Abstract. The heterogeneous reaction of N 2 O 5 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 γ =(8.0±0.3)·10 −2 . This uptake slowly saturates into a steady state uptake of γ =(1.3±0.3)·10 −2 suggesting that reaction of N 2 O 5 with the mineral dust surface and hydrolysis of N 2 O 5 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 2 O 5 is irreversibly taken up to form nitrate on the surface. Recent model calculations suggest that the uptake rates of N 2 O 5 on Saharan dust which we measured may be large enough to influence the photo-oxidant budget of the atmosphere.

Abstract. The heterogeneous reaction of N2O5 with mineral (Saharan) dust has been studied at T=298 K using a combination of Knudsen and DRIFTS cell for kinetic and product investigations, respectively. The initial uptake coefficient has been determined to be γ=(8.0±0.3)·10−2. This uptake slowly saturates into a steady state uptake of γ=(1.3±0.3)10−2 suggesting that reaction of N2O5 with the mineral dust surface and hydrolysis of N2O5 on the surface take place simultaneously. Moreover, the product investigations suggest that N2O5 is irreversibly taken up forming nitrate on the surface. The uptake rates of N2O5 on Saharan dust are large enough to influence the photo-oxidant budget of the atmosphere.