Polycyclic aromatic hydrocarbons (PAHs) in Chicago air

Ambient air samples were collected in Chicago, IL between June and October 1995 as part of a study to investigate the dry deposition and air-water exc hange of polycyclic aromatic hydrocarbons (PAHs). A modified high-volume sa mpler (PS-1 sampler) was used to collect airborne PAHs in both the particul ate and gas phases. The average total (gas + particulate) Sigma(14)-PAH con centration was 428 +/- 240 ng m(-3), similar to those previously observed i n Chicago, IL and other urban areas. The particle/gas phase distribution va ried widely. The gas phase percentage ranged from 1.1 to 99.4%, and general ly decreased with increasing molecular weight. The amount of PAHs associate d with the particulate phase increased with decreasing temperature, probabl y due to the temperature dependence of gas/particle partitioning. Concentra tions of PAHs with molecular weights between 154 and 202 were correlated we ll with phenanthrene concentrations while compounds with molecular weights higher than 202 had little or no correlation with phenanthrene concentratio n, probably due to the different partitioning, transport and removal charac teristics of low and high molecular weight compounds. (C) 1999 Elsevier Sci ence B.V. All rights reserved.