Terrestrial Gamma Dose Research Articles

Mapping natural radioactivity of soils in the eastern Canary Islands

The Canary Islands archipielago (Spain) comprises seven main volcanic islands and several islets that form a chain extending for around 500 km across the eastern Atlantic, between latitudes 27°N and 30°N, with its eastern edge only 100 km from the NW African coast. The administrative province of Las Palmas comprises the three eastern Canary Islands (Lanzarote, Fuerteventura and Gran Canaria). An extensive study of terrestrial gamma dose rates in surface soils has been carried out to cover the entire territory of the province (4093 km2). The average outdoor gamma dose rate in air at 1 m above ground is 73 nGyh−1 at Gran Canaria, 32 nGyh−1 at Fuerteventura, and 25 nGyh−1 at Lanzarote. To complete the radiological characterization of this volcanic area, 350 soil samples at 0–5 cm depth were collected to cover all the geologic typologies of the islands. These samples were measured using high resolution gamma spectrometry to determine the activity concentrations of 226Ra, 232Th and 40K. The average values obtained were 25.2 Bq/kg, 28.9 Bq/kg, and 384.4 Bq/kg, respectively. Maps of terrestrial gamma activity, effective dose, and activity concentrations of 226Ra, 232Th and 40K for the region have been developed through the use of geostatistical interpolation techniques. These maps are in accord with the geology of the islands.

Seasonal Variation of Terrestrial Gamma Radiation Dose and Evaluation of Annual Effective Dose in AECD Campus, Dhaka, Bangladesh

Background: Seasonal variations of environmental terrestrial gamma dose rates were measured at the Atomic Energy Centre Dhaka (AECD) campus in Shahbag Thana under Dhaka City from January to December 2015. Aim of the study: This kind of study is required to detect the natural and artificial radionuclides (if any) releasing from nuclear facilities in the country or from neighbouring countries. Materials and Methods: The measurement was performed using a portable High Purity Germanium (HPGe) detector (Model No. GEM25P4-83). The portable HPGe detector was placed at 1 meter above the ground facing downward and data acquisition time was 10,000 sec. Four locations were selected in the AECD campus to obtain the spectrum and those locations were marked out using global positioning system. Results: The average dose rate of the four locations from location-1 to location-4 were 0.428 ± 0.041, 0.344 ± 0.073, 0.355 ± 0.049 and 0.405 ± 0.054 µGy.h-1 respectively. The average dose rate of six seasons such as winter, spring, summer, rainy, autumn and late autumn were 0.377 ± 0.088, 0.421 ± 0.071, 0.385 ± 0.066, 0.358 ± 0.031, 0.281 ± 0.106 and 0.421 ± 0.023 µGy.h-1 respectively. The annual effective dose of the population due to the terrestrial gamma radiation were also calculated and it was varied from 0.208 - 0.627 mSv. The mean annual effective dose was found to be 0.472 ± 0.081 mSv which is comparable to the worldwide average value of 0.48 mSv.y-1. Conclusion: It was observed that winter, spring, summer and late autumn season’s dose rates are higher than those of rainy & autumn seasons.

Assessment of lithogenic radioactivity in the Euganean Hills magmatic district (NE Italy)

The Euganean Hills of North East Italy have long been recognised as an area characterized by a higher than average natural radiation background. This is due to two main reasons: a) primary lithogenic radiation due to rhyolitic and trachytic outcrops, which are “acidic alkaline” magmatic rocks potentially enriched in uranium and thorium; b) secondary sources related to a geothermal field – widely exploited for spa tourism in the area since the Roman age – producing surface release of radon-enriched fluids.Though radioactivity levels in the Euganean district have been often investigated in the past – including recent works aimed at assessing the radiation doses from radon and/or total gamma radiation – no effort has been put so far into producing a thorough assessment linking radiation protection data to geological-structural features (lithology, faults, water, organic matter content, etc.). This work represents the first part of the interdisciplinary project “Geological and geochemical control on Radon occurrence and natural radioactivity in the Euganean Hills district (North-Eastern Italy)”, aimed at producing detailed results of the actual radiation levels in connection mainly with lithological parameters.A detailed sampling strategy, based on lithostratigraphy, petrology and mineralogy, has been adopted. The 151 rock samples collected were analyzed by high resolution γ-ray spectrometry with ex situ HPGe detectors. Statistical and geostatistical analyses were performed, and outlier values of U and Th – possibly associated with anomalies in the geological formation – were identified. U, Th and K concentration maps were developed using both the entire database and then again after expunging the outliers; the two were then compared. In all maps the highest values can be associated to trachyte and rhyolite lithologies, and the lowest ones to sedimentary formations. The external dose due to natural radionuclides in the soil – the so called terrestrial gamma dose rate – has been calculated using the U, Th and K distribution measured in the bedrock samples.

A comparative study of terrestrial gamma dose rate in air measured by thermoluminescent dosimeter, portable survey meter and HPGe gamma spectrometer

In this paper, three different widely-used measurement techniques for environmental gamma dose rate were studied and compared, i.e., the thermoluminescent dosimeter, the portable survey meter and the spectrometric analysis. Thirteen investigation sites were selected, and the TLDs were arranged to accumulate the radiation signals during an interval of about one quarter, the instant dose rates by using a portable survey meter were collected around the site, and top surface soils were sampled in the surroundings for radionuclides analyzing in laboratory. The results from these methods were compared, which revealed high correlations. The differences and possible uncertainties for the three methods were analyzed, inspired a further study should be conducted to have more successful estimation of dose rate in surface air.

Modeling of geogenic radon in Switzerland based on ordered logistic regression

PurposeThe estimation of the radon hazard of a future construction site should ideally be based on the geogenic radon potential (GRP), since this estimate is free of anthropogenic influences and building characteristics. The goal of this study was to evaluate terrestrial gamma dose rate (TGD), geology, fault lines and topsoil permeability as predictors for the creation of a GRP map based on logistic regression. MethodSoil gas radon measurements (SRC) are more suited for the estimation of GRP than indoor radon measurements (IRC) since the former do not depend on ventilation and heating habits or building characteristics. However, SRC have only been measured at a few locations in Switzerland. In former studies a good correlation between spatial aggregates of IRC and SRC has been observed. That’s why we used IRC measurements aggregated on a 10 km × 10 km grid to calibrate an ordered logistic regression model for geogenic radon potential (GRP). As predictors we took into account terrestrial gamma doserate, regrouped geological units, fault line density and the permeability of the soil. ResultsThe classification success rate of the model results to 56% in case of the inclusion of all 4 predictor variables. Our results suggest that terrestrial gamma doserate and regrouped geological units are more suited to model GRP than fault line density and soil permeability. ConclusionOrdered logistic regression is a promising tool for the modeling of GRP maps due to its simplicity and fast computation time. Future studies should account for additional variables to improve the modeling of high radon hazard in the Jura Mountains of Switzerland.

Natural radioactivity measurements in Pahang State, Malaysia

This study was aimed at providing the baseline data of terrestrial gamma dose rates and natural radioactivity to assess the corresponding health risk in the ambient environment of the Pahang State. Terrestrial gamma radiation (TGR) from 640 locations was measured with the mean value found to be 176 ± 5 nGy h−1. Ninety-eight soil samples were analysed using a high-purity germanium detector (HPGe), and the mean concentrations of the radionuclides 226Ra, 232Th and 40K are 110 ± 3, 151 ± 5 and 542 ± 51 Bq kg−1, respectively.226Ra and 232Th concentrations were found to be three times the world average, while that of 40K is quite higher than the world average value. The acid-intrusive geological formation has the highest mean concentrations for 226Ra (215 ± 6 Bq kg−1), 232Th (384 ± 12 Bq kg−1) and 40K (1564 ± 153 Bq kg−1). The radium equivalent activities (Req) and the external hazard index (Hex) for the various soil types were also calculated. Some of the soil types were found to have values exceeding the internationally recommended levels of 370 Bq kg−1 and the unity value, respectively.

Terrestrial gamma dose rate, radioactivity and radiological hazards in the rocks of an elevated radiation background in Juban District, Ad Dali’ Governorate, Yemen

This study aims to evaluate natural radiation and radioactivity in the rock and to assess the corresponding health risk in a region of elevated background radiation in Juban District, Ad Dali’ Governorate, Yemen. The mean external gamma dose rate was 374 nGy h−1 which is approximately six times the world average. The measured results were used to compute annual effective dose equivalent, collective effective dose and excess lifetime cancer risk, which are 2.298 mSv, 61.95 man Sv y−1 and 8.043 × 10−3, respectively. Rocks samples from different geological formations were analyzed for quantitative determination of 226Ra, 232Th and 40K. The specific activity of the rocks samples ranges from 7 ± 1 Bq Kg−1 to 12 513 ± 329 Bq Kg−1 for 232Th, from 6 ± 1 Bq kg−1 to 3089 ± 74 Bq kg−1 for 226Ra and 702 ± 69 Bq kg−1 to 2954 ± 285 Bq kg−1 for 40K. 232Th is the main contributor to gamma dose rate from the rock samples. Indicators of radiological health impact, radium equivalent activity and external hazard index are 3738 Bq kg−1 and 10.10, respectively. The mean external hazard index was ten times unity in the studied locations in Juban District, which is higher than the recommended value.

Predicting terrestrial gamma dose rate based on geological and soil information: case study of Perak state, Malaysia

An extensive terrestrial gamma radiation dose (TGRD) rate survey has been conducted in Perak State, Peninsular Malaysia. The survey has been carried out taking into account geological and soil information, involving 2930 in situ surveys. Based on geological and soil information collected during TGRD rate measurements, TGRD rates have been predicted in Perak State using a statistical regression analysis which would be helpful to focus surveys in areas that are difficult to access. An equation was formulated according to a linear relationship between TGRD rates, geological contexts and soil types. The comparison of in situ measurements and predicted TGRD dose rates was tabulated and showed good agreement with the linear regression equation. The TGRD rates in the study area ranged from 38 nGy h−1 to 1039 nGy h−1 with a mean value of 224 ± 138 nGy h−1. This value is higher than the world average as reported in UNSCEAR . The TGRD rates contribute an average dose rate of 1.37 mSv per year. An isodose map for the study area was developed using a Kriging method based on predicted and in situ TGRD rate values.

Lifetime Effective Dose Assessment Based on Background Outdoor Gamma Exposure in Chihuahua City, Mexico.

Determining ionizing radiation in a geographic area serves to assess its effects on a population’s health. The aim of this study was to evaluate the spatial distribution of the background environmental outdoor gamma dose rates in Chihuahua City. This study also estimated the annual effective dose and the lifetime cancer risks of the population of this city. To determine the outdoor gamma dose rate in air, the annual effective dose and the lifetime cancer risk, 48 sampling points were randomly selected in Chihuahua City. Outdoor gamma dose rate measurements were carried out by using a Geiger-Müller counter. Outdoor gamma dose rates ranged from 113 to 310 nGy·h−1. At the same sites, 48 soil samples were taken to obtain the activity concentrations of 226Ra, 232Th and 40K and to calculate their terrestrial gamma dose rates. Radioisotope activity concentrations were determined by gamma spectrometry. Calculated gamma dose rates ranged from 56 to 193 nGy·h−1. Results indicated that the lifetime effective dose of the inhabitants of Chihuahua City is on average 19.8 mSv, resulting in a lifetime cancer risk of 0.001. In addition, the mean of the activity concentrations in soil were 52, 73 and 1097 Bq·kg−1, for 226Ra, 232Th and 40K, respectively. From the analysis, the spatial distribution of 232Th, 226Ra and 40K is to the north, to the north-center and to the south of city, respectively. In conclusion, the natural background gamma dose received by the inhabitants of Chihuahua City is high and mainly due to the geological characteristics of the zone. From the radiological point of view, this kind of study allows us to identify the importance of manmade environments, which are often highly variable and difficult to characterize.

Activity Concentrations of Natural Radionuclides in Soils of Rainforest Sites in Western Ghats

Assessments of naturally occurring radionuclides in soil collected from a tropical rainforest forest of western Ghats, India were conducted. These radionuclides were distributed unevenly in the forest soil. For all soil samples, the terrestrial gamma dose rate and the corresponding outdoor annual effective dose equivalents were evaluated. The activity concentration of 232Th and average outdoor gamma dose rates were found to be higher than the global average which appears to affects Western Ghats environment in general, the radiological hazard indices were found to be within the International Commission on Radiological Protection recommended limits. Hence, obtained results for natural radionuclides in the forest soils were within the range specified by UNSCEAR (2000) report for virgin soils except 232Th.

Prediction of terrestrial gamma dose rate based on geological formations and soil types in the Johor State, Malaysia

This study aims to predict and estimate unmeasured terrestrial gamma dose rate (TGDR) using statistical analysis methods to derive a model from the actual measurement based on geological formation and soil type. The measurements of TGDR were conducted in the state of Johor with a total of 3873 measured points which covered all geological formations, soil types and districts. The measurements were taken 1 m above the soil surface using NaI [Ti] detector. The measured gamma dose rates ranged from 9 nGy h−1 to 1237 nGy h−1 with a mean value of 151 nGy h−1. The data have been normalized to fit a normal distribution. Tests of significance were conducted among all geological formations and soil types, using the unbalanced one way ANOVA. The results indicated strong significant differences due to the different geological formations and soil types present in Johor State. Pearson Correlation was used to measure the relations between gamma dose rate based on geological formation and soil type (DG,S) with the gamma dose rate based on geological formation (DG) or soil type (Ds). A very good correlation was found between DG,S and DG or DG,S and Ds. A total of 118 pairs of geological formations and soil types were used to derive the statistical contribution of geological formations and soil types to gamma dose rates. The contribution of the gamma dose rate from geological formation and soil type were found to be 0.594 and 0.399, respectively. The null hypotheses were accepted for 83% of examined data, therefore, the model could be used to predict gamma dose rates based on geological formation and soil type information.

Terrestrial Gamma Radiation Exposure in Bangka-Belitung Islands, Indonesia

Bangka-Belitung is known as tin producer and it geologically contains higher concentrations of natural radionuclides than most other areas. The aim of this study was to evaluate the level of terrestrial gamma radiation in Bangka-Belitung Islands. The external gamma radiation dose rate from terrestrial gamma-rays have been measured at one meter above the ground by means of a portable gamma spectrometer at 66 survey points. The terrestrial gamma dose rates in Bangka island range from 43.67 to 511.54 nGy h -1 with a mean of 183.45 nGy h -1 , while in Belitung island they range from 15.54 to 416.39 nGy h -1 with a mean of 132.60 nGy h-1. From this work, a strong correlation was found between dose rates found from in-situ radiation measurements and dose rates calculated theoretically from radioactivity contents of the soil at the same locations. Generally, Bangka-Belitung islands have higher outdoor natural gamma dose rates than the world average value of 0.058 μGy h -1 for the regions with normal background radiation specified by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). Received: 27 August 2014; Revised: 05 March 2015; Accepted: 30 March 2015

Radiological hazard associated with natural radionuclide concentrations in the northern part of Pahang state Malaysia

Radiological studies to determine the health hazard associated with concentrations of natural radionuclides 226Ra, 232Th and 40K in soils of northern part of Pahang state Malaysia were conducted. In situ measurement for external gamma radiation and soil samples was taken from different locations covering the entire districts of the study area. The in situ measurements were conducted using NaI[Ti] detector. The mean terrestrial gamma dose rate (TGDR) was found to be 185 ± 7 nGy h−1. The soil samples were measured using high-purity germanium detector (HPGe) and analyzed using Genie2000 software. The results obtained shows that the mean activity concentrations of the radionuclides 226Ra, 232Th and 40K in the area were 117 ± 4, 151 ± 5 and 622 ± 57 Bq kg−1, respectively. The Radium equivalent activities (R eq), External hazard index (H ex) and Annual Effective Dose (AED) out doors were also found to be 380 Bq kg−1, 1.027 and 0.210 mSv year−1, respectively. The results were compared with values given in United Nations Scientific Committee on the Effects of Atomic Radiation (2000).

Indoor terrestrial gamma dose rate mapping in France: a case study using two different geostatistical models

Terrestrial gamma dose rates show important spatial variations in France. Previous studies resulted in maps of arithmetic means of indoor terrestrial gamma dose rates by “departement” (French district). However, numerous areas could not be characterized due to the lack of data. The aim of our work was to obtain more precise estimates of the spatial variability of indoor terrestrial gamma dose rates in France by using a more recent and complete data base and geostatistics. The study was based on the exploitation of 97 595 measurements results distributed in 17 404 locations covering all of France. Measurements were done by the Institute for Radioprotection and Nuclear Safety (IRSN) using RPL (Radio Photo Luminescent) dosimeters, exposed during several months between years 2011 and 2012 in French dentist surgeries and veterinary clinics. The data used came from dosimeters which were not exposed to anthropic sources. After removing the cosmic rays contribution in order to study only the telluric gamma radiation, it was decided to work with the arithmetic means of the time-series measurements, weighted by the time-exposure of the dosimeters, for each location. The values varied between 13 and 349 nSv/h, with an arithmetic mean of 76 nSv/h. The observed statistical distribution of the gamma dose rates was skewed to the right. Firstly, ordinary kriging was performed in order to predict the gamma dose rate on cells of 1*1 km2, all over the domain. The second step of the study was to use an auxiliary variable in estimates. The IRSN achieved in 2010 a classification of the French geological formations, characterizing their uranium potential on the bases of geology and local measurement results of rocks uranium content. This information is georeferenced in a map at the scale 1:1 000 000. The geological uranium potential (GUP) was classified in 5 qualitative categories. As telluric gamma rays mostly come from the progenies of the 238Uranium series present in rocks, this information, which is exhaustive throughout France, could help in estimating the telluric gamma dose rates. Such an approach is possible using multivariate geostatistics and cokriging. Multi-collocated cokriging has been performed on 1*1 km2 cells over the domain. This model used gamma dose rate measurement results and GUP classes. Our results provide useful information on the variability of the natural terrestrial gamma radiation in France (‘natural background’) and exposure data for epidemiological studies and risk assessment from low dose chronic exposures.

Evaluation of radionuclides in the terrestrial environment of Western Ghats

The activity concentration of naturally occurring radionuclides in soil samples of an elevated radiation background area of Western Ghats were determined using gamma-ray spectrometry with the aim of evaluating the environmental radioactivity. The annual effective dose equivalent and the radiation hazard indices from the soil activity were estimated to reduce the harmful effects of gamma radiation to the population dwelling in the area. The activity concentrations of 232Th and average outdoor terrestrial gamma dose rate were found to be higher than the world average, this may affect Western Ghats environment in general. Therefore, the radiological risks to the general population from ionizing radiation from the naturally occurring radionuclides in the soil are considered to be significant. However, other radiological hazard indices were found to be within permissible limits.

Isodose mapping of terrestrial gamma radiation dose rate of Selangor state, Kuala Lumpur and Putrajaya, Malaysia

A terrestrial gamma radiation survey for the state of Selangor, Kuala Lumpur and Putrajaya was conducted to obtain baseline data for environmental radiological health practices. Based on soil type, geological background and information from airborne survey maps, 95 survey points statistically representing the study area were determined. The measured doses varied according to geological background and soil types. They ranged from 17 nGy h−1 to 500 nGy h−1. The mean terrestrial gamma dose rate in air above the ground was 182 ± 81 nGy h−1. This is two times higher than the average dose rate of terrestrial gamma radiation in Malaysia which is 92 nGy h−1 (UNSCEAR 2000). An isodose map was produced to represent exposure rate from natural sources of terrestrial gamma radiation.

Determination and evaluation of natural radioactivity and heavy metal levels in the aquatic environment of trans-boundary rivers: Maritza, Tundja and Arda

The main problem in the trans-boundary river system is that heavy metal and radioactive pollution can cause long-term effects on ecosystems. Therefore the natural radioactivity and heavy metal levels in the Maritza, Tundja and Arda Rivers, common for Bulgaria and Turkey, were determined for 3 years period (2007–2010). Gross alpha, gross beta and total radium isotopes activities, uranium and heavy metal concentrations of the surface water of the rivers were investigated and also terrestrial gamma and gamma dose rate were measured. The results were compared with reported data from other countries of the world and the recommended international standards. The results gathered in this study may provide background data on the natural radioactive and heavy metal levels of these trans-boundary rivers.

Annual effective dose of naturally occurring radionuclides in soil and sediment

In this study, the natural radioactivity level of soils and sediments due to the usage of fertilizers, particularly phosphate fertilizers, in agricultural lands of the Büyük Menderes River Basin, Western Turkey, have been determined. A total of 40 soil and sediment samples were collected along the Büyük Menderes River Basin and analyzed for 238U, 232Th, and 40K radioisotopes using a high-purity germanium detector. The activity concentrations of 238U, 232Th, and 40K in soils are in the ranges of 32 ± 4–93 ± 13, 11 ± 2–71 ± 9, and 353 ± 14–958 ± 23 Bq kg−1, and in sediments they are between 22 ± 6 and 72 ± 10, 7.3 ± 0.6 and 50 ± 5, and 310 ± 16 and 633 ± 25, respectively. In addition, to determine the hazard from natural radioactivity, the external terrestrial gamma dose rate in air (nGy h−1) and annual effective dose rate (mSv y−1) were calculated and compared with internationally recommended values. In soil samples, the average external terrestrial gamma dose rate in air was found to be 80.2 nGy h−1 and the average annual effective dose is 0.1 mSv.

Measurement of radioactivity in an elevated radiation background area of Western Ghats

As part of monitoring the exposure of the general public to natural radioactivity, the activity concentration of naturally occurring radionuclides in soil samples in an elevated radiation background area of Western Ghats was determined using gamma-ray spectrometry. Average values of the activity concentration of radionuclides, outdoor terrestrial gamma dose rate, annual effective dose equivalent and radiation hazard indices from soil activity were estimated. The activity concentrations of 232Th and average outdoor terrestrial gamma dose rate were found to be higher than the world average, possibly affecting the Western Ghats environment in general. Therefore, radiological risks to the general population from ionizing radiation from the naturally occurring radionuclides in the soil are considered to be significant. How- ever, other radiological hazard indices were found to be within permissible limits.

Dose rates and seasonal variations of 238U, 232Th, 226Ra 40K and 137Cs radionuclides in soils along Thrace, Turkey

Concentrations of 238U, 232Th, 226Ra, 40K and 137Cs are measured in collected soil samples from various locations in the Thrace region of Turkey. The activity concentrations range from 12.82 to 101.75 Bq kg−1 d.w. (dry weight) for 238U, from 5.16 to 73.34 Bq kg−1 d.w. for 232Th, from 185.54 to 5399 Bq kg−1 d.w. for 40K and from 11.42 to 90.73 Bq kg−1 d.w. for 226Ra. In addition to naturally occurring radionuclides, 137Cs activity concentration is determined between 3.05 and 46.78 Bq kg−1 d.w. for soil samples. Determination of the radiological hazard is achieved through calculations of the external terrestrial gamma dose rate in air (nGy h−1) and annual effective dose rate (mSv year−1) and the results are compared with the similar works in different countries.