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 cm 3 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.

Suitability of urban river water for irrigation: the case of the Houet river in Burkina Faso

“…Based on the values of EC, %Na and SAR, the Houet river water is excellent for irrigation. These results differ from those of Senou et al (2020) in the dry season who found SAR values of 9, indicating an unsuitable water for irrigation. 64 This difference highlights the importance of the dilution phenomena that take place in the Houet River during the rainy season due to the contribution of rainwater, even after mixing with the wastewater from the WWTP which is polluted.…”

“…These results differ from those of Senou et al (2020) in the dry season who found SAR values of 9, indicating an unsuitable water for irrigation. 64 This difference highlights the importance of the dilution phenomena that take place in the Houet River during the rainy season due to the contribution of rainwater, even after mixing with the wastewater from the WWTP which is polluted. 18,19 The Houet river water could contribute to improve the productivity of market gardening but regarding to anthropic and agricultural activities in addition to the WWTP wastewater release, it is recommended to regularly monitor the river.…”

“…25,62,63 The presence of these elements in water must be controlled as at high concentrations they can hamper crops growth. The variations in Ca 2+ , Mg 2+ , K + , Na + are similar to those found by Senou and al. (2020) in the Houet River during the dry season of 2012.…”

“…(2020) in the Houet River during the dry season of 2012. 64 The concentrations of Cl, Mg, Na and K are similar to those found in the dry season on the Massili River which is the main receptacle of almost all industrial wastewater (treated or not) from the city of Ouagadougou. On the other hand, the concentrations of Cl -, HCO 3 -, PO 4 3-, NO 2 -, NO 3 and NH 4 + , are similar to those reported by Nahli and al.…”