Ecotoxicological risk assessment of heavy metals from remediated oil spill site in Niger Delta region, Nigeria
Omobolaji O. Afolabi, O. M. Adesope
Abstract
Ecotoxicological risk assessment studies provide information about environmental risk and the magnitude of such risk for further action when necessary. The study assessed the ecotoxicological risk of heavy metals (HMs)- Lead (Pb), Cadmium (Cd), Chromium (Cr), Nickel (Ni), Iron (Fe), and Copper (Cu)) from remediated oil spill site in Niger Delta region to establish the site contamination and ecological risk status of environmental mediums (soil and sediment) based on contamination factor (CF), enrichment factor (EF), Geo-Accumulation Index (Igeo), Pollution Load Index (PLI), Degree of Contamination Index (DCI), Risk Index (RI), and Principal Component Analysis (PCA). The mean concentration of HMs such as Pb (0.234 mg/kg), Ni (0.307 mg/kg), Fe (1.552 mg/kg), Cr (0.299 mg/kg) and Cd (0.004 mg/kg) exceeded the allowable limit of World Health Organization while Cu (0.527 mg/kg) was within the WHO limit. The contamination status indicated a low CF, zero EF, no pollution of heavy metals, and very low DCI. The ecological risk estimation of soil and sediment indicated low RI for both soil and sediment and trend as RIsoil: Cd (0.72) > Fe (0.1) > Ni (0.075) > Pb (0.06) > Cu (0.02) > Cr (0.018) and RIBs: Cd (2.01) > Ni (0.085) > Pb (0.075) > Fe (0.041) > Cu (0.01) > Cr (0.0018). The PCA revealed a strong correlation among many of the HMs suggested common sources and distribution patterns, while the negative and weak correlation of Cd and Fe with other HMs suggested other sources of the metals other than the anthropogenic sources. Therefore, the HMs in the environmental mediums were deemed contaminated and can be fit for human use in the coming years.