The Estimation of the Influence of Kosa Phenomenon on Aerosols in Japan by the Measurement of Rb and Sr in the Airborne Particles

The concentration ratio between Rb and Sr in soils varies in different localities. The ratio has been used to presume an earthenware-producing district in an archaeological field. In this study, desert soils in Taklamakan, Gobi and Alashan, these deserts were considered to be a major source of Kosa, and soils in Japan were Analyzed by X-ray fluorescence method. The ratios of Rb/Sr in desert soils in China were about 0.47, and those in Japanese soils were more than 0. 80 in the western Japan and less than 0.60 in the eastern Japan. These ratios in soils showed clearly different localities. Aerosol samples monthly collected at 11 sites in NASN (National Air Surveillance Network), 1981, were also analyzed by X-ray fluorescence method. The ratio of Rb/Sr in aerosols was 0. 60 in the western Japan and 0. 40 in the eastern Japan in the average of 12 months. On the other hand, the ratio of Rb/Sr in aerosols in metropolitan and industrial area such as Tokyo, Nagoya and Osaka was 0. 90; higher than other area due to the contribution of Rb from the steel industry. As the result of measurements of Rb and Sr in both aerosols and soils, it was found that the ratio of Rb/Sr in aerosols at each site in Japan strongly reflected that in soils except at metropolitan and industrial sites. However, the ratios of Rb/Sr in aerosols at most of sites were close to those of desert soils in China (0. 47), on May, 1981 when Kosa phenomenon was observed everywhere in Japan. Especially, in the western Japan, the ratio of Rb/Sr in aerosols largely decreased and became close to 0. 47 on May, 1981. This is because the western Japan is geographically near the Asiatic Continent and aerosols in the western Japan were strongly affected by desert soil particles transported by Kosa phenomenon.