Measurement of oxygenated polycyclic aromatic hydrocarbons associated with a size-segregated urban aerosol

Size-segregated atmospheric particles were collected in Boston, MA, using a micro-orifice impactor. The samples were analyzed for oxygenated polycyclic aromatic hydrocarbons (OPAH) using gas chromatography/mass spectrometry. Seven PAH ketones (1-acenaphthenone, 9-fluorenone, 11 H-benzo[a]fluoren-11-one, 7H-benzo[c]fluoren-7-one, 11 H-benzo[b]fluoren-11-one, benzanthrone, and 6H-benzo[cd]pyrene-6-one), four PAH diones (1,4-naphthoquinone, phenanthrenequinone, 5,12-naphthacenequinone, and benzo[a]pyrene-6,12-dione), and one PAH dicarboxylic acid anhydride (naphthalic anhydride) were identified. Seven additional compounds with mass spectra typical of OPAH were tentatively identified. OPAH were generally distributed among aerosol size fractions based on molecular weight. Compounds with molecular weights between 168 and 208 were approximately evenly distributed between the fine (aerodynamic diameter, D-p, < 2 mu m) and coarse (D-p > 2 mu m) particles. OPAH with molecular weights of 248 and greater were associated primarily with the fine aerosol fraction. Most OPAH were distributed with particle size in a broad, unimodal hump similar to the the distributions observed for PAH in the same samples. These results suggest that OPAH are initially associated with fine particles after formation by either combustion or gas phase photooxidation and then partition to larger particles by vaporization and sorption. Two OPAH were distributed in bimodal distributions with peaks at D-p approximate to 2 mu m and D-p approximate to 2 mu m. These bimodal distributions may be indicative of sorption behavior different from PAH and other OPAH.