Abstract
Concentrations of selected heavy metals, nutrient elements and PAHs in farms and produce (cassava tubers and oil bean seeds) from 4-year-old crude oil impacted areas (Ekore and Uduvwoku) and a non-oil-impacted area (Okpe), all in Ughelli South Local Government Area, Delta State, Nigeria, were investigated to ascertain degree of risk posed. A random sampling design was chosen with three replications. Results obtained revealed significantly (P < 0.05) elevated (mg·kg-1) Cd (0.240, 0.140) and Cr (1.327, 3.122) in cassava samples for Ekore and Uduvwoku respectively in comparison to non-detectable amount for those of non-impacted source and exceeded set WHO limits of 0.1 and 0.05 mg·kg-1 respectively. Although PAHs were low, oil spill increased available levels by factor of 2.5 and 5 for Ekore and Uduvwoku respectively. Again, Cd and Cr exceeded WHO limit for study impacted soils. Available N, P and K decreased (%) by 56.1, 28.5 and 2.4 for Ekore and 82.9, 39.9 and 45.5 for Uduvwoku Cassava samples. Nutrient profiling in oil bean revealed % reduction in avaliable N, P and K by 33.7, 47.7 and 57.9 and 28.9, 76.3 and 39.8 for Ekore and Uduvwoku samples respectively. For oil bean, Cd and Cr did not differ markedly between polluted samples but exceeded WHO limits. Other studied contaminants fell within limits. In soils, available N, P and K decreased (%) by 39.6, 79.1 and 27.4 for Ekore and 53, 88.1 and 45.5 for Uduvwoku samples. Low pH of 5.3 and 5.7 in Ekore and Uduvwoku respectively may increase the leachability of Cr into groundwater. Biopersistent Cd and Cr were found to biomagnify up the food chain and may impair major processes. Although PAHs were relatively low, their % composition was more of High Molecular Weight that was less readily biodegraded by indigenous microorganisms, and hence can persist in the environment as carcinogens.
Highlights
The emergence of oil as the world’s leading fuel was partly due to its relative cleanliness but the enormous scale of the petroleum industry’s operation has inevitably created a new set of difficult environmental problems as being experienced today in the Niger Delta region of Nigeria [1]-[3]
polycyclic aromatic hydrocarbons (PAHs) were relatively low, their % composition was more of High Molecular Weight that was less readily biodegraded by indigenous microorganisms, and can persist in the environment as carcinogens
With the myriads of industries located in the Niger Delta region, it is a thing of interest to investigate the level of heavy metals and PAH distribution in crops grown around these areas
Summary
The emergence of oil as the world’s leading fuel was partly due to its relative cleanliness but the enormous scale of the petroleum industry’s operation has inevitably created a new set of difficult environmental problems as being experienced today in the Niger Delta region of Nigeria [1]-[3]. Food crops grown on contaminated soils take up heavy metals and polycyclic aromatic hydrocarbons and accumulate them in their tissues. This research aims to evaluate the levels of polycyclic aromatic hydrocarbons and selected heavy metals in crude oil polluted soils and major crops grown on such soils in Ughevwughe community. This will provide baseline information on the level of risk faced by the people living within that region and for clean-up design
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