| Budget Amount *help |
¥6,900,000 (Direct Cost: ¥6,900,000)
Fiscal Year 2002: ¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 2001: ¥4,700,000 (Direct Cost: ¥4,700,000)
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| Research Abstract |
The in sib distribution patterns of clay minerals and thermodynamic analysis of quasi-soil solution composition reveal the weathering, sequence of 2:1 minerals in humid Asia as follows : In moderately to highly weathered soils, dioctahedral mica inherited from parent materials is a major source of 2:1 minerals in soil clays. In Thailand, under moderately acidic conditions with annual precipitation of less than 1500 mm, mica is considered to be directly weathered to kaolin minerals with forming few expandable 2:1 minerals, if any. In contrast, under strongly acidic conditions in Indonesia and/or Japan with higher precipitation, mica tends to firstly weathered to expandable 2:1 minerals and then to kaolinite
Such expandable 2:1 minerals formed under acidic conditions can immobilize Cs^+ extensively. In addition, FES of weathered mica can immobilize Cs^+ ion In Thailand and Ukraine, Cs immobilizing capacities of the soils are relatively small and vary depending on the occwYence of FFS in m
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ica minerals. Judging firm the results obtained for Cs-adsorption and desorption behaviors under different ionic strengths, FES immobilize Cs independently of I of a soil solution while collapsed interlayer sites also immobilize Cs but are, to some degree, affected by 1, i.e., increased ionic concentration of surrounding solution may enhance desarption of Cs^+ once immobilized. Such properties of clay minerals on Cs adsorption are possibly modified through soil formation, i.e., hydroxy-interlayering and/or extensive weathering of mica minerals
Generally expandable 2:1 minerals with modeltely-to highly-charged layers can immobilize Cs^+ most strongly. This is the case that occurs in Japan and/or Indonesia among the present study Fortunately such soils in Japan are mostly modified by hydroxy interlayering, which can decrease the chance of irreversible Cs immobilization. Moreover, the Cs^+ ion once immobilized in the collapsed layers of expandable 2:1 minerals can be desorbed if solution I increases. In this sense, these is a room for trying phytoremediacion in Japanese and/or Indonesian soils,although high dose of soluble salts may be required if the main target for extraction of Cs^+ is collapsed 2:1 layers. On the other hand, FES of weathered mica can fix Cs^+ ion independently of solution L In rum, Cs^+ ion once retained by mica minerals would not be released by the change of 1 of surrounding solution In the soils of Ukraine and Thailand, such mica minerals are considered to be mainly responsible for Cs immobilization. It is, therefore, quite difficult to remove Cs^+ ion firm these soils if a fairly large amount of mica minerals is present Less
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