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

Polycyclic aromatic hydrocarbons (PAH) and nitropolycyclic aromatic hydroca rbons (NPAH) in airborne particulates collected simultaneously at downtown and suburban sites and in exhaust particulates from diesel and gasoline eng ine vehicles were determined. The mean concentrations of all compounds in t he atmosphere were lower at the suburban site. The differences between the two sites were smaller in airborne particulates than in the atmosphere. How ever, the difference in NPAH concentrations in particulates between the two sites was greater than the difference in PAH concentrations, suggesting th at the NPAH were less stable than the PAH, The concentrations of 1-nitropyr ene and 1,3-, 1,6- and 1,8-dinitropyrenes were generally much higher in aut omobile exhaust particulates than in airborne particulates because the form er were collected directly. However, 2-nitrofluoranthene and 2-nitropyrene were observed in airborne particulates but not in automobile exhaust partic ulates. The diurnal concentrations showed that 2-nitrofluoranthene and 2-ni tropyrene might be formed by a hydroxyl radical-initiated reaction followed by nitration.