Ionic constituents and source analysis of PM2.5 in three Korean cities

Ambient PM2.5 samples were taken at 24-h intervals in three Korean cities from September 2002 to February 2004, and their ionic constituents were analyzed. The mean PM2.5 mass concentrations were 42.9, 42.8, and 40.8 μg m−3 in Seoul, Chuncheon, and Ulsan, respectively. In Ulsan, the concentrations in the two winters (2002–2003 and 2003–2004) were statistically different each other because in 2002–2003 the airborne trajectories passed through metropolitan and industrialized areas, whereas in 2003–2004 they did not. Ionic constituents amounted to about 39, 35, and 60% of the PM2.5 masses measured in Seoul, Chuncheon, and Ulsan, respectively. Sulfate was the largest constituent in both Chuncheon and Ulsan, while nitrate was in Seoul. Potential source contribution function (PSCF) was applied in order to identify both the local and regional sources affecting enhanced PM2.5 concentrations in Korea. The southern industrialized area in Korea, including the cities Pohang and Ulsan, was identified as the local sources, and industrial facilities located in eastern China and southern Japan were determined to be the regional sources.