Μελέτη της κατανομής των πολυκυκλικών αρωματικών υδρογονανθράκων (ΠΑΥ) στην αέρια και σωματιδιακή φάση της ατμόσφαιρας και των διεργασιών απομάκρυνσής τους μέσω υγρής - ξηρής απόθεσης

Abstract

The aim of this research was to investigate the partitioning of Polycyclic Aromatic Hydrocarbons (PAHs) and their removal mechanisms from the atmosphere by wet and dry deposition. More precisely, the concentrations of 13 EPA PAHs were determined in the gas and particulate phase at an urban, a rural and an adjacent coastal site in the Eordea Basin, western Greece. Four large power plants operate in the area, which produce approximately 2/3 of the country’s electric power requirements by lignite burning. The seasonal and spatial variations of the concentrations and the distribution between the gas and particle phase were evaluated. The coefficients of the partitioning, KP, were regressed against the ambient temperature, the subcooled liquid vapor pressure of the compound (PLo) and the octanol-air partitioning coefficient (KOA) in order to assess whether or not the theoretical models that have been suggested by Yamasaki et al. (1982), Pankow (1987) and Finizio et al. (1997) can describe the partitioning of PAHs in the area. The experimentally obtained partition coefficients were compared with theoretical predictions based on the absorption model and the absorption + adsorption model in an effort to estimate which mechanism dominates the partitioning of PAHs in the three areas. Moreover, the dry and wet deposition fluxes of PAHs were measured and their relative contribution in the overall removal from the atmosphere was assessed. The total (gas+particle) deposition velocities and the scavenging ratios of PAHs in the gas and particulate phase were determined, so as to estimate which of the two phases is more efficiently removed from the atmosphere by the two mechanisms. The main conclusions of the research can be summarized to the following: PAH concentrations in the atmosphere • The mean concentrations of particulate ΣPAHs were 0.814, 3.33 and 2.49 ng m-3 and the mean concentrations of the gas phase ΣPAHs were 3.06, 14.4 and 24.1 in the rural, the adjacent coastal and the urban site, respectively. ΣPAH concentrations exhibited significant spatial differences suggesting that the three sites are affected by sources of different strength. Seasonal variations were important only for the particulate phase PAHs with the highest concentrations observed during the cold period of the year. • The particulate PAH profile in the rural site was different from the profile in the other sites, with Ph and Fl being the more abundant PAHs, while in the other sites the higher molecular weight PAHs with five and six rings contributed the 70% of the total. The PAH profile of the gas phase was similar in all the three sites. Gas-particle partitioning of PAHs