Environmental Risk Assessment of Soil and Groundwater in Ajokpori Ogale, Eleme LGA, Rivers State, Nigeria: Application of Geoaccumulation and Water Quality Indices

The increasing prevalence of hydrocarbon contamination in the Niger Delta necessitates robust, science-based environmental risk assessments to guide remediation and public health interventions. This study presents a comprehensive baseline evaluation of soil and groundwater quality in Ajokpori Ogale, Eleme LGA, Rivers State, Nigeria, using a multi-index approach to assess pollution levels and ecological risks. A total of six soil samples (SS8T, SS8B, SS16T, SS16B, SS23T, SS23B) and one groundwater sample were analyzed for physicochemical parameters, heavy metals, hydrocarbons, and microbial content. The data were interpreted using contamination indices including the Geoaccumulation Index (Igeo), Enrichment Factor (EF), Contamination Factor (CF), Pollution Load Index (PLI), and Potential Ecological Risk Index (RI), alongside the Water Quality Index (WQI) for groundwater. Results revealed acidic conditions in both soil (pH 4.98–5.96) and groundwater (pH 4.72), with elevated Total Petroleum Hydrocarbons (TPH) at SS23T (1.817 mg/kg) indicating a localized contamination hotspot. Cadmium (Cd) showed significant anthropogenic enrichment (EF > 10) at SS23T and SS8T, with Igeo values of 0.18 and –0.28, respectively, classifying the site as “uncontaminated to moderately contaminated.” The PLI values (0.09–0.41) indicated low overall pollution load, while the RI was highest at SS23T (35.23), driven by Cd’s high toxicity factor. Groundwater analysis revealed excellent quality (WQI = 7.20), with all parameters within WHO and NIS 554:2015 limits except pH. The absence of detectable BTEX and PAHs suggests either effective natural attenuation or levels below detection limits. The integration of geochemical and hydrological indices provided a robust framework for risk characterization, confirming that while the site currently poses low ecological risk, localized contamination with Cd and hydrocarbons warrants long-term monitoring. This study underscores the utility of multi-index approaches in environmental assessment and provides critical baseline data for future remediation planning in oil-impacted tropical environments.