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ABSTRACT
The dependency on fossil fuels as energy source has resulted in serious environmental issues in recent times. Hence, petroleum contaminated soils must be treated to ensure that human health and the environment remain protected. Soil samples from hydrocarbon contaminated site were analyzed to identify population of autochthonous hydrocarbon degrading bacteria (HDB) present in the hydrocarbon contaminated soil. Soil samples were collected from eight different locations tag Site A-H (polluted and unpolluted (control sample A) at a depth of 0-120 cm. Pour plate method using Nutrient Agar (NA), was used for the isolation of hydrocarbon degrading bacteria (HDB) counts incubated at 30 oC for 24 hours. Results obtained from the study were subjected to statistical analysis (ANOVA) using Turkey's test to separate means of significant difference (p<0.05). The results of total heterotrophic bacteria count ranged from (2.3 ± 3.5 - 5.2 ± 3.5) x 104 cfu/g. The bacteria isolates identified were Pseudomonas sp., Micrococcus sp., Enterobacter sp., Acinetobacter sp., Arthrobacter sp., Bacillus sp. and Klebsiella sp. The result of soil texture revealed that silt ranged from (18.10±14.90 – 65.75±0.43ab), clay ranged from (16.55±1.35a – 36.45±2.75) %, while sand ranged from 11.26±0.01a – 52.30±8.60a) %. The heavy metal results were below WHO permissible limits. The results of the physiochemical properties revealed that pH, EC, carbon, nitrogen, phosphorus, water holding capacity, bulk density and moisture content were statistically significant with respect to normal control. The results of the total petroleum hydrocarbon (TPH) across all sampling sites were below the 5,000 mg/kg permissible limit for hydrocarbon contaminated soil. The results of polycyclic aromatic hydrocarbon (PAH) revealed the presence of acenaphthene (22.61 mg/kg) fell within (20 mg/kg – 60 mg/kg) that represents slightly polluted soil. Conclusively, soil is a natural habitat for bacteria to reside and the physiochemical parameters of soil can be distorted by hydrocarbon contamination.
