Analysis of Petroleum Hydrocarbon Contamination in Surface Soils around a Petroleum Storage Depot in Port Harcourt, Rivers State

Petroleum storage depots located within urban areas of Rivers State, South South Nigeria, pose persistent contamination risks to surrounding soils and shallow groundwater. This study analyses total petroleum hydrocarbon concentrations and polycyclic aromatic hydrocarbon profiles in surface soils collected from four transects extending radially from a major petroleum storage depot in Port Harcourt at distances of 0, 50, 100, and 200 metres. Fifteen composite soil samples were collected at 0 to 30 cm depth, extracted using Soxhlet extraction, and analysed by gas chromatography-flame ionisation detection and gas chromatography-mass spectrometry. Total petroleum hydrocarbon concentrations at the depot perimeter averaged 18,430 mg/kg, declining to 2,150 mg/kg at 200 metres, all substantially above the Department of Petroleum Resources remediation target of 50 mg/kg for residential land use. Naphthalene, phenanthrene, and benzo(a)pyrene were the dominant polycyclic aromatic hydrocarbon congeners detected. Spatial distribution analysis confirmed hydrocarbon plume extension predominantly in the downwind direction. Soil physico-chemical parameters, including organic matter content and texture, influenced contaminant distribution. The study establishes a contamination baseline for this depot site, provides evidence for regulatory enforcement, and recommends bioremediation feasibility studies for impacted zones in Port Harcourt. Keywords: petroleum hydrocarbons, soil contamination, PAH, Port Harcourt, depot