Terrestrial radiation exposure emitted from naturally occurring radionuclides, such as 40K and radionuclides from the 238U and 232Th series and their decay products represent the main external source of irradation to human body. The purpose of this study was to provide the assessment of the doses from terrestrial exposure of population in Belgrade. The gamma dose rate, annual effective doses and external hazard indexes due to terrestrial natural occurring radionuclides (226Ra, 232Th, 40K) were calculated based on their activities in soil samples in Belgrade determined by gamma-ray spectrometry. The mean value of the total absorbed gamma dose rate outdoors due to terrestrial radionuclides for Belgrade was 59 nGy/h which is close to the worldwide average value (58 nGy/h). The values of the gamma dose rate varied among sampling locations as a consequence of different geological formations in the investigated area. The mean value of annual effective dose of 73 Sv was significantly lower than the maximum allowed dose of 1 mSv for the population and was consistent with the worldwide average value. The mean value of external hazard index was found to be 0.28. The results of this assessment study pointed out that there is no significant radiation risk to the population of Belgrade due to terrestrial exposure to radiation from natural sources outdoors.I International Conference on Radiation in Various Fields of Research : RAD 2017 : book of abstracts; April 25-27, 2012; Niš, Serbi

Dragović, Ranko M.

Dragović, Snežana D.

Janković Mandić, Ljiljana

Onjia, Antonije

Đolić, Maja

Terrestrial radiation exposure emitted from naturally occurring radionuclides, such as 40K and radionuclides from the 238U and 232Th series and their decay products represent the main external source of irradation to human body. The purpose of this study was to provide the assessment of the doses from terrestrial exposure of population in Belgrade. The gamma dose rate, annual effective doses and external hazard indexes due to terrestrial natural occurring radionuclides (226Ra, 232Th, 40K) were calculated based on their activities in soil samples in Belgrade determined by gamma-ray spectrometry. The mean value of the total absorbed gamma dose rate outdoors due to terrestrial radionuclides for Belgrade was 59 nGy/h which is close to the worldwide average value (58 nGy/h). The values of the gamma dose rate varied among sampling locations as a consequence of different geological formations in the investigated area. The mean value of annual effective dose of 73 Sv was significantly lower than the maximum allowed dose of 1 mSv for the population and was consistent with the worldwide average value. The mean value of external hazard index was found to be 0.28. The results of this assessment study pointed out that there is no significant radiation risk to the population of Belgrade due to terrestrial exposure to radiation from natural sources outdoors.I International Conference on Radiation in Various Fields of Research : RAD 2012 : April 25-27, 2012; Niš, Serbi

Repository of the Vinča Nuclear Institute (VinaR)

The First International Conference on Radiation and Dosimetry in Various Fields of ResearchApril 2012Faculty of Electronic Engineering  |  NiŠ    Serbia 25 – 27,  |M M X I IPROCEEDINGS  Publisher:  University of Niš, Faculty of Electronic Engineering P.O.Box 73, 18000 Niš, Serbia www.elfak.ni.ac.rs  For the publisher: Prof. Dr. Zoran Perić  Editor: Prof. Dr. Goran Ristić  Cover design: Vladan Nikolić, arch.   Technical editing: Vladan Nikolić, arch.  Proof-reading: Saša Trenčić, BA  Printed by: Medivest, Niš    Print run: 200 copies  The First International Conference on Radiation and Dosimetry  is realized as a part of the FP7 project: Joint research on various types  of radiation dosimeters (RADDOS)   ISBN 978-86-6125-063-7        POPULATION DOSES FROM TERRESTRIAL GAMMA EXPOSURE IN BELGRADE (SERBIA)  AND THEIR RELATION TO GEOLOGICAL SETTING Lj. Janković-Mandić1, R. Dragović2, M. Djolić1, A. Onjia1, S. Dragović3   1University of Belgrade, Vinča Institute of Nuclear Sciences, P.O. Box 522, Belgrade 2University of Niš, Faculty of Science and Mathematics, Višegradska 33, Niš 3University of Belgrade, Institute for the Application of Nuclear Energy, Banatska 31b, Belgrade Abstract. Terrestrial radiation exposure emitted from naturally occurring radionuclides, such as 40K and radionuclides from the 238U and 232Th series and their decay products represent the main external source of irradation to human body. The purpose of this study was to provide the assessment of the doses from terrestrial exposure of population in Belgrade. The gamma dose rate, annual effective doses and external hazard indexes due to terrestrial natural occurring radionuclides (226Ra, 232Th, 40K) were calculated based on their activities in soil samples in Belgrade determined by gamma-ray spectrometry. The mean value of the total absorbed gamma dose rate outdoors due to terrestrial radionuclides for Belgrade was 59 nGy/h which is close to the worldwide average value (58 nGy/h). The values of the gamma dose rate varied among sampling locations as a consequence of different geological formations in the investigated area. The mean value of annual effective dose of 73 Sv was significantly lower than the maximum allowed dose of 1 mSv for the population and was consistent with the worldwide average value. The mean value of external hazard index was found to be 0.28. The results of this assessment study pointed out that there is no significant radiation risk to the population of Belgrade due to terrestrial exposure to radiation from natural sources outdoors. Key words: radium, thorium, potassium, exposure, lithology.   1. INTRODUCTION  Assessment of the radiation doses in humans from natural sources is of special importance because natural radiation is the largest contributor to the collective dose received by the world population. The knowledge of the doses from natural background is necessary as a basis for comparison with man-made sources of exposure. Moreover, owing to the large variability of doses from natural sources of radiation, some individual doses may be high enough to obligate the introduction of remedial measures. Many radionuclides exist naturally at trace levels in various soil and rock formations. Particular interest is being focused on the external exposure due to gamma radiation emitted by naturally occurring radionuclides. The significant sources of this external exposure are the 238U decay chain, the 232Th decay chain and the 40K. This exposure depends primarily on the geological and geographical conditions and, a significant part, is delivered outdoors [1]. The aim of this work to determine the activity concentrations of 226Ra, 232Th and 40K in soil samples collected across the city of Belgrade, the capital of Serbia, using gamma ray spectrometry and use the results  to calculate absorbed gamma dose rate in air, annual effective dose equivalent and external hazard index Belgrade is expected to change from being a city to a conurbation in the near future and baseline data of this type will be of importance in the assessments of population exposure. 2. MATERIALS AND METHODS The city of Belgrade is located in the northern part of Serbia. It spreads over area of about 1000 km2 and has a population of approximately 1.8 million, i.e. about 20% of total population of Serbia.   The samples of undisturbed soils were collected from 70 locations of Belgrade during 2006-2010. A total of 230 samples were collected. From each location, 3-4 subsamples were collected by  template method [2], up to depth of 10 cm. Samples were dried at 105 °C to a constant weight and then homogenized. The homogenized samples were placed in 1L Marinelli beakers. The beakers were sealed hermetically and kept aside for about a month to ensure equilibrium between 226Ra and its daughters before being taken for gamma spectrometric analysis.  The measurements were performed using HPGe gamma-ray spectrometer ORTEC-AMETEK (34%  296 relative efficiency and 1.85 keV FWHM for 60Co at 1.33 MeV, 8192 channels) shielded with 10 cm lead internally lined with 2 mm copper foil. The weight of each sample was approximately 1 kg. The activity of each sample was measured for 60 ks. A mixed calibration source MBSS 2 from Czech Metrological Institute, was used for efficiency calibration in the same geometry as the measured samples. For the purpose of quality assurance, independent checks on calibration were performed using two standard reference materials from International Atomic Energy Agency (IAEA-385) and Environmental Measurement Laboratory United States Department of Energy (QAP-9803). The activity of 226Ra was evaluated from the gamma ray of 609.3 keV of 214Bi peak and 351.9 keV of 214Pb, while 911.2 and 969.1 keV gamma-ray lines emitted by 228Ac and 238.6 keV emitted by 212Pb was used to determine 232Th. The activity of 40K was determined using its 1460.8 keV gamma-ray line.  Gamma Vision 32 was used to process the spectra obtained [3]. Statistical evaluation of obtained results was performed using statistical package SPSS 10.0 for Windows [4].  2.1. Absorbed gamma dose rate  The external gamma dose rate in the air at 1 m above ground level was calculated from the measured activity concentrations of 226Ra, 232Th and 40K in soil assuming that other radionuclides, such as 137Cs, 90Sr and the 235U series can be neglected as they contribute very little to the total dose from environmental background [5,6,7]. The calculation were performed according to the following equation [1]: D = 0.462ARa+ 0.604ATh+0.042AK (1) where ARa, ATh, and AK are activity concentrations (Bq kg-1) of 226Ra, 232Th and 40K, respectively. 2.2. Annual effective dose equivalent  In order to estimate the annual effective doses, one must take into account the conversion coefficient from absorbed dose in air to effective dose and the indoor occupancy factor. Using the dose conversion factor of 0.7 Sv Gy-1 and occupancy factor of 0.2 adopted by UNSCEAR (2000) the annual effective dose equivalent (AEDE) was calculated as follows [1]: AEDE  = D  8760  0.7  0.2 (2) 2.3. External hazard index  The external hazard index Hex provides a useful guideline for regulating the safety standards on radiation protection for the general public. It was calculated by using the equation [8]:  Hex = ARa/370 + ATh/259 + AK /4810  (3)  where ARa,ATh,,AK are activity concentrations (Bq kg-1) of 226Ra, 232Th and 40K respectively, in soil samples. The value of this index must be less than unity to keep the radiation hazard insignificant, i.e. to keep the radium equivalent activity and annual dose under the permissible limits of 370 Bq kg-1 and 1 mSv, respectively [9]. 3. RESULTS AND DISCUSSION Descriptive statistics for activity concentrations of primordial radionuclides in soil samples collected in Belgrade area is presented in Table 1.  Table 1 Descriptive statistics of activity concentrations of 226Ra, 232Th and 40K for all analyzed soil samples  It can be seen that activity concentrations of 226Ra, 232Th and 40K, ranged from 12 to 55 Bq kg-1, from 11 to 64 Bq kg-1 and from 280 to 800 Bq kg-1, respectively. The mean activity concentration for 226Ra of 33 Bq kg-1 was close to the world average value of 32 Bq kg-1, that of 232Th  38 Bq kg-1 was about 18% lower than the world average value, while mean activity concentration of 40K 504  Bq kg-1 was 18%  higher than world average value. The analyzed radionuclides showed a range of concentrations, as a consequence of the variety of lithological components in the investigated area. The most of sampling locations are situated on terrains of the southern rim of  Panonian area and the northern parts of Sumadian mesozoic joist. There are two structural floors in tectonics of Belgrade area. The first one is composed of jurassic and cretaceous sediments and magmatic products. The parts of mesozoic joist on west are composed of flysh sediments of upper cretaceous series, which are covered by neogen sediments with horizontal stratification important for the development of pedological cover. The second structural floor is composed of neogen sediments. More than 70% of the territory of Belgrade is covered by quaternary deposits of alluvial lake, alluvial marsh, alluvial, delluvial, delluvial, delluvial-prolluvial, prolluvial and eolic sediments. Near the Sava and Danube rivers, alluvial sediments are deposited, and in the area of Zemun and Bezanija, loess is predominant [10]. Such a geological composition, together with the expressed structural formations and different terrain elevation, causes differences in concentration of analyzed radionuclides in soils. Descriptive statistics for the total absorbed gamma dose rates (D), annual effective dose equivalent (AEDE) and external hazard index (Hex) are presented in Table 2.    Activity concentration (Bq kg-1) Parameter 226Ra 232Th 40K Range 43 53 520 Mean 33 38 500 Median 35 39 500 St. deviation 8 9 100 Minimum 12 11 280 Maximum 55 64 800  297 Table 2  Descriptive statistics of total gamma dose rate due to 226Ra, 232Th and 40K, annual effective dose equivalent  and external hazard index   The values of total gamma dose rates varied between 25 and 90 nGy h-1 with the mean value of 59 nGy h-1. According to UNSCEAR (2000) [1], the dose rate in air outdoors from terrestrial gamma rays in normal circumstances is approximately 60 nGy h-1 and the national average ranges from 1 to 1100  nGy h-1. The mean value of D for soils analyzed in this study is close to the world average value.  The contribution to the total absorbed gamma dose rate by 226Ra, 232Th and 40K was 25%, 39% and 36%, respectively. The contribution of each radionuclide to the total dose depends primarily on soil type and geological background of each investigated location.  The values of  annual effective dose equivalent (AEDE) for different locations Belgrade ranged from 31 to 110 Sv y-1  with mean value of  73 Sv y-1, which is much below the maximum permissible dose of 1 mSv y-1 recommended by the ICRP for members of the public [9] and also less than the average external gamma dose of 0.48 mSv y-1 from natural radiation sources of terrestrial origin assessed by UNSCEAR (2000) [1]. The range and mean values of absorbed gamma dose rate due to 226Ra, 232Th and 40K obtained for Belgrade are compared with values reported for cities worldwide (Table 3). Table 3. Absorbed gamma dose rates in cities from different parts of the world compared with that obtained in present study It can be seen that the mean value of gamma dose rate observed in the present study (59 nGy h-1) lies within the reported values. It is comparable with those reported for the cities of Zacatecas, Mexico [19] (45 nGy h-1), Windhoek, Namibia [18] (56 nGy h-1) and Istanbul, Turkey [15] (49 nGy h-1). The value obtained in the present study is 2.6-fold lower than that assessed by Hosseini (2007) for Zahedan, Iran [20] (158 nGy h-1).   However, it is about 2.5-fold higher than gamma dose rates reported for Tripoli, Libya [17] (23 nGy h-1) and Alkharje, Saudi Arabia [11] (24 nGy h-1). These differences in terrestrial radioactivity, and the associated external exposure due to gamma radiation, are caused by geological and geographical specifities of investigated areas. The high gamma dose rates reported for Teheran could be explained by its geological composition which includes metaluminous to weakly peraluminous rocks, corresponding to  magnetite- and ilmenite-bearing granitoids, ranging from diorites to granites [21]. The mean value of external hazard index was found to be 0.28. The results of this assessment study pointed out that there is no significant radiation risk to the population of Belgrade due to terrestrial exposure to radiation from natural sources outdoors The results of this study are useful as a data baseline for preparing a radiological map of the studied area as well as for enrichment of the worlds data bank. Before more definite conclusions of hazards of population exposure to natural radionuclides and drawn, an extended and more systematic survey of the area in needed. Acknowledgement: This work was supported by the Ministry of Education and Science of the Republic of Serbia (Project No. III 43009).  REFERENCES   1. United Nations Scientific Committee on the Effect of Atomic Radiation (UNSCEAR), Exposure from Natural Radiation Sources, New York: United Nations, 2000. 2. International Atomic Energy Agency, Soil sampling for environmental contaminants,  IAEA-TECDOC-1415, 2004. 3. ORTEC, Gamma Vision 32, Gamma-Ray Spectrum Analysis and MCA Emulation, Version 5.3. Oak Ridge, USA, 2001. 4. SPSS Inc. Statistical Package for the Social Sciences (SPSS) v. 10.0, Chicago, Illinois, http://www.spss.com. 1999. 5. D.C. Kocher, A.L. Sjoreen, Dose-rate conversion factors for external exposure to photon emmiters in soil. Health Phys, vol. 48, 1985, pp. 193-205. 6. P. Jacob, H.G. Paretzke, H. Rosenbaum, and M. Zankl, Effective dose equivalents for photon exposure from plane sources on the ground, Radiat. Prot. Dosim. vol.14, 1986, pp 299-300. 7. K.C. Leung, S.Y. Lau, and C.B. Poon, Gamma radiation dose from radionuclides in Hong Kong soil, J. Environ. Radioact. vol. 11, 1990, pp. 279-290.  8. J. Beretka, and P.J. Mathew, Natural radioactivity of Australian building materials, industrial wastes and byproducts, Health Phys. vol 48, 1995, pp. 87-95. 9. International Commission on Radiological Protection. 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Population doses from terrestrial gamma exposure in Belgrade (Serbia) and their relation to geological setting

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Population doses from terrestrial gamma exposure in Belgrade (Serbia) and their relation to geological setting

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