大気中のBe-7、Be-10濃度と同位体比の季節変動

Abstract

Seasonal variations for Be-7 and Be-10 concentrations in air and rain in Tokyo (35.7 deg N, 139.6 deg E) and Hachijo-Island (33.1 deg N, 139.9 deg E) were investigated. The Be-7 and Be-10 in sample were determined by gamma-ray spectrometry and AMS, at Univ. of Tokyo, respectively. The seasonal variations for Be-7 and Be-10 concentrations in Tokyo and Hachijo-Island were similar. Two peaks were observed in spring and fall for Be-7 and Be-10 concentrations. The spring peak was caused by the input of stratospheric aerosol. The Be-7 and Be-10 flux estimated from rain sample was not so similar because they were influenced by many factors such as pH, precipitation and so on. Seasonal variation for the isotopic ratio, Be-10/Be-7, of the air (NA, HA) and filtrated rain (NW, HR) was similar, but different from total deposition (NT). The total deposition samples showed high Be-10/Be-7 value which caused by the input of nearby soil with enriched Be-10. The excess Be-10 from nearby soil were estimated to be 0.025 atoms cm(sup -2) s(sup -1) which correspond to 24 percent and 33 percent for the average Be-10 flux in 2002 (0.105 atoms cm(sup -2) s(sup -1)) and 2003 (0.076 atoms cm(sup -2) s(sup -1)), respectively.