Size distribution and resources of pahs in atmospheric particulate matters in Ho Chi Minh city

Abstract

In this study, size distribution of 10 PAHs, with 4 – 6 rings in atmospheric particulate matters (PM) at the basement, the roadside and the ambient air in Ho Chi Minh City were measured from 27 December 2010 to 26 January 2011. PM was separated into nine fractions of different sizes as follows: > 9.0, 9.0 – 5.8; 5.8 – 4.7; 4.7 – 3.3, 3.3 – 2.1; 2.1 – 1.1; 1.1 – 0.7, 0.7 – 0.4; và < 0.4 µm. The results showed that the total concentrations of 10 PAHs (total PAHs) varied from 29.7 – 43.7 ng/m³, 37.1 – 45.7 ng/m³, and 8.8 – 18.1 ng/m³, respectively, at the basement site, the roadside site and the ambient air site. Total PAHs were mainly concentrated in particles with aerodynamic diameter smaller than 0.4 μm at the basement and roadside site. On the other hand, total PAHs were mainly concentrated in particles with aerodynamic diameter 0.4 – 0.7 μm at the ambient air site. Generally, the five- and six-ring PAHs were predominately on fine particles (smaller than 2.5 μm aerodynamic diameter) and the 4 – ring PAHs spread-out in both fine and coarse particles (more than 2.5 μm aerodynamic diameter). Diagnostic ratios of specific PAHs were used to characterize the PAH emission sources in the atmosphere. The result of this study indicated that motorcycles and gasoline automobiles are suggested as the main emission sources of PAHs in Ho Chi Minh City and it is necessary to control PAHs concentration in air environment in Ho Chi Minh City.