Variation of Be-7 concentration in surface air at Nagano, Japan

摘要

The concentration of Be-7 in surface air at Nagano City has been measured during the period from August 2000 to March 2005. The average monthly concentrations of Be-7 in surface air were in the range of 3.3 - 14 mBq/m(3) with pronounced two peaks in spring and autumn. It took 30 - 40 hours to recover the Be-7 concentrations observed before, once Be-7 was washed out by wet precipitations. For a pronounced increase in the concentrations of Be-7 found in winter, a low-pressure trough coming close to the Japanese Islands with high concentrations of Be-7 is responsible under the characteristic distribution of atmospheric pressure around the Japanese Islands.