EFFECTS OF BIOREMEDIATION OF PETROLEUM POLLUTION ON SOIL PHYSICOCHEMICAL PROPERTIES AND METALS BIOAVAILABILITY IN SOUTHSOUTH NIGERIA

Abstract

The effects of bioremediation on selected soil physicochemical properties and heavy metals bioavailability in South South geopolitical region of Nigeria, was studied. The level of petroleum pollution and remediation the physicochemical and metals bioavailability in bioremediated soils were examined in 20 composite soil polluted and remediated soils each with a composite control samples. The soils were collected, processed and chemically extracted and analyzed according to standard methods and procedures. The results showed adequate remediation levels ranging from about 95 to 98% such that the residual total petroleum
hydrocarbons (TPH) were within the Nigeria acceptable levels and below the intervention values. However, a general drop in the soils’ pH with average reduction in pH values of 2.32 in the bioremediated sites was observed. Also observed, was the increase in the bioavailability of selected heavy metals with average increase values of 11.91, 13.70, 16.23 and 14.84% for Cr, Pb, Cd and As respectively. Similarly, the percentage increase in bioavailability for Ba, Cu, Ni and Zn were 13.23, 10.90, 10.63 and 11.03 % respectively. The R2 values for the scattered graph plot of pH drop on metal bioavailability ranged from 0.7091 – 0.8988. The increment in the metal bioavailability could be attributed to drop in the pH of the sites during the remediation field work.The study revealed the need for re-conditioning petroleum polluted soils after their bioremediation