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The size-separated number concentrations of aerosols ranging from 0.3 to 25 mum were observed in Seoul and Anmyon Island in the west coast of Korea during Asian dust period in Spring 1998. During the heavy dust period, the number size distributions of aerosols observed in both places were characterized by decreases in small size < 0.5 mum and increase in large size between 1.35 and 10 mum, For particles in this range, there was a good correlation between number concentrations observed in both two places. The number of coarse particles > 10 mum showed a distinct diurnal variation without a significant change in amplitude, which was more pronounced in Seoul. It suggests that coarse particles were more affected by local sources. Trajectories back in time showed that the air collected in Korea during dust period originated from desert regions in the central part of China. From these results, it was evident that increased particles in the range of 1.35-10 mum during dust source period represented mineral components, which originated possibly from the dust source regions. (C) 2001 Elsevier Science Ltd. All rights reserved.