Isotope Tracking of Surface Water Groundwater Interaction in the Beninese Part of the Iullemeden Aquifer System

The Kandi basin is located in northeast Benin (West Africa). This study is focused on the estimation of water fluxes exchanged between the river Niger (and its tributaries) and the transboundary Iullemeden Aquifer System. In that framework, an innovative approach based on the application of the Bayesian Mixing Model (MixSIAR) analysis on water isotopes (oxygen-18, deuterium and tritium) was performed. Moreover, to assess the relevance of the model outputs, Pearson’s correlation and Principal Component Analysis (PCA) have been done. A complex relationship between surface water and groundwater has been found. Sixty percent (60%) of groundwater samples are made of more than 70% river water and rainwater;while 31.25% of surface water samples are made of about 84% groundwater. To safeguard sustainable water resources for the well-being of the local communities, surface water and groundwater must be managed as a unique component in the Kandi basin.

Assessment of Groundwater Physico-Chemical Quality in the Ouémé Delta (Southern-Benin)

Groundwater resources are the main sources of water used to supply drinking water to the population of the Ouémé Delta via the Continental Terminal aquifer. Urbanization, population growth, and agricultural and industrial activities have resulted in a deterioration in the quality of these resources. To assess the quality of the delta’s groundwater and its suitability for human consumption and irrigation, a total of fourteen (14) physico-chemical parameters were analyzed in some forty existing water points between September 2020 and March 2021, using standard water analysis techniques. The values obtained were compared with the potability standards recommended by the World Health Organization (WHO) and the Republic of Benin and were subjected to statistical analysis (principal component analysis (PCA)). In addition, methods for determining the suitability of water for irrigation were used. The results showed that the waters are acidic to slightly neutral and influenced by ambient temperature. In addition, the waters are moderately mineralized, with conductivities (24 - 1205 μS/cm) in line with WHO standards. A comparison of the analytical results of the WHO (2017) and Benin (2001) standards indicates that the majority of the waters studied are of good quality for all the chemical parameters considered. Nevertheless, some samples show levels of nitrates (21%), potassium (14% to 16%), calcium (13%), ammonium (12%), nitrites (8%) and bicarbonates (10%) over their respective standards. The Wilcox and Riverside diagrams indicate that the majority of waters (90%) have excellent suitability for irrigation and no negative effect on soil fertilization.

Structural and Mineralogical Characterization of the Clayey Deposits of Gbédji-Kotovi in Lama Depression, Bénin

The objective of the study was to characterize the clays of the Lama depression in Benin. Macroscopic examination of hand soundings, dynamic penetration test and stratigraphic correlation of water borehole logs, as well as scanning electron microscopy (SEM) combined with energy-dispersive X-ray microanalysis (EDX) method were made on compact or stratified clays. The large grains are embedded in a sintered matrix. The texture is heterogeneous and open, including quartz, carbonates and organic matter. The fine fraction is dominated by mineral paragenesis characterizing Kaolinite-Quartz-Calcite-Gypsum dioctahedral smectites composed of: Oxygen, Silica, Carbon, Aluminum, Iron, Zinc, Titanium and Magnesium. This smectic and regular structure includes coarse grains of the order of 800 μm. The pore diameters vary from 130 μm to 1.14 μm. The inter-particle porosity is poorly developed unlike the inter-aggregate pores larger than 0.05 μm. The texture is laminar and shows elongated turbo static particles with more or less rounded edges and honeycomb particles. Quartz and carbonates induce an increase in heterogeneities which develop mechanical sensitivity and hydraulic conductivity. High contents of silica, iron or aluminum and low contents of calcium and magnesium, as well as the presence of other trace elements suggest an alumino-ferriferous clay resulting from the hydrothermal alteration of the acid granite massif. These heterogeneities promote less tortuous pores or paths, making these clays more permeable. Finally, other stabilization studies and improvements to hydraulic products and binders should favor the use of the studied clay as improved backfill or drilling muds.

Physico-Chemical Features of the Kpassa Reservoir, Northern Benin, with Emphasis on Its Trophic State: A Preliminary Study

This work presents recent data on the physico-chemical properties and the trophic status of Kpassa reservoir at eighteen locations from August 2014 to February 2015. Seventeen physico-chemical parameters were measured and data obtained were statistically analyzed. The descriptive statistics showed their variations (minima-maxima) as follows: pH (4.65 - 7.30), temperature (25.1°C - 29.9°C), dissolved oxygen (1 - 5.79 mg/L), oxydability (0.32 - 10.88 mg O2/L), electrical conductivity (55 - 77 μS/cm𕒵), TDS (76 - 94 mg/L), turbidity (15.70 - 274.40 NTU), transparency (0.24 - 1.55 m), suspended matter (3 - 92 mg/L), total phosphorus (0.25 - 1.90 mg/L), orthophosphate (0.08 - 0.61 mg/L), nitrate (undetected 5.50 mg/L), nitrite (undetected 0.79 mg/L), ammonia (undetected 0.36 mg/L), chlorophyll a (7.20 - 2334.6 μg/L), silica (4.34 - 15.67 mg/L) and N/P ratio (0.08 - 42.62). These parameters were mainly influenced by agricultural activities and climatic conditions. The restriction or the removal of the use of chemical fertilizers in agricultural activities in Kpassa reservoir basin was recommended. The highest values of Pearson and Spearman correlations were observed across TDS and conductivity (0.967;0.951), turbidity and oxydability (0.924;0.665), turbidity and chlorophyll a (0.884;0.663), turbidity and suspended matter (0.982;0.793), suspended matter and transparency (𕒴.781;𕒴.819), suspended matter and nitrate (𕒴.813;𕒴.839), suspended matter and oxydability (0.919;0.602) and suspended matter and chlorophyll a (0.879;0.656). Carlson’s trophic state index (TSI) values varied between 36 and 66 showing that Kpassa reservoir was eutrophic in August and mesotrophic to oligotrophic during the other months of the sampling period. ANOVA and Kruskal-Wallis test indicated that there were no significant differences between sampling stations.

Assessment of the Physico-Chemical Pollution of a Water Body in a Perspective of Integrated Water Resource Management: Case Study of NokouéLake

Nokoué Lake is the most important surface of brackish waters of Benin and one of the biggest West African lagoons, in point of view of its surface (about 150 km2), its productivity and exploitation. The aim of this study is to monitor the temporal and spatial variation of physico-chemical parameters of Nokoué lake water for its sustainable management. A total of twenty (20) points of sampling have been followed during a period of one year. The results of the monitoring reveal low dissolved oxygen and high concentration in phosphorus and chlorophyll a, sign of eutrophication. In addition, nutrient concentrations (nitrites, phosphates, nitrates) responsible for the phenomenon compared to water quality assessment grid of the Organisation for Economic Co-operation and Development, (OECD) used to classify the waters in the range of hyper-eutrophic waters characterized by the proliferation of aquatic plants. So some measures have been proposed to remediate to this pollution in order to an integrated management.

Chemical Evolution of the Continental Terminal Shallow Aquifer in the South of Coastal Sedimentary Basin of Benin (West-Africa) Using Multivariate Factor Analysis

In southern Benin, where population is growing and water demand for domestic activities is increasing, water balance assessment constitutes a serious concern about sustainability of water resources. Major ions have been employed with statistical methods to identify geochemical processes controlling groundwater quality. Multivariate statistical analysis (principal component analysis “PCA” and hierarchical cluster analysis “HCA”) revealed the main sources of groundwater mineralization. According to the hydrochemical data and the methods of treatment, groundwater mineralization in the investigated aquifer is caused by four main processes: 1) mixing with Nokoué lake and Porto-Novo lagoon salt water causing salinity to increase in the southern part of the aquifer;2) anthropogenic activities;3) cation exchange process;and 4) soil CO2 diffusion providing a large proportion of bicarbonates.

Study of the Sediments of the Dam of Okpara (Benin): Physico-Chemical Characterization and Speciation of Iron and Manganese

Iron and Manganese contents and parameters including pH, conductivity, and organic matter contents were determined in the sediments of the Okpara dam in Northern Benin. Fifteen samples were collected during a one-month period and analysed in laboratory using the method of sequential extraction of Tessier. The analyses indicated that sediments contained high concentrations in reducible fraction of Iron and relatively high contents of exchangeable fraction, acidhydrolysable fraction and residual fraction of Manganese. The findings of this study confirmed the hypotheses that the meal contents of the sediments were relatively high and varied according to the geochemical phases.

Evaluation of Nitrogen and Phosphorus Wastes Produced by Nile Tilapia (<i>Oreochromis niloticus</i>L.) Fed <i>Azolla</i>-Diets in Earthen Ponds

Nitrogen (N) and phosphorus (P) wastes produced by Nile tilapia Oreochromis niloticus L. fed Azolla, an aquatic atmospheric nitrogen fixing fern, was evaluated for 90 days in pond experiment. Six isonitrogenous (29.2% crude protein) and isoenergetic (16.9 Kj·g–1) diets A0, A10, A20, A30, A40 and A50, containing 0%, 10%, 20%, 30%, 40% and 50% of Azolla meal (AM) respectively, as partial fishmeal (FM) substitutes, was provided to experimental fish. The Azolla-free diet A0 served as a control. Fish specific growth rate (SGR) was higher with the control diet, the lower values being obtained in A50-fed fish (P Azolla could be used in diet to sustain Nile tilapia growth and as “environmentally-friendly” ingredient to limit P loss, while providing N to the field, beneficially in tropical marshland pond where this nutrient is already limiting.

Assessment of Some Heavy Metals in Fresh Fish (Oreochromis aureus): Case of Toho Lake in South Eastern Benin, West Africa

The protection of aquatic ecosystems is of great importance to maintain the biological balance necessary to secure healthy foods therein imbedded. Toho Lake, located to the south east of Benin, is threatened by pollution emanating from anthropogenic activities with the use of chemical fertilizers, effluent of domestic waste, particularly human and animal excrement with neighbourhood effluents. This study aimed at assessing some heavy metals in fresh fish (Oreochromis aureus) of Toho Lake in order to secure healthy food for the population and protect the ecosystem. Samples of water and fishes were collected and analyzed by HACH DR 3900 after treatment. Results revealed a mean oxygenation of water (4.95 mgo2/l), Biochemical Oxygen Demand (21.5 mgo2/l), Chemical oxygen Demand (149, 39 mg/l) with the nitrogen in Nitrate (NO3: 0.18 mg/l), ammonium nitrate (N-N: 0.47 mg/l), and phosphorous (2.06 mg/l) to be very high. The highest contents of heavy metals obtained in the fresh fish were cadmium (32.25 mg/kg), copper (115 mg/kg), lead (8.25 mg/kg), and zinc (90.75 mg/kg) and revealed that the fishes of Toho lake were polluted. The finding allowed us to conclude that the pollution of the lake and the fish carnage are due to anthropogenic pollution through chemicals spilling. Some protection methods of the lake and ecosystem are proposed in order to keep the fish safe and protect the well-being of the population.

Microbiological Pollution Indication as Tracer for the Pollution of Well Water: The Example of the District of Abomey-Calavi (Benin)

Water is indispensable at life. Resources in waters of the township of Abomey-Calavi are of national importance. The township of Abomey-Calavi is very close to the biggest plan of water Beninese lagoon: The Nokoué lake. Besides, not only the waters of the ground water are consumed by the majority of the population from the traditional well, but also, the underground waters of the terminal continnental of the township of Abomey-Calavi are exploited intensely by the Society Nationnale of the Waters of Benin (SONEB) to nourish in drinking water in the townships of Abomey-Calavi, of Cotonou the biggest city of the country and Sèmè. The microbiological parameter followup (total coliforms, coliforms thermotolerants and enterrococcis) to the level of many traditional well and deep boring and some different points of Nokoué lake were the object of a treatment of data by the establishment of card of fecal contamination of waters natural of the region, that informs us on the quality of waters by the slant of a microbiological quality indication that calculates itself according to the method of Bovesse and Depelchin (1980). The survey of the microbiological contamination indication, succeeds to the establishment of seasonal cards of quality of waters.

Eco-Toxicological Approach as a Contribution to Integrated Water Management on Okpara Dam at Kpassa in Benin: Evaluation of Contamination of Fish and Surface Water by Organochlorine Pesticides

The paper explores the degree of pollution of organochlorine pesticides in fish and water in the dam at Kpassa on a tributary of Okpara River that is pumped by Benin National Water agency (SONEB) in supplying drinking water to supply the city of Parakou. Doing so, fourteen parameters of organochlorine are analyzed. Most of obtain organoclorine concentration in water and fish below is indicated critical values. However, DDT and endrine concentration in water is slightly above legal tolerable values. Hexachlorobenen and dieldrine concentrations are three times higher than legal limit value while aldrine is ten times higher. However, heptachlore is double concentrated in fishery while aldrine (endrine, dieldrine aldrine, lindane, hexachloro-benzene, DDT) is found in the dam fish and surface water three times concentrated than tolerated value. These levels of concentrations result from the intensification of organoclorine pesticide used in agriculture especially in cotton production. These are caused by the chemical application accumulated in soil and through the food value chain system. Therefore, it is very important to extract sediment from the reservoir by dredging in oder to renew the ecosystem of the dam. To persistently manage the basin water resources, it is imperatively important to observe a significant behaviour changed from all stakeholders.

Influence of Salinity on Duckweed Growth and Duckweed Based Wastewater Treatment System

The growth of duckweed (Spirodela polyrrhiza) was investigated in an outdoor batch system under 15 different conductivities ranging from 200 μS/cm to 3000 μS/cm with average 110 μmol/m2 daylight intensity. The growth was performed in an anaerobically treated domestic wastewater using an initial plants population of 50 fronds. Increase in Relative Growth Rate—RGR—(in terms of fresh weight and number of fronds) had a significant non-linear (polynomial) relationship with the conductivity. The maximum RGR related to fresh weight of 0.176 was observed at the conductiviity of 1200 μS/cm while the maximum RGR related to fronds number was 0.193 at the conductivity of 800 μS/cm. The optimum range for duckweeds growth was found to be between conductivities of 600 μS/cm and 1400 μS/cm. The maximal rates of removal of COD of 14.5 mg/day, of 0.65 mg/day, NTK of 15.68 mg/day, faecal coliforms of 100% and turbidity of 80.8% were observed in this range. The COD and PO42- removal rates were highly correlated to the growth rate, with the correlation factor of up to 0.783 and, then to the conductivity. The NTK reduction was positively related to the conductivity.

Study of Microbiological Quality along the Water Chain in Belbedji in the Republic of Niger

This work deals with the microbiological study along the water chain in Belbedji, a local government in the northwest of the Zinder region in the Republic of Niger. For this study, two (2) standpipes, thirty (30) families and ninety (90) samples were selected in order to follow the variation of water microbiological quality. For that the parameters studied are the total coliforms, the fecal coliforms and the E. coli. From these parameters we calculated the indication or the index of the microbiological quality (MQI) by the method of Bovesse and Depelchin, 1980. The variations of the fecal contamination at the level of the families in the different phases are represented on maps. At the water marker, 100% of families have good microbiological quality. After the transport of water, on 3.33% of the families the quality of the water deteriorated. After water storage, 16.66% of families had deteriorated water quality, with the passage of fecal contamination from zero to low on 13.33% of families, and fecal contamination from zero to moderate 3.33% of families.

Sediment Speciation from Dekin Groundwater at District of Dangbo (South Benin)

The objective of this research is to determine the physicochemical elements contained in the groundwater and in the deposits originating from these waters of the Arrondissement of Dêkin, Commune of Dangbo in the South of Benin. Physical parameters were measured from the multi-parameter and the chemical parameters by reagent assays. The precipitate from the groundwater was studied by speciation. The different assays were carried out using the Hach Lange DR2800 Spectrophotometer. The data processing was done with different software including ArcGis 10.1, Diagram.Ink of Roland SIMLER and PHREEQC 2.17.4137. Strong mineralization of the deposit from the drilling water was indicated in these three elements: Copper (220.1 mg/kg), iron (2528 mg/kg) and zinc (239.5 mg/kg) whose contents are higher than the French guideline values for heavy metal content in sediments in mg/kg. The calculation of the Saturation Indices of the drilling water shows saturation with respect to Goethite and Hematite. All these results have led us to conclude that the high content of Metallic Trace Element (MTE) in the deposit and especially of the iron in the drilling water originates from the dissolution-precipitation of the aquifer rock.

Negative Impacts of the Practices of Acadjas on the Aheme Lake in Benin

The objective of this study is to reveal the negative impacts of the practices of acadjas on the Aheme lake in Benin. Various material and methods were used for the measures of the physicochemical parameters such as: colorimetric HACH DR/890, the multiparameter WTW 340i and specific kits for the dosage of minerals. Also, the investigations were made with the resources by persons. It emerges from this study that the practices of acadjas asphyxiate and disturb the lake species. In fact, the concentrations in dissolved oxygen became very weak (1595 mg/L to 3740 mg/L), and the contents of nitrites (2, 25 mg/L to 14, 5 mg/L), suspension materials and turbidity are raised. The consequences both on the aquatic fauna and on the vegetation of the bank are worrying. The waterside populations are also threatened. Some actions in an attempt to regulate the practice of acadjas and promote reforestation of the lagoon bank need to be put in place.

Physico-Chemical Characterization of Waters and Sediments of Basins in the Cotton Area in Benin: Case of the Alibori Basin in the Commune of Banikoara North of Benin

The Alibori Basin, with an area of 13,400 km2, is a tributary of the Niger River in Benin. It is a river that passes through the potentially agricultural area of Benin. The waters of the river are useful for wildlife and are used for various purposes (drinking water, laundry, domestic activities). They regularly receive the discharges and drainage of the residues of the chemical fertilizers and pesticides not used by crops during the cultivation of the river and watershed bank. This study aims to assess the impact of the agricultural inputs on the quality of the waters from Alibori river on the basis of its physico-chemical characteristics and concentrations in Trace Metal Elements such as Zn, Pb, Cd and Cu. Seven (7) sites were selected along the river. Concentrations of , , , ?, Cu2+ and Zn2+ were measured using a spectrophotometer DR 1800 and that of Pb and Cd by Metalyse. The Metal Trace Elements were measured in the Alibori river sediments after being treated and mineralized using aqua regia. The results revealed that Alibori river characteristics varied with seasons and its waters and sediments were polluted by metals, phosphates and nitrites. The pollution of waters of the Alibori River was due to the intensive use of the chemical fertilizers and pesticides for agricultural purposes.

FVC and FEV Reference Values for Beninese Individuals Aged 17 - 20 Years

Background: 1) To determine forced vital capacity (FVC) and forced expiratory volume in one second (FEV) for Beninese individuals of both sexes aged 17 - 20 years;2) Compare the observed values to those calculated based on the algorithms of the spirometer used. Materials and Methods: The FVC and FEV values were first measured using a Micro Quark spirometer and then calculated from equations for the European Respiratory Society-93 (ERS-93) in 148 subjects, including 46 girls. In each age group, the measured values for the height of the subjects were considered the only variables used to calculate the equations for FVC and FEV with their 95% confidence intervals. The means of the FEV and FVC values were obtained by univariate analysis. Results: The calculated FEV and FVC values were significantly higher (p Conclusion: The correction factors incorporated in spirometers imported from Europe no longer seem appropriate to measure the physical characteristics of African subjects. The differences between the two methods of assessment should be used as new ethnic correction factors.

Bronchospasm Diagnosis in Motorcycle Taxi Drivers Exposed to Automotive Pollutants in Porto-Novo

Background: In African cities, chronic exposure to pollutants is the most common public health problem faced daily by motorcycle taxi drivers. In Benin, studies conducted on motorcycle drivers, have shown the presence of nitrogen oxides, carbon monoxide, sulfur dioxide, volatile organic compounds and particulate matter in ambient air, which may affect lung function. Aims: This study aims to diagnose potential respiratory problems among 48 motorcycle taxi drivers (47.02 ± 8.75 years) compared to a control group made up of 52 people (46.38 ± 8.81 years) in Porto-Novo, Benin. Methods: A questionnaire, two exploration pulmonary function tests and two 6-minute walk tests were used to identify symptoms and changes in respiratory variables that reveal the existence of bronchospasm. Results: The frequency of respiratory symptoms noted among motorcycle taxi drivers is higher than that recorded among members of the control group. We observed that motorcycle drivers at rest and after physical effort have significantly lower respiratory variables (FVC, FEV1, PEF, FEF25-75, FEF50 and FEF25) (p < 0.05) than those recoded in control group. Conclusion: It can therefore be concluded that, because of the relatively long duration of exposure among motorcycle taxi drivers, the inhalation of automobile pollutants, may cause respiratory problems in this population.

Characterization of Four University Hospitals Wastewater in Cotonou, Benin

Introduction: Because of the specificity of their care activities, hospital wastewater contains various contaminants such as germs, disinfectants, metals, pharmaceuticals and chemical reagents, potentially infectious or toxic, which can be harmful to living organisms, or create ecological damage. This study aimed to analyze the quality of wastewaters produced by university hospitals of Cotonou in Benin. Methods: We conduct an analytical cross-sectional study including 30 wastewater samples from selected hospitals. An analysis of variance was performed at the significance level of 0.05. Results: Microbiological analysis showed the presence of germs such as total coliform types, faecal coliforms, fecal streptococcus, staphylococcus, yeasts and Clostridium perfringens in hospital wastewater samples. There was a significant difference (p < 0.05) in the microbial loads of various germs, except staphylococcus, between hospitals. With regard to the physicochemical parameters, only the conductivity complied with the standards for the discharge of wastewater into the environment. A significant difference was noted between hospitals, for the electrical conductivity of wastewater (p < 0.05). The average levels of metals detected in the wastewaters were in line with Benin’s standards. There was no difference between the average concentrations of metals except for copper (p < 0.05). Conclusion: The wastewater produced by the university hospitals of Cotonou is of poor quality and therefore requires adequate prior treatment before discharge into the environment.

Physico-Chemical Characteristics of Gushing Water Aquifers in the Coastal Sedimentary Basin of Benin (West Africa)

The coastal sedimentary basin in southern Benin consists of monoclinal layers divided into two plateau zones (North and South) which are separated by a longitudinal depression ESE-WNW. The valleys of the main N-S-oriented rivers (Ouémé, Couffo and Mono) set the bondaries of the different plateau of the BSC (Coastal Sedimentary Basin). The present study, based on geology, hydrochemistry, temperature and log data available on boreholes, makes a physico-chemical characterization of the waters of the gushing aquifers of the coastal sedimentary basin of Benin. The gushing water boreholes are shared between the valleys of the main rivers of the BSC. Some of these boreholes are thermal with a water temperature between 38 and 69 degrees Celsius. The hydrogeological correlations established in the BSC in accordance to the North- South direction in the valleys of the main streams (Couffo and Ouémé) reveal that the captured aquifers are sands, marls and limestones that respond either in major discordance (northern zone) or above the sedimentation gaps (southern zone). Chemical analyses have shown that gushing thermal waters are mineralized in the south with a neutral to basic pH and are highly concentrated with bicarbonate, calcium and magnesium ions. In the North, on the other hand, thermal waters are acidic with a pH ranging from 4.8 to 5.9. The acidic nature of the northern waters is influenced by the crystalline base while the southern neutral to basic waters are influenced by the lithological nature (limestone and marl) of the aquifer. The random distribution of thermal water boreholes in the valleys of the main BSC streams is believed to be related to tectonic events.