GEOCHEMICAL EVALUATION AND RISK ASSESMENT OF SOIL: A CASE STUDY OF MOSOGAR COMMUNITY

ABSTRACT This study evaluated the geochemical characteristics and human health risks from Potentially Toxic Elements (PTEs) and Total Petroleum Hydrocarbons (TPH) in soil and water within Mosogar, a community in Nigeria's Niger Delta impacted by chronic oil spills and pipeline vandalism. Soil and water samples from residential, agricultural, and industrial zones were analyzed using Atomic Absorption Spectrometry and Gas Chromatography. The soil was slightly acidic to neutral (mean pH 6.62). Geochemical indices, including the Geo-accumulation Index (Igeo) and Pollution Load Index (PLI), were calculated, and human health risks were assessed using a US EPA model. Results indicate that while Iron (Fe), Chromium (Cr), and Nickel (Ni) concentrations were below Nigerian regulatory limits, the mean Cadmium (Cd) concentration was 1.254 mg/kg, exceeding the Nigerian permissible limit (0.8 mg/kg) by 57%. A maximum Cd concentration of 1.875 mg/kg was found at a specific hotspot. TPH concentrations also significantly exceeded national safety limits. Geochemical indices confirmed high anthropogenic contamination, primarily driven by Cadmium, which exhibited a Contamination Factor (CF) of 4.18 and a mean Igeo of 2.0, classifying it as moderately to heavily contaminated. The PLI was >1 at seven of eight sites, identifying specific locations as pollution hotspots. The Ecological Risk Factor (Er) for Cd was 125.4, indicating considerable ecological risk from this single element. The Total Potential Ecological Risk Index (RI) for the area was 134.49, signifying a moderate overall ecological risk. The human health risk assessment suggests the elevated Cd levels pose a potential non-carcinogenic health risk (Hazard Quotient >1) via the ingestion pathway, particularly for children. The findings confirm that persistent oil-related pollution, characterized by severe Cadmium contamination, poses significant ecological and public health risks in Mosogar, necessitating urgent remediation, stricter regulatory oversight, and the provision of alternative safe drinking water.