Study of Natural Radioactivity Levels and the Associated Radiological Hazards in Soil from Ambanja City and its Surroundings, Madagascar

The aim of this present work is to investigate the natural radioactivity levels and to estimate the radiological hazards from the soil samples collected from different locations in Ambanja city and its surroundings. In total, twenty soil samples were collected. All samples were oven-dried, sieved, ground and put in appropriate sample container prior to analysis. Sample measurements have been performed by NaI(Tl) gamma spectrometry system with Scintivision software. The mean specific activities of ⁴⁰K, ²³⁸U series and ²³²Th series were (730± 141) Bq.kg^-1, (44± 10) Bq.kg^-1 and (123± 14)Bq.kg^-1 respectively. These results show that the radioactivity levels of the three natural radionuclides are not uniformly distributed in the soil, and their activities vary from one place to another.These variations canbe caused by the interaction with geological formations inthe study areas. The mean value of radium equivalent activity in the soil is lower than 370 Bq.kg^-1, meaning that this soil presents no radiological risk when used as a building material. All of the absorbed gamma dose rate is above the worldwide mean value of 57 nGy.h^-1. Regarding the annual effective dose rate, all of these values are below the maximal admissible limit of 1 mSv.year^-1. Thus, there is no significant radiological risk from the soil in this study area.