Abstract

Ogba-Egbema area has played host to oil and gas production and transportation for more than four decades with some adverse impact on the environment. This research assessed the status of seven heavy metals (Fe, Zn, Pb, Cu, Mn, Cr, and Hg) and hydrocarbon (THC, PAH and BTEX) in soils of five transects in Ogba-Egbema. A total of 120 soil samples were analyzed (45 genetic horizon samples from eight soil profiles and 75 random surface soils; 15 from each of five transects). Heavy metal status of the soils varied greatly: Zn (<0.01 – 15.10 mg/kg); Pb (<0.01 – 285.50 mg/kg); Fe (247.0 – 13128.5 mg/kg), Mn (<0.01 – 40.40 mg/kg), Cu (0.01 – 20.01 mg/kg), Cr (0.01-17.71 mg/kg) Hg was below detectable limit (<0.01mg/kg) in all the soils studied. The ranges of hydrocarbons along four transects in the un-impacted areas were: THC (0.93 – 55.8); PAH (0.01 – 0.9) and BTEX (<0.1), while in the impacted areas (along the crude oil pipeline right of way) the ranges were: THC (30.0 – 217.50); PAH (1.6 – 12.40) and BTEX (<0.1). The study revealed that in the impacted areas both heavy metals and hydrocarbons were marginally higher than in normal soils but were far below the maximum tolerable levels set by FAO and WHO for agricultural soils. There was no threat of heavy metal and hydrocarbon pollution in these soils. However, farming activities should be discouraged along the pipeline right of way given the relatively higher status of heavy metals and hydrocarbons to avoid the possibility of bio-accumulation in cultivated crops.