Extractable Hydrocarbons, Nickel and Vanadium Contents of Ogbodo-Isiokpo Oil Spill Polluted Soils in Niger Delta, Nigeria

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 x 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.

Conflicts – Oil Exploration and Water

“…Nigeria brands of crude oil are known to contain relatively high concentrations of some heavy metals . For Nigeria's dominant ‘sweet’ crude oil, Bonny Light, the associated heavy metals occur in the order nickel>vanadium>cadmium>copper>lead . High concentrations of barium, lead and cadmium, above WHO permissible limits were recorded in borehole and open hand‐dug well waters in the Western Niger Delta, which the authors attributed to oil exploration and processing activities.…”

“…[61] For Nigeria's dominant 'sweet' crude oil, Bonny Light, the associated heavy metals occur in the order nickel>vanadium>cadmium>copper> lead. [62] High concentrations of barium, lead and cadmium, above WHO permissible limits [58] were recorded in borehole and open hand-dug well waters in the Western Niger Delta, [63] which the authors attributed to oil exploration and processing activities. They studied levels of heavy metals-cadmium, chromium, copper, iron, nickel and lead-analyzed in the River Ijana, which receives petroleum effluents from the Warri Refinery, Western Niger Delta and reported concentrations generally above WHO standards recommended for surface waters.…”

Peripheral axonopathy in sciatic nerve of adult Wistar rats following exposure to vanadium

“…Nigeria is currently ranked the seventh highest gas flaring country in the world; a seeming improvement on previous rankings (second position) she once held as at 2010 . However, considering the volume of gas flared per land mass of the country, gas flaring remains a major environmental and epidemiological concern in Nigeria, whose crude oil is known to be rich in vanadium . These flares release vanadium in its gaseous form, vanadium pentoxide, making it easier to gain access to the body system through the inhalational route and thus exerting its toxic effects on a variety of biological systems .…”

“…[3][4][5] However, considering the volume of gas flared per land mass of the country, gas flaring remains a major environmental and epidemiological concern in Nigeria, whose crude oil is known to be rich in vanadium. 6 These flares release vanadium in its gaseous form, vanadium pentoxide, making it easier to gain access to the body system through the inhalational route 7 and thus exerting its toxic effects on a variety of biological systems. 8 Some of the vanadium-induced pathologies reported on various organ systems include: the lungs, liver, spleen, and testes, 9,10 haematological and biochemical alterations 11,12 and the kidneys.…”

The effects of ammonium metavanadate on biochemical hormonal, haematological and histopathological parameters of the female wistar rats

“…Vanadium is a transitional metal that exists in different oxidational states (Barceloux & Barceloux 1999) in fossil fuels, industrial and environmentally degraded areas (Osuji & Adesiyan 2005). It is also a trace element found in the catalytic distillation of crude oil.…”