Natural Radionuclides In Soil Research Articles

Baseline and Quality Reference Values for Natural Radionuclides in Soils of Rio de Janeiro State, Brazil

ABSTRACT A first large-scale systematic survey of natural radioactivity contents of soils of the state of Rio de Janeiro is presented, focused on the establishment of Quality Reference Values (QRVs). Undisturbed soil samples were collected from 243 areas and analyzed by gamma spectrometry. The activity contents varied largely, ranging from 12.2 to 1,029 Bq kg−1 for 40K (geometric mean of 111.1 Bq kg−1), from 3.5 to 99.8 Bq kg−1 for 226Ra (geometric mean of 29.7 Bq kg−1), and from 5.4 [...]

Research on the Content of Natural Radionuclides in Soils Damaged by Natural and Anthropogenic Processes

Research on the Content of Natural Radionuclides in Soils Damaged by Natural and Anthropogenic Processes

A national survey of natural radionuclides in soils and terrestrial radiation exposure in Iran

In the past, some efforts have been made for measuring natural radioactivity and evaluating public exposure to natural radiation in certain areas of Iran especially in well-known High Level Natural Radiation Areas (HLNRA) in Ramsar and Mahallat. However, the information on radionuclide concentrations, and, consequently, terrestrial radiation exposure for many other areas are not available. There was therefore a need for a systematic and nation-wide survey. For this purpose, 979 soil samples from 31 provinces were collected. The activity concentrations of 40K, 226Ra and 232Th were measured by HPGe detector. The average activity concentrations for Iran were found to be 457.7 Bq/kg for 40K, 24.3 Bq/kg for 226Ra and 25.8 Bq/kg for 232Th. Results were compared with previous regional or provincial surveys. The population-weighted average outdoor and indoor annual effective dose due to external exposure to terrestrial sources of radiation are 0.06 mSv and 0.33 mSv, respectively. It was shown that there is a significant correlation between the activity concentrations of 232Th and 40K in soil. In addition, the results of chi square tests show normal and lognormal distributions cannot be considered for the frequency distributions of activity concentration of 232Th and 226 Ra while 40K has a normal distribution.

Artificial and natural radionuclides in soils of the southern and middle taiga zones of Komi Republic

Specific activities of artificial (137Cs, 90Sr) and natural (40К, 232Th, 226Ra) radionuclides in background soils of southern and middle taiga of Komi Republic have been estimated with consideration for the landscape-geochemical features of the territory. It has been shown that their accumulation and migration in soils are determined by the following factors: position in relief, texture, and organic matter content. No anomalous zones with increased contents of radionuclides in soils have been revealed.

Determination of Concentrations of Natural Radionuclides in Soils and Water in Non-cultivated Sites in Seberang Perai, Malaysia

Determination of Concentrations of Natural Radionuclides in Soils and Water in Non-cultivated Sites in Seberang Perai, Malaysia

Naturally occurring radionuclide transfer from soil to vegetables in some farmlands in Ghana and statistical analysis

Distribution studies of natural radionuclides in soil, statistical analysis of activity concentrations, and transfer factors (TFs) from soil to the vegetables grown in some selected farming communities within the Greater Accra Region in Ghana were carried out. The measurements were carried out through a gamma-ray spectrometry. The mean activity concentrations of 226Ra, 228Ra, and 40K in the fertilized soils were 20.0 ± 3.9 Bq/kg, 39.0 ± 7.0 Bq/kg, and 143.6 ± 23.3 Bq/kg, respectively. For the nonfertilized soils, mean activity concentrations were found to be 12.07 ± 2.55 Bq/kg for 226Ra, 27.1 ± 6.3 Bq/kg for 228Ra, and 87.8 ± 18.5 Bq/kg for 40K. These results were compared with reported ranges in the literature from other location in the world. The TF for 226Ra, 228Ra, and 40K from fertilized soil to vegetables was evaluated. 226Ra TF values from fertilized soil to vegetables were found to be higher in lettuce in Farm 6. The highest TF for 40K and 228Ra was found in cauliflower in Farm 4. 40K TF was higher than those values reported in other studies. The activity concentration in fertilized and unfertilized soil exhibited slightly positively skewed, negatively skewed, leptokurtic, and platykurtic distribution in terms of skewness and kurtosis. The activity concentration of natural radionuclides in fertilized and unfertilized soil is statistically insignificant at 5% level of significance using independent t-test. Pearson's correlation coefficient exhibited a negative correlation between 226Ra and 228Ra in fertilized soil and 226Ra and 228Ra in vegetables but was statistically insignificant while 40K in fertilized soil exhibited a positive correlation with 40K in vegetables and was statistically significant at 5% level of significance with a coefficient of determination of 1%, 61%, and 10% for 226Ra, 40K, and 228Ra, respectively.

Modelling seasonal variations of natural radioactivity in soils: A case study in southern Italy

The activity of natural radionuclides in soil has become an environmental concern for local public and national authorities because of the harmful effects of radiation exposure on human health. In this context, modelling and mapping the activity of natural radionuclides in soil is an important research topic. The study was aimed to model, in a spatial sense, the soil radioactivity in an urban and peri-urban soils area in southern Italy to analyse the seasonal influence on soil radioactivity. Measures of gamma radiation naturally emitted through the decay of radioactive isotopes (potassium, uranium and thorium) were analysed using a geostatistical approach to map the spatial distribution of soil radioactivity. The activity of three radionuclides was measured at 181 locations using a high-resolution ?-ray spectrometry. To take into account the influence of season, the measurements were carried out in summer and in winter. Activity data were analysed by using a geostatistical approach and zones of relatively high or low radioactivity were delineated. Among the main processes which influence natural radioactivity such as geology, geochemical, pedological, and ecological processes, results of this study showed a prominent control of radio-emission measurements by seasonal changes. Low natural radioactivity levels were measured in December associated with winter weather and moist soil conditions (due to high rainfall and low temperature), and higher activity values in July, when the soil was dry and no precipitations occurred.

Correlation analysis of the natural radionuclides in soil and indoor radon in Vojvodina, Province of Serbia

The most dominant source of indoor radon is the underlying soil, so the enhanced levels of radon are usually expected in mountain regions and geology units with high radium and uranium content in surface soils. Laboratory for radioactivity and dose measurement, Faculty of Sciences, University of Novi Sad has rich databases of natural radionuclides concentrations in Vojvodina soil and also of indoor radon concentrations for the region of Vojvodina, Northern Province of Serbia. In this paper we present the results of correlative and multivariate analysis of these results and soil characteristics in order to estimate the geogenic radon potential. The correlative and multivariate analysis were done using Toolkit for Multivariate Analysis software package TMVA package, within ROOT analysis framework, which uses several comparable multivariate methods for our analysis. The evaluation ranking results based on the best signal efficiency and purity, show that the Boosted Decision Trees (BDT) and Multi Layer Preceptor (MLP), based on Artificial Neural Network (ANN), are multivariate methods which give the best results in the analysis. The BDTG multivariate method shows that variables with the highest importance are radio-nuclides activity on 30 cm depth. Moreover, the multivariate regression methods give a good approximation of indoor radon activity using full set of input variables. On several locations in the city of Novi Sad the results of indoor radon concentrations, radon emanation from soil, gamma spectrometry measurements of underlying soil and geology characteristics of soil were analyzed in detail in order to verify previously obtained correlations for Vojvodina soil.

Accuracy associated with the activity determination by in situ gamma spectrometry of naturally occurring radionuclides in soils

In situ gamma spectrometry (ISGS) is a technique mainly focused on the determination of man-made radionuclides deposited on soils. It is widely used for the radioactive characterization of soils in which there has been an incorporation of such radionuclides, especially 137Cs. Its use for the activity determination of naturally occurring radionuclides in soils has been more limited, and the accuracy associated with those measurements has yet to be treated extensively. There are numerous factors affecting the accuracy of the activity determination of naturally occurring radionuclides, such as the assumed soil geometry, the soil’s geological and mineral composition, its moisture content, etc. The present work studies the accuracy associated with the ISGS determination of the activity concentrations of natural radionuclides in soils using a portable HPGe detector. For 40K and 232Th activity determinations, the uncertainties associated with ISGS are generally of the order of 15%. However, 226Ra activity determined from its daughters 214Pb and 214Bi can be significantly overestimated when there is a major presence of 222Rn in the air around the detector. Finally, absorbed dose rate in air values were calculated from the naturally occurring radionuclide concentration in soils. The results showed good correspondence between the values obtained from ISGS and those obtained from laboratory determinations with the same soils.

Radiological hazard assessment of natural radionuclides in soils of some oil-producing areas in Nigeria

ABSTRACTThe activity concentrations of 226Ra, 232Th, and 40K were measured in soil core samples collected from eight locations with untapped crude oil deposits and two oil fields where crude oil exploration is ongoing in Nigeria. Measurement was carried out using a high-purity germanium (HPGe) detector. The radiological hazard to humans due to the radiation emitted from natural radionuclides in soils collected from the areas studied was assessed. In areas with untapped crude oil deposits, the average values of the absorbed dose rate (D), annual effective dose equivalent (AEDE), radium equivalent activity (Raeq), annual gonadal dose equivalent (AGED), external hazard index (Hex), internal hazard index (Hin), representative gamma index (Iγ), and excess lifetime cancer risk (ELCR) were 11.40 nGy h−1, 13.98 µSv y−1, 23.39 Bq kg−1, 82.41 mSv y−1, 0.063, 0.076, 0.183, and 0.049 respectively. In areas where crude oil exploration is ongoing, the average values of D, AEDE, Raeq, AGED, Hex, Hin, Iγ, and ELCR were 29.42 nGy h−1, 59.53 µSv y−1, 59.60 Bq kg−1, 206.69 mSv y−1, 0.162, 0.203, 0.455, and 0.209, respectively for workers who spend up to 8 hours per day at the oil fields. For workers who spend 10 hours per day at the oil fields, the average values of the AEDE and ECLR were 75.76 µSv y−1 and 0.266, respectively. Although all the calculated radiation hazard indices are lower than the permissible limits set by ICRP, the values are higher in areas where crude oil exploration is ongoing than areas with untapped crude oil deposits. This shows that oil and gas exploration activities have impacted negatively on the radiological status of the environment of the study area.

Measurement of gross alpha activity and statistical analysis of beach sediments along southern coastal region of TamilNadu

Radioactivity is a part of our environment. Natural radionuclides in soil generate a significant component of the background radiation exposure to the population. Radiation becomes a concern when these particles and energy come in contact with molecules inside the human body. This paper evaluates the radioactivity concentration of beach sand samples collected from the south east region of Tamilnadu. 20 beach sand samples are collected from the different locations of Tamilnadu. A survey of the gross alpha activity has been done using alpha scintillation counter. The gross alpha activity in the sand samples near the sea are found to be maximum (3679.6 Bq/kg) in Ko1 of sieve size 0.250 mm and minimum (162.3 Bq/kg) in Aa1 and Ma1 of sieve size 0.025mm respectively. Also, the results showed the gross alpha activity in the beach sand samples 150 m away from the sea is maximum (1774.1 Bq/kg) in Pml5 and minimum (107.5 Bq/kg) in Pe5 respectively. Statistical analysis has also been carried out to find the significant differences in the samples.

Effects of source rocks, soil features and climate on natural gamma radioactivity in the Crati valley (Calabria, Southern Italy)

The study, which represents an innovative scientific strategy to approach the study of natural radioactivity in terms of spatial and temporal variability, was aimed to characterize the background levels of natural radionuclides in soil and rock in the urban and peri-urban soil of a southern Italy area; to quantify their variations due to radionuclide bearing minerals and soil properties, taking into account nature and extent of seasonality influence. Its main novelty is taking into account the effect of climate in controlling natural gamma radioactivity as well as analysing soil radioactivity in terms of soil properties and pedogenetic processes.In different bedrocks and soils, activities of natural radionuclides (238U, 232Th 4 K) and total radioactivity were measured at 181 locations by means of scintillation γ-ray spectrometry. In addition, selected rocks samples were collected and analysed, using a Scanning Electron Microscope (SEM) equipped with an Energy Dispersive Spectrometer (EDS) and an X-Ray Powder Diffraction (XRPD), to assess the main sources of radionuclides. The natural-gamma background is intimately related to differing petrologic features of crystalline source rocks and to peculiar pedogenetic features and processes. The radioactivity survey was conducted during two different seasons with marked changes in the main climatic characteristics, namely dry summer and moist winter, to evaluate possible effects of seasonal climatic variations and soil properties on radioactivity measurements. Seasonal variations of radionuclides activities show their peak values in summer. The activities of 238U, 232Th and 4 K exhibit a positive correlation with the air temperature and are negatively correlated with precipitations.

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.

Natural radioactivity levels of great soil groups in Seferihisar Geothermal Region, Turkey

In this study, measurement of natural radioactivity and analyses of physical properties of soil were carried on great soil groups around the Seferihisar Geothermal Region. The radioactivity levels in soils were analyzed using scintillation gamma spectroscopy. The activity concentrations for 226Ra, 232Th, and 40K range from 7.1 to 32.0 Bq kg−1, 15.2 to 35.9 Bq kg−1 and 223.1 to 802.2 Bq kg−1, respectively. Obtained data was compared with average values given by UNSCEAR and the other studies. The radium equivalent activity (Raeq) in soil samples ranges from 42.2 to 144.7 Bq kg−1 which are lower than the suggested maximal admissible value of 370 Bq kg−1 recommended by OECD. In addition, the value of external exposure dose has been determined from the content of natural radionuclides in soil. The absorbed dose rates change between 20.6 and 70.9 nGy h−1 with a mean value of 46.7 nGy h−1 which is lower than the global average value of 55 nGy h−1. The annual effective dose rates varied from 25.2 to 87.0 μSv year−1 with an average value of 57.3 μSv year−1. Obviously, all the calculated values were lower than this value, and therefore the environment of Tuzla Fault can be regarded as an area with normal natural background radiation.

Natural radionuclides in soil near a coal-fired power plant in the high background radiation area, South China.

In this study, soil samples around Mawan coal-fired power plant (CFPP) in Shenzhen, a high background radiation area in South China, were analyzed for natural radionuclides. The activity concentration of (226)Ra, (232)Th, and (40)K in soils around Mawan CFPP ranged from approximately 72 to 358 Bq kg(-1) (averaged 204 Bq kg(-1)), 118 to 432 Bq kg(-1) (averaged 265 Bq kg(-1)), and 101 to 2168 Bq kg(-1) (averaged 1269 Bq kg(-1)), respectively, being found to be significantly higher than the world range values. The levels of these radionuclides in soil largely decreased with increasing distance from the CFPP, indicating a technologically enhanced natural radiation near the CFPP. The Raeq values for the soil samples around Mawan CFPP ranged from 346 to 878 Bq kg(-1), most of which exceeded the allowed maximum Raeq value of 370 Bq kg(-1). The operating of CFPP has increased the total radioactive dose received for the nearby population.

A Comparison Study of Soil Samples from Sinai Province in Egypt by Using X-Ray Diffraction and Gamma-Ray Analysis

Ten soil samples from Jabal Al Qur, Wadi Baba, and Wadi Sieh in Sinai, Egypt, were analyzed by XRD spectroscopy. The XRD spectroscopy results indicate that the major, minor and trace constituents varied from one sample to another. Samples were also analyzed by HPGe gamma spectrometer to determine the activity concentration of U-238, Th-232 series and K-40. The concentrations for 238U ranged from 57.03 to 4220.41 Bq/kg with an average 1110.75 Bq/kg, for 232Th, ranged from 13.55 to130.46 Bq/kg with an average 71.85 Bq/Kg. The concentrations for 40K were in the range from 12.18 to 948.93 Bq/kg with an average value 457.09 Bq/kg. The average activity concentration values of 226Ra, 232Th, and 40K, in all the collected samples were higher than the world average. The radium equivalent (Req), absorbed dose rate (DR), the effective dose rate (Deff), and hazard indices resulted due to the natural radionuclides in soil are also calculated. The Results show that the study area is not safe for human and environments.

Natural Radioactivity of Topsoil in Two Granite Areas of Guangzhou, South China

The natural radionuclide (238U, 226Ra, 232Th and 40K) concentrations in 152 soil samples were determined from two major granite areas in Guangzhou, using high resolution γ-ray spectroscopic system based on the characteristic spectral peaks. The mean activity values for 238U, 226Ra, 232Th and 40K were found to be 156.6±98.8, 160.9±96.5, 184.8±101.5 and 832.5±493.1 Bq kg–1 dry mass, respectively. The absorbed dose rate (D) calculated from activity concentration of 226Ra, 232Th and 40K ranged from 53.2 to 497.1 nGy h–1 with a mean of 220.7 nGy h–1. The Radium equivalent activity (Raeq), the outdoor annual effective dose and the external hazard index (Ir), which resulted from the natural radionuclides in soil, were also calculated and found to vary from 119.7 to 1117.2 Bq kg–1, from 0.07 to 0.61 mSv and from 0.33 to 3.07, respectively. The radium equivalent activities and the external hazard index in all the soil samples were same as 64.5% higher than the limit of 370 Bq kg–1 and 1.0, respectively. The outdoor annual effective dose was higher than the worldwide mean value of 0.07 mSv.

An Analysis for Distribution of Natural Radionuclides in Soil, Sand and Sediment of Potenga Sea Beach Area of Chittagong, Bangladesh

A HPGe (High Purity Germanium) detector based, low background gamma-ray counting system was used for activity measurement in soil, sand and sediment samples collected from Potenga sea beach area of Chittagong, Bangladesh. The specific radioactivities of Radium (226Ra), Thorium (232Th) and Potassium (40K) were measured in the above samples. The investigation reflects the lower deposition of minerals exist in the collected samples. From the measured specific radioactivities of the above three natural radionuclides, the radium equivalent activity (Raeq), the external hazard index (Hex), the external gamma absorbed dose rate and the annual effective dose were calculated. The obtained mean values of gamma absorbed dose rate in soil and sand samples and annual effective dose in soil, sand and sediment samples were found higher than the worldwide average as reported by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR, 2000). The Raeq values were in the range of 47.86 to 293.76 Bq·kg-1 and the Hex varied from 0.13 - 0.81, which indicated that the study area was radiologically safe for human being.

Baseline Assessment of dose due to Natural Radionuclides in soils of coastal regions of Kanyakumari district in Tamil Nadu, India

The natural radioactivity due to uranium, Thorium and potassium in soil contributes to the radiation dose received by human beings significantly. Gamma ray spectrometric measurements carried out for the natural radioactivity levels due to 226 Ra, 232 Th and 40 K in beach sand samples around the coast of Kanyakumari district were analyzed. For assessing the environmental radiological impact to public it is essential to evaluate the activity levels of these radionuclides. The absorbed dose rate due to natural radionuclides was also calculated and the results are reported in this paper. The total annual effective dose of the study area founds to vary between 0.94 mSv to 2.23 mSv. This study provides a baseline data of radioactivity background levels in the coastal regions of Kanyakumari district from Muttom to Midalam and will be useful to assess any changes in the radioactive background levels.

Effect of Geology on Soil Radioactivity and Risks to Humans Based on Data from Several Towns in Nigeria

Gamma ray spectrometric technique has been used to determine activity concentrations of some primordial radionuclides in the naturally occurring uranium, actinium and thorium series and of non-series 40K in soil samples collected from five major towns in Oyo State, Southwestern Nigeria. Activity concentration determination was done using a high purity germanium (HPGe) detector. It ranged from 85.83 ± 4.04 Bq kg−1 to 1,850.60 ± 36.83 Bq kg−1 for 40K; 5.23 ± 0.34 Bq kg−1 to 198.31 ± 4.10 Bq kg−1 for 208Tl (indicator for 232Th) and 7.82 ± 0.42 Bq kg−1 to 64.65 ± 2.00 Bq kg−1 for 214Bi (indicator for 238U). The outdoor absorbed dose rate in air due to each of the primordial radionuclides was calculated from the mean values of the activity concentration in each sample. Values ranged from 3.60 ± 0.17 nGy h−1 to 77.73 ± 1.55 nGy h−1 for 40K, 3.48 ± 0.23 nGy h−1 to 132.07 ± 2.73 nGy h−1 for 208Tl and 3.35 ± 0.21 nGy h−1 to 27.73 ± 0.86 nGy h−1 for 214Bi. The absorbed dose rate in air was the highest for rocky areas, while the lowest value came from non-rocky, non-industrialized areas. The estimated annual outdoor effective dose equivalents for the two rocky areas were 385.76 μSv y−1 and 221.28 μSv y−1. The estimated annual outdoor effective dose equivalents for the two industrialized areas were 64.05 μSv y−1 and 47.65 μSv y−1. The value for non-rocky, non-industrialized areas was 19.19 μSv y−1. The average value for the study area was 147.59 μSv y−1. The estimated collective effective dose equivalent for the area was 9.77 × 102 man-Sv y−1. The expected number of people in the study area at risk of incurring cancer per year as a result of radioactivity in the soil was estimated to be 11; this value represents approximately 7% of the estimated 160 people for 18 Nigerian cities, approximately 69% of 16 people estimated for oil producing areas of Nigeria and less than the United States Environmental Protection Agency regulatory limit of 1 cancer case to 10,000 people. Also, this result shows that local variability of natural radionuclides in soil depends on local geology of the area. The incidence number was 2.4 people per million.