[Seasonal variation of water-soluble ions in PM2.5 at Changbai Mountain]

To study seasonal variation of water-soluble ions in PM2.5 at Changbai Mountain. PM2.5 was collected with a high-volume sampler from Jun. 2005 to Dec. 2008, and the concentrations of water-soluble ions were analyzed using ion chromatography. The results showed that the three major ions of SO4(2-), NH4+ and NO3 showed obvious seasonal variation. The mass concentration of SO4(2-) was the highest in summer and lowest in autumn. The mass concentration of NO3- was the highest in winter and lowest in summer. The seasonal variation of NH4+ was influenced by SO4(2-) and NO3-. The total concentrations of water-soluble ions in PM2.5 from different directions were evidently different, following the order of NE < NW < SW, with the average concentrations of 5.43, 7.63 and 10.26 microg x m(-3), respectively. Ca2+ was strongly correlated with CO3(2-), and the correlation(R) was higher in spring (0.74) than that in summer (0.30).