Study of physicochemical parameters and level of cadmium and lead contamination in irrigation water in market garden areas in West Burkina Faso

Abstract

 The market gardening areas of Kodeni and Dogona are among the main market gardening sites in the city of Bobo-Dioulasso (Burkina Faso). On these vegetable perimeters, the forms of water mobilization for irrigation are essentially wells for the Kodeni site and wastewater from sewers for Dogona. In order to assess the physico-chemical quality and the level of cadmium and lead contamination in these waters, samples were taken at different points on each site and outside the site. The method used is based on the sampling of water in 0.5 liter polyethylene bottles, previously rinsed twice with the sample to be taken. The first samples are used to rinse the bottles and perform physical field analyzes which are pH, electrical conductivity (CE), temperature, salinity, turbidity and total dissolved solids (TDS). Each sample was acidified with pure analytical concentrated nitric acid (HNO3) (0.5 cm3 in 0.5 liters of water) which was used to determine the metals. Physico-chemical analyzes and the level of cadmium and lead contamination were carried out. The results of these analyzes were processed using hydrochemical techniques (Piper diagram). Principal Component Analysis (PCA) has also been used to highlight the phenomena of mineralization of water in these market gardening areas. The results obtained show that these irrigation waters are acidic at the Kodeni site (pH = 5.49) and basic for the Dogona site (pH = 7.95). They are weakly mineralized at the Kodeni site with an average conductivity of 52.56 4µS/ cm and strongly mineralized at the market garden area of Dogona with an average conductivity of 508.4 4µS / cm. The cadmium and lead contents are sometimes higher than those recommended by the WHO (0.01 mg/ L for cadmium and 0.003 mg/ L for lead). The chemical facies give sodium calcium water. The value of the sodium absorption ratio (11.85) of the water at the Dogona site and that of the pH (5.49) at the Kodeni site show that the irrigation water is chemically unsuitable for agricultural use during the dry season.