ISSN 2995-9246
International Journal of Chemistry | Vol. 1, No. 7, July 2010 | pp. 52–60
DOI: 10.46882/2010/IJC/000007
Article Type: Original Research Paper
Title: Speciation and Spatial Distribution of Heavy Metals in Surface Sediments of the Lagos Lagoon System
Names of Authors: Babajide A. Adeisa¹, Ngozi E. Chukwu¹, Hans-Dieter Meier²
Authors’ Affiliations:
¹Department of Marine Sciences, University of Lagos, Akoka, Nigeria
²Institute for Chemistry and Biology of the Marine Environment, University of Oldenburg, Oldenburg, Germany
Abstract: Heavy metal pollution in coastal lagoons poses a severe ecological threat to benthic organisms and commercial fisheries. Surface sediment samples collected from ten strategically selected stations across the Lagos Lagoon were analyzed to evaluate the total concentrations and chemical speciation of Cadmium (Cd), Chromium (Cr), Copper (Cu), Lead (Pb), and Zinc (Zn). Spatial distribution patterns showed that heavy metal accumulation was drastically elevated in areas near industrial wastewater discharges and urban runoff channels. A modified Tessier sequential extraction procedure was employed to fractionate the metals into five operational pools: exchangeable, bound to carbonates, bound to iron-manganese oxides, bound to organic matter, and residual. Total metal levels ranged as follows: Zn (112.4–345.8 mg/kg) > Cr (45.2–128.5 mg/kg) > Pb (18.6–94.2 mg/kg) > Cu (12.4–65.3 mg/kg) > Cd (1.1–5.4 mg/kg). Speciation analysis revealed that Cd and Pb were predominantly associated with the exchangeable and carbonate fractions (35% and 28%, respectively), highlighting their high mobility, bioavailability, and potential toxicity to the aquatic ecosystem. Conversely, Cr and Cu were mostly locked within the organic and residual fractions, suggesting lower immediate ecological risk. The pollution load index (PLI) indicated significant anthropogenically driven deterioration across the lagoon system.
Keywords: Heavy metals, Sediment speciation, Tessier extraction, Bioavailability, Lagos Lagoon, Environmental pollution
Manuscript Timeline: Received: April 15, 2010; Revised: May 24, 2010; Accepted: June 15, 2010; Published: July 02, 2010