Hydrochemical characteristics and quality assessment of groundwater from shallow wells in Gboloko Area, central Nigeria

Abstract

Physiochemical assessment of shallow groundwater in Gboloko area was carried out  to determine its suitability for drinking and irrigation purposes. Eighteen (18)  groundwater samples were collected from different rural communities’ wells and  subjected field measurements of physical parameters followed by chemical analyses using ICP-MS, ICP-ES, Calorimetry and Turbimetry methods. The results show that pH of the groundwater ranged from 5.1 to 8.6 (mean 6.6) which indicates the  groundwater is slightly acidic and slightly alkaline. EC and TDS varied from 60  to1367mg/L (mean 277.4mg/L) and 53 to 995mg/L (mean 206.5mg/L) respectively. The concentration of major cations were in the order of Ca²⁺>Na+> Mg²⁺> K⁺ while that of anion were in the order of HCO₃ ->Cl-> SO₄ -> NO_3- .Five hydrochemical facies were delineated from Piper plot; they are CaHCO₃,  CaNaHCO₃, CaMgCl, CaCl, and NaHCO₃ water type. CaHCO₃ water is the dominant facies which represents water of recharge zone while CaNaHCO3 and CaCl are the least. The presence of NaHCO3 CaNaHCO3, and CaMgCl water type shows  hydrochemical processes such as ion exchange and linear mixing. The drinking water quality assessment indicates the values for all the hydrochemical parameters are within the maximum permissible standard by WHO, 2006 except for two locations where nitrate concentrations are above the guideline value. The nitrate contamination observed at those locations may be attributed to leachates from domestic wastes and agricultural activities. Although nitrate contamination was expected to be rampant in  groundwater of the area Irrigation water quality indices showed that the groundwater is ranged from mostly suitable to unsuitable.

Key words: Groundwater quality, Gboloko, Hydrochemical Facies, Irrigation water