[Size distributions and diurnal variations in the concentrations of polycyclic aromatic hydrocarbons in winter in urban and suburban Nanjing, China].

The contamination status and distribution characteristics of particulate polycyclic aromatic hydrocarbons (PAHs) were investigated in aerosols of urban and suburban Nanjing. A total of 17 PAHs were analyzed in the aerosol samples collected in daytime and nighttime during January 1st to 10th, 2010 in Nanjing University (NU) and Nanjing University of Information Science & Technology (NUIST). The PAH concentrations at the urban and suburban sites were 41.36-220.35 ng x m(-3) and 45.10-200.86 ng x m(-3), respectively, of which about 66%-67% was absorbed by fine particles (Dp < or = 2.1 microm). High levels of particulate PAHs were detected at both sampling sites with different diurnal variations. The higher total-PAH concentration occurred in the daytime at the urban site and in the nighttime at the suburban site. The change of prevailing wind direction and high-pressure weather system had significant impact on the variation of PAH concentrations, which were dominated by fine and coarse particles in urban and suburban regions, respectively. Difference in PAH size distributions was found for low weight molecular PAHs (LWM-PAH) and high weight molecular PAHs (HWM-PAH) in urban and suburban areas. The concentrations of 2-3 ring PAHs were higher at the suburban site than those at the urban site, whereas larger amounts of 4-6 ring PAHs were found at the urban site than at the suburban site. The concentration peaks in coarse particle size of high-molecular-weight PAHs found in our study were larger than those in some of the previous studies, which might be due to the high carbon content in coarse particles in the atmosphere at our sites. Analysis of diagnostic ratios indicated that the PAHs particles at both two sites have the same sources, including combustion of coal and biomass, vehicular exhaust and suburban industrial emission.