The contribution of traffic to atmospheric concentrations of polycyclic aromatic hydrocarbons

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 center of Birmingham, U.K. Concentrations of 17 out of 18 PAH were significantly correlated (greater than or equal to 95% confidence level) to those of CO and NOX. Using the COPAH and NOX-PAH linear regression equations, it is estimated that during this sampling event 71% (59-87%) and 59% (47-81%), 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 site ca. 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 B[e]P as an indicator, the contribution of traffic to concentrations 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 Sigma methyl phenanthrenes/phenanthrene, an estimated 60-84% of total PAH traffic emissions at the city center site originated from diesel vehicles.