Sediment characterisation and metal content of Eleiyele River, Ibadan, Nigeria

Abstract

Sediment analysis is one way of evaluating the quality of a water body because sediments are the sink of pollutants in any water body. Samples were collected fortnightly for 6 months at 5 sampling points and analysed for heavy metals (Fe, Mn, Zn, Pb, Cr, Cu, Ni, and Cd)), Nitrate, Nitrite, Phosphate and particle size. The degrees of metal pollution were evaluated using the following pollution indexes; Enrichment ratio (ER), Pollution load index (PLI) and Geoaccumulation index (Igeo). Metal concentration was highest at station 3 but most of the metals (Cr, Ni, Pb, Fe) exceeded the tolerable values provided by FEPA. The ER showed a low value for Mg, Cr and Ni (<1) while Zn and Pb showed mild enrichment (>3). The PLI of lower values implies non-appreciable input from anthropogenic sources. The Igeo values falls between 0-1 suggesting negligible contamination from these metals in the sediment samples. Nitrate is highest at station 1 (3.986mg/kg), Nitrite ranges from 0.271 mg/kg - 0.108 mg/kg. Phosphorus is highest at station 3 (5.102mg/kg) and lowest at station 5 (2.181mg/kg). The textural class of sediment at most stations (Stations 1, 2, 3 and 4) is Fine sand while its coarse sand at station 5.