BACTERIOLOGICAL AND PHYSICO-CHEMICAL ANALYSIS OF DIESEL-CONTAMINATED SOIL IN BENIN CITY, EDO STATE, NIGERIA

Abstract

The bacteriological and physico-chemical analysis of diesel contaminated soil was carried out over a period of seven weeks. Different volumes of diesel were added to 1000g of soil in microplots. Microplot with no diesel added served as control and was labelled sample A. Samples B, C, D, and E contained 250ml, 500ml, 750ml and 1000ml of diesel respectively. Samples were collected weekly for analysis. The bacterial count ranged from 8.70 ± 0.92 x 104 cfu/g to 1.28 ± 0.89 x 105 cfu/g, 9.70 ± 0.05 x 104 cfu/g to 1.02 ± 0.11 x 105 cfu/g, 4.50 ± 1.40 x104 cfu/g to 9.10 ± 0.11 x 104 cfu/g, 3.20 ± 0.05 x 104 cfu/g to 8.80 ± 0.05 x 104 cfu/g and 1.00 ±0.05 x 104 cfu/g to 8.20 ± 0.05 x 104 cfu/g in samples A, B, C, D and E respectively, showing that the bacterial counts in the treated samples declined and later increased at week seven of the experiment. The bacteria isolated from the soil samples were Bacillus subtilis, Flavobacterium sp, Klebsiella sp., Micrococcus sp. and Pseudomonas aeruginosa. Analysis of the physico-chemical parameters showed that there was reduction in pH (8.80 ± 0.06 to 5.10 ± 0.06) and % Nitrogen (15.90 ± 0.06 to 4.90 ± 0.06) for the different concentrations as the weeks progressed. The temperature (28.00 ± 0.60 to 33.00 ± 0.60 0C), Chemical oxygen demand (COD) (105.00 ± 0.58 to 459.00 ± 0.58) and % Carbon (3.37± 0.06 to 23.99 ± 0.33) increased with time for the various concentrations of diesel contamination, compared to the control. The results of this study revealed that diesel altered the soils‘ physico-chemical properties and the biological activity of the soil environment