The Lake Nyos gas disaster: chemical and isotopic evidence in waters and dissolved gases from three Cameroonian crater lakes, Nyos, Monoun and Wum

Kusakabe, Minoru; Ohsumi, Takashi; Aramaki, Shigeo

doi:10.1016/0377-0273(89)90056-5

Cited by 97 publications

(71 citation statements)

References 18 publications

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“…Temperature and gas content data are taken from Figs. 1 and 2 and Tables 1 and 2; dissolved salt data for recent years are unpublished, but are similar to previous reports (7,15,17).…”

Section: Methodssupporting

confidence: 87%

Degassing Lakes Nyos and Monoun: Defusing certain disaster

Kling

Evans

Tanyileke

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

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106

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Since the catastrophic releases of CO2 in the 1980s, Lakes Nyos and Monoun in Cameroon experienced CO 2 recharge at alarming rates of up to 80 mol͞m 2 per yr. Total gas pressures reached 8.3 and 15.6 bar in Monoun (2003) and Nyos (2001), respectively, resulting in gas saturation levels up to 97%. These natural hazards are distinguished by the potential for mitigation to prevent future disasters. Controlled degassing was initiated at Nyos (2001) and Monoun (2003) amid speculation it could inadvertently destabilize the lakes and trigger another gas burst. Our measurements indicate that water column structure has not been compromised by the degassing and local stability is increasing in the zones of degassing. Furthermore, gas content has been reduced in the lakes Ϸ12-14%. However, as gas is removed, the pressure at pipe inlets is reduced, and the removal rate will decrease over time. Based on 12 years of limnological measurements we developed a model of future removal rates and gas inventory, which predicts that in Monoun the current pipe will remove Ϸ30% of the gas remaining before the natural gas recharge balances the removal rate. In Nyos the single pipe will remove Ϸ25% of the gas remaining by 2015; this slow removal extends the present risk to local populations. More pipes and continued vigilance are required to reduce the risk of repeat disasters. Our model indicates that 75-99% of the gas remaining would be removed by 2010 with two pipes in Monoun and five pipes in Nyos, substantially reducing the risks.gas disaster ͉ limnology ͉ natural hazard V olcanoes can release massive amounts of CO 2 at the Earth's surface (1), and in the last 20 years natural lakes with CO 2 -rich waters have also proven to be highly dangerous (2-4). Before the nature of these gas-charged lakes was understood, sudden releases of large clouds of CO 2 gas from Lakes Nyos and Monoun in Cameroon, in 1986 and 1984, respectively, claimed the lives of Ϸ1,800 people by asphyxiation (2, 3). The gas originates from magma at great depth, but dissolves into groundwater near the Earth's surface. The CO 2 -charged water enters the lake bottoms through springs (2, 4) and accumulates in the deep, stratified lakes. Although the timing of sudden releases may be modulated by climate (5), it is now clear that continuous gas recharge into the lakes ensures a natural cycle of repeating disasters (6-8).Unlike most natural hazards, the certainty of future disasters at these lakes can be averted by directed mitigation. The solution is to degas the lakes through controlled piping of gas-rich bottom water to the lake surface where the gas is released harmlessly to the atmosphere in low concentrations. Once flow in a pipe is mechanically initiated, lift is provided by the buoyant rise of bubbly water and the process becomes spontaneous and selfsustaining. Theoretical models (9-11) indicated that this mitigation was feasible, and pumping began at Lake Nyos in 2001 and Lake Monoun in 2003 (12). However, questions still arose about the safety of this hazard miti...

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“…Temperature and gas content data are taken from Figs. 1 and 2 and Tables 1 and 2; dissolved salt data for recent years are unpublished, but are similar to previous reports (7,15,17).…”

Section: Methodssupporting

confidence: 87%

Degassing Lakes Nyos and Monoun: Defusing certain disaster

Kling

Evans

Tanyileke

et al. 2005

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

106

108

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“…Comparison of the 1988 results with our previous field surveys in October 1986 (Kusakabe et al 1989) and October-November 1986(Tietze 1987 shows that temperature and concentrations of CO2 and other dissolved ionic species are increasing in the bottom water ). Because estimates of the CO, flux to the lake are of primary importance in evaluating the potential for a future gas release, tentative estimates of CO2 flux have been made based on the 3He-temperature ) and CO,-conductivity relationships ) obtained during our 1988 survey.…”

mentioning

confidence: 58%

“…2) was attached to accommodate the exsolved gas (Kusakabe et al 1989). Water was collected close to the French buoy, where the maximum depth observed was 208 m.…”

Section: Methodsmentioning

confidence: 99%

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An estimate of CO₂ flux in Lake Nyos, Cameroon

Nojiri

Kusakabe

Tietze

et al. 1993

Limnology & Oceanography

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A hstractAn outburst of lethal gas from Lake Nyos, Cameroon, killed more than 1,700 people on 2 1 August 1986. The surveys carried out so far indicate that a considerable portion of the CO, dissolved in the lake was released to the atmosphere and asphyxiated the people. We revisited the lake in December 1988. The conductivity-temperature-depth profiler (CTD) measurements and chemical analysis of the lake water revealed that temperature, total dissolved solids (TDS), and CO, content of the bottom water increased in parallel fashion, especially in the bottom layer, during the preceding 25 months. The result supports the view thdt CO1 is being supplied to the lake bottom in the form of warm, CO,-charged, mineralized water. From the increments of temperature and CO, during the period, fluxes of heat and CO, were estimated to be 0.43 MW and 1 .O Mmol yr I. The CO1 flux is large enough to saturate the lake's hypolimnion within -30 yr. In the 1988 survey, the very bottom layer of the lake was estimated to be close to saturation with CO,. Using the CO,-TDS-Si relationship and temperature dependence of the solubility of amorphous silica, we estimated the chemical composition of the warm, mineralized water; these estimates suggest the existence of a CO,-saturated fluid below the sedimentary cover.

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“…Changes in Lake Nyos bottom water chemistry since the gas release can be measured, but chemical evolution of the lake prior to the event must be inferred. (Kusakabe et al, 1989, this issue); springs issuing from granitic rocks above Lake Nyos; rain in Cameroon and surface water before the event (Kling, 1987b); spring water associated with ultramafic rocks (Hem, 1970); and leachates from experimental weathering of basalts (Siever and Woodford, 1979).…”

Section: Sodium MMmentioning

confidence: 99%