Search

The Lobo is the source of drinking water for SODECI in the department of Daloa. The strong agricultural activity around it can lead to the dissipation of phytosanitary products into the environment. However, the transfer of pesticide residues from agricultural plots to this aquatic environment is little studied or even non-existent. The objective of this work is to determine the state of contamination of the Lobo River by phytosanitary products. The HPLC assays were carried out on water samples taken at the exit of the agricultural plots (upstream) and in the Lobo (downstream). These analyzes revealed the presence of residues of pesticides such as glyphosate, mancozeb 2,4-D and lambda-cyhalothrin at various concentrations. Indeed, at the exit of the agricultural plots (upstream) and in the Lobo (downstream), the average concentrations detected were respectively 0.89µg / L to 0.35 µg / L for glyphosate, 0.81µg / L at 0.38 µg / L for mancozeb, 0.5 µg / L at 0.39 µg / L for 2,4-D, and 0.06 µg / L at 0.02 µg / L for lambda-cyhalothrin. However, these values are higher than the international standard (WHO) which is 0.1µg / L at the exit of the plantations and in the waters of the Lobo except the values ​​of 2,4-D.

The aims of the work were to study the current quality of the water in Lake DOHOU used for drinking water supply through several physical, chemical analyses and using water quality indices (WQI). In addition, the question was whether the populations are at risk after drinking water of lake following a reduction of 50% and 75% in the median and maximum values of pesticides. Thus, the results of the pesticide monitoring program were incorporated into probabilistic human health risk assessment exercises. Water samples were collected over a period of one year. Pesticides were subjected to solid phase extraction and then analyzed using gas chromatography coupled to tandem mass spectroscopy. The other parameters were measured according to conventional methods. The results showed that the most frequently detected pesticides were aldicarb (79%), simazine (79%) and monolinuron (44%). They also showed the mean values of concentrations exceeding 1.5 μg/L. Metoxuron detected at a frequency of 29% showed the maximum average concentration (13.46 μg/L). Nearly 98% of the sampling points had at least one substance with an average concentration above the quality standard (0.1 μg/L) and 80% did not meet the total concentration standards. Cumulative risk quotient estimates after 50% or 75% abatement for frequently identified pesticides were greater than unity when extreme values for adults and children were considered. To determine the suitability of water for aquatic life, drinking water consumption and drinking water production, the water quality index (WQI), the heavy metal pollution (HPI) and the heavy metal evaluation (HEI) were calculated. The poor quality of the water was mainly related to pesticides, organic matter and microbiological parameters. Most of the nutrients and metals studied were often below the standards of drinking water and aquatic life. The Water Quality Index (WQI) has shown that water quality is degrading for these three modes of use and ranges from poor to marginal. The coupling of monitoring data with probabilistic estimates of human risks could be used by the Ivorian authorities to propose effective pollution management plans.

The water from natural springs in the city of Daloa is increasingly used by the population for its drinking water needs, even though its quality remains unknown. This study aims to determine the acquisition mechanism of the mineralization of these waters. Thus, physicochemical analyses were carried out on 10 spring water samples in February 2019. A summary statistical analysis of the results obtained shows that these waters are acidic (4.81 ≤ pH ≤ 5.39) and very weakly mineralised, with 50% of the conductivities below 100 μS·cm-1. The average iron (0.5 ± 1.02 mg/L) and manganese (0.61 ± 0.90 mg/L) contents show that these two parameters are increasing in the spring water. The Normalized Principal Component Analysis (NPCA) shows that mineralization is mainly controlled by surface inputs of elements (anthropogenic pollution), then the oxidation-reduction phenomenon and, finally, the water-rock contact (mineralization-residence time). Otherwise, the very low expression of water-rock contact (mineralization-residence time) in the acquisition of the mineralization reflects a short residence time of the water in the aquifer.

Determination of groundwater recharge is a major challenge in areas where rainfall is generally abundant. Variability and uncertainty are inherent in the estimation of recharge, and several methods are therefore recommended for its estimation at a regional level. In this study, we evaluated several methods for estimating recharge: the web GIS-based automated hydrological analysis tool (WHAT), water table fluctuation (WTF), hydrograph analyses, a recession curve displacement method, graphical separation, and empirical formulas. The annual recharge estimated by combining direct recharge and base-flow varied from 84 mm in 2019 to 66.4 mm in 2020. The mean direct recharge was about 44 mm in 2018 and 57.3 mm in 2019, representing about 4% and 5% of the respective rainfall. In 2020, this direct recharge was 43 mm, or about 6% of rainfall, around 25% lower than in 2019. Base-flow separation methods and recession curve displacement generally gave low results, whereas modified empirical formulas gave results close to those of the WTF method and were considered more consistent and reasonable. The regression curve displacement method implemented in the United States geologic survey (USGS) RORA program was found to be unsuitable for the study area. However, the other methods presented more reasonable results and could be used to estimate groundwater recharge in the study area.

Access to drinking water remains at the center of major development projects in Côte d'Ivoire, particularly in the Lobo watershed, located in the Precambrian basement area which is made up of magmatic and metamorphic rocks. The exploitation of the basin's groundwater is marked by numerous failures in the boreholes drilled. Thus, this study aims to implement a land management tool to identify areas of high aquifer productivity in order to reduce the failure rate of drilling in the Lobo watershed. The methodology adopted was to map the recharges and fractures through the coupling of agro-hydrological modeling with SWAT, remote sensing and GIS. The results obtained show that the SWAT model was sensitive to 13 hydrological parameters and particularly to groundwater-related parameters. The statistical and graphical criteria of the SWAT model showed good performances (the Nash-Sutcliffe "NS" and determination "R2" coefficients > 0.6) for the calibration period (1982-1993) and (NS and R2 ≥ 0.5) for the validation period (1979-1981). The monthly volumes of water recharging the groundwater tables range from 43 m3 to 5770 m3. The superposition of the recharge map on the fracturing map, based solely on geophysical surveys (presence of fractures), shows the potential sites for the installation of high flow boreholes. These sites could be located at the level of the mega fractures in the zones where the volumes of water reserves remain higher or equal to 3363 m3/month., Environmental and Water Sciences, public Health and Territorial Intelligence Journal, Vol. 5, No 2 (2021)

The supply of drinking water from aquifers of base remains problematic because of his complexity. The combination of several methods is more adapted for the mapping of water establishment favorable areas. This study is focused on water points establishment favorable areas mapping. The methods used are remote sensing, pump tests sheets for determining aquifers and saprolites thickness. To determine the recharge, GR2M Method and drainage density has been used. The digital elevation model (DEM) has been used to generate slopes and drainage density maps. The thematic maps obtained combined under GIS to produce water potentiality map. The results obtained have been with exploitation rates. Three classes of potentialities have been identified. These are classes of high potentialities in groundwater which cover approximately 20% of the study area. It occurs mainly in central areas where there are sedimentary formations usually captured by the drilling. These areas are generally located in the central part, mainly in areas where there is low slope, important with a thick layer of saprolites.

Mining is a major concern for the availability of groundwater resources due to the continual pumping out for pit dewatering. The objective of the study is to assess the impact of mining on the functioning of the aquifer system of the Yaoure Gold Project area. The methodology adopted was to first caracterize the aquifer system by producing the fracturing map from remote sensing. Endeed, the water level in the aquifer system was determined by the Castany method. The piezometry was studied in low and high water in order to determine the recharge and discharge zones and to follow the behaviour of the water in the aquifer system. Finally, the analysis of pumping test sheets was used to determine the hydrodynamic characteristics of the aquifer. The results obtained show 170 lineaments oriented in the N-S, NE-SW and NW-SE directions. The recharge of the aquifer is 46.5 mm/year with discharge zones observed in the north-east and south sectors and a recharge zone in the north of the study area. Water level variations in some boreholes and the determined transmissivity values varying between 1.85.10-6 and 3.5.10-4 m2/s (average of 2.47.10-5 m2/s), indicate a probable influence of pumping on the water level in the aquifer. Groundwater flows preferentially in a west-east direction and could generally discharge into the Bandama River. The hydraulic conductivities vary between 1.23.10-7 and 1.32.10-5 m/s with an average of 3.3710-6 m/s. The specific flow rates vary between 0.05 and 3.6 m3/h/m and the average value is 0.61 m3/h/m.

In order to assess the health risks associated with the ingestion of heavy metals or trace metal elements (TME) contained in foodstuffs from market garden crops, we sampled the tomato, cabbage, onion and leaves of 'onions and lettuce grown in the lowlands of the town of Daloa. The concentrations of ETM contained in these market garden products were determined by an Atomic Absorption Spectrophotometer (AAS) using three methods such as the flame method (Zn), the oven method (Pb, Cd, As, Cr, Ni) and the hydride (Hg) method. The results obtained showed that the heavy metals studied are present in fruits and vegetables with the most important Zn, Cr and Ni contents. However, metals such as arsenic, mercury and zinc present a concentration higher than that of the standard in force for the foodstuffs studied. Thus, the consumption of market garden products from cultivated soils in the areas studied could present dangers for the exposed population. Indeed, the study of the health risks associated with the ingestion of these vegetables has shown that for arsenic and zinc the determined Danger Quotient are all greater than 1. Which means that these vegetable crops present risks. related to the ingestion of zinc and arsenic. this means that the exposed population is theoretically out of danger. The values obtained from the Health Impact (SI) are all less than 1 for the population surveyed. On the other hand, for the estimated population of the city of Daloa we observe an IS> 1.

Rice is a strategic axis of socio-economic development of the region of Denguele because of the population increase. In spite of the essential role which plays the rice in the consumption of the population in developing countries, its production remains always insufficient. National policy of Côte d'Ivoire regarding rice knew a development at the beginning of 1970s in this north region of the country. This is not the case now because of lack of follow-up of many projects and malfunction of structures management. So today, the evaluation of the projects executed within the framework of a rice crop campaign requires the manipulation of a big quantity of heterogeneous data. The design of an appropriate management tool is necessary to organize and communicate information to facilitate decision making. The adopted approach is the one of a geodatabase which consists of the elaboration and the implementation of the data in a relational database management system. The data were modeled according to the Entity-Relationship formalism based on MERISE method which is characterized by three levels: conceptual, logical and physical. The result of this work indicates an unequal distribution of rice projects in this region. They are all concentrated around the town of Odienne which occupies about 41% of the cultivated area at the expense of other localities. This GIS highlights the benefits of implementing a geographic database for the management of a rice project.