Comparison of polycyclic aromatic hydrocarbons and nitropolycyclic aromatic hydrocarbons in airborne and automobile exhaust particulates

Polycyclic aromatic hydrocarbons (PAH) and nitropolycyclic aromatic hydrocarbons (NPAH) in airborne particulates collected simultaneously at downtown and suburban sites and in exhaust particulates from diesel and gasoline engine vehicles were determined. The mean concentrations of all compounds in the atmosphere were lower at the suburban site. The differences between the two sites were smaller in airborne particulates than in the atmosphere. However, the difference in NPAH concentrations in particulates between the two sites was greater than the difference in PAH concentrations, suggesting that the NPAH were less stable than the PAH, The concentrations of 1-nitropyrene and 1,3-, 1,6- and 1,8-dinitropyrenes were generally much higher in automobile exhaust particulates than in airborne particulates because the former were collected directly. However, 2-nitrofluoranthene and 2-nitropyrene were observed in airborne particulates but not in automobile exhaust particulates. The diurnal concentrations showed that 2-nitrofluoranthene and 2-nitropyrene might be formed by a hydroxyl radical-initiated reaction followed by nitration.