Analysis of ²²⁶ Ra, ²³²Th ⁴⁰К and ¹³⁷ Cs in samples of soil from some areas of Republic of Macedonia by using gamma spectrometry

摘要

Taking into consideration the importance of the distribution and transfer of radio nuclides in soil, an attempt was made in this work to determine the concentration of ²²⁶Ra, ²³²Th ⁴⁰К and ¹³⁷Cs in the same. The concentrations of activity in the gamma-absorbed dose rates of the terrestrial naturally occurring radio nuclides, as follows, ²²⁶Ra, ²³²Th and ⁴⁰K were determined in samples of soil collected from some parts of Republic of Macedonia, i.e. from three major cities in the Republic of Macedonia. The samples are taken by means of a special dosage dispenser which enables sampling of samples at a depth of 0-5 cm, 5-10cm and 10-15cm, thus disabling the sampling above these layers of soil. An identification of radio nuclides and assessment of their activity has been performed by applying gamma spectrometry. The time of counting for each sample was 65000 s. in order to obtain statistically small mistake. The spectrums were analyzed by a commercially available software GENIE-2000 received from Canberra, Austria. The activity of soil had wide range of values: 20.3 to 82.9 Bq kg^-1for ²²⁶Ra, 16.1 to 82.5 Bq kg^-1 for ²³²Th, 325 to 799.0 Bq kg^-1for ⁴⁰К and 9.1 to 24.3 Bq kg^-1for ¹³⁷Cs, respectively. The concentrations of these radio nuclides have been compared with the available data from the other countries. Natural environmental radioactivity and the associated external exposure due to gamma radiation depend primarily on the geological and geographical conditions. Namely, the specific levels of terrestrial environmental radiation are related to the type of rocks from which the soils originate. The obtained data indicate that the average value of activity of ²³²Th is about higher than the one of ²²⁶Ra The concentration of activity of ⁴⁰К in the soil has greater value than ³²Th and ²²⁶Ra in all soils. The causes for the existence of ¹³⁷ Cs in these soils are the nuclear explosions, waste radioactive materials and other incidents. It reaches the surface of the pedosphere by means of dry and wet flushing and depending on the physical and the chemical properties of the soil, as well as depending on the eventually applied agrotechnical and agrochemical measures, it connects, that is, it penetrates in the deeper soil layers.