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Polycyclic aromatic hydrocarbons and polychlorinated biphenyls were investigated in sediment of bitumen deposit impacted area of Agbabu, Nigeria, to determine the present level of contamination with these toxic compounds prior to exploitation. Samples were collected during the dry season (March) and the wet season (August) of year 2008. Analysis was carried out with gas chromatography using mass spectrometry detector for polycyclic aromatic hydrocarbons and flame ionization detector for polychlorinated biphenyls. In the dry season sum of concentration of PAHs ranged from zero to 0.12 ± 0.06 ppm, while in the wet season the minimum was 0.18 ± 0.07 ppm and the maximum was 1.04 ± 0.16 ppm. Most of these values were higher than sum of polycyclic aromatic hydrocarbons concentrations of 1 -10 µg/kg indicating that they were likely to come from anthropogenic sources. Average concentrations of PAHs such as naphthalene and benzo (a) pyrene obtained in sediment in the wet season in some of the stations were higher than recommended limits. The linear regression analysis between sum of concentrations and percentage organic carbon showed no significant correlation in sediment in the dry season (r 2 = 0.0025) and in the wet season (r 2 = 0.1345). The predominance of 4-6 ringed polycyclic aromatic hydrocarbons and the ratios between pairs of individual polycyclic aromatic hydrocarbons showed that they are likely to have come from pyrolytic sources. No polychlorinated biphenyl congener was detected in the samples.

Ground water of the farm settlements in the bitumen deposit area of Western Nigeria were tested for pH, conductivity, turbidity, total dissolved solid, sulphate, phosphate, nitrogen nitrate, chloride, alkalinity, total hardness, calcium, magnesium, sodium, potassium and total coliform in the dry season (March) and rainy season (August) of years 2008 and 2009 using atomic absorption spectrometer and standard analytical methods. Conductivity, pH, turbidity, phosphate ions and total coliform values obtained in some of the wells were out of the recommended range for drinking water. Water quality index analysis was carried out using information entropy method. Water quality index of the wells when compared with the permissible limits of international standards, ranked the bore hole as 'excellent' in the dry season of year 2009 and just 'good' in the rainy season of the same year. Ground water sampling stations were ranked extremely poor at least once out of the four seasons considered. Water quality index ranking also showed that the quality of the wells declined over the years. The correlation coefficient matrix (p \ 0.05) of water quality index and the parameters showed significant relationships between water quality index and total coliform (0.99), total dissolved solids and conductivity (0.96), hardness and Ca 2? (0.68), hardness and Mg 2?(0.75). Water quality index also showed moderate significant relationship with total dissolved solid, conductivity and N-NO 3 -. High concentration of total coliform in most of the shallow wells in the environment, due to bitumen deposit, renders them unfit for human consumption unless properly treated.