Geochemical Analysis of Groundwater in Central Cross River State: Implications for Water Quality and Public Health

Groundwater quality in Central Cross River State, Nigeria, is vital for public health and sustainability. This study evaluates the geochemical characteristics of groundwater in parts of the central Cross River State within the Ikom-Mamfe Embayment, analyzing physicochemical parameters, major ions, trace metals, and correlation matrix analysis. A total of 23 boreholes were sampled, revealing pH values between 6.17 and 8.50 (mean: 6.87) and electrical conductivity (EC) ranging from 28.67 to 198.50 µS/cm (mean: 133.43 µS/cm). Major anions include chloride (Cl⁻) at 0.25–5.10 mg/L (mean: 1.74 mg/L), fluoride (F⁻) at 0.03–0.21 mg/L (mean: 0.13 mg/L), nitrate (NO₃⁻) at 0.10–2.00 mg/L (mean: 0.91 mg/L), nitrite (NO₂⁻) at 0.01–1.10 mg/L (mean: 0.16 mg/L), and sulfate (SO₄²⁻) at 4.50–7.20 mg/L (mean: 5.85 mg/L), all within WHO limits. Major cations include calcium carbonate (CaCO₃) at 11.00–376.00 mg/L (mean: 134.71 mg/L), iron (Fe²⁺) at 3.05–6.23 mg/L (mean: 4.44 mg/L), magnesium (Mg²⁺) at 0.10–0.49 mg/L (mean: 0.16 mg/L), manganese (Mn²⁺) at 0.10–0.32 mg/L (mean: 0.16 mg/L), and sodium (Na⁺) at 1.10–1.41 mg/L (mean: 1.14 mg/L).Hydrogeochemical facies analysis (Piper and Durov diagrams) classifies groundwater as predominantly Ca-HCO₃ type, indicating carbonate dissolution as a key influence. Correlation matrix analysis revealed strong associations between EC and major cations/anions, highlighting mineral dissolution as a primary control on groundwater chemistry. Negative correlations between pH and Fe²⁺ (-0.453) and Mn²⁺ (-0.045) suggest that lower pH levels increase metal solubility, while positive correlations between turbidity and Fe²⁺ (0.354) indicate potential contamination sources. Elevated Fe²⁺ and Mn²⁺ concentrations exceed WHO drinking water guidelines, posing health risks. While groundwater remains largely suitable for irrigation, localized anthropogenic contamination from agriculture and waste disposal necessitates improved monitoring, pollution control, and targeted water treatment strategies. Sustainable groundwater management policies are essential to ensure long-term water safety in the region.