Changes in soil microbial respiration and physicochemical properties following bonny light crude oil contamination of sandy loam soil

Abstract

This study was undertaken to investigate the effects of Bonny light crude oil contamination of sandy loam soil on aspects of microbial metabolism and physicochemical properties of the soil. Bonny light crude oil (specific gravity = 0.81) was used at eight different levels (0.5%, 1.0%, 2.0%, 2.5%, 5.0%, 10.0%, 15.0% or 20.0% v/w of soil) for the controlled pollution of pristine soil samples, each weighing 1 kg. The experiment lasted for eight
weeks. Results of the effects of crude oil on the physicochemical properties of the soil showed that high levels of the oil significantly (p< 0.05) increased soil organic matter but had no significant effect on the pH and moisture content. With the exception of organic carbon, the levels of bioavailable nitrogen, sodium, potassium, calcium, magnesium, sulphur and phosphorus in the test samples with higher levels of crude oil (5.0%, 10.0%, 15.0% and 20.0%) were significantly reduced when compared to their levels in the controls. Similarly, higher levels of the oil significantly (p<0.05) reduced soil microbial phospholipid synthesis and CO emission. 2 Correlation analysis using the Pearson's correlation model showed a positive correlation between soil CO and 2 phospholipid (r = 0.74).

Keywords: Contamination, Crude oil, Microbial respiration, Physicochemical properties.