Document Type : Original Article
Félix Houphouët Boigny University, Unit Training Research of Earth Sciences and mining resources, Laboratory of Soil, Water and Geomaterials Sciences (SSEG), BP 582 Abidjan 22, Côte d’Ivoire.
Jean Lorougnon Guédé University, Unit Training and Research of Environment, Laboratory of Sciences and Technologies of Environment, BP 150 Daloa, Côte d’Ivoire.
Background : The cocoa crisis en1970s decade in Côte d’Ivoire was manifested by the proliferation of crops pests, reduced production and decreased rainfall. To cope with all these constraints, the producters adopted various strategies, including the use of agricultural inputs to improve the production. Thus, this study aim to characterize the effects of these inputs on water-soil couple.
Methods :. 12 soil and surface water samples were taken for analysis. The determination of trace metal content was done using an Atomic Absorption Spectrophotometer (AAS). Chemical elements were analyzed using a HACH DR 6000 spectrophotometer.
Results : Soil concentrations of exchangeable base Ca2+, K+ and Mg2+ are low with average values of 5.71 cmol/kg, 0.35 cmol/kg and 1.66 cmol/kg respectively. The soils of cocoa orchards are quite rich in assimilable phosphorus (P). The average phosphorus content is 24.31 cmol/kg with a minimum of 3.92 cmol/kg and a maximum of 78.4 cmol/kg. The study of surface water quality showed that the average values of biochemical oxygen demand for 5 days (BOD5) (18.64 mg/L) and chemical oxygen demand (COD) (15.49 mg/L) are lower than the respective standards of 25 mg/L and 125 mg/L of the WHO. These surface waters have average concentrations of 0.015 mg/L for cadmium (Cd), 0.042 mg/L for zinc (Zn) and 0.062 mg/L for manganese (Mn), below the respective standards of 0.003 mg/L, 3 mg/L and 0.4 mg/ L.
Conclusion : This study shows that surface waters are not yet very polluted by these inputs.