Water-soluble ionic species of coarse and fine particulate matter and gas precursor characteristics at urban and rural sites of central Taiwan

Coarse and fine particulate matter (PM) were taken by a dichotomous sampler, and gas precursors were determined by a denuder sampler at two stations in central Taiwan. Water-soluble ionic constituents of PM and their precursor gases were analyzed by ionic chromatograph. In summer, the daytime/nighttime PM₁₀ concentrations were 37 ± 10/41 ± 18 μg m⁻³ and 36 ± 14/34 ± 18 μg m⁻³ for Xitun and Jhushan, respectively. Average PM₁₀ concentration in winter was 1.55 and 1.76 times that of summer for Xitun and Jhushan, respectively. PM mass concentrations were similar for both stations, although one station is located in the downtown area of Taichung, and the other is in a rural area with no heavy pollution sources. Water-soluble ionic species content was 38–53 % of PM_2.5 and 43–48 % of PM₁₀ mass concentration. HNO₃, HCl, and SO₂ were high in the daytime; the daytime-to-nighttime concentration ratio was 3.75–6.88 for HNO₃,1.7–7.8 for HCl, and 1.45–2.77 for SO₂. High NH₃ levels were determined in the area, especially in winter, which could be a precursor of NH₄ ⁺ to form particulate matter. In Xitun, motor vehicles downtown and in the industrial district could be sources of air pollution. In contrast, there are few industrial sources at Jhushan; therefore, the transport of air pollutants from upwind of other regions and the accumulation of pollutants could be important PM sources at Jhushan.