Spatial And Temporal Assessment Of Water And Sediment Quality From Coastal Lagoons In The Central And Western Regions Of Ghana

Abstract

Coastal lagoons provide many benefits or services; however, some of these lagoons are under increasing threat of pollution from expanding population and over-exploitation. This study assessed the quality of five coastal lagoons in the Western and Central Regions of Ghana. Sediments and water samples were collected and analyzed for physicochemical parameters and heavy metal concentrations from Muni, Narkwa, Amisa, Fosu and Hwini lagoons from August 2020 to February 2021 . Sediments and water quality were assessed following analytical procedures outlined in the standard methods using water, wastewater and various pollution index indicators. The mean range values for water samples for all the lagoons investigated are; pH, 7.87 - 9.34; DO 2.08- 5.59 mg/L; TDS 23.34 - 32.58 gi L; Cond 36.47 - 50.91 mS/cm; Temp 28.29- 29.67 °C; Sal 36.69 - 58.09 PSU; Nitrate 6.77 - 14.81 mg/L; Phosphate, 3.62- 13.37 mg/L; Turbidity, 5.66 - 45.43 NTU; Fe, 0.81 - 3.1 0 mglL; Pb, 0.64 - 1.09 mg/L; Mn, 0.05 - 0.29 mglL; Cr, 0.05 - 0.39 mg/L; Cd, 0.05 - 0.31 mg/L; Ni, 0.08 - 0.25 mg/L; Zn, 0.18 - 0.40 mglL. The concentration ranges found for the metals in the sediments were Fe 126.20 - 141.10 mg/kg; Pb 12.70 - 27.20 mg/kg; Mn 22.10-37.50 mg/kg; Cr 8.40-21.50 mg/kg; Ni 6.30- 19.80 mg/kg, Zn 9.70 - 23.40 mg/kg. Cadmium (Cd) was below detection limit in all the sediment samples. Significant spatial variations were observed within and between the lagoons. The Nemerow's Pollution Index for all lagoon water were greater than I . The quality of lagoon water for Hwini was fair and marginal for Muni, Fosu, Narkwa and Amisa lagoons. The lagoon sediments were extremely contaminated with regards to all sediment pollution indicators used. These observations suggested anthropogenic pollution of the lagoon water and sediments. There is the need for continuous monitoring of the lagoon ecology by local authorities and institutions mandated to manage these water resources to stop or minimize the deterioration of these lagoons in order to preserve them to sustain the ecosystem.