Raman spectroscopic study of inorganic salts present in atmospheric particulate matter : their origin and implications
The aim of this doctoral thesis is to investigate aspects concerning the atmospheric origin of some inorganic salts of known atmospheric occurrence. In this context, based on laboratory experiments, the atmospheric formation of certain inorganic salts is proposed in view of the common presence of certain ions in the atmosphere and their interaction with atmospheric water. The condensation-evaporation cycles have a strong influence on the composition of the particles and the modifications taking place during the transport (aging). The evaporation of solution droplets containing specific ions results in the crystallization of mixed salts (e.g., bloedite, darapskite, koktaite, etc.) confirming the preponderant role of water in the modification of the atmospheric particles. Moreover, certain alkaline minerals can react with (NH4)2SO4 in contact with humid air, showing that water is a key factor to trigger chemical reactions in solid particles. Raman spectroscopy is the main analytical tool used in this work, therefore, the bands observed in the Raman spectra of all pure salts considered in this investigation have been properly assigned. The Raman-specific features of some salts were discussed from the point of view of their crystal structure. General aspects of the significance of atmospheric particulate matter to human health, the atmospheric chemistry and climate are outlined.