Atmospheric Transformation of Polycyclic Aromatic Compounds

Abstract

<p> The profiles of polycyclic aromatic compounds (PAC) were compared in three separate studies involving air samples collected in urban and rural locations across Canada. In the Freelton/Pier 25 study (conducted near Hamilton, Ontario) a total of 32 NPAH were analyzed for in 12 composite air particulate samples from Freelton (a rural site) and Pier 25 (an urban site) using negative ion chemical ionization gas chromatography-mass spectrometry.</p> <p> The NPAH levels at the two sites were found to be similar except for the two samples at Pier 25. These results were consistent with the PAH levels determined previously which showed significantly increased levels at Pier 25 under the same condition when the sampling site was downwind of the urban/industrial core. NPAH may be significant contributors to mutation induction due to exposures to ambient air since the offspring of male mice from the Pier 25 site exposed to ambient air showed inherited mutation rates about 2 times greater than offspring of mice exposed at the Freelton site. NPAH are highly mutagenic and carcinogenic compounds that act via reductive metabolism and can be readily metabolized to potent reactive intermediates within all cells.</p> <p> Concentration data for a set of polycyclic aromatic compounds were obtained for samples collected during the day and night during a study in Simcoe (rural) and Toronto (urban) as well as at three sites in British Columbia as part of the Pacific 2001 study (Slocan (urban), Langley (suburban/rural) and Sumas (rural)). The conversion of these concentration data into particulate loadings data (using elemental carbon data) enabled us to perform a number of unique interpretations and analyses of the data sets. Since particulate loadings values are not affected by air dispersion it was possible to compare samples and individual PAC across a range of samples.</p> <p> Principal components analysis of the loadings data showed dramatic differences between the urban and rural sites from each study. Day-night samples at the rural sites also showed dramatic profile differences. The urban sites showed significantly less differences in profiles, consistent with lesser degree of air transformation and closer proximities to sources.</p>