Heavy metal concentration in soil in the tailing dam vicinity of an old gold mine in Johannesburg, South Africa†
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Soil contamination with heavy metals is a serious concern to food production and human health. The present study was conducted to evaluate the impact of tailings from an old mining site on heavy metal contamination of soil. Using a GPS to map out different sites around the tailing dam, soil samples were taken from under grassland at the different sites, at depths of 15 cm and 1 m, using a shovel and handheld auger. The samples were prepared, acid digested, and analyzed for a multi-element suite by inductively coupled plasma atomic emission spectrometry. Results showed heavy metal concentration in the order of Cr > Zn > As > Mn > Cu > Pb > Ni > Sr > Hg. Most of the soil samples contained high concentration of As (13.46–234.6 mg kg−1). Soil concentrations of As, Hg, Cr, and Mn also decreased with distance from the dump material. Single contamination index of each pollutant, calculated according to the South African Soil Quality Standards revealed very high and medium pollution grades for As (index = 7.39) and Cr (index = 2.16), respectively. Arsenic is a metal associated with gold ore and soil pollution by such metals can make it infertile and unsuitable for plants.