カメルーン・ニオス湖ガス災害に果たした湖の役割

概要

論文の詳細を見る
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 CO_2 (aq) and HCO_3^- with a substantial concentration of Fe^<2+> in deep waters. Stable isotopic compositions of carbon (δ^<13>C=-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 SO_4^<2-> argue against the volcanic gas injection hypothesis as a cause of the disaster. The gas bursts were caused by outgassing of CC_2-laden deep water which was displaced upward and effervesced near the surface, possibly triggered by an increased input rate of warmer, CC_2-charged groundwater from the bottom during the rainy season.
日本地球化学会の論文
1987-12-10