In order to protect and improve market garden crops, market gardeners use large quantities of plant protection products and water in the production area. This has an impact on soil quality. The aim of this study was to determine the level of soil pollution downstream of the Daloa Regional Hospital. Twenty-four soil samples were taken from six sites in the study area. These samples were analysed by liquid/liquid chromatography coupled with mass spectrophotometry. The results of the analyses revealed the presence of seven medicinal residues, including five antibiotics (Ciprofloxacin, Erythromycin, Tetracycline, Sulfamethoxazole and Norfloxacin), a beta-blocker (Propranolol) and an anti-inflammatory (Salicylic Acid). The average concentrations of these antibiotic residues ranged from 3.41 to 50.34 µg/kg; the anti-inflammatory and the beta-blocker recorded values of 112.67 µg/kg and 17.35 µg/kg respectively. Eleven residues of active ingredients, including Chlorothalonil, Cypermethrin, Metamidophos, Endrin, Deltamethrin, Dimethomorph, Profenofos, Beta-endosulfan, Etoenprox, Furathiocarb and Carbendazim, were quantified at levels ranging from 0.04 to 39.62 µg/kg. These active ingredients belong to five families of plant protection products: organochlorines, organophosphates, carbamates, thiocarbamates and synthetic pyrethroids. The constant discharge of these medicinal and phytosanitary residues contaminates the soil and poses a threat to humans and their environment.

The people living along the Lobo catchment area in Nibéhibé are experiencing difficulties in supplying drinking water due to the impacts of climate variability and the anthropic pressures on the surface water used. The objective of this study is to characterise the groundwater-river interactions based on the major fracturing and the hydrographic network. The hydrographic network and the major fracturing map were used as data for the different treatments. Also, the hierarchy of the hydrographic network using the Strahler method highlighted the rivers of order 1 to 5. Frequency curves of the number of drains and cumulative lengths according to Strahler's orders were constructed and then interpreted using the «law of rivers» to detect drains with a structural origin. The distribution of drains in the river system follows the exponential law with a good correlation coefficient (R² =0.97). Moreover, the coupling of the map of watercourses of structural origin and the map of major fractures has made it possible to highlight potential areas of groundwater-river exchange. These zones represent the intersection of permanent watercourses and areas of very high fracture density.

Rice is a strategic axis of socio-economic development of the region of Denguele because of the population increase. In spite of the essential role which plays the rice in the consumption of the population in developing countries, its production remains always insufficient. National policy of C