Spain's 'killer lake' to be disarmed

A seemingly pretty lake in Huelva, Spain, is apparently the disguise of a potential mass killer, according to geochemists.

The lake is actually the flooded remains of an open-pit mine abandoned in the 1980s, and has large amounts of carbon dioxide trapped in and under the water. It's the only lake known in Europe with those conditions. In Africa there are a number, but they result from volcanic activity, not mining.

Under normal conditions, the CO₂ would remain at the bottom of the lake without a hazard. But according to geochemists at Spain's Institute of Geology and Mining, there is a risk that it could be released suddenly, by the collapse of a bank or a small earthquake. That could cause a sudden release of CO₂  that would displace oxygen and could kill hundreds. 1,700 died in an incident like that in Cameroon in 1986.

The institute is installing a pipe system to draw out and dissipate the carbon dioxide, similar to systems installed at a number of African lakes. A pipe is anchored at the bottom of the lake to draw water to the surface, where the gas can dissipate under controlled conditions. It's expected to take about 5 months to clear it all.