Comparison of Inorganic Contamination of Pyrometallurgy and Hydrometallurgy Sites at Obuasi

This study investigates inorganic pollutant concentrations in streams and sediments affected by pyrometallurgical and hydrometallurgical gold ore processing at the Obuasi mine, Ghana. Water and sediment samples were analyzed for pH, major anions (NO₃⁻, Cl⁻, SO₄²⁻), cations (Na⁺, K⁺, Ca²⁺, Mg²⁺), and trace metals (As, Cu, Fe, Zn, Pb). Water pH ranged between 5.80 and 7.50, with elevated anion and metal levels across both sites. Pyrometallurgical effluents exhibited higher trace metal concentrations (0.01–5.00 mg/L) and markedly elevated SO₄²⁻ (0.85–945.50 mg/L), while hydrometallurgical effluents showed greater NO₃⁻ (0.01–95.39 mg/L) and Cl⁻ (1.00–49.05 mg/L) concentrations. In water, Ca²⁺ and SO₄²⁻ were the dominant cation and anion, respectively. Sediments from hydrometallurgical zones contained substantially higher levels of most parameters, excluding pH, NO₃⁻, Cl⁻, Na⁺, and Mg²⁺. Average sediment concentrations of Ca²⁺, Mg²⁺, As, and Fe ranged from 3,217 to 46,026 mg/kg. Overall, pyrometallurgical processes contributed greater pollutant loads to water, whereas hydrometallurgical processes resulted in higher sediment contamination. These contrasting geochemical patterns underscore the influence of ore processing methods on pollutant partitioning between water and sediments, with implications for environmental monitoring and remediation in mining regions.