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Caractérisation de l’impact des activités humaines sur la qualité de la ressource en eau en milieu urbain sub-saharien : étude de la contamination du bassin versant de la Méfou (Région Centre du Cameroun) par les pesticides et les résidus pharmaceutiques

Abstract : Demographic growth and urbanization create pressure on water resources. Among urban contaminants, pesticides and pharmaceuticals can be discharged into the aquatic environment through agricultural activities and untreated waste waters. Their presence is also reported in global water bodies. Measured contamination levels can have ecotoxicological effects on aquatic organisms as well as on human populations. In Sub-Saharan Africa, these problems are beginning to be highlighted. Local agricultural practices and consumption of pharmaceuticals lead to specific concerns.The aim of this thesis is to identify and characterize the impacts of human activity on the quality of the water resource in urban Sub-Saharan Africa, by analyzing pesticide and pharmaceutical contamination. The study area was the Méfou watershed that drains the political capital of Cameroon, Yaoundé (Center Region).First, the study area was characterized by its environmental (reliefs, land use) and socio-demographic specificities to identify anthropogenic pressures. Urban agricultural practices and in particular the intensive market gardening in the humid lowlands involves the use of massive amounts of pesticides. The absence of a sewage system and the numerous pit-latrines, drains and septic tanks are the sources of diffuse pharmaceutical contamination.Using the example of pesticides, a contaminated runoff mapping method based on susceptibility maps (from the IRIP method) confirmed that some treated plots located in situations that favor runoff were sources of diffuse pesticide contamination. Several areas in the study basin can accumulate this polluted runoff. Next, the multi-criteria SIRIS-Pesticides method from INERIS was applied based on two agricultural scenarios constructed with data sources from the literature. Results pointed to the potential transfer of pesticides from crops to both surface and groundwater.To reinforce these hypotheses, two water quality surveys were conducted in the rainy season between 2015 and 2018, combining grab and passive sampling. Thirty-two pesticides and twenty-four pharmaceuticals were searched for in surface and groundwater in the Méfou watershed. The main results indicate that (i) high concentrations of herbicides and analgesics were detected and quantified in the water samples along with a wide range of targeted compounds; (ii) the contamination pattern showed that the urban area is more polluted than the peri-urban area of Yaoundé; (iii) the measured concentrations pose an environmental risk, in particular the herbicides atrazine and diuron; and (iv) some groundwater sampling points used for drinking water were contaminated by the targeted pharmaceuticals.A social survey conducted in March 2018 around the sampling points identified the risks related to water use. The lack of a sewage system and the discharge of untreated waste water into the immediate surroundings facilitate contamination of the sampling sites. As groundwater is used as an alternative to the tap water network in Yaoundé, the population is also exposed to the risk of pharmaceutically contaminated drinking water.The main results provide baseline information about anthropogenic pressures, contamination levels and related issues in Yaoundé. They raise questions about (i) the transfer of contaminants in the Méfou hydrosystem and (ii) population exposure and potential health risks due to their presence and to the levels of contamination of the water resources.
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https://tel.archives-ouvertes.fr/tel-02005690
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Submitted on : Monday, February 4, 2019 - 11:22:44 AM
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  • HAL Id : tel-02005690, version 1

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Perrine Branchet. Caractérisation de l’impact des activités humaines sur la qualité de la ressource en eau en milieu urbain sub-saharien : étude de la contamination du bassin versant de la Méfou (Région Centre du Cameroun) par les pesticides et les résidus pharmaceutiques. Ingénierie de l'environnement. IMT - MINES ALES - IMT - Mines Alès Ecole Mines - Télécom, 2018. Français. ⟨NNT : 2018EMAL0003⟩. ⟨tel-02005690⟩

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