Polycyclic Aromatic Hydrocarbons and Nitropolycyclic Aromatic Hydrocarbons in Motorcycle Exhaust

Abstract

This study investigated the polycyclic aromatic hydrocarbons (PAHs) and nitropolycyclic aromatic hydrocarbons (NPAHs) in airborne particulates, soil, and motorcycle exhaust in Hanoi city. This was performed in order to understand the environmental behaviors of PAHs and NPAHs and the contribution of motorcycles to soil and atmospheric PAHs and NPAHs in a typical motorcycle city of Vietnam. The atmospheric PAHs and NPAHs distribution in Hanoi were characterized and showed a higher contribution of six-ring PAHs: benzo[ghi]perylene (BghiPe), indeno[1,2,3-cd]pyrene (IDP) and the four-ring NPAH: 7-nitrobenz[a]anthracene (7-NBaA) in a motorcycle city compared to those in typical automobile cities (Kanazawa and Tokyo, Japan) and a coal-burning city (Shenyang, China). This study showed that the concentration of benzo[a]pyrene (BaP), the most toxic PAH, was exhausted from motorcycles at much higher concentrations than from automobiles. Furthermore, among four detected NPAHs, 6-nitrochrysene (6-NC) and 7-NBaA were the dominant compounds in motorcycle exhaust. These may contribute to their higher concentrations in the atmosphere and soil in Hanoi. This study also found that despite small engine sizes, motorcycles emitted much more particulate matter (PM) and PAHs than automobiles. PM emitted from motorcycles showed stronger PAH-related carcinogenicity and indirect-acting mutagenicity but weaker NPAHs-related direct-acting mutagenicity than PM from automobiles. This study provides useful information to control environmental pollution and to improve air quality in motorcycle cities in Southeast Asia.