Microbiological and Physicochemical Evaluation of Oil-polluted Soil from Major Auto Mechanic Shops in Port Harcourt Metropolis, Rivers State, Nigeria

Abstract

The capability of microorganisms to utilize spent oil in polluted soil from some major auto mechanic workshops in Port Harcourt metropolis as the sole source of carbon and energy was studied. Soil samples were collected from three (3) Auto mechanic workshops (Mile 3 Mechanic Village (N 4º48' 34.07'', E 6º59' 10.17''), Ikoku Mechanic Workshop (N 4º47' 54.28'', E 6º59' 36.42'') and Elekahia Zone H Mechanic Workshop (N4º49' 11.62'', E 7º1' 16.58'') in Port Harcourt, Rivers State, Nigeria from depths of 0–30 cm, 30–60 cm and 60–90 cm at the same spot from each station. Soil samples were analysed microbiologically and physicochemically using standard methods. The control sample was obtained behind the Biology Building of Rivers State University, Port Harcourt. The results of the total heterotrophic bacterial and fungal counts showed that the microbial load was high at a depth of 0 to 30 cm for all the samples analysed including the control. With 60-90 cm depth, low microbial counts were obtained. The total heterotrophic bacterial counts from the three mechanic workshops ranged from 6.8 X 108 to 2.3 X 109cfu/g while the total heterotrophic fungal counts ranged from 1.3 X 106 to 8.0X 106 cfu/g. The spent oil-utilizing microbial populations ranged from1.0 X 105 to 3.0 X 106cfu/g and1.0 X 105 to 8.0 X 105 cfu/g for the bacterial and fungal counts respectively. Five spent oil utilizing bacterial isolates of the genera, Pseudomonas, Klebsiella, Bacillus, Micrococcus and Proteus and five fungal isolates of the genera, Penicillium, Candida, Rhizopus, Fusarium and Aspergillus were obtained from spent oil-polluted soil in this study. The pollution index of the different physicochemical parameters obtained from the different sample stations was as follows: Electrical Conductivity (EC): Mile 3 had the highest with the mean of 12.50 ±0.0-13.20±0.0µs/cm, while Ikoku had the lowest with mean of 10.99 ± 0.0-11.50 ± 0.0 µs/cm. Ikoku had the highest pH level with mean of 7.0 ± 0.0- 8.5 ± 0.0 while Mile 3 had the lowest pH level with mean of 6.5 ± 0.0-7.59 ± 0.0. Ikoku had the highest Total Organic Carbon (TOC) with mean of 17.55 ± 0.0-20.60 ± 0.0 mg/kg while Elekahia had the lowest with the mean of 16.99 ± 0.0-18.0 ± 0.0 mg/kg. Ikoku had the highest Total Hydrocarbon Content (THC) with mean of 38,862 ± 0.0-40,500 ± 0.0 mg/kg while Mile 3 had the lowest with the mean of 20,550 ± 0.0-30,000 ± 0.0 mg/kg. From the Pollution Index Analysis, Ikoku Auto Mechanic Workshop is more contaminated with Spent oil than Mile 3 and Elekahia.