Distribution of polycyclic aromatic hydrocarbons in surface soils and water from the vicinity of Agbabu bitumen field of Southwestern Nigeria

Abstract

Water and soil samples from the vicinity of Agbabu bitumen field of Southwestern Nigeria, were analyzed qualitatively and quantitatively for 10 parent polycyclic aromatic hydrocarbons (PAHs) using gas chromatography coupled by flame ionization detector (GC-FID), in order to gather information on the degree of contamination by bitumen exploration and processing in this area. The total concentrations of 10 PAHs varied from 11.2 to 341.5 μ g L^{− 1} in water and from 101.5 to 209.7 ng g^{− 1} dry weight in soils. The total PAH levels in water samples from all the sampling stations (except at station WB 11), were sufficiently high (> 10 μ g/L) to cause acute toxicity to the exposed organisms. Special PAH compound ratios, such as phenanthrene/anthracene and fluoranthene/pyrene, were calculated to evaluate the relative importance of different origins. The collected data indicate pyrolytic and petrogenic sources. The anthropogenic PAHs, i.e., pyrene and benzanthracene exhibited similar distribution patterns in the studied area, implying that these compounds possess identical sources. Also, dibenzothiophene, a sulfur heterocyclic aromatic compound was determined in this study and it was not detected in all the samples analyzed.

Keywords:

• PAHs
• bitumen
• soil
• water
• GC-FID
• Agbabu
• Southwestern Nigeria

Notes

^a _r_ for 4 d.f. is 0.81 at 95% confidence level. D.f. = Degree of freedom.; N.D., not determined.

^a |r| for 4 d.f. is 0.81 at 95% confidence level. D.f. = Degree of freedom. N.D., not determined.