Graduate School of Oceanography University of Rhode Island Kingston R.I. 02881 U.S.A.
Disasters. 1988 Jun;12(2):131-46. doi: 10.1111/j.1467-7717.1988.tb00661.x.
Gas bursts from tropical crater lakes constitute a hitherto unrecognized natural hazard, which claimed 37 lives around Lake Monoun in 1984 and 1,746 lives in 1986 around Lake Nyos in Cameroon, west Africa. Studies of these events indicate that the lethal gas clouds were dominantly CO(2) which exsolved catastrophically from deep waters of the lakes, producing in the case of Lake Nyos a gas cloud of 1.94 times 10(6) tons CO(2) . Carbon-isotope data indicate a magmatic source of the carbon dioxide, but the geochemistry of deep water and gases does not support a sudden injection of volcanic gas from a deep source into the lakes. Rather, it is proposed that the gas bursts were preceded by gradual build-up of dissolved bicarbonate in deep waters, where anoxic conditions in enclosed and stagnant basins led to low pH and pCO(2) close to saturation. Steady input from the Earth's mantle to submerged mofettes or CO(2) -rich soda springs within the lakes is most likely the primary source of carbon dioxide. Lethal effects of the gas bursts are almost entirely due to CO(2) -induced asphyxia. A small percentage of victims awoke from coma one or two days after the event, but most died. Unusual skin lesions on about 5% of victims arose from the comatose state. It is shown that the mass of gas required to account for the lethal effects and observed gas clouds is an order of magnitude less than the potential gas yield from the lakes. In view of the lethal gas bursts from the small Cameroon lakes, the potential hazard of future gas bursts from other much larger density-stratified equatorial lakes must be seriously considered, particularly in Lake Kivu in east Africa, where methane and carbon dioxide gas content is higher by two to four orders of magnitude than that of the Cameroon lakes. A gas burst from Lake Kivu would form a carbon dioxide cloud up to 340 km(3) in volume and expansion of the exsolving gas from deep water to atmospheric pressure would correspond to an energy release equivalent to 8 megatons of explosive.
从热带火山口湖逸出的气体构成了一种迄今为止尚未被认识到的自然危害，1984 年蒙诺湖周围发生的事件导致 37 人死亡，1986 年喀麦隆西部尼奥斯湖周围的事件导致 1746 人死亡。对这些事件的研究表明，致命的气体云主要是 CO(2)，它从湖泊深处灾难性地逸出，在尼奥斯湖的情况下，产生了 1.94 倍 10(6)吨 CO(2)的气体云。碳同位素数据表明二氧化碳的岩浆源，但深水和气体的地球化学并不支持从深部源突然注入火山气体到湖中。相反，有人提出，气体爆发之前，深水中的碳酸氢盐逐渐积聚，而封闭和停滞的盆地中的缺氧条件导致 pH 值和 pCO(2)接近饱和。从地幔向湖中的淹没喷气孔或富二氧化碳苏打泉持续输入最有可能是二氧化碳的主要来源。气体爆发的致命影响几乎完全是由于 CO(2)引起的窒息。一小部分受害者在事件发生一到两天后从昏迷中醒来，但大多数人死亡。大约 5%的受害者身上出现了不寻常的皮肤损伤，这是从昏迷状态中产生的。结果表明，为了说明致命效应和观察到的气体云所需的气体质量比湖泊潜在的气体产量小一个数量级。鉴于喀麦隆小湖发生的致命气体爆发，必须认真考虑未来其他更大密度分层赤道湖泊发生气体爆发的潜在危险，特别是在东非的基伍湖，那里的甲烷和二氧化碳气体含量比喀麦隆的湖泊高两个到四个数量级。基伍湖的气体爆发将形成一个高达 340 公里(3)的体积的二氧化碳云，从深水中逸出的气体的膨胀到大气压力将相当于 800 万吨爆炸的能量释放。
