ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-5-3423-2005 Kinetics and mechanism of the uptake of N<sub>2</sub>O<sub>5</sub> on mineral dust at 298 K Seisel S. 1 Börensen C. 2 Vogt R. 2 Zellner R. 1 Institute for Physical and Theoretical Chemistry, University of Duisburg-Essen, Germany Ford Forschungszentrum Aachen, Aachen, Germany 19 12 2005 5 12 3423 3432 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/5/3423/2005/acp-5-3423-2005.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/5/3423/2005/acp-5-3423-2005.pdf

The heterogeneous reaction of N<sub>2</sub>O<sub>5</sub> with mineral (Saharan) dust has been studied at T=298 K using a combination of Knudsen and DRIFTS cells for kinetic and product investigations, respectively. The initial uptake coefficient has been determined to be &gamma;=(8.0&plusmn;0.3)&middot;10<sup>&minus;2</sup>. This uptake slowly saturates into a steady state uptake of &gamma;=(1.3&plusmn;0.3)&middot;10<sup>&minus;2</sup> suggesting that reaction of N<sub>2</sub>O<sub>5</sub> with the mineral dust surface and hydrolysis of N<sub>2</sub>O<sub>5</sub> on the surface take place simultaneously. Both uptake coefficients have been calculated on the basis of the geometric (projected) surface area of the sample and must therefore be regarded as upper limits. In addition, the product investigations show that N<sub>2</sub>O<sub>5</sub> is irreversibly taken up to form nitrate on the surface. Recent model calculations suggest that the uptake rates of N<sub>2</sub>O<sub>5</sub> on Saharan dust which we measured may be large enough to influence the photo-oxidant budget of the atmosphere.