HEALTH RISK ASSESSMENT OF HEAVY METAL CONTAMINATION IN EKULU AND NYABA RIVERS, SOUTHEAST NIGERIA
DOI:
https://doi.org/10.5281/zenodo.17233545Keywords:
Heavy metals, Acid Mine Drainage, Ekulu River, Nyaba River, Health risk assessment, Enugu StateAbstract
Heavy metal contamination of surface waters poses serious ecological and human health concerns, particularly in mining-impacted environments. This study evaluated the concentrations, seasonal variations, sources, and health risks of heavy metals in Ekulu and Nyaba rivers, Southeast Nigeria. Both rivers drain the abandoned Onyeama and Okpara coal mines, which continue to discharge Acid Mine Drainage (AMD) into downstream communities. A total of 34 water samples were collected during wet and dry seasons from upstream, midstream, downstream, mine discharge, and control sites. Samples were analyzed for As, Cd, Co, Fe, Hg, Mn, Ni, Pb, and Se using Atomic Absorption Spectrophotometry (AAS), following APHA protocols. The results revealed that Fe, Pb, Cd, and As concentrations consistently exceeded permissible limits set by WHO, USEPA, and FEPA/NESREA standards. Seasonal variations showed higher concentrations in Ekulu River during the dry season due to reduced dilution, while Nyaba River recorded elevated levels in the wet season as rainfall enhanced leaching from abandoned mine tunnels. Correlation analysis confirmed AMD as the dominant contamination source, with additional contributions from irrigation, laundry, effluent disposal, and sand dredging. Human health risk assessment indicated Hazard Quotient (HQ) and Hazard Index (HI) values above 1 for several metals, signifying non-carcinogenic risks, while Incremental Lifetime Cancer Risk (ILCR) values for As, Cd, Ni, and Pb exceeded the acceptable threshold of 1 × 10⁻⁴. Children were found to be more vulnerable than adults across all exposure pathways. The study concludes that Ekulu and Nyaba rivers are unsafe for direct domestic and agricultural use without treatment. It recommends urgent remediation of abandoned mines, continuous water quality monitoring, provision of alternative safe water supplies, stricter regulation of anthropogenic activities, and targeted public health interventions to safeguard local communities
References
Adaikpoh, E. O., Ogala, J. E., & Nwajei, G. E. (2005). Heavy metals concentrations in coal and sediments from River Ekulu in Enugu, coal city of Nigeria. Journal of Applied Sciences and Environmental Management, 9(3), 5–8.
Akpan, A., Tse, A. C., Giadom, F. D., & Adamu, B. (2021). Hydrogeochemical assessment of acid mine drainage in Enugu coalfield, Nigeria. Journal of Environmental Science and Pollution Research, 28(2), 1785–1796.
American Public Health Association (APHA). (2017). Standard methods for the examination of water and wastewater (23rd ed.). APHA.
Armah, F. A., Obiri, S., Yawson, D. O., Pappoe, A. N. M., & Akoto, B. (2010). Assessment of legal framework for small-scale mining in Ghana: A case study of Tarkwa. Resources Policy, 35(1), 29–38.
Balali-Mood, M., Naseri, K., Tahergorabi, Z., Khazdair, M. R., & Sadeghi, M. (2021). Toxicity of heavy metals: Insights into the mechanism of their carcinogenicity. Chemosphere, 263, 127943.
Bigham, J. M., & Cravotta, C. A. (2016). Acid mine drainage, control, and treatment. Applied Geochemistry, 57, 19–31.
Briffa, J., Sinagra, E., & Blundell, R. (2020). Heavy metal pollution in the environment: Sources, toxic effects and remediation. Heliyon, 6(9), e04691.
Chileshe, M. N., Banda, M., Kambole, M. S., & Sakala, G. M. (2021). Human health risk assessment of heavy metals in river systems near abandoned mines in Zambia. Environmental Monitoring and Assessment, 193(11), 741.
Engwa, G. A., Ferdinand, P. U., Nwalo, F. N., & Unachukwu, M. N. (2019). Mechanism and health effects of heavy metal toxicity in humans. Toxicology and Environmental Health Sciences, 11, 201–226.
Federal Environmental Protection Agency (FEPA)/National Environmental Standards and Regulations Enforcement Agency (NESREA). (1991). National Interim Guidelines and Standards for Environmental Pollution Control in Nigeria. Abuja: Federal Government of Nigeria.
Gallagher, D. (2022). Acid mine drainage: Environmental challenges and management strategies. Environmental Reviews, 30(1), 57–73.
Ken-Onukuba, R. I., Okonkwo, C. C., Udeigwe, T. K., & Igboanugo, I. (2021). Water pollution and public health implications in Enugu coal mining district, Nigeria. African Journal of Environmental Science and Technology, 15(6), 222–231.
Nigerian Meteorological Agency (NIMET). (2022). Seasonal rainfall prediction for Nigeria 2022. Abuja: NIMET.
Obasi, N. A., & Akudinobi, B. E. B. (2020). Heavy metal contamination and ecological risk assessment of soils and sediments around Enugu coal mines, Nigeria. Environmental Earth Sciences, 79(3), 1–14.
Obiadi, I. I., Obiadi, C. M., Akudinobi, B. E. B., Mmaduweesi, I. E., & Ezim, O. E. (2016). Enugu coal mines and their environmental impact. International Journal of Environment and Pollution Research, 4(3), 15–31.
Ozoko, D. C. (2015). Environmental impacts of acid mine drainage from coal mines in Nigeria. Journal of Geoscience and Environment Protection, 3(2), 17–27.
Qin, W., Niu, Z., Ye, Q., Li, H., Ma, Y., & Xiang, P. (2021). Health risk assessment of heavy metal exposure in mining-impacted rivers: A review. Science of the Total Environment, 780, 146558.
Rehman, K., Fatima, F., Waheed, I., & Akash, M. S. H. (2018). Prevalence of exposure of heavy metals and their impact on health consequences. Journal of Cellular Biochemistry, 119(1), 157–184.
Singh, A., Wu, J., Zhao, Y., & Wang, J. (2022). Seasonal variation of heavy metals in abandoned mine drainage: Case study of Chinese rivers. Ecotoxicology and Environmental Safety, 238, 113600.
Tchounwou, P. B., Yedjou, C. G., Patlolla, A. K., & Sutton, D. J. (2012). Heavy metals toxicity and the environment. EXS, 101, 133–164.
United States Environmental Protection Agency (USEPA). (2018). Edition of the drinking water standards and health advisories tables. Washington, DC: Office of Water, EPA 822-F-18-001.
World Health Organization (WHO). (2017). Guidelines for drinking-water quality (4th ed.). Geneva: World Health Organization.
Zhao, Y., Wu, P., Li, Y., & Zhang, G. (2020). Long-term impacts of acid mine drainage on water quality and ecological health. Environmental Pollution, 260, 114075.
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