Heavy Metal Levels in Surface Sediments from Bonny Estuary, Nigeria

Abstract

Essential metals such as Cu and Cr are needed in trace amounts, and their absence may cause serious problems, while non-essential metals such as Cd and Pb have no biological function, and their presence, even in very small quantities, may be toxic. This study aims to assess the level of some heavy metals in sediments of some intertidal creeks around Port Harcourt in the upper Bonny Estuary. The concentrations of heavy metals (Cr, Cd, Pb and Cu) in the sediments of five (5) intertidal creeks (Elelenwo, Choba, Eagle Island, Ogbunabali and Amadi-ama) around Port Harcourt metropolis, Nigeria, for a period of six (6) months, were investigated. Heavy metal concentrations were determined using Atomic Absorption Spectrophotometry. A General linear model of ANOVA was used to test for significant variations in space and time between study areas. The software packages – MS Excel and Minitab R16 were used. There were notable spatial and temporal variations of heavy metal concentrations in sediment across the study areas. Maximum concentrations (mg/kg) of Cr, Cd, Pb and Cu in sediments were 9.75, 3.56, 72.80 and 11.50, respectively. Heavy metal concentrations were discovered to exceed threshold effect values at several stations, with cadmium (0.44-3.56 mg/kg) and lead (72.80 mg/kg) being of particular concern. The study confirmed that areas like Ogbunabali and Choba were hotspots of contamination with regard to heavy metals due to solid waste disposal and discharges in those areas. The study, therefore, concluded that there was heavy metal pollution in the sediments of the intertidal areas studied.