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Microbial
population changes in tropical agricultural soil
experimentally contaminated with crude petroleum
Oluwafemi S. Obayori*, Matthew O.
Ilori, Sunday A. Adebusoye, Olukayode O. Amund and Ganiyu O.
Oyetibo
Department of Botany and Microbiology,
University of Lagos, Akoka, Lagos, Nigeria.
*Corresponding author. E-mail:
femiobayori@yahoo.com
Accepted 7 July, 2008 |
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Impacts of crude petroleum pollution on the soil environment
and microbial population dynamics as well as recovery rates
of an abandoned farmland was monitored for seven months
spanning the two major seasons in Nigeria with a view to
establishing process conditions necessary for development of
effective strategies for bioremediation. The physico-chemistry
of the control and contaminated soils differed just
significantly (P < 0.05). Whereas these factors were
relatively stable over the period of investigation for the
control site, a downward trend was observed for the
experimental. The polluted soil showed significant diversity
in structure and number of flora .There was an initial drop
in microbial population densities at the onset of pollution
but, a gradual increase was observed thereafter. Higher
counts of microflora were obtained for April, May, June and
July samples which coincided with the onset and peak of wet
season. A rapid and significant reduction in residual oil
concentration was observed during this period. Overall,
nearly 100% of the crude oil pollutant was degraded within
the 28-week study period. The residual oil concentration
gave a high but negative correlation coefficient (r = -0.84
to -0.90) with total heterotrophic and hydrocarbon-utilizing
populations. On application of data generated to model
equations, approximately 60.5 weeks would elapse before the
contaminated soil could recover from the impact of the oil.
Our results show that a natural population readily able to
degrade crude oil is present in the soil chosen for this
study. However, it may be necessary to monitor the level of
inorganic nutrients and adjust some appropriately to enhance
biodegradation of the organic pollutant.
Key
words:
Biodegradation, crude petroleum, heterotrophic counts,
hydrocarbon-utilizers, microflora, pollution, residual oil
concentration. |
