Abstract
A first comprehensive study is presented on natural radionuclide activity concentrations in surface soils in different divisions of Tafila city. The natural radioactivity of 238 U, 232 Th and 40 K is determined using gamma spectroscopy. The soil activity concentrations ranged from 1.8 to 76.4 Bq kg −1 for 238 U, 6.3 to 85.5 Bq kg −1 for 232 Th, and 84 to 516.7 Bq kg −1 for 40 K. The activity concentrations of the radionuclide in soils are directly relevant to outdoor exposure. Absorbed dose rates in air outdoors were calculated to be in the range of 22.28 – 62.71 nGy h −1 with an overall average value of 40.12 nGy h −1 . The study showed an annual effective dose equivalent in the range of 27.34 – 76.96 µSv y −1 . A comparison of the measured values with the corresponding worldwide average values shows that the activities of natural radionuclides in the studied samples are below the world average activity values.
Highlights
Radionuclides have been present always in every environment of the earth’s surface
An attempt has been made to determine the concentration of 40K, 232Th and 238U in soil samples collected from ten different divisions of Tafila city using high purity germanium (HPGe) gamma ray spectrometer and to compute the total absorbed gamma dose rate in air due to the presence of 40K, 232Th and 238U in the samples
It can be seen in this table that the mean activity concentrations of 232Th and 40K were 27.91 Bq kg−1 and 285.02 Bq kg−1, respectively
Summary
Radionuclides have been present always in every environment of the earth’s surface. Only nuclides with half-lives comparable to the age of the earth or their corresponding decay products, existing in terrestrial materials, can still be found today on earth, e.g. 40K, and the radionuclides from the 238U and 232Th series (UNSCEAR, 2000). It is interesting to mention that only few previous studies were conducted to determine the radioactivity levels and associated dose rates from surface soils in Jordan. Al-Hamarneh et al (2003) have made a study on surface and core soil samples collected from different regions of Jordan. In their work, they focused on measuring the concentrations of artificial radionuclides. Similar study has been made by AL-Jundi et al (2003) on a measurement of the specific activity and the gamma-ray absorbed doses of the naturally occurring radionuclides in soil cores obtained from eight sites along Amman Aqaba National Highway. An attempt has been made to determine the concentration of 40K, 232Th and 238U in soil samples collected from ten different divisions of Tafila city using HPGe gamma ray spectrometer and to compute the total absorbed gamma dose rate in air due to the presence of 40K, 232Th and 238U in the samples
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