Project Members

Measurements of airborne ²²²Rn, ²¹⁰Pb, ²¹⁰Po and ⁷Be at Tatsunokuchi and Hegra Island

Kazuhisa Komura, Ph. D., Professor [ komurak@po.incl.ne.jp ]

　Airborne ²²²Rn, ²¹⁰Pb, ²¹⁰Po and cosmic ray induced 7Be are monitored at the Low Level Radioactivity Laboratory (LLRL) in Tatsunokuchi and Hegra Island located about 50 km offshore from Noto Peninsula and 600-800 km from opposite shore. The area of Hegra Island is only 1 km² and is considered to be very sensitive to environmental variations of Honshu Island and also of countries of opposite shore.

　Airborne radionuclides are collected on filter paper by using two (occasionally three) high volume air samplers daily at LLRL and weekly at Hegra Island. Special sampling at 1 to several hours of interval will be made in the cases of drastic weather change such as thunderstorm, typhoon, and localized heavy rain. Simultaneous sampling at Tatsunokuchi and highland (skiing field 1000 m or 650 m high) is also planned to investigate vertical distribution and mixing of airborne radionuclides and air mass movement. Sampling locations are shown in Figure 1.

　Gamma ray emitting ²¹⁰Pb and ⁷Be are measured by non-destructive gamma spectrometry using ultra low background Ge detectors in Ogoya Underground Laboratory. On the other hand, ²¹⁰Po is measured by Si detector after radiochemical separation of polonium from 1/4th portion of air-filer. ²²²Rn, which is parent of ²¹⁰Pb and ²¹⁰Po, is monitored by joint work with Nagoya University, at 1 hour of interval both at Tatsunokuchi and Hegra Island.

　In the present study, variations of ²¹⁰Pb, ²¹⁰Po and ⁷Be can be measured with at most 1hr interval which is order of magnitute shorter than previous measurements, therefore, new information on horizontal and vertical air mass movement may be obtained.