Sources of polycyclic aromatic hydrocarbons (PAHs) in street dust in a tropical Asian mega-city, Bangkok, Thailand

We collected samples of roadside air, automobile exhaust soot, tires, asphalt, and used engine oil in a tropical Asian mega-city, Bangkok, Thailand, and analyzed them for polycyclic aromatic hydrocarbons (PAHs) and hopanes. The concentrations and compositions of PAHs and hopanes were utilized to identify the sources of PAHs in street dust, in which high concentrations of PAHs were reported in our previous study. Weight-based concentrations of total PAHs had the following order: gasoline-powered vehicle soot (2600±2900 μg/g; n=4)Ndiesel-powered vehicle soot (115±245 μg/g; n=7)≈roadside aerosols (101±35 μg/g; n=5)≈used engine oil (97±65 μg/g; n=4)≈tire wear particles (82±41 μg/g; n=5)Nasphalt (2.3±1.6 μg/g; n=3)Nstreet dust (1.1±0.8 μg/g; n=10). In cluster analysis, all the source materials fell into different clusters from that in which street dust fell, indicating that multiple source materials contribute to PAHs in the street dust. Multiple regression analysis of PAH profiles and diagnostics of hopane compositions identified tire debris as the major contributor of PAHs to street dust, followed by diesel vehicle exhaust.