Description: Das Projekt "Die heterogene Umwandlung von Stickoxiden auf Aerosoloberflaechen" wird vom Umweltbundesamt gefördert und von Forschungszentrum Jülich GmbH, Institut für Chemie und Dynamik der Geosphäre durchgeführt. Nitrogen oxides are key players in the tropospheric chemistry. They control the photolytic HOX cycle and the chemical formation of tropospheric ozone. Nocturnal heterogeneous reactions of nitrogen oxides contribute to the daytime chemistry either directly, by the formation of photoactive compounds like HNO2, or indirectly, by the formation of HNO3 whose removal by wet or dry deposition decreases the daytime nitrogen oxide levels. In the continental tropospheric boundary layer the heterogeneous conversion of nitrogen oxides is expected to occur on aqueous inorganic aerosols, but quantitative uptake and conversion rates are scarce. Prerequisite for the quantitative understanding of these heterogeneous processes is the simultaneous chemical and physical characterization of the gas- and the aerosol phase. It is therefore proposed to investigate the heterogeneous reactions of nitrogen oxides on aqueous nitrate and sulfate aerosols in a large aerosol chamber at boundary layer conditions on one hand, and in lab scale flow tube measurements for a wide range of pressures and temperatures on the other hand. Gas phase concentrations will be measured by FTIR absorbance spectroscopy.The aerosol size distribution and total aerosol surface will be monitored by electromobility particle sizing or by optical scattering. For the chemical characterization of the aerosol phase including heterogeneous conversion products jet steam collection combined with ion chromatography will be implemented at the aerosol chamber. In the flow tube studies aerosol conditioning and evaporating of aerosol surface layers with mass spectrometric detection of the evolving gas will be utilized. FTIR extinction measurements of the aerosol substrate and Mie calculations will support the aerosol characterization. The uptake coefficients for NO3 and N2O5 on sulfate and nitrate aerosol will be quantified by the measurement of the gas phase loss. Conversion rates and partitioning of the heterogeneous reactions products between the gas phase and the aerosol phase will be determined by the measured gas phase and aerosol composition. Since the relative humidity controls the aerosol water content, the relative humidity will be varied to quantify the effect of water activity on uptake and conversion rates. Numerical model calculation will aid the evaluation and interpretation of the measurements. The interaction of simulation experiments in the aerosol chamber with full aerosol characterization and flow tube measurements for a wide range of temperature and pressures will yield uptake coefficients, conversion rates, product partitioning factors and mechanistic concepts for atmospheric heterogeneous processes of nitrogen oxides. Quantifying these heterogeneous pathways is an essential step in realistically defining reduction strategies for anthropogenic nitrogen oxide emissions from vehicles and other surfaces sources as well as for the aircraft NOX emissions in the upper troposphere...
Types:
SupportProgram
Origin: /Bund/UBA/UFORDAT
Tags: Jülich ? Luftdruck ? Ozon ? Substrat ? Sulfat ? Nitrat ? NOx-Minderung ? Nitratbestimmung ? Oxid ? Salpetersäure ? Durchflussmessung ? Wasserdampf ? Trockene Deposition ? Aerosol ? Massenspektrometrie ? Schadstoffemission ? Stickoxide ? Temperaturmessung ? U-Bahn ? Ionenchromatografie ? Gasförmiger Stoff ? Bodennahes Ozon ? Chemikalien ? Luftfahrzeug ? Chromatografie ? Reaktionstemperatur ? Simulation ? Simulationsmodell ? Studie ? Troposphäre ? Wassergehalt ? Emission ? Größenverteilung ? Modellierung ? Ionen ? Elektromobilität ? Partikel ? Forschungseinrichtung ? Grenzschicht ? Atmosphärenchemie ? Geosphäre ? Anthropogener Einfluss ? Chemische Reaktion ? Hydroxylradikal ? Aerosolkammer ?
Region: Nordrhein-Westfalen
Bounding box: 6.76339° .. 6.76339° x 51.21895° .. 51.21895°
License: cc-by-nc-nd/4.0
Language: Deutsch
Time ranges: 1997-10-01 - 2000-03-31
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