Assessment of Soil Contamination from Petroleum Product Storage Facilities in Warri, Delta State

This study assesses soil contamination by petroleum hydrocarbons in the vicinity of petroleum product storage and depot facilities in Warri, Delta State, South South Nigeria. Warri hosts numerous petroleum product bulk storage depots and retail stations, and historical spills, tank leakages, and overfills from these facilities have contributed to soil contamination with total petroleum hydrocarbons, polycyclic aromatic hydrocarbons, and benzene, toluene, ethylbenzene, and xylene compounds. Soil samples were collected at depths of zero to thirty centimetres and thirty to sixty centimetres from thirty-six sampling points situated at four major depot facilities and six petrol filling stations at varying radial distances from primary source locations. Samples were analysed for total petroleum hydrocarbons using gas chromatography-flame ionisation detection, and selected samples were further analysed for individual polycyclic aromatic hydrocarbons. Results show total petroleum hydrocarbon concentrations ranging from 180 to 42,000 milligrams per kilogram, with highest values directly adjacent to depot tank berms and underground tank vent pipes at petrol stations. Benzene, toluene, ethylbenzene, and xylene compounds are detected at concentrations above risk-based screening levels at seven petrol station sites. Polycyclic aromatic hydrocarbon contamination is concentrated in the upper horizon at depot sites. Seasonal data indicate persistent contamination without natural attenuation within the sampling timeframe. The study recommends soil remediation by excavation and off-site treatment at highly contaminated locations and enhanced leak detection systems at depot facilities. Keywords: petroleum contamination, soil quality, total petroleum hydrocarbons, Warri, remediation.