CONTAMINATION RISK BY HEAVY METALS IN RIVER BIRIM UNDER INTENSE ILLEGAL GOLD MINING IN GHANA

Abstract

Illegal artisanal gold mining has emerged as a major environmental challenge in Ghana, with significant consequences for water resources. This study assessed contamination risks posed by heavy metals in water and sediments of the River Birim, a river system severely impacted by unregulated mining. Water and sediment were obtained using standard protocols and analyzed for metals such as iron (Fe), manganese (Mn), nickel (Ni), cadmium (Cd), zinc (Zn), chromium (Cr), lead (Pb), and mercury (Hg) using atomic absorption spectrophotometry. Sediment concentrations (mg/kg) followed the order Fe (8986.33) > Mn (425.90) > Ni (24.68) > Cd (17.67) > Zn (11.23) > Cr (2.50) > Pb (1.33) > Hg (0.50), while water concentrations (mg/L) ranked as Fe (5.36) > Cd (0.23) > Ni (0.08) > Zn = Hg (0.04) > Cr = Mn (0.03) > Pb (0.02). Concentrations of Cd, Fe, Pb, Hg, and Ni in water exceeded World Health Organization (WHO) limits for potable water. Sediment quality indices indicated moderate to severe contamination by Hg and Cd, with cadmium alone contributing approximately 98% of the total ecological risk (PERI = 10,827.3). Non-carcinogenic risks were below the threshold of concern (HI < 1). However, carcinogenic risk assessments revealed ingestion of Cd- and Ni-contaminated water and Cd-rich sediments exceeded permissible limits, suggesting potential long-term health implications. These findings highlight the urgent need for stricter environmental regulation, sustainable mining practices, and continuous monitoring to protect communities reliant on the River Birim.