The size distribution of210Po in the atmosphere around Mt. Sakurajima in Kagoshima prefecture, Japan

Abstract

The concentration and size distribution of 21~ in particulate matters in the atmosphere were measured around the active volcano, Mt. Sakurajima in Kagoshima prefecture, Japan. The samples were collected eight times at four sampling points for the period from June 1994 to January 1996. The highest concentration of 21~ was 2940 p.Bq/m 3 at Akamizu located 2 km away from the crater of Mt. Sakurajima. The 21~ concentrations decreased with the increase of distance from Mt. Sakurajima. The size distribution curves of 21~ in the particulate matters showed that 21~ is usually condensed to fine particles smaller than 2 p.m in diameter. In addition, it was suggested that the 21~ concentration in particulate matters collected at Akamizu was affected by the wind direction over Mt. Sakurajima.