Geochemical assessment and speciation of metals in sediments of Osun and Erinle Rivers, Southwestern Nigeria
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ORIGINAL PAPER
Geochemical assessment and speciation of metals in sediments of Osun and Erinle Rivers, Southwestern Nigeria O. W. Okunola 1 & A. S. Olatunji 2
Received: 21 April 2016 / Accepted: 18 July 2017 # Saudi Society for Geosciences 2017
Abstract Fifty sediment samples were collected from Osun (urban) and Erinle (suburban) rivers in addition to ten samples of the underlying rock types (schist and gneiss) and analyzed for elemental constituents while speciation of metals was determined by sequential analysis. Data were geochemically evaluated and ArcGIS was used to generate geochemical maps. Metal concentrations (ppm) in suburban and urban areas were Cd (0.2–0.2, 0.2–1.1), Cu (37.0–272.0, 49.0–970.0), Ni (6.0–27.0, 3.0–43.0), Pb (16.0–67.0, 15.0–2650.0), Zn (32.0–170.0, 50.0–987.0), Co (8.0–60.0, 2.0–86.0), Cr (26.0–153.0, 9.0–128.0), V (30.0–142.0, 9.0–135.0), and Mn (442.0–5100.0, 107.0– 3930.0), respectively. In the rocks, Cu, Ni, Pb, Co, Cr, V, and Zn, concentrations (ppm) were below detection limit (BDL)-0.05, BDL-38.00; 6.23–12.00, BDL-20.00; 3.78– 6.23, BDL-5.00; BDL-0.20, BDL-4.00; 5.00–9.00, BDL66.00; 15.99–32.00, BDL-130.00; and 18.00–26.00, BDL48.00, respectively, with Cu, Pb, Zn, Cd, and Mn of elevated concentrations in sediments compared with that of the rocks, being indication of additional anthropogenic sourcing. Calculated contamination indices revealed contamination for sediment from the urban areas compared to those from the sub-urban. High percentage of Pb (2.94–81.92%), Cu (31.69–45.95%), Zn (49.2–65.5%), Cd (31.69– 45.95%), and Mn (12.13–37.50%) are hosted by the bioavailable phases (carbonate, organic, and sulfide). The geochemical distribution of metals in the sediments of the
* A. S. Olatunji [email protected] 1
Nigerian Geological Survey Agency, Abeokuta office, Abuja, Nigeria
2
Department of Geology, University of Ibadan, Ibadan, Nigeria
Osun and Erinle rivers is governed by both geogenic (Ni-CrCo-V) and anthropogenic (Pb-Cd-Zn) activities. Elevated concentration and occurrences of the selected metals in the bio-available phases pose potential health risk to people in the urban area. Keywords Sequential analysis . Anthropogenic . Contamination indices . Bioavailable phases
Introduction In many developing countries such as Nigeria, rapid urban and industrial expansion is closely linked to increased environmental degradation and pollution. Osogbo metropolis is the political capital of the State of Osun in southwestern Nigeria (Fig. 1). The city is one of the fast-developing socio-economic centers in Nigeria, aggressively developing without commensurate planning. The city has thus become associated with poor land use pattern, poorly constructed and maintained sewage and waste disposal systems, as well as high traffic density. These unregulated developments have resulted in indiscriminate dumping of refuse and discharge of waste water into the drainage channels within the city. The solid wastes and waste water eventually find their way into Osun and Erinle rivers, the tw
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