Petroleum Hydrocarbon, Heavy-Metal, And Microbial Contamination Of Shallow Groundwater In The Gbaramatu Kingdom, Niger Delta: Geospatial Evidence And Public Health Risk Implications

Abstract

The communities most closely affected by petroleum-exploration infrastructure are at a higher risk of groundwater contamination than others, and that risk is not always expressed in measurable public-health risk. This study assesses the contamination of shallow groundwater samples in three communities of Okerenkoko, Kurutie and Kunukunuma of the Gbaramatu Kingdom in Warri, South-West local government area of Delta State and uses a screening-level human-health risk assessment and geospatial hotspot mapping. Lead (0.039–0.764 mg/L), cadmium (0.014-0.172 mg/L), and arsenic (0.157-0.185 mg/L) exceeded WHO (2022) limits at multiple sites, alongside total petroleum hydrocarbons (0.041-0.052 mg/L, exceeding the 0.01 mg/L threshold at every location) and polycyclic aromatic hydrocarbons (0.014-0.025 mg/L, exceeding the 0.0007 mg/L guideline by up to 36-fold). E. coli was present in 28 of 30 samples showing concentrations up to 5.9 × 10⁴cfu/mL which exceeded the WHO permissible limit. A screening-level Hazard Index calculation using the standard USEPA oral reference doses (ORDs) resulted in HI values of approximately 26.8 (adult) and 102.4 (child), well above the USEPA non-carcinogenic risk threshold of 1.0 with arsenic and cadmium as the most significant contributors. Persistent contamination hotspots were mapped using geospatial interpolation, with the same regions observed associated with the hydrocarbon, heavy-metal and microbial data sets, implying spatial coincidence in contamination hotspots and suggesting that contamination is from one rather than multiple sources. These findings document a measurable failure to meet United Nations Sustainable Development Goal 6 (clean water and sanitation) and carry direct implications for SDG 3 (health and wellbeing), and they support regionally coordinated regulatory intervention, coordinated between Nigeria's Ministry of Water Resources, NESREA, and NOSDRA, rather than community-by-community remediation.