Correlations Between PAHs and CO, NO, NO₂, O₃ along an Urban Street

Abstract

Since 1997 to 1999, bimonthly measures of daily PAH concentrations, adsorbed on airborne particulate (PM₁₀) have been carried out in Genoa (Italy), along a canyon street, crossed daily by about 27.000 vehicles. Simultaneous concentrations of CO, NO, NO₂ were evaluated in the same sampling site. Ozone concentrations were measured in two sampling stations, far from traffic, and their daily mean was used as a measure of oxidative strength of urban air in Genoa.

PAHs correlate positively with CO and NO. Negative correlations were found with NO₂ and particularly with O₃. Cyclopenta(cd)pyrene was confirmed the most reactive PAH, while benzo(e)pyrene showed a relative stability.

Multiple linear regression analyses confirmed that PAH concentration covariates mainly with CO and O₃, while NO₂ has negligible correlation. According to these results, benzo(a)pyrene concentrations are well predicted (standard error = 0.35 ng/m3), by the following equation:

These results suggest that traffic is the main PAH source in the studied site and in urban atmosphere PAHs adsorbed on suspended particulate may be degraded also by oxidation.

Key Words:

• Urban air pollution
• sources
• degradation
• polycyclic aromatic hydrocarbons
• carbon monoxide
• nitric oxide
• nitrogen dioxide
• ozone