Assessment of Hydrochemistry, Facies Type and Processes Contributing the Major Ions to the Groundwater of Ajakanga Area, Ibadan, South Western Nigeria

Abstract

Resulting from insufficient supply of potable water and risk of possible contamination from anthropogenic sources, 14 samples were collected from wells at Ajakanga and environs in Ibadan, Southwestern Nigeria, in order to determine the shallow groundwater quality and desirability for drinking purposes. Physical parameters such as pH, EC, and TDS were measured at site using a combined EC, TDS and pH meter. Major ions analyzed included Na⁺, Ca²⁺, Mg²⁺, K⁺, NO₃^-, Cl^-, HCO₃^- and SO₄^2-. The anions were measured using titrimetric method, and analyzed by Genesys 2.0 Spectrophotometer, while the cations were analyzed using the flame photometry method. The hydrochemical data were subjected to a series of statistical analysis and conventional graphical plots. Results showed that all the chemical parameters analyzed, excepting Cl^- fall within the World Health Organization permissible limit for drinking water. The shallow groundwater is therefore fit for drinking purposes. Cations concentration in the water is in the order of Ca>Mg>Na>K, while for the major anion HCO₃>Cl>SO₄>NO₃. Scatter plots and Gibbs diagram showed that the cations were released into the water as a result of weathering of the underlying basement rocks. Trilinear Piper diagram indicated two water facies in the area, with CaHCO₃ water being dominant, while CaMgHCO₃ is subordinate. Application of Chloro Alkaline Indices and the Ca/HCO₃ ratio indicated that reverse ion exchange reaction is responsible for the dominance of Ca²⁺ and Mg²⁺ in the waters.