African Journal of Biotechnology Vol. 6 (16), pp. 1939-1943, 20 August 2007   

ISSN 1684–5315 © 2007 Academic Journals        

Full Length Research Paper

Studies on the effect of petroleum hydrocarbon on the microbial and physico-chemicals characteristics of soil

Akpor, O. B.¹*, Igbinosa, O. E.¹ and Igbinosa, O. O.²

¹Department of Microbiology, Obafemi Awolowo University, Ile-Ife, Nigeria.

²University of Sint Eustatius, School of Medicine P.O.73, Goldenrock Sint Eustatius, Netherlands-Antilles.

*Corresponding authors E-mail: akpor2006@gmail.com.

Accepted 20 June, 2007

The microorganisms capable of degrading crude oil are present in any conceivable environment. This study was aimed at ascertaining the bacteria and fungi that are able to survive in soils contaminated with 3 different petroleum hydrocarbon fractions (premium motor spirit ‘PMS’, domestic purpose kerosene ‘DPK’ and automotive gas oil ‘AGO’). Soil surface samples (0.5 cm) were collected randomly from different locations in Ile-Ife in Osun State of Nigeria. Soil samples were contaminated with the hydrocarbon fractions in a ratio of 1:1 and estimated for total bacterial counts (TBC), total fungal counts (TFC), and total hydrocarbon utilizing bacterial counts (HYCUB). The following anions and cations were also determined in the soil samples; Ca²⁺, Mg²⁺, K⁺, Na⁺, NO₃⁺, and NO₂⁺. The results showed that TBC ranged from 2.1 x 10³ to 3.6 x 10⁶ cfu/g, while TFC was in the range of 0 to 2.0 x 10³ cfu/g and HYCUB was in the range of 4.8 x 10¹ to 4.5 x 10³ cfu/g. Apart from average HYCUB counts that was highest in DKP samples, other counts were highest in the PMS samples. Similar bacteria of diverse species were isolated from the contaminated soil samples, although their months of occurrences and numbers differed, Mg²⁺, K⁺ and Na⁺ all increased in all the contaminated soils, at the end of the study. In this study, the HYCUB counts were negatively correlated with Ca²⁺ (r = -0.667, p<0.05). This study revealed a significant correlation between total fungal counts and hydrocarbon-utilizing bacterial counts (r = 0.700, p< 0.05) and a negative correlation between total bacterial counts and Na⁺ (r = -0.677, p< 0.05). The results of the study has revealed that refined petroleum can have an increasing or decreasing effect on soil physico-chemical characteristics, and that some of these physico-chemical characteristics may have effect on microbial counts.

Key words: Hydrocarbon, microbial counts, physico-chemical characteristics.