Characteristics of Atmospheric Polycyclic Aromatic Hydrocarbons and Nitropolycyclic Aromatic Hydrocarbons in Hanoi-Vietnam, as a Typical Motorbike City

We investigated polycyclic aromatic hydrocarbons (PAHs) and nitropolycyclic aromatic hydrocarbons (NPAHs) in airborne particulates collected at two sites (I and T) in Hanoi city, a typical city where traffic jams were caused by many motorbikes. The mean total concentration of 10 PAHs having 4-6 rings at sites I and T ranged from 9.6-63.7 pmol m(-3) and from 24.8-41.9 pmol m(-3), respectively. The predominant PAHs determined were 6-ring PAHs: benzo[ghi]perylene (BghiPe), indeno[1,2,3-cd]pyrene (IDP) and 5-ring PAHs: benzo[b] fluoranthene (BbF), benzo[a] pyrene (BaP). The NPAHs with the highest mean concentrations were 9-nitroanthracene (9-NA) (297 +/- 134 fmol m(-3)) at site I and 1-nitropyrene (1-NP) (331 +/- 103 fmol m(-3)) at site T. Both PAH and NPAH concentrations were higher in winter at site I but higher in summer at site T. Diagnostic markers indicated that motorbikes strongly contributed to atmospheric PAHs and NPAHs in Hanoi city. The contribution of PAHs having 6 rings and 7-NBaA in Hanoi city was larger and the [NPAH]/[PAH] concentration ratios were slightly larger than those in typical automobile cities in Japan and a coal-burning city in China. A possible reason for the higher ratio of 7-NBaA to the total concentration of NPAHs may be that almost all of the motorbikes are not fitted with catalytic converters.