EVOLUTION OF THE CONCENTRATIONS OF TRACE SPECIES IN AN AIRCRAFT PLUME - TRAJECTORY STUDY

Permanent increase of the subsonic aviation flights and attempts to develop high-speed civil transport (HSCT) necessitate an assessment of their possible environmental impacts. To evaluate global aviation effects, it is important to know the role of the chemical transformations inside an aircraft plume taking into account heterogeneous reactions. The goad of this work is to model the principal physical and chemical processes occurring inside as aircraft exhaust plume. A new box model which calculates 41 relevant O-x, HOx, NOx, ClOx, BrOx, SOx, and HC species and includes the possible heterogeneous reactions on the combustion aerosol and ice contrail particles is proposed. The simplified descriptions of the aircraft plume dilution and ice contrail formation are described. The transformations inside the aircraft wake are presented for the trajectories of the exhaust product motions st the levels of 200 and 100 mbar calculated for the particular atmospheric conditions on April 25, 1986. The following problems are discussed: the ozone response at these altitudes, the oxidation rate of NOx and SO2, the role of the heterogeneous reactions on the combustion aerosol and contrail particles, and the possibility of ice and nitric acid trihydrate (NAT or HNO3,3H(2)O) particle formation inside the wake. The model results are in agreement with available experimental data for NO, NO2, HNO3, HNO2, and SO2. Analytical expressions are proposed to evaluate the oxidation rates of NOx and SO2 in the aircraft wake. The local ozone response is small (between 0.6% at 200 mb and -0.1% at 100 mb). Possible future investigations are proposed.