Controlled degassing of lakes with high CO₂ content in Cameroon: an opportunity for ecosystem CO₂-enrichment experiments

Summary

SUMMARY

In 1984 and 1986, massive eruptions of carbon dioxide from two lakes in Cameroon killed at least 1800 Cameroonian villagers. Countless head of cattle were also asphyxiated. Since then, measurements have shown that the amount of CO₂ still dissolved in these lakes is very high (20,000 tons and 500,000 tons at Monoun and Nyos, respectively). The danger of a future gas burst (the so-called “limnic eruption”) could be eradicated by drawing off dissolved CO₂. A gas-lift experiment at Lake Monoun in April 1992 allowed CO₂ to be released at a flow-rate of 15 to 150 l.s^-1 (STP), depending on the diameter of the pipe used. The large high grade CO₂ resource from these two west African lakes provides an exceptional opportunity to conduct large scale and long-term experiments on the effect of increased atmospheric CO₂ concentrations on biotic systems in the tropical region. A description of the planned experiments is presented.

INTRODUCTION

In several volcanic regions of the world, large amounts of gas containing mainly CO₂ are sporadically released. In some instances, the gas released may asphyxiate humans. In the last decade, this phenomenon has been reported in Indonesia (Le Guern, Tazieff & Faivre-Pierret, 1982), and later in Cameroon at lake Monoun in 1984 (Sigurdsson et al., 1987) and at Lake Nyos in 1986. These gas eruptions were all of nearly pure carbon dioxide of deep (mainly magmatic) origin, expanding from a near-surface reservoir.