Mapping of radioactivity levels in and around the gold mine tailing dams of Gauteng Province, South Africa

Abstract

Naturally occurring radionuclides arises mainly from natural sources and anthropogenic activities such as mining. In South Africa, gold mining in the goldfields of the Witwatersrand Basin has resulted in numerous tailing dams that have high concentrations of NORM bearing residue. The aim of this study was to evaluate the surface radioactivity levels in and around the gold tailing dams of Gauteng Province in South Africa and further determine the consequential radiological exposure to the public. The portable BGO SUPER-SPEC (RS-230) spectrometer, with a 6.3 cubic inches Bismuth Germanate Oxide (BGO) detector was used to measure the activity concentrations for 238U, 232Th and 40K in mine tailings, soils and underlying rocks. This work was conducted on a regional scale and covered the West Rand, East Rand and Central Rand Districts of the Gauteng Province, which are dominated by the abandoned gold tailings dams. Of the three radionuclides that were studied, 238U was found to be the most significant radioactive contaminant of radiological concern. High 238U concentrations (209.95 to 2578.68 Bq/kg) were found in the mine tailings than in the surrounding soils (9.88 to 941.07 Bq/kg) and rocks (11.12 to 71.63 Bq/kg). In surface soil, the radionuclides show significant spatial variability with high activities recorded in soils located in close proximity to tailings thus signifying the adverse environmental impacts of mining in the study area. The annual effective dose estimations indicate that the mine tailings found in the area and soils impacted by tailings significantly contribute to the external gamma radiation received by members of the public. This therefore highlight the need for further monitoring and regulatory control measures targeting these affected areas, in order to ensure the protection of persons and the environment within the areas.Keywords: activity concentration; gold mine tailings; in situ gamma ray spectrometry; radiologicalexposures; South Africa