Ecological Risk Assessment of Heavy Metals in Soils of Biseni, South-South Nigeria

Abstract

Heavy metals are natural constituents of the environment. However, when such
heavy metals occur in significantly high concentrations exceeding acceptable
limits, they become toxic and harmful to both human health and ecological
balance. This study was aimed investigating the concentration levels and
distribution patterns of selected heavy metals in soils around Biseni in Yenagoa.
Five heavy metals – cadmium (Cd), copper (Cu), iron (Fe), nickel (Ni) and lead
(Pb) – were the focus of the present study. Geochemical determination of heavy
metals concentrations was carried out using the atomic absorption
spectrophotometry (AAS) technique. The heavy metals were randomly
distributed with the mean concentrations in the order of Cu > Ni > Cd > Fe >Pb.
The specific ranges of the concentrations of the heavy metals in the soil are Cd (<
0.001 mg/kg – < 3.045mg/kg), Cu (0.946mg/kg – 4.680 mg/kg), Fe (o.542 mg.kg –
2.876 mg/kg), Ni (< 0.001 mg/kg – 3.849 mg/kg) and Pb (< 0.001 mg/kg – 0.008
mg/kg). The study revealed that heavy metals concentrations in some of the
sampled soils exceed the World Health Organization (WHO) recommended
maximum permissible limits of Cd, Ni and Cu whereas the observed Pb and Fe
concentrations in the soils were well within the acceptable limits. It is inferred
that the significantly high concentrations of Cd, Ni and Cu in the soils is as a
result of human activities in the area, particularly hydrocarbons exploration and
exploitation. In view of the observed random distribution relatively toxic
concentrations of some of the heavy metals in the soils in Biseni, it is
recommended that appropriate remediation efforts and strategies be adopted
even as more detailed, periodic assessment and reassessment of heavy metals
studies on the environment in the area are recommended.