5. Assessment of Heavy Metals in Water and Sediments of Sakumo II, Chemu and Kpeshie Lagoons - Ghana

Abstract

This study aimed at assessing the levels of heavy metal pollution in selected lagoons within the Greater Accra Region of Ghana. Water and sediment samples were collected during the dry and wet seasons from selected lagoons, namely; Sakumo II, Chemu and Kpeshie lagoons. The study areas were selected due to the reliance of the people on the lagoons for their livelihood. The lagoons also serve as habitat for diverse fish species. Analysis of the samples were done using the Fast-Sequential Atomic Absorption Spectrometer (VARIAN AA 240FS) fitted with deuterium background corrector. Results from the heavy metals determined (Cu, Pb, Fe, Ni, Zn, and Mn) were compared with the EPA, WHO and USEPA recommended limits, which indicated significant differences in concentrations between the two seasons. The concentration of Copper in the water samples ranged from 2.87 - 3.95 mg/L for Sakumo II lagoon, 8.32-9.39 mg/L for Chemu lagoon and 6.10-6.84 mg/L for Kpeshie lagoon during the dry season. Copper concentrations, however, increased significantly during the wet season with Kpeshie recording the highest mean concentration of 11.69 mg/L. Lead concentration for both seasons did not increase significantly within the study area. Chemu lagoon recorded the highest mean lead concentration of 0.68 mg/L. Chemu lagoon also recorded the highest concentrations of zinc and Iron with values ranging from 17.44-17.83 mg/L and 22.26-23.51 mg/L during the dry season and from 23.80-24.34 mg/L and 27.26-27.89 mg/L during the wet season respectively. Heavy metal concentrations of sediment samples varied widely within the study area with Chemu lagoon recording the highest mean concentrations of all six metals determined for both seasons. The results revealed that, concentrations of both water and sediment samples were highest during the dry season compared to the wet season. Correlations between metals in the sediment samples were statistically significant and positive with values within 0.6 and 1.0 indicating that, the metals in each combination originated from a particular source.