Distributional Coefficients and Enrichment Studies of Potentially Toxic Heavy Metals in Soils Around Itakpe Iron-Ore Mine, North Central Nigeria

Abstract

Soil samples were collected randomly but uniformly distributed around Itakpe iron-ore mines in both dry and wet seasons. Surface soils were collected from 0cm to 10cm using stainless steel augers and located using Global Positioning System (GPS). Soil samples were air-dried, sieved through 500um mesh and 1.0g digested, evaporated and analysed using Atomic Absorption Spectrometer (AAS).Five (5) geo-environmental indices were used to quantitatively evaluate the degree of soil contamination due to iron ore mining. The anthropogenic factor (AF) for both seasons revealed that all heavy metals have greater than 50% AF except for Cd in the dry season. The geo accumulation index (Igeo) for both seasons showed background concentration to unpolluted for Cu and Zn while Fe, Ni, Cdand Pb recorded moderately to very highly polluted. The pollution index (Eri), showed tiny hazard level for all the heavy metals in dry season and in wet season, Cd and Ni recorded strong hazard level while tiny hazard level were observed for Cu and Pb. The ecological pollution index for the area is strong (RI=323.25). Dry and wet season enrichment factor (EF) revealed background concentration for all the heavy metals except Fe with EF> 40 (extremely high enrichment). While contamination factor (CF) was very high for Fe in both seasons, Cu and Ni recorded considerable to very high contamination in dry season. The wet season also revealed considerable contamination for Ni and Cd; moderate to considerable contamination for Cu, Zn and Pb. The sites in both seasons have experienced various degrees of deterioration but more significant in wet season. Based on these indices, the soils around Itakpe iron-ore area has suffered significant degrees of contaminations with respect to Fe, Ni, Cd and Pb.