SIRE DISTRIBUTIONS OF POLYCYCLIC AROMATIC-HYDROCARBONS AND ELEMENTAL CARBON .1. SAMPLING, MEASUREMENT METHODS, AND SOURCE CHARACTERIZATION

Ten polycyclic aromatic hydrocarbons (PAHs) were measured in size-segregated aerosol samples of 0.05-4 mu m diameter collected by a low-pressure impactor sampler using a high-resolution analysis procedure based on HPLC and fluorescence detection. This method can-be used to characterize both vehicular emissions and ambient aerosol, allowing meaningful intercomparison. A field study was carried out at two traffic tunnels to characterize the vehicular source. PAH and elemental carbon (EC) size distributions measured in the Caldecott Tunnel were unimodal with over 85% of the mass in particles smaller than 0.12 pm aerodynamic diameter. Ambient air intrusion into the relatively short Sepulveda Tunnel resulted in small secondary peaks in the PAH distributions in the 0.5-1.0-mu m size range. These size distributions, when corrected for ambient air intrusion using a mass balance of PAH and CO, were unimodal. PAH profiles (PAH/Benzo[k]fluoranthene ratios) were developed for the vehicular source, which can be used in receptor modeling estimations for source allocation.