Hydrochemical Assessment and Geospatial Analysis of Borehole Water Quality in Effurun, Delta State, Nigeria

Borehole water is a primary drinking water source in Effurun, Delta State, Nigeria, making its quality a critical public health concern. Contaminants such as major ions and trace metals can affect water safety, necessitating comprehensive assessment. This study evaluates the hydrochemical characteristics of borehole water, identifies contamination sources, and assesses compliance with World Health Organization (WHO) and Nigerian Standard for Drinking Water Quality (NSDWQ) guidelines. The study aims to determine the spatial distribution of major ions and trace metals in borehole water, assess water quality variations, and identify contamination patterns due to natural and anthropogenic influences. Water samples were collected from ten boreholes (BH1–BH10) and analyzed for significant cations (Ca²⁺, Mg²⁺, Na⁺, K⁺), anions (Cl⁻, SO₄²⁻, NO₃⁻, HCO₃⁻), and trace metals (Pb, Cu, Zn, Mn). Statistical analysis, spatial mapping using ArcGIS, and hydrogeochemical modeling (Piper and Durov diagrams) were conducted to determine concentration trends and geochemical interactions. Calcium ranged from 29.95 to 64.50 mg/L, showing moderate correlations with sodium and potassium. Magnesium remained stable (9.50–14.20 mg/L), while chloride levels (39.50–52.70 mg/L) suggested seawater intrusion. Sulfate (18.76–31.20 mg/L) and nitrate (16.78–30.70 mg/L) exceeded permissible limits, indicating contamination from agricultural and industrial sources. Lead levels (0.092–0.127 mg/L) exceeded WHO limits (0.01 mg/L) by over tenfold, posing significant health risks. Higher contaminant concentrations in BH7, BH8, and BH9 indicate surface-groundwater interactions, with increased lead (0.127 mg/L in BH8), chloride (49.90 mg/L in BH7), and nitrate (22.40 mg/L in BH9). The spatial analysis identified southeastern Effurun as a contamination hotspot requiring urgent mitigation. Continuous monitoring, pollution control, and water treatment interventions are essential to ensure safe drinking water. This study uniquely integrates hydrogeochemical, statistical, and geospatial approaches to assess borehole water contamination, providing actionable insights for sustainable groundwater management.