Φυσικοχημική μελέτη αερολυμάτων στην ατμόσφαιρα του λεκανοπεδίου Αττικής

Abstract

The scope of the present Thesis was the chemical characterization of atmospheric aerosol in the atmosphere of Athens basin according to semivolatile organic compounds, SOCs and the study of its physicochemical properties related to the gas/particle partition of SOCs in the atmosphere.In the present Thesis experimental part is consisted of two parts: 1. Study of SOCs concentration in the atmosphere of Attica basin Data concerning particulate and gas phase concentrations of SOCs (PAHs, n-alkanes and PCBs) in the atmosphere of Athens basin are presented in this study for a 17 month period sampling in three sites: an urban heavy traffic site, a semi-urban site influenced by heavy duty diesel vehicles and an industrialized site located in West Attica landfill, influenced by an accidental lanfill fire. It was shown that: • Levels of SOCs were found to be similar to other sites of the same nature in Europe, #sia, North and South America while a weak reducing tendency was found for PAHs levels when comparing to data for a similar study in Patission street, during 1984-1986 • Vehicle traffic emissions were found to be the major source of PAHs and n-alkanes. • PCBs were originated probably by air-surface exchange. • Other sources of SOCs less important, are biogenic for n-alkanes, and industrial activities situated in the south-west region of Attica basin for PAHs and PCBs. • Biogenic sources of n-alkanes become more important during autumn. • Meso-scale air masses circulation induced by Attica basin topography and meteorology, was found to influence significantly atmospheric levels of SOCs. South winds favorite SOCs accumulation and along with west wind are responsible for transport of SOCs from industrialized areas. Data also provided evidence of SOCs both ways transport between Attica basin and Thriasio Plain. • Lanfill fire incident resulted to elevated levels in the atmosphere for selected PAHs and PCBs. 2. Study of gas/particle partition of SOCs in the atmosphere of Attica basin Temperature dependence of partition showed that: • Temperature was found to be not the only factor controlling gas phase concentration and partition constant of SOCs, giving evidence for local emissions impact and transport from adjacent areas. • Meso-scale air masses circulation was also found, for some SOCs, to provide conditions for discernible types of aerosol according to physical and chemical properties of their partition. Both descriptions, using either vapor pressure or octanol-air partition coefficient were applied in order to parameterize SOCs partition in Athens atmosphere. It was shown that: • Deviations from the prediction models were found in both cases and were attributed to nonexchangeable fraction of pyrogenic volatile SOCs. • Non-equilibrium state probably results by proximity to the sources, slow sorption or desorption of non-volatile SOCs due to low diffusion rates and atmospheric reaction of SOCs in gas and particle phase. The octanol-air model was used to calculate theoretical partition constants. The octanol,soot-air model was applied as well, to calculate theoretical partition constants for each sampling event It was found that: • Octanol-air, soot-air combined model was found to predict accurately PAHs partition especially when air masses were originated by heavy emission areas. • Octanol-air, soot-air combined model also gave PCBs partition constants closer to the experimental value for landfill fire samples. • Octanol-air model was better for predicting PCBs partition constant and only in the case of landfill fire was appropriate for PAHs partition. • Results are suggesting that PAHs partition is close to an adsorption process while PCBs and nal kanes partition is closer to an absorption process