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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. [ABSTRACT FROM AUTHOR]

Presents an abstract of a study on the natural and artificial radioactivity of soils due to gamma ray emitters in Tunisia. Method used to determine the radionuclide specific concentrations in the soil samples; Equipment used to measure the total external dose rates in air; Way to explain the differences between calculated and measured dose rates.

Abstract: Radioactivity measurements were carried out in 26 groundwater samples from Tunisia. Activity concentrations of uranium were studied by radiochemical separation procedures followed by alpha spectrometry and that for radium isotopes by gamma-ray spectrometry. The results show that, the concentrations in water samples range from 1.2 to 69mBq/L.1, 1.3 to 153.4mBq/L, 2.0 to 1630.0mBq/L and 2.0 to 1032.0mBq/L for 238U, 234U, 226Ra and 228Ra, respectively. The U and Ra activity concentrations are low and similar to those published for other regions in the world. The natural radioactivity levels in the investigated samples are generally increased from mineral waters through therapeutic to the spring waters. The results show that a correlation between total dissolved solids (TDS) values and the 226Ra concentrations was found to be high indicating that 266Ra has a high affinity towards the majority of mineral elements dissolved in these waters. High correlation coefficients were also observed between 226Ra content and chloride ions for Cl−–Na+ water types. This can be explained by the fact that radium forms a complex with chloride and in this form is more soluble. The isotopic ratio of 234U/238U and 226Ra/234U varies in the range from 0.8 to 2.6 and 0.6 to 360.8, respectively, in all investigated waters, which means that there is no radioactive equilibrium between the two members of the 238U series. The fractionation of isotopes of a given element may occur because of preferential leaching of one, or by the direct action of recoil during radioactive decay. The annual effective doses due to ingestion of the mineral waters have been estimated to be well below the 0.1mSv/y reference dose level. [ABSTRACT FROM AUTHOR]