Geochemical Speciation, Spatial Distribution, and Bioavailability of Chromium and Zinc in Urban Estuarine Sediments

International Journal of Chemistry | Vol. 17, No. 3, March 2026 | pp. 17–24

DOI: 10.46882/2026/IJC/000209

Article Type: Original Research Paper

Title: Geochemical Speciation, Spatial Distribution, and Bioavailability of Chromium and Zinc in Urban Estuarine Sediments

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 chromium (Cr) and zinc (Zn) in surface sediments collected from an urban estuarine system 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: Zn > Cr across all sampling locations. Spatial mapping revealed significant pollutant accumulation near industrial drainage channels. Speciation patterns demonstrated that a high proportion of zinc (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 zinc indicated a high environmental hazard rating, highlighting a strong need for local effluent regulatory frameworks.

Keywords: Estuarine sediments; Heavy metals; BCR protocol; Geochemical speciation; Bioavailability; Zinc hazard

Manuscript Timeline: Received: August 05, 2024; Revised: September 18, 2024; Accepted: October 12, 2024; Published: March 11, 2026.

Citation: Obi, C. I., & Kim, S. H. (2026). Geochemical Speciation, Spatial Distribution, and Bioavailability of Chromium and Zinc in Urban Estuarine Sediments. International Journal of Chemistry, 17(3), 17–24.

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