Background: Patents have been granted for a number of techniques for petroleum biodegradation
including use of micro-organisms for degradation of hydrocarbon-based substances and for hydrocarbon
degradation in oil reservoirs, but there is a dearth of information on hydrocarbon degradation in different soil textures.
Objective: Hence, this work investigated the effects of different soil textures on degradation of petroleum hydrocarbons
during a six-week period.
Methods: Five soil textural classes commonly found in Port Harcourt metropolis, Nigeria, namely sand, loamy sand,
sandy loam, silty clay and clay, were employed. The soils were contaminated with the same amount of crude oil and then
remediated by biostimulation. Selected soil properties were monitored over time.
Results: Bacterial numbers declined significantly in the fine soil textures after petroleum contamination, but were either
unaffected or increased significantly in the coarser soil textures. Hydrocarbon losses ranged from 42% - 99%; the sandy
loam had the highest, while the clay soil had the least total hydrocarbon content (THC) reduction. The total heterotrophic
bacterial (THB) counts generally corroborated the THC results. Fold increase in bacterial numbers due to remediation
treatment decreased with increasing clay content.
Conclusion: The results suggest that higher sand than clay content of soil favours faster hydrocarbon degradation. Hydrocarbon
degradation efficiency increased with silt content among soil groupings such as fine and coarse soils but not necessarily
with increasing silt content of soil. Thus, there seems to be cut-off sand and clay contents in soil at which the effect
of the silt content becomes significant.