Kinetics and mechanism of the uptake of N₂O₅ on mineral dust at 298 K

International audienceThe heterogeneous reaction of N2O5 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 ?=(8.0±0.3)·10?2. This uptake slowly saturates into a steady state uptake of ?=(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. 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 N2O5 is irreversibly taken up to form nitrate on the surface. Recent model calculations suggest that the uptake rates of N2O5 on Saharan dust which we measured may be large enough to influence the photo-oxidant budget of the atmosphere

Heterogene Reaktionen von N_2O_5 und HBr und ihr Einfluss auf den Ozonabbau in der polaren Stratosphaere

Heterogeneous reactions of dinitrogenpentoxide (N_2O_5) and nitric acid (HONO_2) with hydrogenbromide (HBr) were studied in order to get information about the products and mechanisms of these reactions. Furthermore the homogeneous gas pahse reaction of HONO_2 with HBr was investigated. The investigations of the heterogeneous reactions were performed at temperatures below 200 K analysing simultaneously the solid phase by means of FTIR-spectroscopy and the gas phase by mass spectrometry. The characterization of the individual compounds was in good agreement with literature data. The observed differences were due to the different temperatures used in this investigation. (orig.)Available from TIB Hannover: RN 9219(193) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman