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Abstract

Sulfuric acid with the precurser sulfur dioxide (SO2) is responsible for the formation of aerosols. Nitric acid (HNO3) and methane acid (HCOOH) can affect the aerosol in special atmospheric situations. A longterm change of the atmospheric aerosol composition and changes in size and number of the atmospheric aerosol particles, affect the earth’s climate on a local and global scale. The aim of this work is to quantify the atmospheric mole fractions of the aerosol precursor gases SO2, HCOOH und HNO3. By chemical ionisation mass spectrometry specific product ions of the named precursor gases are formed in an ion reaction chamber and detected by an ion trap mass spectrometer (ITCIMS). Measurement inaccuracies due to wall losses, humidity of the air samples and thus discrepancies in the effective rate coefficients are online calibrated by use of the corresponding isotopic standards. Also changes of the ion residence time in the flow tube are considered. The modified IT-CIMS measurement setup is successfully deployed in the context of the INTEX–B (Intercontinental Chemical transport experiment B) campaign on board of the research aircraft FALCON, which belongs to the German Aerospace Center (DLR). Results of this campaign will be shown and discussed in detail here. A second part of this thesis deals with NOx chemistry as it occurs during electrical discharges during atmospheric lightning for instance. The experiments are performed in close collaboration with the Technical University of Munich which provides the necessary high voltage laboratory. The IT-CIMS is used for quantitative and qualitative analysis of the gaseous HNO2, HNO3, NO3 and HNO3 mole fractions. Corona, arc and lightning discharges are tested. A HNO3/NOy ratio of 0.8 to 4 % is obtained. Finally the gained laboratory HNOx mole fractions are compared to a corona discharge measured during fly through of a thunderstorm cloud. During the INTEX–B campaign Northern American and Asian air masses are located in the free troposphere above Europe, showing enhanced SO2 and HCOOH concentrations. Closer analysis of the sampled air masses shows that by an age of 2–4 days of travel time still enhancements in the HCOOH mole fractions of up to 250 ppt are possible. To further explain its origin as well as its particular high SO2 concentration a during an INTEX-B flight intersected air parcel is compared to an easy back-traceable case of a 7 days old Asian air mass also observed in this campaign. To explain the origin from a determinate air mass with a SO2–molfractions of 1 ppb, located during the INTEX–B campaign, the air mass was compared to an already analysed data of a very young plume (few hours) taken from an earlier campaign named ITOP and a 7 days old asiatic air mass. Analysis leads to an age of about 1 to 3 days and defines the North American continent as origin of the specified air mass.