Impacts of PM2.5 sources on variations in particulate chemical compounds in ambient air of Bangkok, Thailand

In this study, PM2.5-bound carbonaceous compounds, including organic carbon (OC), elemental carbon (EC), water-soluble ionic species (WSIS), and polycyclic aromatic hydrocarbons (PAHs) in the ambient air of Bangkok were analysed. The mean PM2.5 concentration was 77.0 +/- 21.2 mu g m(-3), while the average concentrations of OC, and EC were 8.03 +/- 4.02, and 2.62 +/- 1.49 mu g m(-3), respectively. The relatively high OC/EC ratio (3.52 +/- 1.41) coupled with a strong positive correlation between K+ and carbonaceous compounds (K+ vs. OC (r = 0.86), K+ vs. EC (r = 0.87), K+ vs. Char-EC (r = 0.82)) suggest that biomass burning are one of the major contributors to PM2.5 in the sampling area. A comparatively high abundance of both B[g,h,i]P and Ind guides that vehicular exhausts, industrial combustion, and burning of waste might reflect the sources of these PAHs in Bangkok's atmosphere. Interestingly, hierarchical cluster analysis (HCA) indicated that the main source of PM2.5 was a mixture of various combustion activities (e.g. biomass burning, vehicular exhaust, fossil fuel, coal, and industrial emissions). Principal Component Analysis (PCA) successfully classified five principal sources of PM2.5, including vehicular exhaust, biomass burning, sea salt aerosol, power plant, and industrial emissions, which accounted for 43.7%, 24.0%, 10.5%, 6.48%, and 4.46%, respectively. These results indicated that the effects of vehicular exhausts and biomass burning played an important role in governing the PM2.5 level in ambient air of Bangkok. The findings of this study aid policymakers in launching effective air quality control strategies based on the source apportionment analysis.