Abstract: By means of the Andersen stage sampler, size-segregated atmospheric particles were collected in Chengdu City in winter, 2010. The size distribution spectra of major water-soluble inorganic ions (SO₄^2-, NO₃^-, Cl^-, F^-, NH₄⁺, Ca²⁺, Mg²⁺, K⁺, and Na⁺) were determined. Mass contents of SO₄^2-, NO₃^-, NH₄⁺, Cl^-, K⁺ and Na⁺ mainly concentrated in the fine particles within the size range of 3.3-0.65 μm, and those of Ca²⁺ and Mg²⁺ concentrated in the coarse particles (11.0-4.7 μm). SO₄^2-, NO₃^-, NH₄⁺ and Ca²⁺ were the major inorganic ions in the collected atmospheric particles. Under different weather conditions, mass concentrations of SO₄^2- and NO₃^- decreased in sequence of foggy day, cloudy day and rainy day, and their contents in the foggy day were about 2.5 and 5 times higher than that in cloudy day and rainy day, respectively. Accordingly, the other ions were also about 2 times higher. In the all sizesegregated particles, the ratios of \[NO₃^-\]/\[SO₄^2-\] were less than 1.0, indicating that the air pollution in  Chengdu City are still dominated by stationary source (coal combustion) while the mobile pollution source (main as vehicle exhaust) is becoming increasingly important.

Key words: Quercus wutaishanica population, age structure, life table, survival curve.