www.ijird.com April, 2021 Vol10 Issue4 INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH & DEVELOPMENT DOI No. : 10.24940/ijird/2021/v10/i4/APR21024 Page 105 Heavy Metal Contamination of Borehole Water of Selected Settlements in the Coastal Area of Ondo-State, Nigeria 1. Introduction In Nigeria Niger Delta Region, and indeed Nigeria, the problem of water resources is the availability of good- quality (potable) water because of environmental pollution and degradation (Nduka and Orisakwe, 2010); beside this, valuable man-hours and resources are spent traveling long distances fetching water of doubtful quality. The southern part of Ondo State (Southwestern, Nigeria) is characterised by numerous surface water bodies. Groundwater is not common in the area, since the aquifer is very deep and will require huge investment for the more than 400 communities. More than 70% of the area is underlain by various non aquiferous rocks thereby making it a herculean task to sink water boreholes. These factors thereby make the inhabitants to harness the surface water more for their drinking and domestic needs including agricultural activities. Previous studies have shown that water resources in Nigeria are easily contaminated from anthropogenic activities (Efeet.al., 2005). The uncontrolled discharge of untreated effluents into natural receptors by industries in Nigeria has been reported (Atubi, 2011). Since a strong relationship exist between human activities and pollution of the environment, the recognition of this connection and the need to protect human health, recreation, and fisheries production led to the early development of water-quality regulations and monitoring methods (Corvalanet.al., 2005). The rapid urbanization and industrialization of the Niger Delta Region of Nigeria occasioned by huge crude oil and gas reserves has its toll on the environment (Offiong and Cocodia, 2011). The US Department of Energy estimates that since 1960, there has been more than 4,000 oil spills, discharging several million barrels of crude oil into the ponds, ditches, creeks, beaches, ISSN 2278 – 0211 (Online) Dr. O. Terebo Senior Lecturer, Department of Environmental Health, College of Health Technology, Akure, Ondo State, Nigeria Dr. A.A. Soyingbe Senior Lecturer, Department of Environmental Health Sciences, Ogun State College of Health Technology, Ilese, Ogun State, Nigeria Dr. O. Olayinka Associate Professor, Department of Environmental Management & Toxicology, Federal University of Agriculture, Abeokuta, Nigeria O. Bamgbose. Professor, Department of Environmental Management & Toxicology, Federal University of Agriculture, Abeokuta, Nigeria W. O. Abdul Professor, Department of Aquaculture & Fisheries Management, Federal University of Agriculture, Abeokuta, Nigeria Abstract: Heavy metal contamination of the borehole water in the coastal area of Ondo state was assessed by monitoring 264 borehole water samples covering 33 locations divided into four districts (identified as I, II, III & IV) between 2017 and 2019. The metal concentrations of Copper, Lead, Cadmium, Zinc, Chromium, Nickel, Iron, Manganese, Cobalt and Vanadiumwere determined using standard methods. The metal concentrations were within WHO limits except for Pb (0.21 mg/L) in District III. Seasonal variation in mean concentration of heavy metals were; Zinc (0.03±0.01, 0.03±0.04mg/L), Chromium (0.01±0.00, 0.01±0.01 mg/L), Iron (0.58±0.07, 0.12±0.15mg/L), Cadmium (0.003±0.00, 0.01±0.01), Nickel (0.003±0.00, 0.004±0.01mg/L), Manganese (0.02±0.01, 0.03±0.01mg/L), Copper (0.02±0.00, 0.03±0.01mg/L), Lead (0.01±0.00, 0.003±0.01mg/L), Cobalt (0.004±0.00, 0.002±0.01mg/L) and Vanadium (0.003±0.00, 0.03±0.01 mg/L) for rainy and dry seasons respectively. There was significant difference (p<0.05) for Cr, Fe, Cd,Cu and Co, with no significant difference p<0.05) observed for Zn, Ni, Mn and V between seasons. The results obtained from this study suggest no significant risk to this population given the toxicity of these metals with exception of lead in district III. Keywords: AAS, borehole water, heavy metals, maximum contamination level and WHO