Étude de la compétitivité de complexation des métaux issus des phosphates naturels de Hahotoé-Kpogamé par les substances humiques

Le phosphate naturel de par sa formule chimique constitue une source importante de l’élément phosphore pour les plantes. Pour cela il est utilisé dans le compost pour améliorer les qualités nutritionnelles des plantes. Les analyses chimiques effectuées sur le phosphate naturel révèlent la présence des métaux lourds. Pour étudier les risques de rétrogradation de ces engrais phosphatés, notre étude s’est portée sur la complexation des substances humiques naturelles extraites des sols sur des ions métalliques tels que le calcium, cadmium et le magnésium contenus dans les phosphates naturels de Hahotoé- Kpogamé du Togo. Les résultats obtenus montrent que la quantité d’ions complexés augment avec le temps d’attaque. Le taux d’ions complexés diminue lorsque le pH de la solution d’acide humique évolue de 6,5 à 9,5. Une étude comparative de la complexation de ces trois ions révèle que le cadmium malgré sa faible teneur dans le phosphate naturel se complexe mieux que le calcium et le magnésium. Après 30 jours d’attaque du phosphate naturel nous avons obtenu un taux avoisinant les 10% pour le cadmium, 9% pour le calcium et environ 2% pour le magnésium pour une solution d’acide humique de pH=6,5.Mots-clés : complexation, métaux lourds, phosphate naturel, rétrogradation, substances humiques.Study on competitiveness of metals after complexation of phosphate rock in Hahotoè-Kpogamé by humic substancesPhosphate by its chemical constitution is an important source of the phosphorus element for plants. Thus, it is used in compost to improve the nutritional qualities of plants. Chemical analyzes of the phosphate reveal the presence of heavy metals. To assess the risk of the phosphate fertilizer downgrading, our study focused on calcium, magnesium, and cadmium ions contents in the humic substances extracted from soils fertilize with Hahotoè-Kpogamé (Togo) phosphate. The results show that the amounts of ions in the complexed humic substances increase with the attack time. The complexed ions rate decreases as the pH of the solution of humic acid changes from 6.5 to 9.5. Despite the low cadmium content in the rock phosphate, this element is more easily assimilated in complex than its two analogous. After 30 days of phosphate attack, a humic acid solution at pH = 6.5 gave a rate of about 10% for cadmium, 9% for calcium and 2% magnesium.Keywords : complexation, heavy metal, rock phosphate, downgrading, humic substances

Epidemiology de l’hepatite virale B chez les Ogo du Togo : prevalence et marqueurs serologiques

But de l’étude: –L’épidémiologie des hépatites virales est peu connue dans les ethnies isolats du Togo. Cette étude a pour but d’évaluer la séroprévalence et l’évolution de l’hépatite virale B chez les Ogo.Patients et méthodes. – Une étude transversale a concerné 538 sujets apparemment sains 433 Ogo et 105 témoins vivant tous dans le même village. La créatinine, les transaminases et gamma-GT ont été dosées. Le dépistage de l’AgHBs et la recherche des marqueurs sériques antigènes et anticorps ont été effectués par immunochromatographie basée sur la technique double sandwich.Résultats. –L’Ag HBs était présent chez 9,96 % des Ogo et 18% des témoins. On observe que 2,94% des Ogo présentaient une hépatite aiguë ou chronique active. L’infection chronique était observée chez 6,05% des Ogo et 5% des témoins. Tandis que 6,2% des Ogo et 8% des témoins étaient guéris mais mal protégés. Les sujets convalescents étaient de 6,48% chez les Ogo et 5% chez les témoins. Les concentrations des transaminases étaient significativement plus élevées chez les témoins (p<0.001) que chez les Ogo.Conclusion: Cette étude révèle que la prévalence de l’HVB est moins élevée chez les Ogo que chez les témoins. Les 14% de la population qui sont des porteurs chroniques sont des sujets vecteurs pour de propagation du virus et présentent des risques de développer à long terme des cirrhoses ou un carcinome. Ces résultats devraient permettre la mise en place de programmes de sensibilisation et de prise en charge sanitaire plus efficaces des populations rurales.Mots clés: Hépatite virale B, Séroprévalence, Ethnie Ogo, TogoEnglish Title: Epidemiology of hepatitis viral B in Ogo population of Togo: prevalence and serological markers English AbstractObjectives: - Epidemiology of viral hepatitis is little known in Togolese isolated ethnic groups. The aim of this study was to investigate seroprevalence and evolution of viral hepatitis B in Ogo population.Patients and methods: - A cross-sectional study involved 538 apparently healthy subjects. They were 433 Ogo subjects and 105 control subjects all living in the same village. Creatinine, transaminases and gamma GT were performed. Screening of HBsAg and the detection of the viral markers: antigens and antibodies were performed by immunochromatography double sandwich technique.Results: Ag HBs was present in 9.96% of Ogo and 18% of controls. We observed that 2.94% of Ogo had acute or chronic hepatitis. Chronic hepatitis was observed in 6.05% Ogo and 5.01% controls. While 6.2% of Ogo and 8% of controls were cured but poorly protected and 6.48% of Ogo and 5% of control were convalescent. Transaminase concentrations were significantly elevated in controls subjects than Ogo (p <0.001).Conclusion - This study reveals that seroprevalence of viral hepatitis B was lower in Ogo than in control. The 14% of the population who are chronic carriers are potential subjects for spreading the virus and present risks of developing long-term cirrhosis or hepatocellular carcinoma. These results will allow to the setting up of a sensitization and health care programs for the rural populations.Keywords: Viral hepatitis B, seroprevalence, Ogo ethnic group, Tog

The Grand Popo experiment, Benin

International audienceThe first large nearshore field experiment in the G ulf of Guinea was conducted at Grand Popo Beach, Be nin, in February 2013, on an open wave-dominated micro- to meso-tidal coast, located mid-way between Cotonou and Lome harbours. The overall project aims at understanding at multi-scale (from event to interannual) the causes of the dramatic erosion observed throughout the Bight of Benin, and caused by the interaction of a large littoral drift with human engineering works. Grand Popo 2013 experiment was designed to measure the processes over the short term and to test the ability of an installed video system to monitor the evolution of this stretch of coast over the longer term. The beach, characterized by a low-tide terrace and a high tide reflective part, experiences a long swell (Hs=1.6m, Tp=16 s, oblique incidence ~15-20°). Topographic surveys showed a double beach cusp system interaction and repeated surf-zone drifter runs revealed high flash and swash rip activity driven by wave dissipation over the terrace and energetic swash dynamics at the upper reflective beach. Swash was measured over a cusp system at two locations using video poles. Wave reanalyses (ERAInterim) were used to determine the wave climate and its variability, and to quantify sediment transport. This robust methodology is thought to be replicated elsewhere in different coastal environments in West Africa, in particular with the objective to monitor various sites within the framework of the new West African Coastal Observatory

The Grand Popo beach 2013 experiment, Benin, West Africa: from short timescale processes to their integrated impact over long-term coastal evolution

The first large nearshore field experiment in the Gulf of Guinea was conducted at Grand Popo Beach, Benin, in February 2013, on an open wave-dominated micro- to meso-tidal coast, located mid-way between Cotonou and Lome harbours. The overall project aims at understanding at multi-scale (from event to interannual) the causes of the dramatic erosion observed throughout the Bight of Benin, and caused by the interaction of a large littoral drift with human engineering works. Grand Popo 2013 experiment was designed to measure the processes over the short term and to test the ability of an installed video system to monitor the evolution of this stretch of coast over the longer tenn. The beach, characterized by a low-tide terrace and a high tide reflective part, experiences a long swell (Hs=1.6 m, Tp=16 s, oblique incidence similar to 15-20 degrees). Topographic surveys showed a double beach cusp system interaction and repeated surf-zone drifter runs revealed high flash and swash rip activity driven by wave dissipation over the terrace and energetic swash dynamics at the upper reflective beach. Swash was measured over a cusp system at two locations using video poles. Wave reanalyses (ERAInterim) were used to determine the wave climate and its variability, and to quantify sediment transport. This robust methodology is thought to be replicated elsewhere in different coastal environments in West Africa, in particular with the objective to monitor various sites within the framework of the new West African Coastal Observatory

Food security for Africa: an urgent global challenge

<p>Abstract</p> <p>In 2012, food insecurity is still a major global concern as 1 billion people are suffering from starvation, under-, and malnutrition, and the Food and Agriculture Organization of the United Nations (FAO) has concluded that we are still far from reaching millennium development goal (MDG) number 1: to halve extreme poverty and hunger by 2015. In sub-Saharan Africa, the number of people suffering from hunger is estimated at 239 million, and this figure could increase in the near future.</p> <p>There are many examples of food insecurity in sub-Saharan Africa, some of them having reached catastrophic dimensions, for example, in the Horn of Africa or southern Madagascar. Food insecurity is not just about insufficient food production, availability, and intake, it is also about the poor quality or nutritional value of the food. The detrimental situation of women and children is particularly serious, as well as the situation among female teenagers, who receive less food than their male counterparts in the same households.</p> <p>Soaring food prices and food riots are among the many symptoms of the prevailing food crisis and insecurity. Climate change and weather vagaries, present and forecast, are generally compounding food insecurity and drastically changing farming activities, as diagnosed by the Consultative Group on International Agricultural Research (CGIAR) in June 2011.</p> <p>The key cause of food insecurity is inadequate food production. Since the global food crisis of 2007–2008, there has been an increasing awareness throughout the world that we must produce more and better food; and we should not be derailed from this goal, despite some relief brought by the good cereal harvests in 2011–2012. This is particularly true in sub-Saharan Africa, which needs and wants to make its own green revolution.</p> <p>The African challenge indeed is key to mitigating food insecurity in the world. Commitments were made by the heads of states and governments of the African Union to double the part of their domestic budgets devoted to agriculture in 2010–2011, so as to reach 10%. Technical solutions exist and there are indeed, throughout Africa, good examples of higher-yielding and sustainable agriculture. But good practices have to spread throughout the continent, while at the same time social and economic measures, as well as political will, are indispensable ingredients of Africa’s green revolution. It is also necessary that international donors fulfil their commitment to help African farmers and rural communities and protect them against unfair trade, competition, and dumping of cheap agrifood products from overseas.</p