Some chemical characteristics of the river Pra estuary in the Western Region of Ghana

Abstract

This paper discusses the nutrients budget and transfers of mineral nutrients from land to the sea that influence significantly the biogeochemical process operating in the coastal ecosystem. Water samples were collected fortnightly from six sites in the estuary and analysed using standard methods of analyses. It was observed that the estuary is alkaline in nature and the alkalinity increases, in the lower reach of the river as it flowed into the sea. The estuary could be classified as a well-mixed estuary due to the vertical homogenous distribution of salinity. The inorganic nitrogen in the water body exists predominately in the form of nitrate (NO3 - ), as compared to concentrations of ammonium (NH4 ) and nitrite (NO2 - ). The ranges of NO3 - , NH4 + and NO2 - concentrations are (4.98-8.27), (0.11-0.46) and (0.005-10.95) x 10-3 mg/L. The concentrations of nitrate, nitrite, ammonium and phosphate were found to be within WHO specification. The calculated residual flow (VR) for both November and December are -2.7 x 10 7 m 3 day-1 and -1.01 x 10 7 m 3 day-1, respectively. The negative value of V R implies that water flows from the system. The corresponding residence and flush times are 324 and 109 seconds and 828 and 595.2 seconds for November and December, respectively