm$^{-3}$, over which $\gamma_{initial}$ ranged from 1.5 x10$^{-5}$ to 1.0 x10$^{-6}$. By repeatedly oxidizing the surface until passivated a surface site concentration was estimated to be 2 x10$^{14}$ sites cm$^{-2}$. Oxidations of alumina were conducted as a function of relative humidity by adding water vapour and ozone simultaneously to the chamber. The presence of water vapour dramatically reduced $\gamma_{initial}$ by up to 80% at 75% RH. Our results highlight the need to consider the oxidation and hydration state of the mineral dust surface when investigating the impact that heterogeneous chemistry on mineral dust may have in the atmosphere.
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0305 Aerosols and particles (0345, 4801)
DE: 0317 Chemical kinetic and photochemical properties
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting