Characterization and Ecotoxicological Assessment of Polycyclic Aromatic Hydrocarbons in Soils from the Niger Delta, Nigeria

Abstract

Polycyclic Aromatic Hydrocarbons (PAHs) in the environment deserve more attention because of their widespread occurrence, mutagenic, carcinogenic, and tetragenic effects. Surface soils from Ukwuani, Ndokwa, and Isoko areas of the Niger Delta were assessed for their PAH concentrations and ecotoxicity impact on the environment. The PAHs in the soils were characterized qualitatively and quantitatively using Gas Chromatography–Flame Ionization Detector (GC-FID) and the source determined by various molecular diagnostic ratios. The total concentrations of PAHs defined as ∑₇ PAHs from the locations ranged from 112.8 to 827.6 ng/g. Of the 16 priority PAHs, only seven were present in the soils. Low molecular weight (two and three rings) PAHs were dominant in the soils. Molecular diagnostic ratios of the PAHs in the soils indicated that they originated from pyrogenic sources such as gas flaring and combustion of biomass etc. The PAH species in the soils have no carcinogenic effects. PAH ecotoxicity indicators in the soils such as ERL (Effective Range Low) and ERM (Effective Range Median) revealed mild toxic effects. Six of the seven individual PAH concentrations were below the ERM, thus indicating mild to negative toxic effects. The soils have moderate pollution of PAHs compared with other studies, international standards, and guidelines. The PAH species from gas flaring and other combustion of biomass has potential health risk if ingested by plants and aquatic animals.