| Budget Amount *help |
¥6,300,000 (Direct Cost: ¥6,300,000)
Fiscal Year 1996: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1995: ¥900,000 (Direct Cost: ¥900,000)
Fiscal Year 1994: ¥4,500,000 (Direct Cost: ¥4,500,000)
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| Research Abstract |
1) Research and development work was performed for measurements of ^<10>Be and ^<26>Al with Accelerator Mass Spectrometry (AMS) at MALT (Micro Analysis Laboratory, Tandem accelerator), University of Tokyo. Current sensitivities for ^<10>Be and ^<26>Al AMS measurements are ^<10>Be/^9Be=(0.5-1) x10^<-13> and ^<26>Al/^<27>Al=(0.5-1) x10^<-13>, respectively.
2) Contents of ^<10>Be, ^<26>Al and ^<53>Mn in various parts of the Brenham pallasite (stony iron meteorite) were determined. These values were adopted to the universal model for nuclide production in meteorites, which was reported earlier (Nagai et al., GCA1993). As a result, this model was proved to be applicable for the larger body and the heavier shielding samples.
3) The latitudinal distributions of ^7Be and ^<10>Be in the atmosphere over North Pacific Ocean to Antarctic Ocean, have clear features which has maxima of ^7Be and ^<10>Be concentrations around 20 to 30ﾟ in both hemisphere, and minima around equator and 50 to 60ﾟS.The cau
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se for this feature may be elimination of aerosol by wet precipitationor circulation path of tropospheric atmosphere. The average value of ^<10>Be/^7Be were 1.23 and 1.95 in the northern hemisphere and in the southern hemisphere, respectively. This discrepancy may derived from different exchange rate of air between troposphere and stratosphere or resuspension of soil in the continent.
4) Observed ^<10>Be/^7Be value in the ocean surface water in Sulu Sea during KH96-5 Hakuhho-maru cruse were 34.9. Using this value and 1.23 in the atmosphere, the residence time of Be in the ocean surface water was estimated to 1.2 year. The deposition velocity from atmosphere to surface water was calculated to 1.64 cm/sec. Based on ^<10>Be/^7Be variation, the deposition velocity of Be between surface and middle water, i.e.60 to 100 m depth, also estimated to 23year/1000m.
5) The ^<10>Be concentration was measured in the sediment collected at ODP Site 925 on the Ceara Rise in the equatorial Atlantic. The variation of ^<10>Be flux over 7Ma and the high ^<10>Be flux in the last 2Ma could be explained by terrigeous input from Amazon drainage. On the other hand, the variation of ^<10>Be flux derived from the global changes in ^<10>Be production rate did not observed. Less
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