2021 Fiscal Year Final Research Report
Monitoring of temperature in hydrothermal reservoir using gaseous elemental mercury
| Project/Area Number |
18H01290
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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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| Review Section |
Basic Section 17030:Human geosciences-related
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
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| Co-Investigator(Kenkyū-buntansha) |
大場 武 東海大学, 理学部, 教授 (60203915)
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| Project Period (FY) |
2018-04-01 – 2022-03-31
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| Keywords | 火山 / 水蒸気噴火 / 気体単体水銀 / 側噴火 / 草津白根山 |
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| Outline of Final Research Achievements |
The relation between mercury emission rates (φ) and temperature at the site RH was found to satisfy the Arrehenius equation, however, φ changes depending on the underground temperature (Tg), not the chamber temperature (Tc). Although ln(φ) changes linearly against Tc^-1 (Arrehenius equation), we can clearly see that the intercepts of the Arrehenius plot is different for the data recorded on morning (temperature increased with time) and evening (temperature decreased with time). The mechanisim for the difference in intercept is interpreted as a delayed response of the subsurface temperature (Tg) to the change in chamber temperature (Tc). On the basis of the consideration using the heat conduction equation, mercury emission rates (φ) changes depending on the ground temperature at a depth of two centimeters. Using the empirical relation obtained in this study, we modified the spatial distribution and temporal changes in GEM emission rate from volcanoes.
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| Free Research Field |
火山化学
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| Academic Significance and Societal Importance of the Research Achievements |
活火山で発生する水蒸気噴火は，周辺 1-2 km 以内に大きな噴石を落下させ，そこに滞在している登山者や事業者に甚大な被害を与える．本研究では，水蒸気噴火に先行する地下温度上昇を，地表において気体水銀放出率を観測することで検出する新しい方法を構築した．本研究の主たる成果は，水銀放出率に影響する地表面付近の温度効果を定量的に明らかにしたことである．この知見に基づき，火山活動としての水銀放出を高い信頼性のもとでモニタリングが可能となる．今後は草津白根山などの火山において実際の観測に適用することで，本手法の有効性を実証的に検討する．
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