Hydrogeochemical and anthropogenic influence on the quality of water sources in the Rio del Rey Basin, South Western, Cameroon, Gulf of Guinea

This study which focuses on the hydrogeochemical and anthropogenic influence on water sources in the Rio del Rey Basin has provided an insight into the sources of major ions, water mineralisation processes, and the suitability of the water sources for drinking and agricultural purposes. Fifty-one (51) samples (38 groundwater, 9 surface water, 1 tap, 1 reservoir and 2 rainfall events) were analysed for physico-chemical and microbial quality. The pH of groundwater samples ranged from 5.5 to 8. Sixty percent (60%) of the groundwater samples were slightly acidic (5.5-6.4) and were different from the WHO (2004) standard for drinking water. Electrical conductivity values (3-274 μS/cm) and total dissolved solids (7.66 to 248.30 mg/l) for groundwater sources were low and signified low mineralisation and freshwater conditions. The relative abundance of major ions (meq/l) was Na+>K+>Mg2+>Ca2+ for cations and HCO3->NO3->SO42->Cl- for anions. The main water types were: Na-HCO3 (45%), Ca-HCO3 (35%), Na- Ca-HCO3 (15%), Ca-Mg-Cl (2%) and NaCl (2%). The processes that influenced the water chemistry were incongruent silicate dissolution and cation exchange. The chemical constituents were low and within the WHO (2004) guidelines for drinking water except for high concentrations of NO3- (77.28 mg/l) and Br- (0.08 mg/l) in one open well. Water quality index calculated using the adjusted form of CCME (2001) based on the major and chemical parameters (TDS, pH, F- and Br-) for groundwater and surface water data indicated that 90, 6, 2 and 2% provided excellent, good, marginal and poor water quality, respectively for drinking purposes. The evaluation of results showed that 90% of groundwater sources were suitable for agricultural purposes. Total coliform counts indicated that 97% of the groundwater sources were polluted.Key words: Groundwater chemistry, microbial quality, anthropogenic influence, Rio del Rey Basin

Hydrochemistry of shallow groundwater and surface water in the Ndop plain, North West Cameroon

This study was conducted on the hydrochemistry of shallow groundwater and surface water in the Ndop plain, North West Cameroon. The objectives were to determine the physico-chemical characteristics of water, controls on water chemistry and suitability for drinking and irrigation. Forty-six shallow groundwater and 26 surface water samples were investigated. Field measurements of physical parameters were preceded by chemical analyses of the samples for major ions and F-. About 69% of the water sources had pH values below 6.5, classifying the water as barely acidic. Electrical conductivity (<282 μS/cm) and total dissolved solids (<183 mg/l) were low suggesting low-mineralised and freshwater. The relative abundance of major ions (meq/l) was Na2+>Ca2+>Mg2+>K+ for cations and HCO3->>NO3 -≥ Cl->SO42- for anions. Major ion concentrations were low, and within the WHO guidelines for drinking water, but F- concentrations were much lower (<0.39 mg/l) and below guideline value. Main water types and proportions were Na-HCO3 (53 %), Ca-HCO3 (35 %) and a mixed Na-Ca-HCO3 (11%). Predominant processes influencing water chemistry were incongruent dissolution of silicate minerals and cation-exchange of Na+ in rocks for Ca2+ in water. The low major ion concentrations indicated low water-rock interactions and short residence time. The analysed water was suitable for irrigation.Key words: Water chemistry, hydrochemical controls, drinking-irrigation quality, Ndop plain, Cameroon

CONFCAYS 2019 & Sub Regional Training Workshop on Science AdviceScience Advice in Africa: Opportunity or illusion: Young Scientists: Mainspring of innovation and development in Africa

International audienceThe Cameroon Academy of Young Scientists (CAYS) is a branch of the Cameroon Academy of Science (CAS) aimed at promoting research, paving the way for young scientists, encouraging the development of innovative approaches to national and international challenges. CAYS is a forum for building scientific capacities and the applicability of science to solve problems and provide decision makers and the public with advice based on the most up-to-date scientific knowledge. With support from MINRESI, MINTOUR, MINESUP, CAS, AUF and other partners, CAYS is organizing it first biennial international conference under the theme «Young Scientists: Mainspring of innovation and development in Africa » where scientists have opportunities to present their research results on diverse topics. More and more, scientific advice is spreading the world over to assist policy makers and politicians to make decisions that are informed by evidence-based data and scientific knowledge. It is an opportunity for dialogue that breaks or limits the gaps between researchers in different fields. In Africa and particularly in the Central African Sub-region, the progress of this concept is still lagging behind. Taking cognizance of this, CAYS offers an opportunity, during this conference, of a training workshop on the science advice in collaboration with The Quebec Research Funds (FRQ) and the International Network for Government Science Advice (INGSA). For the workshop, 65 participants were selected from government institutions and civil society organizations in the Central African Region. A total of 153 abstracts (55 oral and 98 poster presentations) were selected from national and international participants. The said abstracts will be presented in 4 sessions under 3 major themes including 1) Nutrition, Health and Environment; 2) Material Science, ITC and Renewable Energy; and 3) Digital Economy, Peace and Development. These abstracts have been compiled in this abstracts volume

Major ions, δ18O, δ13C and 87Sr/86Sr compositions of water and precipitates from springs along the Cameroon Volcanic Line (Cameroon, West Africa): Implications for provenance and volcanic hazards

A combined study of major ions, δ18O, δD, 13C, 87Sr/86Sr isotopes, X-ray diffraction, scanning electron microscopy, and electron probe microanalyses on springs and spring mineral precipitates along the Cameroon Volcanic Line (CVL) was undertaken to understand water chemistry, and infer the type and origin of the precipitates. The waters are of evaporated Na + KCl and non-evaporated Ca + MgHCO3 types, with the more mineralized (electrical conductivity-EC of 13130 μS/cm) Lobe spring inferred to result from interaction of circulating 49 °C waters with magmatic volatiles of the active Mt. Cameroon. Water mineralization in the other springs follows the order: Sabga A > Sabga B > Bambui B > Bambui A > Nyos Cave. But for the Nyos Cave spring, all other springs contain fluoride (up to 0.5–35.6 mg/l above WHO potable water upper limit). The Sabga spring contains arsenic (up to 1.3 mg/l above the WHO limits). The springs show low fractionation temperatures in the range of 19–43 ᵒC. The Lobe and Sabga A springs are precipitating dolomite (CaMg(CO3)2), while the Nyos Cave, Bambui A, Bambui B and Sabga B springs precipitate trona ((Na3H(CO3)2.H2O). Our data suggest a marine provenance for the carbonates, and point to a volcanic input for the Lobe, Nyos, Sabga A, and Bambui A springs. The latter springs are therefore proposed as proxies for monitoring volcanic activity for hazard mitigation along the CVL

Hydrochemical characteristics of groundwater in sedimentary, metamorphic and volcanic aquifers in Ndian Division, South West Region, Cameroon.

Wells and springs are the dominant potable water sources in the area of study used by the population. Studies of the characteristics of aquifer types and the hydrochemistry of groundwater in sedimentary, metamorphic, and volcanic aquifers in the southern part of Ndian Division indicated the presence of the following three types of aquifers-sedimentary (alluvial), metamorphic (weathered/fractured gneisses) and volcanic (jointed basalts and pyroclastic materials). Fieldwork involved collecting details on rock characteristics such as the mineralogy, grain-size and texture. Physical parameters (pH, EC and temperature) were measured in-situ. Cations were determined by AAS and anions by ion chromatography. The pH values for sedimentary aquifers (5.50-8.00), metamorphic (6.10-7.40) and volcanic (5.80-7.60), reflected slightly acidic, neutral and basic water sources. The mean concentration of total dissolved solids (TDS) in the groundwater increased from metamorphic (8.84 mg/l), to volcanic (17.08 mg/l), and to sedimentary (40.48 mg/l) aquifers, representing the degree of mineralisation in these rock types. Alkalinity increased from metamorphic (14.53 mg/l), volcanic (19.18 mg/l), to sedimentary (57.64 mg/l). Based on the electrical conductivity, all the water sources were suitable  for drinking and for irrigation. Relating the major groundwater chemical facies to their geologic occurrence showed that the water in sedimentary rocks was characterised by Na-HCO3 (90%) and Ca-(HCO3)2 (10%), in the metamorphics by Na-HCO3 (100%) and in the volcanic aquifers by Ca/Mg-(HCO3)2 (70%) and Na-HCO3 (30%) water types. Based on WHO (2004) norms for potable water, 37 water sources were suitable for drinking and one water source (open well at Bekora) unsuitable due to excess nitrate and bromide concentrations of 77.28 mg/l and 0.08 mg/l respectively. Relatively based on EC and TDS, the most mineralised water was found in the sediments, the volcanics intermediate and the least mineralised water was in the metamorphic formations. The results constitute useful baseline information for future provision and management plans of water resources in the area.Keywords: Ndian Division, rock types, hydrochemistry, physical properties, groundwater, unconfinedaquifers

Heavy Metal Contamination and Ecological Risk Assessment in Soils of the Pawara Gold Mining Area, Eastern Cameroon

Pawara area is a mining district in the eastern region of Cameroon. Mining in the area is generally artisanal and semi-mechanized, practiced by the local miners and immigrants from neighboring African countries and China. The lack of strict regulations and control of mining activities permits the miners to use illegal substances, especially Hg in gold separation. These expose the area to toxic and heavy metals pollution. This study highlights the source of heavy metals concentration in the Pawara soils and the potential adverse effects of Hg on gold separation to the environment and health. Three mining sites and one control site were investigated, namely Site A, Site B and Site C. The control Site 0 (background) is an area where no mining and agricultural activities have taken place. Soil samples were collected at depth of 20 cm, with six from each site (24 samples). Samples were analyzed for Al, Cd, Cr, Cu, Fe, Hg, Pb, Cd and Zn content using atomic absorption spectrophotometry in a graphite furnace. The metals, except for Fe, show high values for all three sites exceeding the background levels in the soils. Hg shows the highest concentration on Site A with a value of 1590 mg kg−1. Pb is highest on Site B with a concentration of 12,274 mg kg−1. The contamination degree was assessed with the help of contamination indices (Igeo—index of geo-accumulation; PLI—pollution load index; RI—potential ecological risk; Eri—ecological risk; Pi—single pollution index; CF—contamination factor) and all parameters show a high degree of contamination on all three sites compared to the control site. Hg, Pb, Cd, Cr and Cu as single pollutants show the highest ecological risk on Site A and Site B where intense mining is taking place. The absence of industrial and large-scale agricultural activities in the Pawara area, the nonexistence of contaminants on the control site and the presence of contaminants on Site C where farming is high and mining is low jointly show that the discharge of mine wastes onto the soils and stream channels are the main source of contaminants and potential pollutants of the Pawara ecological environment

Heavy Metal Contamination and Ecological Risk Assessment in Soils of the Pawara Gold Mining Area, Eastern Cameroon

Pawara area is a mining district in the eastern region of Cameroon. Mining in the area is generally artisanal and semi-mechanized, practiced by the local miners and immigrants from neighboring African countries and China. The lack of strict regulations and control of mining activities permits the miners to use illegal substances, especially Hg in gold separation. These expose the area to toxic and heavy metals pollution. This study highlights the source of heavy metals concentration in the Pawara soils and the potential adverse effects of Hg on gold separation to the environment and health. Three mining sites and one control site were investigated, namely Site A, Site B and Site C. The control Site 0 (background) is an area where no mining and agricultural activities have taken place. Soil samples were collected at depth of 20 cm, with six from each site (24 samples). Samples were analyzed for Al, Cd, Cr, Cu, Fe, Hg, Pb, Cd and Zn content using atomic absorption spectrophotometry in a graphite furnace. The metals, except for Fe, show high values for all three sites exceeding the background levels in the soils. Hg shows the highest concentration on Site A with a value of 1590 mg kg−1. Pb is highest on Site B with a concentration of 12,274 mg kg−1. The contamination degree was assessed with the help of contamination indices (Igeo—index of geo-accumulation; PLI—pollution load index; RI—potential ecological risk; Eri—ecological risk; Pi—single pollution index; CF—contamination factor) and all parameters show a high degree of contamination on all three sites compared to the control site. Hg, Pb, Cd, Cr and Cu as single pollutants show the highest ecological risk on Site A and Site B where intense mining is taking place. The absence of industrial and large-scale agricultural activities in the Pawara area, the nonexistence of contaminants on the control site and the presence of contaminants on Site C where farming is high and mining is low jointly show that the discharge of mine wastes onto the soils and stream channels are the main source of contaminants and potential pollutants of the Pawara ecological environment

A comparative review of petrogenetic processes beneath the Cameroon Volcanic Line: Geochemical constraints

The origin and petrogenesis of the Cameroon Volcanic Line (CVL), composed of volcanoes that form on both the ocean floor and the continental crust, are difficult to understand because of the diversity, heterogeneity, and nature of available data. Major and trace elements, and Sr-Nd-Pb isotope data of volcanic rocks of the CVL spanning four decades have been compiled to reinterpret their origin and petrogenesis. Volcanic rocks range from nephelinite, basanite and alkali basalts to phonolite, trachyte and rhyolite with the presence of a compositional gap between SiO2 58–64 wt.%. Similarities in geochemical characteristics, modeled results for two component mixing, and the existence of mantle xenoliths in most mafic rocks argue against significant crustal contamination. Major and trace element evidences indicate that the melting of mantle rocks to generate the CVL magma occurred dominantly in the garnet lherzolite stability field. Melting models suggest small degree (<3%) partial melting of mantle bearing (6–10%) garnet for Mt. Etinde, the Ngaoundere Plateau and the Biu Plateau, and <5% of garnet for the oceanic sector of the CVL, Mt. Cameroon, Mt. Bambouto, Mt. Manengouba and the Oku Volcanic Group. The Sr-Nd-Pb isotope systematics suggest that mixing in various proportions of Depleted MORB Mantle (DMM) with enriched mantle 1 and 2 (EM1 and EM2) could account for the complex isotopic characteristics of the CVL lavas. Low Mg number (Mg# = 100 × MgO/(MgO + FeO)) and Ni, Cr and Co contents of the CVL mafic lavas reveal their crystallization from fractionated melts. The absence of systematic variation in Nb/Ta and Zr/Hf ratios, and Sr-Nd isotope compositions between the mafic and felsic lavas indicates progressive evolution of magmas by fractional crystallization. Trace element ratios and their plots corroborate mantle heterogeneity and reveal distinct geochemical signatures for individual the CVL volcanoes