Hydrogeochemical characteristics, sources and human health risk assessment of heavy metal dispersion in the mine pit water-surface water-groundwater system in the largest manganese mine in Ghana

This study was conducted to appraise the hydrogeochemical characteristics and sources of heavy metals and the probable human health risks associated with the consumption of water contaminated with heavy metals in the mine pit water-surface water-groundwater system in the Nsuta manganese mining area in western Ghana. Therefore, a total of 29 samples were collected for hydrochemical analysis and the hydrochemical data was interpreted using multivariate statistical analysis. The results indicate that the pH of water in the mine pit water-surface water-groundwater system is slightly acidic to alkaline in nature. The groundwater evolved from Ca-Mg-SO4, Ca-Mg-HCO3-SO4, Ca-Mg-Na-Cl to Ca-Na-Cl-HCO3 water type with other mixed types, reflecting intense water-rock interaction and dissolution of rocks belonging to the Banded Manganese Formation and the Birimian metasediments in the area. The water is supersaturated with respect to goethite and hematite, pointing to precipitation and dissolution of these minerals. The Water Hazard Index values range from 0.20 to 30.5, implying minimal to extreme toxicity of the water. The mine pit water shows very high Fe, Mn, Ni, As and Sb concentrations, which resulted in hydromorphic dispersion of the heavy metals to the surface water and groundwater. The computed Hazard Index values show higher values (>1) in the surface water and mine pit water, and the carcinogenic risk is low in the groundwater, high in the surface water and extremely high in the mine pit water. Therefore, appropriate control and remedial measures should be urgently put in place to safeguard the health of the people.