Hydrogeochemical Controls on Groundwater Quality in Agricultural Communities of Benue State, Nigeria

Abstract

Groundwater is an important source of domestic water supply in agricultural communities, but its chemistry may reflect both natural geochemical processes and land-use inputs. This study evaluated hydrogeochemical characteristics and controls on groundwater quality in four agricultural communities of Benue State, Nigeria. Thirty-two groundwater samples were analysed for physicochemical parameters, major ions and selected potentially toxic metals using standard analytical procedures. Community-level summaries, Piper and Gibbs graphical analysis, Pearson correlation and principal component analysis (PCA) were used to identify dominant hydrochemical patterns. Community mean pH ranged from 6.23 to 6.91, electrical conductivity from 241 to 527 µS/cm and total dissolved solids from 154 to 336 mg/L. Calcium and bicarbonate were the dominant major ions, while community-mean nitrate concentrations ranged from 9.6 to 29.8 mg/L and were highest in Community C. The community-mean major-ion compositions plotted within a Ca–Mg–HCO₃-dominated field. Strong correlations among EC, TDS, Ca²⁺, Mg²⁺ and HCO₃⁻ supported a substantial mineralisation component, whereas associations of NO₃⁻ with K⁺ and Cl⁻ were consistent with an additional land-use influence. PCA identified four components accounting for 78.46% of total variance. The evidence supports water–rock interaction as the principal hydrochemical background, with superimposed anthropogenic signals. Community C showed the greatest chemical enrichment and warrants priority in future monitoring.