Bacteriological and Physicochemical Properties of Petroleum-Contaminated Soil Collected from a Mechanic Site in Abuja, North-Central Nigeria

Elevated levels of petroleum hydrocarbon and certain heavy metal compounds in soil samples due to environmental and manmade operations can amount to concentrations considered as toxic. Soil samples from 3 different locations, 30 meters from each other were collected and assessed for polycyclic aromatic hydrocarbon (PAH), total petroleum hydrocarbon (TPH), selected heavy metal concentrations, pH, Electrical Conductivity, texture, organic matter, moisture content and bacterial population. The results on the test sites showed that pH range for the workshop soil samples was between 5.08-5.45 in comparison to the control 6.74. Data obtained also revealed that the tested site A alone contained lead (44.91 mg/g) and cadmium (0.01 mg/g). The heavy metal content for sites A, B and C where higher than that of the control site D for which the enrichment factors was determined for sodium (1.07, 3.34, 4.12), copper (2.73, 2.63, 1.57), iron (9.84, 10.67, 9.21), zinc (4.78, 2.58, 2.98), nickel (1.44, 1.11, 1.56) and manganese (2.57, 2.23, 3.77) respectively. The moisture content and electrical conductivity ranged between 44.7-46.5% and 985.6-1124.7 (μS/cm) respectively as opposed to 44.9%, 846.3 (μS/cm) for the control. Total bacterial enumeration revealed a count of 2.28 x 104 (cfu/g), 2.01 x 104 (cfu/g), 1.98 x 103 (cfu/g) and 2.71 x 105 (cfu/g) at sites A, B, C and D respectively. The presence of hydrocarbon and heavy metal pollutants due to the activities at the mechanic workshop resulted in change of known physicochemical properties which in turn affects the ecology as well as life forms in the area