Outburst of carbon dioxide from Lake Nyos, Cameroon

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  • カメルーン・ニオス湖ガス災害に果たした湖の役割
  • カメルーン ニオスコ ガス サイガイ ニ ハタシタ ミズウミ ノ ヤクワリ

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Outbursts of a large volume of carbon dioxide took place on 21 August 1986 at Lake Nyos, Cameroon, leading more than 1700 lives to death by asphyxiation. Geochemical and limnological survey made some 50 days after the disaster revealed that the lake water was still stratified with respect to temperature, chemistry and density except a very surface layer. The dissolved species were overwhelmingly dominated by CO2 (aq) and HCO3- with a substantial concentration of Fe2+ in deep waters. Stable isotopic compositions of carbon (δ13C=-3‰) and helium (5.7 times the atmospheric 3He/4He ratio) strongly indicate a mantle origin of the gases. Very low concentrations of Cl- and SO42- argue against the volcanic gas injection hypothesis as a cause of the disaster. The gas bursts were caused by outgassing of CO2-laden deep water which was displaced upward and effervesced near the surface, possibly triggered by an increased input rate of warmer, CO2-charged groundwater from the bottom during the rainy season.


  • Chikyukagaku

    Chikyukagaku 21 (2), 39-47, 1987

    The Geochemical Society of Japan

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