Assessment of Polycyclic Aromatic Hydrocarbons (Pahs) And Heavy Metals Contaminations in Surface Water and Sediments of Oil Impacted Rivers in Khana LGA, Rivers State, Nigeria

Abstract

The Niger Delta region of Nigeria is highly vulnerable to environmental pollution due to extensive oil exploration and industrial activities, resulting in the contamination of aquatic ecosystems with heavy metals and polycyclic aromatic hydrocarbons (PAHs). This study assessed the concentrations of heavy metals and PAHs in surface water and sediments of the Khana LGA, Rivers, Rivers State, to evaluate potential ecological and human health risks. Surface water and sediment samples were collected from selected sampling stations within rivers in Zaakpon, Kaani, and Bane communities in Gikana LGA and analyzed using standard physicochemical and spectroscopic techniques, including Atomic Absorption Spectroscopy (AAS) for heavy metals and Gas Chromatography-Mass Spectrometry (GC-MS) for PAHs. Results indicated that the mean concentrations of heavy metals in surface water were Pb (0.285 ± 0.019 mg/L), Cd (0.013 ± 0.004 mg/L), Cr (0.044 ± 0.005 mg/L), and Fe (1.894 ± 0.196 mg/L), with several exceeding WHO and NSDWQ limits. Sediment samples exhibited higher metal accumulation, with Cu (14.771 ± 1.074 mg/kg), Pb (29.279 ± 3.161 mg/kg), Fe (1826.925 ± 10.798 mg/kg), and Zn (136.356 ± 6.317 mg/kg), indicating sediments act as long-term sinks for metal pollutants. For PAHs, total concentrations in water ranged from 0.167 to 1.256 mg/L (mean: 0.477 ± 0.075 mg/L), with carcinogenic PAHs (∑cPAHs) at 0.121 ± 0.024 mg/L, exceeding WHO and USEPA guidelines. Sediment PAH concentrations were substantially higher, ranging from 6.994 to 20.178 mg/kg (mean: 11.866 ± 1.274 mg/kg), with both low and high molecular weight PAHs present, reflecting mixed petrogenic and pyrogenic sources. The study concludes that the Khana Rivers are heavily contaminated with both heavy metals and PAHs, posing serious environmental and human health risks. Urgent interventions are recommended, including continuous monitoring of water quality, enforcement of environmental regulations, remediation of polluted sediments, and community awareness programs to mitigate exposure to toxic contaminants. The findings provide a crucial baseline for future ecological risk assessment and pollution management in oil-impacted riverine systems of the Niger Delta.