Ambient air particulates and related ionic species study at Taichung airport, Taiwan

The concentrations of total suspended particulate (TSP), fine particles (PM2.5) (with aerodynamic diameter < 2.5 mu m), coarse particles (PM2.5-10) (with aerodynamic diameter 2.5-10 mu m), and the related water-soluble ionic species (Cl-, NO2-, NO3-, SO42-, Na+, NH4+, K+, Mg2+, and Ca2+) were studied at the Taichung airport sampling site in central Taiwan during September to December 2005. The results showed that the TSP, PM2.5, and PM2.5-10 concentrations of particulate mass averaged 120.6, 38.1, and 24.2 mu g/m(3), respectively. In general, the ionic species of SO42-, NH4+, and NO3- were higher, being considered the major pollutants for traffic, suburban, rural, urban, and airport sampling sites in central Taiwan. Soil, secondary aerosol, and marine salt were the major pollutant sources at the Taichung harbor sampling site. In addition, the photochemical gas-phase oxidation is the predominant formation mechanism during summer at suburban and urban sampling sites. The secondary aerosol was the dominant factor responsible for this result for the traffic-sampling site. The results also reflected that the water-soluble ionic species in the coarse particulates occupied the major portions except for the ionic species of Na+ and Mg2+ at the Taichung airport sampling site in central Taiwan. Additionally, the results indicated that the sulfate has the highest average composition compared with the other ionic species in TSP and PM2.5 at this airport sampling site. Such information may be useful in forensic investigations at the studied site.