The influence of gold mining on radioactivity of mining sites soil in Tanzania

Abstract

The activity of 226Ra, 232Th and 40K in soil samples were measured by gamma spectrometry using high purity germanium detector. The study involved 40 samples from four divisions: 10 samples each were drawn from the control area (CTR), washing area 1 (W1), washing area 2 (W2) and the mining pits (MP). Radium and Thorium were measured in highest value (80.44 and 94.62) Bq/kg, respectively at MP-9 while the lowest levels (1.56 and 0.96) Bq/kg, respectively were detected at MP-2. At W1, 40K (max. 887.5 Bq/kg) recorded the highest mean level while 232Th (mean=16.7 Bq/kg) had the lowest level. For W2, 40K (max. 1535.7 Bq/kg) recorded highest level and 232Th (mean = 8.1 Bq/kg) recorded the lowest (10.7 Bq/kg). Results further show that mean activity levels of 226Ra, 232Th and 40K from mining area were 42.5, 35.5 and 652.4Bq/kg, respectively. In comparison, the respective average activity for 40K, 226Ra, and 232Th recoded 118.4, 14.5 and 9.7 Bq/kg, respectively in control area. For the sake of assessing the suitability of building materials, hazard indices were calculated and their results were less than unity indicating that, building materials are safe. The annual gonadal equivalent dose, representative gamma index, alpha index revealed values of 484.8 µSv/y, 1.1 and 0.2, respectively. The average annual effective dose was 85.5 mSv which is about 8% greater than the world average. Results show that mining activities in Rwamagasa might be posing radiological hazard to people. Therefore, measures on radioactive materials to the miners and the surrounding community are recommended.