Heavy metal pollution and ecological geochemistry of soil impacted by activities of oil industry in the Niger Delta, Nigeria

摘要

The aim of the study was to assess the metal pollution of the soil around two crude oil flow stations in the Niger Delta, Nigeria and perform the ecological geochemistry of soil. Soil samples were collected by systematic random sampling around the flow stations in Kokori and Kolo Creek, Niger Delta Nigeria. The concentrations of Zn, Pb, Ni, Cr and Cd in the soil were determined by Atomic Absorption Spectrophotometry after wet-digestion in acid mixture of HNO3+ HCl + H2O2. Mean concentration values of Zn, Pb, Ni, Cr, and Cd in the soil of both Kokori and Kolo Creek were higher in some cases by several orders of magnitude than the Control values except for Ni in Kokori and Pb in Kolo Creek. The levels of Index of geo-accumulation (I-geo) were no pollution to low pollution except Cr in Kolo Creek that indicates strong pollution. Nemerow integrated pollution index (NIPI) also indicates the soil of Kokori and Kolo Creek to be of moderate and high levels of pollution respectively with Zn majorly contributing to the pollution status in Kokori while Cr, Zn and Ni are the major pollutants in Kolo Creek. However, a different pollution pattern was observed in the single potential ecological risk assessment of metals in the soil. Cd and Cr in Kokori and Cr, Cd and Ni in Kolo Creek portend ecological risk with the following patterns; Cd = Cr > Zn = Pb = Ni and Cr > Cd = Ni > Zn = Pb respectively. Comprehensive potential ecological risk (RI) assessment indicated low potential ecological risk for Kokori and Kolo Creek; and the major contributors are Cd, Ni and Cr. Therefore, there is urgent need to remediate these metals that could pose ecological risk so that further buildup would be prevented, and avert any potential harm to ecological functioning of the areas.