Ecological risk assessment of heavy metals in road side soils of Onitsha South Local Government Area, Anambra Nigeria

K. E. Ochiagha, P. A. C. Okoye, N. C. Eboagu

Abstract: The concentrations of heavy metals (Mn, Ni, Cr, Cu, Zn, Pb and Fe) in the soils of Onitsha South Local Government area of Anambra Nigeria were investigated and the potential ecological risk of heavy metals pollution evaluated. Atomic Absorption Spectrophotometer (AAS) was employed to analyze the heavy metals concentrations in the studied area. Lars Hakanson’s potential ecological hazards index method was used to evaluate the heavy metals potential ecological risk in soils. The results from heavy metal concentration revealed that average concentrations of the metals investigated were as follows: Mn 1.39 mgkg^-1, Ni 1.24 mgkg^-1, Zn 1.24mgkg^-1, Cr 9.08 mgkg^-1 , Cu 0.80mgkg^-1,Pb 0.52mgkg^-1and Fe 96.37mgkg^-1 in the wet season while the following average values were recorded in dry season: Mn 1.60mgkg^-1, Ni 1.83mgkg^-1, Zn 2.45mgkg^-1, Cr 11.54mgkg^-1, Cu 1.22mgkg^-1, Pb 0.50mgkg^-1 and Fe 143.54mgkg^-1. The concentrations of Fe in the soils were relatively high (96.368- 143.54 mgkg^-1) for both seasons. The values obtained from the heavy metals concentrations with the exception of Cr and Fe revealed that the soils were not heavily contaminated by these heavy metals. Based on Lars Hakanson’s potential ecological index method, Cr had considerable ecological risk in soils in the wet season with location 8 had highest risk while in the dry season Cr moderately polluted the area with location 7 having considerable ecological risk. The other heavy metals had slight ecological risk. Ecological risk of total heavy metals pollution was moderate. Correlation analysis suggest that heavy metals pollution source for Mn, Ni, Pb, Cr, Cu, and Zn may be mainly derived from metal processing, electroplating industries, industrial wastewater, agricultural activities and domestic sewage.