Extractable Hydrocarbons, Nickel and Vanadium Contents of Ogbodo-Isiokpo Oil Spill Polluted Soils in Niger Delta, Nigeria |
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Authors: | Leo C Osuji Samuel O Adesiyan |
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Institution: | (1) Department of Industrial & Pure Chemistry, University of Port Harcourt, Choba Port Harcourt, Nigeria;(2) Department of Crop Protection and Environmental Biology, University of Ibadan, Nigeria |
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Abstract: | An oil spill polluted site at Ogbodo-Isiokpo in Ikwere Local Government Area of Rivers State in southern Nigeria, was identified
for study following three successive reconnaissance surveys of oil fields in the Agbada west plain of Eastern Niger Delta.
A sampling area of 200 m × 200 m was delimited at the oil spill impacted site using the grid technique and soils were collected
at surface (0–15 cm) and subsurface (15–30 cm) depths from three replicate quadrats. A geographically similar, unaffected
area, located 50 m adjacent to the polluted site, was chosen as a control (reference) site. Total extractable hydrocarbon
contents of the polluted soils ranged from 3.02–4.54 and 1.60–4.20 mg/kg (no overlap in standard errors) at surface and subsurface
depths respectively. The concentrations of two “diagnostic” trace heavy metals, nickel (Ni) and vanadium (V), which are normal
constituents of crude oil, were also determined in the soils by atomic absorption spectrophotometric method after pre-extraction
of cations with dithionite–citrate carbonate. Ni varied from 0.15 to 1.65 mg/kg in the polluted plots and from 0.18 to 0.82
mg/kg in the unpolluted plots; vanadium varied from 0.19 to 0.70 mg/kg in the polluted plots and from 0.14 to 0.38 mg/kg in
the unpolluted plots. Ni and V were more enhanced (p < 0.05) in the oil-polluted soils, especially at subsurface depth. Whilst the oil spillage could be said to be indirectly
responsible for the enhanced concentrations of nickel and vanadium via the injection and availability of the petroleum hydrocarbons
that might have increased the activities of biodegradation on site, the physico-chemical properties of the soils and inherent
mobility of metals, as well as the intense rainfall and flooding that characterized the period of study, may have also contributed,
at least in part, to these enhanced concentrations. Such levels of Ni and V may result to enhanced absorption by plants, which
may bring about possible bioaccumulation in such plants and the animals that depend on them for survival and all of these
may lead to toxic reactions along the food chain. |
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Keywords: | crude oil hydrocarbon nickel Niger Delta oil spill polluted soils vanadium |
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