Effects of Varying Concentrations of Crude Oil on Some Physicochemical Properties of Agricultural Soil

Abstract

This research investigated the effects of varying concentrations of crude oil on some physicochemical characteristics of crude oil polluted agricultural soils from Igodan- Lisa, Oba-Ile and Ido-Ani areas of Ondo State, Nigeria. The soil samples were exposed to 1-4% (w/w) crude oil and analyzed monthly for six periods using standard physical and chemical analytical techniques. Results indicated that the physicochemical properties were altered. The physicochemical parameters varied with increase in the amount of crude oil spilled and time. The pH and moisture contents (MC) progressively decreased with increase in concentration of crude oil applied to the samples. Polluted soils had lower pH values (4.91- 6.17) and MC (15.24% to 26.83%) relative to control samples. The organic matter content increased with increased amount of crude oil spilled in the range of 6.65-10.93%. The organic carbon contents progressively increased with concentration of crude oil and sampling days. At 4% crude oil pollution, the organic carbon content in the samples were 6.04-8.28%, 5.39-7.82% and 6.05-8.21% for Igodan-Lisa, Oba-Ile and Ido-Ani soils respectively at 0-180 days of experiment. The changes in soil physicochemical suggested that soil integrity and quality is altered by crude oil contamination. The increased acidity with time also suggested the release of acidic metabolites in bioremediation by intrinsic microorganisms.