Alain Fouepe

Institut de Recherches Géologiques et Minières

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Takeshi Ohba

Tokai University

Joseph Victor Hell

Institut de Recherches Géologiques et Minières

Minoru Kusakabe

University of Toyama

Wilson Y. Fantong

Institut de Recherches Géologiques et Minières

Romaric Ntchantcho

Institut de Recherches Géologiques et Minières

Gregory Tanyileke

Institut de Recherches Géologiques et Minières

Katsuya Kaneko

Kobe University

B. Ketchemen-Tandia

University of Douala

George Elambo Nkeng

National Advanced School of Public Works

Kazuto Saiki

Osaka University

Cooperative Institutions

Institut de Recherches Géologiques et Minières

Université de Yaoundé I

University of Douala

Ministry of Scientific Research and Innovation

Federal Institute for Geosciences and Natural Resources

The University of Tokyo

University of Toyama

Tokai University

Tokyo Institute of Technology

Graduate School USA

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Contribution of methane to total gas pressure in deep waters at lakes Nyos and Monoun (Cameroon, West Africa)

GEOCHEMICAL JOURNAL (2013)

Issa Takeshi Ohba Wilson Y. Fantong Alain Fouepe Boris Chako Tchamabé

A portable gas-analyser was used to perform on-site gas analysis at lakes Nyos and Monoun. Results were used to evaluate the effect of the dissolved CH4 on the gas saturation level. Although CH4 represents marginal proportion in term of the total gas concentration (~2.2 mol % in Lake Monoun and ~0.6 mol % in Lake Nyos) it contributes ~37% and ~19% to the total dissolved gas pressure and ~23% and ~13% to saturation level in lakes Monoun and Nyos respectively. The risk due to CH4 increase is evaluated and monitoring and surveillance measures proposed. Because methane is less more soluble than carbon dioxide, its increase may accelerate saturation of the lake waters with dissolved gas making gas eruptions more frequent. It is therefore recommended to regularly monitor the lakes in order to assess CH4 evolution for hazard mitigation purposes. If future monitoring surveys confirm current CH4 increase, a device to extract deep rich-gas water must be experimented and put in place without delay.

Saturation (graph theory)

Methane gas

Gas pressure

10.2343/geochemj.2.0250

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Citations (13)

Shallow groundwater quality evolution after 20 years of exploitation in the southern Lake Chad: hydrochemistry and stable isotopes survey in the far north of Cameroon

Environmental Earth Sciences (2019)

Mohammad Bello B. Ketchemen-Tandia Bertil Nlend Frédéric Huneau Alain Fouepe

δ18O

Environmental isotopes

10.1007/s12665-019-8494-7

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Citations (20)

Vertical change in transparency of water at Lake Nyos, a possible indicator for the depth of chemocline

Journal of African Earth Sciences (2019)

Kazuto Saiki Katsuya Kaneko Takeshi Ohba Romaric Ntchantcho Alain Fouepe

Chemocline

Geophone

10.1016/j.jafrearsci.2019.02.008

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Citations (3)

Temporal pollution by nitrate (NO3), and discharge of springs in shallow crystalline aquifers: Case of Akok Ndoue catchment, Yaounde (Cameroon)

African Journal of Environmental Science and Technology (2013)

Wilson Y. Fantong Alain Fouepe Serges L. Bopda Djomou Hycinth S. Banseka Katsuro Anazawa

Less than 30% of households in Yaounde have direct access to pipe-borne water. It is important to generate a time series on quality and quantity of spring water, which is an alternative source of water. Accordingly, temporal variation of NO3 and dissolved oxygen (DO), lag time of springs recharge by rainfall, discharge of springs and annual discharge of water from the Akok-Ndoue catchment was evaluated. Eleven springs, 3 wells and 1 rain gauge were investigated for 24 months. Flow rate, electrical conductivity, water temperature, DO, pH, water level in wells, rainfall amount and major ions were measured monthly. Temporally, the months of March, April, September and October are when the springs and shallow wells are polluted by NO3. Spatially, springs at lower altitudes are also susceptible to NO3 pollution. Rainfall depths from 125 to 275 and >275 mm/month recharge springs after 1 to 2 months, and less than 1 month, respectively. Moreover, when rainfall amount is <100 mm, it takes about 2 months for the discharge of the springs to decrease to less than 0.2 l/s. The springs were of category 5-7 on the Meinzer’s classification scheme. Recharge was estimated at 50 mm/year and the springs showed a wide range of variability with discharge that decreased with increase in elevation. Key words: Springs, Spatio-temporal pollution, discharge, crystalline aquifer, Yaounde, Cameroon

Water discharge

Discharge

10.5897/ajest13.1421

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Citations (8)

Mass balance of nitrogen and potassium in urban groundwater in Central Africa, Yaounde/Cameroon

The Science of The Total Environment (2016)

Robert Kringel Andrea Rechenburg D. Kuitcha Alain Fouepe S. Bellenberg

Mass flow of nutrients from innumerous latrines and septic tanks was assessed to best describe the groundwater quality situation in the urban environment of Yaounde. 37 groundwater samples were taken at the end of dry season 2012 and analysed for nutrient related (NO3−, NH4+, NO2−, K+, Cl−, HPO42 − and TOC) and physico-chemical ambient parameters. A survey on waste water discharge close to water points constrained point sources from sanitation. The results showed that the median of nitrate concentration exceeds the WHO limit. We realized that EC increases from the geogenic background to very high levels in the urban area within short distance, suggesting anthropogenic input. Dug wells showed nitrate and ammonium in equivalent concentrations, indicating incomplete nitrification and mandating their inclusion into water type classification. The mass turnover of nutrients in urban groundwater scales high in comparison to national statistical figures on fertilizer import for 2012. A mass N,K balance for infiltration water overestimates observed concentrations by a factor of 4.5. The marked balance gap is attributed to dynamic non-equilibrium between input and output. Unresolved questions like a) urban sanitation, b) hygiene & health and c) environmental protection urgently call for closing the nutrient cycle. In the light of Cameroonian strategies on rural development, tackling the groundwater nutrient, urban agriculture, food — NEXUS might partially restore urban and periurban ecosystem services under economical constraints and thus improve living conditions.

10.1016/j.scitotenv.2015.12.090

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Citations (52)

Variation of hydrogeochemical characteristics of water in surface flows, shallow wells, and boreholes in the coastal city of Douala (Cameroon)

Hydrological Sciences Journal (2016)

Wilson Y. Fantong Brice Tchakam Kamtchueng B. Ketchemen-Tandia D. Kuitcha Joséphine Ndjama

Groundwater is used by 3 million inhabitants in the coastal urban city of Douala, Cameroon, but comprehensive data are too sparse for it to be managed in a sustainable manner. Hence this study aimed to (1) assess the potability of the groundwater; (2) evaluate the spatial variation of groundwater composition; and (3) assess the interaction and recharge mechanisms of different water bodies. Hydrogeochemical tools and methods revealed the following results in the Wouri and Nkappa formations of the Douala basin, which is beneath Douala city: 30% of water samples from hand-dug wells in the shallow Pleistocene alluvium aquifer were saline and highly mineralized. However, water from boreholes in the deeper (49–92 m depth) Palaeocene aquifer was saline-free, less mineralized and potable. Water in the shallow aquifer (0.5–22 m depth) was of Na+-K+-Cl−-NO3− type and not potable due to point source pollution, whereas Ca+-HCO3− unpolluted water dominates in the deeper aquifer. Water in the deep and shallow aquifers indicates the results of preferential flow pass and evaporative recharge, respectively. Possible hydrogeochemical processes include point source pollution, reverse ion exchange, remote recharge areas and mixing of waters with different chemical signatures.EDITOR D. Koutsoyiannis ASSOCIATE EDITOR M.D. Fidelibus

Saline water

10.1080/02626667.2016.1173789

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Citations (21)

A new method to determine dissolved CO ₂ concentration of lakes Nyos and Monoun using the sound speed and electrical conductivity of lake water

Geological Society London Special Publications (2015)

Mitsuhisa Sanemasa Kazuto Saiki Katsuya Kaneko Takeshi Ohba Minoru Kusakabe

Abstract A new method to measure the CO 2 concentration in lakes Nyos and Monoun using sound speed (SS) and electrical conductivity (EC) of the lake water was developed. Limnic eruptions at lakes Monoun and Nyos in Cameroon, characterized by a risk related to possible sudden release of magmatic CO 2 gas dissolved in the lake water, occurred in 1984 and 1986 respectively, killing about 1800 residents. CO 2 monitoring of the lake waters was initiated to prevent further disasters. Classical methods of CO 2 measurement, which require chemical analysis of water samples, are not suitable for frequent and multi-point monitoring. Inspired by the method of measuring salt concentration using SS, we obtained data for dissolved CO 2 (CO 2 (aq) ) assuming the following formula Δ v = k 1 [ C O 2 ( aq ) ] + k 2 [ HCO 3 − ] , where Δ v is additional SS due to dissolved ions and k 1 and k 2 are coefficients determined through experiments. The coefficient k 1 was determined with temperature T (°C) dependence as 0.0323–0.000523 T [l m s −1 mmol −1 ]. k 2 was estimated to be 0.132 at Lake Nyos and 0.0930 at Lake Monoun. Once k 1 and k 2 values are obtained, [CO 2(aq) ] and [ HCO 3 − ] are calculated using the SS, T and EC.

Speed of Sound

10.1144/sp437.5

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Citations (6)

Hydrogeochemistry of low agricultural soil yield in Sahelian and sub-tropical watersheds, Northern Cameroon

Journal of African Earth Sciences (2022)

Wilson Y. Fantong Gergino Y. Chounna Therese L. L. Jokam Nenkam Alain Fouepe Ernest Chi Fru

Bedrock

Biogeochemical Cycle

10.1016/j.jafrearsci.2022.104823

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Citations (2)