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Continuous monitoring of water chemistry of Lake Nyos using an automated CDT and satellite data

Research Project

Project/Area Number 13573013
Research Category

Grant-in-Aid for Scientific Research (B)

Allocation TypeSingle-year Grants
Section海外学術
Research Field 地球化学
Research InstitutionOkayama University

Principal Investigator

KUSAKABE Minoru  Institute for Study of the Earth's Interior, Professor, 固体地球研究センター, 教授 (20015770)

Co-Investigator(Kenkyū-buntansha) YOSHIDA Yutaka  Yoshida Engineer Office, General Manager, 所長
SATAKE Hiroshi  Faculty of Science, Toyame University, Professor, 理学部, 教授 (40134994)
NAGAO Keisuke  Graduate School of Science, University of Tokyo, Professor, 大学院・理学系研究科, 教授 (40131619)
Project Period (FY) 2001 – 2002
Project Status Completed (Fiscal Year 2002)
Budget Amount *help
¥13,900,000 (Direct Cost: ¥13,900,000)
Fiscal Year 2002: ¥4,300,000 (Direct Cost: ¥4,300,000)
Fiscal Year 2001: ¥9,600,000 (Direct Cost: ¥9,600,000)
KeywordsCameroon / Lake Nyos / gas disaster / CTD / chemical and isotopic compositions / temperature structure / density structure
Research Abstract

Lakes Nyos and Monoun (Cameroon) exploded in the mid 1980s killing about 1800 people. At these lakes, temperature, total dissolved ions, and CO2 concentration in the bottom water have been steadily increasing since the last explosions. Thus the lake explosion may recur unless CO_2 concentration is lowered. Currently gas removal is going on using a degassing system that was installed in January 2001 at Lake Nyos and February 2003 at Lake Monoun.
In the present investigation, we determined (1) the spatial distribution of CO_2 and variation with time in the total amount of CO_2 in the lakes, and (2) the changes in the physical structure of the lakes, I.e., temperature, chemical composition, and density of the lakes. We made a detailed CTD observation at Lake Nyos along N-S and E-W cross sections. This enabled us to construct a three-dimensional distribution of temperature and chemistry for the first time. It was found that the lakes show strong stratification and that the artificial degassing did not give any substantial change in the chemical and physical structures of the lakes except for enrichment of chemical species in surface water. This was caused by addition of degassed deep water at the surface.
The highest ( 350 mmol/kg) is observed below 190 m depth a Nyos. The CO_2 recharge rate in the deep waters is 100 Mmol/yr, at least as high as in the previous ten years. The highest ratios of ^3He/^4He (8.1x10^<-6>) and ^<40>Ar/^<36>Ar (600), suggestive of magmatic affiliation. At monoun, the highest CO_2 concentration of 160 mmol/kg is observed between 65-95 m depth. The lakes may spontaneously explode in the near future if CO_2 saturation is reached at any depth. However, gas explosion at these lakes can occur at any time upon introduction of external forcing such as a landslide.

Report

(3 results)
  • 2002 Annual Research Report   Final Research Report Summary
  • 2001 Annual Research Report
  • Research Products

    (15 results)

All Other

All Publications (15 results)

  • [Publications] 日下部 実: "カメルーン・ニオス湖における湖水爆発の原因とガス抜きによる再発防止対策の開始"化学と教育. 49. 619-622 (2001)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] Kusakabe, M.: "A simple method for sampling total dissolved carbonate in carbonate-rich natural waters and CO_2 preparation for δ^<13>C determination"Geochemical Journal. 35. 459-464 (2001)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] Aka, F.: "Noble gas isotopic compositions and water/gas chemistry of soda springs from the Islands of Bioko, Sao Tome and Annobon along with Cameroon Volcanic Line, West Africa"Applied Geochemistry. 16. 323-338 (2001)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] 日下部 実: "カメルーン・ニオス湖ガス災害と地球化学"地球化学. 36. 137-147 (2002)

    • Description
      「研究成果報告書概要(和文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] Kusakabe, M.: "Causes of the limnic eruption at Lake Nyos, Cameroon, and its mitigation by means of artificial degassing"Kagaku-to-Kyoiku (Chemistry and Education in English). 49. 619-622 (2001)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] Kusakabe, M.: "A simple method for sampling total dissolved carbonate in carbonate-rich natural waters and CO_2 preparation for δ^<13>C determination."Geochemical Journal. 35. 459-464 (2001)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] Aka, F.: "Noble gas isotopic compositions and water/gas chemistry of soda springs from the islands of Bioko, Sao Tome and Annobon along with Cameroon Volcanic Line, West Africa."Applied Geochemistry. 16. 323-338 (2001)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] Kusakabe, M.: "The Lake Nyos gas disaster and geochemistry."Chikyu-Kagaku (Geochemistry in English). 36. 137-147 (2002)

    • Description
      「研究成果報告書概要(欧文)」より
    • Related Report
      2002 Final Research Report Summary
  • [Publications] 日下部 実: "カメルーン・ニオス湖における湖水爆発の原因とガス抜きによる再発防止対策の開始"化学と教育. 49. 619-622 (2001)

    • Related Report
      2002 Annual Research Report
  • [Publications] Kusakabe, M.: "A simple method for sampling total dissolved carbonate in carbonate-rich Natural waters and CO_2 preparation for δ^<13> C determination"Geochemical Journal. 35. 459-564 (2001)

    • Related Report
      2002 Annual Research Report
  • [Publications] Aka, F.: "Noble gas isotopic compositions and water/gas chemistry of soda springs from the Islands of Bioko, Sao Tome and Annobon along with Cameroon Volcanic Line, West Africa"Applied Geochemistry. 16. 323-338 (2001)

    • Related Report
      2002 Annual Research Report
  • [Publications] 日下部 実: "カメルーン・ニオス湖ガス災害と地球化学"地球化学. 36. 137-147 (2002)

    • Related Report
      2002 Annual Research Report
  • [Publications] 日下部 実: "カメルーン・ニオス湖における湖水爆発の原因とガス抜きによる再発防止対策の開始"化学と教育. 49. 619-622 (2001)

    • Related Report
      2001 Annual Research Report
  • [Publications] M.Kusakabe: "A simple method for sampling total dissolved carbonate in carbonate-rich natural waters and CO_2 preparation for δ^<13>C determination"Geochem.Jour.. 35. 459-564 (2001)

    • Related Report
      2001 Annual Research Report
  • [Publications] Aka, F.T., Kusakabe, M.Nagao, K, Tanyileke, G.: "Noble gas isotopic compositions and water/gas chemistry of soda springs from the Islands of Bioko.Sao Tome and Annobon along with Cameroon Volcanic Line, West Africa"Applied Geochemistry. 16. 323-338 (2001)

    • Related Report
      2001 Annual Research Report

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Published: 2001-04-01   Modified: 2016-04-21  

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