1997 Fiscal Year Final Research Report Summary
Mechamism of Aoshio formation
| Project/Area Number |
08680595
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
環境保全
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| Research Institution | The University of Tokyo |
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Principal Investigator |
NANBA Kenji The University of Tokyo , Graduste School of Agricultural and Life Sciences, Assistant Professor, 大学院・農学生命科学研究科, 助手 (70242162)
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| Co-Investigator(Kenkyū-buntansha) |
FURUYA Ken The University of Tokyo, Graduste School of Agricultural and Life Sciences, Asso, 大学院・農学生命科学研究科, 助教授 (30143548)
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| Project Period (FY) |
1996 – 1997
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| Keywords | aoshio / anoxic / Hamana / Tokyo Bay / Suigetsu |
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| Research Abstract |
Aoshio (milky blue-green water) is coloration of water caused by colloidal sulfur which derives from upwelling of coastal subsurface water rich in sulfide ion. However, it is general that transparent water containing sulfide is observed as surface water after the upwelling except Tokyo Bay. It means oxidation reaction is faster in aoshio formation. Then, hypothesizing that heavy metal ion might catalyze in the sulfide oxidation, laboratory assay experiments were attempted to elucidate what element contributes in the reaction of hydrogen sulfide and oxygen in artificial sea water. Initial 20 minuters in the reaction could be expressed as a 3 order equation derivative of expected reaction. Fe and Ni were the most potent catalysts according to the velocity constant among Mn, Cr, Co, Zn, Pb, Cu, Cd, and Al. Water sampled in Tokyo Bay had similar catalytic effects and possible catalysts were detected in the water. The results suggested that hydrogen sulfide oxidation in aoshio formation is catalyzed by Ni and Fe.
Although aoshio is not observed, a coloration similar to aoshio may exist in middle layr where oxygen and sulfide encounter. By the trial to detect this middle layr aoshio with in situ photometric equipments, turbidity maximum and associated layr of photosynthetic bacteria were observed in two brackish lakes where aoshio has not been known but transparent anoxic water is observed.photosynthetic bacteria were considered to play some role in aoshio prevention. And the group composition and the biomass of photosynthetic bacteria were suggested to be important in aoshio formation by simple colorimetry newly developed to quantify photosynthetic bacteria.
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Research Products
(2 results)
