Evaluation of hydrocarbon and co-contaminants in groundwater and associated public health risks using electrical resistivity and hydrochemical data

Abstract

Hydrocarbon plays a vital role in national and global economic development. However, the environmental impact of hydrocarbon extraction and utilization remains a challenging phenomenon, which has recorded a far worse impact on the soil, groundwater, and public health. This study applied resistivity and hydrochemical data to provide information about the distribution of potential hydrocarbon contaminants (HCCs) and co-contaminants such as heavy metals (HMs) in groundwater near a refinery and the possible associated health risks for effective environmental management and public health protection. The concentrations of HCCs and variations in electrical resistivity values were examined. The regional aquifer vulnerability to the HCCS was evaluated. Based on the study's outcomes, HCCs occur in the overburdened topsoil at depths of 0.0 m–3.5 m, with electrical resistivity values varying between 15,000 Ωm and 60,000 Ωm. These values exceeded the known subsurface resistivity values of the region as a result of the presence of HCCs. Hydrochemical data records indicate high concentrations of HCCs in groundwater ranging from 0.342 mg/L – 0.572 mg/L. The level of total petroleum hydrocarbons (TPH) in groundwater from five hand-dug wells (HDWs): HDW 1 (0.4721), HDW 2 (0.4517), HDW 3 (highest at 0.5716), HDW 4 (0.4012), and HDW 5 (lowest at 0.3421), over the Directorate of Petroleum Resources (DPR). The aquifer of the region was polluted with HMs owing to infiltrated HCCs in different range, i.e., 0.792–1.692 mg/L for zinc, 0.909–1.711 for iron, 0.711–1.612 mg/L for lead, 0.333–0.717 mg/L for chromium, and 0.038–0.081 mg/L for cadmium, and pH ranged from 5.3 to 7.1 and electrical conductivity (EC) from 0.524 to 0.777 mS/cm, corresponding to the elevated electrical resistivity contrast caused by HCCs. Data analysis provides a comprehensive understanding of the environmental impacts of hydrocarbons and HMs, demonstrating how petrochemical industrial activities infiltrate into groundwater systems, exacerbating environmental degradation and posing serious health threats to human beings.