GAS TO PARTICLE (PM_(10)) PARTITIONING OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHS) IN A TYPICAL URBAN ENVIRONMENT OF THE PO VALLEY (BOLOGNA, ITALY)

摘要

PM_(10) filter samples and polyurethane plugs, collected in the metropolitan area of Bologna (Italy) throughout 2002 and 2003, have been analysed for 9 polycyclic aromatic hydrocarbons (PAHs). Gas-particle partitioning coefficients K_P were determined for all PAHs at various temperatures, and good log K_p vs 1/T correlations were found, allowing us to estimate the heats of sorption of PAHs on PM_(10). Two linear log-log correlations were also checked; the former links K_P and the subcooled liquid vapour pressures (P_L°) with r~2 = 0.88 and slope = -0.54. Slopes shallower than -0.6 indicate that absorption to the organic carbon (OC) microfilm coating particles is the prevailing sorption mechanism and that, by a molecular point of view, intermolecu-lar interactions between PAHs and OC are smaller than intermolecular interactions in the pure liquid PAH. The second linear plot was found between K_P and the octanol-air partition coefficients (K_(OA)) with r~2 = 0.89 and slope = 0.56. The last good fitting again confirms absorption on OC as the most important process, and indicates that chemical composition of paniculate matter in the days examined keeps quite constant, thus reinforcing the hypothesis that a main atmospheric pollution source (vehicular traffic) is responsible for the air quality in the area of Bologna.