EVALUATION OF HEAVY METAL POLLUTION IN SOILS OF OIL EXPLORATION HOST COMMUNITIES UTILISING INDIGENOUS EARTHWORMS AS BIOINDICATORS

This study assessed the risk of heavy metal pollution in soils of oil extraction host communities by utilising indigenous earthworms as bioindicators. Soil and earthworm samples at a depth of 0-20 cm were obtained from the same quadrant across five coastal wetlands in Delta State. Fifty samples were gathered from the research region. Concentrations of specific heavy metals were assessed via Atomic Absorption Spectroscopy (Solaar 969 Unicam Series Model). The average concentrations of heavy metals and total hydrocarbon content in soils were 217.741±130.42 (Fe), 5.997±6.33 (Cr), 0.275±0.13 (Cd), 4.732±3.00 (Cu), 34.729±33.37 (Zn), 23.298±19.19 (Mn), 10.856±2.90 (Pb), and 17694.98±47114.37 (THC). The enrichment factor (EF) indicates substantial enrichment of Fe, Cr, and Mn, considerable enrichment of Cd, Cu, and Zn, and exceedingly high enrichment of Pb. The geoaccumulation index (Igeo) reveals that Fe is moderately contaminated, Cr is moderately to heavily polluted, Cd and Cu are heavily to extremely polluted, while Pb demonstrates extreme pollution. The contamination factor (CF) indicates a significantly elevated presence of Fe, Cr, Zn, and Mn, while Cd, Cu, and Pb also demonstrate substantial contamination. All sample locations exhibit a significantly elevated level of contamination (CD > 24 = very high degree of contamination). According to Tomlinson et al. (1980), the PLI value for the studied soils demonstrates PLI > 1. The indexes of potential ecological danger were arranged in the following order: EiRCd, EiRPb, EiRCu, EiRZn, EiRCr, EiRMn. Cadmium was the primary factor contributing to the potential ecological danger, as all sampling locations exhibit significant ecological risk to the environment. The bioaccumulation factor (BAF) indicated that the earthworm samples accumulated chromium (Cr), cadmium (Cd), copper (Cu), and zinc (Zn), as BAF values exceeding 1 signify metal bioaccumulation. It is necessary to evaluate the heavy metal concentrations of Cd, Cu, Zn, and Pb in the adjacent vegetation. It is essential to implement suitable engineering and ecological strategies to regulate soil heavy metal concentrations, alongside conducting ecological restoration in contaminated areas. This underscores the necessity of adhering to the recommendations outlined in the United Nations Environment Program’s 2011 environmental assessment report and the 2030 Agenda for Sustainable Development Goals (SDGs) regarding the remediation of oil spills in Delta State, as the survival of human life and other biotic elements in this region is at risk.