Determination of Total Petroleum Hydrocarbon Levels in Agricultural Soils of Bayelsa State Following Oil Spill Incidents

Recurring oil spill incidents in the Niger Delta continue to devastate agricultural soils, threatening food production and livelihoods of farming communities. This study determines total petroleum hydrocarbon concentrations and assesses associated soil quality degradation in farmland soils of three communities in Bayelsa State affected by pipeline spills reported within the preceding twelve months. Soil samples were collected at three depths from spill-impacted and control plots and extracted by Soxhlet extraction using n-hexane. Total petroleum hydrocarbons were quantified by gravimetry and confirmed by gas chromatography-flame ionisation detection. Concurrent physicochemical analysis included soil pH, total organic carbon, total nitrogen, cation exchange capacity, and available phosphorus. Results show total petroleum hydrocarbon concentrations in spill-affected soils ranging from 4,500 to 27,000 milligrams per kilogram, far exceeding the Department of Petroleum Resources intervention threshold of 50 milligrams per kilogram. Significant reductions in organic nitrogen and available phosphorus in contaminated soils indicate impairment of soil fertility. Correlation analysis revealed a strong negative relationship between total petroleum hydrocarbon levels and crop productivity indices estimated from yield surveys of affected farmers. The study recommends immediate remediation of identified hotspots, compensation for affected farmers, and the operationalisation of the National Oil Spill Detection and Response Agency's remediation protocols. Keywords: total petroleum hydrocarbons, oil spill, Bayelsa State, soil contamination, Niger Delta