A study of 16 EPA priority polycyclic aromatic hydrocarbons (PAHs) associated with particulate matter (PM2.1) in the ambient air in Nanjing was carried out from November 2009 to July 2010.Total PAH concentrations during the sampling period were in the range of 25.91-102.25 ng/m3(average value: 58.09ng/m3),with relatively higher values in nighttime rather than daytime.Differing from other studies,PM2.1-bound PAHs were found to be more abundant at suburban site,which was due to the sharp increase in vehicle numbers for recent years in suburban along with the development of urbanization and the unique industrial circumstance around the suburban site.Whats more,similarities between the profiles for two sites were identified by using coefficient of divergence,predicting PAHs from the two districts have common sources.Correlation analysis proved the PM2.1-bound PAHs mainly derived from combustion activities and the species of BbF,Chr,Fla,InP,BeP,BghiP,all of which were vehicle markers,dominated the PAH profiles.The average concentrations in four reasons were in the order of winter>spring>autumn >summer,owing to both pollution sources local or external and meteorological factors.Apportioned by Diagnostic ratios and Principal component analyses(PCA),yearly potential sources of PM2.1- bound PAHs in Nanjing were traffic exhaust and coal consumption including coal combustion,coal gas production and coke oven.During autumn,local emission provided a higher level of contribution with the source of wood/biomass burning supplied.However,air masses in spring and winter were relatively aged and influenced more by long range transport.Particulates in summer were diluted by Asian monsoon with much degradation happened.