NYOS-MONOUN DEGASSING PROJECT (NMDP)

Advisory Committee Report

Report of the Meeting Held at the Institut de Physique du Globe, Paris, France, 19-20 March 2000

Committee Members:

Alain Bernard (Belgium), Bill Evans (U.S.A.), Michel Halbwachs (France), George Kling (Chair, U.S.A.), Minoru Kusakabe (Japan), Jean-Christophe Sabroux (France), Greg Tanyileke (Cameroon), Klaus Tietze (Germany). Participants: Yutaka Yoshida (Japan)

EXECUTIVE SUMMARY

Two disasters at Lakes Nyos and Monoun in Cameroon in the 1980s resulted in the deaths of about two thousand people. The loss of cattle and farmland and the resettlement of another two thousand survivors, now refuges from their homes for almost 14 years, has brought much suffering to the people of Cameroon. The disasters occurred when clouds of carbon dioxide gas that were stored in the lakes were suddenly released, suffocating everything in their paths. Both lakes still contain dangerous and ever increasing amounts of gas. Scientists have proposed and tested a method to remove the gas in a controlled manner by pumping through pipes inserted in the lakes. An international Advisory Committee for the Nyos-Monoun Degassing Project (NMDP, coordinated by the Cameroonian government) met in March 2000 to evaluate the scientific and technical information about the lakes and the plans to eliminate the hazards. The Committee's report recommends a single, unified plan regarding the degassing operation, safety and security issues, and the education and training required by the large-scale degassing and hazard mitigation of the lakes.

I. INTRODUCTION

History of the NMDP Advisory Committee

In 1987, just following the 1986 gas disaster at Lake Nyos, the first International UNESCO Conference on the disaster was held in Yaounde, Cameroon. A group of scientists attending this conference created an organization named the International Working Group on Crater Lakes (IWGCL). The purposes of IWGCL at that time were to exchange scientific information about the gas disasters, to coordinate the follow-up field work that was planned by those interested in these hazards, and to organize scientific meetings as a forum for further studies. In 1990 the first official meeting of the IWGCL was held in Nancy, France. At this meeting a consensus was reached regarding the causes of the gas disasters and the strategy for reducing the hazards by gas removal, and a letter to this effect was published in the journal Nature (v.348, p.201, 1990). A second international meeting was held in 1992 in Paris, France, and included not only scientists but also engineers interested in the specific technologies of degassing. Again, a consensus was reached on the scientific explanations for these events and on the technical means of a degassing project. After this meeting, and a similar conference held in Misasa, Japan in 1992, the IWGCL was expanded and received the status of Commission on Volcanic Lakes (CVL) in 1993, as granted by the International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI).

Between 1992 and 1995, the field demonstration projects for degassing that were carried out in Cameroon, and the proposals for degassing projects presented to various funding agencies, have followed the general consensus reached during the two meetings in France attended by members of the CVL. Once the field tests showed that controlled degassing was possible, in 1997 the CVL worked to establish an international committee to help coordinate and advise any future degassing efforts. This committee, named the NMDP Advisory Committee (Nyos-Monoun Degassing Project), is composed of 8 members from six countries, as listed above.

In October of 1999 the Cameroonian government formed an Inter-Ministerial Committee that is responsible for all degassing efforts on Lakes Nyos and Monoun. Shortly after that, the Inter-Ministerial Committee requested an update on the scientific and technical aspects of degassing from the NMDP Committee. The response of the NMDP Committee is contained in this report, which summarizes the discussions held at a meeting in Paris, France in March of 2000.

Current Status of the Lakes

It is important to know the current gas content of the lakes, and how the gas content is changing. As long as the lakes contain large quantities of dissolved gas they could potentially release lethal amounts of gas without warning. A key factor in estimating the likelihood of a gas burst is the degree of gas saturation (the ratio of gas pressure to hydrostatic pressure) at various depths in the lake. Several different methods have been used to measure the gas content, and all methods show good agreement and have established that the gas pressures in the lakes are high and are steadily increasing.

On the basis of the last field results available from 1999, in Lake Nyos there has been a gas pressure increase at all depths below 170 m compared to previous measurements. The largest increases have occurred in the bottom 20 m of the lake. Gas pressure at lake bottom exceeds 13 bar, which represents just over 60% of the saturation value based on an ambient hydrostatic pressure of 21 bars. In Lake Monoun gas pressure has increased in waters below 60 m depth and now reaches about 83% of the saturation pressure at that depth. Fortunately, the rate of pressure increase in Lake Monoun is less than the rate of increase in Lake Nyos. The fact that present day gas saturation is less than 100% does not indicate that the lakes are safe. Any large disturbance of the water column such as a landslide, rockfall, or violent storm could trigger a release of the gas remaining in these lakes at any time.

Current Status of International Projects and Funding

The scientific study of these gas-charged lakes has a long history, due mainly to projects supported by German, French, American, Japanese, and British governments beginning after 1986. A series of technical test projects aimed at degassing the lakes began in 1992 at Lake Monoun and was continued in 1995 at Lake Nyos (led by M. Halbwachs). From 1986 on, and especially after the success of the test projects, larger proposals for full-scale degassing of the lakes were submitted by German (Tietze, 1986-7), French (Halbwachs et al. 1995-6), and Japanese (Kusakabe et al. 1997-8) scientists. Although the entire, full-scale proposals were not realized, work on the lakes continued. The eruption of Mt. Cameroon in spring of 1999 led to an increased international awareness of the natural hazards in Cameroon, and at that time the U.S. government requested a proposal to work on the hazards of the lakes. This U.S. proposal (including principal investigators from Cameroon, France, Japan, and the U.S.) was funded by the Office of Foreign Disaster Assistance (OFDA) in late 1999. Shortly after this the French Embassy signed a contract with the Cameroonian Ministry MINREST for the degassing, to be coordinated with additional funds from the Cameroonian government. In addition, the Cameroonian Inter-Ministerial Committee, which has the overall responsibility for all degassing efforts, has committed funds toward the necessary infrastructure such as road improvement, construction of heliport, observatory, and storehouse buildings at both lakes, vehicles and other transportation including boats, as well as other logistical costs. The current financial support available is sufficient to install the initial pipes and begin degassing operations in both lakes, although further funds will be necessary to install the total number of pipes required to safely reduce gas levels in the lakes within ~5 years.

II. DEGASSING OPERATION

Short Term

In the short term the main objective is to install pipes that will remove gas at a rate that is faster than the natural rate of gas recharged into the lakes each year. This will insure at a minimum that the gas pressures are gradually reduced, and that the danger of another gas burst is reduced. The NMDP Committee recommends a single degassing plan which incorporates all presently available resources from the Cameroonian and international participants. This plan will use at least one pipe in Lake Monoun (up to 2 or 3 total) and one pipe in Lake Nyos initially. The technical details of the plan are presented in Section VIII below.

The timetable for this plan is to construct the necessary equipment, test the equipment, and ship the equipment and supplies to arrive in Cameroon no later than 1 October 2000. The installation will proceed immediately and will be completed by the beginning of February 2001. Successful completion will require: (1) Customs clearance for equipment and supplies arriving in Cameroon; (2) Improved roads to both Lakes Monoun and Nyos; (3) Transportation to the lakes of materials and personnel by truck and 4-wheel drive vehicle; (4) Construction of a storeroom building for supplies and technical work at each lake; in addition the electrical lines should be extended to Lake Monoun; and (5) Military assistance and SCUBA equipment for security and safety at each lake. This includes having an observer on site, closing the road at the inlet of Lake Monoun, restricting fisherman from Lake Monoun, and compensating the fisherman while they are unable to work during the initial degassing.

Long Term

In the long term the main objective is to remove the gas from the waters in both lakes. This will result in elimination of future gas releases from gas stored in the bottom waters of the lakes. As with the short-term plan, this long-term plan will require a single, unified project that will fit into the overall program of the Inter-Ministerial Committee. This project will increase the number of pipes in order to reduce the gas pressures to safe levels as quickly as possible. We will employ the same techniques used in the short-term plan. Given our current scientific and technical understanding, this project will have a time frame of up to 5 years. It is essential that any proposals to national or international funding agencies be incorporated into this unified project.

Based on our experience, it is imperative for the successful funding of international proposals that the long-term degassing plan is nominated by the Cameroonian government as the number one priority for foreign assistance. Both the short-term and long-term plans also include a substantial component of education and technical training that must be accomplished in order to make the transition from high foreign participation to mainly Cameroonian maintenance of the degassing operation (see Section IV on Education below).

III. SAFETY AND SECURITY

We recommend following the same safety measures that were used during the previous degassing tests at Lakes Nyos and Monoun. At Lake Monoun, the Cameroonian military evacuated people from low-lying areas around the lake during the tests. At Lake Nyos, evacuation to higher ground was accomplished through arrangements made by the security team. During both tests, the Cameroonian military (Marines) supplied compressed air masks (SCUBA) that were available for all participants. Although there will be an automated warning system in case of disruption of flow in the pipes (see Section VIII, Technical Plans), we recommend having at a safe location a permanent, trained observer on site at both lakes to monitor the operation of the degassing equipment and to respond to needed modifications of the operation.

At Lake Nyos, it is worth noting that the areas below the lake are officially off-limits now. A thorough sweep of the area should be made before the degassing operation commences, but once the piping has proceeded for several days, it should be sufficient to spread the word through local chiefs and officials that the area should remain evacuated until the gas content in the lake is greatly lowered. Given the cooperation of local people in our past efforts and the official off-limits territory, there should be no difficulty with this precaution.

At Lake Monoun, the people living near the lake are actually in danger now. At a minimum, they should be warned about the dangers. As discussed below, we will work with the local government and agencies such as the International Red Cross and U.S. Peace Corps to educate those living near the lake. During the degassing process there will be a CO₂ monitoring system that produces a warning signal if the concentrations in the air near the town of Njindoun reach dangerous levels. Before this installation, properly educated people could probably flee to high ground (nearby on two sides of the lake) fast enough to escape death should a release occur before the degassing operation begins. Also, the piping should reduce the hazard at a fairly fast rate, so the local populace will receive a faster benefit from the mitigation. Given our calculations of flow rates in the installed degassing pipes, in a few years there should be no real hazard of gas release at Lake Monoun. The fishermen who work directly on the lake present the biggest concern. While it may be impossible or unfair to keep them from their livelihoods during the entire degassing period, they must be educated to stay away from the pipe area. Our experience is that they will be quite reasonable and supportive of our efforts if they are properly compensated for the disruption of their livelihoods.

Finally, it should be noted and accepted that these lakes are currently very dangerous and that a sudden and catastrophic release of gas could occur at any time. However, in our review we found that all evidence and calculations to date indicate that the proposed hazard mitigation, and the actual process of controlled degassing, will not increase the likelihood of another sudden gas release.

IV. EDUCATION AND TRAINING

Short Term

In the short term there are two priorities. First there must be education of target groups living close to the lakes. This education is necessary to inform local populations about the risks associated with the lakes, about the general methods that will be used to reduce these risks, and about the cooperation that is needed during the degassing such as temporary evacuation and avoidance of pipes and platforms on the lakes. The NMDP Committee recommends that the Cameroonian government produce a small pamphlet, with input from scientists, that can be distributed to the target groups. The distribution of this pamphlet should be coordinated with "town meetings" to answer specific questions about the degassing program. There appears to be both money and personnel available through the International Red Cross and the U.S. Peace Corps to facilitate this program of education in collaboration with the appropriate Cameroonian Ministries. In addition, because concerns about the hazards of these lakes are so widely spread throughout Cameroon, there should be a one page "poster" that is produced that describes the general degassing project. This poster can be distributed and displayed in central, public areas throughout Cameroon.

The second priority is to train technicians for the immediate tasks associated with installation of the pipes this year. This will require Cameroonian government funds to support the current technical force available (that is, the small number of people who have worked with the international community in the past), and to support the initial stages of training more students and technicians who will continue the monitoring and maintenance of the program in the long term.

Long Term

In the long term, all of the tasks associated with the degassing will need to be assumed by Cameroonian scientists and technicians. Thus there must be a program of training and higher education of the next generation of scientists, engineers, and technicians. Overall, this program on the lakes offers a wonderful opportunity for young Cameroonians interested in science. For example, there are many different projects for students such as monitoring the biology, chemistry, and physics of the lakes during and after the transition from high gas to low gas contents. In addition, the international community is able to offer technical expertise and training for students, especially if the Cameroonian government provides support for both short and long-term training in Europe, Japan, or the U.S.

V. USE OF DEGASSED CO₂

There are two potential uses of the degassed CO2 from these lakes. The first is scientific and the second is commercial. The NMDP committee has expertise in the potential scientific uses of CO2, and our discussion here is centered around those uses and issues.

The most exciting possible use for the degassed CO2 is in a CO2-enrichment experiment. Human activities on earth have been increasing greenhouse gases and the CO2 content of the atmosphere, and this increase will continue into the future and will change our climate. Because of this, there has been a tremendous amount of research on how natural ecosystems respond to elevated CO2 concentrations. The current state-of-the-art research projects in this area are called Free Air CO2 Enrichment, or "FACE" experiments. FACE experiments use large volumes of CO2 blown across large plots of vegetation. The range of CO2 required is from ~3,000 to 9,000 metric tons per year, and the U.S. cost is about $60 to $95 USD per ton. The estimated pumping rate of one 13 cm pipe in Lake Nyos is ~30,000 tons per year, which would be sufficient for a FACE experiment. The length of time that this amount of gas is required would be from 8-10 years. Thus a research group interested in conducting a local FACE experiment would have the benefit of using the CO2 from Nyos.

The advantages of using CO2 from these lakes are (1) the CO2 has a distinct ¹⁴C and ¹³C signature, (2) the high purity (ethylene-free) CO2 is readily available, and (3) it is a tropical setting and there is a great need for more information on the response of tropical systems to increased atmospheric CO2. The main drawback for establishing a FACE experiment near Lake Nyos is that these experiments also require a substantial amount of power. The expense of this power is from ~$3,000 to $10,000 USD per year. Thus a small scale experiment seems more readily feasible at Lake Monoun because it is closer to power distribution lines.

The commercial uses of the gas may be varied, and could include technical or industrial applications. The drawback to these commercial uses is the remote location of the lakes, especially Lake Nyos, and the lack of electrical power at the sites. Power would be needed to construct an extraction and bottling plant. The other costs associated with commercial use must include the transportation from the lakes to industrial centers.

At present, it appears that there are no large, immediate financial rewards for the use of the gas contained in these lakes. Although the potential for scientific and commercial use should continue to be explored, we find no indication that the degassing project should be delayed. Neither will the degassing scheme be too much complicated by the eventual use of the discharged gas. Once the main degassing is nearly ended, a small pipe could be maintained in the lakes that reaches a bottom layer of 1-2 meters thick that still contains high pressures of gas (which would power the extraction). This would maintain a smaller source of CO₂ for longer periods of time.

VI. ENVIRONMENTAL ISSUES

The main potential impact on the environment of the lakes will be from the release of anoxic, saline bottom water at the surface. However, the data gathered to date on these lakes indicate that these impacts will be very small. Because the driving force for fluid flow in the pipes is CO2 exsolution, flow rates will be highest during the initial stage of degassing and will decrease with time as the concentration of CO2 in the bottom water decreases. The initial flow rate of water in the pipe from the bottom to the surface of Lake Nyos will be at most 1,700,000 cubic meters per year (1.7 x 10⁶ m³/yr). This water will be somewhat dispersed at the surface of the lake due to the piping design, but more importantly it will be mixed into and diluted by the surrounding surface water. In Lake Nyos the upper 45 m of the water column mixes with the atmosphere each year and contains about 6 x 10⁷ m³ of water. Thus, in the first year the discharge water would be diluted by about 50 times. But in fact the dilution is much greater because of the turnover of water in the surface of the lake due to flushing. Based on rainfall records, drainage basin area, and our stream gauging results, Tuttle et al. (1992) calculated that the freshwater input to the lake surface is about 2.4 x 10⁷ m³/yr, or 14 times the flow rate of bottom water in the pipe. Therefore, the surface water down to 45 m flushes completely out of the lake in a little more than two years, and with this high turnover rate, the dilution factor for degassed water is large enough to prevent serious ecological perturbations or harm.

At Lake Monoun the flow of the Panke river into and out of the lake has not been gauged to our knowledge, but based on rainfall records must be at least as large as the freshwater throughput at Lake Nyos. At the same time, the discharge rate of bottom water through one 13 cm pipe should be about 3/4 of the rate in Nyos, suggesting that the ecological consequences will be smaller than in Lake Nyos.

Many Cameroonian lakes (e.g., Wum, Manengouba, Barombi Mbo) have occasional overturns where anoxic water reaches the surface, and although fish kills have been reported, the fish populations recover. It is unlikely that substantial fish kills could occur as a result of the anoxic water brought to the surface during the degassing. For example, no fish kills were observed during the test degassing at Lake Monoun in 1992, and because water below 5-7 m in the lake is normally anoxic, fish in the lake are accustomed to living with anoxic water in close proximity. The fish in Monoun can survive short periods of exposure to anoxic water, as has been shown for other cichlid fishes. Finally, the fish populations recovered fine after the 1984 gas burst in Lake Monoun, possibly due to the fact that there are three basins in Lake Monoun, only one of which contains high concentrations of gas. The fish in Lake Nyos were recently introduced by a French scientist, and are not used substantially by the local population. The threat of anoxic water causing fish kills in Nyos is less than found in Lake Monoun because of the larger volume of an oxygenated upper mixed layer of water in Nyos.

The actual discharge rate of CO2 (considering CO2 as a greenhouse gas pollutant) from a single pipe at Lake Nyos is no more than the CO2 discharge rate of a 1.2 MWe production by a coal-fired power plant. In addition, because of the isolated nature of this discharge and the rapid mixing of the gas with surrounding air, there should be no problem with local pollution. There are also no other pollutants such as hydrogen sulfide or nitrous oxides that will be released in substantial concentrations from the lake.

The monitoring equipment that has been and will be installed on both lakes will be able to detect small changes in the temperatures and salinity of the water, the gas concentrations in the bottom waters, and the stability of lake stratification. Any changes in these parameters will alert us to the fact that the anoxic water may be moving toward the surface or that the salinity of the surface water may be changing. Periodic measurements of a full suite of chemical and biological parameters will also be used to track any potential changes in the lakes that occur during degassing.

VII. ISSUE OF THE DAM

The natural spillway or dam at Lake Nyos is composed of loosely consolidated volcanic material. The exact composition and age of dam materials is unknown. However, the structure is weak, and when the dam fails it will generate a tremendous flood that could empty the upper 40 m of Lake Nyos and reach into Nigeria. What is currently needed is an expert evaluation of how to address this hazard. There are at least two possibilities; the first is to use "jet-grouting" to stabilize the dam, and the second is to draw down the level of the lake and use horizontal drilling to change the outflow so it is below the weak dam. We recommend that the Cameroonian government facilitate a study on the dam by an NGO as soon as possible (there is one French organization, Hydraulique Sans Fronti�re (HSF), that we are aware of with the appropriate expertise). Regardless of the option of removing the potential flood hazard, it is necessary to first remove the gas from the lake. Once the bulk of the gas has been removed, remediation on the dam could begin. If possible it will be best to keep the level of the lake stable so as not to depressurize any gas contained in pockets or dissolved in groundwater beneath the lake. However, if there is no alternative and the lake level must be lowered, the process must be done slowly and carefully with enough time to let the system come to a new steady state before proceeding.

VIII. TECHNICAL PLANS

The design of the degassing system (pipe, valves, sensors, and actuators) has been decided on. The design will be almost identical to the design used in previous degassing demonstrations, successfully carried out at Monoun (1992) and Nyos (1995). Based on various safety considerations, we have decided on the following:

(1) Pipe material.

The most important potential hazard is the failure of the pipe at some depth during the degassing process. Should this occur, bubbles will escape in the open water and could trigger an uncontrolled gas release. Therefore, the pipes must be made up of a very ductile material (in contrast with brittle ones). The high density polyethylene we have chosen combines several important advantages, including (a) very pliable (lengthening above 200% at break point), (b) neutral buoyancy (density 0.96 g/cm³), and (c) easy to cut and to weld. With the polyethylene pipe this potential hazard of pipe breakage at depth is virtually eliminated.

(2) Automatic reduction or shut-down of the degassing in case of problems.

It may become necessary to reduce the gas flow or to shut-down the gas flow at some time during the degassing. We will use the automatic opening of a lateral valve to accomplish this shut-down. It is not possible to actually close the pipe rapidly (either at the top or bottom), because the trapped gas will generate a buoyancy force (Archimedian, lifting the whole pipe) which will not be counteracted by the ballast attached to the pipe. Because the flowing stream of gas and water creates a steady low pressure inside the pipe, the opening of a lateral valve at a suitable depth will cause the external, gas-poor water to enter the pipe and mix with the gas-rich water. This will result in a decrease of the energy associated with the gas coming out of solution. The water and gas jet will thus be slowed down, and the mechanical stress on the pipe structure will return to a harmless level. The former full strength jet can be reactivated simply by shutting the lateral valve.

(3) Real-time monitoring of the degassing system operation.

The data gathered by the monitoring systems will check the proper functioning of the self-siphon process using various technological sensors:

(a) two to three measurements of flow rate and/or flow velocity in the monophasic liquid part of the upward gas jet;

(b) static pressure (depth) at the bottom of the pipe.

          If at least two of these control parameters show a significant change, the rate of degassing will be automatically and instantaneously slowed down by opening the lateral valve. At this point there is a need to evaluate the cause of the shift in the measurements, including on-site inspection. This process leads to the decision to either restart or shut down the degassing system.

In addition to these main safety concerns listed above, the thermal (temperature) and chemical (conductivity and CO2 concentration) profiles of the water column, and their changes with time, will be monitored continuously during degassing. Temperature profile measurement will be carried out as close as possible to the pipe and will be concentrated on depths near the thermocline and at the lower pycnocline (density boundaries). These measurements will evaluate the impact of the ongoing degassing on the stratification and stability of the water column. Water electrical conductivity (salinity) sensors will be attached to the bottom of the pipe in order to monitor the water inflow gas content; this technique uses a relationship between the gas content and the salinity of the water. We will also continuously determine the CO2 concentration of the water taken in at the bottom of the pipe by measuring the volume of CO2 degassed at the surface per volume of water.

The data generated during the monitoring of the degassing will be transmitted by satellite for real-time monitoring of the degassing progress. This transmission system will have bi-directional capability, so that the valves may be operated remotely.

Finally, the NMDP Committee determined that certain studies not currently being made by project personnel would be very helpful in the technical understanding and mitigation of these natural hazards. These studies include (a) measurements of radon concentrations in the lakes to serve as a tracer of gas inputs and gas cycling, and (b) in-situ density measurements of the lake water.

IX. DATA DISSEMINATION AND MEDIA ISSUES

The project will generate a large amount of information and data, and there are both internal and external considerations of the proper use of these project data:

(a) Internal. At least 3 computer sites (Cameroon, France, U.S.) will contain all the data generated in the experiment, and all project personnel can freely access all data. Potential projects associated with the degassing to be done by students should be presented first to the advisory group to make sure that they are compatible with the program. All student data will be available to project personnel for use in maintenance of the degassing system. Students will have primary responsibility for their data in terms of publication in external, peer-reviewed journals.

(b) External. All reports of primary data to the media (or postings on a Web site) must be cleared by the advisory group. General information such as the relative rate of degassing, the number of pipes in operation, and so forth can be given to the media at any time. Project data to be presented in a published scientific record (such as a note to Science or Nature) or in a peer-reviewed article in a scientific journal must be cleared by the advisory group.

There are also various issues with the media (reporters, film crews) that are a concern in this operation, and we advise that two recommendations are followed:

(1) There is open access for all media members from both Cameroonian and international agencies; no person or group should receive "exclusivity rights" that would prohibit open access to filming or interviews with project personnel. Widespread Press coverage will be beneficial for the program. Interested media should contact the Inter-Ministerial Committee to communicate their desire to report on the degassing and to receive a permit.

(2) Media personnel or groups with permits should be offered transportation to the lakes separately from the scientific equipment. Once on site, there should be a "media tent" or area where the media personnel can be located. A schedule should be made that allows the media access to project scientists and technicians during specific, set times during the day. A balance must be found between access and interference.

This report is provided by the NMDP Advisory Committee, and may be viewed at the Web site http://www.umich.edu/~gwk/research/nyos.htm. This web site will also be linked in the future to the web site of MINREST in Cameroon.

NMDP Advisory Committee:

Alain Bernard, Belgium. [email protected]

William Evans, United States. [email protected]

Michel Halbwachs, France. [email protected]

George Kling, (Chair), United States. [email protected]

Minoru Kusakabe, Japan. [email protected]

Jean-Christophe Sabroux, France. [email protected]

Gregory Tanyileke, Cameroon. [email protected]

Klaus Tietze, Germany. [email protected]