Concentrations, Human and Ecological Risks of Metals in Soils in the Vicinity of Asphalt Plants in Delta States, Nigeria

The concentrations of metals, cadmium (Cd), lead (Pb), chromium (Cr), nickel (Ni), copper (Cu), cobalt (Co), iron (Fe), manganese (Mn) and zinc (Zn) were measured in soil profiles in the vicinity of asphalt plants in Delta State, Nigeria by atomic absorption spectrometry after acid digestion. The concentrations of the metals in all depths and distances from the asphalt plants ranged from 0.07 to 0.58 mg kg^-1 for Cd; 37.1 to 177 mg kg^-1 for Cr; 2.0 to 31.1 mg kg^-1 for Cu; 2.0 to 11.1 mg kg^-1 for Co; 20 to 143 mg kg^-1 for Ni. The concentrations of metals in these sites were below the Department of Petroleum Resources maximum allowed values of metals in soils, except for Ni and Cr. The estimated contamination/pollution index indicates that the examined sites fall into slight to severe pollution ranges with a significant contribution from Cr and Ni. The total ecological risk (RI) values of metals in these soil profiles were 150 which suggested low ecological risks for these soils. However, the total cancer risk of metals in these soil profiles exceeded the target value of (1/10^6) one in a million chance of developing cancer.