To estimate the residence times of aerosols in air, the activities of 210Pb and 210Po in aerosols were measured at 4 sites in Pusan. All aerosol samples were collected by a high volume air sampler from January to October 1996. The activities 210Pb and 210Po in Pusan were varied from 11.77 to 67.57 dpm/1000㎥ and from 2.63 to 15.91 dpm/1000㎥, respectively. The mean activities were 34.62 dpm/1000㎥ for 210Pb and 8.24 dpm/1000㎥ for 210Po. The highest values of the activities of 210Pb and 210Po were appeared at P3 site and the lowest values at P4 site. During the sampling period, the trends of the activities of 210Po and 210Pb were similar to total suspended particulate matter(TSP) concentrations. The mean residence times of atmospheric aerosols calculated from 210Po/210Pb activity ratio was about 60∼80 days in Pusan. The longest residence time of atmospheric aerosols was in January because of the lack of rainout and washout, but the shortest residence time was in August, largely due to scavenging effect by frequent rains. The activities of 210Po and 210Pb in atmospheric aerosols were different in time and space, which seems that the distribution of 210Po and 210Pb activities and scavenging processes in air may be controlled by the local and meteorological conditions.

Chemical composition of atmospheric aerosols was measured at 4 sites in Pusan. All the samples were collected with a high volume air sampler from January to October 1996, to analyze major ions and heavy metals. Dominant ions of aerosols were SO42- in anion and Na+ in cation. Sulfate, nitrate and ammonium ions in aerosols showed high enrichmentfactor to soil and seawater composition. The concentrations of heavy metals in aerosols was lowest at the site P1 near the coast. The lowest concentrations of major ions and heavy metals mainly appeared in August, probably due to scavenging by frequent rains. Especially, the concentrations of total suspended particulate matter(TSP) and heavy metals in aerosols showed good correlations in Pusan. Based on crustal Al, enrichment factors for some metals(Zn, Cu, Pb, Cd) in aerosols were significantly greater than unity, and the order was Cd > Pb > Zn > Cu. This evidence suggests that Cd and Pb are derived predominantly from non-crustal sources.