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

Permanent increase of the subsonic aviation flights and attempts to de velop high-speed civil transport (HSCT) necessitate an assessment of t heir possible environmental impacts. To evaluate global aviation effec ts, it is important to know the role of the chemical transformations i nside an aircraft plume taking into account heterogeneous reactions. T he goad of this work is to model the principal physical and chemical p rocesses occurring inside as aircraft exhaust plume. A new box model w hich calculates 41 relevant O-x, HOx, NOx, ClOx, BrOx, SOx, and HC spe cies and includes the possible heterogeneous reactions on the combusti on aerosol and ice contrail. particles is proposed. The simplified des criptions of the aircraft plume dilution and ice contrail formation ar e described. The transformations inside the aircraft wake are presente d for the trajectories of tile exhaust product motions st the levels o f 200 and 100 mbar calculated for the particular atmospheric condition s on April 25, 1986. The following problems are discussed: the ozone r esponse at these altitudes, the oxidation rate of NOx and SO2, the rol e of the heterogeneous reactions on the combustion aerosol and contrai l particles, and the possibility of ice and nitric acid trihydrate (NA T or HNO3,3H(2)O) particle formation inside the wake. The model result s are in agreement with available experimental data for NO, NO2, HNO3, HNO2, and SO2. Analytical expressions are proposed to evaluate the ox idation rates of NOx and SO2 in the aircraft wake. The local ozone res ponse is small (between 0.6% at 200 mb and -0.1% at 100 mb). Possible future investigations are proposed.