Effects of Natural Attenuation on the Nutrient Stability of Simulated Oil Spill Contaminated Soils

Natural attenuation of off-field laboratory-simulated crude oil-contaminated soils were investigated to determine the effects on the nutrient stability without organic inputs. Soil samples were collected from Elele and Isiokpo in the Ikwere local government area of Rivers State, Nigeria. Twenty kilograms of the soils were spiked with different milliliters of crude oil and the characteristics of the soils, such as pH, electrical conductivity (EC), total organic carbon (TOC), total organic matter (TOM), cation exchange capacity (CEC), total hydrocarbon content (THC), and total petroleum hydrocarbon (TPH), were determined immediately after contamination (CT) and six months after natural attenuation (NA) using standard analytical methods. Results obtained showed a decrease in the values of the physicochemical properties of the soils as shown: pH (6.11 to 5.60); TOC (4.49% to 3.19%); TOM (7.76% to 5.52%) for Elele soils, and for soil samples from Isiokpo pH (5.89 to 5.85); TOC (3.96% to 2.77%); TOM (6.84% to 4.79%). Natural attenuation decreased THC and TPH values by 14.32% and 12.53% in Elele soil and 12.37% and 9.75% in Isiokpo soils, respectively. The result of the study showed that natural attenuation, without any organic input, is effective in remediating petroleum hydrocarbon contents of oil-impacted soil and thus restoring soil physicochemical properties to arable form.