Hydrochemical Characterisation and Health-risk Assessment of Drinking Water Sources in Brass Island, Bayelsa State, Nigeria

Abstract

This study evaluates the hydrochemical characteristics and trace-metal contamination of drinking-water sources in Brass Island, Bayelsa State, Nigeria, and assesses their potential health implications. Twelve water samples were collected from boreholes, hand-dug wells, and surface waters during the dry season and analysed for physicochemical parameters, major ions, and trace metals (Fe, Mn, Zn, Pb, Cu, and Cd) following standard procedures. In situ measurements of pH, temperature, electrical conductivity (EC), and total dissolved solids (TDS) were conducted using a multi-parameter meter, while trace metals were quantified using atomic-absorption spectrophotometry (AAS). The results showed slightly acidic pH values (5.2–6.4) and moderate mineralisation, with EC (210–540 µS cm⁻¹) and TDS (125–315 mg L⁻¹) within permissible limits. Major ions revealed low hardness (Ca²⁺ = 12.4–32.1 mg L⁻¹; Mg²⁺ = 5.2–15.8 mg L⁻¹) and mild marine influence (Cl⁻ = 20.5–58.3 mg L⁻¹; SO₄²⁻ = 6.3–19.7 mg L⁻¹). Nitrate concentrations (3.4–21.6 mg L⁻¹) suggested limited anthropogenic enrichment from wastewater and agricultural runoff. Trace-metal analysis indicated that Fe (0.21–1.24 mg L⁻¹) and Pb (0.002–0.042 mg L⁻¹) exceeded guideline limits in some samples, whereas Mn, Zn, Cu, and Cd generally remained within safe ranges. Health-risk assessment using the USEPA (2010) model showed that the cumulative Hazard Index (HI) for adults (0.76) was within the safe threshold (<1), but that for children (1.28) indicated potential non-carcinogenic risk, primarily from Pb and Cd exposure. The study concludes that while the overall water quality in Brass Island is moderate, localised contamination from corroded pipelines, saline intrusion, and oil-related activities poses a long-term health concern. Continuous monitoring, land-use mapping, corrosion-resistant infrastructure, and community-level water treatment are recommended to safeguard public health and ensure sustainable water management in this coastal environment.