Spatial Distribution and Hydrogeological Controls On Hydrocarbon Contamination in Groundwater in Ogale, Niger Delta, Nigeria

Groundwater contamination by petroleum hydrocarbons is an environmental concern in the Niger Delta, where oil-related activities threaten groundwater resources used by surrounding communities. This study investigated the spatial distribution of total petroleum hydrocarbons (TPH), polycyclic aromatic hydrocarbons (PAHs), and benzene, toluene, ethylbenzene and xylenes (BTEX) in groundwater in Ogale, Rivers State, Nigeria, and examined their relationships with selected hydrogeological parameters. Fifty-six groundwater sampling locations were assessed using hydrocarbon concentration data, hydraulic-head measurements, hydraulic-conductivity estimates, and geospatial analysis. Descriptive statistics showed substantial spatial variability in contaminant concentrations. TPH ranged from 0 to 1,680,625 µg/L, with a mean of 108,024.36 µg/L and a median of 8,255.50 µg/L. PAHs ranged from 0 to 12,454 µg/L, while BTEX ranged from 0 to 25,469 µg/L. Hydraulic head ranged from 4.640 to 16.120 m, and hydraulic conductivity varied from 1.220 × 10⁻⁸ to 2.610 × 10⁻³ m/s. Spearman’s rank correlation analysis identified a positive association between TPH concentration and depth to water (ρ = 0.301, p = 0.024). No statistically significant associations were observed between the other hydrocarbon groups and the examined hydrogeological parameters. The findings demonstrate heterogeneous groundwater contamination and indicate that depth to water may be associated with TPH distribution. However, the observational design and limited statistical associations do not establish causal transport mechanisms. The study highlights the importance of integrating contaminant mapping with hydrogeological characterisation to guide targeted groundwater monitoring, delineation of contamination, and remediation planning in Ogale.