Determination of octanol-air partition coefficients and supercooled liquid vapor pressures of PAHs as a function of temperature: Application to gas-particle partitioning in an urban atmosphere

Octanol-air partition coefficients (K-OA) for 14 polycyclic aromatic hydrocarbons (PAHs) were determined as a function of temperature using the gas chromatographic retention time method. log K-OA values at 25 degrees ranged over six orders of magnitude, between 6.34 (acenaphthylene) and 12.59 (dibenz[a,h]anthracene). The determined K-OA values were within factor of 0.7 (dibenz[a,h]anthracene) to 15.1 (benz[a]anthracene) of values calculated as the ratio of octanol-water partition coefficient to dimensionless Henry's law constant. Supercooled liquid vapor pressures (P-L) of 13 PAHs were also determined using the gas chromatographic retention time technique. Activity coefficients in octanol calculated using K-OA and P-L ranged between 3.2 and 6.2 indicating near-ideal solution behavior. Atmospheric concentrations measured in this study in Izmir, Turkey were used to investigate the partitioning of PAHs between particle and gas-phases. Experimental gas-particle partition coefficients (K-p) were compared to the predictions of K-OA absorption and K-SA (soot air partition coefficient) models. Octanol-based absorptive partitioning model predicted lower partition coefficients especially for relatively volatile PAHs. Ratios of measured/modeled partition coefficients ranged between 1.1 and 15.5 (4.5 +/- 6.0, average +/- SD) for K-OA model. K-SA model predictions were relatively better and measured to modeled ratios ranged between 0.6 and 5.6 (2.3 +/- 2.7, average +/- SD). (c) 2006 Elsevier Ltd. All rights reserved.