Impending legislation pertaining to atmospheric PAH concentrations has intensified efforts to identify their sources. Particulate-phase PAH were measured every 2 h between 06.00 and 20.00 on 12/5/96 at a heavily trafficked location in the centerof Birmingham, U.K. Concentrations of 17 out of 18 PAH were significantly correlated (> 95 confidence level) to those of CO and NO{sub}x. Using the COPAH and NO~PAH linear regression equations, it is estimated that during this sampling event7l (59-87)and 59 (4781), respectively, of 4-7 ring PAH originated from traffic. At weekly intervals between 7/15/97 and 12/9/97, simultaneous monitoring of particulate-phase PAH was conducted over 24 h periods at the same city center location, and a campus siteca. 3 km southwest of the city center, and ca. 500 m from the nearest busy road. Intersite differences in PAH concentrations should thus arise primarily from differences in traffic emissions. Using BeP as an indicator, the contribution of traffic toconcentrations of 4-7 ring PAH at the two sites was estimated at 80-82 and 61-67 for the city center and campus sites, respectively. Utilizing ratios of∑methylphenanthrenes/phenanthrene, an estimated 60-84 of total PAH traffic emissions at the citycenter site originated from diesel vehicles.
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