Gas-to-particle partitioning of polycyclic aromatic hydrocarbons in an urban atmosphere

Semi-volatile organic compounds (SOCs) are present in the atmosphere as vapors and are adsorbed to particulate matter. Knowledge of the gas-to-particle distribution of these compounds is important in understanding their atmospheric fate and transport. A baseline experimental study to estimate the vapor- and particle-phase-associated concentrations of the SOCs (specifically, polycyclic aromatic hydrocarbons, PAHS) in the Baton Rouge (Louisiana) air was carried out. A comparison of the levels of concentrations of PAHs obtained in Baton Rouge to those obtained in other parts of the world is made. The sampling artifacts associated with a traditional high-volume sampler introduced errors in the estimation of the partition coefficient. Different air sampling procedures (a modified. low-volume sampler and an annular denuder) were evaluated in order to obtain a more accurate measure of the gas-to-particle partition coefficient. The effects of temperature and precipitation on the partitioning of PAHs between the vapor and particulate phase were ascertained.