Schistosomiasis is a neglected tropical disease (NTD) widespread in sub-Saharan Africa and mostly affects school going children. Côte d’Ivoire is one of the most vulnerable countries to schistosomiasis, and its ...Schistosomiasis is a neglected tropical disease (NTD) widespread in sub-Saharan Africa and mostly affects school going children. Côte d’Ivoire is one of the most vulnerable countries to schistosomiasis, and its prevalence varies by region. This cross-sectional survey was conducted in schools in the Upper Sassandra region to determine the knowledge, attitude, and practices of school children regarding schistosomiasis. In total, 354 students participated in the survey. Our results showed that, compared to the girls, the boys had a higher level of knowledge about schistosomiasis OR = 1.605 and p = 0.05. Regarding the signs, symptoms, and modes of transmission and prevention of schistosomiasis, the participants reported a low level of knowledge p > 0.05 and OR 1. In conclusion, it is important to target health messages in schools to reach the most vulnerable students effectively. This initiative aims to provide children with basic knowledge and skills in the transmission of schistosomiasis.展开更多
The mafic enclaves from Paleoproterozoic domain are considered to be the results of large-scale crust-mantle interaction and magma mixing. In this paper, petrography, mineralogy and geochemistry were jointly used to d...The mafic enclaves from Paleoproterozoic domain are considered to be the results of large-scale crust-mantle interaction and magma mixing. In this paper, petrography, mineralogy and geochemistry were jointly used to determine the origin of the mafic enclaves and their relationship with the host granitoids of the Kan granite-gneiss complex. This study also provides new information on crust-mantle interactions. The mafic enclaves of the Kan vary in shape and size and have intermediate chemical compositions. The diagrams used show a number of similarities in the major elements (and often in the trace elements) between the mafic enclaves and the host granitoids. Geochemical show that the Kan rock are metaluminous, enriched in silica, medium to high-K calc-alkaline I-type granite. The similarities reflect a mixing of basic and acid magma. Mafic enclaves have a typical magmatic structure, which is characterized by magma mixing. The genesis of these rocks is associated with the context of subduction. They result from the mixing of a mafic magma originating from the mantle and linked to subduction, and a granitic magma (type I granite) that arises from the partial melting of the crust.展开更多
This study assesses the chemical quality of water resources in the Lower Senegal River valley, based on 35 samples collected in November 2022. Major ion concentrations in surface water and groundwater were analyzed us...This study assesses the chemical quality of water resources in the Lower Senegal River valley, based on 35 samples collected in November 2022. Major ion concentrations in surface water and groundwater were analyzed using classical geochemical interpretation diagrams (Piper, GIBBS, etc.) and multivariate geostatistical analyses, including hierarchical cluster analysis (HCA) and principal component analysis (PCA). The results revealed three types of facies: Ca-Mg-HCO3-type facies, characteristic of poorly mineralized waters such as surface waters and groundwater from dune formations and the alluvial plain close to the hydraulic axis;Na-Cl type facies associated with well waters located in the alluvial plain that tap Inchirian or Nouakchottian shallow reservoirs and Maastrichtian deep borehole waters;and mixed Ca-Cl and Na-HCO3 type facies observed in certain floodplain and dune reservoirs. The results showed a strong correlation between sodium, chlorides, bromides, and electrical conductivity, indicating a significant contribution of these ions to groundwater mineralization. The various sources of water mineralization include mixing processes between surface water or rainwater, or calcite or dolomite dissolution processes (for weakly mineralized waters), basic exchanges or inverse basic exchanges between the aquifer and the water table (for moderately mineralized waters), and evaporation processes, halite dissolution, and paleosalinity during periods of marine transgression and regression (for highly mineralized waters). The study also highlighted the high vulnerability of the alluvial aquifer to pollution from intensive irrigated agriculture, as significant quantities of sulfates and nitrates were measured in some samples. These results also highlight the importance of water quality management in the Lower Senegal Valley, particularly as concerns the protection of the alluvial aquifer against pollution from irrigated agriculture.展开更多
Precision agriculture(PA)is an agricultural management strategy based on observation,measurement and response to the variability of inter/intra-champ cultures.It includes advances in terms of data collection,analysis ...Precision agriculture(PA)is an agricultural management strategy based on observation,measurement and response to the variability of inter/intra-champ cultures.It includes advances in terms of data collection,analysis and management,as well as technological developments in terms of data storage and recovery,precise positioning,yield monitoring and remote sensing.The latter offers an unprecedented spatial,spectral and temporal resolution,but can also provide detailed information on the height of the vegetation and various observations.Today,the success of new agricultural technologies means that many agricultural tasks have become automated and that scientists have conducted more studies and research based on smart algorithms that automatically learn the decision rules from data.The use of Deep Learning(DL)and in particular the development and application of some of its algorithms called Convolutional Neural Networks(CNNs)are considered to be a particular success.In this work,we have applied and tested the performance of a network of convolutional neural network to automatically detect and map olive trees from Phantom4 drone imagery.The workflow involved the acquisition of images and the generation of ortho-mosaic with Pix4D software,as well as the use of a geographic information system.The results obtained with a training dataset of 4500 images of 24∗24 pixels are very satisfying:95%Precision,a 99%Recall and an F-score of 97%.展开更多
The application of organic amendments on soils poor in organic matter(OM) can improve long-term soil fertility, but may also enhance the mineralization of native soil organic matter. Three organic amendments, compost,...The application of organic amendments on soils poor in organic matter(OM) can improve long-term soil fertility, but may also enhance the mineralization of native soil organic matter. Three organic amendments, compost, sewage sludge and horse manure, used by urban market gardeners in Dakar, Senegal were analyzed for their OM maturity. Their fate was evaluated in a 45-d agronomic trial in a sandy Arenosol with lettuce. In each case, water-extractable organic matter(WEOM) and humic-like substances(HLS)were isolated from raw amendments and amended soils, and characterized using ultraviolet-visible(UV/Vis) spectroscopy. Results highlighted the general more aromatic character of HLS and WEOM fractions extracted from compost compared to the other two amendments. When applied to soils, however, these differences were not clearly observed. The aromaticity and humification degree of the labile fraction(WEOM) increased with depth in the first 30 cm for all amendments. This indicated the high lixiviation rates that fresh OM underwent in the studied sandy soil. Finally, a statistical analysis of the results was able to discriminate between surface and deeper horizons and between amended- and non-amended soil samples. Spectroscopic indices showed indeed strong increase/decrease with depth linked with the mineralization/humification processes that the fresh OM from amendments underwent during the 45 d of the agronomic trial. This study highlights the potential of spectroscopic techniques to study agricultural amendment organic matter fractions and their fate in soils.展开更多
The bioremediation of a long-term contaminated soil through biostimulation and surfactant addition was evaluated. The concentrations of 1,1,1-trichloro-2,2-bis（4-chlorophenyl）ethane（DDT） and its metabolites 1,1-di...The bioremediation of a long-term contaminated soil through biostimulation and surfactant addition was evaluated. The concentrations of 1,1,1-trichloro-2,2-bis（4-chlorophenyl）ethane（DDT） and its metabolites 1,1-dichloro-2,2-bis（4-chlorophenyl） ethane（DDD） and1,1-dichloro-2,2-bis（4-chlorophenyl） ethylene（DDE） were monitored during an 8-week remediation process. Physicochemical characterization of the treated soil was performed before and after the bioremediation process. The isolation and identification of predominant microorganisms during the remediation process were also carried out. The efficiency of detoxification was evaluated after each bioremediation protocol. Humidity and p H and the heterotrophic microorganism count were monitored weekly. The DDT concentration was reduced by 79% after 8 weeks via biostimulation with surfactant addition（B ＋ S） and 94.3%via biostimulation alone（B）. Likewise, the concentrations of the metabolites DDE and DDD were reduced to levels below the quantification limits. The microorganisms isolated during bioremediation were identified as Bacillus thuringiensis, Flavobacterium sp., Cuprivadius sp.,Variovorax soli, Phenylobacterium sp. and Lysobacter sp., among others. Analysis with scanning electron microscopy（SEM） allowed visualization of the colonization patterns of soil particles. The toxicity of the soil before and after bioremediation was evaluated using Vibrio fischeri as a bioluminescent sensor. A decrease in the toxic potential of the soil was verified by the increase of the concentration/effect relationship EC50 to 26.9% and 27.2% for B ＋ S and B, respectively, compared to 0.4% obtained for the soil before treatment and 2.5%by natural attenuation after 8 weeks of treatment.展开更多
Field geological work, field engineering monitoring, laboratory experiments and numerical simulation were used to study the development characteristics of pore-fracture system and hydraulic fracture of No.3 coal reser...Field geological work, field engineering monitoring, laboratory experiments and numerical simulation were used to study the development characteristics of pore-fracture system and hydraulic fracture of No.3 coal reservoir in Southern Qinshui Basin. Flow patterns of methane and water in pore-fracture system and hydraulic fracture were discussed by using limit method and average method. Based on the structure model and flow pattern of post-fracturing high-rank coal reservoir, flow patterns of methane and water were established. Results show that seepage pattern of methane in pore-fracture system is linked with pore diameter, fracture width, coal bed pressure and flow velocity. While in hydraulic fracture, it is controlled by fracture height, pressure and flow velocity. Seepage pattern of water in pore-fracture system is linked with pore diameter, fracture width and flow velocity. While in hydraulic fracture, it is controlled by fracture height and flow velocity. Pores and fractures in different sizes are linked up by ultramicroscopic fissures, micro-fissures and hydraulic fracture. In post-fracturing high-rank coal reservoir, methane has level-three flow and gets through triple medium to the wellbore; and water passes mainly through double medium to the wellbore which is level-two flow.展开更多
A modified plastic strain energy as hardening state parameter for dense sand was proposed, based on the results front a series of drained plane strain tests on saturated dense Japanese Toyoura sand with precise stress...A modified plastic strain energy as hardening state parameter for dense sand was proposed, based on the results front a series of drained plane strain tests on saturated dense Japanese Toyoura sand with precise stress and strain measurements along many stress paths. In addition, a unique hardening function between the plastic strain energy and the instantaneous stress path was also presented, which was independent of stress history. The proposed state parameter and hardening function was directly verified by the simple numerical integration method. It is shown that the proposed hardening function is independent of stress history and stress path and is appropriate to be used as the hardening rule in constitutive modeling for dense sand, and it is also capable of simulating the effects on the de-formation characteristics of stress history and stress path for dense sand.展开更多
The identification of burnt forests and their monitoring provide essential information for the suitable management and conservation of these ecosystems. This research focuses on the use of remote sensing with MODIS se...The identification of burnt forests and their monitoring provide essential information for the suitable management and conservation of these ecosystems. This research focuses on the use of remote sensing with MODIS sensor data in a Mediterranean environment, precisely in the Rif region known for its high occurrence of forest fires and the largest burnt areas in Morocco. It mapped the burnt areas during the summer of 2016 using spectral indices from MODIS images, namely the Normalized Burn Ratio (NBR) and the Burnt Area Index for MODIS (BAIM). Two field surveys were used to calibrate spectral indices and validate the maps. First, a monotemporal analysis using a single pre-fire image determined the appropriate threshold of the spectral indices (BAIM and NBR) for burn detecting. Secondly, a multitemporal method was applied based on dBAIM and dNBR images which represented pre-fire and postfire differences of the BAIM and NBR images, respectively. The results show that separate use of monotemporal postfire and multitemporal methods produced an overestimation of the burnt areas. Finally, we propose a new algorithm combining both methods for burnt area mapping that we name Burnt Area Algorithm. MCD45A1 and MCD64A1 MODIS burnt area products were compared to the proposed algorithm. Validation of the estimated burnt areas using reference data of the Moroccan High Commission for Water, Forests and Fight against Desertification showed satisfactory results using the proposed algorithm, with a determination coefficient of 0.68 and a root mean square error of 44.0 ha.展开更多
Strain rate effects on the stress-strain behavior of sand were investigated by performing special plane strain and triaxial compression tests on saturated and air-dried sand specimens. In these tests, the loading stra...Strain rate effects on the stress-strain behavior of sand were investigated by performing special plane strain and triaxial compression tests on saturated and air-dried sand specimens. In these tests, the loading strain rate was changed many times by a factor of up to 1 000 during otherwise monotonous loading at a constant axial strain rate. Test results show that the stress jump upon a stepwise change in the strain rate decays with an increase in the irreversible strain when monotonous loading continues at the changed strain rate and the amount of stress jump is essentially proportional to the instantaneous stress. Based on the amount of these stress jumps, a parameter fl called the rate-sensitivity coefficient is introduced to represent the quantity of the observed viscous properties of sand, which equals 0.021 3 and 0.024 2 respectively for Hostun and Toyoura sands. Further analyses on the results indicate that the effect of the presence of pore water is deemed to be negligible with sand and the fl value is rather independent of loading method, wet condition and confining pressure.展开更多
Recent catastrophic events related to floods in Colombia reveal again the situation of disaster as a development issue not solved in the country. It is necessary to analyze in more detail the areas under threat and th...Recent catastrophic events related to floods in Colombia reveal again the situation of disaster as a development issue not solved in the country. It is necessary to analyze in more detail the areas under threat and their respective vulnerability to the different mechanisms can generate flooding events and make adjustments in the assessment of disaster risks for the appropriate decision-making at local, regional and national levels. This paper presents a research project in its first phase, whose main objective is to develop a methodology for vulnerability assessment from a multiscale, multitemporal and multidisciplinary perspectives, combining the use of indicators and a spatial information system to analyze exposure and vulnerability at regional and local level in specific areas. This methodological tool will also enable local and regional authorities to identify the most appropriate strategies to reduce vulnerability and adaptation options, and make better decisions in assessing disaster risk. The information generated in this study will contribute to public policy action structured to correct short- and medium-term situations of actual or potential vulnerability, which can also be used in other activities of territorial and environmental planning, developing technology transfer activities and training associated with the research project in the service of the authorities and communities. Results obtained of the vulnerability analysis for a Colombian study area will relate to the hazards obtained in a parallel project whose goal is to identify the best risk management strategies through the development of GIS （geographic information system）-based scenarios for different risk and vulnerability reduction options.展开更多
Groundwater in California is very precious, yet what we can withdraw is often contaminated with natural and anthropogenic pollution sources. We have examined the Borrego Valley (BV) groundwater (N = 6 wells) in southe...Groundwater in California is very precious, yet what we can withdraw is often contaminated with natural and anthropogenic pollution sources. We have examined the Borrego Valley (BV) groundwater (N = 6 wells) in southern California to understand the source of arsenic and nitrate in some of its groundwater production wells. The results show that the arsenic values range from <2 ppb to 12.2 ppb and the nitrate values from <1 ppm to 10.2 ppm for different wells respectively. The results showed that the arsenic concentration increased 270% for the well # ID1-10 since 2004 and showed an increase of 63% since 2013 respectively. For other wells the results showed an increase of 147% and 72% since 2001. The nitrate concentration has jumped 42% in concentration since last year in one of the wells. The objective of this study is to understand the nature and source of arsenic and nitrate in BV groundwater aquifer as to how this change in arsenic and nitrate concentration occurs through the time. The arsenic retention in the sediments is highly variable and controlled by local processes as a result of natural weathering process of metamorphic bedrock. The second results from the development of strongly reducing conditions at near-neutral pH values, leading to the desorption of arsenic from mineral oxides and to the reductive dissolution of Fe and Mn oxides, also leading to arsenic release. The high arsenic concentrations in some groundwater wells in Borrego Valley CA require the need for reconnaissance surveys in mineralized areas of fractured crystalline basement. Net groundwater extraction values are based on an irrigation efficiency of 78 percent with 14 to 22 percent irrigation return. We believe that the return flow from irrigational activity could be one of the major sources of nitrate transferring the agricultural contaminants such as nitrate to Borrego Valley aquifer.展开更多
The use of well water by disadvantaged populations in most African cities often presents health risks. The purpose of this study is to determine the physico-chemical and microbiological quality of M’bahiakro well wat...The use of well water by disadvantaged populations in most African cities often presents health risks. The purpose of this study is to determine the physico-chemical and microbiological quality of M’bahiakro well water. A series of physico-chemical, microbiological and piezometric analyses were carried out on the well water in the area. The results of these analyses were processed using Piper and Schoeller-Berkaloff diagrams and the software R 3.1.2 for Principal Component Analysis. Physico-chemical analysis results show that the water has an average temperature of 28°C. They are acidic, with a pH that generally varies from 4 to 6. M’bahiakro well waters are highly mineralized, with an average electrical conductivity of 369.1 μS/cm and 984.1 μS/cm and pass from sodium and potassium chlorinated facies in the dry season (February) to sodium chlorinated facies in the rainy season (October) with K+, Na+ and NO3- ions dominating. These ions would be the result of soil rainfall and the intervention of anthropogenic activities in the pollution of shallow groundwater. Bacteriological results exploitation shows that the well waters studied host high densities of enteritis bacteria (E. coli, Fecal streptococcus, and Clostridium perfringens) during the rainy period (October). M’Bahiakro’s well water is of poor quality and unsuitable for human consumption without prior treatment. However, they deserve particular attention and would require further treatment in rainy periods.展开更多
The study investigates the seasonal and spatial variations in water quality parameters at four different locations along Potou lagoon for seventeen consecutive months. In order to explore spatial variation among diffe...The study investigates the seasonal and spatial variations in water quality parameters at four different locations along Potou lagoon for seventeen consecutive months. In order to explore spatial variation among different stations and seasonal changes, no parametric test of ANOVA was used to compare the mean values of the tested parameters for all the different sampling sites and seasons. Seasonal observations on water quality parameters and chlorophyll-a in Potou coastal lagoon revealed that the coastal water was significantly influenced by freshwater during the long and short rainy seasons. The seasonal significant variation (p a increased during the long dry season, whereas, the concentration of nutrients (nitrite, nitrate, ammonium and soluble reactive phosphorus) increased in the rainy periods. Contrary to the seasonal variation, a spatial homogeneity (horizontal) was registered for all variables, a condition related to the low human occupation in the lagoon watershed. Comparing this study with others conducted in Potou lagoon in 2008, no critical differences that evidence alteration in the water quality were found.展开更多
The Sangzhi-Shimen synclinorium, which is in the western margin region of the Hunan-Hubei Province and as the southeast part of the middle Yangtze platform, is a second-level tectonics unit in the south of this region...The Sangzhi-Shimen synclinorium, which is in the western margin region of the Hunan-Hubei Province and as the southeast part of the middle Yangtze platform, is a second-level tectonics unit in the south of this region. Along the profile, it can be divided into 5 third-level structure belts. By the comprehensive interpretation of seismic data and magnetotelluric (MT) sounding data, it is found that the surface structure is not in accordance with that of the underground, and this un-coordination can be conducted by many decollement surfaces between the layers. There are three periods of deformation in its geo-history in this region: before the early (Yanshan) stage, during the early Yanshan stage and after the early Yanshan stage, while the main deformation period is during the early (Yanshan) stage. And the mechanism of deformation is the thrust faults in basement, which are controlled by many decollements, in addition to the decollement of the cap-rock.展开更多
This study evaluated compaction level of a 15-year old no-till vertisol field crop(40.91%clay,44.16%loam and 14.93%sand)having organic matter contents of 2.23%and 2.91%in 0-10 cm and 10-20 cm profiles,respectively.The...This study evaluated compaction level of a 15-year old no-till vertisol field crop(40.91%clay,44.16%loam and 14.93%sand)having organic matter contents of 2.23%and 2.91%in 0-10 cm and 10-20 cm profiles,respectively.The bulk density ranged from 1.30 g/cm^3 to 1.80 g/cm^3 in the field boundaries,and from 1.01 g/cm^3 to 1.40 g/cm^3 in its center.The field showed a gradient of limestone from 3%to 13%.Measurements were done to evaluate soil strength(cone index)and soil plasticity(Atterberg limits).The soil strength showed different levels of compaction from 4.5 MPa to 16 MPa to distinct five spatial clusters in the field.The soil compactness was related to limestone gradient according the correlation found between the soil strength and limestone levels.The soil plasticity test showed occurrence of plastic limits when the moisture content decreased from 26%to 15%within 5 d interval.The Atterberg limits showed the importance of respecting intervention delays to avoid soil compaction due to its plasticity.A pedotransfer function was developed using soil parameters of texture,organic matter,bulk density,cohesion,internal friction angle and moisture content to compute its precompression stress.Results showed importance of compaction in the field extremities due to importance of machines/tools traffic without avoiding cropping interventions during soil plasticity state.The soil strength(as measured value)was correlated to precompression stress(as estimated values)to show the importance of using pedotransfer function as significant method to evaluate indirectly compactness or susceptibility to compaction of the studied vertisol.展开更多
We investigated the effects of elevated carbon dioxide (CO2) on biogeochemistry of marsh sediment including speciation of selected heavy metals in Salinas de San Pedro mudflat in California. The Salinas de San Pedro m...We investigated the effects of elevated carbon dioxide (CO2) on biogeochemistry of marsh sediment including speciation of selected heavy metals in Salinas de San Pedro mudflat in California. The Salinas de San Pedro mudflat has higher carbon (C) content than the vast majority of fully-vegetated salt marshes even with the higher tidal action in the mudflat. Sources for CO2 were identified as atmospheric CO2 as well as due to local fault degassing process. We measured carbon dioxide, methane, total organic carbon, dissolved oxygen, salinity, and heavy metal concentration in various salt marsh locations. Overall, our results showed that CO2 concentration ranging from 418.7 to 436.9 (ppm), which are slightly different in various chambers but are in good agreement with some heavy metal concentrations values in mudflat at or around the same location. The selected metal concentration values (ppm) ranging from 0.003 - 0.011 (As);0.001 - 0.005 (Cd);0.04 - 0.02 (Cr);0.13 - 0.38 (Cu);0.11 - 0.38 (Pb);0.0009 - 0.020 (Se);and 0.188 - 0.321 (Zn). The low dissolved oxygen (ppm) in the pore water sediment indicated suboxic environment. Additionally, CO2 (ppm) and loss on ignition (LOI) (%) correlated inversely;the higher CO2 content, the lower was the LOI (%);that is to say the excess CO2 causes higher rates of decomposition and therefore it leads to lower LOI (%) on the mudflat surface. It appears that the elevated CO2 makes changes in salt marsh pore water chemistry for instance the free ionic metal (Cu2+, Pb2+, etc.) speciation is one of the most reactive form because simply assimilated by the non-decayed or alive organisms in sediment of salt marsh and/or in water. This means that CO2 not only is a sign of improvement in plant productivity, but also activates microbial decomposition through increases in dissolved organic carbon availability. CO2 also increases acidification processes such as anaerobic degradation of microorganism and oxidation of reduced components. The heavy metal concentrations in sediment samples were slightly higher in suboxic layer, yet it appears that salt marsh sediments in Salinas de San Pedro act like a sink for nutrient and carbon by maximizing carbon sequestration.展开更多
Groundwater comprises a large portion of irrigation for California＇s agriculture, and sustains a wide diversity of ecosystems as well as consumptive use, but pumping is occurring faster than replenishment. At the sam...Groundwater comprises a large portion of irrigation for California＇s agriculture, and sustains a wide diversity of ecosystems as well as consumptive use, but pumping is occurring faster than replenishment. At the same time, contaminants from fertilizers and pesticides are infiltrating into the groundwater, becoming increasingly concentrated as water is extracted. It compared space-based observations of groundwater anomalies from California＇s San Joaquin Valley using the GRACE （gravity recovery and climate experiment） against measurements of 42 organic and inorganic chemicals from 41,667 wells in the valley from 2003 to 2010. It compared Arsenic, Boron, Cadmium, Chloride, Selenium, Trichloroethylene, and TDS （total dissolved solid） concentrations with the groundwater storage anomaly from 2003 to 2010. The results show strong correlations for groundwater depletion against increasing chloride （r2= 0.78, p 〈 0.05） and boron （r2 = 0.88, p 〈 0.05）. This indicates increasing contaminant concentrations while groundwater was depleting over the last eight years. Solubilization by complexation with Cl, CO3 and/or organic chelates may account for the increasing concentration of some heavy metals when groundwater depletion occurs. These results are the first to link space-based groundwater mass change with groundwater contaminant concentration change.展开更多
The objective of this study was to evaluate the typology of water through physicochemical and bacteriological characterization with the aim of highlighting its vulnerability as a drinking water resource. The methodolo...The objective of this study was to evaluate the typology of water through physicochemical and bacteriological characterization with the aim of highlighting its vulnerability as a drinking water resource. The methodology adopted was to evaluate the level of pollution by monitoring the spatiotemporal variation of the water pollution indicator levels of Lake Dohou. The sampling frequency is monthly for one year, from November 2017 to October 2018, in order to obtain a fairly representative image of water quality and its seasonal evolution in eight (8) well-defined stations. The parameters were determined using the standard methods defined by the French Association for Standardization (AFNOR). This study shows that the waters are acidic, with an average pH of 5.81 and a low electrical conductivity of between 42.67 ± 4.30 and 59.62 ± 21.84 μS.cm-1. At all stations, seasonal mean water transparencies are low (<1 m). It is also noted that 99.7% of the water samples collected had total nitrogen (TN) levels above the limit of 4 mg.L-1. All of the lake’s waters have non-compliant BOD5 (2.L-1) for raw water intended for the production of drinking water. Sites D6 and D7 have COD/BOD5 ratio greater than 3, which indicates the presence of non-biodegradable organic matter in these areas. Total coliforms, Escherichia coli and Enterococci were present in 100% (28/28) water samples at concentrations ranging from 2300 to 173,000 CFU/100 mL, from 100 to 1650 CFU/100 mL and from 20 to 1140 CFU 1/100 mL respectively. For Salmonella pathogens, they were detected in 50% of the dry season samples and in 100% of the rainy season samples. This almost permanent presence of this pathogenic germ denotes a poor quality of water with reference to this parameter. The presence of total coliform and other microbial contaminants suggests that supplied water is highly contaminated with pathogens and great reservoirs for them. Principal component analysis (PCA) of the physicochemical data set allowed defining three different classes of water on the Dohou Lake. Outside the upstream zone (D6 and D8), water could continue to be used for the production of drinking water.展开更多
The objective of this study is to assess the level of metal contamination of sediments and agricultural soils in the Ity-Floleu zone. The concentrations of trace elements (Fe, Mn, As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) we...The objective of this study is to assess the level of metal contamination of sediments and agricultural soils in the Ity-Floleu zone. The concentrations of trace elements (Fe, Mn, As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) were measured in different seasons over two successive years. The sediment pollution index made it possible to note that the sediments and agricultural soils of the various stations studied are highly polluted in all seasons. The calculation of the geoaccumulation index indicates that surface water sediments most often experience extreme or moderate pollution in As, Cd, Cu, Hg and Zn in the dry or rainy season except in Pb in some cases. We observed that the sediments of the Cavally river present a serious pollution due to extreme anthropic activities carried out along the river. Over the entire region, the results of the potential ecological risk index (RI) indicate that all the sediments and agricultural soils analysed present a moderate ecological risk in terms of Pb and Zn in certain cases and an ecological risk is observed low bound to other metals in all seasons. This metallic pollution generated by human activities in this region can have consequences for the environment and biodiversity.展开更多
文摘Schistosomiasis is a neglected tropical disease (NTD) widespread in sub-Saharan Africa and mostly affects school going children. Côte d’Ivoire is one of the most vulnerable countries to schistosomiasis, and its prevalence varies by region. This cross-sectional survey was conducted in schools in the Upper Sassandra region to determine the knowledge, attitude, and practices of school children regarding schistosomiasis. In total, 354 students participated in the survey. Our results showed that, compared to the girls, the boys had a higher level of knowledge about schistosomiasis OR = 1.605 and p = 0.05. Regarding the signs, symptoms, and modes of transmission and prevention of schistosomiasis, the participants reported a low level of knowledge p > 0.05 and OR 1. In conclusion, it is important to target health messages in schools to reach the most vulnerable students effectively. This initiative aims to provide children with basic knowledge and skills in the transmission of schistosomiasis.
文摘The mafic enclaves from Paleoproterozoic domain are considered to be the results of large-scale crust-mantle interaction and magma mixing. In this paper, petrography, mineralogy and geochemistry were jointly used to determine the origin of the mafic enclaves and their relationship with the host granitoids of the Kan granite-gneiss complex. This study also provides new information on crust-mantle interactions. The mafic enclaves of the Kan vary in shape and size and have intermediate chemical compositions. The diagrams used show a number of similarities in the major elements (and often in the trace elements) between the mafic enclaves and the host granitoids. Geochemical show that the Kan rock are metaluminous, enriched in silica, medium to high-K calc-alkaline I-type granite. The similarities reflect a mixing of basic and acid magma. Mafic enclaves have a typical magmatic structure, which is characterized by magma mixing. The genesis of these rocks is associated with the context of subduction. They result from the mixing of a mafic magma originating from the mantle and linked to subduction, and a granitic magma (type I granite) that arises from the partial melting of the crust.
文摘This study assesses the chemical quality of water resources in the Lower Senegal River valley, based on 35 samples collected in November 2022. Major ion concentrations in surface water and groundwater were analyzed using classical geochemical interpretation diagrams (Piper, GIBBS, etc.) and multivariate geostatistical analyses, including hierarchical cluster analysis (HCA) and principal component analysis (PCA). The results revealed three types of facies: Ca-Mg-HCO3-type facies, characteristic of poorly mineralized waters such as surface waters and groundwater from dune formations and the alluvial plain close to the hydraulic axis;Na-Cl type facies associated with well waters located in the alluvial plain that tap Inchirian or Nouakchottian shallow reservoirs and Maastrichtian deep borehole waters;and mixed Ca-Cl and Na-HCO3 type facies observed in certain floodplain and dune reservoirs. The results showed a strong correlation between sodium, chlorides, bromides, and electrical conductivity, indicating a significant contribution of these ions to groundwater mineralization. The various sources of water mineralization include mixing processes between surface water or rainwater, or calcite or dolomite dissolution processes (for weakly mineralized waters), basic exchanges or inverse basic exchanges between the aquifer and the water table (for moderately mineralized waters), and evaporation processes, halite dissolution, and paleosalinity during periods of marine transgression and regression (for highly mineralized waters). The study also highlighted the high vulnerability of the alluvial aquifer to pollution from intensive irrigated agriculture, as significant quantities of sulfates and nitrates were measured in some samples. These results also highlight the importance of water quality management in the Lower Senegal Valley, particularly as concerns the protection of the alluvial aquifer against pollution from irrigated agriculture.
文摘Precision agriculture(PA)is an agricultural management strategy based on observation,measurement and response to the variability of inter/intra-champ cultures.It includes advances in terms of data collection,analysis and management,as well as technological developments in terms of data storage and recovery,precise positioning,yield monitoring and remote sensing.The latter offers an unprecedented spatial,spectral and temporal resolution,but can also provide detailed information on the height of the vegetation and various observations.Today,the success of new agricultural technologies means that many agricultural tasks have become automated and that scientists have conducted more studies and research based on smart algorithms that automatically learn the decision rules from data.The use of Deep Learning(DL)and in particular the development and application of some of its algorithms called Convolutional Neural Networks(CNNs)are considered to be a particular success.In this work,we have applied and tested the performance of a network of convolutional neural network to automatically detect and map olive trees from Phantom4 drone imagery.The workflow involved the acquisition of images and the generation of ortho-mosaic with Pix4D software,as well as the use of a geographic information system.The results obtained with a training dataset of 4500 images of 24∗24 pixels are very satisfying:95%Precision,a 99%Recall and an F-score of 97%.
基金supported by the Swiss National Science Foundation (No. 207021-109689/1)
文摘The application of organic amendments on soils poor in organic matter(OM) can improve long-term soil fertility, but may also enhance the mineralization of native soil organic matter. Three organic amendments, compost, sewage sludge and horse manure, used by urban market gardeners in Dakar, Senegal were analyzed for their OM maturity. Their fate was evaluated in a 45-d agronomic trial in a sandy Arenosol with lettuce. In each case, water-extractable organic matter(WEOM) and humic-like substances(HLS)were isolated from raw amendments and amended soils, and characterized using ultraviolet-visible(UV/Vis) spectroscopy. Results highlighted the general more aromatic character of HLS and WEOM fractions extracted from compost compared to the other two amendments. When applied to soils, however, these differences were not clearly observed. The aromaticity and humification degree of the labile fraction(WEOM) increased with depth in the first 30 cm for all amendments. This indicated the high lixiviation rates that fresh OM underwent in the studied sandy soil. Finally, a statistical analysis of the results was able to discriminate between surface and deeper horizons and between amended- and non-amended soil samples. Spectroscopic indices showed indeed strong increase/decrease with depth linked with the mineralization/humification processes that the fresh OM from amendments underwent during the 45 d of the agronomic trial. This study highlights the potential of spectroscopic techniques to study agricultural amendment organic matter fractions and their fate in soils.
基金the GDCON group and the 2013–2014 sustainability grant of the Pro-Vice Chancellor for Research of the University of Antioquia for funding the project
文摘The bioremediation of a long-term contaminated soil through biostimulation and surfactant addition was evaluated. The concentrations of 1,1,1-trichloro-2,2-bis（4-chlorophenyl）ethane（DDT） and its metabolites 1,1-dichloro-2,2-bis（4-chlorophenyl） ethane（DDD） and1,1-dichloro-2,2-bis（4-chlorophenyl） ethylene（DDE） were monitored during an 8-week remediation process. Physicochemical characterization of the treated soil was performed before and after the bioremediation process. The isolation and identification of predominant microorganisms during the remediation process were also carried out. The efficiency of detoxification was evaluated after each bioremediation protocol. Humidity and p H and the heterotrophic microorganism count were monitored weekly. The DDT concentration was reduced by 79% after 8 weeks via biostimulation with surfactant addition（B ＋ S） and 94.3%via biostimulation alone（B）. Likewise, the concentrations of the metabolites DDE and DDD were reduced to levels below the quantification limits. The microorganisms isolated during bioremediation were identified as Bacillus thuringiensis, Flavobacterium sp., Cuprivadius sp.,Variovorax soli, Phenylobacterium sp. and Lysobacter sp., among others. Analysis with scanning electron microscopy（SEM） allowed visualization of the colonization patterns of soil particles. The toxicity of the soil before and after bioremediation was evaluated using Vibrio fischeri as a bioluminescent sensor. A decrease in the toxic potential of the soil was verified by the increase of the concentration/effect relationship EC50 to 26.9% and 27.2% for B ＋ S and B, respectively, compared to 0.4% obtained for the soil before treatment and 2.5%by natural attenuation after 8 weeks of treatment.
基金Projects(41330638,41272154)supported by the National Natural Science Foundation of ChinaProject supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD),ChinaProject(2014M551705)supported by the China Postdoctoral Science Foundation
文摘Field geological work, field engineering monitoring, laboratory experiments and numerical simulation were used to study the development characteristics of pore-fracture system and hydraulic fracture of No.3 coal reservoir in Southern Qinshui Basin. Flow patterns of methane and water in pore-fracture system and hydraulic fracture were discussed by using limit method and average method. Based on the structure model and flow pattern of post-fracturing high-rank coal reservoir, flow patterns of methane and water were established. Results show that seepage pattern of methane in pore-fracture system is linked with pore diameter, fracture width, coal bed pressure and flow velocity. While in hydraulic fracture, it is controlled by fracture height, pressure and flow velocity. Seepage pattern of water in pore-fracture system is linked with pore diameter, fracture width and flow velocity. While in hydraulic fracture, it is controlled by fracture height and flow velocity. Pores and fractures in different sizes are linked up by ultramicroscopic fissures, micro-fissures and hydraulic fracture. In post-fracturing high-rank coal reservoir, methane has level-three flow and gets through triple medium to the wellbore; and water passes mainly through double medium to the wellbore which is level-two flow.
文摘A modified plastic strain energy as hardening state parameter for dense sand was proposed, based on the results front a series of drained plane strain tests on saturated dense Japanese Toyoura sand with precise stress and strain measurements along many stress paths. In addition, a unique hardening function between the plastic strain energy and the instantaneous stress path was also presented, which was independent of stress history. The proposed state parameter and hardening function was directly verified by the simple numerical integration method. It is shown that the proposed hardening function is independent of stress history and stress path and is appropriate to be used as the hardening rule in constitutive modeling for dense sand, and it is also capable of simulating the effects on the de-formation characteristics of stress history and stress path for dense sand.
基金the Faculty of Science and Technology of Beni Mellal for their logistical and financial support for the PhD project No. RNES44/13
文摘The identification of burnt forests and their monitoring provide essential information for the suitable management and conservation of these ecosystems. This research focuses on the use of remote sensing with MODIS sensor data in a Mediterranean environment, precisely in the Rif region known for its high occurrence of forest fires and the largest burnt areas in Morocco. It mapped the burnt areas during the summer of 2016 using spectral indices from MODIS images, namely the Normalized Burn Ratio (NBR) and the Burnt Area Index for MODIS (BAIM). Two field surveys were used to calibrate spectral indices and validate the maps. First, a monotemporal analysis using a single pre-fire image determined the appropriate threshold of the spectral indices (BAIM and NBR) for burn detecting. Secondly, a multitemporal method was applied based on dBAIM and dNBR images which represented pre-fire and postfire differences of the BAIM and NBR images, respectively. The results show that separate use of monotemporal postfire and multitemporal methods produced an overestimation of the burnt areas. Finally, we propose a new algorithm combining both methods for burnt area mapping that we name Burnt Area Algorithm. MCD45A1 and MCD64A1 MODIS burnt area products were compared to the proposed algorithm. Validation of the estimated burnt areas using reference data of the Moroccan High Commission for Water, Forests and Fight against Desertification showed satisfactory results using the proposed algorithm, with a determination coefficient of 0.68 and a root mean square error of 44.0 ha.
基金Project(50679056) supported by the National Natural Science Foundation of ChinaProject(06-0378) supported by Program for NewCentury Excellent Talents in University+1 种基金Project(05SG25) supported by the "Dawn" Program of Shanghai Education Commission, ChinaProject(B308) supported by the Shanghai Leading Academic Discipline, China
文摘Strain rate effects on the stress-strain behavior of sand were investigated by performing special plane strain and triaxial compression tests on saturated and air-dried sand specimens. In these tests, the loading strain rate was changed many times by a factor of up to 1 000 during otherwise monotonous loading at a constant axial strain rate. Test results show that the stress jump upon a stepwise change in the strain rate decays with an increase in the irreversible strain when monotonous loading continues at the changed strain rate and the amount of stress jump is essentially proportional to the instantaneous stress. Based on the amount of these stress jumps, a parameter fl called the rate-sensitivity coefficient is introduced to represent the quantity of the observed viscous properties of sand, which equals 0.021 3 and 0.024 2 respectively for Hostun and Toyoura sands. Further analyses on the results indicate that the effect of the presence of pore water is deemed to be negligible with sand and the fl value is rather independent of loading method, wet condition and confining pressure.
文摘Recent catastrophic events related to floods in Colombia reveal again the situation of disaster as a development issue not solved in the country. It is necessary to analyze in more detail the areas under threat and their respective vulnerability to the different mechanisms can generate flooding events and make adjustments in the assessment of disaster risks for the appropriate decision-making at local, regional and national levels. This paper presents a research project in its first phase, whose main objective is to develop a methodology for vulnerability assessment from a multiscale, multitemporal and multidisciplinary perspectives, combining the use of indicators and a spatial information system to analyze exposure and vulnerability at regional and local level in specific areas. This methodological tool will also enable local and regional authorities to identify the most appropriate strategies to reduce vulnerability and adaptation options, and make better decisions in assessing disaster risk. The information generated in this study will contribute to public policy action structured to correct short- and medium-term situations of actual or potential vulnerability, which can also be used in other activities of territorial and environmental planning, developing technology transfer activities and training associated with the research project in the service of the authorities and communities. Results obtained of the vulnerability analysis for a Colombian study area will relate to the hazards obtained in a parallel project whose goal is to identify the best risk management strategies through the development of GIS （geographic information system）-based scenarios for different risk and vulnerability reduction options.
文摘Groundwater in California is very precious, yet what we can withdraw is often contaminated with natural and anthropogenic pollution sources. We have examined the Borrego Valley (BV) groundwater (N = 6 wells) in southern California to understand the source of arsenic and nitrate in some of its groundwater production wells. The results show that the arsenic values range from <2 ppb to 12.2 ppb and the nitrate values from <1 ppm to 10.2 ppm for different wells respectively. The results showed that the arsenic concentration increased 270% for the well # ID1-10 since 2004 and showed an increase of 63% since 2013 respectively. For other wells the results showed an increase of 147% and 72% since 2001. The nitrate concentration has jumped 42% in concentration since last year in one of the wells. The objective of this study is to understand the nature and source of arsenic and nitrate in BV groundwater aquifer as to how this change in arsenic and nitrate concentration occurs through the time. The arsenic retention in the sediments is highly variable and controlled by local processes as a result of natural weathering process of metamorphic bedrock. The second results from the development of strongly reducing conditions at near-neutral pH values, leading to the desorption of arsenic from mineral oxides and to the reductive dissolution of Fe and Mn oxides, also leading to arsenic release. The high arsenic concentrations in some groundwater wells in Borrego Valley CA require the need for reconnaissance surveys in mineralized areas of fractured crystalline basement. Net groundwater extraction values are based on an irrigation efficiency of 78 percent with 14 to 22 percent irrigation return. We believe that the return flow from irrigational activity could be one of the major sources of nitrate transferring the agricultural contaminants such as nitrate to Borrego Valley aquifer.
文摘The use of well water by disadvantaged populations in most African cities often presents health risks. The purpose of this study is to determine the physico-chemical and microbiological quality of M’bahiakro well water. A series of physico-chemical, microbiological and piezometric analyses were carried out on the well water in the area. The results of these analyses were processed using Piper and Schoeller-Berkaloff diagrams and the software R 3.1.2 for Principal Component Analysis. Physico-chemical analysis results show that the water has an average temperature of 28°C. They are acidic, with a pH that generally varies from 4 to 6. M’bahiakro well waters are highly mineralized, with an average electrical conductivity of 369.1 μS/cm and 984.1 μS/cm and pass from sodium and potassium chlorinated facies in the dry season (February) to sodium chlorinated facies in the rainy season (October) with K+, Na+ and NO3- ions dominating. These ions would be the result of soil rainfall and the intervention of anthropogenic activities in the pollution of shallow groundwater. Bacteriological results exploitation shows that the well waters studied host high densities of enteritis bacteria (E. coli, Fecal streptococcus, and Clostridium perfringens) during the rainy period (October). M’Bahiakro’s well water is of poor quality and unsuitable for human consumption without prior treatment. However, they deserve particular attention and would require further treatment in rainy periods.
文摘The study investigates the seasonal and spatial variations in water quality parameters at four different locations along Potou lagoon for seventeen consecutive months. In order to explore spatial variation among different stations and seasonal changes, no parametric test of ANOVA was used to compare the mean values of the tested parameters for all the different sampling sites and seasons. Seasonal observations on water quality parameters and chlorophyll-a in Potou coastal lagoon revealed that the coastal water was significantly influenced by freshwater during the long and short rainy seasons. The seasonal significant variation (p a increased during the long dry season, whereas, the concentration of nutrients (nitrite, nitrate, ammonium and soluble reactive phosphorus) increased in the rainy periods. Contrary to the seasonal variation, a spatial homogeneity (horizontal) was registered for all variables, a condition related to the low human occupation in the lagoon watershed. Comparing this study with others conducted in Potou lagoon in 2008, no critical differences that evidence alteration in the water quality were found.
文摘The Sangzhi-Shimen synclinorium, which is in the western margin region of the Hunan-Hubei Province and as the southeast part of the middle Yangtze platform, is a second-level tectonics unit in the south of this region. Along the profile, it can be divided into 5 third-level structure belts. By the comprehensive interpretation of seismic data and magnetotelluric (MT) sounding data, it is found that the surface structure is not in accordance with that of the underground, and this un-coordination can be conducted by many decollement surfaces between the layers. There are three periods of deformation in its geo-history in this region: before the early (Yanshan) stage, during the early Yanshan stage and after the early Yanshan stage, while the main deformation period is during the early (Yanshan) stage. And the mechanism of deformation is the thrust faults in basement, which are controlled by many decollements, in addition to the decollement of the cap-rock.
文摘This study evaluated compaction level of a 15-year old no-till vertisol field crop(40.91%clay,44.16%loam and 14.93%sand)having organic matter contents of 2.23%and 2.91%in 0-10 cm and 10-20 cm profiles,respectively.The bulk density ranged from 1.30 g/cm^3 to 1.80 g/cm^3 in the field boundaries,and from 1.01 g/cm^3 to 1.40 g/cm^3 in its center.The field showed a gradient of limestone from 3%to 13%.Measurements were done to evaluate soil strength(cone index)and soil plasticity(Atterberg limits).The soil strength showed different levels of compaction from 4.5 MPa to 16 MPa to distinct five spatial clusters in the field.The soil compactness was related to limestone gradient according the correlation found between the soil strength and limestone levels.The soil plasticity test showed occurrence of plastic limits when the moisture content decreased from 26%to 15%within 5 d interval.The Atterberg limits showed the importance of respecting intervention delays to avoid soil compaction due to its plasticity.A pedotransfer function was developed using soil parameters of texture,organic matter,bulk density,cohesion,internal friction angle and moisture content to compute its precompression stress.Results showed importance of compaction in the field extremities due to importance of machines/tools traffic without avoiding cropping interventions during soil plasticity state.The soil strength(as measured value)was correlated to precompression stress(as estimated values)to show the importance of using pedotransfer function as significant method to evaluate indirectly compactness or susceptibility to compaction of the studied vertisol.
文摘We investigated the effects of elevated carbon dioxide (CO2) on biogeochemistry of marsh sediment including speciation of selected heavy metals in Salinas de San Pedro mudflat in California. The Salinas de San Pedro mudflat has higher carbon (C) content than the vast majority of fully-vegetated salt marshes even with the higher tidal action in the mudflat. Sources for CO2 were identified as atmospheric CO2 as well as due to local fault degassing process. We measured carbon dioxide, methane, total organic carbon, dissolved oxygen, salinity, and heavy metal concentration in various salt marsh locations. Overall, our results showed that CO2 concentration ranging from 418.7 to 436.9 (ppm), which are slightly different in various chambers but are in good agreement with some heavy metal concentrations values in mudflat at or around the same location. The selected metal concentration values (ppm) ranging from 0.003 - 0.011 (As);0.001 - 0.005 (Cd);0.04 - 0.02 (Cr);0.13 - 0.38 (Cu);0.11 - 0.38 (Pb);0.0009 - 0.020 (Se);and 0.188 - 0.321 (Zn). The low dissolved oxygen (ppm) in the pore water sediment indicated suboxic environment. Additionally, CO2 (ppm) and loss on ignition (LOI) (%) correlated inversely;the higher CO2 content, the lower was the LOI (%);that is to say the excess CO2 causes higher rates of decomposition and therefore it leads to lower LOI (%) on the mudflat surface. It appears that the elevated CO2 makes changes in salt marsh pore water chemistry for instance the free ionic metal (Cu2+, Pb2+, etc.) speciation is one of the most reactive form because simply assimilated by the non-decayed or alive organisms in sediment of salt marsh and/or in water. This means that CO2 not only is a sign of improvement in plant productivity, but also activates microbial decomposition through increases in dissolved organic carbon availability. CO2 also increases acidification processes such as anaerobic degradation of microorganism and oxidation of reduced components. The heavy metal concentrations in sediment samples were slightly higher in suboxic layer, yet it appears that salt marsh sediments in Salinas de San Pedro act like a sink for nutrient and carbon by maximizing carbon sequestration.
文摘Groundwater comprises a large portion of irrigation for California＇s agriculture, and sustains a wide diversity of ecosystems as well as consumptive use, but pumping is occurring faster than replenishment. At the same time, contaminants from fertilizers and pesticides are infiltrating into the groundwater, becoming increasingly concentrated as water is extracted. It compared space-based observations of groundwater anomalies from California＇s San Joaquin Valley using the GRACE （gravity recovery and climate experiment） against measurements of 42 organic and inorganic chemicals from 41,667 wells in the valley from 2003 to 2010. It compared Arsenic, Boron, Cadmium, Chloride, Selenium, Trichloroethylene, and TDS （total dissolved solid） concentrations with the groundwater storage anomaly from 2003 to 2010. The results show strong correlations for groundwater depletion against increasing chloride （r2= 0.78, p 〈 0.05） and boron （r2 = 0.88, p 〈 0.05）. This indicates increasing contaminant concentrations while groundwater was depleting over the last eight years. Solubilization by complexation with Cl, CO3 and/or organic chelates may account for the increasing concentration of some heavy metals when groundwater depletion occurs. These results are the first to link space-based groundwater mass change with groundwater contaminant concentration change.
文摘The objective of this study was to evaluate the typology of water through physicochemical and bacteriological characterization with the aim of highlighting its vulnerability as a drinking water resource. The methodology adopted was to evaluate the level of pollution by monitoring the spatiotemporal variation of the water pollution indicator levels of Lake Dohou. The sampling frequency is monthly for one year, from November 2017 to October 2018, in order to obtain a fairly representative image of water quality and its seasonal evolution in eight (8) well-defined stations. The parameters were determined using the standard methods defined by the French Association for Standardization (AFNOR). This study shows that the waters are acidic, with an average pH of 5.81 and a low electrical conductivity of between 42.67 ± 4.30 and 59.62 ± 21.84 μS.cm-1. At all stations, seasonal mean water transparencies are low (<1 m). It is also noted that 99.7% of the water samples collected had total nitrogen (TN) levels above the limit of 4 mg.L-1. All of the lake’s waters have non-compliant BOD5 (2.L-1) for raw water intended for the production of drinking water. Sites D6 and D7 have COD/BOD5 ratio greater than 3, which indicates the presence of non-biodegradable organic matter in these areas. Total coliforms, Escherichia coli and Enterococci were present in 100% (28/28) water samples at concentrations ranging from 2300 to 173,000 CFU/100 mL, from 100 to 1650 CFU/100 mL and from 20 to 1140 CFU 1/100 mL respectively. For Salmonella pathogens, they were detected in 50% of the dry season samples and in 100% of the rainy season samples. This almost permanent presence of this pathogenic germ denotes a poor quality of water with reference to this parameter. The presence of total coliform and other microbial contaminants suggests that supplied water is highly contaminated with pathogens and great reservoirs for them. Principal component analysis (PCA) of the physicochemical data set allowed defining three different classes of water on the Dohou Lake. Outside the upstream zone (D6 and D8), water could continue to be used for the production of drinking water.
文摘The objective of this study is to assess the level of metal contamination of sediments and agricultural soils in the Ity-Floleu zone. The concentrations of trace elements (Fe, Mn, As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) were measured in different seasons over two successive years. The sediment pollution index made it possible to note that the sediments and agricultural soils of the various stations studied are highly polluted in all seasons. The calculation of the geoaccumulation index indicates that surface water sediments most often experience extreme or moderate pollution in As, Cd, Cu, Hg and Zn in the dry or rainy season except in Pb in some cases. We observed that the sediments of the Cavally river present a serious pollution due to extreme anthropic activities carried out along the river. Over the entire region, the results of the potential ecological risk index (RI) indicate that all the sediments and agricultural soils analysed present a moderate ecological risk in terms of Pb and Zn in certain cases and an ecological risk is observed low bound to other metals in all seasons. This metallic pollution generated by human activities in this region can have consequences for the environment and biodiversity.
