Assessing Anthropogenic Influence and Heavy Metal Contamination in The Ona River Using Pollution and Risk Indices

Abstract: Surface water contamination by heavy metals poses significant ecological and public health challenges, particularly in rapidly urbanizing regions of developing nations. This study assessed the concentration, distribution, and associated ecological and health risks of potentially toxic elements in the Ona River, located within the Adeoyo region of Ibadan, Oyo State, Nigeria. Water samples were collected from three georeferenced sites and analyzed for Fe, Zn, Cu, Cr, As, Cd, Ni, Mn, and Mg using Atomic Absorption Spectrophotometry (AAS) following APHA (2022) standard protocols. Contamination indices including the Geo-accumulation Index (Igeo), Enrichment Factor (EF), Contamination Factor (CF), Pollution Load Index (PLI), and Ecological Risk Index (ERI) were employed to evaluate pollution intensity, while non-carcinogenic and carcinogenic health risks were computed using the United States Environmental Protection Agency (USEPA) model. Results revealed that Cr, Cd, As, Pb, and Fe concentrations were within permissible limits of WHO (2022) and Nigerian Standards for Drinking Water Quality (NSDWQ, 2015). In contrast, Ni and Mn exceeded recommended thresholds, indicating localized anthropogenic inputs, primarily from industrial and urban effluents. Nickel exhibited the highest CF (2.86–3.86) and EF (1735.29–3748.24), denoting considerable contamination and extreme enrichment, while PLI values below 1 suggested overall unpolluted status. The ERI values (15.87–21.78) indicated low ecological risk; however, Ni emerged as the most significant contributor to potential toxicity. Although the Hazard Index (HI < 1) implied minimal immediate health effects, long-term exposure may pose latent risks. The study concludes that while the Ona River water remains largely unpolluted, elevated Ni and Mn levels necessitate continuous monitoring, stricter effluent regulation, and sustainable watershed management to protect aquatic ecosystems and public health.

Heavy metals, Ona River, Water quality, Contamination indices, Ecological risk, Public health

1. Adedeji, O. H., Olayinka, O. O., and Oketola, A. A. (2023). Hydrogeochemical assessment and ecological risk evaluation of heavy metals in surface water from an urban river system in southwestern Nigeria. Environmental Science and Pollution Research, 30(12), 34567–34582. https://doi.org/10.1007/s11356-023-25710-4 [Google Scholar] [Crossref]

2. Adeyemi, O. S., Akinola, M. O., and Ede, A. N. (2024). Assessment of trace metal distribution and ecological risks in sediments and water from a tropical river system in southwestern Nigeria. Environmental Monitoring and Assessment, 196(5), 512. https://doi.org/10.1007/s10661-024-12784-z. [Google Scholar] [Crossref]

3. Ali, H., Khan, E., & Ilahi, I. (2023). Comprehensive assessment of heavy metal contamination and pollution indices in riverine sediments: Spatial and ecological implications. Environmental Monitoring and Assessment, 195(2), 210–224. https://doi.org/10.1007/s10661-023-11765-0. [Google Scholar] [Crossref]

4. American Public Health Association (APHA), American Water Works Association (AWWA), and Water Environment Federation (WEF). (2022). Standard Methods for the Examination of Water and Wastewater (24th ed.). APHA. [Google Scholar] [Crossref]

5. Amoo, A.O., Zakari, A.W., Ijanu, E.M., Adeleye, A.O. and Amoo, N.B. (2017). Physicochemical and Bacteriological Assessment of Surface Water Quality: A case study of Jakara River, North-western Nigeria. International Journal of Applied Research and Technology. 6 (9):65-74. [Google Scholar] [Crossref]

6. Anthony, E.; Emmanuel, D.S.; Jamel, S.; Emmanuel, C.A. (2022). Hydrogeochemical characteristics, sources and human health risk assessment of heavy metal dispersion in the mine pit water–surface water–groundwater system in the largest manganese mine in Ghana. Environmental Technology & Innovation. 2022, 26:1-21. [Google Scholar] [Crossref]

7. Asare-Donkor, N.K.; Boadu, T.A.; Adimado, A.A. (2016). Evaluation of groundwater and surface water quality and human risk assessment for trace metals in human settlements around the Bosomtwe Crater lake in Ghana. SpringerPlus,：5 (1), 1–19. [Google Scholar] [Crossref]

8. Bardi Juliet I, Bawo SS Docas, Oyedeji Ayodele, Bardi Stephen I, Koplamma N Bala (2025). Analysis of Heavy Metal Concentration of Surface Water Around Gas-flaring Stations in Selected Areas of Delta State, Nigeria. Open Journal of Environmental Biology. 2025;10(1):029-036. Available from: 10.17352/ojeb.000048 [Google Scholar] [Crossref]

9. Bessa A.Z. Ekoa, Spatial variation, ecological risk, and point sources of Environmental Trace Metals in lacustrine ecosystems: an assessment of natural and urban Inputs, Soil Sediment. [Google Scholar] [Crossref]

10. Chen, W., Li, Z., Wang, J., & Xu, Y. (2023). Ecological risk assessment of heavy metals in urban river sediments using integrated pollution indices and risk modeling. Environmental Research, 232, 116345. https://doi.org/10.1016/j.envres.2023.116345. [Google Scholar] [Crossref]

11. Çiner, F.; Sunkari, E.D.; Şenbaş, B.A. (2021). Geochemical and multivariate statistical evaluation of trace elements in groundwater of Niğde municipality, south-central Turkey: implications for arsenic contamination and human health risks assessment. Arch. Environ Contam. Toxicol,：80 (1), 164–182. [Google Scholar] [Crossref]

12. Demissie, S., et al. “Assessing Acute and Chronic Risks of Human Exposure to Arsenic.” Environmental Health Insights, vol. 18, 2024, pp. 1-12. DOI: 10.1177/11786302241257365. [Google Scholar] [Crossref]

13. Hussain, R.; Wei, C.; Luo, K. (2019). Hydrogeochemical characteristics, source identification and health risks of surface water and groundwater in mining and non-mining areas of Handan, China. Environ. Earth Sci.：78 (14), 1–23. [Google Scholar] [Crossref]

14. Iroha, I. R., Ude, I. U., Okoronkwo, C., Kenneth, O., Okafor, C. O. O., and Akuma, S. O. (2020). Comparative Assessment of Physicochemical Characteristics, Metal Levels and Anion Contents of Water from Different Aquatic Environments in Ebonyi State. Biomed J. Sci. & Tech Res. 29 (5): 22834-22865. [Google Scholar] [Crossref]

15. Islam M, Ahmed M, Raknuzzaman M, et al. (2015). Heavy metal pollution in surface water and sediment: a preliminary assessment of an urban river in a developing country. Ecol Indic ;48:282–291. doi: 10.1016/j.ecolind.2014.08.016. [Google Scholar] [Crossref]

16. Islam, M. S., Ahmed, M. K., Raknuzzaman, M., Habibullah-Al-Mamun, M., and Masunaga, S. (2023). Geo-accumulation and ecological risk assessment of heavy metals in river sediments: A case study from South Asia. Environmental Science and Pollution Research, 30(12), 34921–34935. https://doi.org/10.1007/s11356-023-26210-2. [Google Scholar] [Crossref]

17. Kahal A, El-Sorogy AS, Qaysi S, Almadani S, Kassem OM, Al-Dossari A. (2020). Contamination and ecological risk assessment of the Red Sea coastal sediments, southwest Saudi Arabia. Marine Pollution Bulletin; 154:111125. [Google Scholar] [Crossref]

18. Khan MB, Dai X, Ni Q, Zhang C, Cui X, Lu M, et al. (2019). Toxic Metal Pollution and Ecological Risk Assessment in Sediments of Water Reservoirs in Southeast China. Soil and Sediment Contamination: An International Journal;28:695-715. [Google Scholar] [Crossref]

19. Liu P, Hu W, Tian K, Huang B, Zhao Y, Wang X, et al. (2020). Accumulation and ecological risk of heavy metals in soils along the coastal areas of the Bohai Sea and the Yellow Sea: A comparative study of China and South Korea. Environment International;137:105519. [Google Scholar] [Crossref]

20. Loska, K., and Wiechuła, D. (2003). Application of principal component analysis for the estimation of source of heavy metal contamination in surface sediments from the Rybnik Reservoir. Chemosphere, 51(8), 723–733. https://doi.org/10.1016/S0045-6535(03)00187-5 [Google Scholar] [Crossref]

21. Müller, G. (1969). Index of geoaccumulation in sediments of the Rhine River. Geojournal, 2(3), 108–118. https://doi.org/10.1007/BF02986851 [Google Scholar] [Crossref]

22. Nour HE, El-Sorogy AS, AbdEl-Wahab M, Mohamaden M, Al-Kahtany K. (2019) Contamination and ecological risk assessment of heavy metals pollution from the Shalateen coastal sediments, Red Sea, Egypt. Marine pollution bulletin;144:167-72. [Google Scholar] [Crossref]

23. Obunwo, C. C. and Opurum, J. J. (2013). Evaluation and comparison of water quality parameter from fresh water surface stream and hand-dug wells in Isiokpo Community, River state, Nigeria. Journal of Natural Science, 3 (13): 42 – 45. [Google Scholar] [Crossref]

24. Odeyemi, A. T. and Agunbiade, R. O. (2012). Bacteriological and Metal Analyses of Water Samples from Awotunde Fish Pond and River. Scientific Journal of Microbiology, 1 (2): 48-54. [Google Scholar] [Crossref]

25. Olabamiji, A. O., Alausa, S. K., Adejumobi, C. A., & Alabi, T. A. (2023). Environmental Impact Assessment of Radionuclide and Metal Contamination in Heavily Urbanized River, Ibadan, Nigeria. Nigerian Journal of Physics, 32(1), 160–168. Retrieved from https://njp.nipngr.org/index.php/njp/article/view/6. [Google Scholar] [Crossref]

26. Pan, Z., et al. (2024). Heavy metal exposure and cardiovascular disease: mechanisms and epidemiology. Circulation Research, 135(3), 312–330. [Google Scholar] [Crossref]

27. Rahman, M. A., Hasan, M. R., and Alam, M. S. (2024). Assessment of heavy metal contamination and ecological risk in surface waters: An integrated approach using pollution indices. Environmental Monitoring and Assessment, 196(4), 245–258. https://doi.org/10.1007/s10661-024-12345-6. [Google Scholar] [Crossref]

28. Rahman, M. A., Sultana, N., Chowdhury, M. T. H., and Ahmed, F. (2024). Assessment of heavy metal contamination and associated health risks in groundwater used for drinking and irrigation in industrial areas. Environmental Monitoring and Assessment, 196(3), 245. https://doi.org/10.1007/s10661-024-12645-9 [Google Scholar] [Crossref]

29. Sazakli, E., et al. (2024). Human health effects of oral exposure to chromium: A systematic review. Environmental Research, 248, 118567. [Google Scholar] [Crossref]

30. Shallom, N. C., Obinna, C. W., Adetayo, Y. O. and Vivienne, N. E. (2011). Assessment of water quality in Canaanland, Ota, Southwestern Nigeria. Agriculture and Biology Journal of North America 2(4): 577-583. [Google Scholar] [Crossref]

31. Singh, A., Sharma, R. K., and Tiwari, S. (2022). Geo-accumulation index-based evaluation of heavy metal contamination in aquatic sediments: A review of global studies. Environmental Nanotechnology, Monitoring & Management, 18, 100715. https://doi.org/10.1016/j.enmm.2022.100715. [Google Scholar] [Crossref]

32. Standard Organization of Nigeria (SON). (2015). Nigerian Standard for Drinking Water Quality (NSDWQ): Nigerian Industrial Standard NIS 554:2015. Lagos, Nigeria: SON. [Google Scholar] [Crossref]

33. Tajudeen Yahaya, Lawal Nana Aisha1, Abdulrahman Sani Kalgo, Nasiru Muhammad, Muhammad-Jamil Abubakar, Mohammed Umar Faruk (2024). Contamination and risk assessment of heavy metals in water and fish obtained in Bunza River in Kebbi State, Nigeria. Environmental Health Engineering and Management Journal 2024, 11(2), 191-199. [Google Scholar] [Crossref]

34. U.S. Environmental Protection Agency (USEPA). (1989). Risk Assessment Guidance for Superfund: Volume I – Human Health Evaluation Manual (Part A). EPA/540/1-89/002. [Google Scholar] [Crossref]

35. Ustaoğlu F, and Islam MS (2020). Potential toxic elements in sediment of some rivers at Giresun, Northeast Turkey: A preliminary assessment for ecotoxicological status and health risk. Ecological Indicators; 113:106237. [Google Scholar] [Crossref]

36. WHO, Quality Guidelines for Drinking Water - 2nd Edition Hygiene Criteria and Supporting Documentation Drinking Water Standards Water Quality Standards Guideline, 2000. ISBN 924 2544809 (NLM Classification WA 675). [Google Scholar] [Crossref]

37. World Health Organization (WHO). (2022). Guidelines for drinking-water quality: Fourth edition, incorporating the first addendum. Geneva: World Health Organization. https://www.who.int/publications/i/item/9789240045069 [Google Scholar] [Crossref]

38. World Health Organization (WHO). (2023). Guidelines for drinking-water quality: Fourth edition incorporating the first and second addenda. Geneva: World Health Organization. https://www.who.int/publications/i/item/9789240077237 [Google Scholar] [Crossref]

39. World Health Organization. Arsenic. Fact sheet, 2 September 2022. Geneva: WHO. Available at: https://www.who.int/news-room/fact-sheets/detail/arsenic. World Health Organization [Google Scholar] [Crossref]

40. Zhang C, Shan B, Tang W, Wang C, Zhang L. (2019). Identifying sediment associated toxicity in rivers affected by multiple pollutants from the contaminant bioavailability. Ecotoxicology and Environmental Safety; 171:84-91. [Google Scholar] [Crossref]

41. Zhang, Y., Chen, J., Wang, X., & Liu, L. (2024). Assessment of heavy metal contamination and ecological risk in urban river sediments using pollution indices and multivariate analysis. Environmental Science and Pollution Research, 31(9), 13245–13260. https://doi.org/10.1007/s11356-024-29751-8. [Google Scholar] [Crossref]

42. Zhu G, Noman MA, Narale DD, Feng W, Pujari L, Sun J. (2020). Evaluation of ecosystem health and potential human health hazards in the Hangzhou Bay and Qiantang Estuary region through multiple assessment approaches.Environmental Pollution;114791. [Google Scholar] [Crossref]

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