Geochemical Speciation, Spatial Distribution, and Environmental Risk Assessments of Lead and Nickel in Estuarine Mudflats

International Journal of Chemistry | Vol. 8, No. 7, July 2017 | pp. 49–56

DOI: 10.46882/2017/IJC/000106

Article Type: Original Research Paper

Title: Geochemical Speciation, Spatial Distribution, and Environmental Risk Assessments of Lead and Nickel in Estuarine Mudflats

Names of Authors: C. I. Obi¹, M. H. Chang²*

Authors’ Affiliations:
¹Department of Pure and Industrial Chemistry, University of Port Harcourt, Port Harcourt, Nigeria.
²Department of Marine Science, National Sun Yat-sen University, Kaohsiung, Taiwan.

Abstract: Monitoring total metal concentrations alone is inadequate to assess environmental risk in coastal estuarine zones because heavy metal mobility and bioavailability depend heavily on specific chemical binding forms. This study evaluates the total concentration and geochemical speciation fractions of lead (Pb) and nickel (Ni) in surface sediments collected from five mudflat nodes exposed to urban storm-water discharge channels. Quantitative analysis was performed using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) following the five-step Tessier sequential extraction protocol. The total metal contents followed the sequence: Pb > Ni across all monitored coordinates. Spatial distribution evaluations revealed significant metal accumulation downriver from industrial zones. Speciation patterns demonstrated that a high proportion of lead (38.5%) and nickel (24.2%) existed within the exchangeable and carbonate-bound fractions, which are highly unstable and bioavailable to benthic organisms. Conversely, remaining fractions were bound within residual and organic-bound matrices, implying low immediate mobility under baseline pH conditions. The Risk Assessment Code (RAC) calculated for lead indicated a high environmental hazard threat level, highlighting a need for regulatory treatment protocols.

Keywords: Estuarine sediments; Speciation analysis; Tessier protocol; Bioavailability; Lead contamination; Risk Assessment Code

Manuscript Timeline: Received: August 05, 2016; Revised: September 18, 2016; Accepted: October 12, 2016; Published: July 08, 2017.

Citation: Obi, C. I., & Chang, M. H. (2017). Geochemical Speciation, Spatial Distribution, and Environmental Risk Assessments of Lead and Nickel in Estuarine Mudflats. International Journal of Chemistry, 8(7), 49–56.

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