Final Activity Report Summary - ECITAMA (Evaluation of the Climatic Impact of the Tropospheric Aerosols in the Mediterranean Area) ECITAMA was a multidisciplinary project which comprised of laboratory work, field campaigns and modelling studies to investigate the main factors controlling aerosol variability in the eastern Mediterranean. The major objectives of the project were: 1. to get a better understanding of the main factors contributing to the spatial and temporal variability of the aerosol precursors and aerosols in the eastern Mediterranean; 2. to differentiate between the relative contribution of biogenic and anthropogenic sources to the aerosol budget in the area; 3. to perform simultaneous high-time resolution measurements of aerosol precursors, i.e. of light and heavy Non-methane hydrocarbons (NMHCS), particulate matter and other physicochemical parameters in intensive campaigns at various sites with different geographical locations reflecting distinct aspects of aerosol precursors chemistry; 4. to use the data to determine the relative importance of the Oxidants-like hydroxyl (OH) radical and chloride (Cl) atoms under different atmospheric conditions; 5. to use the database in order to construct a chemistry module capable of describing the atmospheric oxidation capacity in the area. The major scientific achievements of the project were: 1. the development of a specific online sampling and analysis (GC) technique for the detection of natural or anthropogenic source related aerosol precursors in the eastern Mediterranean, including isoprene, benzene, toluene, xylenes, limonene and pinene; 2. the creation of a large database on the abundances of aerosol precursors, including high resolution measurements of C2-C8 hydrocarbons, at three different locations, namely natural, rural and urban; 3. the quantification of the Hydrogen chloride (HCl) gaseous form with a filter packs' technique in order to infer its possible contribution to the Cl atom abundance in the area, as well as the detection and quantification of other gaseous chemical species such as ammonia (NH3), nitric acid (HNO3) and sulphuric acid (H2SO4); 4. the identification and quantification of the ionic composition, i.e. of the major inorganic anions and cations and the major organic anions, of the particles in the fine and coarse mode at a natural site; 5. the discrimination between the contribution of Elemental carbon (EC) and Organic carbon (OC) to the carbonaceous aerosols in the area; 6. the concentrations of the OH radicals and Cl atoms inferred through hydrocarbon measurements and the derivation, for the first time, of the seasonal variability of the Cl atom in the eastern Mediterranean; 7. the estimation of the possible implication of the OH radical and Cl atom abundance on regional atmospheric chemistry. The multidisciplinary approach that was adopted for ECITAMA was successful over the two years of the programme. The project provided a scientific basis needed to better understand and assess the role of various factors contributing to the increase of aerosol burdens in the eastern Mediterranean. The main contributors to the particulate matter in the area were ions, dust and particulate carbonaceous material. In terms of ions, sulphate (SO42-) and ammonium (NH4+) were important ionic components of the sub-micrometric, or else fine mode, aerosol fraction at the investigated site. Dust through its main components, like carbonate and bicarbonate (CO32- and HCO3-), calcium (Ca2+) and magnesium (Mg2+), seemed to play an important role in the coarse mode. Another major outcome of the work indicated that, under well defined and uniform meteorological conditions, hydrocarbon measurements could provide a useful tool to estimate OH radical and Cl atoms at levels that could considerably contribute to the oxidation of hydrocarbons in the troposphere of the investigated region. Contribution from both natural and anthropogenic sources might account for the abundance of various atmospheric chemical constituents, including the gaseous and particulate form, in the eastern Mediterranean.
