Ecological Implications and Source Apportionment of Heavy Metal and Hydrocarbon Contaminants in the Soil of a Poorly Crude Oil Remediated Site in Nigeria: A Case of Ikot Ada Udo Community
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Department of Zoology and Environmental Biology, Faculty of Biological Sciences, University of Calabar, Nigeria
Department of Biological Science, Faculty of Natural and Applied Sciences, Arthur Jarvis University, Akpabuyo, Cross River State, Nigeria
Publication date: 2021-11-01
Corresponding author
Akaninyene Joseph   

Department of Zoology and Environmental Biology, Faculty of Biological Sciences, University of Calabar, Nigeria
J. Ecol. Eng. 2021; 22(10):275-286
The ecological risk and source apportionment of heavy metals and hydrocarbons in soil from the study site was carried out. Composite soil samples (n = 48) were collected from 3 sampling points (SP 1, SP 2, SP 3) within the site at 50, 200, and 500 meters, respectively, from the oil well and from a control site (Ibagwa, Abak) at 10,000 meters from the study site, using a hand-held auger. The samples were analyzed for heavy metals using inductively coupled plasma atomic emission spectrometry (ICP–AES, Yobin Yvon JY-24) and total petroleum hydrocarbon (TPH) using Agilent 6890N Gas Chromatography - Flame Ionization Detector (GC– FID model, Japan). Mean levels of heavy metals and TPH were higher in the study site compared to the control. The mean levels of heavy metals were 0.748 mg/kg (Pb), 0.754 mg/kg (Cd), 1.577 mg/kg (Ni), 0.274 mg/kg (Cr), 4.749 mg/kg (Fe), 0.020 mg/kg (V), 0.103 mg/kg (Co), 0.181 mg/kg (As), 5.544 mg/kg (Mn), and 5.187 mg/kg (TPH). The heavy metals in the soil had an increasing sequence of V<Co<As<Cr<Pb<Cd<Ni<Fe<Mn. The soil recorded the Cd, Cr, Fe, V, and As levels above the WHO permissible limits for soil. Ecological risk assessment revealed that Cd had the highest contamination (Cif) (91.47%) and ecological factor (Eir) (99.29%) in the soil, denoting that Cd contributed the most to the ecological instability and contamination of the soil. Co-relation, principal component analysis (PCA), and coefficient of variation (CV) revealed that Pb, Cd, Ni, Cr, Fe, V, As, Mn, and TPH were introduced into the soil through the crude oil spill (artificial sources), while Co originated from natural sources. A thorough clean-up of the spill site is therefore recommended to ecologically restore the soil. More of similar studies are required in other crude oil impacted soils in Niger Delta, Nigeria.
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