Kinetics and mechanism of the uptake of N 2O 5 on mineral dust at 298 K
The heterogeneous reaction of N 2O 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 2O 5 with the mineral dust surface and hydrolysis of N 2O 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 2O 5 is irreversibly taken up to form nitrate on the surface. Recent model calculations suggest that the uptake rates of N 2O 5 on Saharan dust which we measured may be large enough to influence the photo-oxidant budget of the atmosphere.