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).     

Natural radioactivity measurements in rock samples of Cuihua Mountain National Geological Park, China

The concentrations of the natural radionuclides namely 40K, 232Th and 226Ra in rock samples collected from Cuihua Mountain National Geological Park of China have been determined using a NaI(Tl) detector. The concentrations of 226Ra, 232Th and 40K in the studied rock samples range from 10.7 to 34.8, 19.9 to 53.6 and 642.7 to 1609.9 Bq kg(-1) with an average of 20.4, 30.1 and 1009.5 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). The values of H ex and H in are less than unity. The mean outdoor air absorbed dose rate is 69.7 nGy h(-1), and the corresponding outdoor effective dose rate is 0.086 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.     

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.     

²²⁶Ra, ²³²Th and ⁴⁰K radionuclides enhancement rate and dose assessment for residues of lignite-fired thermal power plants in Turkey

A total of 77 coal, slag and fly ash samples collected from six thermal power plants were measured by gamma-ray spectrometry. The average (226)Ra activity concentrations in coal, slag and fly ash were measured as 199.8±16.7, 380.3±21.8 and 431.5±29.0 Bq kg(-1), respectively. The average (232)Th activity concentrations in coal, slag and fly ash were measured as 32.0±2.4, 74.0±9.0 and 87.3±9.8 Bq kg(-1), respectively. The average (40)K activity concentrations in coal, slag and fly ash were found to be 152.8±12.1, 401.3±25.0 and 439.0±30.2 Bq kg(-1), respectively. The radium equivalent activities of samples varied from 147.6±8.5 to 1077.4±53.3 Bq kg(-1). The gamma and alpha index of one thermal power plant's fly ash were calculated to be 3.5 and 5 times higher than that of the reference values. The gamma absorbed dose rates were found to be higher than that of the average Earth's crust. The annual effective dose of residues measured in four thermal power plants were calculated higher than that of the permitted dose rate for public, i.e. 1 mSv y(-1).     

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.     

Radioactivity concentration in soil samples in the southern part of the West Bank, Palestine

The activity concentrations of naturally occurring radioactive materials such as (238)U, (232)Th and (40)K were measured for 38 soil samples collected from diverse zones in the southern area of West Bank, Palestine using gamma-ray spectroscopy. The measured activities of (238)U, (232)Th and (40)K were found to range from 32.9 to 104.7, 14.5 to 76.6 and 297 to 962 Bq kg(-1) with averages value of 68.7, 48.0 and 630 Bq kg(-1), respectively. The obtained values of activity concentrations are higher than the world average of 35, 30 and 500 Bq kg(-1) for (238)U, (232)Th and (40)K, respectively. The measured (137)Cs activity concentration was found to range from 1.8 to 36.1 Bq kg(-1) with an average value of 8.5 Bq kg(-1). The detected activities were attributed to the fallout of (137)Cs, which is the only man-made radionuclide. The calculated average of the total gamma-radiation dose rate of natural radionuclides, (137)Cs and cosmic radiation is 121.4 nGy h(-1). The radium equivalent activity (R(aeq)), dose rate (D(r)), external hazard index (H(ex)) and radioactivity level index (I(gamma)) in all samples are presented. Some values were found to be in the range of worldwide values, whereas others were above the worldwide values.     

Radiological impacts of natural radioactivity from soil in Montenegro

Soil samples from Montenegro were analysed by the HPGe detector with 40 % of relative efficiency, for radioactivity due to (226)Ra, (232)Th and (40)K. The average activity concentrations have been found to be 39.9, 43.5 and 437.6 Bq kg(-1), respectively, i.e. in accordance with those in the other South European countries. In order to evaluate the health hazard, radium equivalent activity, absorbed dose rate, annual effective dose rate, external hazard index, annual gonadal dose equivalent and excess lifetime cancer risk (CR) have been calculated. The excess lifetime CR (× 10(-3)) had a range from 0.12 to 0.79, with an arithmetic mean of 0.27, which is in accordance with the global average. Mean gonadal dose equivalent was higher than the world average, and one location was found with the radium equivalent activity >370 Bq kg(-1), i.e. with the external hazard index higher than unity, which means the radiation hazard is not negligible.     

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.     

Natural radioactivity levels and radiation hazard indices in granite from Aswan to Wadi El-Allaqi southeastern desert, Egypt

Studies on radiation level and radionuclide distribution in granite from Aswan to Wadi El-Allaqi area that is located in southeastern desert of Egypt were undertaken. The samples collected from five locations: Gabal El Mesala, Umm Hibal, Abu Herigle, Abu Marw and Deneibit El Quleib. The purpose of this study is to provide a baseline map of radioactivity background levels in the investigated area environment, and this study will be used as reference information to assess any changes in the radioactive background level due to geological processes. The highest average values of 226Ra and 232Th concentrations (24.00 and 31.28 Bq kg(-1), respectively) were observed at Abu Herigle region, whereas the highest average value of 40K concentration, 589.95 Bq kg(-1), was detected in Umm Hibal. The absorbed dose rate in air was found to be in the range between 5.40 and 45.11 nGy h(-1), and radium equivalent activity concentration was found in the range between 29.57 and 71.85 Bq kg(-1). Also the representative external hazard index values for the corresponding samples were also estimated and given.     

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.     

Gamma-emitting radionuclides in the shallow marine sediments off the Sindh coast, Arabian Sea

Determination of gamma emitting radionuclides in shallow marine sediments off the Sindh coast has been carried out using a gamma spectrometry technique. The activity concentration measured in various sediment samples off the Sindh coast has been found to vary from 15.93 +/- 5.22 to 30.53 +/- 4.70 Bq kg(-1) for 226Ra, from 11.72 +/- 1.22 to 33.94 +/- 1.86 Bq kg(-1) for 228Ra and from 295.22 +/- 32.83 to 748.47 +/- 28.75 Bq kg(-1) for 40K. The calculated mean values of radium equivalent activity, absorbed dose rate and effective dose are 98 Bq kg(-1), 49 nGy h(-1) and 0.06 mSv y(-1), respectively. No artificial radionuclide was detected in the samples measured from the study area. As no data on radioactivity of the coastal environment of Pakistan are available, the data presented here will serve as baseline information on radionuclide concentration in shallow sea sediments off the Sindh coast. The data will also be useful for tracking pollution inventories from unusual radiological events (if any) in the territorial waters of the study area. Further, the information presented will contribute to modelling of a regional radioactivity database from the perspectives of the International Atomic Energy Agency's Asia-Pacific Marine Radioactivity Database and Global Marine Radioactivity Database.     

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.     

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).     

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.     

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.     

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).     

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.     

Lung cancer risks due to the radon in cigarette tobacco

Thirty-one tobacco samples were evaluated for the activity concentrations of radon and radium using solid-state nuclear track detectors (CR-39). The detectors were exposed for a period of 150 days to different types of cigarette tobacco. The highest values of 364 Bq m^–3 for radon and 31.4 Bq kg^–1 for radium were obtained for MIA2 sample, and the lowest values of 20.2 Bq m^–3 for radon and 1.74 Bq kg^–1 for radium, for SUM sample. According to the estimate, this range of radon levels corresponds to the lung cancer incidence in the range 22–396 cases per million smoker per year. The annual effective dose in general and for lungs in particular, the surface and mass exhalation rate, the equivalent equilibrium concentration of radon, and absorbed dose to tissues and lungs were calculated. The highest values were obtained for MIA2 sample, and the lowest values, for SUM sample.     

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.