Hydrogeochemistry and human health risk assessment of heavy metal pollution of groundwater in Tarkwa, a mining community in Ghana

Abstract

The current study investigated the geochemical characterization and contamination of groundwater quality in Tarkwa, a mining community in Ghana. Total dissolved solids, electrical conductivity, calcium, magnesium, sodium, potassium, total dissolved solids, total hardness, heavy metals, and cyanide (CN) were all assessed in 74 groundwater samples. Other parameters assessed included pH, electrical conductivity, carbonate, bicarbonate, chloride, sulphate, nitrate, and pH. Using the method recommended by the USEPA, a health risk assessment was carried out. Among the parameters which exceeded their WHO recommended threshold were pH (4.9–7.7), Conductivity (150–1082 µS/Cm), Turbidity (1.4–139.5 NTU), Magnesium (1.9–395.5 mg/L), Nitrate (4.5 mg/L–760 mg/L), phosphate (2.3–80 mg/L), Sulphate (10–855.6 mg/L), CN (1.6–16 mg/L), As (0.001–0.015 mg/L), Hg (0.001–0.005 mg/L), Cd (ND-0.009 mg/L), Mn (0.004–1.38 mg/L), Ni (0.002–0.118 mg/L). The study also showed that the groundwater in Tarkwa is naturally hard, making Ca and Mg ions the main ions determining the chemistry of the water. Similar to this, the most significant factors affecting water chemistry were rock dominance and precipitation dominance. Due to high levels of CN, As, and Cd, health risk evaluation revealed that prolonged intake of groundwater from Tarkwa is linked to both carcinogenic and noncarcinogenic health risk. Children were shown to be more vulnerable to both carcinogenic and noncarcinogenic health risks than adults.

Keywords

• Water Quality
• Gibbs plot
• Hydrogeochemistry
• Risk assessment
• Groundwater