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Background: Treatment and wastewater disposal lack in Abidjan leads to wastewater discharge in the natural environment without treatment. These waters were loaded with pathogenic microorganisms that are the causes of many diseases. Objectives: This study aims to assess the parasitological quality of water from pipes of Abididjan City, studying protozoa and helminths. Methodology: 400 samples were collected in three municipalities and 19 sites. Parasites were identified using sedimentation. Biological analyzes revealed 269 (67.2%) positive samples, with the presence of 19 taxa belonging to helminths (nematodes, cestodes) and protozoa group (amoeba, ciliates, flagellates). Protozoa are most common with a clear dominance of amoebas class followed by ciliates and flagellates. In 269 positives samples, Entamoeba coli (160 (59.48%)), Endolimax nana (112 (41.64%)), Giardia spp (71 (26.4%)), and Paramecium caudatum (66 (24.54%)) are the most common species. The spatial distribution showed that Yopougon commune was the most parasitized, followed by Abobo-Adjame. Results: The most parasitized sites were CHU, SEL, and AG. At the seasonal level, the dry season was where the parasite load was highest regardless of municipality and sites. Conclusion: The presence of these parasite groups and the diversity of parasitic taxonomic indicates faecal contamination of piped water in Abidjan city. These parasites present a potential danger for these piped waters' direct and indirect uses. Therefore, it is necessary to treat this water before any use and before it flows into surface water to avoid these parasites.

For many purposes of hydropower production, many reservoirs are built throughout the planet. Because of the processes of erosion and sedimentation, these infrastructures are facing a big problem of progressive reduction of their storage capacity. Consequently, a good knowledge of the change of storage for proper planning and management is very important. The Universal Soil Loss Equation (USLE) was used to evaluate the gross erosion in the Lom Pangar catchment and the quantity of sediment that effectively reach the outlet of the catchment. The gross erosion was evaluated to be 47.2 million tons of soil per year with an average of 6.61 million tons per year that effectively reach the outlet. On the quantity that reaches the outlet, the Brune’s sediment trap efficiency was applied and 0.1% of Lom Pangar reservoir decreases per year, an amount smaller than the 1% of annual worldwide reduction of water reservoirs. Keywords: Erosion, storage volume, reservoir, Lom Pangar Dam, Cameroon © International Journal of Ground Sediment & Water, ©Sun Jichao. The website is http://ijgsw.comze.com/

In this study, the characteristics of δ2H and δ18O in rainwater, groundwater and spring water have been used to understand the groundwater recharge dynamics in the Amedzofe area (one of the highest human habitation in Ghana). The local Meteoric Water Line (LMWL) using all the rainfall events gave an equation with the best fit line of δ2H = 7.32 δ18O + 8.20 (n = 113; r 2 = 0.94). Heavier rainfall events greater than 10, 20 and 30 mm further orient the slope closer to the Global Meteoric Water Line (GMWL). The data showed that the isotopic compositions of the rainwater in the area are mainly influenced by the rainfall amount with temperature having minimal effect. All the spring water and most of the groundwater plot around the GMWL, implying they are of meteoric origin. The Chloride Mass Balance (CMB) and δ18O shift methods suggest annual mean recharge rate of 160.43 and 125.79 mm/year representing 10.70 and 8.39% of annual rainfall, respectively. The estimated mean recharge rate for the spring was 317.51 mm/year and 300.68 mm/year representing 26.46 and 25.06% of annual rainfall for CMB and δ18O shift methods, respectively. Rainfall stable isotopes from Kpando and Amedzofe gave an altitude effect of 0.17/100 m and altitude of recharge of the springs from +724.00 to +788.61 m amsl. The stable isotopes data identified two distinct moisture sources, isotopically enriched local moisture (evaporated surface water bodies and evapo-transpiration water vapour flux from vegetation) and isotopically depleted moisture source from the Atlantic Ocean. The results further showed that significant groundwater recharge in the study area takes place in the months of March, June and August.

To assess the water quality in the locality of Betare-Oya affected by an intensive artisanal and semi mechanized mining activities, 71 samples were collected from sixteen points during the 2015-2016 hydrological year. These points include: three in Lom river which is the main stream of the study area, five in Mari river which is one of the left bank tributaries of the Lom, in Betare-Oya and eight in the left and the right bank of Mari. Different physicochemical parameters such as pH, electrical conductivity (EC), alkalinity, turbidity, total suspended solids (TSS), cyanide (CN-), major elements and heavy metals (Pb, Zn, Cd, Fe, Cu, As, Mn and Cr) were analyzed. Water Quality Indices (WQI), Heavy metal Pollution Index (HPI), sodium adsorption ratio (SAR) and percent sodium (Na%) were also computed to evaluate the suitability of water for drinking and irrigation. The results showed that the surface water from Betare-Oya was acidic to basic (5.40

The deterioration of water quality in lakes constitutes an environmental problem faced by humanity. The Nkolbisson artificial lake which is located downstream of the Abiergue and Mintotomo streams in Yaounde is under the influence of various forms of pollution, mostly resulting from human activities. There is proliferation of algae on the lake surface that consumes the available oxygen in the lake. The main objective of the current study is to evaluate the different forms of pollutants in the lake, in order to propose efficient solutions for a suitable management strategy, basing on the physico-chemical and biological analysis. The lake retains an average of 2535.49 tons/year of suspended solids in the rainy season and 1438.05 tons/year in the dry season. The range of dissolved oxygen (5.2 - 3.8 mg/l); pH (7.8 - 6.8); temperature (23.9°C - 23.1°C); electrical conductivity (266.1 - 87.3 μS/cm); turbidity (22.3 - 10 UNT); suspended solid (240 - 40 mg/l); BOD (55 - 8 mg/l); COD (76 - 87.3 mg/l). Biologically, faecal coliforms fluctuates between (42 × 102 - 425 × 103 FCU/100 ml), faecal streptococci (8 × 103 - 158 × 103 FCU/100 ml) and total Coliform (15 × 103 - 78 × 106 FCU/100 ml) evidence that, the studied lake is highly polluted. Consequently the lake retains an average of 2888.7 tons/year of suspended matter.

An automatic observation buoy (AOB) was installed at Lake Nyos in March 2014. The temperature and electrical conductivity (EC) of lake water were continuously observed from March 10, 2014 to April 15, 2016. The thermocline and chemocline located deeper than −90 m subsided 15 m in the observation period due to the bottom water removal by the CO2 degassing pipes. The velocity of subsidence was estimated quantitatively by correlating the time variation of EC obtained by AOB and the depth profile of EC. The velocity of subsidence was not constant, namely, it was fast in dry season and slow in rainy season. The time variation in the velocity of subsidence can be attributed to the seasonal variation of water flux in the degassing pipes. Considering the water balance in the deep part of lake, the flux of ground water supplied to lake was estimated to be 6.5*106 (m3/year), which is comparable to the recharge rate of ground water within the catchment area surrounding Lake Nyos. Abrupt drops in temperature and conductivity were observed at −120 m in January 2016, when the temperature at -4 m reached 21.8 °C as the lowest value. The abrupt drops are due to the sinking of surface cold water.

Objectives Sickle cell anemia is due to a mutations on the betaglobin gene, inducing abnormal hemoglobin. In West Africa the main mutations lead to S or C types of hemoglobin. Patients with homozygote mutations seem protected against severe malaria, but not against mild disease. The prevalence of abnormal hemoglobin among patients attending dispensaries for mild malaria is thus unknown. A retrospective study was conducted to update data on the prevalence of S and C hemoglobin among patients attending dispensaries with mild malaria. Enrolment of patients was conducted during in vivo malaria treatment efficacy survey following the 42 days WHO protocol. A group of non-infected pregnant women and a group of patients with fever different from malaria, were also recruited in the same dispensaries. Results 794 blood samples were included. S and C genotypes were found in all the regions of Ivory Coast with the highest prevalence in the Northern region (S and C genotypes, 27%). In non-infected patients, prevalence of mutations was higher than in malaria patients. Conclusion A high proportion of patients with mild malaria carried genetic hemoglobin disorder. This population of high risk must be better investigated to control treatment efficacy and to manage complications. Electronic supplementary material The online version of this article (10.1186/s13104-018-3296-7) contains supplementary material, which is available to authorized users.

The alluvial aquifer underlying the city of Douala comprises shallow Quaternary deposits where groundwater is the main source for domestic and drinking purposes. Shallow groundwater in the area show signs of acidification with average pH range of 3.8-6.8. Long-term groundwater chemistry data (1998-2013), hydrogeochemical and R mode factor analysis were used to establish the acidification process of shallow groundwater and also determine possible origin and implications for water quality and use in the area. Twenty-six groundwater sample points, three streams and three rain sample points were studied seasonally in the 2006-2008 and the 2010-2013 study periods. The data were compared with result of a study, 7 years earlier (1998-1999). The results show evidence of acidification manifested by depletion of HCO3, a decrease in the pH and increase in SO4 and NO3 concentrations of shallow groundwater. Average groundwater pH range is 3.94-7.70 (1998-1999), 3.8-6.91 (2006-2008), and 3.7-6.8 (2010-2013). Only approximately 16 % (1998-1999), 14 % (2006-2008) and 11.11 % (2010-2013) of water samples fall within the range of pH (6.5-8.5) for potable water according to WHO (1993). The alkalinity/acid neutralizing capacity of the shallow groundwater has decreased significantly coupled with increase in the number of zero alkalinities recorded in the 2010-2013. The shallow groundwater is generally undersaturated with common carbonate minerals (calcite, dolomite), therefore providing insufficient acid buffer. Principal component analysis in combination with hydrogeochemical studies revealed that four main factors are responsible for the groundwater chemistry and acidity: (1) acid atmospheric deposition, (2) anthropogenic activities (industrial effluent discharges and acid spill, (3) chemical weathering, and (4) coastal atmospheric deposition/cation exchange. In general, the shallow groundwater is not suitable for drinking and domestic purposes with respect to the low pH and elevated nitrate concentration. In view of the implications such as increase in corrosion and increased mobilization of toxic elements (e.g. Al, Pb, Cu, Zn, Mn) as well as their possible harmful effect on health, it is recommended that the causes, rate of acidification and the mobility of trace elements be investigated with more details.

Water containing high concentrations of nitrate is unfit for human consumption and, if discharging to freshwater or marine habitats, can contribute to algal blooms and eutrophication. The level of nitrate contami- nation in groundwater of two densely populated, agro- industrial areas of the Cameroon Volcanic Line (CVL) (Banana Plain and Mount Cameroon area) was evaluated. A total of 100 samples from boreholes, open wells and springs (67 from the Banana Plain; 33 from springs only, in the Mount Cameroon area) were collected in April 2009 and January 2010 and analyzed for chemical constituents, including nitrates. The average groundwater nitrate con- centrations for the studied areas are: 17.28 mg/l for the Banana Plain and 2.90 mg/l for the Mount Cameroon area. Overall, groundwaters are relatively free from excessive nitrate contamination, with nitrate concentrations in only 6 % of groundwater resources in the Banana Plain exceeding the maximum admissible concentration for drinking water (50 mg/l). Sources of NO3 - in groundwater of this region may be mainly anthropogenic (N-fertilizers, sewerage, animal waste, organic manure, pit latrines, etc.). Multivariate statistical analyses of the hydrochemical data revealed that three factors were responsible for the groundwater chemistry (especially, degree of nitrate con- tamination): (1) a geogenic factor; (2) nitrate contamina- tion factor; (3) ionic enrichment factor. The impact of anthropogenic activities, especially groundwater nitrate contamination, is more accentuated in the Banana Plain than in the Mount Cameroon area. This study also dem- onstrates the usefulness of multivariate statistical analysis in groundwater study as a supplementary tool for inter- pretation of complex hydrochemical data sets.

Summary We used environmental tracers (δD, δ 18 O, 3 H and chlorofluorocarbons (CFCs)) to establish the groundwater flow system within the Mount Cameroon area: a 4090 m high active entirely alkaline volcano located within a humid equatorial region. Seventy-five ground and surface water samples (68 spring samples, 6 borehole samples and 1 stream sample) were collected around the volcano during the wet (October–November 2010) and dry seasons (January–February 2010) as well as 10 rain samples in June–September 2010 in order to establish recharge elevations, apparent ages (residence times) and groundwater flow system in the fractured volcanic (basaltic) aquifers. The δ 18 O and δD composition of rainwater and groundwater in the Mount Cameroon area fit the Douala Local Meteoric Water Line (DLMWL). The recharge elevations of the individual springs were calculated from their δ 18 O-values and the equation of the altitude gradient (−0.16‰ δ 18 O/100 m) of precipitation on the mountain. For springs sampled during the two seasons, dry season samples have higher recharge elevations than rainy season samples. Seasonal variation exists in the tritium values as rainy season samples systemically are higher than those of the dry season samples . This implies the input of new water from the rain causing the groundwater system to rejuvenate. Apparent ages for the Mount Cameroon springs calculated from CFCs based on the Piston Flow model range from 10 to approximately 57 years. CFC apparent ages for rainy season samples are systemically younger than those of dry season samples. There is seasonal variation in groundwater flow system in the Mount Cameroon area and also along the different flanks of the volcano. The groundwater flow system is conceptualized by 2 models; a Bypass/piston flow model for the flow system during the rainy season and a binary mixing/piston flow model characterizes the flow system during the dry season.

Hydrochemical and environmental isotopic ( 2 H, 18 O and 3 H) data were used to investigate the hydrogeochemical and isotopic characteristics of groundwater within Mbanga, Njombe and Penja (Banana Plain). Hydrogeochemically, the groundwaters are mainly Ca–HCO 3 , Ca–Mg–HCO 3 , Ca–Na–HCO 3 , and Ca–Na–NO 3 –Cl–HCO 3 water types. The groundwater chemistry may be adequately explained by the incongruent dissolution of silicate and alumino-silicate minerals, impact of anthropogenic activities and cation exchange between the groundwaters and clay minerals. The isotopic contents of groundwaters ranged from −4.2‰ to −2.1‰ for δ 18 O, from −23.4‰ to −10.6‰ for δD and from 0.6 to 1.4 TU for tritium. In the conventional δD–δ 18 O diagram, the distribution of data points indicates that the groundwaters are of meteoric origin and have not been affected by evaporation. Environmental isotopes ( 18 O, 2 H and 3 H) indicate mixing between recent and old groundwaters; the latter were recharged under more humid climatic conditions than that at present or from higher elevations. Groundwater in Mbanga, Njombe and Penja are of meteoric origin, young and are still in the early stage of geochemical evolution.

In this study, 8 bottled water brands sold in Cameroon were analyzed for 76 elements/parameters by ICP-MS, IC, titration and mass spectrometric methods. This was to investigate the geochemical characteristics of the bottled waters in order to identify the main hydro geochemical processes controlling their chemical content. A comparison of the element concentrations and the legal limits for both bottled and tap water (Cameroon, EU, US EPA, WHO) shows that Aluminium concentration in three brands is above the lower guideline value set by EPA with very high lead concentration (6.4 μg/l) in one brand. Various water quality classification systems were used in to characterize the different bottled water types. Piper diagram was used to establish that dominant chemical types of the bottled water brands are Ca–HCO3, Ca–Mg–HCO3, Ca–Na–Mg–HCO3, Na–HCO3 and Na–Mg–HCO3. Application of R-Mode factor analysis to the data set allowed the determination of the possible relationship between the distribution of individual elements and lithology or other surface enrichment phenomena. In particular waters draining through volcanic rocks are enriched in elements such as As, B, Br−, Cl−, Cs, F, K, Li, Na, NO3−, PO43−, Rb, Sc, SiO2, Sr, Te, Ti, and V. One of the three R-Mode factor analysis associations, recognized as being representative of elements analyzed shows high nitrate and Pb loadings along with As, PO43− and Zn. The latter association probably reflects a sign of anthropogenic contribution in the volcano-sedimentary aquifers of the study area. Q-Mode hierarchical cluster analysis established four major groups amongst the bottled water brands. Stable water isotopes (δD and δO18) established that the recharge origin of the bottled waters and other groundwaters of the study area is meteoric.