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Abstract
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.
Acknowledgments
The authors thank Prof. Nguyen Thi Phuong Thao and Mr. Hoang Van Tu (Vietnam Academy of Science and Technology) for supporting the field surveying and setting of higher volume samplers in air sampling.