Evaluation of Radioactivity Concentration and Radiological Impact for a Closed Open Pit Gold Mine
DOI:
https://doi.org/10.15392/2319-0612.2025.2548Keywords:
Terrestrial radiation, external radiation exposure, gamma ray spectrometer, Closed Gold MineAbstract
Evaluating radioactivity concentration and radiological impacts in soil, water and air is essential for both operating and closed gold mines, as geological settings, mining, industrial and agricultural activities can increase the natural occurring radioactivity level. The assessment is critical since the presence of radioactive elements can pose significant health risks and social problems. While most studies focus on active mining operations, this study targets the radioactivity concentration and radiological impact due to exposure of radionuclides of 232Th, 226Ra, and 40K for the closed open pit gold mine located in Nzega, Tanzania. In this study, gamma spectrometry was used for radioactivity evaluation and radiological impact assessment. The results indicated that, the activity concentration levels of 232Th radionuclides range from 17.4±2.4 to 133±13 Bq/kg, with an average value of 42.1±4.4 Bq/kg. The activity levels of 226Ra radionuclides range from 13.1±1.6 to 308±28 Bq/kg, with an average value of 82.8±7.9 Bq/kg, and the activity levels of and 40K radionuclides range from 101±15 to 1,119±103, with an average value of 461±45 Bq/kg. These activity concentrations were found to be above those mean values reported by UNSCEAR 2000 of 30, 35, and 400 Bq/kg for 232Th, 226Ra, and 40K, respectively, for natural radionuclides in soils. The radiological parameters calculated from the activity concentration were below the acceptable limit. The mean annual effective dose of 0.5 mSv/Year was below the ICRP recommended limit of 1.0 mSv/Year for members of general public. The average value of radium equivalent activity was 178.4 Bq/kg. The estimated average values of Hex (0.4) and Hin (0.7) in the study area were both below the desirable limit of 1. However, the radiological parameters at Re-handle were above the public limit and this requires mitigation measures. It can be concluded that no risk may threat the residents around study area except for Re-handle area which we recommends continued monitoring of radiation levels to ensure they remain within safe limits, and restricted access to this area is necessary to safeguard public health and environmental integrity.
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