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-segr egated aerosol samples of 0.05-4 mu m diameter collected by a low-pres sure impactor sampler using a high-resolution analysis procedure based on HPLC and fluorescence detection. This method can-be used to charac terize both vehicular emissions and ambient aerosol, allowing meaningf ul intercomparison. A field study was carried out at two traffic tunne ls to characterize the vehicular source. PAH and elemental carbon (EC) size distributions measured in the Caldecott Tunnel were unimodal wit h over 85% of the mass in particles smaller than 0.12 pm aerodynamic d iameter. Ambient air intrusion into the relatively short Sepulveda Tun nel 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 unimoda l. PAH profiles (PAH/Benzokfluoranthene ratios) were developed for t he vehicular source, which can be used in receptor modeling estimation s for source allocation.