DETERMINATION OF THE LEVELS OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHs) AND HEAVY METALS IN SOILS AND PLANT FOOD CULTIVARS FROM SOME OIL EXPLORATION COMMUNITIES OF BAYELSA STATE.

AUTHOR: IFEMEJE, JONATHAN CHINENYE

DEPARTMENT: APPLIED BIOCHEMISTRY

AFFILIATION: NNAMDI AZIKIWE UNIVERSITY, AWKA

Soils and vegetation in three selected communities in Bayelsa state were investigated for presence of recalcitrant Polycyclic aromatic hydrocarbons (PAHs) and heavy metals in the soils and edible plant food cultivars. Two of the communities, Angiama and Oporoma are crude oil impacted areas having had oil spillage accidents in 2010 and 2008 respectively while Yenagoa a non crude oil impacted area is used as control. Physicochemical properties of soils from these study areas were investigated using standard methods, the polycyclic aromatic hydrocarbon (PAHs) in the soil and food cultivars were determined using Gas Chromatography – Mass Spectrophotometer while heavy metals were analysed by Atomic Absorption Spectrophotometer. The result of the investigation reveal that oil spillage degrades the soil as revealed by the significant reduction in pH , moisture content and bulk density of soils from Angiama and Oporoma communities compared with Yenagoa. Soil from Angiama had the highest percentage (%) organic carbon (4.40±0.53%) and total hydrocarbon (846.40±10.11mg/kg) followed by Oporoma (2.13±0.12% and 520.00±5.00mg/kg respectively) and Yenagoa (1.30±1.08% and 62.20±0.26mg/kg respectively). The anion levels of soil nitrate (NO32-) and phosphate (PO43-) were significantly highest in soil residues from Yenagoa than in Angiama and Oporoma while the levels of exchangeable cations (Ca2+, Mg2+, K+,and Na+) were highest in Angiama than in Oporoma and Yenagoa soils. The values were significantly different at p<0.05.This suggest that exchangeable cations accompany oil spill. High molecular weight recalcitrant PAHs Benzo(a) pyrene, benzo(a) anthracene, Benzo(K) fluoranthene, Benzo(b)fluoranthene were present in both Angiama and Oporoma soil but were not detected in Yenagoa. Except for phenanthrene, low molecular weight PAHs were not detected in soil samples from Yenagoa, occurred sparingly in Oporoma but were predominant in Angiama. Food cultivars from both Angiama and Oporoma were equally proportionately contaminated with these high molecular weight PAHs. The leafy vegetables (pumpkin and scent leaf) were far more contaminated than the tubers (yam and cassava). Heavy metal contaminants of soils and food cultivars mirror exactly the same trend associated with recalcitrant PAHs. These results reveal that oil spillage activity is responsible for the preponderance of PAHs and heavy metals in the soils of the Niger Delta. It also demonstrates that by the process of natural weathering polluted soils are remedied over time. Given the appreciable accumulation of these crude fraction toxicants in food cultivars, it is suggested that the foods remain a major endogenous source of PAHs and heavy metals among the people of the area.

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