Urban air PAHs: Concentrations, temporal changes and gas/particle partitioning at a traffic site in Turkey

Abstract

Atmospheric concentrations and gas/particle partition coefficients were determined for polycyclic aromatic hydrocarbons (PAHs) in the city of Bursa, Turkey between August 2004 and May 2005. The average total (gas + particle) PAH concentration was 456 ± 524 ng m- 3. The ambient air concentrations were mainly influenced by traffic and industrial activities. PAH compounds considered in this study predominantly existed in the gas phase and the average contribution of gas phase to total (gas + particle) PAH concentrations was about 90% which was in line with the previously reported values. The partitioning between the particle and gas phases was investigated in this study because gas/particle-partitioning coefficient (Kp) has an important role on the fate of PAHs. Experimentally determined Kp values correlated well with the subcooled liquid vapor pressures (PL0) of PAHs. The octanol-air partition coefficient (KOA), which can also be used to calculate Kp values, gave high correlation coefficients with the PL0. In another approach, the Kp values were estimated by considering adsorption onto the soot carbon and absorption into organic matter of atmospheric particulates. In general, Kp values calculated based on KOA gave smaller values than the ones predicted based on soot/air (KSA) partition coefficient. Sorption of PAHs on particles was underestimated by KOA suggesting that absorption would not be enough to explain partitioning and adsorption would still be important.