distribution of polycyclic aromatic hydrocarbons in gas phase in urban atmosphere

polycyclic aromatic hydrocarbons (pahs) are toxic pollutants released by various urban combustion sources. tehran is the largest city in iran with a population of about 8 million and it is faced with serious air quality problems. the gas phase samples collected from 21 sites in tehran area throughout year 2005. the samples‘ pahs were collected using a skc trapping consisting of glass cartridge packed with xad-2 resin supported by two polyurethane foam plugs. sixteen pahs were analyzed by hplc with two detectors (fluorescence; uv-vis) according to u. s. environmental protection agency methods.the average concentrations of pahs ranged from 16068.98 î¼g/m3 for bahman site to 1000.24 î¼g/m3 for nour site. the species that presented higher concentration were acenaphtylene (2674.74 î¼g/m3), naphthalene (2467.71 î¼g/m3) and acenaphtene (1245.22 î¼g/m3). the pahs with two and three rings were responsible by 87 % of the total concentration among 16 pahs. a major source of pahs, in tehran area is related to traffic and the number of gasoline and diesel vehicles.