Contamination des eaux de puits traditionnels par les nitrates sur le bassin versant de la Lobo (Buyo, sudouest de la Côte d’Ivoire)

Objective: Contamination of groundwater by nitrates is a real public health concern that is currently being paid a particular attention worldwide. This study investigates the spatial distribution of nitrates in traditional water supply wells in the Lobo's watershed, in order to derive appropriate measures to protect groundwater resources in this region. Methodology and Results: the origin of nitrate water from traditional wells of Lobo’s watershed was determined through the analysis of nitrate concentrations. The samples were collected in March (dry season) and June (wet season) 2007 on the waters of traditional wells in two villages Gbili and Logbozoa and camps on the lobo’s watershed. The results show that nitrate concentrations vary on the watershed. In general, concentrations range from 0 mg.L-1 to 71,26 mg L-1. Wells with a concentration above the guideline value of WHO (50 mg.L-1) are found in Buyo and both villages Gbili and Logbozoa. On the other hand, wells of Tchemasso, Buyo Provisoire and camps have nitrate levels complying with the standard. Conclusion and application of results: Well waters of Buyo and two villages Gbili and Logbozoa with higher population densities are richer in nitrate. On the contrary, wells of Tchemasso, Buyo Provisoire and camps, with lower population density and sometimes with wells in plantations have low levels. Thus, the high population density, coupled with the lack of sanitation and incorrectly installed latrines, is the main cause of high nitrate levels in traditional water supply wells in the Lobo’s Watershed. Water wells located in plantations with low nitrate levels show that agriculture is not responsible for the contamination of water in this area. In the short term, an appropriately designed awareness campaign on sanitation and public health directed to the populations should be initiated to allow improving and protecting well water quality in the Lobo’s watershed.Keywords: anthropogenic activity; groundwater; pollution; physico-chemical quality