TSP composition data and backward trajectory analysis results at Gosan, Korea, for 10 years between March 1992 and February 2002 are studied to understand the site characteristics and the relationship between the aerosol composition and meteorological conditions. The average non-sea-salt-(nss)-sulfate concentration (6.74 μg m-3) is higher than those observed at other background areas in the world. It was demonstrated that the observed high level of sulfate is due to transport from outside the site. The concentrations of nss-sulfate/ammonium/nss-potassium, sodium/chloride/magnesium, and nss-calcium/nitrate show a strong relationship, suggesting their common emissions sources and/or transport pattern. It is likely that the concentration ratio of nss-sulfate to nitrate is decreasing because of the increase of the nitrate concentration. On the basis of various measurement and emission estimate studies, it is suggested that this trend is mainly caused by the emission trend change in China. About half of the air mass trajectories are from northern China, and a quarter are from southern China. On the basis of cluster analysis, it was found that when air parcels moved from China, the concentrations of nss-sulfate, ammonium, and nitrate are the highest.
- Long-term trend