The average value of annual
7Be deposition in Japan from 1989 to 1995 was 1, 500Bq/m
2, the overall range being 290-6, 500Bq/m
2. The
7Be concentration in rain obtained by dividing the annual amount of
7Be deposition by annual precipitation was 0.2-2.8 Bq/
l, giving an average of 1.0±0.4Bq/
l. A large amount of
7Be deposition was found along the Japan Sea, such as in the prefectures of Ishikawa, Toyama, and Fukui, while lesser amounts were found along the Pacific Ocean, and the lowest amounts were found inland and/or in the Setonaikai area. In the areas along the Japan Sea, both precipitation and
7Be concentration in the rain peak during the winter months, which causes large amounts of
7Be to be deposited. Along the Pacific Ocean-side of eastern Japan, an increase in
7Be deposition was observed during spring and autumn, while
7Be deposition in western Japan was in the spring. In the basins of central Japan, as well as in the Setouchi district, only slight
7Be deposition was seen throughout the year.
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