Impact of the urban development of the Mingoa River watershed on the Municipal Lake of Yaoundé, Cameroon

10 p.International audienceCurrently, Africa is the less urbanized region in the world. But that trend will change by 2020. Their urban development and globalization have promoted developed countries lifestyle, despite poverty. That means the use of chemicals. Sanitation issues have led to the discharge of untreated wastewater, and as a result, to the emission of persistent pollutants, harmful for human health and for the aquatic environment. Chemicals leading role in economy and in the improvement of life quality has to be weight against their potential negative impacts. The risk represented by these impacts makes chemicals management, an issue of sustainable development. According to a UNEP report, that topic is little documented in Africa. Our work aims at reconstructing an historical link between the urban development of the Mingoa River watershed and the Municipal Lake organic pollution. Thus, we are going to examine the sedimentary compartment using pollutants as tracers. Given that we have not started yet the laboratory work, this article is an introduction to the study

Apport de la géologie, de l’hydrogéologie et des isotopes de l’environnement à la connaissance des «nappes en creux» du Grand Yaéré (Nord Cameroun)

La carte piézométrique de la nappe du Logone-Chari-Tchad met en évidence des anomalies piézométriques interprétées comme des « nappes en creux ». Les informations de l’hydrogéologie et des isotopes de l’environnement conduisent à remettre en question les grandes profondeurs des niveaux statiques observées par certains auteurs dans ces dépressions piézométriques. Les données hydrogéologiques démontrent que dans la zone déprimée de la surface piézométrique, l’aquifère est de type bicouche. Par ailleurs, la distribution des teneurs en isotopes stables (oxygène-18 et deutérium) et en tritium confirme le cloisonnement des aquifères :La relation δ 2H vs. δ 18O montre que les effets d’enrichissement par évaporation lors de la recharge des nappes ne sont très marqués que dans les eaux des nappes superficielles dont les niveaux statiques ne dépassent pas 20 m de profondeur. Les dépressions fermées dont les points les plus bas atteignent 60 m sous la surface du sol s’interprètent difficilement dans l’hypothèse d’une reprise évaporatoire.Il résulte de cette étude que l’absence de dépendance nette entre les niveaux piézométriques superficiels et les niveaux profonds place le problème des anomalies piézométriques du Grand Yaéré dans un contexte totalement différent de celui des anciennes interprétations qui s’appuyaient sur l’hypothèse d’une nappe libre généralisée monocouche. À l’avenir, la construction de la carte piézométrique de la nappe du Logone-Chari-Tchad devra tenir compte de la structure des deux nappes superposées.Piezometric depressions, common in sub-Saharan Africa, are major hydrogeological anomalies manifested by closed curves, pronounced hollows and dips attaining several tens of meters below the regional water table level. The Logone-Chari-Chad piezometric map reveals piezometric anomalies that have been interpreted as depressed aquifers. The depth of the water table is 60 m in the Tagawa-Am Talia axis, 40 m between Louba-Louba and Andirni and 30 m around Yagoua. Factors linked to evaporation are generally thought to be responsible for these depressed zones.The objective of this study (based on the saturated zone) was: 1) to place the Logone-Chari-Chad piezometric anomalies in their hydrogeological settings, and 2) to evaluate the use of environmental isotopes to explain their formation processes. To achieve our goal, 27 water supply points (8 boreholes and 19 wells) were selected from the borders and centre of the Logone-Chari-Chad depression. Samples were collected between 1989 and 1991. Measurements performed in the field involved static water levels, whereas the laboratory analyses 18O, 2H and 3H were performed at the International Atomic Energy Agency (IAEA) laboratory in Vienna, within the framework of the project RAF/8/012 funded by IAEA.The new geological and hydrogeological data demonstrate that in the depressed zone of the piezometric surface, the aquifer has two layers. In contrast, the Logone-Chari-Chad piezometric map was previously drawn considering the aquifer as a single-layer. From a hydrochemical point of view, the groundwater in the Logone-Chari-Chad aquifer is stratified: calcium bicarbonate type water was found at the surface (shallow groundwater), whereas sodium carbonate type water was found at depth (deeper groundwater).Seasonal piezometric fluctuations of 1.5 to 3 m have been observed in the shallow groundwater. In the deeper groundwater, they range from 0.20 to 0.30 m. The difference in the values of water table fluctuation leads not only to variations in the mode of groundwater circulation, but also to variations in the hydrodynamic properties of aquifers, such as transmissivity.The distribution in stable isotope contents (18O, 2H and 3H) confirmed the compartmentalization of aquifers. The correlation between 3H and 18O showed that there are two water types, with different recharge modes and episodes. On the border of the depression, shallow groundwater pinches out on the semi-permeable substratum, resulting in a tritium content greater than 4 UT. In the depression axis, there is deeper groundwater with a tritium content below 4 UT.The relationship between 2H and 18O shows that the enrichment effects of evaporation at the time of recharge are very pronounced only in the shallow groundwater, where the static level does not exceed 20 m below the soil surface. The closed piezometric depressions, whose deepest point attains 60 m below the soil surface, cannot be explained by the presence of intense evaporation. The variation in tritium content with respect to the static level shows that in the depressed zone, the first 20 m are characterized by a tritium content greater than 4 UT, whereas at depths of 30 m or more, tritium contents are lower than 4 UT.The absence of dependence between shallow and deep piezometric levels invalidates the interpretation of great water depths proposed in previous studies of the piezometric depression of the Logone-Chari-Chad water table. Thus, the hypothesis that the Logone-Chari-Chad is a single-layer system should be abandoned. The future construction of the piezometric map of the Logone-Chari-Chad water table should take into account the structure and lithology of the two superimposed layers

Apport de la géologie, de l'hydrogéologie et des isotopes de l'environnement à la connaissance des “nappes en creux” du Grand Yaéré (Nord Cameroun)

International audiencePiezometric depressions, common in sub-Saharan Africa, are major hydrogeological anomalies manifested by closed curves, pronounced hollows and dips attaining several tens of meters below the regional water table level. The Logone- Chari-Chad piezometric map reveals piezometric anomalies that have been interpreted as depressed aquifers. The depth of the water table is 60 m in the Tagawa-Am Talia axis, 40 m between Louba-Louba and Andirni and 30 m around Yagoua. Factors linked to evaporation are generally thought to be responsible for these depressed zones. The objective of this study (based on the saturated zone) was: 1) to place the Logone-Chari-Chad piezometric anomalies in their hydrogeological settings, and 2) to evaluate the use of environmental isotopes to explain their formation processes. To achieve our goal, 27 water supply points (8 boreholes and 19 wells) were selected from the borders and centre of the Logone-Chari-Chad depression. Samples were collected between 1989 and 1991. Measurements performed in the field involved static water levels, whereas the laboratory analyses 18O, ²H and 3H were performed at the International Atomic Energy Agency (IAEA) laboratory in Vienna, within the framework of the project RAF/8/012 funded by IAEA. The new geological and hydrogeological data demonstrate that in the depressed zone of the piezometric surface, the aquifer has two layers. In contrast, the Logone-Chari-Chad piezometric map was previously drawn considering the aquifer as a single-layer. From a hydrochemical point of view, the groundwater in the Logone-Chari-Chad aquifer is stratified: calcium bicarbonate type water was found at the surface (shallow groundwater), whereas sodium carbonate type water was found at depth (deeper groundwater). Seasonal piezometric fluctuations of 1.5 to 3 m have been observed in the shallow groundwater. In the deeper groundwater, they range from 0.20 to 0.30 m. The difference in the values of water table fluctuation leads not only to variations in the mode of groundwater circulation, but also to variations in the hydrodynamic properties of aquifers, such as transmissivity. The distribution in stable isotope contents (18O, ²H and 3H) confirmed the compartmentalization of aquifers. The correlation between 3H and 18O showed that there are two water types, with different recharge modes and episodes. On the border of the depression, shallow groundwater pinches out on the semi-permeable substratum, resulting in a tritium content greater than 4 UT. In the depression axis, there is deeper groundwater with a tritium content below 4 UT. The relationship between ²H and 18O shows that the enrichment effects of evaporation at the time of recharge are very pronounced only in the shallow groundwater, where the static level does not exceed 20 m below the soil surface. The closed piezometric depressions, whose deepest point attains 60 m below the soil surface, cannot be explained by the presence of intense evaporation. The variation in tritium content with respect to the static level shows that in the depressed zone, the first 20 m are characterized by a tritium content greater than 4 UT, whereas at depths of 30 m or more, tritium contents are lower than 4 UT. The absence of dependence between shallow and deep piezometric levels invalidates the interpretation of great water depths proposed in previous studies of the piezometric depression of the Logone-Chari-Chad water table. Thus, the hypothesis that the Logone-Chari-Chad is a single-layer system should be abandoned. The future construction of the piezometric map of the Logone-Chari-Chad water table should take into account the structure and lithology of the two superimposed layers

Identifying students' misconceptions in writing balanced equations for dissolving ionic compounds in water and using multiple-choice questions at the symbolic and particulate levels to confront these misconceptions /

Adviser: Michael J. Sanger.Students who harbor misconceptions often find chemistry difficult to understand. To improve teaching about the dissolving process, first semester introductory chemistry students were asked to complete a free-response questionnaire on writing balanced equations for dissolving ionic compounds in water. To corroborate errors and misconceptions identified from students' generated balanced equations, another sample of students participated in semi-structured interviews where they were asked to explain their thought processes involved in writing the balanced equations for the dissolving ionic compounds dissolving in water. Misconceptions of the dissolving process were identified and described in detail. The most popular misconception was that water chemically reacts with an ionic compound through double displacement to form a metal oxide and an acid. The second popular misconception was that an ionic compound dissolves as neutral atoms or molecules. The third popular misconception was that students confused subscripts and coefficients.Another sample of introductory chemistry students were assessed on the dissolving process using the three popular misconceptions as three of the four choices in multiple-choice questions at the symbolic- and particulate-level. The symbolic-level questions involved symbolic balanced equations and the particulate-level questions involved dynamic animations or static pictures of the same four choices. Students' responses to these questions were discussed in terms of four variables---Answer (the correct answer and three misconceptions), Representation (symbolic or particulate questions), Visualization (static or animated pictures), and Representation Order (symbolic questions before or after the particulate questions).The same test instrument was used on the same student sample to assess how two types of subscripts affected students understanding of dissolving ionic compounds in water. Two of the ionic compounds had monatomic subscripts (MgCl2, Ag2SO4) and two did not (NaBr, KNO 3). Two had polyatomic subscripts (KNO3, K2SO 4) and two did not (NaBr, MgC12). Students' responses to these questions were also discussed in terms of four variables---Answer (the four choices), Representation (symbolic or particulate questions), Monatomic subscripts, and Polyatomic subscripts. The subscript misconception was more popular for symbolic questions compared to particulate questions, and the correct answer was less popular for particulate and symbolic questions when the question contained a monatomic subscript.Ph.D

And.

https://stars.library.ucf.edu/bookartsexhibit-13thannual/1001/thumbnail.jp

Maternal and child level factors associated with childhood (0-23 months) diarrhoea in Ghana: a pooled analysis of national representative datasets

In Ghana, diarrhoea is one of the leading causes of childhood morbidity and mortality. The objective of this study was to examine maternal and child level factors associated with diarrhoea among children in Ghana. A weighted group of 4,821 mother-child dyads was used for the analysis. The analysis was restricted to mothers with children under 2 years of age. Multivariate logistic regression analysis was performed on the pooled data. The pooled prevalence of diarrhoea among the children was 18 per cent. It was found that children older than five months, rural children, children whose mothers had 24 months or more preceding birth interval, and those houses’ floors made of unimproved materials were more likely to have had experienced diarrhoea. While children with mothers who obtained secondary or higher education and those had access to unimproved sources of drinking water reported less occurrence of diarrhoea. Maternal and child factors have some effects on the occurrence of diarrhoea among children less than two years in Ghana. To decrease the prevalence of childhood diarrhoea in the country, more educative programmes are required for mothers whose children are more likely to having frequent episodes of diarrhoea.Keywords: Maternal, Child, Factors, Diarrhoea, Ghana, Surve

Clustering Effects on Wireless Mobile Ad-Hoc Networks Performances

A new era is dawning for wireless mobile ad hoc networks where communication will be done using a group of mobile devices called cluster, hence clustered network. In a clustered network, protocols used by these mobile devices are different from those used in a wired network; which helps to save computation time and resources efficiently. This paper focuses on Cluster-Based Routing Protocol and Dynamic Source Routing. The results presented in this paper illustrates the implementation of Ad-hoc On-Demand Distance Vector routing protocol for enhancing mobile nodes performance and lifetime in a clustered network and to demonstrate how this routing protocol results in time efficient and resource saving in wireless mobile ad hoc networks.Comment: journal, 19 pages, 14 figures and 1 table, http://airccse.org/journal/ijcsit2014_curr.htm

Assessing Chemistry Teachers Knowledge and Skills in Using ICT in Teaching Organic Chemistry at the Senior High School in the Ashanti Region

The advancement of science and technology vis-à-vis the constant need to improve upon the teaching practice is a course that when successfully put together would efficiently be very advantageous to the students and the teacher. The purpose of the study was to assess the barriers of ICT use, Support system and teachers’ knowledge and skills of ICT use in the teaching of Chemistry in senior high schools (SHSs) in the Ashanti Region. The teachers sampled for the study were from the various types of Senior High Schools (SHSs) such as mixed or co-educational SHSs, single sex female and single sex male in the Ashanti Region. The research instrument that was used to collect the data was questionnaire. Descriptive statistics were carried out to analyze the data using Statistical Package for Social Scientist (SPSS) software version 16. The findings of the study identified perceived barriers of ICT integration in teaching in the SHSs as lack of enough or limited access to computers/computer lab, non-availability of computer software, lack of time in school schedule for integrating ICT and lack of adequate technical support. It also included not get any current technical support for provision of technical course for operating and maintaining computer system and having a technician in the classroom. Teachers’ knowledge and skill in technology use was not seen as a barrier to ICT integration in teaching. It is recommended that computer laboratories should be setup in SHSs and furnished with computers and software that will enable teachers plan and deliver their lesson effectively using ICT. The time table of the SHSs should be reviewed to cater for ICT integration which teachers’ perceived to be time consuming. Keywords: Administrative support, Technical Support, Information and Communication Technology, Senior High School and West African Examination Council DOI: 10.7176/JEP/11-24-03 Publication date:August 31st 202

Utilisation et conservation des ressources en sol et en eau (Nord Cameroun) : rapport final

Après avoir étudié les principaux facteurs régionaux du milieu naturel, une partie de l'étude est consacrée à la caractérisation et à la cartographie des systèmes écologiques de la région de Mouda. Une troisième partie est axée sur les problèmes de fonctionnement des espèces ligneuses et herbacées et fait appel à la connaissance du régime hydrique des sols et à l'organisation des couvertures pédologiques. Une dernière étude, celle du ruissellement et de l'érosion peut être considérée comme la ligne principale du projet