Abstract

The concentration, distribution profile and possible sources of n-alkanes and polycyclic aromatic hydrocarbons in the soil of oil sand deposits in Ondo Southwest Nigeria were investigated to determine the present level of contamination prior to exploitation of the oil sand deposits. Surface soil samples (0-15 cm) were collected from Ilubinrin, Agbabu and Oloda communities. The level and distribution of polyaromatic hydrocarbons and n-alkanes in the soil samples were analyzed using gas chromatography coupled with a flame ionization detector. The mean concentrations of polycyclic aromatic hydrocarbons (PAHs) in the soil of Agbabu, Ilubinrin, and Oloda were 36.07±1.61, 16.09±0.76 and 10.04±0.55 ìg/kg and the mean concentrations of identified, resolved n-alkanes were 14.03±0.55, 22.38±0.99 and 30.37±1.20 mg/kg, respectively. The odd-numbered alkanes were dominant in Agbabu and Ilubinrin, while the even numbered alkanes are dominant in Oloda. The distribution of total combustion specific PAHs was higher in most of the area than the non-combustion specific PAHs and the highest percentage of total carcinogenic PAHs was 28, 33 and 45% in Oloda, Ilubinrin, and Agbabu, respectively. The studied area was not polluted with PAHs, but there was evidence of PAH's accumulation in the soil. Various n-alkanes and PAHs ratios were obtained to identify the possible sources of PAHs and n-alkanes. Mixed sources of pyrogenic and petrogenic PAHs were discovered with predominant pyrolytic sources due to combustion of wood, biomass, and bitumen seepage.

Key words: Polycyclic aromatic hydrocarbons, oil sand, diagnostic ratio, aliphatic hydrocarbons, bitumen.