Evaluation of Trace Elemental Levels as Pollution Indicators in an Abandoned Gold Mine Dump in Ekurhuleni Area, South Africa

In the Blesbokspruit area of Ekuhurleni, South Africa, previous gold mining activities resulted in many tailings dump sites. 20 representative soil samples were used in describing the distribution of metals. The soils were very strongly acidic ranging from 3.86 to 4.34 with a low cation exchange capacity (CEC). Based on X-ray fluorescence (XRF) analysis, elemental composition of the soils revealed average values of major elements such as Na2O (0.18%), MgO (0.63%), Al2O3 (6.51%), SiO2 (81.83%), P2O5 (0.04%), SO3 (3.40%), K2O (1.98%), CaO (0.45%), TiO2 (0.51%), Cr2O3 (0.17%), MnO (0.04%), Fe2O3 (3.59%), NiO (0.04%), As2O3 (0.02%), with Rb2O and SrO falling below 0.01%. Trace metals (TM) contamination levels in the soils were evaluated using various pollution indices which revealed that over 60% of the soils were between the high degree and the ultra-high degree of contamination classes. The concentration of various trace metals varies from 860.3-862.6 mg/kg for Cr; 324.9-328.4 mg/kg for Al; 200.9-203.4 mg/kg for As; 130.1-136.2 mg/kg for Fe; 121.9-125.8 mg/kg for Pb; 27.3-30.2 mg/kg for Co; 23.8-26.8 mg/kg for Ni; 7.2-9.2 mg/kg for Ti; 7.1-9.2 mg/kg for Cd; 4.0-5.6 mg/kg for Zn and 0.1-0.6 mg/kg for Cu.