Radioactivity distribution in soil, rock and tailings at the Geita Gold Mine in Tanzania

Abstract

This study evaluated the activity concentrations of natural radionuclides in soil, waste rocks and tailings from the Geita gold mining site in Tanzania using high-resolution gamma spectroscopy. A total of 41 samples: 31 soil, 5 waste rock, and 5 tailing samples were collected around the mine to assess their radiological hazards. The average activity concentrations in soil were 54, 45 and 279 Bq kg-1 for 226Ra, 232Th and 40K. In contrast, tailings exhibited higher activity concentrations of 70, 36 Bq kg-1 for 226Ra and 232Th, and significantly elevated levels of 877 Bq kg-1 for 40K, while waste rocks showed intermediate values, with 66, 73 and 660 Bq kg-1 for 226Ra, 232Th and 40K respectively. Radiological hazard indices were calculated to quantify potential risks. In soil, the radium equivalent activity (Raeq) averaged 139 Bq kg-1, the annual effective dose equivalent (AEDE) was 78 μSv y-1, the annual gonadal dose equivalent (AGDE) reached 430 μSv y-1, and the excess lifetime cancer risk (ELCR) was 0.27 ×10-1. Tailings showed a Raeq of 189 Bq kg-1, AEDE of 111 μSv y-1, AGDE of 678 μSv y-1, and ELCR of 0.39 ×10- 1, while waste rocks exhibited a Raeq of 200 Bq kg-1, AEDE of 108 μSv y-1, AGDE of 642 μSv y-1, and ELCR of 0.37 ×10-3. Notably, the ELCR values for tailings and waste rocks exceeded the global average of 0.29 ×10-3, rendering them unsuitable for use as building materials. The absorbed dose rates were 69 nGy h-1 for soil, 91 nGy h-1 for tailings, and 88 nGy h-1 for waste rocks. One-way ANOVA revealed significant differences (p <0.05) among the matrices. These findings underscore the need for targeted waste management and remediation strategies to mitigate radiological health risks in the investigated mining area as well as other areas with similar characteristics.