Community Research and Development Information Service - CORDIS

Final Activity Report Summary - TOTECAT (Tools and techniques for a changing atmosphere: Innovative approach on studying environmentally important questions)

The aim of the 'Tools and techniques for a changing atmosphere (TOTECAT) project was to provide training in the field of atmospheric chemistry and physics. The project consisted of seven long term training programs, each devoted to a different aspect of atmospheric chemistry or physics.

The first project was concerned with laboratory studies of heterogeneous troposphere chemistry. Heterogeneous chemistry of trace atmospheric gases on particulate surfaces could be important for the analysis of reactions in atmospheric chemistry. We studied the heterogeneous reactions of one of the mainly anthropogenic pollutants, nitrogen dioxide (NO2), on sodium chloride (NaCl), a surrogate of marine aerosols. The presence of a native organic coating on field collected marine aerosol particles pushed us to investigate the effect of fatty acids on this removal reaction of nitrogen oxide in the marine boundary layer.

The second project was focussed on the photochemistry of aldehydes. Secondary oxygenated pollutants, such as hydroxyacetone, methylvinylketone and acrolein, resulting from the oxidation of isoprene released in the troposphere by plants, or anthropogenic pollutants like the hydrofluorocarbons, may be photolysed. We succeeded in determining the efficiency of photolysis of these molecules, characterised by the quantum yield, by analysing the time profiles of the photofragments just after the irradiation of gaseous samples with a laser pulse at 266 nm or 355 nm.

The third project refered to the characterisation and transport of aerosols from spaceborne remote sensing and ground-based lidar sounding. Particulate matter was known to have a significant impact on health. Within this project, we used ground base or spaceborn light detection and ranging (LIDAR) instruments to quantify the concentration, size and composition of different aerosol particulates. The ground based LIDAR was employed in different field campaigns, while mathematical methods were applied for the retrieval of satellite data.

The fourth project analysed the formation of soot particles. Soot formation in flames was a complex process involving both physical and chemical transformations. Polycyclic aromatic hydrocarbons (PAH) were generally considered as the main precursors of soot particles. In this work, an experimental setup dedicated to such an investigation was developed. This setup relied on three different experimental techniques, namely laser desorption (LD), laser ionisation (LI) and time of flight mass spectrometry (TOF-MS).

The fifth project investigated the reactivity of the hydroperoxyl (HO2) radicals. This project was dedicated to the construction of a fluorescence assay by gas expansion (FAGE) set up, able to measure ambient atmospheric hydroxide (OH) and HO2 concentrations. This set up was fully operational and was successfully tested in a first field campaign. The set up was also adapted to time resolved measurements by coupling it to a photolysis cell. In this case OH or HO2 radicals were generated in a pulsed way and their concentration was subsequently time resolved by FAGE. This allowed to measure rate constants of reactions involving OH or HO2 under atmospheric conditions.

The sixth project was concerned with the in-situ micro-Raman investigation of aerosol and bulk surfaces. The impact of heterogeneous interactions between the ice and trace gases on the atmospheric physico-chemistry was difficult to quantify because of the specific properties of the ice crystals. Physical parameters were determined on the solubility of formaldehyde in ice and cooled water. The impact of its presence on the structure of ice particles grown by condensation was studied. A clathrate hydrate crystal of formaldehyde could be formed at low temperature.

Finally, the seventh project referred to the tropospheric degradation of volatile organic compounds (VOCs). The degradation of VOCs in the troposphere was generally induced by a reaction with OH radicals, followed by reaction with oxygen (O2). A major intermediate key species in these mechanisms was HO2 radical. In this project we set up a sophisticated experimental technique allowing for the simultaneous, time resolved measurement of both radicals. This set up was employed to study the first steps of the degradation of aromatic hydrocarbons.

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