Radionuclide distribution and exposure doses in mine tailing dumps from the west rand gold mining region of the Gauteng province, South Africa

Mine tailing dumps are one of the prevalent environmental legacies of gold mining in the Witwatersrand Basin, which are typically enriched in Naturally Occurring Radioactive Materials (NORMs). This study aimed to evaluate radionuclide levels and the associated exposure risks from external gamma radiation in mine tailing dumps and soils near residential areas in historical mining towns of the upper West Rand region in Gauteng Province, South Africa. The activity concentrations of various radioisotopes were measured using Gamma spectrometry. The activity concentrations of 238U (87.2–449 Bq/kg), 235U (4.19–21.6 Bq/kg), 234U (88.9–458 Bq/kg), 232Th (12.3–78.1 Bq/kg), 228Th (12.5–81 Bq/kg), 228Ra (12.3–78.1 Bq/kg), 226Ra (14.5–2650 Bq/kg) and 40 K (1.89–125 Bq/kg) were highly variable in all samples. All but 226Ra activity concentrations fell below the prescribed limits of 500 Bq/kg and 50 000 Bq/kg (40 K). The presence of tailings material in some of the sampled soils signifies the extensive environmental impacts of tailings on the surrounding areas and the potential radiological risks to public health. Annual effective dose estimates ranged between 0.062 and 0.282 mSv/y, and fall far below the IAEA and NCRP’s 1 mSv/y regulatory limit, albeit most samples’ estimates exceeding UNSCEAR’s 0.08 mSv/y global average value. It is recommended that continuous monitoring of different geological materials near residential areas be established to ensure compliance with regulatory standards and the public’s protection from radiological damage. Moreover, mine tailings dumps rehabilitation is crucial to prevent further environmental contamination and lower radiological risks to public health.