Characterization and Source Identification of PM10-bound Polycyclic Aromatic Hydrocarbons in Urban Air of Tianjin, China

PM10 samples were collected at six sampling sites in city center of Tianjin from April 2008 to January 2009. The concentrations of 17 selected polycyclic aromatic hydrocarbons (PAHs) in PM10 were quantified. Spatial and seasonal variations of PAHs were characterized. The dominant PAHs in PM10 samples were fluoranthene, pyrene, benz[a] anthracene, phenanthrene, chrysene, benzo[b]fluoranthene, anthracene, indeno[1,2,3-cd]pyrene and benzo[a]pyrene, accounting for above 85% of total PAHs. The total PAHs concentrations of the six sampling sites ranged from 23.4 to 513 ng/m. Spatial variations were predominantly due to the different strengths of source emission. The total PAHs concentrations at Dongli Monitoring Station (DL) site and Beichen Science and Technology Park (BC) site were higher than those at other four sites in heating period, while those at Meijiang community (MJ) site and Beichen Science and Technology Park (BC) site were higher in no-heating period. Higher PAHs concentrations during heating period and lower concentrations during no-heating period were observed at the six sampling sites, which may be caused by the stronger emissions from stationary combustion sources in heating period and the quicker air dispersion, washout effects, photodegradation and higher percentage in the air in vapor phase in no-heating period. The PAHs concentrations in gaseous phase were predicted with gas/particle partition model, and the BaP and BaP equivalency results indicated that the health risk of gas and particle phase PAHs to human in Tianjin were higher than that in other cities. The contributions from potential sources to PAHs in PM10 were estimated by the diagnostic ratios between PAHs and principal component analysis (PCA). In whole sampling period, coal combustion was found to the predominant contributor of PM10-bound PAHs, followed by vehicles emission and wood combustion.