Role of Plant-Microbe Interactions in Rhizoremediation of Petroleum Product-Polluted Nigerian Soils

Plant-microbe interactions in petroleum product-contaminated soils were examined under field conditions, to analyze the effects of environmental factors on rhizoremediation. Different plant types (elephant grass, cassava, carpet grass, Indian bamboo, fern, palm and a mixture of these plants) were considered. The abundance of effective indigenous microorganisms (EIM) and remediation time were also considered. Eight soil samples were collected from crude oil-contaminated sites of Ogoni, Rivers State, Nigeria. Total viable counts were taken using spread plate methods. Hydrocarbon utilizing microorganisms using mineral salt agar with crude oil vapor phase gave counts in the range of 102 – 108. Gas Chromatographic – FID methods gave results of 9 field samples for TPH to range from 0.96 mg/kg for control to 4,650 mg/kg for oil well 3 without vegetation. Polyaromatic hydrocarbon (PAH) of 9 field samples ranged from 0.26 mg/kg for control to 30.066 mg/kg depending on the extent of pollution of the site. Mixed plant population showed abundance of EIM (108) and greater TPH and PAH removal. The effect of time on the concentration of TPH and PAH in the different samples show that significant difference exist, P – value = 0.420. Microbial counts are significantly different over time, also microbial counts are significantly different in the different samples (F-value = 3.15, 2.76, 2.53, 2.1, 1.92 and 1.7) for rows, columns and layers. Local Nigerian plants could promote rhizoremediation of crude oil polluted soils