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Aim: To evaluate the effect of illegal crude oil refining activities on soil microorganisms using standard microbiological methods.
Study Design: This study employs laboratory experimental design, statistical analysis of the data and interpretation.
Place and Duration of Study: Soil samples were taken once a month for three months (May- July, 2018) from Ke in Degema Local Government Area of Rivers State, Nigeria, where illegal crude oil refining activities are ongoing.
Methodology: Using standard microbiological methods, total culturable heterotrophic bacterial counts, total fungal counts, Hydrocarbon utilizing bacterial and fungal counts were analysed to evaluate the effect of the activities. Total hydrocarbon content of the soil samples was also analysed.
Results: The populations of the total heterotrophic bacterial, fungal and hydrocarbon utilizing bacterial (HUB) and fungal (HUF) counts of the contaminated soil were enumerated. The mean total heterotrophic bacterial counts in Station 1 around the pot ranged from 2.5 x 105 to 1.8 x 106cfu/g, fungal counts ranged from 2.1 x 103 to 4.4 x 104cfu/g, HUB (HUB) counts ranged from 4.2 x 104 to 6.4 x 105cfu/g and hydrocarbon utilizing fungal (HUF) counts ranged from 1.5 x 103 to 4.0 x 103cfu/g. The results of soil samples taken 20m away from the Pot location ranged from 7.0 x 105 to 8.2 x 106cfu/g for total heterotrophic bacterial counts, fungal counts ranged from 2.3 x 103 to 1.5 x 104cfu/g, HUB ranged from 4.7 x 104 to 5.7 x 105cfu/g and HUF ranged from 2.0 x 103 to 3.5 x 103cfu/g. Also, the results of total heterotrophic bacterial counts for Station 2 ranged from; 4.3 x 105 to 3.3 x 106cfu/g, fungi 2.0 x 103 to 3.3 x 104cfu/g, HUB ranged from 3.8 X 104 to 5.4 x 104cfu/g and HUF 1.6 x 103 to 3.5 x 103cfu/g, while 20m away from the Pot total heterotrophic bacteria ranged from 1.3 x 107 to 6.5 x 107cfu/g, fungi 5.8 x 103 to 1.4 x 105cfu/g, HUB 5.4 x 104 to 1.1x 105cfu/g and HUF 3.1 x 103 to 4.7 x 104cfu/g. While the control samples taken from inside the community where no such activity is on, ranged from 2.6 x 107 to 7.9 x 107cfu/g for total heterotrophic bacterial counts, total heterotrophic fungal counts ranged from 2.8 x 104 to 5.3 x 104cfu/g, HUB 2.0 x 102 to 3.1 x 102cfu/g and HUF 2.0 x 101 to 2.3 x 101cfu/g. twelve bacterial genera were identified and eight fungal genera: Bacillus, Alcaligenes, Flavobacterium, Acinetobacter, Pseudomonas, Micrococcus, Proteus, Serratia, Enterobacter, Streptococcus, Escherichia, Staphylococcus, Penicillum, Aspergillus, Fusarium, Mucor, Rhizopus, Geotrichum, Candida, and Cladosporium. Total hydrocarbon content ranged from 106 to 281mg/kg across the locations. When compared with the control, it was observed that the microbial population and diversity were adversely affected. These variations observed in the microbial population are indicative of the effect of the illegal refinery on the soil microorganisms.
Conclusion: The results of this study indicates that the continuous contamination of the soil environment by the activities of illegal crude oil refining, lead to a decrease in microbial population and diversity. This may result in devastating ecological damage, adversely affecting the ecological balance which may affect food chain and in turn animals and humans.