Natural radioactivity in the newly discovered high background radiation area on the eastern coast of Orissa, India

Review and statistical analysis of activity values reported for coastal sands worldwide

The activity of natural radionuclides is unevenly distributed across the Earth's crust, with certain areas exhibiting significantly higher levels than others, known as High Background Radiation Areas (HBRAs). This study presents a statistical analysis of reported activity values for coastal sands globally. Through this statistical analysis, costal sands were classified into four categories based on their activity levels, providing a standardized framework to compare the natural radioactivity of these sands. This classification is a valuable tool for identifying populations exposed to different radiation levels, which is essential for the study of stochastic effects. The study proposes thresholds to define HBRAs as regions with activity values exceeding 203 Bq/kg for 238U, 517 Bq/kg for 232Th, or 960 Bq/kg for 40K. Regions with lower values are classified as NonHBRAs. Further subdivision of these categories resulted in four distinct regions: NonHBRA-, NonHBRA+, HBRA-, and HBRA+. The activity values for these subdivisions are 92 Bq/kg and 2,903 Bq/kg for 238U, 94 Bq/kg and 7,230 Bq/kg for 232Th, and 901 Bq/kg and 2,298 Bq/kg for 40K. By calculating the external dose rates from the reported activity data, a threshold of 357 nGy/h was identified as the dose boundary separating NonHBRAs from HBRAs. The values for the subdivisions resulted 101 nGy/h and 3,867 nGy/h. The study also explores the content of these natural radionuclides in relation to their bearing minerals and discusses correlations between the reported activity values and the characteristics of the sands. Additionally, the activity of the anthropogenic radionuclide 137Cs (reported values ranging from the detection limit to 63 Bq/kg) is examined.

Ambient gamma radiation level around Kaveri river basin, Karnataka state, India

Studies on ambient gamma radiation in indoor and outdoor environment and their effect on human health have created interest among the researchers across the world. The present study represents the results of indoor and outdoor ambient gamma dose rates around the Kaveri river basin from Talakaveri (Madikeri district) to Mekedatu (Ramanagara district) by using portable Environmental Radiation Dosemeter. The annual effective dose in the present study area varies between 0.14 mSv.y-1 and 0.58 mSv.y-1 with an average value of 0.30 mSv.y-1 for indoor radiation. The outdoor annual effective dose ranged between 0.01 mSv.y-1 and 0.14 mSv.y-1 with an average value of 0.06 mSv.y-1. The total annual effective dose varies from 0.17 to 0.72 mSv.y-1 with an average value of 0.36 mSv.y-1. The calculated values of indoor and outdoor annual effective dose in the study area (are found to be lower than the world average values (1 mSv.y-1 and 0.48 mSv.y-1).

Assessment of natural radioactivity levels and hazard indicators in Tarakeshwor Municipality, Nepal through in-situ technique and multivariate analysis

The evaluation of primordial radionuclide concentrations in rapidly urbanized and concrete-laden areas through the importation of construction materials from various regions of Nepal is both important and essential. This study utilized a portable gamma-ray spectrometer (PGIS 2) to analyze the distribution of three natural radionuclides: uranium (238U), thorium (232Th), and potassium (40K) in Tarakeshwor Municipality, Kathmandu, Nepal. The measured dose rates ranged from 70.22 nSv hr-1 to 163.66 nSv hr-1, with an average of 124.65±20.29 nSv hr-1, surpassing the global average of 59 nSv hr-1. The activity concentrations of 40K, 238U, and 232Th exceeded global averages, indicating relatively higher natural radioactivity concentrations in the region. Specifically, the average values for 40K, 238U, and 232Th were 935.26±172.30 Bq kg-1, 80.47±15.53 Bq kg-1, and 80.44±18.58 Bq kg-1, respectively. The calculated radium equivalent (Ra eq ) ranged from 132.26 to 351.22 Bq kg-1, and the annual gonadal equivalent dose (A G E D ) varied from 372.61 to 1028.81 μSv yr-1. The annual effective dose rates for indoor and outdoor environments were 0.54±0.09 mSv yr-1 and 0.15±0.03 mSv yr-1, respectively, both exceeding the global average. The representative level index (RLI) within the study area averaged 1.96±0.32, indicating an elevated radiation risk. The excess lifetime cancer risk (E L C R ) values for outdoor and indoor environments were 0.52× 10 - 3 ±0.09 × 10 - 3 and 1.87 × 10 - 3 ±0.31× 10 - 3 , respectively, surpassing the world average. Additionally, external hazard indices (H ex ) ranged from 0.36 to 0.59, while internal hazard indices (H in ) ranged from 0.38 to 1.20, both indicating values higher than UNSCEAR recommendations. These findings underscore the necessity for further experimental analysis employing ex-situ equipment. The data generated in this study can provide a valuable baseline for future assessments and interventions in radiation risk management guidelines within the country.

Estimation of radiation dose due to thoron and progeny inhalation in high background natural radiation area of Odisha, India

Results of the preliminary measurements of indoor radon, thoron and progeny concentrations showed very high values of thoron concentrations in the eastern coastal region of Odisha, India. Therefore, measurements of thoron and its progeny concentrations were extended to a larger number of houses in this area for the assessment of the radiation dose received by the public. The measured values of thoron concentrations were used for the calculation of annual effective doses. The estimated values of the annual effective dose due to thoron exposure were observed in the range of 0.2-14.7 mSv. The estimated radiation doses responsible for thoron exposure were observed considerably high in the region. The results obtained are compared with those obtained in other studies performed so far in the study area and a review of different studies involving different measurement techniques is presented in the paper. The results of this study support the preliminary studies showing high values of thoron levels in the study area.

Natural radioactivity and radiological hazard analysis of construction stones from various quarries in Machakos County-Kenya

The radioactivity levels of rocks sampled from the quarries of Kyasioni, Mavoloni and Kathaana located in the lower Eastern County of Machakos in Kenya were determined. Forty-two samples were collected using stratified random sampling and analysed using NaI(TI) detector with a specially designed lead shield. The parametric values of activity concentration, absorbed dose, annual dose rate and hazard indices were estimated using activity-dose relations suggested in UNSCEAR and ICRP reports. The mean activity concentration for the entire work for 238U (226Ra), 232Th and 40K were 68.33 ± 3.11, 101.10 ± 1.83 and 1084.02 ± 30.28 Bq/kg, respectively. Kyasioni quarry presented the highest activity concentration of 74.75 ± 3.15, 118.48 ± 1.91 and 1120.35 ± 30.07 Bq/kg for 226Ra, 232Th and 40K, respectively. The average annual effective dose was estimated as 0.58 ± 0.01, 0.47 ± 0.01 and 0.52 ± 0.01 mSv/y for Kyasioni, Kathaana and Mavoloni quarries, respectively. Other radiological parameters estimated from the corresponding activities were within the recommended limits hence guaranteeing safety to the users.

The status of natural radioactivity in Nigerian environments

Proper documentation of baseline radiation data of different environments is an important step toward adequate environmental monitoring, and it provides quick means to quantitatively check and determine possible radionuclide contamination by anthropogenic sources. Besides, such documentation is useful for decision making processes, assessment of dose rates to the public, epidemiological studies, and environmental regulations. This review summarizes the results of studies conducted on radioactivity in Nigerian environments. For most soil samples, the levels of radioactivity are well within the world averages of 33, 45, and 420 Bq kg^-1 for ²²⁶Ra, ²³²Th and ⁴⁰K, respectively. Other soil samples from regions such as Abeokuta in the southwest, and Jos in the northcentral have been described as high background radiation areas with radioactivity values comparable with those obtained from known high background radiation areas such as the Odisha (formerly Orissa) coast in India (with values reported as 350, 2,825, and 180 Bq kg^-1 for ²³⁸U/²²⁶Ra, ²³²Th, and ⁴⁰K, respectively). In some parts of Nigeria, surface and underground water sources used for drinking and other purposes also present elevated levels of ²²⁶Ra above the world range of 0.01 to 0.1 Bq l^-1 and the tolerable levels recommended by the World Health Organization and U.S. Environmental Protection Agency. Corresponding radiation doses due to measured radioactivities from different environments were estimated and compared with those reported in similar studies around the world. More so, the human and environmental health hazards that might be associated with the reported radioactivity in different environmental settings are discussed. The present report is expected to support authorities in developing appropriate regulations to protect the public from radiation exposure arising from environmental radioactivity. The report also examines other areas of consideration for future studies to ensure adequate radiation monitoring in Nigeria.

Investigations on baseline levels for natural radioactivity in soils, rocks, and lakes of Larsemann Hills in East Antarctica

A comprehensive measurement of concentrations of the natural radionuclides ²³⁸U, ²³²Th and ⁴⁰K, and ²²⁶Ra in the soil and rocks along with natural uranium and tritium activity levels in lake water were carried out during the Indian expedition to Antarctica. The samples were collected from the Larsemann Hills region in Antarctica (latitude 69°20' S to 69°25'S, longitude 76°6' E to 76°23'E). The data on the natural radioactivity for this region is limited. The study was carried out to establish baseline levels of radioactivity in different terrestrial matrices of this region such as soil, rocks, and lake water. A radiation survey mapping for terrestrial radioactivity was conducted in the region before collection of soil and rock samples. The soil and rock samples were analyzed for natural radioactivity concentrations using high-resolution gamma spectroscopy system. The major contributor to elevated gamma radiation background is attributed to the higher concentration of ²³²Th and ⁴⁰K radionuclides in both soil and rocks. Terrestrial components of gamma dose rate due to natural radioactivity have been estimated from the measured radioactivity concentrations and dose conversion coefficients. Several "hotspots" and high background areas in the region have been identified having significantly higher concentration of ²³²Th and ⁴⁰K. Rocks in Larsemann Hills region showed high reserve of thorium mineralization in monazites and ⁴⁰K in K-feldspar. The concentrations of ²³²Th in soil are found to be in the range of 106-603 Bq/kg, whereas in rock it is in the range of 8-4514 Bq/kg. Natural radioactivity U (nat) and ³H contents in the lake water samples in Larsemann Hills region were estimated as 0.4 and 1.3 Bq/L and are well within the prescribed limit of radioactivity in drinking water as recommended by World Health Organization.

ASSESSMENT OF THE OUTDOOR GAMMA RADIATION LEVELS IN ALGIERS PROVINCE, ALGERIA

The outdoor gamma radiation dose rates due to natural radioactivity and due to the artificial radionuclides released from the Chernobyl and Fukushima accidents and Algeciras incident were assessed in the Algiers province (capital of Algeria). Furthermore, the dose rates induced by the cosmic rays were analytically calculated in the province concerned. The recorded dose rates due to terrestrial outdoor gamma radiation were found to range from 14.3 ± 0.7 to 114.3 ± 5.7 nGy h -1, those due to cosmic rays ranged from 32.021 ± 0.013 to 34.029 ± 0.367 nGy h -1, while the contribution of the dose rate due to external exposure induced by 137Cs deposits, from major accidents, was estimated to be less than 0.3 nGy h-1. The spatial distributions of terrestrial and cosmic rays dose rates were mapped using QGIS software. The obtained radiological baseline maps can be used as reference information to assess any changes in the radiation exposure levels having an impact on the population health.

DETERMINATION OF RA-226, TH-232, K-40 AND CS-137 ACTIVITIES IN SOILS AND BEACH SANDS AND RELATED EXTERNAL GAMMA DOSES IN ARIKLI MINERALIZATION AREA (AYVACIK/TURKEY)

Uranium mineralization areas may jeopardize public health and surrounding natural life. In the current study for radioactivity and geochemical analyses, 43 soil, 5 rock and 10 beach sand samples were collected in and around Arıklı (Ayvacık, Turkey) uranium mineralization area. Radioactivity levels in the soils (up to Ra-226: 629, Th-232: 240, K-40: 3669 Bq/kg) were found higher than the that of beach sands. Besides, radioactivity of the beach sand samples is found at normal levels (avg: Ra-226: 31, Th-232: 31, K-40: 542 Bq/kg) when compared to worldwide average soil. Dose values indicate that the region have ~three times higher average gamma radioactivity than the corresponding world average although measured gamma doses ranged up to 687 nGy/h. The high measured values are related to uranium mineralization, alteration zones, faults and Arıklı tuff.

A seasonal 222Rn mass-balance of Lake Burullus, Egypt: Indications for higher pore water exchange rates during the dry season

Radon mass balances in lakes can be used to trace transport processes along the sediment-water interface, such as groundwater discharge or pore water exchange. Understanding these transport processes is important, as they can affect the lake water budget, or biogeochemical cycles in lakes due to nutrient inputs. We present here a seasonal ²²²Rn mass balance of Lake Burullus (Northern Egypt), the second largest lake of Egypt. The Lake receives ²²²Rn from drainage water and the decay of ²²⁶Ra, and loses ²²²Rn via decay of ²²²Rn, atmospheric evasion and water discharge into the Mediterranean Sea. However, the mass balance reveals a significant surplus of ²²²Rn, which cannot be explained by the previously mentioned processes. The ²²²Rn surplus is especially high during the dry season, and might be explained by groundwater discharge and pore water exchange which transports ²²²Rn into the lake. Higher ²²²Rn fluxes into the lake during dry season might be explained by higher bioirrigation rates due to warmer temperatures, or higher groundwater discharge rates due to a higher hydraulic head on land caused by excessive irrigation in adjacent fields. Groundwater discharge and pore water exchange should be investigated in further detail in order to understand if they have effects on water budgets and biogeochemical cycles of Lake Burullus.

Significance of thoron measurements in indoor environment

Radon, ²²²Rn, is the major contributor to natural radiation in human environment. The exposure of high radon is known as one of the causative factors of lung cancer. Though thoron, ²²⁰Rn, has been a matter of study in atmospheric science, but it was often neglected compared to radon. It was considered that the amount of thoron in the environment is less than that of radon. However, recent studies show that thoron and its progeny sometime contribute significantly to the radiation dose in residential buildings. A review of methodologies, measurement protocols and concepts used in various thoron measurement surveys performed in India is presented in this paper. The results of measurements of thoron and its progeny, carried out in the Himalayan region and in the high background radiation area of the south-eastern coast of Odisha, India are also presented. The results obtained using various thoron measurements techniques and the resulting doses to the general public are discussed in details.

NATURAL RADIOACTIVITY MEASUREMENT AND DOSE ASSESSMENT OF BEACH PLACER SANDS IN THE COASTAL REGION OF TAMIL NADU (INDIA)

A preliminary study was carried out to determine the radioactivity concentration of 232Th, 226Ra and 40K in beach placer sands from 13 locations along the coast line of Tamil Nadu state, India. The ambient dose rates varied from 9 to 467 nGy h-1. The activity concentrations of radionuclide 232Th, 226Ra and 40K ranged from 5.2 to 683 Bq kg-1, 13 to 198 Bq kg-1 and 107 to 421 Bq kg-1, respectively. The annual effective dose rate ranges from 27 to 620 μSv y-1 and was higher at seven beaches in comparison to the UNSCEAR annual worldwide average value.

Geospatial analysis and assessment of 226Ra, 235U, 232Th, 137Cs, and 40K at Anzali wetland, north of Iran

Achieving better monitoring and radiation risk assessment is among the main issues in environmental studies. In this regard, natural radioactivity measurements in sediments can provide useful information about the environmental transport mechanism and about the sources of radionuclides. Anzali wetland, as the study area of this research, is located on the southwestern shore of the Caspian Sea with rapidly changing ecosystems. Because of its strategic location, increasing pollution levels, decreasing water table, and increasing sediment discharge from rivers, Anzali wetland has a unique significance in terms of studying its radioactivity from sediment and soil samples. The average ²²⁶Ra, ²³⁵U, ²³²Th, ¹³⁷Cs, and ⁴⁰K values for 33 sediment and soil samples were 24.66, 3.72, 31.94, 11.66, and 506.38 Bq kg^-1, respectively. Variography analyses revealed a spatial structure with minimum/maximum variance equal to 3/8 from 135°/45° azimuth direction. In addition, the fractal geometry indicates values higher than 3.7, 24.5, 30, 25, and 475 Bq kg^-1 as anomalous values for ²³⁵U, ²²⁶Ra, ²³²Th, ¹³⁷Cs, and ⁴⁰K using Kriging estimated data with a search radius of 5000 m, respectively. Compared with the average values published by UNSCEAR (2008) for earth's crust average and compared with the values for the southern areas of Iran (Oman Sea), the estimated average and anomalous data for a pollutant at Anzali wetland do not exceed the reference data. The higher values in the samples of this study could be related to specific environmental problems such as industrial wastewater from about 30 polluted factories transported by 10 major rivers. Agricultural wastes, such as herbicides, pesticides, and fertilizers from rice fields, and being a tourist attraction zone at sea beach are the other most possible pollution sources in the study area.

Mineral and magnetic parameters as proxies for natural radioactivity level in Vaigai river sediment: Horizontal and vertical approach

The present study is aimed to show that the mineral and magnetic parameters are proxies for radioactivity level of Vaigai river sediment. In order to show the usefulness of above said parameters as proxies for radioactivity level of the river, elaborate analyses along with radioactivity level need to be analyzed in horizontal (different locations) and vertical (upper, first, second and third feet) views of the river. The radioactivity analysis shows that average concentrations of ²³⁸U, ²³²Th and calculated absorbed dose rate are within the recommended safety level in all depth samples. Eleven minerals have been identified and characterized by FTIR, and are confirmed by XRD techniques. Based on the calculated results of extinction co-efficient, the amount of major minerals are decreased in the order of quartz > microcline feldspar > orthoclase feldspar > kaolinite in all depth samples. The presence of ordered crystalline quartz in all depth samples have been assessed by the calculated crystallinity index values. These observations are matched with XRD results. Magnetic susceptibility measurement was carried out in horizontal and vertical views which show the presence of dia, ferri, antiferri and ferrihydrate magnetic minerals in present sediments. Studied characteristics and their distributions are almost similar in all the depths. Multivariate statistical analyses include cluster analysis (CA), Factor analysis (FA) and Principal component analysis (PCA) are effective tool to show the above said parameters as proxy and the analyses are carried out. Relevant justification is also given for explaining the parameters as proxy. In the clay mineral, high adsorption of radionuclides and magnetic minerals occurs in lattice defects or onto crystal and grain boundaries due to the high cation exchange capacity. Since, the parameters such as content of clay, magnetic susceptibility and amount of kaolinite (clay) in all depth samples are strongly associated with radioactivity variables, one can say that above said parameters may be proxies for determining the level of radioactivity in Vaigai river sediment.

A REVIEW ON VARIATION OF NATURAL RADIOACTIVITY ALONG THE SOUTHEAST COAST OF TAMIL NADU FOR THE PAST 4 DECADES (1974-2016)

This review deals with natural radioactivity variation along the southeast coast of Tamil Nadu for the past four decades (1974-2016). About 40 research works have been conducted along the coast since 1974 in various environmental matrices using a variety of experimental methods. For these measurements researchers are adopted different experimental methods. The measured gamma dose rate ranged from 30 to 8700 nGy/h. The mean specific activity of 238U, 232Th and 40K was found to be 58.8 ± 28.7, 465.2 ± 147.3 and 311.2 ± 27.8 Bq/kg, respectively. The calculated annual exposure rate ranged from 0.29 to 12.8 mSv/y with the mean value of 3.7 mSv/y which is above the global average of 2.4 mSv/y as reported by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) (Report to General Assembly, Annex B Exposures of the public and workers from various sources of radiation. United Nations, New York (2008)). Plant food items recorded low 210Po activities as compared to seafood organisms. Grain size, season and place of sampling have a decisive bearing on coastal radioactivity. Therefore, it is concluded from the review data that there is an appreciable elevation in background radiation level in the coastal region. This review suggests that new radiological surveys using improved methodology that cover the entire coastal stretch are needed.

Hazardous parameters associated with natural radioactivity exposure from black sand

Black sand samples collected from Baltim beaches (Kafr El-Sheikh governorate) in Egypt on the Mediterranean Sea shore were analyzed radiometrically and evaluated using a nondestructive gamma ray spectroscopic techniques. The natural radionuclides of ²²⁶Ra, ²³²Th and ⁴⁰K in the black sand samples were identified and quantified. It is found that the activity concentrations for ²²⁶Ra, ²³²Th and ⁴⁰K in different eleven sites (S1S11) were found within the ranges of 28-322, 91-308 and 81-339 Bq/kg, respectively. Moreover, different radiological hazardous parameters (absorbed dose rate, annual effective dose equivalent, radium activity, annual gonadal dose equivalent and excess lifetime cancer risk) were calculated. The results show that these values are greater than the permissible values due to increasing the activity concentrations of the primordial radionuclides ²²⁶Ra, ²³²Th and ⁴⁰K. The dose rate for radiation emitted at 1 m from the surface of land was measured directly and the results shown that all sites emit radiation doses more than the international permissible value (57 nGy/h) especially at three sites which around 340 nGy/h. These values are important to establish baseline levels of this environmental radioactivity to detect any upcoming change for the local population and resorts people. The relatively high dose rate will be considered as a spa for the physical therapy such as treatment of some skin diseases and rheumatoid.

Radiological Investigation of High Background Radiation Areas

In this paper, we used the Hyper-Pure Germanium (HPGe) detector to measure 30 samples which are collected from north of Nile Delta near Rosetta beach in Egypt. The activity of primordial radionuclides, such as 238U, 235U, 232Th, and 40K was estimated. Concentrations ranged between 36.5-177.4, 50-397.5 and 56.1-168.9 Bq.kg-1 for 238U, 232Th and 40K respectively. Activity concentration of 235U and the variation in uranium isotopic ratio 235U/238U was calculated. External hazard indices (Hex) (or radium equivalent activity Raeq), activity concentration indices (I), alpha index (Iα), absorbed outdoor gamma dose rate (Dout), effective outdoor gamma dose rate (Eout) and Excess Lifetime Cancer Risk (ELCR) due to different samples are estimated. External hazard indices (Hex) are ranged between 0.32-2.04, radium equivalent activity (Raeq) are ranged between 118.67-753.91, the activity concentration indices (I) are 0.42-2.61, and alpha index (Iα) are 0.18-0.89. External hazard indices (Hex) in some samples more than unity then it exceeds the upper limit of exposure. Also, the radium equivalent activities (Raeq) are higher than the exemption limits (370 Bq.kg-1).

NATURAL RADIOACTIVITY LEVEL AND ELEMENTAL COMPOSITION OF SOIL SAMPLES FROM A HIGH BACKGROUND RADIATION AREA ON EASTERN COAST OF INDIA (ODISHA)

A comprehensive study was carried out to determine the radioactivity concentration of soil samples from different sites of a high background radiation area in the eastern coast of India, Odisha state. The dose rate measured in situ varied from 0.25 to 1.2 µSv h^-1 The gamma spectrometry measurements indicated Th series elements as the main contributors to the enhanced level of radiation and allowed the authors to find the mean level of the activity concentration (±SD) for ²²⁶Ra, ²²⁸Th and ⁴⁰K as 130±97, 1110±890 and 360±140 Bq kg^-1, respectively. Human exposure from radionuclides occurring outdoor was estimated based on the effective dose rate, which ranged from 0.14±0.02 to 2.15±0.26 mSv and was higher than the UNSCEAR annual worldwide average value 0.07 mSv. Additionally, X-ray fluorescence analysis provided information about the content of major elements in samples and indicated the significant amount of Ti (7.4±4.9 %) in soils.

Assessment of gamma radiation exposure of beach sands in highly touristic areas associated with plutonic rocks of the Atticocycladic zone (Greece)

This study aims to evaluate the activity concentrations of ²³⁸U, ²²⁶Ra, ²³²Th, ²²⁸Th and ⁴⁰K along beaches close to the plutonic rocks of the Atticocycladic zone that ranged from 15 to 628, 12-2292, 16-10,143, 14-9953 and 191-1192 Bq/kg respectively. A sample from island of Mykonos contained the highest ²³²Th content measured in sediments of Greece. The heavy magnetic fraction and the heavy non-magnetic fraction as well as the total heavy fraction, were correlated with the concentrations of the measured radionuclides in the bulk samples. The heavy fractions seem to control the activity concentrations of ²³⁸U and ²³²Th of all the samples, showing some local differences in the main ²³⁸U and ²³²Th mineral carrier. Similar correlations have been found between ²³⁸U, ²³²Th content and rare earth elements concentrations. The measured radionuclides in the beach sands were normalized to the respective values measured in the granitic rocks, which at least in most cases are their most probable parental rocks, so as to provide data upon their enrichment or depletion. Since the Greek beaches are among the most popular worldwide the annual effective dose equivalent received due to sand exposure has been estimated and found to vary between 0.002 and 0.379 mSv y^-1 for tourists and from 0.018 to 3.164 mSv y^-1 for local people working on the beach. The values corresponding to ordinary sand samples are orders of magnitude lower than the limit of 1 mSv y^-1, only in the case of heavy minerals-rich sands the dose could reach or exceed the recommended maximum limit.

Activity concentration and spatial distribution of radionuclides in marine sediments close to the estuary of Shatt al-Arab/Arvand Rud River, the Gulf

Tigris and Euphrates rivers both emerge in eastern Turkey and cross Syria and Iraq. They unite to Shatt al-Arab/Arvand Rud River and discharge in Arabic/Persian Gulf. The activity concentration of natural and anthropogenic radionuclides was measured during the August of 2011 in a number of surficial sediment samples collected from the seabed along an almost straight line beginning near the estuary mouth and extending seaward. The results exhibited low activity concentration levels and an almost homogeneous spatial distribution except locations where sediment of biogenic origin, poor in radionuclides, dilute their concentrations. Dose rates absorbed by reference marine biota were calculated by the ERICA Assessment Tool considering the contribution of 40 K. The results revealed a relatively low impact of 40 K mainly to species living in, on and close to the seabed. Also, statistical association of radionuclides with selected stable elements (Ca, Ba and Sr) did not indicate presence of by-products related with oil and gas exploitation and transportation activities. Moreover, a semi-empirical sedimentology model applied to reproduce seabed granulometric facies based entirely on radionuclides activity concentrations.

Evaluation of excess life time cancer risk due to natural radioactivity of the Lignite samples of the Nichahoma, lignite belt, North Kashmir, India

Naturally occurring radionuclides of the 226Ra, 232Th, and 40K present in the lignite samples was measured by using a low-background Pb-shielded gamma spectroscopic counting assembly utilizing NaI(Tl) detector for the measurement and to evaluation the radiation hazard indices and excess life time cancer risk. The average values of specific activity concentrations in the investigated lignite samples was found to be 45.36 Bq kg−1 for 226Ra, 21.42 Bq kg−1 for 232Th, 40.51 Bq kg−1 for 40K and 79.11 Bq kg−1 for Raeq respectively. The average value excess life time cancer risk was found to be relatively higher than the world average. Moreover, the correlation analysis shows the strong dependence of excess lifetime cancer risk on measured dose and the radium equivalent activity.

Inhalation exposures due to radon and thoron ((222)Rn and (220)Rn): Do they differ in high and normal background radiation areas in India?

In India, High Background Radiation Areas (HBRAs) due to enhanced levels of naturally occurring radionuclides in soil (thorium and, to a lesser extent, uranium), are located along some parts of the coastal tracts viz. the coastal belt of Kerala, Tamilnadu and Odisha. It is conjectured that these deposits will result in higher emissions of radon isotopes ((222)Rn and (220)Rn) and their daughter products as compared to Normal Background Radiation Areas (NBRAs). While the annual external dose rates contributed by gamma radiations in these areas are about 5-10 times higher, the extent of increase in the inhalation dose rates attributable to (222)Rn and (220)Rn and their decay products is not well quantified. Towards this, systematic indoor surveys were conducted wherein simultaneous measurements of time integrated (222)Rn and (220)Rn gas and their decay product concentrations was carried out in around 800 houses in the HBRAs of Kerala and Odisha to estimate the inhalation doses. All gas measurements were carried out using pin-hole cup dosimeters while the progeny measurements were with samplers and systems based on the Direct radon/thoron Progeny sensors (DRPS/DTPS). To corroborate these passive measurements of decay products concentrations, active sampling was also carried out in a few houses. The results of the surveys provide a strong evidence to conclude that the inhalation doses due to (222)Rn and (220)Rn gas and their decay products in these HBRAs are in the same range as observed in the NBRAs in India.

Assessments of radioactivity concentration of natural radionuclides and radiological hazard indices in sediment samples from the East coast of Tamilnadu, India with statistical approach

This paper reports on the distribution of three natural radionuclides (238)U, (232)Th and (40)K in coastal sediments from Pattipulam to Devanampattinam along the East coast of Tamilnadu to establish baseline data for future environmental monitoring. Sediment samples were collected by a Peterson grab samples from 10m water depth parallel to the shore line. Concentration of natural radionuclides were determined using a NaI(Tl) detector based γ-spectrometry. The mean activity concentration is ⩽2.21, 14.29 and 360.23Bqkg(-1) for (238)U, (232)Th and (40)K, respectively. The average activity of (232)Th, (238)U and (40)K is lower when compared to the world average value. Radiological hazard parameters were estimated based on the activity concentrations of (238)U, (232)Th and (40)K to find out any radiation hazard associated with the sediments. The radiological hazard parameters such as radium equivalent activity (Raeq), absorbed gamma dose rates in air (DR), the annual gonadal dose equivalent (AGDE), annual effective dose equivalent (AEDE), external hazard index (Hex) internal hazard index (Hin), activity utilization index (AUI) and excess lifetime cancer (ELCR) associated with the radionuclides were calculated and compared with internationally approved values and the recommended safety limits. Pearson correlation, principal component analysis (PCA) and hierarchical cluster analysis (HCA) have been applied in order to recognize and classify radiological parameters in sediments collected at 22 sites on East coast of Tamilnadu. The values of radiation hazard parameters were comparable to the world averages and below the recommended values. Therefore, coastal sediments do not to pose any significant radiological health risk to the people living in nearby areas along East coast of Tamilnadu. The data obtained in this study will serve as a baseline data in natural radionuclide concentration in sediments along the coastal East coast of Tamilnadu.

Determination of activity concentration of natural and artificial radionuclides in sand samples from mediterranean coast of Antalya in Turkey

In this paper, we attempt to determine the activity concentration of natural and artificial radionuclides in 37 sand samples from the Mediterranean coast of Antalya in Turkey by using a high purity Germanium (HpGe) detector. 238U, 232Th, 40K and 137Cs activity concentrations, absorbed dose rate, annual effective dose equivalent, radium equivalent activity, external and internal hazard index of sand samples are determined res-pectively. The average values are 13.43 ± 0.21 Bq/kg, 6.96 ± 0.06 Bq/kg and, 122.46 ± 18.58 Bq/kg, for 238U, 232Th and 40K respectively. Most of the activity concentration values are less than below minimum detection limit for 137Cs. The average values of the absorbed dose rate D (nGy/h), annual effective dose equivalent AEDE(μSv/y), radium equivalent activity Raeq (Bq/kg), external hazard index Hex and internal hazard index Hin are 15.52 nGy/h, 19.03 μSv/y, 32.81 Bq/kg, 0.09 and 0.12 respectively. It is observed that 238U, 232Th, 40K and 137Cs activity concentrations, absorbed dose rate, annual effective dose equivalent, radium equivalent activity are in the limit of the published values, external and internal hazard index values are less than unity.

Radiometric, SEM and XRD investigation of the Chituc black sands, southern Danube Delta, Romania

The black sand of the Chituc marine sand bank, northern of the city of Navodari (Romania), presents anomalous high radioactivity. Field measurements recorded in some places dose rate up to 200 nSv/h, significantly overpassing the average value of 44 ± 20 nSv/h along the entire Southern sector of Romanian Black Sea shore. Gamma ray spectrometry performed on both Slanic-Prahova Underground Low Background Laboratory and Geological Institute of Romania Radiometric Facilities showed with clarity the dominance of (228)Ac radioisotope in the 50 microns fraction together with the (226)Ra and traces of (40)K. No significant amount of anthropogenic (137)Cs was identified. Based on radiometric as well as on SEM-EDAX and XRD determinations we come to the conclusion that the evidenced radioactivity could be attributed to both uranium and thorium series in the zircon and monazite fractions and to a lesser extent to potassium in the feldspars.

Activity concentration of natural radioactive nuclides in nonmetallic industrial raw materials in Japan

Natural materials such as rock, ore, and clay, containing natural radioactive nuclides are widely used as industrial raw materials in Japan. If these are high concentrations, the workers who handle the material can be unknowingly exposed to radiation at a high level. In this study, about 80 nonmetallic natural materials frequently used as industrial raw materials in Japan were comprehensively collected from several industrial companies, and the activity concentrations of (238)U series, (232)Th series and (40)K in the materials was determined by ICP-MS (inductively-coupled plasma mass spectrometer) and gamma ray spectrum analyses. Effective doses to workers handling them were estimated by using methods for dose estimation given in the RP 122. We found the activity concentrations to be lower than the critical values defined by regulatory requirements as described in the IAEA Safety Guide. The maximum estimated effective dose to workers handling these materials was 0.16 mSv y(-1), which was lower than the reference level (1-20 mSv y(-1)) for existing situation given in the ICRP Publ.103.