Developments in Brief : Toxic Gas From Africa Lake Still Seen as Peril

Lake Nios in Cameroon, which last year suddenly released a cloud of carbon dioxide gas, asphyxiating more than 1,700 people, cannot be considered safe until the remaining gas is removed, a scientific study says.

“High concentrations of carbon dioxide remain dissolved in Lake Nios, representing a potential hazard until they can be safely lowered,” according to the report, made by an 11-member team of the U.S. Foreign Disaster Assistance office of the Agency for International Development. It was released last week at the annual conference of the U.S. Geological Society of America in Boulder, Colo. The team spent three weeks investigating the disaster in the west-central African nation.

The lake occupies a volcanic crater that was formed only a few hundred years ago, but underlying the lake is a volcanic pipe that serves as a conduit for the gradual upward flow of carbon dioxide from deep within the Earth.

“Over a long period of time, gas dissolved in ground water has been accumulating in the bottom water of the lake, creating a potential hazard,” the report said.

On Aug. 21, the gas bubbled out and formed a huge cloud that then flowed across adjacent land, killing people and livestock.

The team said there was no clear trigger that released the gas, but said any serious disruption in the stratified levels of water in the lake could have set it off.

The report recommended monitoring other lakes in the region that show high concentrations of dissolved carbon dioxide, and using huge pipes to bring water up from the lowest levels to release the built-up gas in a controlled manner.