Measurements of Physicochemical, Elemental, and Total Petroleum Hydrocarbon Contents as Pollution Indicators of Soils in Petroleum Products Retailing Station Surrounding Areas

Abstract

Soils around petroleum products retailing stations were analyzed for their physicochemical, elemental, and total petroleum hydrocarbon contents with a notion to assess the contamination level of the soils. Samples were collected using standard analytical procedures and the elemental contents of the soils were determined using bulk scientific atomic absorption spectrometry/atomic emission spectrometry techniques, while total petroleum hydrocarbon and physicochemical parameters contents were determined using standard analytical techniques. Ten elements were analyzed and detected and their concentrations, enrichment factors, pollution index, and geoaccumulation index (Igeo) values established. The concentrations of most of the analyzed elements were higher in the oil-contaminated soils than those of other Nigerian soils, while the values of the analyzed physicochemical parameters followed the same trend. The results of the Igeo indicated that the soils were very heavily polluted (6.2–18.0) with all the metal, except V, which was heavily polluted (4.2). Very high enrichment factors and pollution index were obtained for Mn, Zn, K, Cu, Ni, Cr, and Pb. This was corroborated by their values, which were excessive when compared with their tolerable limits. The clustering results indicated that the elements were fairly correlated, indicating chemical affinity and/or similar sources. These were supported by the cross plot results (R2 = 0.5), and the results of Pearson correlation matrices for the elements. Average total petroleum hydrocarbons level (1,233.0 mg/kg) of the soils was high when compared to studies of similar settings. The overall results showed that the soils were highly contaminated and may pose a threat to public health.