Determination of specific activity of 226Ra, 232Th and 40K for assessment of environmental hazards

Studies have been carried out using gamma-spectrometric techniques to determine the natural radioactivity in some rocks that are used as building materials in Yemen. The concentrations of the natural radionuclides namely(226) Ra, (232)Th and (40)K in the rock samples collected from different rock markets in Yemen have been determined using an NaI(Tl) detector. The concentrations of (226)Ra, (232)Th and (40)K in the studied rock samples range from 22.2 to 88.8 Bq kg(-1), 8.12 to 113.68 Bq kg(-1) and 31.3 to 2222.3 Bq kg(-1), respectively. The concentrations of these radionuclides are compared with the typical world values. To evaluate the radiological hazard of the natural radioactivity, the radium equivalent activity, the air absorbed dose rate, the annual effective dose rate, the representative level index and the values of both external and internal hazard indices were evaluated and compared with the internationally approved values. The radium equivalent activity values of all rock samples are lower than the limit of 370 Bq kg(-1) except for one sample which is about 413.386. The values of external hazard index (H(ex)) and internal hazard index (H(in)), absorbed doses in indoor air and the corresponding effective dose equivalents in a typical dwelling are presented. The need for further studies is also discussed.     

Measurement of natural radioactivity and assessment of associated radiation hazards in soil around Baoji second coal-fired thermal power plant, China

Activity concentrations of natural radionuclides (226)Ra, (232)Th and (40)K in soil around Baoji Second coal-fired thermal power plant of China were determined using gamma ray spectrometry. The mean activity concentrations of (226)Ra, (232)Th and (40)K in soil were found to be 40.3 ± 3.5, 59.6 ± 3.1 and 751.2 ± 12.4 Bq kg(-1), respectively, which are all higher than the corresponding average values in Shaanxi, Chinese and world soil. The radium equivalent activity (Ra(eq)), the air absorbed dose rate (D), the annual effective dose (E), the external hazard index (H(ex)) and internal hazard index (H(in)) were evaluated and compared with the internationally reported or reference values. All the soil samples have Ra(eq) lower than the limit of 370 Bq kg(-1) and H(ex) and H(in) less than unity. The overall mean outdoor terrestrial gamma air absorbed dose rate is ～86.6 ± 3.4 nGy h(-1) and the corresponding outdoor annual effective dose is 0.106 ± 0.004 mSv, which is higher than the worldwide average (0.07 mSv y(-1)) for outdoor's annual effective dose.     

Measurement of natural radioactivity in beach sands from Rizhao bathing beach, China

The natural radioactivity of (226)Ra, (232)Th and (40)K was determined for beach sand samples collected from Rizhao bathing beach, China, using gamma ray spectrometry. The measured activity in beach sand ranges from 7.6 to 17.2, 7.8 to 25.1 and 883.4 to 1313.6 Bq kg(-1) for (226)Ra, (232)Th and (40)K with mean values of 12.0, 15.2 and 1079.2 Bq kg(-1), respectively. The activity concentrations of (226)Ra and (232)Th in beach sands are lower, while (40)K is higher than the world average. The radium equivalent activity in all beach sand samples is lower than the safe limit set in the OECD report (370 Bq kg(-1)). The values of the external hazard index are less than unity. The mean outdoor air absorbed dose rate is 59.8 nGy h(-1) and the corresponding outdoor effective dose rate is 0.073 mSv y(-1).     

Natural radioactivity levels of granites used in Turkey

Thirty granite samples commonly used in Turkey were surveyed for natural radioactivity. Concentrations of natural radionuclides in all samples were determined by gamma-ray spectroscopy with hyper-pure germanium detector. The activity concentrations measured for (226)Ra and (232)Th ranged from 0.7±0.1 to 186±1 Bq kg(-1), and from 0.5±0.1 to 249±2 Bq kg(-1), respectively. The activity concentrations obtained for (40)K varied from minimum detectable activity (0.4 Bq kg(-1)) to 1935±11 Bq kg(-1). The radium equivalent activity (Ra(eq)), the absorbed dose rate (D), the external hazard index (H(ex)) and the annual effective dose equivalent were also calculated and compared with the international recommended values. Granite samples were also analysed mineralogically. It was observed that the presence of large amount orthoclase and radiogenic accessory minerals are the sources of high activity concentration levels.     

Specific activity and hazards of Archeozoic-Cambrian rock samples collected from the Weibei area of Shaanxi, China

The present work deals with the radioactivity of the Archeozoic-Cambrian rocks of the Weibei area, Shaanxi, China. A total of 45 rock samples of Archeozoic-Cambrian strata were investigated. The radionuclides of the samples, in Bq kg(-1), have been measured using Na(I)Tl gamma-ray spectrometer. The concentration of 226Ra, 232Th and 40K in the Archeozoic-Cambrian rock samples range from 12.3 to 55.4, from 2.4 to 98.7 and from 58.6 to 1613.3 Bq kg(-1), respectively. The measured activity concentrations for these radionuclides were compared with the typical world average values. To assess the radiological hazard of the natural radioactivity in the samples, the radium equivalent activity, the external hazard index, internal hazard index and the annual gonadal dose equivalent associated with the radionuclides were calculated and compared with the international recommended values.     

Study on radionuclides in granite quarries of Bangalore rural district, Karnataka, India

Studies on natural radiation levels and radionuclides were carried out extensively in the environment of granite quarries of Kanakapura, Ramanagara Taluks and Bidadi Hobli in Bangalore rural District and Bangalore city. The indoor and outdoor gamma exposure rate in air was measured using an environmental dosemeter, and it is converted into absorbed dose using suitable conversion factor. The activity concentrations of natural radionuclides in rock samples and also in soil samples were measured using an HPGe gamma-ray spectrometer. The results reveal that the activity concentrations of (226)Ra, (232)Th and (40)K in rocks are found to be vary from 32.2 to 163.6, 128.3 to 548.6 and 757.4 to 1418.4 Bq kg(-1), respectively, with corresponding arithmetic mean values of 93.2, 306.2 and 1074.4 Bq kg(-1). Activity concentrations of (226)Ra, (232)Th and (40)K in soil samples were found to vary from 32.4 to 55.2, 39.9 to 214.3 and 485.4 to 1150.2 Bq kg(-1), respectively, with corresponding arithmetic mean values of 40.7, 93.1 and 750.4 Bq kg(-1). The average activity levels of all these radionuclides are above the global average. This is consistent with the geological and geo-chemical significance of the rocks of the area under investigation. The results of these systematic investigations are discussed in detail and compared with the literature values represented for other environments.     

Study on external exposure doses from terrestrial radioactivity in Southern Vietnam

This paper presents the radioactivity concentrations of 226Ra, 232Th and 40K for 106 samples of surface soil collected in Southern Vietnam. The mean values of mass activity of radionuclides 226Ra, 232Th and 40K for Southern Vietnam are 28.6, 50.7 and 292.6 Bq kg(-1), respectively, which lead to the population-weighted absorbed dose rate of 54.5 nGy h(-1). The average annual effective doses outdoors, indoors and in total of Southern Vietnam are estimated to be 0.067, 0.374 and 0.441 mSv, respectively. The radium equivalent activity and the external hazard index of soil in Southern Vietnam are in the range 23.2-254.1 Bq kg(-1) and 0.06-0.69, respectively.     

Measurement of radioactivity in the soil of Bahawalpur division, Pakistan

Bahawalpur is the largest division of the Punjab province in Pakistan. It is larger than many countries of the world. Gamma activity from the naturally occurring radionuclides namely 226Ra, 232Th, the primordial radionuclide 40K and the artificial radionuclide 137Cs was measured in the soil of the Bahawalpur division using gamma spectrometry technique. The mean activity of 226Ra, 232Th, 40K and 137Cs were found to be 32.9 +/- 0.9, 53.6 +/- 1.4, 647.4 +/- 14.1 and 1.5 +/- 0.2 Bq kg(-1), respectively. The mean radium equivalent activity Raeq, external hazard index, internal hazard index and terrestrial absorbed dose rate for the area under study are 158.5 +/- 4.1 Bq kg(-1), 0.4, 0.5 and 77.32 nGy h(-1), respectively. The annual effective dose equivalent to the public was found to be 0.5 mSv.     

Environmental gamma radiation measurement in district Swat, Pakistan

External exposure to environmental gamma ray sources is an important component of exposure to the public. A survey was carried out to determine activity concentration levels and associated doses from (226)Ra, (232)Th, (40)K and (137)Cs by means of high-resolution gamma ray spectrometry in the Swat district, famous for tourism. The mean concentrations for (226)Ra, (232)Th and (40)K were found to be 50.4 +/- 0.7, 34.8 +/- 0.7 and 434.5 +/- 7.4 Bq kg(-1), respectively, in soil samples, which are slightly more than the world average values. However, (137)Cs was only found in the soil sample of Barikot with an activity concentration of 34 +/- 1.2 Bq kg(-1). Only (40)K was determined in vegetation samples with an average activity of 172.2 +/- 1.7 Bq kg(-1), whereas in water samples, all radionuclides were found below lower limits of detection. The radium equivalent activity in all soil samples is lower than the limit set in the Organisation for Economic Cooperation and Development report (370 Bq kg(-1)). The value of the external exposure dose has been determined from the content of these radionuclides in soil. The average terrestrial gamma air absorbed dose rate was observed to be 62.4 nGy h(-1), which yields an annual effective dose of 0.08 mSv. The average value of the annual effective dose lies close to the global range of outdoor radiation exposure given in United Nations Scientific Committee on the Effects of Atomic Radiation. However, the main component of the radiation dose to the population residing in the study area arises from cosmic ray due to high altitude.     

Radioactivity level in Chinese building ceramic tile

The activity concentrations of (226)Ra, (232)Th and (40)K have been determined by gamma ray spectrometry. The concentrations of (226)Ra, (232)Th and (40)K range from 158.3 to 1087.6, 91.7 to 1218.4, and 473.8 to 1031.3 Bq kg(-1) for glaze, and from 63.5 to 131.4, 55.4 to 106.5, and 386.7 to 866.8 Bq kg(-1) for ceramic tile, respectively. The measured activity concentrations for these radionuclides were compared with the reported data of other countries and with the typical world values. The radium equivalent activities (Ra(eq)), external hazard index (H(ex)) and internal hazard index (H(in)) associated with the radionuclides were calculated. The Ra(eq) values of all ceramic tiles are lower than the limit of 370 Bq kg(-1). The values of H(ex) and H(in) calculated according to the Chinese criterion for ceramic tiles are less than unity. The Ra(eq) value for the glaze of glazed tile collected from some areas are >370 Bq kg(-1).     

Radiological significance of cement used in building construction in Turkey

The activity concentration of (226)Ra, (232)Th and (40)K in seven cement types from different factories and grinding plants were measured using a gamma ray spectrometry with HPGe detector. The average activity concentrations observed in the studied cement samples (all from 141 samples) were 40.0 +/- 27.1, 28.0 +/- 20.9 and 248.3 +/- 95.0 Bq kg(-1) for (226)Ra, (232)Th and (40)K, respectively. The radium equivalent activity (Ra(eq)), the representative level index, the indoor absorbed dose rate and the corresponding annual effective dose were estimated for the potential radiological hazard of the cement. The Ra(eq) values were compared with the corresponding values for cement of different countries. The mean indoor absorbed dose rate (87.4 +/- 48.5 nGy h(-1)) is slightly higher than the population-weighted average of 84 nGy h(-1), whereas the corresponding effective dose rate (0.4 +/- 0.2 mSv y(-1)) is lower than the dose criterion of 1 mSv y(-1). The obtained results indicate no significant radiological hazards arise from using Turkish cement in building construction.     

Natural and artificial radionuclide measurements and radioactivity assessment of soil samples in eastern Sichuan province (China)

The activity concentrations of natural and artificial radionuclides were measured in the eastern region of Sichuan province (China). One hundred and ninety-three soil samples from this region were collected and analysed by high-purity germanium gamma spectrometry. The measured results show that the average radioactivity concentrations of (226)Ra, (232)Th, (40)K and (137)Cs in the soil samples are 26, 49, 440 and 6 Bq kg(-1), respectively. The calculated average radium equivalent activity is 130 Bq kg(-1), which is less than the recommended limit of 370 Bq kg(-1). The absorbed dose rate and annual effective dose are 60 nGy h(-1) and 74 μSv, respectively. This is the first time the absorbed dose rate in the east region of Sichuan has been mapped. Overall, the environmental radiation background is greater in the southern part of the area studied than in the northern.     

Terrestrial gamma radioactivity levels and their corresponding extent exposure of environmental samples from Wadi El Assuity protective area, Assuit, Upper Egypt

Representative environmental samples (sandy soil, limestone, marble and gravels) collected from Wadi El Assuity, protective area, Assuit governorate in Upper Egypt have been investigated radiometrically using NaI (Tl) gamma-ray spectrometer. The specific activity of the radionuclides in Bq kg?1 for soil ranged between 10.5 and 18.7 for 22?Ra, 1.5 to 4.6 for 232Th and from 94 to 107 for ??K, for limestone ranged between 19 and 27.1 for 22?Ra, 32.9 to 50 for 232Th and from 49 to 7 3 for ??K, where, for marble ranged between 12.2 and 30.7 for 22?Ra, 32.6 to 59.5 for 232Th and 55 to 70 for ??K and for gravels ranged between 7.8 and 21.8 for 22?Ra, 19.8 to 30.0 for 232Th and from 151 to 260 for ??K. The mean activity concentrations of measured radionuclides were compared with other literature values. The absorbed dose rate, radium equivalent activity and external hazard index were calculated and compared with internationally recommended values. The gamma absorbed dose rates in the samples ranged between 8.44 and 50.89 nGy h?1. These dose rates are consistent with the accepted worldwide average 55 nGy h?1 for the public. All values obtained for radium equivalent activity are < 370 Bq kg?1, which are acceptable for safe use. The calculated values of external hazard index obtained varied from 0.12 to 0.24. Since these values are lower than unity, one can say that the radiation hazard is insignificant for the population living in the investigated area. This permits the use of these materials sediments as building materials in any probable development projects at this area.     

Measurement of natural radioactivity and dose rate assessment of terrestrial gamma radiation in the soil of southern Punjab, Pakistan

Activity concentrations of (226)Ra, (232)Th, (40)K and (137)Cs in soil samples collected from the most populous area of southern Punjab of Pakistan have been measured by gamma-ray spectrometry. The measured activity concentrations for these radionuclides are compared with the reported data from different other countries and it is found that measured activity concentrations are comparable with the worldwide measured average values reported by the UNSCEAR. Subsequently assessed radiological effects show that the mean radium equivalent activity (Ra(eq)) is 96.7 +/- 15.2 Bq kg(-1) and air absorbed dose rate (D) is 46.1 +/- 7.3 nGy h(-1). The values of internal and external radiation hazard indices are found to be less than unity. The annual effective radiation dose is calculated to be 0.28 +/- 0.05 mSv, which is well below the limit of 1.0 mSv y(-1) recommended by the International Commission on Radiological Protection, for the general public.     

Natural radioactivity and external dose assessment of surface soils in Vietnam

In this study, natural radioactivity in surface soils of Vietnam and external dose assessment to human population, deduced from activities of (226)Ra, (232)Th and (40)K nuclides, were determined. From 528 soil samples collected in 63 provinces of Vietnam, including five centrally governed cities, the average activities were obtained and equal to 42.77 ± 18.15 Bq kg(-1) for (226)Ra, 59.84 ± 19.81 Bq kg(-1) for (232)Th and 411.93 ± 230.69 Bq kg(-1) for (40)K. The outdoor absorbed dose rates (OADRs) in air at 1 m above the ground level for 63 provinces were calculated, and their average value was 71.72 ± 24.72 nGy h(-1), with a range from 17.45 to 149.40 nGy h(-1). The population-weighted OADR of Vietnam was 66.70 nGy h(-1), which lies in the range of 18-93 nGy h(-1) found in the World. From the OADRs obtained, it was estimated that the outdoor annual effective dose and indoor annual effective dose to the population were 0.082 and 0.458 mSv, which are higher than the corresponding values 0.07 and 0.41 mSv, respectively, of the World. The radium equivalent activity Ra(eq) and the external hazard index H(ex) of surface soils of Vietnam are lower than the corresponding permissible limits of 370 Bq kg(-1) and 1, respectively. Therefore, soil from Vietnam is safe for the human population when it is used as a building material.     

Assessment of radionuclide level in topsoil samples for partial areas of Tibet, China

By using high-purity germanium gamma spectroscopy, specific activities of naturally occurring and man-made radionuclides were determined in topsoil samples collected from Nyingch, Lhasa and Xigazê of Tibet Autonomous Region, China. The average activity concentrations of (226)Ra, (232)Th and (40)K were 25.1 ± 0.7, 67.1 ± 2.8 and 608.6 ± 12.9 Bq kg(-1), respectively. The activity concentration of (137)Cs was found to vary from <0.3 (minimum detection concentration) to 46.2 Bq kg(-1) with an average of 4.3 ± 0.5 Bq kg(-1). By using the results of (226)Ra, (232)Th and (40)K in the sampled soils, the average outdoor gamma dose rate in air was calculated as 77.5 ± 23.2 nGy h(-1). Furthermore, the average outdoor annual effective dose from terrestrial radiation was 0.10 mSv. The external hazard index in this work varied from 0.20 to 0.70 with an average of 0.40 ± 0.14. The external exposure from terrestrial radiation will not pose any significant radiological threat to the population resident in the studied areas.     

Measurements of activity concentrations of naturally occurring radionuclides in soil samples from Punjab province of Pakistan and assessment of radiological hazards

The natural level of radioactivity in soil is one of the major causes of external gamma rays exposure. It was considered imperative to measure gamma-ray activity concentrations due to naturally occurring, potentially hazardous radionuclides from 232Th, 226Ra and 40K in soil samples from Punjab, the most populated province of Pakistan. The activity concentrations were measured in soil samples collected from all 34 district headquarters of Punjab province using a P-type coaxial high purity germanium (HPGe)-based gamma-ray spectrometer having a relative efficiency of 60%. The mean activity concentrations for 232Th, 226Ra and 40K were found to be 41 +/- 8, 35 +/- 7 and 615 +/- 143 Bq kg(-1), respectively in soil samples from all 34 district headquarters of Punjab. The mean values of radium equivalent index (Ra(eq)) and total annual external gamma radiation dose were found to be 141 +/- 27 Bq kg(-1)and 0.38 mSv, respectively. Since these estimated radiological impact assessment factors are lower than the recommended values there seems to be no potential radiological health hazard associated with the soils from the district headquarters in the Punjab province of Pakistan. Geological studies show that most of the soils in Punjab have developed on the extensive fluviatile deposits of five rivers and a stable ratio of natural activity concentrations is observed in soil samples of the areas under study.     

Assessment of radiological hazards of naturally occurring radioactive materials in cement industry

A study on the radiological hazard in Portland cement due to the presence of naturally occurring radioactive materials is being carried out. The Portland cement manufactured in the Islamabad/Rawalpindi region of Pakistan, intermediate products (clinker) and the various raw materials which compose the product have been analysed for (226)Ra, (232)Th and (40)K using a gamma spectrometry system with a N-type high-purity germanium detector of 80 % relative efficiency. From the measured gamma ray spectra, specific activities were determined. The mean values of the total specific activity of (226)Ra, (232)Th and (40)K are 34.2±11.9, 29.1±3.6 and 295.1±66.9 Bq kg(-1), respectively in Portland cement, 28.4±8.7, 11.3±1.7 and 63.1±17.3 Bq kg(-1), respectively in lime stone, 8.2±1.9, 16.2±3.9 and 187.7±53.2 Bq kg(-1), respectively in gypsum, 34.7±13.1, 41.2±6.7 and 187.6±17.2 Bq kg(-1), respectively in clay, 41.1±11.8, 39.3±6.9 and 195.1±29.2 Bq kg(-1), respectively in latrite and 51.1±18.2, 23.2±1.2 and 258.4±15.3 Bq kg(-1), respectively in clinker. The radium equivalent activities (Ra(eq)), external hazard index (H(ex)), internal hazard index (H(in)), absorbed dose rate in air (D) and annual effective dose rate (E(eff)) were also determined. The measured activity concentrations for these radio nuclides and radiological indices were compared with the reported national and international data. All these measured values are comparable with the worldwide data reported in UNSCEAR publications.     

Natural background dose and radium equivalent measurements at Ikogosi warm spring, Nigeria

The natural background dose and the radium equivalent due to the natural radioactivity levels in rocks and sediments collected around Ikogosi warm spring, Nigeria, has been determined in this study using a highly sensitive HpGe detector. The mean activity concentration of (40)K, (226)Ra and (228)Ac were measured to be 585.50 +/- 17.40 Bq kg(-1), 66.91 +/- 5.23 Bq kg(-1) and 48.91 +/- 2.10 Bq kg(-1), respectively, in rock samples while in sediment samples the activity concentrations were found to be 113.89 +/- 5.64 Bq kg(-1) for (40)K, 21.47 +/- 5.14 Bq kg(-1) for (226)Ra and 14.20 +/- 1.07 Bq kg(-1) for (228)Ac. This mean values give rise to average absorbed dose rate of 85.87 nGy h(-1) at a distance of 1.0 m above the ground level and a mean human effective dose equivalent of 0.53 man Sv y(-1) for rock samples. A radium equivalent of 50.55 Bq kg(-1) was measured for the sediment samples. The radium equivalent value is far less than the 370 Bq kg(-1) limit for materials that can be used as building materials while the human effective dose equivalent falls below the world average background dose of 2.4 man Sv y(-1).     

Radionuclide content and associated radiation hazards of building materials and by-products in Baoji, West China

Seven types of common building materials and by-products of coal-fired power plants collected from Baoji, West China, were analysed for the natural radioactivity of 226Ra, 232Th and 40K using gamma ray spectrometry with an NaI(Tl) detector. The average activity concentrations vary from 23.0 to 112.2, 20.2 to 147.5 and 113.2 to 890.8 Bq kg(-1) for 226Ra, 232Th and 40K, respectively. The measured activity concentrations for these radionuclides were compared with the data reported from other countries and with the worldwide average activity of soil. As a measure of radiation hazard to the people, the radium equivalent activities, total annual effective dose and activity concentration index were estimated. The radium equivalent activities of the studied samples are below the internationally accepted values. The calculated total annual effective dose and the activity concentration index of seven types of common building materials are <1 mSv y(-1) and 1, respectively. But fly ash and bottom ash exhibit the higher values that exceed and be close to the acceptable values, respectively. This study shows that the measured building materials do not pose any significant source of radiation hazard and are safe for use in the construction of dwellings. Nevertheless, when fly ash and bottom ash are used in dwelling construction, it is important to assess their radiation potential.