Evaluation of Polycyclic Aromatic Hydrocarbons and Total Petroleum Hydrocarbons Profiles in Some Nigerian Crude Oils

Abstract

Aim: To evaluate the concentrations of Polycyclic Aromatic Hydrocarbons and Total Petroleum Hydrocarbons in some Nigerian crude oils. Study Design: Field and Laboratory-Experimental Design were used in this study. Place and Duration of Study: Crude oil samples were obtained from three locations (designated as Location 1, Location 2, and Location 3) in the Niger Delta, Nigeria. Methodology: The samples were subjected to liquid-liquid extraction using dichloromethane and analysed using GC-FID. Results: The results of the analyses of the crude oils gave polycyclic aromatic hydrocarbons (PAHs) concentrations of 2.6089 x 104 ppm representing 60.06% and total petroleum hydrocarbon (TPH) concentration of 4.3201 x 104 ppm at Location 1, PAHs concentration of 4.764 x 103 ppm (62.8%) and TPH recording a concentration of 7.583x 103 ppm at Location 2, while Location 3 had PAHs concentration of 9.93 x 102 ppm (30.66%) and TPH concentration of 3.239 x 103 ppm. The total concentrations of the high molecular weight PAHs were lower than those of the low molecular weight PAHs in the samples. Also the concentrations of the individual PAHs were higher in the low molecular weight PAHs. The mean PAHs concentrations of 2707.6 ppm (location 1), 551.5 ppm (location 2) and 90.7 ppm (location 3) are different. Conclusion: The observed  results show that all the sixteen polycyclic aromatic hydrocarbons listed as priority pollutants are present in the three crude oil samples with higher concentrations in the light crude oils than in the heavy crude oil and a strong correlation with the total petroleum hydrocarbon concentration. It was also observed that though the ratios of the low molecular weight PAHs to high molecular weight PAHs of the crude oils indicate petrogenic, the unique diagnostic ratios suggest pyrogenic input. There is therefore the need to develop a method of PAHs removal from PAHs contaminated water based on locally available and cheap materials.