A comprehensive study of natural gamma radioactivity levels and associated dose rates from surface soils in cyprus

A survey was carried out to determine activity concentration levels and associated dose rates from the naturally occurring radionuclides 232Th, 238U and 40K, in the various geological formations of Cyprus, by means of high-resolution gamma ray spectrometry. A total of 115 representative soil samples were collected from all over the bedrock surface of the island, based on the different lithological units of the study area, sieved through a fine mesh, sealed in 1000 ml plastic Marinelli beakers and measured in the laboratory with respect to gamma radioactivity for a counting time of 18-h each. From the measured spectra, activity concentrations were determined for 232Th (range from 1.0 x 10(-2) to 39.8 Bq kg(-1)), 238U (from 1.0 x 10(-2) to 39.3 Bq kg(-1)) and (40)K (from 4.0 x 10(-2) to 565.8 Bq kg(-1)). Gamma absorbed dose rates in air outdoors were calculated to be in the range from 1.1 x 10(-2) to 51.3 nGy h(-1), depending on the geological features, with an overall mean value of 8.7 nGy h(-1) and a standard deviation of 8.4 nGy h(-1). This value is by a factor of about seven below the corresponding population-weighted world-averaged value of 60 nGy h(-1) and one of the lowest that has been reported from similar investigations worldwide. Assuming a 20% occupancy factor, the corresponding effective dose rates outdoors equivalent to the population were calculated to be between 1.3 x 10(-2) and 62.9 microSv y(-1), with an arithmetic mean value of 10.7 microSv y(-1) and a standard deviation of 10.3 microSv y(-1).     

A study of environmental radioactivity measurements for Cankiri, Turkey

This study is the first to assess the level of background radiation for the Cankiri province of Turkey. Indoor air radon concentrations were determined using Columbia Resin-39 nuclear track detectors and the average (222)Rn activity was found to be 44 Bq m(-3) (equivalent to an annual effective dose of 1.1 mSv). Measurements of gamma doses in outdoor air were performed using a portable plastic scintillation detector and the average gamma absorbed dose rate was found to be 8 μR h(-1) (corresponding to an annual effective dose of 87.7 μSv). Radionuclide activity concentrations in soil samples were measured through gamma-ray spectrometry and the average activities were determined as 17.7, 22.3, 357 and 4.1 Bq kg(-1) for the radionuclides (238)U, (232)Th, (40)K and (137)Cs, respectively. The average annual effective dose from the natural radioactivity sources ((238)U series, (232)Th series and (40)K) was calculated to be 44.4 μSv. Radioactivity levels of drinking water samples were carried out using a low-background proportional counter and the average gross alpha and beta activities were obtained as 0.25 and 0.26 Bq l(-1), respectively (equivalent to an annual effective dose of 184 μSv). The average radon concentrations in indoor air and the average radionuclide activities in soil were found to be lower than most Turkish cities while higher levels of outdoor gamma dose rate and water radioactivity were observed. The results of this study showed that the region's background radioactivity level differs considerably from the reported data for Turkish cities.     

Radiation dose in the high background radiation area in Kerala, India

A systematic radiological survey has been carried out in the region of high-background radiation area in Kollam district of Kerala to define the natural gamma-radiation levels. One hundred and forty seven soil samples from high-background radiation areas and five samples from normal background region were collected as per standard sampling procedures and were analysed for (238)U, (232)Th and (40)K by gamma-ray spectroscopy. External gamma dose rates at all sampling locations were also measured using a survey meter. The activities of (238)U, (232)Th and (40)K was found to vary from 17 to 3081 Bq kg(-1), 54 to 11976 Bq kg(-1) and BDL (67.4 Bq kg(-1)) to 216 Bq kg(-1), respectively, in the study area. Such heterogeneous distribution of radionuclides in the region may be attributed to the deposition phenomenon of beach sand soil in the region. Radium equivalent activities were found high in several locations. External gamma dose rates estimated from the levels of radionuclides in soil had a range from 49 to 9244 nGy h(-1). The result of gamma dose rate measured at the sampling sites using survey meter showed an excellent correlation with dose rates computed from the natural radionuclides estimated from the soil samples.     

Radionuclide concentrations in soils of Northern Namibia, Southern Africa

Activity concentrations of the naturally occurring radionuclides like (238)U, (232)Th and (40)K in 400 soil samples collected from four major towns across the northern region of Namibia have been determined using gamma-ray spectrometry with the objective of providing baseline data on the radiation level in the region. The average concentrations of radionuclides in the towns vary from 7.5 +/- 2.3 to 14.2 +/- 3.3 Bq kg(-1) for (238)U, 5.8 +/- 2.6 to 24.9 +/- 6.1 Bq kg(-1) for (232)Th and 52.1 +/- 28.7 to 380.1 +/- 112.9 Bq kg(-1) for (40)K. These concentrations were used to calculate the mean absorbed dose rate and the mean annual effective dose in the region. The low value of 21 +/- 16 microSv obtained for the mean annual effective dose indicates that the region has normal background radiation.     

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.     

Radiological significance of beach sand used for climatotherapy from Safaga, Egypt

As a part of national survey to evaluate natural radioactivity in the environment, concentration levels of radioactivity were analysed for sand samples from Safaga, Egypt, which is an ideal area for climatotherapy of psoriasis. Gamma dose rates of three beaches in Safaga were measured. The values ranged from 195.1 to 210.7 nGy h(-1). The activity concentrations (Bq kg(-1)) of radionuclides 238U series, 232Th series and 40K in three different sand profiles (0-5, 5-10, 10-15, 15-25 and 25 - 40 cm) were measured using gamma-ray spectrometry. The annual effective doses were 259 microSv y(-1) for Minveila, 255 microSv y(-1) for Ganet Safaga and 239 microSv y(-1) for Masab El-Ghazel beaches. The dose rates, radium equivalent activities and external hazard indices were evaluated and compared with the international data. These results may contribute to the determination of absorbed dose rate reference levels in Red Sea Coast at Safaga city.     

Measurements of environmental terrestrial gamma radiation average dose rate in three mountainous locations in the western region of Saudi Arabia

This paper describes measurements of external gamma radiation average dose rate from terrestrial gamma rays 1 m above the ground in three different mountainous locations in the western region of the Kingdom of Saudi Arabia. These locations are, At-Taif city, Al-Hada village and Ash-Shafa village. CaSO(4):Dy (TLD-900) thermoluminescence dosemeters were used for the detection of terrestrial gamma radiation at 40 different places in the three locations. The values of terrestrial gamma radiation average dose rate measured ranged between 14 and 279 nG h(-1) for the time interval from June 2001 to June 2002. The measured average dose rate varied with the season of the year. The gamma radiation average dose rates were 468, 541 and 781 microGy y(-1) for At-Taif city, Al-Hada village and Ash-Shafa village, respectively. The corresponding average effective dose rates for the three locations were 94, 108 and 156 microSv y(-1), respectively.     

Gamma activity of stream sediment feldspars as ceramic raw materials and their environmental impact

In situ gamma spectrometric measurements have been performed to characterise the natural radiation that emitted from the stream sediment feldspars in Wadi El Missikat and Wadi Homret El Gergab, Eastern Desert, Egypt. The measurements of potassium (K, %), equivalent uranium (eU, ppm) and equivalent thorium (eTh, ppm) were converted into specific activities and equivalent dose rate. The average specific activities were 1402 Bq kg(-1) for K, 113 Bq kg(-1) for eU and 108 Bq kg(-1) for eTh in Wadi El Missikat, while they were 1240, 104 and 185 Bq kg(-1) in Wadi Homret El Gergab. The calculated outdoor average effective dose rates was 1.1 mSv y(-1) in wadi El Missikat and 1.3 mSv y(-1) in Wadi Homret El Gergab. The terrestrial-specific activities and effective dose rate levels of the natural radioactivity in the two areas lie within the international recommended limits for occupational feldspar quarry workers. On the other hand, these results indicated that irradiation is higher than the allowable level for members of the public. Therefore, quarrying the feldspar sediments from these locations as ceramic raw materials may yield an undesired impact on the environment, especially through the indoor applications.     

Environmental radioactivity studies in the proposed Lambapur and Peddagattu uranium mining areas of Andhra Pradesh, India

The present work was aimed at the establishment of baseline radioactive data in the proposed Lambapur and Peddagattu uranium mining areas in the Andhra Pradesh state, India. The background concentrations of naturally occurring radioactivity in the near-surface soils of the study areas were estimated and the results were analysed. The (238)U concentration in the near-surface soil of the study area was found to vary from 100 to 176 Bq kg(-1), with a mean of 138±24 Bq kg(-1). (232)Th in the study area soils was found to vary between 64 and 116 Bq kg(-1), with a mean of 83±15 Bq kg(-1). The (40)K concentration was found to vary between 309 and 373 Bq kg(-1), with a mean of 343±20 Bq kg(-1). The mean natural background radiation levels were also measured with thermoluminescence (TL) dosimetry technique and with a μR-survey meter, in the villages of the study area. Dose rates measured by TL are found to vary from 1287 to 3363 μGy y(-1), with a mean of 2509 ± 424 μGy y(-1). The dose rates measured in the same villages with a μR-survey meter were found to be in the range of 1211-3255 μGy y(-1), with a mean of 2524 ± 395 μGy y(-1). The mean radiation levels in the study area are found to be relatively high when compared with (Indian) national and international averages. Correlations among radon, thoron and gamma dose rates were found to be poor. The pre-operational data produced in this work will be useful for comparison with future radiation levels during the proposed uranium mining operations.     

Natural and anthropogenic radionuclides in the granitic region of Kapidag peninsula, Western Anatolia, Turkey

Naturally occurring radionuclides of terrestrial origin (also called primordial radionuclides) are present in various degrees in all media in the environment. This study represents the reports on the natural and anthropogenic radionuclides in the Kapidag granitic region. For this purpose, activities of radionuclides in soil, beach sands and rocks of the region have been investigated to assess the radiological hazard of the natural radioactivity. The radium equivalent activities, the absorbed dose rates and the external hazard indexes have been calculated, and also in situ gamma dose rates have been measured in the region. The mean activities of (238)U, (232)Th and (40)K with the ranges were determined as 31.1±15.7 (12.1-71.9), 42.5±15.9 (19.7-94.9), 590.3±192.2 (184.7-892.5), in the soil, as 16.5±9.5 (4.9-40.8), 67.1±106.9 (18.5-433.0), 569.2±212.6 (162.0-821.1) in the sand and as 25.4±12.8 (4.8-50.7), 37.8±21.5 (4.5-96.7), and 592.4±285.5 (62.4-1121.6) Bq kg(-1) in the rocks, respectively. It was also observed that the average activities of (137)Cs were ranged 0-27.8 Bq kg(-1) in the soil and 0.6-3.8 Bq kg(-1) in the beach sands. The mean Ra(eq) activities of the rocks, sands and soil were found to be 125.1±59.5, 156.3±157.2 and 137.3±48.8 Bq kg(-1), respectively, lower than the recommended maximum value of 370 Bq kg(-1) with some exceptions. The maximum contributors to the total absorbed gamma dose rates in air were determined as (238)U (45%) for the beach sands, (238)U (40%) for the soil and (40)K (41%) for rocks. The average outdoor gamma dose rates for the soil due to terrestrial and cosmic radiations were found to be 64.6±22.7 and 47.1±9.6 nGy h(-1), respectively, with the total of 111.7±29.5 nGy h(-1) outdoor gamma exposure rate and the annual average effective outdoor gamma dose was calculated as 137±36.2 μSv for the region. The results of the study were discussed with similar studies in close regions and the worldwide averages.     

Annual effective dose due to natural radionuclides in building blocks in eight cities of Southwestern Nigeria

The specific absorbed dose rates due to (226)Ra, (232)Th and (40)K in building blocks have been determined for a model dwelling dimension of 3.6 x 3.6 x 3.0 m(3), wall thickness 10 cm and density of 1.73 x 10(3) kg m(-3) in eight cities across Southwestern Nigeria. The Mustonen method of calculating gamma-ray annual exposure rate from the radioactivity concentrations (Bq kg(-1)) of (226)Ra, (232)Th and (40)K in the blocks have been adopted with modifications to suit the Nigerian situation. The specific absorbed dose rates obtained were as follows: 11.36, 14.94 and 0.92 microGy y(-1) per Bq kg(-1) for (226)Ra, (232)Th and (40)K, respectively. These dose rates were used to calculate the annual effective dose in the model dwelling. The annual effective dose obtained varied between 209.20 (Osogbo) and 400.36 microSv y(-1) (Abeokuta). The values are in the range of values obtained for the German Democratic Republic (309 microSv y(-1)) and Jordan (470 microSv y(-1)).     

Population dose due to building materials in Ibadan, Nigeria

The natural radionuclide contents of some concrete building blocks randomly sampled in the city of Ibadan have been determined using NaI(Tl) gamma ray spectrometry. The radionuclides 226Ra, 232Th and 40K were determined with city mean specific activities 47 +/- 21 Bq.kg-1, 52 +/- 21 Bq.kg-1, and 352 +/- 222 Bq.kg-1, respectively. These activities amount to a radium equivalent of about 150 Bq.kg-1, which is lower than the recommended maximum value of 370 Bq.kg-1. The mean value of the external hazard index was found to be 0.41 which implies that the building blocks used in the city of Ibadan are within the acceptable level of radioactivity. The mean indoor gamma dose equivalent to individuals due to the walls was calculated to be 412 microSv.y-1 and the collective dose equivalent 563 man.Sy.y-1.     

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).     

Body radioactivity and radiation dose from 40K in Bangladeshi subjects measured with a whole-body counter

A group of subjects of Bangladeshi adults from both sexes were studied for internal radioactivity and effective dose by measuring the whole-body activity of naturally occurring (40)K using a whole-body counter. The mean activity concentration in the whole body and effective dose due to naturally occurring (40)K for the average male were found to be 2.0 +/- 0.4 Bq.g(-1) and 100 +/- 26 microSv.y(-1), respectively and those for the average female were 1.7 +/- 0.3 Bq.g(-1) and 100 +/- 20 microSv.y(-1), respectively. The mean activity concentration in the whole body and effective dose for both sexes were 1.9 +/- 0.4 Bq.g(-1) and 100 +/- 25 microSv.y(-1), respectively. The effective dose from (40)K for subjects is below the value reported by the UNSCEAR.     

Radioactivity concentrations in soil and dose assessment for Samsun City Centre, Turkey

In this study, natural gamma radioactivity levels were determined in the soil samples of the Samsun city centre by using the gamma ray spectrometry method. The analysis carried out with the high-purity germanium gamma spectrometry system has shown that average activity concentrations of (238)U, (232)Th, (40)K and (137)Cs were 19±2, 22±4, 521±23 and 15±1 Bq kg(-1), respectively. From the gamma analysis of soil samples, the average value of the absorbed gamma dose rates in air and the average value of the external annual effective dose rates were calculated as 45±4 nGy h(-1) and 55±5 μSv y(-1), respectively. The external hazard index has also been calculated and it has been found that the radiation hazard in Samsun is insignificant.     

Radioactivity concentrations and dose assessment in surface soil samples from east and south of Marmara region, Turkey

The activity concentrations of 137Cs, 40K, 232Th, 238U and 226Ra were measured in surface soil samples from East and South of Marmara region, Turkey. The physico-chemical parameters (organic matter, CaCO3 contents and pH-value) of the soil samples were determined in the samples collected from 100 sampling stations. The average activity concentrations of 137Cs, 40K, 232Th, 238U and 226Ra were found to be 27.46+/-21.84, 442.51+/-189.85, 26.63+/-15.90, 21.77+/-12.08 and 22.45+/-13.31 Bq kg(-1), respectively. The mean value of total annual external gamma radiation dose equivalent for the natural radionuclides was calculated to be 54.86 microSv. The current data were compared with those found in the other locations of Turkey and different countries.     

Radioactivity in soil from the city of Kavadarci (Republic of Macedonia) and its environs

The activity concentrations and distribution of natural and anthropogenic radionuclides in soils from the city of Kavadarci, Republic of Macedonia, and its environs were investigated. The purpose of the study, the first of this kind in this region was to evaluate the environmental radioactivity and radiological health hazard, as well as to determine the connection between the concentration of natural radionuclides and the geology of the terrain. A total of 45 surface soil samples were collected from evenly distributed sampling sites. Gross alpha and gross beta activity measurements were made using a gas flow proportional counter, while the activity concentrations of gamma emitting radionuclides were measured using a high purity germanium detector. The average activity concentrations of ??K, 22?Ra, 232Th and 13?Cs were found to be 546±118, 38.8±14.6, 43.7±18.4 and 41.5±40 Bq kg?1, respectively. The mean values of gross alpha and gross beta activities were 522±192 and 681±146 Bq kg?1. The mean total absorbed dose rate in air calculated from the concentration of the natural radionuclides was 67.1±20.9 nGy h?1, and the corresponding annual effective dose rate outdoors was 0.082±0.026 mSv y?1. The results of the analysis show strong correlation between the abundance of the natural radionuclides in soils and their geological origin.     

Natural radioactivity and external gamma radiation exposure at the coastal Red Sea in Egypt

Radionuclides which present in different beach sands are sources of external exposure that contribute to the total radiation exposure of human. In this work, superficial samples of beach sand were collected from the Red Sea coastline (Ras Gharib, Hurghada, Safaga, Qusier and Marsa Alam areas) and at 20 km on Qena-Safaga road. The distribution of natural radionuclides in sand beach samples was studied by gamma spectrometry. The activity concentrations of primordial and artificial radionuclides in samples that are collected from the coastal environment of the Red Sea were 19.2 +/- 3 Bq kg(-1) for (210)Pb, 21.1 +/- 1 Bq kg(-1) for (226)Ra, 22.7 +/- 2 Bq kg(-1) for (238)U, 1.0 +/- 0.1 Bq kg(-1) for (235)U, 11.6 +/- 1 Bq kg(-1) for (228)Ra, 13.0 +/- 1 Bq kg(-1) for (228)Th, 12.4 +/- 1 Bq kg(-1) for (232)Th, 930 +/- 32 Bq kg(-1) for (40)K and 1.2 +/- 0.3 Bq kg(-1) for (137)Cs. The mean external gamma-dose rate was 62.5 +/- 3.2 nSv h(-1), 54.4 +/- 2.8 nGy h(-1) Ra equivalent activity (Ra(eq)) was 107 +/- 5.8 Bq kg(-1), 0.86 +/- 0.04 Bq kg(-1) for representative level index (I(gamma)) and effective dose rate was 0.067 +/- 0.003 mSv y(-1) in beach sand red sea, in air due to naturally occurring radionuclides.     

Dose rate assessment of terrestrial gamma radiation in the Delta region of Nigeria

In situ gamma spectroscopy has been employed to characterise natural radiation in the soil at 32 locations in the Delta region of Nigeria. The outdoor gamma dose rates in the air due to 40K, 238U and 232Th in the soil were 1.5 +/- 0.9 nGy h(-1), 6.9 +/- 1.6 nGy h(-1) and 16.3 +/- 3.1 nGy h(-1) respectively. The estimated total annual outdoor effective dose to the people in the region was 31.6 microSv y(-1).     

Outdoor radioactivity and health risks in Balikesir, northwestern Turkey

External irradiation from radionuclides naturally present in the environment or released from man-made practices or events is usually an important component of the exposure of human populations. These exposures derive primarily from gamma radiation arising from the decay of these radionuclides at locations outside the human body. The main objective of this study is to evaluate the radioactivity levels and health risks due to terrestrial radionuclides in the soil of Balikesir, one of the largest cities of the country, northwestern Turkey. For this purpose, activity concentrations of radionuclides in soil and outdoor gamma dose rates (terrestrial and cosmic) have been investigated in the city of Balikesir. In addition, maps for the radionuclide activity concentrations of soil and the outdoor gamma dose rate distributions have been plotted for the region. The average activities of radionuclides, (238)U, (232)Th, (40)K, (235)U and (137)Cs in the soil were determined to be 37.6 ± 10.8, 54.7 ± 15.1, 674.5 ± 203.2, 3.6 ± 1.6, 3.4 ± 2.2 Bq kg(-1), respectively, in the region. The average outdoor gamma dose rates due to terrestrial and cosmic radiations were found to be 78.5 ± 12.4 and 48.9 ± 5.8 nGy h(-1) with the total of 127.4 ± 18.9 nGy h(-1) in the region. Annual effective dose due to environmental outdoor gamma radiation exposures was determined to be 156.3 nSv. The mean estimated cancer risk values were found to be 0.063 × 10(-2) for the region using risk factors of ICRP 103. The results of the study were discussed with the studies done in other cities of Turkey and the worldwide averages.