Evaluation of Soil Physicochemical Properties of Oil Spill Remediation Project in Kegbara-Dere Community, Rivers State, Nigeria

This study was designed for the assessment of physicochemical properties of soils from oil polluted environs in Kegbara-Dere (K-Dere) Community, Gokana LGA, Rivers State, Nigeria. Soil samples were collected from four sites marked A (B-Dere), B (Kpor), C (Bomu), and D (Bera) representing different areas across K-Dere and environs, where remediation exercise were carried out between 2006-2008. Three of the sites A, B, C were heavily oil contaminated and site D used as control wasn’t oil spill soil. At each of the sampled sites, soil samples were collected from two points at a distance of 100 meters, and in two depths, 0-15 cm and 15-30 cm using soil auger. The samples were analyzed for the determination of the rate of physicochemical parameters using standard analytical techniques. Descriptive statistics which includes mean, standard deviation, coefficient of variability and analysis of variance (ANOVA) were employed to summarize the data. The results of the statistical analysis showed that there were significant different at (P<0.05). The oil polluted soils had higher Clay (>60.0%) and lower sand and silt contents than the control site. Soil mean pH varied between 5.94±0.42 in the control and 7.16±0.63 in the oil polluted soils. Total nitrogen (N) content of the oil spilled soils ranged from 0.57±0.74 to 1.09±0.81% and is slightly higher than that of the control soil. This is reflected in the high value of organic matter (8.29±1.34%) in oil spilled soils. Available Phosphorus was quite high ranging from 37.11±2.98 to 78.42±3.97 mg/kg. Cation exchange capacity (CEC) varied between 13.88±1.27 and 90.95±2.40cmol kg−1. EC levels were moderate to high ranging from 198.11±2.98 to 968±93.34cmol/kg. All Anion (HCO3- , SO42- , CO32-) and exchangeable cations (Ca, Mg, K and Na) evaluated were far above the permissible limits set by WHO/FAO for agricultural soil. Average levels of Pb ranged from 241±54.45 to 349±70.71 mg/kg in the oil spilled soils and 117±6.36 to 286±1.41 mg/kg in the control. Mean concentration of Selenium (Sn) in the oil spilled soils varied between 29.53±2.94 and 43.7±1.40 mg/kg, and is slightly higher than the control (27.01±4.60 mg/kg), while Cd was found in trace amounts (1.32±0.98 mg/kg). These values were all far above the maximum tolerable limits set by FAO/WHO for agricultural soil. The results of this study revealed that the 2008 oil spilled remediation exercise carried out in K-Dere Community yielded a big positive result. Moreover, Aftermath, the recontamination of the area was observed to be on steady increase due to the accumulation of more pollutants arising from the oil industry in the area for over a decade without remediation.