Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 2 4 2002 10.5194/acpd-2-983-2002 http://www.atmos-chem-phys-discuss.net/2/983/2002/ http://www.atmos-chem-phys-discuss.net/2/983/2002/acpd-2-983-2002.html http://www.atmos-chem-phys-discuss.net/2/983/2002/acpd-2-983-2002.pdf 983 998 2002-07-15 Suppression of chlorine activation on aviation-produced volatile particles S. K. Meilinger B. Kärcher Th. Peter MPI für Chemie, Mainz, Germany DLR Oberpfaffenhofen, Institut für Physik der Atmosphäre, Wessling, Germany ETH Laboratorium für Atmosphärenphysik, Zürich, Switzerland We examine the effect of nm-sized aircraft-induced aqueous sulfuric acid (H<sub>2</sub>SO<sub>4</sub>/H<sub>2</sub>O) particles on atmospheric ozone as a function of temperature. Our calculations are based on a previously derived parameterization for the regional-scale perturbations of the sulfate surface area density due to air traffic in the North Atlantic Flight Corridor (NAFC) and a chemical box model. We confirm large scale model results that at temperatures T &gt; 210 K additional ozone loss -- mainly caused by hydrolysis of BrONO<sub>2</sub> and N<sub>2</sub>O<sub>5</sub> -- scales in proportion with the aviation-produced increase of the background aerosol surface area. However, at lower temperatures (&lt; 210 K) we isolate two effects which efficiently reduce the aircraft-induced perturbation: (1) background particles growth due to H<sub>2</sub>O and HNO<sub>3</sub> uptake enhance scavenging losses of aviation-produced liquid particles and (2) the Kelvin effect efficiently limits chlorine activation on the small aircraft-induced droplets by reducing the solubility of chemically reacting species. These two effects lead to a substantial reduction of heterogeneous chemistry on aircraft-induced volatile aerosols under cold conditions. In contrast we find contrail ice particles to be potentially important for heterogeneous chlorine activation and ozone depletion. These features have not been taken into consideration in previous global studies of the atmospheric impact of aviation. Therefore, to parameterize them in global chemistry and transport models, we propose the following parameterisation: scale the hydrolysis reactions by the aircraft-induced surface area increase, and neglect heterogeneous chlorine reactions on liquid plume particles but not on ice contrails and aircraft induced ice clouds.