The variability of ocean circulation and sea surface temperature (SST) in the tropical Atlantic, especially in the Gulf of Guinea (GG), defines this region as exceptionally rich from an oceanographic perspective. The ...The variability of ocean circulation and sea surface temperature (SST) in the tropical Atlantic, especially in the Gulf of Guinea (GG), defines this region as exceptionally rich from an oceanographic perspective. The Guinea Current (GC), as the major surface current, plays a significant role in marine productivity and coastal upwelling in the GG. This coastal upwelling is known to influence the climate of the surrounding region, primary productivity and local fisheries. Studies on GC variability and its impact on this coastal upwelling have highlighted that the upwelling downstream of Cape Palmas is influenced by GC detachment, topographic variations and advective processes leading to significant vertical mixing. This study aims to analyze the interannual variability of the GC and its impact on coastal upwelling using the Coastal and Regional Ocean COmmunity model (CROCO). The model’s evaluation is conducted using observational data, specifically Geostrophic and EKman Current Observatory (GEKCO) and Ocean Surface Current Analysis (OSCAR) for currents, and Air-sea Fluxes for the global Tropic ocean-description (TROPFLUX) and Optimum Interpolation-Sea Surface Temperature (OI-SST) for temperature. Thus, the model evaluation indicates that it accurately replicates ocean circulation and SST patterns in the tropical Atlantic and the GG. The joint analysis of upwelling indices (surface and intensity) and the position of the GC core allowed us to conclude that the displacement of the GC core does indeed influence the upwelling indices in the northern part of GG. However, other oceanic and atmospheric mechanisms such as vertical diffusion and horizontal advection as proposed by previous studies may also affect the year-by-year variability of coastal upwelling in the northern GG.展开更多
Renewable energies are of major interest due to their inexhaustible and clean nature, with minimal impact on the environment. Numerous technological pathways exist in this field, each distinguished by the materials us...Renewable energies are of major interest due to their inexhaustible and clean nature, with minimal impact on the environment. Numerous technological pathways exist in this field, each distinguished by the materials used and their implementation principles. However, the cost-efficiency ratio remains a significant challenge for researchers. Currently, organic materials are gaining popularity due to their relatively low cost. However, their performance, particularly in terms of conversion efficiency, still requires improvements. This study focuses on optimizing the organic photovoltaic cell ITO/MoO3/CARAPA/PCBM/Alq3/Al using SCAPS. Several parameters were considered, such as layer thickness, recombination center density, and doping, to improve the cell’s performance. The optimal parameters obtained include an efficiency of 3%, a fill factor of 81.67%, an open-circuit voltage of 1610 mV, and a short-circuit current of 2.28 mA/cm2. The study also revealed that doping the phenyl-C61-butyric acid methyl ester (PCBM) layer has a significant impact on efficiency and short-circuit current, improving these parameters up to a certain point before causing degradation due to increased recombination. Furthermore, high doping of the tri (8-hydroxyquinoline) aluminum (Alq3) layer improves performance up to a critical threshold, after which degradation is also observed. In contrast, doping the molybdenum trioxide (MoO3) layer does not have a notable impact on cell performance. Regarding the thickness of the active Carapaprocera (CARAPA) and PCBM layers, non-optimal values lead to a decrease in performance. Similarly, an optimal thickness of the Alq3 layer significantly improves efficiency. These results highlight the importance of parameter optimization to maximize the efficiency of organic solar cells.展开更多
This study assessed the contribution of climate projections to improving rainfall information for cocoa crops in the central and southern regions of Côte d’Ivoire. Particular attention was paid to fourteen local...This study assessed the contribution of climate projections to improving rainfall information for cocoa crops in the central and southern regions of Côte d’Ivoire. Particular attention was paid to fourteen localities in these two climatic zones. Simulation data were obtained from the CORDEX ensemble and observation data from CHIRPS. They cover the period 1991-2005 for the reference period and the future period from 2021 to 2050 for the RCP4.5 and RCP8.5 scenarios. In addition, the study was based on the water requirements necessary during the critical phase of the cocoa tree (the flowering phase) for a good yield from the cocoa production chain on the one hand, and on a selection of three climate indices CDD, CWD and r95PTOT to study their spatio-temporal changes over two future periods 2021-2035 (near future) and 2036-2050 (medium-term) on the other. These climatic indices influence cocoa cultivation and their use in studies of climatic impacts on agriculture is of prime importance. The analysis of their spatio-temporal changes in this work also contributes to providing climate services based on rainfall, to which cocoa crops are highly sensitive. Our results show that the CDD and CWD indices vary from one region to another depending on latitude. For the fourteen localities studied, the number of consecutive dry days (CDD) could increase between now and 2050, while the number of consecutive wet days (CWD) could decrease over the period 2021-2035 and then increase over the period 2036-2050. The localities of Tabou, Aboisso and San-Pedro record high numbers of CDD index and CWD index for both projection scenarios. In comparison with the RCP4.5 and RCP8.5 scenarios, these results show that the RCP8.5 scenarios are having an impact on cocoa growing in Côte d’Ivoire.展开更多
The explosive technological improvement of photovoltaic systems as well as the necessity of populations to come to less expensive energy sources, that have led to an implosion at the level of solar panel manufacturers...The explosive technological improvement of photovoltaic systems as well as the necessity of populations to come to less expensive energy sources, that have led to an implosion at the level of solar panel manufacturers. This causes a large flow of these equipments to developing countries where the need is high, without any quality control. That conducted an experimental investigation on the performance characteristics of a 250 wp monocrystalline silicon photovoltaic module in other to check the verification and quality control. Most of these PV panels which often have missing informations are manufactured and tested in places that are inadequate for our environmental and meteorological conditions. Also, their influences on the stability of internal parameters were evaluated in order to optimize their performance. The results obtained at maximum illumination (1000 w/m<sup>2</sup>) confirmed those produced by the manufacturer. The analysis of these characteristics showed that the illumination and the temperature (meteorological factors) influenced at most the stability of the internal characteristics of the module in the sense that the maximum power increased very rapidly beyond 750 w/m<sup>2</sup> but a degradation of performance was accentuated for a temperature of the solar cells exceeding 50°C. The degradation coefficients were evaluated at -0.0864 V/°C for the voltage and at -1.6248 w/°C for the power. The 10° inclination angle of the solar panel proved to be ideal for optimizing overall efficiency in practical situations.展开更多
This study assesses the projected changes in the climate zoning of Côte d’Ivoire using the hierarchical classification of principal components (HCPC) method applied to the daily precipitation data of an ensemble...This study assesses the projected changes in the climate zoning of Côte d’Ivoire using the hierarchical classification of principal components (HCPC) method applied to the daily precipitation data of an ensemble of 14 CORDEX-AFRICA simulations under RCP4.5 and RCP8.5 scenarios. The results indicate the existence of three climate zones in Côte d’Ivoire (the coastal, the centre and the north) over the historical period (1981-2005). Moreover, CORDEX simulations project an extension of the surface area of drier climatic zones while a reduction of wetter zones, associated with the appearance of an intermediate climate zone with surface area varying from 77,560 km<sup>2</sup> to 134,960 km<sup>2</sup> depending on the period and the scenario. These results highlight the potential impacts of climate change on the delimitation of the climate zones of Côte d’Ivoire under the greenhouse gas emission scenarios. Thus, there is a reduction in the surface areas suitable for the production of cash crops such as cocoa and coffee. This could hinder the country’s economy and development, mainly based on these cash crops.展开更多
Water stress early detection is essential for precision farming to improve crop productivity and product quality. The methods usually used are destructive, long and expensive. In this work, we used hyperspectral chlor...Water stress early detection is essential for precision farming to improve crop productivity and product quality. The methods usually used are destructive, long and expensive. In this work, we used hyperspectral chlorophyll fluorescence technology as a rapid, non-destructive approach to detect the water deficiency of eggplant plants using their spectral footprint. So, an experiment was made on 54 eggplant plants subjected to three water treatments: normal irrigation (T<sub>100</sub>), intermediate irrigation (T<sub>50</sub>) and no irrigation (T<sub>0</sub>). The fluorescence spectra were acquired in vivo and in situ using a USB4000 spectrometer from Ocean optics. For the classification of the plants subjected to three water treatments, we used three pretreatments of the raw hyperspectral data in order to suppress the non-informative variability present in these spectra and to obtain robust models. These are the Savitzky-Golay smoothing (SG), the standard normal variable (SNV) and the first derivative of Savitzky-Golay (SG-D1). The preprocessed data were then subjected to two partial least squares discriminant analyses (PLS-DA): Hard PLS-DA and Soft PLS-DA. These statistical approaches are suitable for large samples as it reduces the dimensionality of the data but improves the accuracy of the prediction. The SG-D1 combined with the Soft PLS-DA gave the best discrimination of plants with scores of sensitivity, specificity and total efficiency respectively of 97.33%, 94% and 95% for calibration, 6 days after hydric stress induction. For the plants used for the prediction, the scores are 86%, 91% and 90% respectively. This study shows that hyperspectral chlorophyll fluorescence spectroscopy is a fast and non-destructive technology allowing early detection of water stress in eggplant plants.展开更多
The buoyancy flux Bo at the air/sea interface is very useful to understand the variability of the stratification of the mixed layer, the oceanic mixing, the phytoplankton dynamics and then the coastal upwelling. The a...The buoyancy flux Bo at the air/sea interface is very useful to understand the variability of the stratification of the mixed layer, the oceanic mixing, the phytoplankton dynamics and then the coastal upwelling. The atmospheric reanalysis ERA5 and the oceanic reanalysis ORAP5 data have been used in this study to describe the sea surface Bo and, its influence on the variability of the mixing in the mixed layer and consequently on the coastal upwelling along the northern coast of the Gulf of Guinea. The Bo is negative along the coast and, is characterized by a seasonal variability dominated by the thermal buoyancy flux. This study has also shown that the mixing layer is very shallow along the coast and deeper offshore. The negative value of the Bo increases the stratification of the mixed layer and reduces the mixing. This could explain why the mixed layer is shallow in this region. This work suggests that an increasing trend of the global warming could have dramatic impact in this area by increasing the stratification in the mixed layer and would contribute to reducing the coastal upwelling intensity.展开更多
In this work, ten medicinal and nutritional leaves samples of <em>Hibiscus sabdariffa</em> Linn imported from Mali and Burkina Faso in C<span style="white-space:nowrap;"><span style=&quo...In this work, ten medicinal and nutritional leaves samples of <em>Hibiscus sabdariffa</em> Linn imported from Mali and Burkina Faso in C<span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">ô</span></span></span>te d’Ivoire and sold on the market were collected. The analysis of these plants using High Purity Germanium detector (HPGE) gamma spectrometry showed the activity concentrations of <sup>226</sup>Ra, <sup>232</sup>Th, and <sup>40</sup>K varied respectively in the range of (1.74 - 0.11) × 10<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span></span></span>3</sup> Bq/kg, (6.72 - 0.61) × 10<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span></span></span>4</sup> Bq/kg and (4.65 - 0.54) × 10<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span></span></span>3</sup> Bq/kg1 in the leaves of <em>H. sabdariffa</em>. The Average Annual Committed Effective Dose (AACED) values from leaves this plant varied from 251.492 × 10<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span></span></span>6</sup> to 68.133 × 10<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span></span></span>6</sup> mSv/y. These values found are below 0.30 mSv/y, the world average value for an individual. These results show that there is no radiological risk in consuming “bissap” leaves.展开更多
Rice yellow mottle is considered the most destructive disease threatening rice production in Africa. Early detection of this infection in rice is essential to limit its expansion and proliferation. However, there is n...Rice yellow mottle is considered the most destructive disease threatening rice production in Africa. Early detection of this infection in rice is essential to limit its expansion and proliferation. However, there is no research devoted to the spectral detection of rice yellow mottle virus (RYMV) infection, especially in the asymptomatic or early stages. This work proposes the use of hyperspectral fluorescence and reflectance data at leaf level for the detection of this disease in asymptomatic stages. A greenhouse experiment was therefore conducted to collect hyperspectral fluorescence and reflectance data at different stages of infection. These data allowed to calculate nine vegetation indices: one from fluorescence spectra and eight from reflectance spectra. A t-test made it possible to identify, from the second day after infection, four relevant reflectance vegetation indices to discriminate healthy leaves from those infected: these are Photochemical Reflectance Index (PRI), Transformed Chlorophyll Absorption in Reflectance Index (TCARI), Structure Intensive Pigment Index (SIPI) and Simple Ratio Pigment Index (SRPI). The fluorescence index was less sensitive in detecting infection. The four significant vegetation indices for the detection of RYMV were then used to build and evaluate models for discriminating plants according to their health status by the supervised classification of support vector machine (SVM) at different stages of infection. The maximum overall accuracy is 92.5% six days after inoculation (6 DAI). The sixth day after inoculation would be the adequate day to detect RYMV. This plants discrimination was validated by the mean reflectance spectra and by the histograms showing the differences between the average reflectance vegetation indices values of the two types of plants. Our results demonstrate the feasibility of differentiating RYMV-infected samples. They suggest that support vector machine learning models could be developed to diagnose RYMV-infected plants based on vegetation indices derived from spectral profiles at early stages of disease development.展开更多
Black carbon is one of the primary aerosols directly emitted from biomass known to have strong absorbing properties. The INDAAF and PASMU observational field campaigns which took place (2018) in Abidjan (urban area) a...Black carbon is one of the primary aerosols directly emitted from biomass known to have strong absorbing properties. The INDAAF and PASMU observational field campaigns which took place (2018) in Abidjan (urban area) and Lamto (rural area) allow the analysis of Black carbon concentration at different time scales through real-time measurements using an analyzer named Aethalometer AE-33. Results presented here show at Lamto: 1) for the diurnal scale an average of 1.71 ± 0.3 μg⋅m<sup>-3</sup> (0.34 ± 0.09 μg⋅m<sup>-3</sup>) in the dry (wet) season;2) for the monthly scale an average of 1.14 ± 0.84 μg⋅m<sup>-3</sup>;3) on the seasonal scale, an average of 2.2 ± 0.02 μg⋅m<sup>-3</sup> (0.6 ± 0.19 μg⋅m<sup>-3</sup>) in the dry (wet) season. The black carbon variation at Lamto is seasonal with an amplification factor of 85.6. Regarding the urban area of Abidjan, due to sampling issues, our analyses were limited to daily, diurnal and weekly time scales. We observed: a) at a daily scale an average of 5.31.± 2.5 μg⋅m<sup>-3</sup>, b) diurnal scale, an average ranging from 6.87 to 13.92 μg⋅m<sup>-3</sup>. The analysis indicated that emissions from urban areas are more related to social and economic activities, with weekday concentrations (7.24 μg⋅m<sup>-3</sup>) higher than concentrations over the weekend (e.g. Saturday 6.59 μg⋅m<sup>-3</sup> and Sunday 6.00 μg⋅m<sup>-3</sup>). Moreover, BC concentration in Abidjan is quite noticeable compared to that of rural areas (Lamto). The ratio between the maximum values of the two areas is of the order of 5.86. In addition, concentrations in some urban areas are slightly above the daily threshold set by the WHO (10 μg⋅m<sup>-3</sup>). Therefore, the levels of urban BC concentrations are alarming whilst rural BC concentrations remain below daily WHO thresholds and are of the same magnitude as those of West African megacities. This study underlies that BC concentrations at Lamto are mainly related to biomass combustion sources while those from urban areas are related to traffic sources. The latter is permanently active, unlike those in rural Lamto, which is seasonal.展开更多
The split characteristics of the tropical Mesoscale Convective System (MCS) of April 9, 2018, in northern Ghana were studied using infrasound data measured by the mobile array (I68CI) which was deployed by C<span s...The split characteristics of the tropical Mesoscale Convective System (MCS) of April 9, 2018, in northern Ghana were studied using infrasound data measured by the mobile array (I68CI) which was deployed by C<span style="white-space:nowrap;">?</span>te d’Ivoire National Data Center (NDC) in collaboration with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). These infrasound measurements were made during a measurement campaign from January 1st, 2018 to December 31, 2018, in northeast Cote d’Ivoire, precisely in Comoe National Park. Graphic Progressive Multi-Channel Correlation (GPMCC) method based on a progressive study of the correlation functions was used to analyze and visualize data. The infrasound detection from this MCS shows clearly a division of the MCS structure into 2 distinct subsystems under the effect of internal and external constraints not well known but related to convection;a smaller subsystem in the north, associated with an area of intense rainfall of about 30 mm/hour and located at 9.5<span style="white-space:nowrap;">°</span>N - 2<span style="white-space:nowrap;">°</span>E with an azimuth of 70<span style="white-space:nowrap;">°</span> and, a large subsystem in the south, associated with a zone of high rainfall of about 96 mm/hour and located at 8.8<span style="white-space:nowrap;">°</span>N - 1.4<span style="white-space:nowrap;">°</span>E with an azimuth of 90<span style="white-space:nowrap;">°</span>. These two subsystems were located 200 km and 260 km from the I68CI station with frequencies of 2.3 Hz and 1 Hz respectively. The mesoscale convective systems in this region are moving from East to West and including several storm cells.展开更多
Rain flooding during June on the West Africa coastal area is analyzed by using the 95th and 75th percentiles, which represent extreme and intense rainfall events respectively. Thus, the contribution of these events th...Rain flooding during June on the West Africa coastal area is analyzed by using the 95th and 75th percentiles, which represent extreme and intense rainfall events respectively. Thus, the contribution of these events that reaches around 50% shows their impact on the rainfall in June. Atmospheric and oceanic factors influence the rain flooding. Indeed, the extreme events are associated with easterly waves propagating from 20<span style="white-space:nowrap;">°</span>E, while those of intense events are initiated around 5<span style="white-space:nowrap;">°</span>E. The impact of oceanic conditions exhibits the warming of the equatorial rail and the Atlantic cold tongue, the warming of the whole ocean basin and a north-south dipole of SST anomalies. The West African monsoon that reaches Abidjan corresponds to a low-level atmospheric flow, whose upward motion extends in latitude from the ocean to the continent. An increase of disturbance contributes to enhancing these events. This is confirmed by the inflow on to the continent of oceanic moisture coming from the ventilation by evaporation of warm water. In addition, the coupled ocean-atmosphere simulations are one of the best candidates that could help to better explain these dramatic events. This study is useful because of showing solutions that could help in adoption of policies for the risks management related to these events.展开更多
The severe drought observed in the Sahel during 1970s, 1980s and 1990s has deeply affected the population as well as the economies and the eco-systems of this climatic area. The GGW Initiative spearheaded by Africa Un...The severe drought observed in the Sahel during 1970s, 1980s and 1990s has deeply affected the population as well as the economies and the eco-systems of this climatic area. The GGW Initiative spearheaded by Africa Union in 2007 proposed to combat the land degradation and desertification by planting a wall of trees stretching from Dakar to Djibouti. A reforestation was then conducted in the Senegal’s GGW since 2006 as part as other areas in the Sahel. This paper aims to evaluate the carbon sequestration dynamics in the sites of the Senegal’s GGW over the last three decades. The method consists firstly of analyzing the evolution of land cover and land use dynamics based on ESA-CCI LC satellite data. There is an improvement of the surface areas of tree and shrub savanna of 11.40% (Tessekere), 8.25% (Syer) and 2.70% (Loughere-Thioly). The regreening of the different localities and a positive dynamic observed is explained by the return to normal rainfall and to reforestation actions, agroforestry practices, better management of natural resources undertaken. However, some non-reforested sites showed an opposite trend despite of the normal rainfall. Secondly, the results on land mapping are used as a proxy for the assessment of carbon stocks. The dynamic observed in vegetation cover since the beginning of the reforestation made it possible to sequester 5.8 million tons of carbon representing respectively 2.31% of African GGW. This gain in stored carbon is equivalent to 21.2 million tons of CO<sub>2</sub> captured in the atmosphere. Through this study, it appears that carbon storage becomes significant 8 to 10 years after the start of reforestation. An urbanization without respect for the environmental factors could be a danger for the climate (case of Ballou).展开更多
This study assesses the climate impact on the productivity of five sugarcane varieties (R579, SP711406, M2593/92, M1400/86, and SP701006) in the industrial plantations of Ferké 1 sugar complex. It is a contributi...This study assesses the climate impact on the productivity of five sugarcane varieties (R579, SP711406, M2593/92, M1400/86, and SP701006) in the industrial plantations of Ferké 1 sugar complex. It is a contribution to research efforts aimed at increasing the productivity of sugarcane varieties in the sugar fields. Also to support agricultural development and guarantee the income of planters. The sugarcane production data are from 2013 to 2017. Climatological data are measured and calculated continuously daily at the production site. In addition, the CMIP-5 (Coupled Model Intercomparison Project) climate database at 1<sup></sup><sup>º </sup>× 1<sup>º</sup> horizontal resolution was used for the predictability of crop yields of the 5 sugarcane varieties in the near future (2021-2050) and far future (2056-2075) to improve the quality of climate services to producers. The statistical methodological approach by multiple linear regression associated with the significativity test shows important and significant coefficients of determination (R<sup>2</sup> > 0.90) between the yields of sugarcane varieties with certain climatic parameters such as minimum and maximum temperatures, insolation, global solar radiation, and potential evapotranspiration. The impact of rainfall has not been directly evaluated because the linear models do not explicitly show sensitivities to this parameter and the total water requirements for the plot are completely assured by irrigation. The future climate projections analyzed only from extreme thermal parameters (Tmax and Tmin) highlight their strong sensitivities with yields from an idealized model. In this model, we have assumed that the water supply needed by sugarcane is always met by irrigation on different plots. Moreover, linear models do not evolve fast enough in time and changes due to external environmental constraints are not too important at the plot scale. The projected thermic parameters can thus constitute a limiting factor for the producibility of sugarcane varieties either by excess or by default. In addition, the linear models used allowed us to observe the behavior of yields with respect to observed past climatic conditions. However, for future yields, there is no way to know if these regressions have the ability to predict them since they are based on projected weather conditions (i.e. CMIP5 data) marked by uncertainties. Additionally, none of the regression equations have been tested against independent observations.展开更多
The Uranium-238 (<sup>238</sup>U), Thorium-232 (<sup>232</sup>Th) families and Potassium-40 (<sup>40</sup>K) are of terrestrial origin and contribute generally to an individual’s e...The Uranium-238 (<sup>238</sup>U), Thorium-232 (<sup>232</sup>Th) families and Potassium-40 (<sup>40</sup>K) are of terrestrial origin and contribute generally to an individual’s external exposure through our presence in this environment. They also contribute to the internal exposure through the ingestion of products and beverages such as water that are close to the earth. The aim of this work is to determine the committed effective dose or Total Indicative Dose (TID) due to gamma radioactivity of the borehole water from the Nord Riviera (NR) well field operated by the Côte d’Ivoire Water Distribution Company (SODECI) for the supply of drinking water to part of the population of Abidjan. In addition, the populations, with their habits, could use these borehole waters directly as drinking water. To this end, water samples from the seven (07) functional boreholes were collected and analyzed on a gamma spectrometry chain, equipped with an HPGe detector in the laboratory of the Radiation Protection Institute (RPI) of the GHANA Atomic Energy Commission (GAEC). The results of the specific activities of <sup>238</sup>U, <sup>232</sup>Th and <sup>40</sup>K obtained were transcribed into TID. As the natural radioactivity of the borehole water is high [1], the TIDs calculated from the activity results of the natural radionuclides<sup>238</sup>U, <sup>232</sup>Th, and <sup>40</sup>K vary for the seven boreholes from 0.150 to 0.166 mSv/yr with an average of 0.161 ± 0.034 mSv/yr. The TID of the control tower, where the borehole water is mixed and treated for household use, is equal to 0.136 ± 0.03 mSv/yr. The TIDs obtained are therefore all slightly greater than the WHO reference dose value of 0.1 mSv/yr. But all remain below the UNSCEAR reference dose of 0.29 mSv/yr.展开更多
The Tongon mine, the largest gold mine in C?te d’Ivoire, has been in operation since April 2010. However, to our knowledge to date, no study has been conducted on metallic contamination in suspended particulate matte...The Tongon mine, the largest gold mine in C?te d’Ivoire, has been in operation since April 2010. However, to our knowledge to date, no study has been conducted on metallic contamination in suspended particulate matter (PM<sub>10</sub> and PM<sub>2.5</sub>) where there is a lack of information on the carcinogenic and non-carcinogenic risk to human health associated with the exposure of populations in the Tongon area to these pollutants. The general objective of this study is to evaluate the level of contamination of PM<sub>10</sub>;PM<sub>2.5</sub> by heavy metals and their impact on the health of populations exposed to these pollutants in the Tongon gold mine area. The sampling and measurement of suspended particulate matter (PM<sub>10</sub> and PM<sub>2.5</sub>) were done using a MiniVol TAS passive air sampler. Heavy metal concentrations were determined by inductively coupled plasma mass spectroscopy (Nex ION 2000 ICP-MS, USA). The results indicate that the average concentrations of suspended particles (PM<sub>2.5</sub> and PM<sub>10</sub>) obtained are all above the recommended exposure limits. In addition, among the heavy metals contained in the suspended particles, the concentrations of arsenic and nickel are high and all above the standard limit values. The assessment of the health risks related to the inhalation of PM<sub>10</sub> particles reveals that their inhalation over a long period could cause a carcinogenic risk.展开更多
In the particular context of climate change in Côte d’Ivoire and the vulnerability of farmers to its effects, one of the major issues is how these changes could impact cocoa yields of cocoa production areas....In the particular context of climate change in Côte d’Ivoire and the vulnerability of farmers to its effects, one of the major issues is how these changes could impact cocoa yields of cocoa production areas. Thus, the objective of this study is to sustainably increase the resilience of all cocoa farming stakeholders to the impacts of climate change. The study was carried out in the central and southern areas of Côte d’Ivoire with a focus on eleven localities that have many communities of cocoa producers and a humid climate. The rainfall and temperature observation data using come from the CRU, they cover the historical period from 1971 to 2000 at 0.5<sup>o</sup> × 0.5<sup>o</sup> horizontal scale. As for the RCP4.5 and RCP8.5 climate scenarios, they come from the CORDEX database and cover the 2021-2050 period. The methodology is based on the calculation of climatic indices sensitive to cocoa cultivation which are the number of consecutive dry days (CDD), the number of consecutive wet days (CWD), the amount of rain during the rainy season and the maximum temperature above 33℃. The results show that for all the localities studied, indices such as CDD and CWD could experience an increase. In addition, the total amount of rain during the long rainy season (April to June) is calculated on the basis of the threshold of 700 mm representing the minimum annual precipitation during the rainy season necessary for good growth of the cocoa tree. It reveals that for the two scenarios the cumulative rainfall will all be greater than 700 mm. Regarding temperatures, the central and southern areas could have a low number of hot days (temperature greater than or equal to 33℃ which is the tolerable threshold for cocoa cultivation). The eleven localities, therefore, remain favorable areas for cocoa cultivation in terms of climatic conditions based on temperature and rainfall, despite the regional dimension of the effects of climate change and the associated constraints.展开更多
The radioactive isotopes of the decay series of uranium-238 (<sup>238</sup>U), thorium-232 (<sup>232</sup>Th) and potassium-40 (<sup>40</sup>K) occur naturally in varying amounts in...The radioactive isotopes of the decay series of uranium-238 (<sup>238</sup>U), thorium-232 (<sup>232</sup>Th) and potassium-40 (<sup>40</sup>K) occur naturally in varying amounts in groundwater. They are the subject of many measures, mainly because of the risk they represent from a public health point of view. The purpose of this study is to measure the radioisotope content of borehole waters from the north riviera (NR) catchment field of the Ivorian drinking water distribution company (SODECI). These measurements will make it possible to assess the absolute levels of radioisotopes in the water from SODECI’s boreholes used directly for drinking or swimming, and possibly the associated risk from a public health point of view. To achieve this, a sampling campaign from the seven functional boreholes and the control or treatment tower took place in July 2018 at the NR well field. The analysis of radionuclides by gamma spectrometry was carried out in the laboratory of the Radiation Protection Institute (RPI) of the Ghana Atomic Energy Commission (GAEC). The naturally occurring radionuclides identified during the borehole water samples analysis are <sup>238</sup>U, <sup>232</sup>Th, and <sup>40</sup>K. The results reveal that the specific activities of uranium vary from 0.45 ± 0.18 Bq/L to 0.55 ± 0.17 Bq/L with an average of 0.49 ± 0.15 Bq/L. Those of thorium vary from 0.66 ± 0.14 Bq/L to 0.78 ± 0.18 Bq/L with an average of 0.72 ± 0.16 Bq/L and potassium of 4.14 ± 0.53 Bq/L at 5.87 ± 0.60 Bq/L with an average of 5.32 ± 0.58 Bq/L.展开更多
Two simulations of five years (2003-2007) were conducted with the Regional Climate models RegCM4, one coupled with Land surface models BATS and the other with CLM4.5 over West Africa, where simulated air temperature a...Two simulations of five years (2003-2007) were conducted with the Regional Climate models RegCM4, one coupled with Land surface models BATS and the other with CLM4.5 over West Africa, where simulated air temperature and precipitation were analyzed. The purpose of this study is to assess the performance of RegCM4 coupled with the new CLM4.5 Land</span><span style="font-family:""> </span><span style="font-family:Verdana;">surface scheme and the standard one named BATS in order to find the best configuration of RegCM4 over West African. This study could improve our understanding of the sensitivity of land surface model in West Africa climate simulation, and provide relevant information to RegCM4 users. The results show fairly realistic restitution of West Africa’s climatology and indicate correlations of 0.60 to 0.82 between the simulated fields (BATS and CLM4.5) for precipitation. The substitution of BATS surface scheme by CLM4.5 in the model configuration, leads mainly to an improvement of precipitation over the Atlantic Ocean, however, the impact is not sufficiently noticeable over the continent. While the CLM4.5 experiment restores the seasonal cycles and spatial distribution, the biases increase for precipitation and temperature. Positive biases already existing with BATS are amplified over some sub-regions. This study concludes that temporal localization (seasonal effect), spatial distribution (grid points) and magnitude of precipitation and temperature (bias) are not simultaneously improved by CLM4.5. The introduction of the new land surface scheme CLM4.5, therefore, leads to a performance of the same order as that of BATS, albeit with a more detailed formulation.展开更多
Sand is an important natural material for the construction of houses, work buildings and other public spaces. This work, which is one of the first contributions to the environmental quality of construction materials, ...Sand is an important natural material for the construction of houses, work buildings and other public spaces. This work, which is one of the first contributions to the environmental quality of construction materials, concerns the measurement of natural radioactivity in the lagoon sands collected in the district of Abidjan. Nineteen (19) samples of these sands are analyzed by gamma-ray spectrometry equipped with HPGe detector. The mean values obtained for <sup>226</sup>Ra, <sup>232</sup>Th and <sup>40</sup>K are respectively 7.76 ± 1.84 Bq·kg<sup>-1</sup>, 5.21 ± 1.36 Bq·kg<sup>-1</sup>, and 217.31 ± 5.03 Bq·kg<sup>-1</sup>. The estimated average value of radium equivalent (Raeq) is 31.94 Bq·kg-1. The results show that the average values obtained are far lower than the global limits of 35, 30, and 400 Bq·kg<sup>-1</sup> for the concentrations of <sup>226</sup>Ra, <sup>232</sup>Th and <sup>40</sup>K, respectively, and 370 Bq·kg<sup>-1 </sup>for the equivalent radium established by the United Nations Scienti<span style="white-space:nowrap;">fi</span>c Committee on the Effects of Atomic Radiation (UNSCEAR). Therefore, the use of the analyzed lagoon sand samples in the different construction sectors should not cause serious radiological effects on the populations living in the District of Abidjan. Our results provide new data on building materials radioactivity in C<span style="white-space:nowrap;">ô</span>te d’Ivoire and all over the World. They can also be used as a reference for future work.展开更多
文摘The variability of ocean circulation and sea surface temperature (SST) in the tropical Atlantic, especially in the Gulf of Guinea (GG), defines this region as exceptionally rich from an oceanographic perspective. The Guinea Current (GC), as the major surface current, plays a significant role in marine productivity and coastal upwelling in the GG. This coastal upwelling is known to influence the climate of the surrounding region, primary productivity and local fisheries. Studies on GC variability and its impact on this coastal upwelling have highlighted that the upwelling downstream of Cape Palmas is influenced by GC detachment, topographic variations and advective processes leading to significant vertical mixing. This study aims to analyze the interannual variability of the GC and its impact on coastal upwelling using the Coastal and Regional Ocean COmmunity model (CROCO). The model’s evaluation is conducted using observational data, specifically Geostrophic and EKman Current Observatory (GEKCO) and Ocean Surface Current Analysis (OSCAR) for currents, and Air-sea Fluxes for the global Tropic ocean-description (TROPFLUX) and Optimum Interpolation-Sea Surface Temperature (OI-SST) for temperature. Thus, the model evaluation indicates that it accurately replicates ocean circulation and SST patterns in the tropical Atlantic and the GG. The joint analysis of upwelling indices (surface and intensity) and the position of the GC core allowed us to conclude that the displacement of the GC core does indeed influence the upwelling indices in the northern part of GG. However, other oceanic and atmospheric mechanisms such as vertical diffusion and horizontal advection as proposed by previous studies may also affect the year-by-year variability of coastal upwelling in the northern GG.
文摘Renewable energies are of major interest due to their inexhaustible and clean nature, with minimal impact on the environment. Numerous technological pathways exist in this field, each distinguished by the materials used and their implementation principles. However, the cost-efficiency ratio remains a significant challenge for researchers. Currently, organic materials are gaining popularity due to their relatively low cost. However, their performance, particularly in terms of conversion efficiency, still requires improvements. This study focuses on optimizing the organic photovoltaic cell ITO/MoO3/CARAPA/PCBM/Alq3/Al using SCAPS. Several parameters were considered, such as layer thickness, recombination center density, and doping, to improve the cell’s performance. The optimal parameters obtained include an efficiency of 3%, a fill factor of 81.67%, an open-circuit voltage of 1610 mV, and a short-circuit current of 2.28 mA/cm2. The study also revealed that doping the phenyl-C61-butyric acid methyl ester (PCBM) layer has a significant impact on efficiency and short-circuit current, improving these parameters up to a certain point before causing degradation due to increased recombination. Furthermore, high doping of the tri (8-hydroxyquinoline) aluminum (Alq3) layer improves performance up to a critical threshold, after which degradation is also observed. In contrast, doping the molybdenum trioxide (MoO3) layer does not have a notable impact on cell performance. Regarding the thickness of the active Carapaprocera (CARAPA) and PCBM layers, non-optimal values lead to a decrease in performance. Similarly, an optimal thickness of the Alq3 layer significantly improves efficiency. These results highlight the importance of parameter optimization to maximize the efficiency of organic solar cells.
文摘This study assessed the contribution of climate projections to improving rainfall information for cocoa crops in the central and southern regions of Côte d’Ivoire. Particular attention was paid to fourteen localities in these two climatic zones. Simulation data were obtained from the CORDEX ensemble and observation data from CHIRPS. They cover the period 1991-2005 for the reference period and the future period from 2021 to 2050 for the RCP4.5 and RCP8.5 scenarios. In addition, the study was based on the water requirements necessary during the critical phase of the cocoa tree (the flowering phase) for a good yield from the cocoa production chain on the one hand, and on a selection of three climate indices CDD, CWD and r95PTOT to study their spatio-temporal changes over two future periods 2021-2035 (near future) and 2036-2050 (medium-term) on the other. These climatic indices influence cocoa cultivation and their use in studies of climatic impacts on agriculture is of prime importance. The analysis of their spatio-temporal changes in this work also contributes to providing climate services based on rainfall, to which cocoa crops are highly sensitive. Our results show that the CDD and CWD indices vary from one region to another depending on latitude. For the fourteen localities studied, the number of consecutive dry days (CDD) could increase between now and 2050, while the number of consecutive wet days (CWD) could decrease over the period 2021-2035 and then increase over the period 2036-2050. The localities of Tabou, Aboisso and San-Pedro record high numbers of CDD index and CWD index for both projection scenarios. In comparison with the RCP4.5 and RCP8.5 scenarios, these results show that the RCP8.5 scenarios are having an impact on cocoa growing in Côte d’Ivoire.
文摘The explosive technological improvement of photovoltaic systems as well as the necessity of populations to come to less expensive energy sources, that have led to an implosion at the level of solar panel manufacturers. This causes a large flow of these equipments to developing countries where the need is high, without any quality control. That conducted an experimental investigation on the performance characteristics of a 250 wp monocrystalline silicon photovoltaic module in other to check the verification and quality control. Most of these PV panels which often have missing informations are manufactured and tested in places that are inadequate for our environmental and meteorological conditions. Also, their influences on the stability of internal parameters were evaluated in order to optimize their performance. The results obtained at maximum illumination (1000 w/m<sup>2</sup>) confirmed those produced by the manufacturer. The analysis of these characteristics showed that the illumination and the temperature (meteorological factors) influenced at most the stability of the internal characteristics of the module in the sense that the maximum power increased very rapidly beyond 750 w/m<sup>2</sup> but a degradation of performance was accentuated for a temperature of the solar cells exceeding 50°C. The degradation coefficients were evaluated at -0.0864 V/°C for the voltage and at -1.6248 w/°C for the power. The 10° inclination angle of the solar panel proved to be ideal for optimizing overall efficiency in practical situations.
文摘This study assesses the projected changes in the climate zoning of Côte d’Ivoire using the hierarchical classification of principal components (HCPC) method applied to the daily precipitation data of an ensemble of 14 CORDEX-AFRICA simulations under RCP4.5 and RCP8.5 scenarios. The results indicate the existence of three climate zones in Côte d’Ivoire (the coastal, the centre and the north) over the historical period (1981-2005). Moreover, CORDEX simulations project an extension of the surface area of drier climatic zones while a reduction of wetter zones, associated with the appearance of an intermediate climate zone with surface area varying from 77,560 km<sup>2</sup> to 134,960 km<sup>2</sup> depending on the period and the scenario. These results highlight the potential impacts of climate change on the delimitation of the climate zones of Côte d’Ivoire under the greenhouse gas emission scenarios. Thus, there is a reduction in the surface areas suitable for the production of cash crops such as cocoa and coffee. This could hinder the country’s economy and development, mainly based on these cash crops.
文摘Water stress early detection is essential for precision farming to improve crop productivity and product quality. The methods usually used are destructive, long and expensive. In this work, we used hyperspectral chlorophyll fluorescence technology as a rapid, non-destructive approach to detect the water deficiency of eggplant plants using their spectral footprint. So, an experiment was made on 54 eggplant plants subjected to three water treatments: normal irrigation (T<sub>100</sub>), intermediate irrigation (T<sub>50</sub>) and no irrigation (T<sub>0</sub>). The fluorescence spectra were acquired in vivo and in situ using a USB4000 spectrometer from Ocean optics. For the classification of the plants subjected to three water treatments, we used three pretreatments of the raw hyperspectral data in order to suppress the non-informative variability present in these spectra and to obtain robust models. These are the Savitzky-Golay smoothing (SG), the standard normal variable (SNV) and the first derivative of Savitzky-Golay (SG-D1). The preprocessed data were then subjected to two partial least squares discriminant analyses (PLS-DA): Hard PLS-DA and Soft PLS-DA. These statistical approaches are suitable for large samples as it reduces the dimensionality of the data but improves the accuracy of the prediction. The SG-D1 combined with the Soft PLS-DA gave the best discrimination of plants with scores of sensitivity, specificity and total efficiency respectively of 97.33%, 94% and 95% for calibration, 6 days after hydric stress induction. For the plants used for the prediction, the scores are 86%, 91% and 90% respectively. This study shows that hyperspectral chlorophyll fluorescence spectroscopy is a fast and non-destructive technology allowing early detection of water stress in eggplant plants.
文摘The buoyancy flux Bo at the air/sea interface is very useful to understand the variability of the stratification of the mixed layer, the oceanic mixing, the phytoplankton dynamics and then the coastal upwelling. The atmospheric reanalysis ERA5 and the oceanic reanalysis ORAP5 data have been used in this study to describe the sea surface Bo and, its influence on the variability of the mixing in the mixed layer and consequently on the coastal upwelling along the northern coast of the Gulf of Guinea. The Bo is negative along the coast and, is characterized by a seasonal variability dominated by the thermal buoyancy flux. This study has also shown that the mixing layer is very shallow along the coast and deeper offshore. The negative value of the Bo increases the stratification of the mixed layer and reduces the mixing. This could explain why the mixed layer is shallow in this region. This work suggests that an increasing trend of the global warming could have dramatic impact in this area by increasing the stratification in the mixed layer and would contribute to reducing the coastal upwelling intensity.
文摘In this work, ten medicinal and nutritional leaves samples of <em>Hibiscus sabdariffa</em> Linn imported from Mali and Burkina Faso in C<span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">ô</span></span></span>te d’Ivoire and sold on the market were collected. The analysis of these plants using High Purity Germanium detector (HPGE) gamma spectrometry showed the activity concentrations of <sup>226</sup>Ra, <sup>232</sup>Th, and <sup>40</sup>K varied respectively in the range of (1.74 - 0.11) × 10<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span></span></span>3</sup> Bq/kg, (6.72 - 0.61) × 10<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span></span></span>4</sup> Bq/kg and (4.65 - 0.54) × 10<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span></span></span>3</sup> Bq/kg1 in the leaves of <em>H. sabdariffa</em>. The Average Annual Committed Effective Dose (AACED) values from leaves this plant varied from 251.492 × 10<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span></span></span>6</sup> to 68.133 × 10<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span></span></span>6</sup> mSv/y. These values found are below 0.30 mSv/y, the world average value for an individual. These results show that there is no radiological risk in consuming “bissap” leaves.
文摘Rice yellow mottle is considered the most destructive disease threatening rice production in Africa. Early detection of this infection in rice is essential to limit its expansion and proliferation. However, there is no research devoted to the spectral detection of rice yellow mottle virus (RYMV) infection, especially in the asymptomatic or early stages. This work proposes the use of hyperspectral fluorescence and reflectance data at leaf level for the detection of this disease in asymptomatic stages. A greenhouse experiment was therefore conducted to collect hyperspectral fluorescence and reflectance data at different stages of infection. These data allowed to calculate nine vegetation indices: one from fluorescence spectra and eight from reflectance spectra. A t-test made it possible to identify, from the second day after infection, four relevant reflectance vegetation indices to discriminate healthy leaves from those infected: these are Photochemical Reflectance Index (PRI), Transformed Chlorophyll Absorption in Reflectance Index (TCARI), Structure Intensive Pigment Index (SIPI) and Simple Ratio Pigment Index (SRPI). The fluorescence index was less sensitive in detecting infection. The four significant vegetation indices for the detection of RYMV were then used to build and evaluate models for discriminating plants according to their health status by the supervised classification of support vector machine (SVM) at different stages of infection. The maximum overall accuracy is 92.5% six days after inoculation (6 DAI). The sixth day after inoculation would be the adequate day to detect RYMV. This plants discrimination was validated by the mean reflectance spectra and by the histograms showing the differences between the average reflectance vegetation indices values of the two types of plants. Our results demonstrate the feasibility of differentiating RYMV-infected samples. They suggest that support vector machine learning models could be developed to diagnose RYMV-infected plants based on vegetation indices derived from spectral profiles at early stages of disease development.
文摘Black carbon is one of the primary aerosols directly emitted from biomass known to have strong absorbing properties. The INDAAF and PASMU observational field campaigns which took place (2018) in Abidjan (urban area) and Lamto (rural area) allow the analysis of Black carbon concentration at different time scales through real-time measurements using an analyzer named Aethalometer AE-33. Results presented here show at Lamto: 1) for the diurnal scale an average of 1.71 ± 0.3 μg⋅m<sup>-3</sup> (0.34 ± 0.09 μg⋅m<sup>-3</sup>) in the dry (wet) season;2) for the monthly scale an average of 1.14 ± 0.84 μg⋅m<sup>-3</sup>;3) on the seasonal scale, an average of 2.2 ± 0.02 μg⋅m<sup>-3</sup> (0.6 ± 0.19 μg⋅m<sup>-3</sup>) in the dry (wet) season. The black carbon variation at Lamto is seasonal with an amplification factor of 85.6. Regarding the urban area of Abidjan, due to sampling issues, our analyses were limited to daily, diurnal and weekly time scales. We observed: a) at a daily scale an average of 5.31.± 2.5 μg⋅m<sup>-3</sup>, b) diurnal scale, an average ranging from 6.87 to 13.92 μg⋅m<sup>-3</sup>. The analysis indicated that emissions from urban areas are more related to social and economic activities, with weekday concentrations (7.24 μg⋅m<sup>-3</sup>) higher than concentrations over the weekend (e.g. Saturday 6.59 μg⋅m<sup>-3</sup> and Sunday 6.00 μg⋅m<sup>-3</sup>). Moreover, BC concentration in Abidjan is quite noticeable compared to that of rural areas (Lamto). The ratio between the maximum values of the two areas is of the order of 5.86. In addition, concentrations in some urban areas are slightly above the daily threshold set by the WHO (10 μg⋅m<sup>-3</sup>). Therefore, the levels of urban BC concentrations are alarming whilst rural BC concentrations remain below daily WHO thresholds and are of the same magnitude as those of West African megacities. This study underlies that BC concentrations at Lamto are mainly related to biomass combustion sources while those from urban areas are related to traffic sources. The latter is permanently active, unlike those in rural Lamto, which is seasonal.
文摘The split characteristics of the tropical Mesoscale Convective System (MCS) of April 9, 2018, in northern Ghana were studied using infrasound data measured by the mobile array (I68CI) which was deployed by C<span style="white-space:nowrap;">?</span>te d’Ivoire National Data Center (NDC) in collaboration with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). These infrasound measurements were made during a measurement campaign from January 1st, 2018 to December 31, 2018, in northeast Cote d’Ivoire, precisely in Comoe National Park. Graphic Progressive Multi-Channel Correlation (GPMCC) method based on a progressive study of the correlation functions was used to analyze and visualize data. The infrasound detection from this MCS shows clearly a division of the MCS structure into 2 distinct subsystems under the effect of internal and external constraints not well known but related to convection;a smaller subsystem in the north, associated with an area of intense rainfall of about 30 mm/hour and located at 9.5<span style="white-space:nowrap;">°</span>N - 2<span style="white-space:nowrap;">°</span>E with an azimuth of 70<span style="white-space:nowrap;">°</span> and, a large subsystem in the south, associated with a zone of high rainfall of about 96 mm/hour and located at 8.8<span style="white-space:nowrap;">°</span>N - 1.4<span style="white-space:nowrap;">°</span>E with an azimuth of 90<span style="white-space:nowrap;">°</span>. These two subsystems were located 200 km and 260 km from the I68CI station with frequencies of 2.3 Hz and 1 Hz respectively. The mesoscale convective systems in this region are moving from East to West and including several storm cells.
文摘Rain flooding during June on the West Africa coastal area is analyzed by using the 95th and 75th percentiles, which represent extreme and intense rainfall events respectively. Thus, the contribution of these events that reaches around 50% shows their impact on the rainfall in June. Atmospheric and oceanic factors influence the rain flooding. Indeed, the extreme events are associated with easterly waves propagating from 20<span style="white-space:nowrap;">°</span>E, while those of intense events are initiated around 5<span style="white-space:nowrap;">°</span>E. The impact of oceanic conditions exhibits the warming of the equatorial rail and the Atlantic cold tongue, the warming of the whole ocean basin and a north-south dipole of SST anomalies. The West African monsoon that reaches Abidjan corresponds to a low-level atmospheric flow, whose upward motion extends in latitude from the ocean to the continent. An increase of disturbance contributes to enhancing these events. This is confirmed by the inflow on to the continent of oceanic moisture coming from the ventilation by evaporation of warm water. In addition, the coupled ocean-atmosphere simulations are one of the best candidates that could help to better explain these dramatic events. This study is useful because of showing solutions that could help in adoption of policies for the risks management related to these events.
文摘The severe drought observed in the Sahel during 1970s, 1980s and 1990s has deeply affected the population as well as the economies and the eco-systems of this climatic area. The GGW Initiative spearheaded by Africa Union in 2007 proposed to combat the land degradation and desertification by planting a wall of trees stretching from Dakar to Djibouti. A reforestation was then conducted in the Senegal’s GGW since 2006 as part as other areas in the Sahel. This paper aims to evaluate the carbon sequestration dynamics in the sites of the Senegal’s GGW over the last three decades. The method consists firstly of analyzing the evolution of land cover and land use dynamics based on ESA-CCI LC satellite data. There is an improvement of the surface areas of tree and shrub savanna of 11.40% (Tessekere), 8.25% (Syer) and 2.70% (Loughere-Thioly). The regreening of the different localities and a positive dynamic observed is explained by the return to normal rainfall and to reforestation actions, agroforestry practices, better management of natural resources undertaken. However, some non-reforested sites showed an opposite trend despite of the normal rainfall. Secondly, the results on land mapping are used as a proxy for the assessment of carbon stocks. The dynamic observed in vegetation cover since the beginning of the reforestation made it possible to sequester 5.8 million tons of carbon representing respectively 2.31% of African GGW. This gain in stored carbon is equivalent to 21.2 million tons of CO<sub>2</sub> captured in the atmosphere. Through this study, it appears that carbon storage becomes significant 8 to 10 years after the start of reforestation. An urbanization without respect for the environmental factors could be a danger for the climate (case of Ballou).
文摘This study assesses the climate impact on the productivity of five sugarcane varieties (R579, SP711406, M2593/92, M1400/86, and SP701006) in the industrial plantations of Ferké 1 sugar complex. It is a contribution to research efforts aimed at increasing the productivity of sugarcane varieties in the sugar fields. Also to support agricultural development and guarantee the income of planters. The sugarcane production data are from 2013 to 2017. Climatological data are measured and calculated continuously daily at the production site. In addition, the CMIP-5 (Coupled Model Intercomparison Project) climate database at 1<sup></sup><sup>º </sup>× 1<sup>º</sup> horizontal resolution was used for the predictability of crop yields of the 5 sugarcane varieties in the near future (2021-2050) and far future (2056-2075) to improve the quality of climate services to producers. The statistical methodological approach by multiple linear regression associated with the significativity test shows important and significant coefficients of determination (R<sup>2</sup> > 0.90) between the yields of sugarcane varieties with certain climatic parameters such as minimum and maximum temperatures, insolation, global solar radiation, and potential evapotranspiration. The impact of rainfall has not been directly evaluated because the linear models do not explicitly show sensitivities to this parameter and the total water requirements for the plot are completely assured by irrigation. The future climate projections analyzed only from extreme thermal parameters (Tmax and Tmin) highlight their strong sensitivities with yields from an idealized model. In this model, we have assumed that the water supply needed by sugarcane is always met by irrigation on different plots. Moreover, linear models do not evolve fast enough in time and changes due to external environmental constraints are not too important at the plot scale. The projected thermic parameters can thus constitute a limiting factor for the producibility of sugarcane varieties either by excess or by default. In addition, the linear models used allowed us to observe the behavior of yields with respect to observed past climatic conditions. However, for future yields, there is no way to know if these regressions have the ability to predict them since they are based on projected weather conditions (i.e. CMIP5 data) marked by uncertainties. Additionally, none of the regression equations have been tested against independent observations.
文摘The Uranium-238 (<sup>238</sup>U), Thorium-232 (<sup>232</sup>Th) families and Potassium-40 (<sup>40</sup>K) are of terrestrial origin and contribute generally to an individual’s external exposure through our presence in this environment. They also contribute to the internal exposure through the ingestion of products and beverages such as water that are close to the earth. The aim of this work is to determine the committed effective dose or Total Indicative Dose (TID) due to gamma radioactivity of the borehole water from the Nord Riviera (NR) well field operated by the Côte d’Ivoire Water Distribution Company (SODECI) for the supply of drinking water to part of the population of Abidjan. In addition, the populations, with their habits, could use these borehole waters directly as drinking water. To this end, water samples from the seven (07) functional boreholes were collected and analyzed on a gamma spectrometry chain, equipped with an HPGe detector in the laboratory of the Radiation Protection Institute (RPI) of the GHANA Atomic Energy Commission (GAEC). The results of the specific activities of <sup>238</sup>U, <sup>232</sup>Th and <sup>40</sup>K obtained were transcribed into TID. As the natural radioactivity of the borehole water is high [1], the TIDs calculated from the activity results of the natural radionuclides<sup>238</sup>U, <sup>232</sup>Th, and <sup>40</sup>K vary for the seven boreholes from 0.150 to 0.166 mSv/yr with an average of 0.161 ± 0.034 mSv/yr. The TID of the control tower, where the borehole water is mixed and treated for household use, is equal to 0.136 ± 0.03 mSv/yr. The TIDs obtained are therefore all slightly greater than the WHO reference dose value of 0.1 mSv/yr. But all remain below the UNSCEAR reference dose of 0.29 mSv/yr.
文摘The Tongon mine, the largest gold mine in C?te d’Ivoire, has been in operation since April 2010. However, to our knowledge to date, no study has been conducted on metallic contamination in suspended particulate matter (PM<sub>10</sub> and PM<sub>2.5</sub>) where there is a lack of information on the carcinogenic and non-carcinogenic risk to human health associated with the exposure of populations in the Tongon area to these pollutants. The general objective of this study is to evaluate the level of contamination of PM<sub>10</sub>;PM<sub>2.5</sub> by heavy metals and their impact on the health of populations exposed to these pollutants in the Tongon gold mine area. The sampling and measurement of suspended particulate matter (PM<sub>10</sub> and PM<sub>2.5</sub>) were done using a MiniVol TAS passive air sampler. Heavy metal concentrations were determined by inductively coupled plasma mass spectroscopy (Nex ION 2000 ICP-MS, USA). The results indicate that the average concentrations of suspended particles (PM<sub>2.5</sub> and PM<sub>10</sub>) obtained are all above the recommended exposure limits. In addition, among the heavy metals contained in the suspended particles, the concentrations of arsenic and nickel are high and all above the standard limit values. The assessment of the health risks related to the inhalation of PM<sub>10</sub> particles reveals that their inhalation over a long period could cause a carcinogenic risk.
文摘In the particular context of climate change in Côte d’Ivoire and the vulnerability of farmers to its effects, one of the major issues is how these changes could impact cocoa yields of cocoa production areas. Thus, the objective of this study is to sustainably increase the resilience of all cocoa farming stakeholders to the impacts of climate change. The study was carried out in the central and southern areas of Côte d’Ivoire with a focus on eleven localities that have many communities of cocoa producers and a humid climate. The rainfall and temperature observation data using come from the CRU, they cover the historical period from 1971 to 2000 at 0.5<sup>o</sup> × 0.5<sup>o</sup> horizontal scale. As for the RCP4.5 and RCP8.5 climate scenarios, they come from the CORDEX database and cover the 2021-2050 period. The methodology is based on the calculation of climatic indices sensitive to cocoa cultivation which are the number of consecutive dry days (CDD), the number of consecutive wet days (CWD), the amount of rain during the rainy season and the maximum temperature above 33℃. The results show that for all the localities studied, indices such as CDD and CWD could experience an increase. In addition, the total amount of rain during the long rainy season (April to June) is calculated on the basis of the threshold of 700 mm representing the minimum annual precipitation during the rainy season necessary for good growth of the cocoa tree. It reveals that for the two scenarios the cumulative rainfall will all be greater than 700 mm. Regarding temperatures, the central and southern areas could have a low number of hot days (temperature greater than or equal to 33℃ which is the tolerable threshold for cocoa cultivation). The eleven localities, therefore, remain favorable areas for cocoa cultivation in terms of climatic conditions based on temperature and rainfall, despite the regional dimension of the effects of climate change and the associated constraints.
文摘The radioactive isotopes of the decay series of uranium-238 (<sup>238</sup>U), thorium-232 (<sup>232</sup>Th) and potassium-40 (<sup>40</sup>K) occur naturally in varying amounts in groundwater. They are the subject of many measures, mainly because of the risk they represent from a public health point of view. The purpose of this study is to measure the radioisotope content of borehole waters from the north riviera (NR) catchment field of the Ivorian drinking water distribution company (SODECI). These measurements will make it possible to assess the absolute levels of radioisotopes in the water from SODECI’s boreholes used directly for drinking or swimming, and possibly the associated risk from a public health point of view. To achieve this, a sampling campaign from the seven functional boreholes and the control or treatment tower took place in July 2018 at the NR well field. The analysis of radionuclides by gamma spectrometry was carried out in the laboratory of the Radiation Protection Institute (RPI) of the Ghana Atomic Energy Commission (GAEC). The naturally occurring radionuclides identified during the borehole water samples analysis are <sup>238</sup>U, <sup>232</sup>Th, and <sup>40</sup>K. The results reveal that the specific activities of uranium vary from 0.45 ± 0.18 Bq/L to 0.55 ± 0.17 Bq/L with an average of 0.49 ± 0.15 Bq/L. Those of thorium vary from 0.66 ± 0.14 Bq/L to 0.78 ± 0.18 Bq/L with an average of 0.72 ± 0.16 Bq/L and potassium of 4.14 ± 0.53 Bq/L at 5.87 ± 0.60 Bq/L with an average of 5.32 ± 0.58 Bq/L.
文摘Two simulations of five years (2003-2007) were conducted with the Regional Climate models RegCM4, one coupled with Land surface models BATS and the other with CLM4.5 over West Africa, where simulated air temperature and precipitation were analyzed. The purpose of this study is to assess the performance of RegCM4 coupled with the new CLM4.5 Land</span><span style="font-family:""> </span><span style="font-family:Verdana;">surface scheme and the standard one named BATS in order to find the best configuration of RegCM4 over West African. This study could improve our understanding of the sensitivity of land surface model in West Africa climate simulation, and provide relevant information to RegCM4 users. The results show fairly realistic restitution of West Africa’s climatology and indicate correlations of 0.60 to 0.82 between the simulated fields (BATS and CLM4.5) for precipitation. The substitution of BATS surface scheme by CLM4.5 in the model configuration, leads mainly to an improvement of precipitation over the Atlantic Ocean, however, the impact is not sufficiently noticeable over the continent. While the CLM4.5 experiment restores the seasonal cycles and spatial distribution, the biases increase for precipitation and temperature. Positive biases already existing with BATS are amplified over some sub-regions. This study concludes that temporal localization (seasonal effect), spatial distribution (grid points) and magnitude of precipitation and temperature (bias) are not simultaneously improved by CLM4.5. The introduction of the new land surface scheme CLM4.5, therefore, leads to a performance of the same order as that of BATS, albeit with a more detailed formulation.
文摘Sand is an important natural material for the construction of houses, work buildings and other public spaces. This work, which is one of the first contributions to the environmental quality of construction materials, concerns the measurement of natural radioactivity in the lagoon sands collected in the district of Abidjan. Nineteen (19) samples of these sands are analyzed by gamma-ray spectrometry equipped with HPGe detector. The mean values obtained for <sup>226</sup>Ra, <sup>232</sup>Th and <sup>40</sup>K are respectively 7.76 ± 1.84 Bq·kg<sup>-1</sup>, 5.21 ± 1.36 Bq·kg<sup>-1</sup>, and 217.31 ± 5.03 Bq·kg<sup>-1</sup>. The estimated average value of radium equivalent (Raeq) is 31.94 Bq·kg-1. The results show that the average values obtained are far lower than the global limits of 35, 30, and 400 Bq·kg<sup>-1</sup> for the concentrations of <sup>226</sup>Ra, <sup>232</sup>Th and <sup>40</sup>K, respectively, and 370 Bq·kg<sup>-1 </sup>for the equivalent radium established by the United Nations Scienti<span style="white-space:nowrap;">fi</span>c Committee on the Effects of Atomic Radiation (UNSCEAR). Therefore, the use of the analyzed lagoon sand samples in the different construction sectors should not cause serious radiological effects on the populations living in the District of Abidjan. Our results provide new data on building materials radioactivity in C<span style="white-space:nowrap;">ô</span>te d’Ivoire and all over the World. They can also be used as a reference for future work.
