Hydrocarbon Speciation by Fingerprinting Technique and Diagnostic Vanadium/Nickel Ratio of Mgbede-20 Oil-Impacted Site in the Niger Delta Basin of Nigeria

摘要

This article describes the speciation and recognition of the hydrocarbon distribution pattern and the diagnostic ratios of source-specific pristane and phytane for the characterization of the chemical composition and source identification of spilled oil at Mgbede-20 in the Niger Delta Basin of southern Nigeria. Gas chromatography fingerprinting and data interpretation of analyses of oil residues from the site indicated that the released oil was a partially degraded paraffin-base crude oil with fairly well resolved peaks in the n-C_(11) to n-C_(23) range. The chromatograms also contained the acyclic isoprenoids pristane and phytane, at mean concentrations of 8,100 ± 1,700 mg/kg and 24,000 ± 7,300 mg/kg, respectively (without overlap in standard errors at 95% confidence level). The loss of the light end n-alkanes of carbon numbers lower than n -C_(11) indicated that the spilled oil was only slightly weathered after the spill incident and that the chemical composition of the aliphatic components had not undergone significant alteration, suggesting that the on-site spilled oil was relatively fresh. A mean pristane-to-phytane (Pr/Ph) ratio of 0.39 was obtained for replicate spill samples; these Pr/Ph ratios were suggestive of an anoxic-derived source crude oil, with some likely non-waxy, marine-derived organic matter content. The V-to-N; ratios and the distribution of polycyclic aromatic hydrocarbons may serve as a corrective profile for future characterization of the Mgbede-20 oil.