Geochemical Assessment and Statistical Characterisation of Heavy Metal Contamination in Estuarine Sediments of Ondo State, Nigeria.

Estuarine sediments in developing coastal regions are becoming increasingly vulnerable to heavy metal
contamination caused by human activities, yet comprehensive assessments remain rare in West African coastal
systems. This study evaluates heavy metal concentrations in surface sediments from six estuarine sites along the
Igbokoda and Igbekebo rivers in Ondo State, Nigeria, employing multivariate statistical methods to identify
contamination sources and spatial patterns. Twenty metals (Ag, Al, As, Ba, Ca, Cr, Cu, Fe, K, Mg, Mn, Na, Ni,
Pb, Se, Th, U, V, Zn) were analysed in 18 sediment samples using ICP-OES after aqua regia digestion. Data
were subjected to correlation analysis, Principal Component Analysis (PCA), and radar fingerprinting to
characterise geochemical signatures. Significant spatial variability was observed, with iron concentrations higher
in Igbokoda sites (1456.79-1665.09 mg/kg) compared to Igbekebo sites (147.57-661.62 mg/kg), while
potassium, magnesium, and sodium showed the opposite pattern, with substantially higher concentrations in
Igbekebo sites. Uranium concentrations ranged from below detection limits to 2.65 mg/kg, whereas thorium
reached maximum levels of 12.65 mg/kg. Strong positive correlations were found between Fe-Mn (r = 0.89),
and among alkali and alkaline earth metals. PCA revealed distinct clustering of sites based on major element
compositions, accounting for 68.4% of total variance. The findings reveal notable geochemical heterogeneity
across the estuarine system, with Igbekebo sites showing potential radiogenic enrichment that warrants further
investigation. This baseline assessment provides vital data for environmental monitoring and risk assessment in
Nigeria’s ecologically sensitive coastal zones.

Heavy metals; Estuarine sediments; Multivariate analysis; Principal component analysis; Environmental contamination; Nigeria

1. Adewuyi, G. O., & Olowu, R. A. (2019). Heavy metal contamination in coastal sediments of Nigeria: A [Google Scholar] [Crossref]

2. review. Environmental Monitoring and Assessment, 191(2), 1-15. https://doi.org/10.1007/s10661-019- [Google Scholar] [Crossref]

3. 7182-4 [Google Scholar] [Crossref]

4. Ali, H., Khan, E., & Ilahi, I. (2022). Environmental chemistry of uranium and thorium: Toxicity, mobility, [Google Scholar] [Crossref]

5. and remediation. Chemosphere, 287, 132145. https://doi.org/10.1016/j.chemosphere.2021.132145 [Google Scholar] [Crossref]

6. Chen, W., Liu, X., & Zhang, Y. (2020). Multivariate analysis of heavy metal contamination in estuarine [Google Scholar] [Crossref]

7. sediments. Marine Pollution Bulletin, 154, 111019. https://doi.org/10.1016/j.marpolbul.2020.111019 [Google Scholar] [Crossref]

8. Kumar, S., Sharma, A., & Singh, K. (2020). Uranium distribution and contamination in groundwater of [Google Scholar] [Crossref]

9. Punjab, India. Environmental Monitoring and Assessment, 192(4), 244. https://doi.org/10.1007/s10661- [Google Scholar] [Crossref]

10. 020-8175-4 [Google Scholar] [Crossref]

11. Liu, R., Wang, M., Chen, W., & Peng, C. (2021). Spatial distribution and pollution evaluation of heavy [Google Scholar] [Crossref]

12. metals in sediments of the Yangtze River estuary. Marine Pollution Bulletin, 163, 111663. [Google Scholar] [Crossref]

13. https://doi.org/10.1016/j.marpolbul.2020.111663 [Google Scholar] [Crossref]

14. Singh, P., Kumar, A., & Prasad, S. M. (2021). Uranium contamination in groundwater: Health risk [Google Scholar] [Crossref]

15. assessment and remediation strategies. Environmental Science and Pollution Research, 28(15), 18915- [Google Scholar] [Crossref]

16. https://doi.org/10.1007/s11356-021-12665-3 [Google Scholar] [Crossref]

17. Thompson, A., Chadwick, O. A., Rancourt, D. G., & Chorover, J. (2020). Iron-oxide crystallinity increases [Google Scholar] [Crossref]

18. during soil redox oscillations. Geochimica et Cosmochimica Acta, 270, 383-398. [Google Scholar] [Crossref]

19. https://doi.org/10.1016/j.gca.2019.12.005 [Google Scholar] [Crossref]

20. Wang, J., Liu, R., & Li, Y. (2020). Sources and ecological risk assessment of heavy metals in estuarine [Google Scholar] [Crossref]

21. sediments. Science of the Total Environment, 713, 136145. [Google Scholar] [Crossref]

22. https://doi.org/10.1016/j.scitotenv.2020.136145 [Google Scholar] [Crossref]

23. WHO. (2012). Uranium in drinking-water: Background document for development of WHO Guidelines [Google Scholar] [Crossref]

24. for Drinking-water Quality. World Health Organization. [Google Scholar] [Crossref]

25. Zhang, L., Xu, Y., & Zhao, J. (2023). Geochemical behavior of heavy metals in estuarine sediments under [Google Scholar] [Crossref]

26. changing environmental conditions. Environmental Chemistry Letters, 21(1), 45-58. [Google Scholar] [Crossref]

27. https://doi.org/10.1007/s10311-022-01456-3 [Google Scholar] [Crossref]

28. Zhou, Q., Zhang, J., & Fu, J. (2021). Sediment quality and heavy metal pollution in coastal zones: A global [Google Scholar] [Crossref]

29. perspective. Environmental Reviews, 29(3), 345-360. https://doi.org/10.1139/er-2020-0045 [Google Scholar] [Crossref]

• Methane Emissions from Municipal Solid Waste - Case Study in Cai Rang District, Can Tho City, Vietnam
• Youth Activism, Intentional Integration of Policies to Raise Awareness on Climate Change Action among the Youth
• Breathing Spaces: Environmental & User Experience in Dhanmondi and Zigatola Multistoried Apartments, Dhaka, Bangladesh
• Effects of Solid Waste Disposal on Soil Quality in Makurdi Metropolis, Benue State, Nigeria
• Environmental Impact of Artisanal and Small-Scale Gold Mining in Borgu Local Government Area