Measurement of radiation levels in soil samples by γ-ray spectrometry

The natural terrestrial gamma radiation dose rate is an important contribution to the average dose rate received by the world's population. Estimation of the radiation dose distribution is important in assessing the health risk to a population and serve as the reference in documenting changes to environmental radioactivity in soil due to anthropogenic activities. Human beings are exposed outdoors to the natural terrestrial radiation that originates predominantly from the upper 30 cm of the soil. Only radionuclides with half-lives comparable with the age of the earth or their corresponding decay products existing in terrestrial material such as ²³⁸U, ²³²Th and ⁴⁰K are of great interest. Since these radionuclides are not uniformly distributed, the knowledge of their distribution in soil and rock play an important role in radiation protection and measurement. Gamma radiation from these represents the main external source of irradiation to the human body and the concentrations of these radionuclides in soil are determined by the radioactivity of the rock and also nature of the process of the formation of the soils. Therefore, radionuclides in soil generate a significant component of the background radiation exposure to the population