Seasonal Trend and Source Identification of Polycyclic Aromatic Hydrocarbons Associated with Fine Particulate Matters (PM2.5 ) in Isfahan City, Iran Using Diagnostic Ratio and PMF Model

Particulate matters (PMs) and their associated chemical compounds such as polycyclic aromatic hydrocarbons (PAHs) are important factors to evaluate air pollution and its health impacts particularly in developing countries. Source identification of these compounds can be used for air quality management. The aim of this study was to identify the sources of PM2.5-bound PAHs in Isfahan city, a metropolitan and industrialized area in central Iran. The PM2.5 samples were collected at 50 sites during 1 year. Source identification and apportionment of particle-bound PAHs were carried out using diagnostic ratios (DRs) of PAHs and positive matrix factorization (PMF) model. The results showed that the concentrations of PM2.5 ranged from 8 to 291 μg/m3 with an average of 60.2 ± 53.9 μg/m3, whereas the sum of concentrations of the 19 PAH compounds (ƩPAHs) ranged from 0.3 to 61.4 ng/m3 with an average of 4.65 ± 8.54 ng/m3. The PAH compounds showed their highest and lowest concentrations occurred in cold and warm seasons, respectively. The mean concentration of benzo[a]pyrene (1.357 ng m−3) in December–January, when inversion occured, was higher than the Iranian national standard value showing the risk of exposure to PM2.5-bound PAHs. Applying DRs suggested that the sources of the PAHs were mainly from fuel combustion. The main sources identified by the PMF model were gasoline combustion (23.8 to 33.1%) followed by diesel combustion (20.6 to 24.8%), natural gas combustion (9.5 to 28.4%), evaporative-uncombusted (9.5 to 23.0%), industrial activities (8.4 to 13.5%), and unknown sources (2.8 to 15.7%). It is concluded that transportation, industrial activities, and combustion of natural gas (both in residential-commercial and industrial sectors) as the main sources of PAHs in PM2.5 should be managed in the metropolitan area, particularly in cold seasons.