Assessing the Effects of Heavy Metal Concentration in Stream Sediments Within Onne and Environs Southeastern Nigeria

Abstract

This study assessed the seasonal variations in heavy metal concentration of stream sediments in parts of Onne,  Rivers state Southeastern Nigeria. River Ogu was mapped for the collection of stream sediments because of its prominence as a receptor of a lot of effluents discharge from the NNPC oil refinery, erosion and weathering of heavy metals from nearby towns. Stream sediment samples were obtained from eleven (11) strategic locations at 3km interval and; a control sample was obtained from Akpajo river to cover both the dry and wet seasons. Samples were analyzed with Atomic Absorption spectrometric method (AAS) and X-ray fluorescence spectroscopy (XRF) for Ni, Cu, Hg, Pb, Zn,Cd, As and Cr. The record of the relative abundance of the heavy metals in the stream sediments in decreasing order for both seasons is as follows;  Zinc (Zn) > Nickel (Ni) > Cadmium (Cd) > Copper (Cu) > Chromium (Cr) > Mercury (Hg) > Lead (Pb) > Arsenic (As). Higher mean concentration values were generally recorded in the wet season than in dry season. Four elements  (Zn, Cd, Ni and Cu) were found to be far higher than tolerable standard of the Federal Ministry of Environment (FME, 2006). The sources of the heavy metals are attributed to Onne refinery, Onne waste dump, runoff from roadside soil, acidic precipitation and effluents from petrochemical industries. Excessive concentrations of heavy metals in the stream sediments affects the aquatic life of the faunas and floras and have adverse effect on humans and this calls for regular monitoring of the chemistry of stream sediments in the area.

Keywords: Heavy metal, stream sediments, Atomic Absorption Spectrometry (AAS), x-ray fluorescence spectroscopy (XRF), River Ogu, Onne .

DOI: 10.7176/JEES/9-10-05

Publication date:October 31^st 2019