Heavy metals concentration and pollution index (HPI) in drinking water along the southwest coast of Ghana

Abstract

The concentration of seven heavy metals in water samples was analyzed along the southwest coast of Ghana in the wet and dry seasons using atomic absorption spectrophotometer. Some physicochemical properties of the water samples were also determined to assess the quality of the water. The ranges of metal concentration in water in the wet season were; As (1.23–7.84 µg/L), Cu (4.10–24.09 µg/L), Pb (4.08–57.98 µg/L), Se (BDL-0.38 µg/L), Zn (2.86–17.75 µg/L) and Hg (0.023–0.068 µg/L), whereas the ranges of metal concentration in the dry season were; As (2.30–5.78 µg/L), Pb (25.47–70.73 µg/L), Se (0.081–0.158 µg/L), Zn (0.79–22.80 µg/L) and Hg (0.004–0.047 µg/L). The results of physicochemical properties of water in the wet season were pH (6.83 to 7.52), EC (291.15–780.64 µS/cm), TDS (195.07–523.02 mg/L), DO (2.98–4.39 mg/L), BOD (3.33 to 6.84 mg/L), salinity (0.01 to 0.30 ppt) and temperature (27.06–30.94 °C), whereas the dry season recorded the ranges of pH (6.84–6.95), EC (516.83 to 660.67 µS/cm), TDS (307.07–442.65 mg/L), DO (1.71–3.04 mg/L), BOD (4.25–13.38 mg/L), salinity (0.22–0.28ppt) and temperature (28.46–30.44 °C). The results showed that the concentration of heavy metals in water was below the WHO standard except Pb which exceeded the limit. The mean heavy metal pollution index (HPI) were 130 and 143 for wet and dry seasons, respectively, indicating that the water HPI was above the critical limit (HPI > 100), hence unfit for drinking. All the physicochemical properties analyzed were within the WHO permissible limits except BOD.