| Project/Area Number |
17340169
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Geochemistry/Astrochemistry
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| Research Institution | Gakushuin University |
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Principal Investigator |
MURAMATSU Yasuyuki Gakushuin University, Faculty of Science, Professor (70166304)
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| Co-Investigator(Kenkyū-buntansha) |
AMACHI Seigo Chiba University, Faculty of Bioresorces, Assistant Professor (80323393)
MATSUZAKI Hiroyuki Tokyo niversity, MALT, Associate Professor (60313194)
MATSUMOTO Ryo University of Tokyo, Department of Geology, Professor (40011762)
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| Project Period (FY) |
2005 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥15,900,000 (Direct Cost: ¥15,000,000、Indirect Cost: ¥900,000)
Fiscal Year 2007: ¥3,900,000 (Direct Cost: ¥3,000,000、Indirect Cost: ¥900,000)
Fiscal Year 2006: ¥5,200,000 (Direct Cost: ¥5,200,000)
Fiscal Year 2005: ¥6,800,000 (Direct Cost: ¥6,800,000)
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| Keywords | iodine / iodine-129 / biogeochemistry / analytical method / chemical species / underground brines / soil / AMS (accelerator mass snectrometry) |
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| Research Abstract |
Iodine is an essential nutrient element, because of its role in the thyroid gland of human and animals. However, geochemical and environmental behavior of this element is not sufficiently known. For example, iodine-rich brines, which contain iodine more than 1000 times higher than that of seawater, occure in several places in Japan, although their origins are not well understood. From a radiological viewpoint, considerable attention should be paid to the levels and behavior of radioiodine, specifically ^<129>I (half-life 16 million years), in the environment. We have studied sensitive analytical methods for ^<129>I and stable iodine and applied them to biogeochemical systems. Microbial activities on the accumulation and transformation of iodine species were also studied. Main results obtained are as follows:
(1) Concentrations of iodine and some other elements in underground waters(including brines)varied very widely from<0.01 to 140 ppm. Analytical results obtained from pore waters in Nankai-Trough sediments associated with methane. In order to determine the ages of iodine in such brine samples using ^<129>I systematics, ^<129>L/^<127> I ratios in selected samples were measured by AMS.
(2) Concentrations of ^<129>I in surface soil samples obtained far from different places in Japan are in the range 1.4×10^<-5>- 4.5×10^<-3> Bq/Kg. Markedly higher ^<129>I concentrations were observed in surface soil samples collected from Tokai-mura, where a spent fuel reprocessing plant is located. The ^<129>I was found to be accumulated in surface soil layers.
(3) Experiments using different types of microorganisms showed that there are bacteria participating in the transformation of iodine species, e. g. iodide to methyl iodide, iodate to iodide, iodide to molecular iodine. We also found iodine accumulating bacteria.
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