Long-term measurements of atmospheric PM2.5 and its chemical composition in rural Korea

Long-term measurements of ambient particulate matter less than 2.5 mu m in diameter (PM2.5) and its chemical compositions were performed at a rural site in Korea from December 2005 to August 2009. The average PM2.5 concentration was 31 mu g m(-3) for the whole sampling period, and showed a slightly downward annual trend. The major components of PM2.5 were organic carbon, SO (4) (2-) , NO (3) (-) , and NH (4) (+) , which accounted for 55 % of total PM2.5 mass on average. For the top 10 % of PM2.5 samples, anionic constituents and trace elements clearly increased while carbonaceous constituents and NH (4) (+) remained relatively constant. Both Asian dust and fog events clearly increased PM2.5 concentrations, but affected its chemical composition differently. While trace elements significantly increased during Asian dust events, NO (3) (-) , NH (4) (+) and Cl were dramatically enhanced during fog events due to the formation of saturated or supersaturated salt solution. The back-trajectory based model, PSCF (Potential Source Contribution Function) identified the major industrial areas in Eastern China as the possible source areas for the high PM2.5 concentrations at the sampling site. Using factor analysis, soil, combustion processes, non-metal manufacture, and secondary PM2.5 sources accounted for 77 % of the total explained variance.