Author(s) :

Prince Bofati Ilonga, Mohamed Meddi, Antoinne Kihumba Mfumu, Belgacem Samir Bekkoussa, Génie-Spirou Kiala Lutonadio, Raphael Mwamba Tshimanga.

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Abstract :

The objective of this study was to assess the physicochemical and isotopic quality of groundwater used for irrigation at the N'Djili Cecomaf agricultural site. The mixed approach used was based on hydrochemical and isotopic analyses combined with multivariate statistical analyses. The groundwater samples from the wells were collected during the rainy and dry seasons of 2023 for hydrochemical and isotopic analyses. The results showed that the groundwater is characterized by a dominant chemical facies of the chloride-calcium and magnesium type. PCA revealed weak positive correlations between Ca2+, Mg2+, NO3-, HCO3-, SO42-, Cl- and EC ions in both seasons. Furthermore, the waters are poorly mineralized, with a very low degree of salinity. Nitrate concentrations exceed 50mg/l and are an indicator of the pollution of these waters because of fertilizers and various manures used on the site, but also of contamination by the waters of the N'Djili River, which carry suspended solids, especially during the rainy season. The Oxygen-18/Deuterium and deuterium excess (d-excess) relationships showed that the water captured by these wells comes from meteoric waters resulting from the infiltration of rainfall during the rainy season and/or from interactions with the waters of the N'Djili River, which drain the lowland. These waters are beneficial for plant nutrition. Based on the sodium adsorption ratio, permeability index and magnesium absorption rate, these waters are excellent for irrigation.

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