The baseline assessment of radiological levels of water in the West Rand Region, Gauteng
Date
2022
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Abstract
Gold mining is one of South Africa’s economic injectors. Given South Africa’s unique geology, acid mine drainage (AMD) formed by mining activities allows for the dissolution and leaching of radionuclides into groundwater and potentially other drinking water sources under the right conditions. The aim of this study was to establish the baseline radiological levels of drinking water in the West Rand region of the Gauteng Province, South Africa. 23 water samples were collected from 9 towns within the study area and a liquid scintillation counter and Liquid Water Isotopes Analyzer (LIWA) model 45-EP were used for the analysis of tritium and stable isotopes respectively. Moreover, alpha spectrometry was employed for radionuclide analysis. Gross-α and gross-β activity concentrations were measured to determine the composition of radionuclides and identify the dominant radionuclides. The lowest activity concentration results reported were 15.3 mBq/L, 0.218 mBq/L, 4.73 mBq/L for uranium isotopes (234U, 235U, 238U); 2.28 mBq/L, 4.73 mBq/L, 18 mBq/L, 2.71 mBq/L for thorium isotopes (227Th, 228Th, 230Th, 232Th); -9.8 mBq/L, -34 mBq/L, -6.4 mBq/L for radium isotopes ( 223Ra, 224Ra, 226Ra); 1.2 mBq/L 210Pb, -16 mBq/L and -1100 mBq/L gross-α and gross-β respectively.. The highest activity concentrations reported were 210 mBq/L, 2.85 mBq/L, 62.0 for uranium isotopes (234U, 235U, 238U); 50.5 mBq/L, 33 mBq/L, 86.4 mBq/L and 23.5 mBq/L for thorium isotopes (227Th, 228Th, 230Th, 232Th); 13 mBq/L, 25 mBq/L and 19.5 mBq/L for radium isotopes (223Ra, 224Ra, 226Ra); 135 mBq/L 210Pb; 341 mBq/L and 13500 mBq/L for gross-α and gross-β respectively. The effective dose calculated from activity concentrations of all samples was within the allowed range (1 mSv/L to 3 mSv/L) of the WHO, UNSCEAR and DWAF drinking water guidelines. The low activity concentrations measured from the radionuclides suggest that the consumption of groundwater within the study area poses very little threat to human health but may cause severe health effects if it accumulates in the human body. The environmental isotopes results showed multiple moisture sources from global circulation, depleted δ 18O and δ 2H (-6.9‰ and -32.2‰, respectively) indicating that the recharging water underwent evaporation prior to recharge. Tritium was used to estimate the groundwater residence times and its activity concentration ranged from 9.44 to 28.32 mBq/L. Low 3H activity concentrations are indicative of new to relatively young waters.
Description
A dissertation submitted in fulfilment of the requirements for the degree of Master of Science in Hydrogeology to the Faculty of Science, School of Geosciences, University of the Witwatersrand, Johannesburg, 2022
Keywords
Gold mining, Radiological assessment, Stable isotopes