Survey of natural and artificial radioactivity in Tunisian soils

A study of the natural radioactivity and artificial radioactivity of soils due to gamma ray emitters was performed in Tunisia, as part of the national programme for environment surveillance. Seventeen sites were studied. The determination of radionuclide specific concentrations in the soil samples (0–5 cm) by gamma ray spectrometry showed the following ranges: 40K (93–319 Bq/kg), 226Ra (5–50 Bq/kg) and 232Th (5–30 Bq/kg) and 137Cs (1–19 Bq/kg). From the measured concentrations we estimated the gamma dose rates due to each radionuclide, and the calculated dose rates (8–32 nGy/h) corresponding to the terrestrial component were compared to the total external dose rates measured in air, by a sensitive scintillometer (42 and 101 nGy/h). The differences between calculated and measured dose rates may be explained partially by the cosmic component. The results of equivalent dose (0.2–0.54 mSv/y) showed a median value of 0.41 mSv/y for residents in the meteorological stations adjacent to the sample locations.