EFFORTS to prevent the release of deadly clouds of gas from two African lakes appear to be failing. Some 1800 people died of asphyxiation during the 1980s when Lakes Nyos and Monoun in Cameroon suddenly released clouds of carbon dioxide over the surrounding countryside.
In an effort to vent the gas at a safe, controlled rate, a pipe was placed in Lake Nyos in 2001 and Lake Monoun in 2003. But the pipes are not working fast enough, says George Kling at the University of Michigan, whose team has analysed 12 years鈥� worth of data on the lakes. Although the pipes are gradually reducing CO2 levels in the water, the rate is dropping as gas concentrations near the pipe inlets fall. Meanwhile, ongoing volcanic activity means other parts of the lake are constantly being recharged (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0502274102).
Kling predicts that the pipe in Lake Monoun will only cut the amount of gas in the lake by 30 per cent. At that point the rate of removal will have fallen to the rate at which gas is recharged. In Lake Nyos, just 25 per cent of the gas will be removed by 2015.
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Extra pipes are needed, Kling says. 鈥淥ur model indicates that 75 to 99 per cent of the gas remaining would be removed by 2010 with two pipes in Monoun and five pipes in Nyos, substantially reducing the risks.鈥�
