Hydrogeochemical evaluation and geospatial distribution modeling of the major ion chemistry of groundwater and their suitability for drinking and irrigation in Lagelu, Southwestern Nigeria

Abstract

Shallow groundwater is an essential resource for domestic, agricultural, and small-scale industrial uses in Lagelu in Oyo State, Southwestern Nigeria. A total of 20 representative groundwater samples were collected from different hand-dug wells and analyzed for the major cations, anions, and heavy metals to establish their suitability for drinking and irrigation. Geospatial variation maps of the major cations and anions were produced using the inverse distance weighted algorithm. The results of the respective concentrations of pH, TDS, EC, HCO3−, NO3−, SO42−, Cl−, PO42−, Ca2+, Mg2+, Na+, K+, Zn2+, Cu+, Pb2+, and As+ except Fe2+ are within the recommended range set by the World Health Organization (WHO) and Nigerian Industrial Standards for Drinking Water Quality (NSDWQ). Based on the hydrogeochemical facies, the groundwater belongs to Na+–K+–Cl−–SO42−, and Ca2+–Mg2+–Cl−–SO42− water types. Gibb’s diagram shows that the interaction of rocks and water dominate the processes that control the ionic compositions of the groundwater due to rock weathering and dissolution. The correlation matrix that specifies the ion concentration relationship showed that TDS, K+, and Fe2+ strongly correlate positively with EC, Na+, and Ca2+, respectively. CO32−, Na+, and Cu moderately correlate positively with Cl−, Mg2+, and pH, respectively. The indices used to determine groundwater suitability for irrigation classified over 90% of the samples as suitable for irrigation