Abstract
The study evaluates the soil properties response to crude oil pollution using remediation by enhanced natural attenuation (RENA) technique in the oxisols type of soil. Uncontaminated soil of 600 g was collected from the topsoil (0-15cm) depth around Agbada 1 Flow Station, Mbodo Community, Aluu, Port Harcourt City, Nigeria. This site was chosen because of the possibility of soil in the area to be polluted with crude oil in the future. The soil sample was air-dried and carefully sieved with 2mm diameter mesh from which 400 g of soil (sample B) was contaminated with 1 mL of Bonny Light type of crude oil and left for a week and 200 g called sample A (control) was uncontaminated. Thereafter, the sample B was subdivided into two equal parts (200g) namely sample B1 and sample B2. Sample B1 remained contaminated but unfertilized while sample B2 was fertilized with 1 g of NPK 15-15-15. The experiment was left for a week in the laboratory under room temperature. Laboratory analysis was carried out on the soil samples (A, B1 and B2) every week for a total period of 4 weeks on soil pH, total organic carbon, organic matter, total N, SO4, available P, Cd, Cr, Pb, Fe, total petroleum hydrocarbon (TPH), moisture content and water holding capacity. Descriptive statistics was used to explain the concentrations of the soil properties in response to crude oil contamination in both fertilized and unfertilized contaminated soil samples, Spearman’s rank correlation was used to determine the relationship between duration and soil response to the application of fertilizer while chi square was used to determine the significant differences in the treatments. There was a reduction in the TPH level from 7150 mg kg-1on the first day of application of fertilizer to 2550 mg kg-1after the 28th day. The water holding capacity and moisture content increased with time from 35.6% and 59.4% on the 1st day to 47.7% and 65.3% on the 28th day respectively. However, the concentrations of Cd, Pb, and Fe reduced with time and no trace of Cr. Significant relationship was observed between duration of the treatment and moisture content (r=0.958), WHC (r=0.964), total N (r=-0.829) and available P (r=0.827). Similarly, significant differences existed in the treatments in moisture content, WHC, total N and available P. The study recommended that there should be a periodic monitoring and management of oil spill sites in oil producing communities to sustainably manage soil for food production and prevent loss of biodiversity.
