Environmental modifications of Lake Nyos surface water by artificial degassing

Abstract

After the catastrophic release of CO2 gas from Lake Nyos in 1986, much emphasis has been put on the urgency of adopting an efficient strategy for reducing CO2 accumulation at depth, but the environmental impacts of the degassing activity have been mostly neglected. The degassing pipes are continuously releasing highly concentrated ferrous iron water to the surface of the lake. The lake surface, which once used to be a deep blue, has now changed into reddish brown, due to the formation of colloidal ferric iron. From December 2001 to January 2011, one degassing pipe transported 560 tons of iron as colloidal ferric iron per year, and after late 2011, three pipes have been transporting about 1100 tons per year. The degassing fountain contains highly concentrated calcium and magnesium other than iron resulting in enrichment of those substances. Although the colloidal ferric iron might have adverse effect on fish and/or other aqueous biota, the lake water remained safe for domestic water use.