Summary. Heterogeneous Chemistry and Atmospheric Ice
The overall objective of the joint project is to elucidate the role of certain heterogeneous processes on the surface of water ice relevant to low-temperature atmospheric chemistry. The results of this study are expected to explain, in part, the failure of gas-phase chemistry alone to account for the ozone losses over Polar Regions, to elucidate the role of water ice in the air purification in upper troposphere and to provide data for surface chemistry and photochemistry on interstellar dust particles.
The specific objectives include:
1. Development of a new experimental technique for the study of the interaction of active halogen species with surfaces typical for atmospheric aerosols.
2. Study of the kinetics of trapping of Br/Cl and BrOx/ClOx by surface water ice;
3. Analysis of the products of the heterogeneous reactions Br/Cl and BrOx/ClOx in the presence of the abundant stratospheric species such as O, O3, NO, NO3, etc. The kinetics of their gas-phase reactions will also be studied.
4. Measurements of uptake coefficient and the products of the reactions of Br/Cl, BrO/ClO and BrO2 radicals on surface water ice supported on the mineral dust.
5. Measurements of products of the temperature-programmed desorption of halogen containing radicals on the surface water ice supported on the mineral dust.
6. Determination of the surface properties of water ice by IR spectroscopy; mechanism of adsorption at low temperatures (-60 - 270 K); chemical and photochemical reactions of different organic and inorganic molecules with the surface of ice films.
7. Development of mechanisms for inclusion in models of heterogeneous and gas phase reactions of various molecules and radicals appropriate to atmospheric conditions.
Four teams from Cork, Vienna, Moscow, and Saint Petersbug will join in this study, applying complementary experimental techniques: mass spectrometry, IR spectroscopy, a Knudsen cell, X-ray diffraction (XRD) studies and temperature programmed desorption (TPD).
New experimental techniques for the study of heterogeneous processes: DF/MBMS, TDMS, and low temperature IR cells will be developed.
Surface intermediates of ozone interaction with the species formed as a result of adsorption of halogen-containing molecules (CH3Br, CHF3, HBr, HCl, C2HxF(4-x), etc.,) and radicals (Br, BrO or BrO2) on disperse ice and their transformations as a function of temperature increase will be studied.
Database containing quality controlled uptake, kinetic and mechanistic data plus IR spectroscopy data. The database will provide input for modelling atmospheric heterogeneous processes and be available on the web through links to the project web-site.
The experimental and theoretical studies on the heterogeneous chemistry and atmospheric ice will lead to a most complete description of the elementary atmospheric processes on the ice surfaces.
198504 St. Petersburg