keywords: Core sediment, heavy metals, urbanization, Orogodo River
The concentrations of heavy metals such as Cu, Ni, Pb, Mn, Fe, Cr and Zn were studied in core sediments of Orogodo River, Nigeria to understand heavy metal contaminations of core sediments as a result of urban sprawl and agricultural practices. The core sediment samples were collected from 0 to 60 cm depths using a corers, digested with a mixture of acids and the metal concentrations were quantified using atomic absorption spectrophotometry. The assessment of contamination of the core sediment was based on the enrichment factor and geoaccumulation index. The mean concentrations of metals in the core sediment were 0.5-5.0 mg kg-1 and 0.9 – 8.8 mg kg-1 for Cu; 0.8- 12.9 mg kg-1 and 0.6-6.5 mg kg-1 for Pb; 42.8 -42.1 and 21.8-46.4 mg kg-1 for Mn; 291-713 and 159-704 mg kg-1 for Fe, 0.6-1.1 and 0.3-2.0 mg kg-1 for Cr ; 14.9 -85.9 and 16.3-94.8 mg kg-1 for Zn in dry and wet seasons, respectively. The geoaccumulation index and enrichment factors indicate that the top sections of sediment cores were significantly polluted with Cu, Ni, Pb and Zn in comparison with pre-industrial and urbanization concentrations.The principal components analysis (PCA) results indicated that metals in the sediments originated from myriad of sources which include those associated with traffic, burning of fuel, industrial and as well as municipal wastewater.