Geochemical Speciation, Spatial Distribution, and Ecotoxicological Risk Assessments of Cadmium and Chromium in Coastal Estuaries

International Journal of Chemistry | Vol. 10, No. 4, April 2019 | pp. 25–32

DOI: 10.46882/2019/IJC/000126

Article Type: Original Research Paper

Title: Geochemical Speciation, Spatial Distribution, and Ecotoxicological Risk Assessments of Cadmium and Chromium in Coastal Estuaries

Names of Authors: C. I. Obi¹, S. H. Kim²*

Authors’ Affiliations:
¹Department of Pure and Industrial Chemistry, University of Port Harcourt, Port Harcourt, Nigeria.
²Department of Chemistry, Seoul National University, Seoul, South Korea.

Abstract: Total concentrations of heavy metals are insufficient to assess ecological risk in coastal bodies because environmental mobility and bioavailability depend heavily on specific chemical binding forms. This study evaluates the total concentration and geochemical speciation fractions of cadmium (Cd) and chromium (Cr) in surface sediments collected from an urban coastal estuary exposed to municipal and industrial waste discharges. Quantitative analysis was performed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) following the modified BCR three-step sequential extraction procedure. The total metal concentrations followed the sequence: Cr > Cd across all sampling locations. Spatial mapping revealed significant pollutant accumulation near industrial discharge channels. Speciation patterns demonstrated that a high proportion of cadmium (45.2%) was associated with the acid-soluble and exchangeable fractions, suggesting high structural instability and bioavailable risks to benthic organisms. Conversely, chromium was primarily bound within the residual and organic matrices, indicating low immediate mobility under baseline pH conditions. The Risk Assessment Code (RAC) calculated for cadmium indicated a high environmental hazard rating, highlighting a strong need for local effluent regulatory frameworks.

Keywords: Coastal estuary; Sediments; Heavy metals; BCR protocol; Geochemical speciation; Bioavailability

Manuscript Timeline: Received: May 11, 2018; Revised: June 22, 2018; Accepted: July 18, 2018; Published: April 02, 2019.

Citation: Obi, C. I., & Kim, S. H. (2019). Geochemical Speciation, Spatial Distribution, and Ecotoxicological Risk Assessments of Cadmium and Chromium in Coastal Estuaries. International Journal of Chemistry, 10(4), 25–32.

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