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 (≥ 95% confidence level) to those of CO and NO x . Using the CO-PAH and NO x -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 Σmethylphenanthrenes/phenanthrene, an estimated 60−84% of total PAH traffic emissions at the city center site originated from diesel vehicles.