Metal fractionation in the soils around a refined petroleum products depot

Abstract

Elemental composition and heavy metal speciation of the soils of Ejigbo oil depot, Lagos state, Nigeria were determined to assess the contamination status of the study area. Oil-impacted and control soils were collected from the oil depot and uncontaminated areas respectively. Pb, Cu, Zn, Cd, Cr, Ni, As, and Fe concentrations in the soils were determined using Atomic absorption spectrometry. Contamination factor (CF) and geo-accumulation index were used to determine the contamination/pollution status of the study area. Geo-accumulation index results indicated that the test soils fall into the unpolluted category (<0) for Cd, Fe, Pb, As, and Zn, while there was unpolluted to moderate pollution (between 0 and 1) for Cu, Ni, and Cr. CF results suggested that the oil depot was contaminated with all the analyzed metals as the CFs were >1. Inter-element clustering equally existed between the analyzed metals. Speciation analysis results showed relatively high bioavailability and mobility potential for Cd and Zn. The study concluded that the soil of the oil depot, whose elemental concentrations exceeded those of the control soils, was impacted with the analyzed metals. Remediation schemes should be developed to clean up the metal in the oil depot soil.