EVALUATION OF HYDROCARBON REMEDIATING POTENTIALS OF AUTOCHTHONOUS MICROORGANISMS AND SOME TROPICAL PLANTS GROWING IN THE VICINITY OF AUTOMOBILE WORKSHOPS IN NIGER STATE

Abstract

This study was conducted to evaluate the hydrocarbon remediating potentials of some tropical plants growing in the vicinity of automobile workshops (AW) in parts of Niger State, Nigeria. This involved a preliminary survey to major AW in Minna, Bida, Suleja and Tegina in Niger State to identify spent engine oil (SEO) tolerant plants growing in the vicinity of the AW. The microorganisms in the rhizosphere and non- rhizhosphere were enumerated using the spread-plate method on standard media and were identified using morphological, biochemical and molecular techniques. Besides, the microorganisms were screened for SEO utilization using spectrophotometric analysis. The physicochemical properties of the SEO polluted soil were determined using standard methods. The bioremediation potential of Melissia officinalis (Lemon balm) and Urena lobata (Caesar weed) were assessed by monitoring the Total Petroleum Hydrocarbon, heavy metal content, GCMS analysis of residual oil and the generation of plant exudates during the phytoremediation process. The experimental setup was a complete randomized design (CRD) conducted at the biological garden of the Federal University of Technology, Minna. The results of the total aerobic heterotrophic bacterial counts in SEO contaminated soil within the various workshops showed that the counts were generally low when compared to the counts from both rhizosphere and non- rhizosphere soils in the AW vicinity. The mean bacterial counts of the AW were more in Tegina (2.37 106 4.01 106 cfu/g), while Bida had the lowest bacterial counts (1.56 105 2.13 105cfu/g) when compared to Minna (2.03 106 3.44 106 cfu/g) and Suleja (1.36 106 2.28 106cfu/g). However, statistical analysis revealed that there were no significant differences (p>0.05) in bacterial counts among the stations. The total fungal counts of soil within the AW were low as compared to the rhizosphere and the non-rhizosphere soils, with Bida having the highest counts (1.36 106 2.26 106 cfu/g) while Tegina and Minna had the lowest counts (3.41 105 5.71 105 cfu/g). Statistical analysis showed that there were no significant differences (p>0.05) across the locations. The SEO utilizing bacterial counts were low. The mean counts ranged from 2.32 103 5.17 103 cfu/g to 1.44 103 5.17 103 cfu/g while the SEO utilizing fungal counts ranged from 9.01 102 5.17 102 cfu/g to 1.02 101 5.17 101 cfu/g. Statistical analysis showed significant differences (p<0.05) among the locations. Microorganisms isolated in the study were Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, Aspergillus niger, Penicillium notatum and Fusarium oxysporium. Species of Bacillus, Staphylococcus and Aspergillus were more consistently isolated and constituted 9.16- 9.83%. Bacillus subtilis strain EE681738 and Aspergillus niger strain HQ659967 were the most efficient spent engine oil utilizers. The residual total petroleum hydrocarbon in M. officinalis treated soil was 56.61%, while it was 50.55% in U. lobata treated soil after seven months. The physicochemical properties of SEO polluted soil remediated with M. officinalis and U. lobata revealed that after seven months of bioremediation, nitrogen, organic matter, potassium and phosporus contents gradually increased. GCMS analysis of the hydrocarbons revealed that 9H-Fluorene, Diphenylacetylene, Tritriacontane, Nonahexacontane, Hentriacontantane, Octatetracontane, IH-Pyrrolo[2,3-b] quinoxalin, Ethanone, Eicosylisobutyl ether, Inolin-2-yl, Carbonic acid were completely degraded while the following compounds, Phenyleamine, Pyrimidine, Carbonic acid, Coumarin, Acetic acid, Naphthalene, 4-Chlorophenoxy were found in the exudates secreted by M. officinalis and U. lobata. The results obtained suggest that plants found within the vicinity of AW particularly, M. officinalis and U. lobata are good candidates for phytoremediation of SEO polluted soil in the tropics.