Chemical composition and source signature of spring aerosol in Seoul, Korea

The measurement of atmospheric aerosol was made in Seoul during the spring of 1998. The objective of this study was to investigate the chemical characteristics of atmospheric aerosol with an emphasis on the effect of Asian dust. Total suspended particles (TSP) and particles smaller than 10 μm (PM 10 ) were collected during March‐May 1998. For PM 10 , water‐soluble ions and trace elements were analyzed: NO 3 − , SO 4 2− , Na + , NH 4 + , K + , Mg 2+ , Ca 2+ , Na, Mg, Al, Ca, Fe, Mn, Cr, Co, Cu, Zn, Cd, and Pb. All data were sorted into three groups on the basis of the intensity of Asian dust observed in Seoul: nondust, regular dust, and heavy dust. Chemical characteristics of aerosol were distinct for the heavy dust incidence compared to the other two cases. The average mass concentration of TSP and PM 10 increased substantially during the heavy dust period. For water‐soluble ions, concentrations of SO 4 2− and NO 3 − were the lowest, whereas Ca 2+ and Mg 2+ concentrations were remarkably enhanced. Concentrations and mass fraction of crustal elements such as Na, Mg, Ca, Fe, and Mn were highly elevated, but those of pollution‐derived heavy metals were appreciably decreased. Enrichment ratios of metallic components indicated that soil dust was the primary source of spring aerosols over Seoul. This was also confirmed by factor analysis. Trajectory analysis provided a convincing evidence for the air mass coming from the Asian desert areas, which are the source region of mineral dust. In contrast, the anthropogenic influence was more pronounced for the regular dust period: concentrations of heavy metals, NO 3 − , and SO 4 2− were the highest. It could be associated with the transport of air mass over the industrialized regions of China, which is demonstrated by backward trajectory analysis. The result of factor analysis with high factor loadings in SO 4 2− and NO 3 − implied the considerable influence of industrial emission on the composition of all spring aerosols over Korea.