Radioactivity concentrations and dose assessment for soil samples around Adana, Turkey

The concentrations of natural radionuclides in surface soils around Adana, Turkey were determined using gamma ray spectrometry with an HPGe detector. The natural gamma ray radioactivity of the terrestrial radionuclides in air was calculated throughout different areas of Adana. The average activity concentrations of (238)U, (232)Th and (40)K were found to be 17.6, 21.1 and 297.5 Bq kg(-1), respectively. Outdoor gamma dose measurements in air 1m above ground level were determined by using a portable gamma scintillation detector. The gamma dose measurements in air were taken from the same places where soil samples were taken. Average outdoor gamma dose rates in sample stations were determined as 67 nGy h(-1). The annual effective dose to the public was found to be 82 microSv.     

Gamma dose rates and distribution of natural radionuclides in sand beaches--Ilha Grande, Southeastern Brazil

In order to study the process of dispersion and the activity concentration of 232Th and 238U series and 40K radionuclides in two island beaches in southeastern Brazil, analyses was made of sand samples of 0-10 cm profile, during a 12-month period. Moreover, the monthly variations of gamma dose rates were studied to determine the local environment absorbed dose rate. The average activity concentration of primordial radionuclides 232Th, 238U and 40K at Preta beach, they were 239, 121 and 110 Bq kg(-1), while at Dois Rios beach they were 48, 39 and 412 Bq kg(-1), respectively. The absorbed dose rate in air, observed at 1 m above the ground, ranged from 54 to 228 nGy h(-1) at Preta beach and from 39 to 110 nGy h(-1) at Dois Rios beach. The annual effective dose equivalent corresponding to Preta beach is 0.15 mSv a(-1) and to Dois Rios 0.08 mSv a(-1).     

Evaluation of technologically enhanced natural radiation near the coal-fired power plants in the Lodz region of Poland

Radionuclide releases together with escaping fly ashes (from 45 x 10(6) kg in previous decades to 8 x 10(6) kg annually in 1996) from the main local and several small coal-fired power plants resulted in a relatively small increase in natural radioactivity levels in the Lodz region. The natural gamma terrestrial radiation dose rates (1 m above ground level) were measured at 82 points including in the vicinity of power plants, in the center of the town and on edge of the town. The average dose rate value for the first area was 36 +/- 1.2 nGy h (-1), whereas the same dose rate for the edge of town was slightly lower 30 +/- 0.9 nGy h (-1) but this difference was statistically significant. Further confirmation of the technologically slightly enhanced exposure of the local population to natural radionuclides was achieved by gamma-spectrometry measurement of the uranium and thorium decay series radionuclides in the surface soil profiles (up to 30 cm depth). The average increase of 226Ra and 232Th radionuclides in the top layer of soil (0-10 cm) according to the 20+/-30 cm depth layer was 21% and 17%, respectively. However, due to the relatively low levels of 232Th (14.3 Bq kg (-1)) and 238U (16.8 Bq kg (-1)) in this area, the annual average effective dose from the natural terrestrial radiation for the local population is also relatively low, 0.28 mSv only.     

Environmental 238U and 232Th concentration measurements in an area of high level natural background radiation at Palong, Johor, Malaysia

Concentrations of uranium-238 and thorium-232 in soil, water, grass, moss and oil-palm fruit samples collected from an area of high background radiation were determined using neutron activation analysis (NAA). U-238 concentration in soil ranged from 4.9 mg kg(-1) (58.8 Bq kg(-1)) to 40.4 mg kg(-1) (484.8 Bq kg(-1)), Th-232 concentration ranged from 14.9 mg kg(-1) (59.6 Bq kg(-1)) to 301.0 mg kg(-1) (1204 Bq kg(-1)). The concentration of U-238 in grass samples ranged from below the detection limit to 0.076 mg kg(-1) (912 mBq kg(-1)), and Th-232 ranged from 0.008 mg kg(-1) (32 mBq kg(-1)) to 0.343 mg kg(-1) (1.372 Bq kg(-1)). U-238 content in water samples ranged from 0.33 mg kg(-1) (4.0 Bq L(-1)) to 1.40 mg kg(-1) (16.8 Bq L(-1)), and Th-232 ranged from 0.19 mg kg(-1) (0.76 Bq L(-1)) to 0.66 mg kg(-1) (2.64 Bq L(-1)). It can be said that the concentrations of environmental U-238 and Th-232 in grass and water samples in the study area are insignificant. Mosses were found to be possible bio-radiological indicators due to their high absorption of the heavy radioelements from the environment.     

Specific activity and hazards of granite samples collected from the Eastern Desert of Egypt

Fifty granitic rock samples were collected from different plutons in the central part of the Eastern Desert of Egypt and were analyzed for specific concentrations of (238)U, (232)Th and (40)K radionuclei. The measurements were carried out using a high performance and stability Nomad Plus spectroscopy system attached to a 1.7 keV (FWHM) HPGe detector. The spectra were analyzed using the direct gamma counting comparison method as well as the traditional absolute efficiency curve method. The highest average value of (238)U concentration (1184 Bq kg(-1)) was observed at EI Misikat region whereas the highest average values of (40)K and (232)Th concentration (2301.8 and 162.5 Bq kg(-1) respectively), were detected at Gabal Homret Waggat area. The radium equivalent activity (Ra(eq)), the absorbed dose rate (D), the external hazard index (H(ex)) and the annual gonadal dose equivalent were also calculated and compared to the international recommended values. Radon exhalation rate from the rock samples were measured using the activated charcoal canister method. The average value of radon exhalation varies from 0.052 to 0.69 Bq m(-2) h(-1) and depends on the specific concentration of uranium.     

Gamma radiation measurements and dose rates in commercially-used natural tiling rocks (granites)

The gamma radiation in samples of a variety of natural tiling rocks (granites) imported in Cyprus for use in the building industry was measured, employing high-resolution gamma-ray spectroscopy. The rock samples were pulverised, sealed in 1-l plastic Marinelli beakers, and measured in the laboratory with an accumulating time between 10 and 14 h each. From the measured gamma-ray spectra, activity concentrations were determined for (232)Th (range from 1 to 906 Bq kg(-1)), (238)U (from 1 to 588 Bq kg(-1)) and (40)K (from 50 to 1606 Bq kg(-1)). The total absorbed dose rates in air calculated from the concentrations of the three radionuclides ranged from 7 to 1209 nGy h(-1) for full utilization of the materials, from 4 to 605 nGy h(-1) for half utilization and from 2 to 302 nGy h(-1) for one quarter utilization. The total effective dose rates per person indoors were determined to be between 0.02 and 2.97 mSv y(-1) for half utilization of the materials. Applying dose criteria recently recommended by the EU for superficial materials, 25 of the samples meet the exemption dose limit of 0.3 mSv y(-1), two of them meet the upper dose limit of 1 mSv y(-1) and only one clearly exceeds this limit.     

Estimation of internal radiation dose to the adult Asian population from the dietary intakes of two long-lived radionuclides

Daily dietary intakes of two naturally occurring long-lived radionuclides, 232Th and 238U, were estimated for the adult population living in a number of Asian countries, using highly sensitive analytical methods such as instrumental and radiochemical neutron activation analysis (INAA and RNAA), and inductively coupled plasma mass spectrometry (ICP-MS). The Asian countries that participated in the study were Bangladesh (BGD), China (CPR), India (IND), Japan (JPN), Pakistan (PAK), Philippines (PHI), Republic of Korea (ROK) and Vietnam (VIE). Altogether, these countries represent more than 50% of the world population. The median daily intakes of 232Th ranged between 0.6 and 14.4 mBq, the lowest being for Philippines and the highest for Bangladesh, and daily intakes of 238U ranged between 6.7 and 62.5 mBq, lowest and the highest being for India and China, respectively. The Asian median intakes were obtained as 4.2 mBq for 232Th and 12.7 mBq for 238U. Although the Asian intakes were lower than intakes of 12.3 mBq (3.0 ug) 232Th and 23.6 mBq (1.9 ug) 238U proposed by the International Commission on Radiological Protection (ICRP) for the ICRP Reference Man, they were comparable to the global intake values of 4.6 mBq 232Th and 15.6 mBq 238U proposed by the United Nation Scientific Commission on Effects of Radiation (UNSCEAR). The annual committed effective doses to Asian population from the dietary intake of 232Th and 238U were calculated to be 0.34 and 0.20 microSv, respectively, which are three orders of magnitude lower than the global average annual radiation dose of 2400 microSv to man from the natural radiation sources as proposed by UNSCEAR.     

Natural radioactivity measurements in the city of Ptolemais (Northern Greece)

Specific activities of the natural radionuclides (238)U, (226)Ra, (232)Th and (40)K were measured by means of gamma-ray spectrometry in surface soil samples collected from the city of Ptolemais, which is located near lignite-fired power plants. The mean activity values for (238)U, (226)Ra, (232)Th and (40)K were found to be 42+/-11, 27+/-6, 36+/-5 and 496+/-56 Bq kg(-1), respectively. These values fall within the range of typical world and Greek values for soil. The indoor radon concentration levels, which were also measured in 66 dwellings by means of SSNTD, ranged from 12 to 129 Bq m(-3), with an average value of 36+/-2 Bq m(-3). This value is close to world and Greek average values for indoor radon concentrations. The total effective dose due to outdoor external irradiation of terrestrial origin and to indoor internal irradiation from the short-lived decay products of (222)Rn was estimated to be 1.2 mSv y(-1) for adults, which is lower than the global effective dose due to natural sources of 2.4 mSv y(-1).     

Estimation of annual effective dose due to natural radioactive elements in ingestion of foodstuffs in tin mining area of Jos-Plateau, Nigeria

Soils and food crops from a former tin mining location in a high background radiation area on the Jos-Plateau, Nigeria were collected and analyzed by gamma spectrometry to measure their contents of 40K, 238U and 232Th. As well as collecting samples, in situ dose rates on farms were measured using a precalibrated survey meter. Activity concentrations determined in food crops were compared with the local food derivatives or diets to investigate the possible removal or addition of radionuclides during food preparation by cooking or other means. Potassium-40 was found to contribute the highest activity in all the food products. The activity concentration of 40K, 238U and 232Th in local prepared diets ranged between 60 and 494 Bq kg-1, between BDL and 48 Bq kg-1 and between BDL and 17 Bq kg-1, respectively. The internal effective dose to individuals from the consumption of the food types was estimated on the basis of the measured radionuclide contents in the food crops. It ranged between 0.2 microSv y-1 (beans) and 2164 microSv y-1 (yam) while the annual external gamma effective dose in the farms due to soil radioactivity ranged between 228 microSv and 4065 microSv.     

Daily ingestion of 232Th, 238U, 226Ra, 228Ra and 210Pb in vegetables by inhabitants of Rio de Janeiro City

The concentrations of the naturally occurring radionuclides 232Th, 238U, 210Pb, 226Ra and 238Ra were determined in the vegetables (leafy vegetables, fruit, root, bean and rice) and derived products (sugar, coffee, manioc flour, wheat flour, corn flour and pasta) consumed most by the adult inhabitants of Rio de Janeiro City. A total of 88 samples from 26 different vegetables and derived products were analyzed. The highest contribution to radionuclide intake arises from bean, wheat flour, manioc flour, carrot, rice, tomato and potato consumption. The estimated daily intakes due to the consumption of vegetables and derived products are 1.9 mBq of 232Th (0.47 microg), 2.0 mBq of 238U (0.17 microg), 19 mBq of 236Ra, 26 mBq of 210Pb and 47 mBq of 228Ra. The estimated annual effective dose due to the ingestion of vegetables and their derived products with the long-lived natural radionuclides is 14.5 microSv. Taking into account literature data for water and milk from Rio de Janeiro the dose value increases to 29 microSv, with vegetables and derived products responsible for 50% of the dose and water for 48%. 210Pb (62%) and 228Ra (24%) were found to be the main sources for internal irradiation.     

Natural radioactivity and radiation exposure in the high background area at Chhatrapur beach placer deposit of Orissa, India

A high natural background radiation area is reported for the Chhatrapur beach placer deposit of Orissa state, on the southeastern coast of India, due to the presence of radiogenic heavy minerals. The average activity concentrations of radioactive elements 232Th, 238U and 40K were measured by gamma-ray spectrometry using a HPGe detector, and found to be 2500 +/-1850, 230 +/- 140 and 120 +/- 35 Bq kg-1, respectively, for the bulk sand samples. The absorbed gamma dose rates in air due to the naturally occurring radionuclides varied from 375 to 5000 nGy h-1, with an average value of 1625 +/- 1200 nGy h-1. The external annual effective dose rate of the region ranged from 0.46 to 6.12 mSv y-1, with an average value of 1625 +/- 1200 mSv y-1. The absorbed gamma dose rate levels of Chhatrapur beach area were similar to the monazite sand-bearing high background radiation areas of southern and southwestern coastal tracts of India and other similar areas of the world. The major contributors to the enhanced level of radiation are monazite and zircon sands.     

Natural activities of 40K, 238U and 232Th in elephant grass (Pennisetum purpureum) in Ibadan metropolis, Nigeria

Samples of elephant grass collected at some pasturing farmlands across different locations in Ibadan metropolis were analyzed for their natural radioactivity concentrations due to 40K, 238U and 232Th radionuclides. Radioactivity measurements were carried out using gamma-ray spectroscopy. The average radioactivity concentration of 40K was found to be 25.7+/-5.5 Bq kg(-1) for 238U and 33.4+/-3.9 Bq kg(-1) for 232Th. The radiological health implication to the population that may result from these values is found to be very low and almost insignificant. No artificial radionuclide, however, was detected in any of the samples, hence, measurements have been taken as representing baseline values of these radionuclides in the grass in the metropolis.     

Natural radioactivity measurements in building materials in Southern Lebanon

Using gamma-spectroscopy and CR-39 detector, concentration C of naturally occurring radioactive nuclides (226)Ra, (222)Rn, (214)Bi, (228)Ac, (212)Pb, (212)Bi and (40)K, has been measured in sand, cement, gravel, gypsum, and paint, which are used as building materials in Lebanon. Sand samples were collected from 10 different sandbank locations in the southern part of the country. Gravel samples of different types and forms were collected from several quarries. White and gray cement fabricated by Shaka Co. were obtained. gamma-spectroscopy measurements in sand gave Ra concentration ranging from 4.2+/-0.4 to 60.8+/-2.2 Bq kg(-1) and Ra concentration equivalents from 8.8+/-1.0 to 74.3+/-9.2 Bq kg(-1). The highest Ra concentration was in gray and white cement having the values 73.2+/-3.0 and 76.3+/-3.0 Bq kg(-1), respectively. Gravel results showed Ra concentration between 20.2+/-1.0 and 31.7+/-1.4 Bq kg(-1) with an average of 27.5+/-1.3 Bq kg(-1). Radon concentration in paint was determined by CR-39 detector. In sand, the average (222)Rn concentration ranged between 291+/-69 and 1774+/-339 Bq m(-3) among the sandbanks with a total average value of 704+/-139 Bq m(-3). For gravel, the range was found to be from 52+/-9 to 3077+/-370 Bq m(-3) with an average value of 608+/-85 Bq m(-3). Aerial and mass exhalation rates of (222)Rn were also calculated and found to be between 44+/-7 and 2226+/-267 mBq m(-2)h(-1), and between 0.40+/-0.07 and 20.0+/-0.3 mBq kg(-1)h(-1), respectively.     

Natural radioactivity and dose assessment for phosphate rocks from Wadi El-Mashash and El-Mahamid Mines, Egypt

The activity concentrations of (226)Ra, (232)Th and (40)K have been measured by gamma spectroscopy (sodium iodide NaI(Tl) detector) in phosphate rock samples, collected from the Wadi El-Mashash, a site located in the central eastern desert, and El-Mahamid in the Nile valley, Egypt. The average activity concentrations of (226)Ra, (232)Th and (40)K (Bq kg(-1)) in phosphate rocks were 665.8+/-33.4, 329.4+/-17 and 587.6+/-29.4 for Wadi El-Mashash and 566.8+/-28.6, 217.3+/-11.8 and 560.1+/-28 for El-Mahamid, respectively. The corresponding values for shale rocks were 85.2+/-5.7, 93.3+/-5.6 and 303.1+/-15.2 Bq kg(-1), respectively. As a measure of radiation hazard to the occupational workers and public, the Ra equivalent activities, representative level index and dose rates due to natural radionuclides at 1 m above the ground surface were estimated. The calculated external gamma-radiation dose received by the workers of the phosphate mine are 538 and 418 microSv/y, which is far below the permitted dose of 20 mSv/y recommended by the International Commission of Radiation Protection [ICRP-60, 1990. Radiation Protection: 1990 Recommendation of the International Commission on Radiological Protection, Oxford, Pergamon Preis.] for workers.     

The application of phosphogypsum in agriculture and the radiological impact

Radium-226 in phosphogypsum produced in a phosphate industry, SICNG operating at Thessaloniki, Northern Greece since May 1966, varied from 261 to 688 Bq kg(-1) (mean value 508 Bq kg(-1)). This radionuclide in soil tilled with phosphogypsum used for agricultural purposes varied from 50 to 479 Bq kg(-1) (average 205 Bq kg(-1)), while in the regular soil of cultivated fields it varied from 37 to 54 Bq kg(-1) (average 48 Bq kg(-1)). Radium-226 in rice originated from cultivated fields tilled with phosphogypsum or not varied from 0.36 to 1.98 Bq kg(-1) (average 1.53 Bq kg(-1)) with the higher values observed in samples originated from cultivated fields tilled with phosphogypsum. Radium-226 transfer factors, TF, from soil tilled with phosphogypsum to plants for the case of rice varied from 6.5 x 10(-3) to 2.0 x 10(-2) (geometric mean: 1.1 x 10(-2)). A mean (226)Ra content in rice 1.53 Bq kg(-1) results in a daily intake of (226)Ra by humans in Greece 0.0084 Bq day(-1) leading to an annual effective dose for adults 0.86 microSv y(-1) which is much less in contributing to the average exposure to natural radiation sources (2.4 mSv y(-1)) and particularly to the part due to ingestion (0.29 mSv y(-1)). It is necessary to continuously control (monitoring) (226)Ra in phosphogypsum before any use for agricultural purposes.     

90Sr, 238U, 234U, 137Cs, 40K and 239/240Pu in Emmental type cheese produced in different regions of Western Europe

A method is presented for the determination of (90)Sr and uranium in Emmental type cheese collected in dairy plants from different European countries. Results display a significant correlation (r = 0.708 Student t-test = 6.02) between the (90)Sr content of the cheese and the altitude of grazing. The highest (90)Sr activity is 1.13 Bq kg(-1) of cheese and the lowest is 0.29 Bq kg(-1). Uranium activity is very low with a highest (238)U value of 27 mBq kg(-1). In addition, (234)U/(238)U ratio shows a large enrichment in (234)U for every location. Without any significant indication of the geographic origin of the cheese, this enrichment is believed to be due to the geological features of the pasture, soil and underground water. These results tend to prove that the contamination of milk by uranium originates principally from the water that the cows drink instead of the forage. This finding may have a great importance in models dealing with dairy food contamination by radionuclides following a nuclear accident. Also, the (90)Sr content and to a lesser extent the (234)U/(238)U ratio could be used to trace the authenticity of the origin of the cheese. (137)Cs activity is lower than the detection limit of 0.1 Bq kg(-1) in all the samples collected (n = 20). Based on natural (40)K activity in cheese (15-21 Bq kg(-1)), the decontamination factor for the alkaline cations from milk to cheese is about 20. Plutonium activity stays below the detection limit of 0.3 mBq kg(-1).     

Distribution of some natural gamma-emitting radionuclides in the soils of the coastal areas of Nigeria

Studies on the radiation level and the radionuclide distribution of some naturally occurring radioactive materials (NORM) in the soils of the coastal areas of Southern Nigeria were undertaken. The purpose of this study is to provide baseline data for the effective monitoring of unforeseeable radioactive fallout in these areas where a lot of oil exploration activities are going on. The radioactivity concentrations of these naturally occurring radionuclides (specifically (40)K, (238)U and (232)Th) in the soil samples were analyzed using a high-resolution, low-background, hyper-pure coaxial gamma-ray detector (EG&G ORTEC HPGe) coupled to an amplifier and multi-channel analyzer. The activity of (40)K ranges between 111.9 and 444.7 kBq kg(-1) with a median value of 283.28 kBq kg(-1); the activity of (226)Ra (a daughter of (238)U) varies from 23.24 to 43.66 kBq kg(-1) with a median value of 34.54 kBq kg(-1); and that of (232)Th ranges from 6.45 to 12.79 kBq kg(-1) with a median value of 9.17 kBq kg(-1). The mean absorbed dose rate in air due to these NORM is found to be (33.655+/-3.409) nGy h(-1). The correlation analyses showed a positive relationship between the three radionuclides in all the five coastal states.     

Characteristics, spatial distribution and vertical profile of gamma-ray emitting radionuclides in the coastal environment of North Sinai

Radionuclide concentrations of beach and dune sand from various sites in Al-Arish city and surrounding area, North Sinai, Egypt, were measured. The sampling sites included locations in the local harbor, Al-Arish valley and Zaranik protected area. The results indicate that the activities of the products of (232)Th and (226)Ra series in samples from the harbor and along the beach were higher than those from non-coastal sites. The activity concentrations of (232)Th for beach sand ranged from 2.3 to 506.5 Bq/kg with an average of 83.4 Bq/kg, while that for dune sand ranged from 2.2 to 15.1 Bq/kg with an average of 6.4 Bq/kg. The average activity concentration of (226)Ra for beach sand was 56.0 Bq/kg (2.9-261.5 Bq/kg), while that for dune sand was 6.5 Bq/kg (3.0-14.7 Bq/kg). The average activity concentrations of (40)K for beach and dune sand were 88.1 Bq/kg and 178.4 Bq/kg, respectively. Six depth profiles in the harbor area were measured up to a depth of 1m within more than two years. These sets of measurements allowed the determination of the migration rate of black sand to be 0.094 cm/day. Samples with the smallest grain size (<0.2 mm) were found to have the highest level of activities, which were attributed to their high content of black sand. No risk exists for public health based on the calculated effective dose equivalent and the recommended limit of 5 mSv/y. On the other hand, local children and adults may receive doses higher than this recommended limit in two locations in the Zaranik protected area according to a model developed in this study.     

Biomagnification of 7Be, 234Th, and 228Ra in marine organisms near the northern Pacific coast of Japan

Enrichment of natural radionuclides of thorium, radium and beryllium in several kinds of marine organisms was investigated near the Pacific coast of Miyagi Pref., Japan. The radioactivity of 7Be, 210Pb, 234Th, 238U, 228Ra and 137Cs was measured using gamma spectrometry. High concentrations of 234Th were observed in ascidian livers (50-400 Bq/kg dry) and excrement (2000-2900 Bq/kg dry), although the parent 238U concentrations were less than 3 Bq/kg dry. Such extreme disequilibrium between 238U and 234Th activity was observed in other organisms (barnacles, mussels and brown algae). Relatively high concentrations of 228Ra were detected in ascidian livers and were observed to decrease according to its half-life (5.75 year), suggesting disequilibrium with its parent 232Th. High concentrations (about 1900-5000 Bq/kg dry) of 7Be were detected in ascidian liver. Possible mechanisms for the observed biomagnification and bioaccumulation of these radionuclides in the organisms analyzed were proposed.     

Intake of uranium and radium-226 due to food crops consumption in the phosphate region of Pernambuco--Brazil

The phosphate region located in the Northeast of Brazil covers an area of approximately 150 km long with an average width of 4 km, along the coast of the states of Pernambuco and Paraíba. The inhabitants of this area are exposed to natural radioactivity levels higher than the background values recorded in the literature, mainly due to the presence of uranium and its decay products in the phosphatic sediments. The main aim of this study was to determine the activity concentration of uranium and (226)Ra in foodstuffs cultivated in this area, where the phosphate mineral has been extracted. The activity concentrations found for uranium and (226)Ra in the foodstuffs analyzed varied from 13 to 186 mBq kg(-1) (wet weight), with a mean value of 46 mBq kg(-1) and from 43 to 2209 mBq kg(-1) (wet weight), with a mean value of 358 mBq kg(-1), respectively. The annual intake of these radionuclides, for rural residents, was 7.45 Bq for uranium and 69.3 Bq for (226)Ra.