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

Abstract

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.