Possible alterations in the distribution and composition of total petroleum hydrocarbon (TPH), polycyclic aromatic hydrocarbons (PAHs), and benzene, toluene, ethyl benzene, and xylene isomers (BTEX) in the released oil at Idu-Ekpeye in Niger Delta (Nigeria) were studied within two seasonal variations of two months and six months, with a view to assessing the level of attenuation of these hydrocarbons in impacted soils. Although there were significant contaminations in the kerosene range (n-C10-n-C14) two months after, especially of the n-C12 and n-C13 fractions, the complete disappearance of the n-C8 to n-C23 hydrocarbons, including the acyclic isoprenoids (pristane and phytane), and the reduced amounts of PAHs, and BTEX, six months after, provided substantial evidence of attenuation as indicated in the reduction in total hydrocarbon content (THC) from 61.17 to 42.86%. Soil physicochemical properties such as pH, moisture content, heavy metal, TOC, and TOM, all provided corroborative evidence of hydrocarbon attenuation. The pristane/phytane ratio of the spill samples suggests that the spilled oil was genetically oxic.
Static tests were employed to assess the acute toxicity of the water-soluble fraction (WSF) of spent automotive lubricating oil (of mixed SAE grades) on Clarias gariepinus, a freshwater fish commonly cultured in Nigeria. Median lethal concentrations (LC50) of the WSF were found to decrease as a function of exposure time from 690+/-21 (after 24 h) to 513+/-58 mg/l (after 96 h). The characteristics of the WSF such as mean acidity (pH 6.6), turbidity (40 NTU), total dissolved solids (TDS; 40 mg/l) and significantly reduced (P<0.05) dissolved-oxygen (DO) values (1.44 mg/l) were not compliant with existing standards set for discharged effluents. The solubility of the detected straight-chain aliphatics ranked as C14>C16>C32>C18>C28; that of the simple aromatics was ortho-xylene>para-xylene; and that of the polyaromatic hydrocarbons (PAHs) was acenaphthylene>9H-fluorene>naphthalene>anthracene>phenanthrene>chrysene>benzo[k]fluoranthene>benzo[a]pyrene>benzo[b]fluoranthene, most of which being serious carcinogens. These oil constituents and the overall physico-chemical properties of the WSF are expected to act synergistically on the test organism (C. gariepinus), eliciting the quantal responses observed. The toxicity of the WSF points to the base constituent, oxidative degradation, and mechano-chemical reactions associated with aged crankcase oils. These oils, therefore, should definitely no longer be disposed into water streams or landscape, not even at sub-lethal concentrations, because of the inherent toxicity of their soluble fractions and the associated danger of bioaccumulation.
This article was inspired by a field reconnaissance survey of outcrops along the Nembe-Brass axis of the petroliferous Niger Delta. It reviews various tradeoffs of the impact of upstream petroleum (seismic and production) operations on the mangrove ecosystems in that region, the largest in Sub-Saharan Africa. Mangroves and intertidal shores are considered critical to the economic well-being of this region owing to the people's dual occupation in fishing and farming. The mangrove ecosystem provides a nutrient medium, which serves as a nursery and spawning ground for many fish species and other biota. Oil and gas activities might destroy these spawn areas, causing reduction in resource output and community pressure. Devegetation of the mangrove forest as a result of seismic delineation leaves the fragile soil exposed, unprotected, and susceptible to erosion. Again, loss of vegetation might discourage the natural role of plants in air purification (CO(2) utilization and O(2) production). The release of nutrients (organic N(2), NH(3), and NO$\rm{{_{3};{-}}}$) and polyaromatic hydrocarbons (PAHs) to the environment, with the attendant increase in microbial load, increases biochemical O(2) demand (BOD) and depletes dissolved O(2) (DO) in H(2)O to a level that is beyond the tolerance limit of organisms. This anoxic situation leads to asphyxiation and subsequent fish kill in affected areas. In order of increasing vulnerability, the mangroves and intertidal shores of the Niger Delta fall under categories 8 to 10 on the environmental sensitivity index (ESI) scale, which predisposes the areas to serious long-term effects and clean-up complexity. Thus, there is need to monitor mangrove systems and shoreline changes in the areas of considerable seismic and production activities, especially in the coastal Niger Delta, where pipeline corrosion due to salt intrusion into the swampy environment and 'unsighted fingers' of sabotage have increased the prevalence of oil spills.
Oil exploration, exploitation, oil well fires and pipe-line vandalism are often reported to lead to high levels of pollution of the environment affecting water, land and air. As a result, the safety of specific fish species for human consumption is constantly in doubt and needs assessment. Guinean tilapia (Tilapia guineensis) and Blackchin tilapia (Sarotherondon melanotheron) are two of the highly consumed fish species in Bodo River. The level of chromium, nickel, cobalt and zinc in the flesh of Tilapia guineensis and Sarotherondon melanotheron found in Bodo River were studied using X-ray fluorescence (XRF). The amount of chromium found in the two fish species ranged between 10.3-10.5mg/kg, nickel 8.7-10.2mg/kg, cobalt 3.0-4mg/kg and zinc 71.2-74.5mg/kg. The levels of Cr, Ni, Co and Zn found in these two species of fish were compared to WHO maximum permissible levels of fish for consumption. The results showed that, fish from the study area contain amount of these metals investigated. This result will serve as a baseline for Food Agencies in Nigeria to certify safety of fishes from various rivers before they are sold for consumption to the public is hereby highlighted. © JASEM http://dx.doi.org/10.4314/jasem.v20i3.9
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