Evaluation of Some Properties of Soils Affected by Diesel Oil Pollution in Uyo, Niger Delta Area, Nigeria

Abstract

Soil pollution due to oil spill is a common problem in the Niger Delta region of Nigeria. This necessitated the experiment to determine the effect of diesel oil pollution on some soil properties in Uyo within the Niger Delta region of Nigeria.  The experiment was conducted at the University of Uyo Teaching and Research Farm in 2009. It was laid out in a completely randomized design (CRD) in triplicates.  The size of the experimental plot was 60.7m², sub-divided into three sub-plots each measuring 20.24m². Each sub-plot was divided into five experimental units receiving the following treatments: 0 (control), 8, 11.5, 14.5 and 22.0 litres of diesel oil, which was converted into 0.0%, 1.39%, 2.50%, 3.45% and 5.06%. The results at two weeks after oil application (2WAOA) showed significant decrease in soil pH from  4.90 in the control  to 4.35 in 5.06% pollution levels resulting in soil reaction being rated as extremely acid in oil polluted soils compared to the control with soil/reaction being rated as very strongly acid. There was depletion in total nitrogen and basic cations such as Ca²⁺, Mg²⁺, Na⁺ and K⁺. at 2WAOA. Carbon/nitrogen ratio increased in all the treatments, with the highest pollution level (5.06%) having 114.33±1.41. Percent base saturation increased inconsistently across the treatments with the highest being 56.96±0.003% (for 2.50% pollution) and the lowest being 44.24±0.008% (for 5.06% pollution level). The results at 18WAOA showed varying degrees of increase in the soil pH. The control plot had the pH of 6.39±0.002 and the highest pollution level of 5.06% had the pH of 6.05±0.2. The soil reaction at 18 WAOA was rated slightly acid compared to extremely acid in 2WAOA. There were varying degrees of increase in organic carbon in all the treatments. Total nitrogen also increased at 18WAOA, the increase ranged from 50-80%. Carbon/Nitrogen ratio was significantly reduced (? < 0.05) across the treatments.  Basic cations and percent base saturation increased across the treatments at 18WAOA. Correlation between concentrations of diesel oil in the soil and some soil properties at 2WAOA and 18 WAOA showed that at 2 WAOA soil pH, total N and percent base saturation showed negative correlation, while organic carbon and carbon/nitrogen ratio showed positive correlation. At 18 WAOA, organic carbon and total N, showed positive correlation, while soil pH, carbon/nitrogen ratio and percent base saturation showed negative correlation.

Keywords: Evaluation, Soil Properties, Oil polluted, Niger Delta Area, Nigeria