EVALUATION OF TOXIC METALS POLLUTION IN SOILS FROM ABANDONED COAL MINES USING POLLUTION INDICES: A CASE STUDY OF ENUGU COAL MINES, SOUTHEASTERN, NIGERIA
Keywords:Abandoned coal mines, Enugu State, Heavy metal, Multivariate statistics, Pollution indices
Due to human mediated activity such as mining and other industrial activities, soil pollution problems from potentially hazardous heavy metals have become an environmental concern in recent years. To evaluate heavy metal pollution of soils from abandoned coal mines in Enugu, we analyzed pollution and possible environmental risk, contrasted hazardous metal contents between soils from abandoned coal mine and soils from non-mining areas and established the link between the toxic metals on a broad scale. For the purpose of this study, 30 soil samples from and around abandoned coal mines and 10 soil samples from non-mining area were collected and analyzed for As, Cr, Ni, Fe3+, Pb, Mn, Zn, Cd and Cu in the laboratory using atomic absorption spectrometry (AAS). Abandoned coal mines referred in current study are Onyeama, Okpara, Ribadu, and Iva Valley coal mines. Approaches such as Index of geoaccumulation (Igeo), Nemerow pollution index (P), potential environmental risk index and other statistics were used. Compared with soils from non-mining areas, heavy metal contents in soils from abandoned coal mines were much higher. For pollution indices, higher Igeo for As, Pb and Cr was ascertained. Soils were polluted or mildly polluted when estimated as per WHO/FAO and FEPA respectively but mildly polluted or heavily polluted when estimated as per background values. Majority of the metals (Fe3+, Cd, Mn, Cu, Ni and Zn) showed a low potential ecological risk, whereas As, Pb and Cr revealed mildly higher potential environmental risk. Based on correlation matrix performed, high positive correlations were found in pairs of Pb/As, Pb/Fe3+, As/Mn, Zn/Fe3+, As/Cr and Cd/Ni (P < 0.01) and Cu/Cr (P < 0.05).