Effects of environmental factors on the monitoring of environmental radioactivity by airborne gamma-ray spectrometry

This study describes and discusses the results of a 14 month-long campaign (April 2019 to June 2020) aimed at characterizing and quantifying the influence of environmental factors (cosmic rays, rainfall events, soil moisture and atmospheric radon) on airborne radiometric surveys, which are used for mapping the concentrations of potassium (K), uranium (U) and thorium (Th), or for monitoring the natural radioactivity in the environment. A large NaI(Tl) airborne spectrometer (4 down + 1 up detectors of 4 L) was installed at a height of 50 m on a meteorological tower to simulate an airborne hover at the Pyrenean Platform for Observation of the Atmosphere (P2OA) in Lannemezan. The continuous, high frequency acquisition of gamma-rays was accompanied by measurements of rainfall intensity, soil moisture content, atmospheric radon activity and meteorological parameters. A semi-diurnal cycle of apparent ²³²Th and ⁴⁰K was observed and explained by atmospheric thermal tides. Both diurnal and seasonal cycles are also evident in the gamma-ray signal, mostly due to variations of soil moisture at these timescales with a maximum during summer when surface soil moisture (0-5 cm depth) is the lowest. An increase of 25% vol. of the soil moisture content, representing the range of variation between the end of summer (18% vol.) and the beginning of spring (43% vol.) leads to a decrease of gamma-rays in the K and Th window by the same amount. Conversely, these results illustrate the potential of using airborne gamma-ray spectrometry to monitor soil moisture at hectometer scales. The washout of radon-222 progeny during rainfall events influences the count of gamma-rays in the U window by adding an atmospheric component to the soil component. The amplitude of the signal increase in the U window varies with the precipitation rate and reaches 30% for an average event. By clear weather, atmospheric radon-222 volumic activity influences the count rate in the U window by about ±3.8% per Bq m^-3, which translates into an influence of 148%/Bq m^-3/kg Bq^-1 (U). This comprehensive, multi-compartment approach is necessary to optimize and improve the processing and analysis of airborne gamma-ray spectrometry data for high sensitivity environmental studies. These results show the importance of environmental factors on the variability of gamma-ray spectrometry and the importance of taking them into account to accurately map radionuclides activities.

Assessment of internal radiation exposure to Antarctic biota due to selected natural radionuclides in terrestrial and marine environment

The present article introduces data on natural radioactivity (⁴⁰K, ^230,232Th, ^234,238U) in the Antarctic marine and terrestrial environment. Various biota samples were analysed due to internal exposure to ⁴⁰K, ^230,232Th, ^234,238U. Activity concentration of ⁴⁰K was the highest in both marine and terrestrial samples. Mean values of ⁴⁰K activity concentration are 1340 Bq/kg and 370 Bq/kg for the marine and terrestrial samples respectively. ²³⁴U/²³⁸U ratios analysis revealed that sea waters and sea spray are the main source of the uranium in the terrestrial samples. Average ^230,232Th, ^234,238U activity concentrations in the Antarctic biota do not exceed 6 Bq/kg. Weighted internal dose rates are relatively low; they range from approximately 0.1 to 0.6 μGy/h. Statistically significant differences in radionuclide accumulation were discovered between the mosses and lichens. It may point to various mechanisms of the nutrient absorption from the environment by these organisms.

ASSESSMENT OF NORM LEVELS AND RADIOLOGICAL HAZARDS FROM PETROLEUM EXTRACTION IN THE ONSHORE OIL FIELDS, EGYPT

Forty-nine different samples (crude oil, surface soil, produced water and sludge) from onshore oil fields in the Western Desert of Egypt were assessed for naturally occurring radioactive material (NORM) levels using HPGe gamma-ray spectrometer. The average activity concentrations of 226Ra, 232Th and 40K were 25 ± 1.3, 26 ± 1.0 and 21 ± 1.5; 9.8 ± 0.50, 11 ± 0.40 and 94 ± 6.9; 130 ± 6.6, 91 ± 3.4 and 41 ± 3.0; and 180 ± 16, 70 ± 6.9 and 1300 ± 110 Bq kg-1 for crude oil, surface soil, produced water and sludge, respectively. The obtained NORM levels are much below the International Atomic Energy Agency NORM clearance levels. Radiological parameters (radium equivalent activity, absorbed dose rate and annual effective dose) were calculated and compared with the international acceptable limits. The annual effective doses are below 1 and 20 mSv, the ICRP safety limits for the public and workers, respectively. Consequently, insignificant radiological hazards could present for the workers and surrounding environment from petroleum extraction activities in the studied area.

Natural radioactivity and radiological risks of common building materials used in Semnan Province dwellings, Iran

Impact assessment of building materials is a focused topic in the field of radioecology. A radiological survey has conducted to monitor radioactivity of most common building materials in Semnan Province, Iran, and assess the radiation risk. Activity concentrations of 226Ra, 232Th, and 40K were measured in 29 samples including nine commonly used building materials that were collected from local suppliers and manufacturers, using a high purity germanium gamma-ray detector. The activity concentrations of 226Ra, 232Th, and 40K varied from 6.7±1 to 43.6±9, 5.9±1 to 60±11, and 28.5±3 to 1085±113 Bq kg-1 with averages of 26.8±5, 22.7±4, and 322.4±4 Bq kg-1, respectively. By applying multivariate statistical approach (Pearson correlation, cluster, and principal component analyses (PCA)), the radiological health hazard parameters were analyzed to obtain similarities and correlations between the various samples. The Pearson correlation showed that the 226Ra distribution in the samples is controlled by changing the 232Th concentration. The variance of 95.58% obtained from PCA resulted that the main radiological health hazard parameters exist due to the concentration of 226Ra and 232Th. The resulting dendrogram of cluster analysis also shows a well coincidence with the correlation analysis.

ASSESSMENT OF NATURAL RADIOACTIVITY LEVELS AND RADIATION EXPOSURE IN NEW BUILDING MATERIALS IN SPAIN

Novel building materials were manufactured and analyzed for 226Ra, 232Th and 40K using an HPGe gamma-ray spectrometer. The results show that the highest value of 40K was 4530 Bq per kg which was measured in a sample containing fly ashes from olive stones. The highest values of 226Ra and 232Th activities were 181 and 185 Bq per kg, which were measured in a sample with fly ashes from the co-combustion of coal and coke, respectively. On the other hand, the lowest values of 40K, 226Ra and 232Th activities were obtained for samples incorporating mussel shells. The radiological health hazard parameters, such as radium equivalent activity (Raeq), activity concentration index (I), absorbed and effective dose rates, associated with these radionuclides were evaluated. These values are within the EU recommended limits in building materials, except for samples of concrete containing fly ashes from olive stones, coal and coke. This study has contributed to the inclusion of industrial wastes that have not been collected previously in the Naturally Occurring Radioactive Material (NORM) databases on radioactivity of building materials.

Assessment of radioactivity concentration in intertidal sediments from coastal provinces in Oman and estimation of hazard and radiation indices

The natural radioactivity of intertidal sediment samples collected from the beaches of Oman was investigated. Using gamma ray spectrometry, the activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in the sediment samples were measured to have average values of 20.49 ± 3.50, 2.26 ± 0.60 and 44.83 ± 4.60 Bq kg^-1 respectively. The activity levels reported are considerably lower than the worldwide average. The annual effective dose rate was estimated to be 0.015 mSv yr^-1 on average. Additionally, the mean radium equivalent, external and internal indices were 26.89, 0.07 and 0.13 Bq kg^-1 respectively which were well below the risk limits. Gamma and alpha radiation indices were computed to be less than unity and show no exceedance beyond the recommended level. Our results provide baseline data for radioactivity in intertidal sediment samples of Oman and show that intertidal beach sand does not pose significant radiological risk to human 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.

DETERMINATION OF NATURAL RADIOACTIVITY AND RADIOLOGICAL HAZARD ASSOCIATED WITH SEDIMENTS SOURCED FROM OGUNPA RIVER CHANNELS, IBADAN, NIGERIA

The natural radionuclides content and radiological assessment of sediments of the Ogunpa waste-water channel were evaluated to ascertain the radiological safety of the sediments as a building material. The mean activity concentrations of 40K, 226Ra and 232Th in Bq kg-1 were found to be 171 ± 69, 11 ± 5 and 10 ± 4, respectively. The overall mean radium equivalent 29 ± 13 Bq kg-1 was <370 Bq kg-1 that can give the maximum recommended dose of 1 mSv to the general public. The activity concentrations of the radionuclides were all less than world average for soils and sediments. Thus, the use of the sediments from the Ogunpa water channel as building material is safe and would not pose any significant radiological health hazards.

MEASUREMENT OF THE ACTIVITY CONCENTRATIONS OF GAMMA EMITTING RADIONUCLIDES IN TOOTHPASTE SAMPLES AND ASSESSMENT OF THE CORRESPONDING ANNUAL EFFECTIVE DOSES

It is inevitable that we are exposed to radiation daily from various sources and products that we consume on daily basis. The use of toothpaste for oral hygiene is one of the most common daily practices by humans and yet very little data are available regarding its radiation content. In this work, we investigated the concentrations of gamma emitting radionuclides in toothpaste samples consumed in Jordan. 40K and 226Ra were detected in almost one-third of the samples, whereas 228Ra was detected in nearly half of them. The corresponding activity concentrations in the detected samples were in the ranges of 68.7-154.2, 4.6-14.1 and 1.3-10.0 Bq/kg, respectively. Dose assessment of accidental ingestion of toothpaste for children and adults was made, and its contribution to the annual effective dose was found to be very minimal with maximum doses of ~2.9 and 1.3 μSv for children and adults, respectively.

Natural radionuclides and assessment of radiological hazards in MuongHum, Lao Cai, Vietnam

²²⁶Ra, ²³⁸U, ⁴ K, and ²³²Th (²²⁸Ra) activity concentrations of 61 soil samples distributed surrounding the rare earth element mine (NORM), MH, Lao Cai, Vietnam have been measured by HPGe detector. The activity concentrations of ²²⁶Ra, ²³⁸U, ⁴ K, and ²³²Th (²²⁸Ra) range from 1179 to 6291 Bq/kg, from 1024 to 8351 Bq/kg, from 260 to 3519 Bq/kg, and from 1476 to 35546 Bq/kg in the ore body and from 21.3 to 964 Bq/kg, from 23.4 to 1635 Bq/kg, from 124 to 3788 Bq/kg, and from 40.9 to 6107 Bq/kg outside the ore body in respective. The study area is considered as the high local natural background radiation with the concentration of ²²⁶Ra, ²³⁸U, ⁴ K, and ²³²Th (²²⁸Ra) of 156, 254, 647, and 908 Bq/kg in respective. Regarding the spatial distribution, the measured radionuclide concentrations are independent of the distance from measured points to the ore body. With regard to the hazard indices, the average calculated radiological hazard indices, including absorbed gamma dose rate, effective dose equivalent, and excess lifetime cancer risk significantly exceed the global average values. There is a disequilibrium between ²³⁸U/²²⁶Ra concentrations in studied soil samples. The results also found that the ²³²Th (²²⁸Ra) concentration and total absorbed gamma dose rate show a strong positive correlation (coefficient of determination, R² = 1).

Measurement of Natural Radionuclides and Assessment of Radiation Hazard in Coal from Parts of China

ABSTRACT

To study the content of radionuclides in coal and to assess its associated radiological impact on the environment for potential radiological risk assessment, a total of 40 coal samples were collected from various mining areas in eight provinces of China. The specific activities of 226Ra, 232Th, 40K, 210Pb, and 238U were measured in all samples using an HPGe gamma-ray spectrometer, and results were compared with available data from other similar studies. The results reveal that the radium equivalent activity was 74.20 Bq kg-1, external hazard index was 0.20, internal hazard index was 0.27, representative gamma index was 0.52, and indoor and outdoor annual effective dose rates were 0.16 nSv y-1 and 0.04 nSv y-1, respectively. Absorbed gamma dose rate in air was 32.87 nGy h-1. In general, these values are lower than the respective threshold limits recommended by UNSCEAR, and the radiation risk to the public is extremely small.

137Caesium, 40K and total K in Boletus edulis at different maturity stages: Effect of braising and estimated radiation dose intake

We studied activity concentrations of artificial ¹³⁷Cs and natural ⁴⁰K and concentration of total potassium (K) in Boletus edulis at different maturity stages (button, young - white, large - white and large - yellow), and the effect of braising and human dietary intake. Mushrooms were collected from the northern region of Poland in 2019. The ¹³⁷Cs activity concentration was significantly higher in raw and braised button stage samples and decreased as the fruitbody matured, but conversely, ⁴⁰K was lower in the raw button stage than in older fruitbodies. ¹³⁷Cs activity concentrations in raw, button stage B. edulis were 36 ± 1 Bq kg^-1 ww (360 ± 1 Bq kg^-1 dw), increasing to 70 ± 2 Bq kg^-1 ww (290 ± 7 Bq kg^-1 dw) when braised. This activity was around fourteen-fold higher (p < 0.0001) than at higher maturity stages which showed 2.5 ± 0.7 Bq kg^-1 ww (25 ± 7 Bq kg^-1 dw) in raw and 4.9 ± 0.7 Bq kg^-1 ww (19 ± 4 Bq kg^-1 dw) in braised fruitbodies. In comparison to raw B. edulis, braising enriched the activity concentrations of ¹³⁷Cs at 110 ± 69% and ⁴⁰K at 80 ± 56% on a whole (wet) weight basis.

The presence of radioactive heavy minerals in prospecting trenches and concomitant occupational exposure

Uranium, perhaps the most strategically important component of heavy minerals, finds particular significance in the nuclear industry. In prospecting trenches, the radioactivity of 238U and 232Th provides a good signature of the presence of heavy minerals. In the work herein, the activity concentrations of several key primordial radionuclides (238U, 232Th, and 40K) were measured in prospecting trenches (each of the latter being of approximately the same geometry and physical situation). All of these are located in the Seila area of the South Eastern desert of Egypt. A recently introduced industry standard, the portable hand-held RS-230 BGO gamma-ray spectrometer (1024 channels) was employed in the study. Based on the measured data, the trenches were classified as either non-regulated (U activity less than 1000 Bq kg-1) or regulated (with 238U activity more than 1000 Bq kg-1). Several radiological hazard parameters were calculated, statistical analysis also being performed to examine correlations between the origins of the radionuclides and their influence on the calculated values. While the radioactivity and hazard parameters exceed United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) guided limits, the mean annual effective doses of 0.49 and 1.4 mSv y-1 in non-regulated and regulated trenches respectively remain well below the International Commission on Radiological Protection (ICRP) recommended 20 mSv/y maximum occupational limit. This investigation reveals that the studied area contains high uranium content, suitable for extraction of U-minerals for use in the nuclear fuel cycle.

Health risk assessment of radioactive footprints of the urban soils in the residents of Dera Ghazi Khan, Pakistan

The aim of the study was to evaluate the radiation levels, radiological doses and excess lifetime cancer risk possessed by the urban soils that were collected from the vicinity of the exclusive mining and excavation centers of Dera Ghazi Khan. The high purity germanium detector was utilized for assessment of naturally occurring radionuclides (NORMs) in soil and results showed that the average activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K (37 Bq/kg, 43.07 Bq/kg, 737 Bq/kg respectively) surpassed the world's average documented values (35 Bq/kg, 30 Bq/kg, and 400 Bq/kg respectively). Moreover, the average values of radiological hazards assessment like radium equivalent, internal and external hazard indices, absorbed dose rate, annual gonadal dose equivalent and excess lifetime cancer risk were 155.70 (Bq/kg), 0.4, 0.5, 73.96 (nGy/h) 90.73 (μSv/y), 476.24 (μSv/y) and 0.31(10^-3) respectively. The data acquired was analyzed using descriptive statistics, cluster analysis and principal component analysis. ArcGIS (10.5) software was utilized for developing maps of radionuclide's concentration for the study area. Results of the study may serve as an important baseline radiometric data for future epidemiological studies and monitoring initiatives in the study area.

Evaluation of radionuclide concentrations and average annual committed effective dose due to medicinal plants and soils commonly consumed by pregnant women in Osukuru, Tororo (Uganda)

The intention of the study was to establish the activity concentrations and the annual committed effective dose due to ingestion of medicinal plants and soils by pregnant women and their probable effects to infants. The samples of medicinal plants and soils were collected from Osukuru, Tororo District (Uganda). The naturally occurring radionuclides investigated were ²²⁶Ra, ²³²Th and ⁴⁰K and their activity concentrations were determined using NaI gamma detector. In the medicinal plants, the average activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K were found to be 6.04 Bq/kg, 9.65 Bq/kg and 359.59 Bq/kg respectively. African Basil registered the highest activity concentration of ²²⁶Ra of 10.02 Bq/kg, spider plant had the highest activity concentration of ²³²Th of 18.60 Bq/kg whereas the pumpkin registered the highest activity concentrations of ⁴⁰K of 437.92 Bq/kg. The average activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in 'medicinal soils' were 68.87 Bq/kg, 78.20 Bq/kg and 477.44 Bq/kg respectively. The soils from the anthills registered the highest activity concentration of ²²⁶Ra and ⁴⁰K while the one from bricks registered the highest activity concentration of ²³²Th. The annual committed effective dose due to the ingestion of medicinal plants varied from 0.096 to 0.297 mSv/y with an average of 0.194 mSv/y in infants, 0.016-0.040 mSv/y with an average of 0.029 mSv/y for individuals of age range 12-17 years and 0.007-0.018 mSv/y with an average of 0.013 mSv/y for individuals older than 17 years. Whereas the annual committed effective dose due to the ingestion of 'medicinal soils' varied from 1.28 to 1.65 mSv/y with an average of 1.46 mSv/y in infants, 0.23-0.30 mSv/y with an average of 0.26 mSv/y (12-17 years) and 0.07-0.09 mSv/y with an average of 0.08 mSv/y for individuals older than 17 years. In medicinal plants, the annual committed effective dose for the all age groups examined were below 0.3 mSv/y (maximum world permissible as reported UNSCEAR, 2000) while that due to the ingestion of 'medicinal soils' had values higher 0.3 mSv/y in infants. The results of this study show that there is inherent danger to the infants in consuming soils during pregnancy and this should be discouraged.

Multivariate statistical approach on distribution of natural and anthropogenic radionuclides and associated radiation indices along the north-western coastline of Aegean Sea, Greece

A comprehensive radiological survey using multivariate statistical analysis was carried out to evaluate the distribution of ⁴⁰K, ²³²Th, ²²⁶Ra, ²³⁵U, and ¹³⁷Cs, and associated radiation indices in beach sand samples of the coastal area of the Aegean Sea. The activity concentration of selected radionuclides was measured and no clue of recent migration of radiocaesium by not only precipitation but also through an indirect way, such as ocean runoff, was found. As part of radiological risk assessment, external radiation hazard index, radium equivalent activity, effective dose, and absorbed dose rate were estimated. Pearson correlation, cluster, and PCA analysis were used by processing observed radiological parameters to determine the correlation between the radiological parameters and locations. Pearson correlation shows a strong association between all parameters and activity of ²²⁶Ra and ²³²Th. A spatial distribution map was provided to a distinct visual representation of the distribution of radionuclide contents in the study area.

MEASUREMENTS OF SEASONAL VARIATIONS OF RADIOACTIVITY DISTRIBUTIONS IN RIVERINE SOIL SEDIMENT OF ADO-ODO OTA, SOUTH-WEST NIGERIA: PROBABILISTIC APPROACH USING MONTE CARLO

The radioactivity levels were measured using a hand-held gamma-ray survey meter and NaI (Tl) based gamma spectroscopy to evaluate the seasonal variation of radioactivity levels in the riverine area of Ado-Odo Ota. The measured iso-dose map reported higher gamma dose rate of 79 nGy/h, approximately 34% higher than the world average of 59 nGy/h. The values for U-238, Th-232 and K-40 activity levels ranged between 29.9 and 21.6; 103.2 and 31.2; 802.2 and 233.5 with mean values of 26.1, 55.6 and 499.3 Bq/kg, respectively. According to the mean, 5th and 95th percentiles of the probabilities using the Monte Carlo simulation, the Radium equivalent activities and the absorbed dose rates are within their respective recommended limits of 370 Bq/kg and 84 nGy/h. This study could be used to monitor dose rates and radiological risks for the areas covering the small area (Ado-Odo Ota) to the larger area (West African Region) as baseline data.

ASSESSMENT OF THE RADIOACTIVITY OF GAMMA EMITTERS IN BABY FORMULA FOR DIFFERENT AGE GROUPS AND BABY CEREAL CONSUMED IN JORDAN

In the present work, different brands of baby formula and cereal consumed in Jordan were analyzed for their radioactivity content. The activity concentrations of 40K varied with the designated age group in formula with the average concentrations being (in Bq/kg): 160.2 ± 33.5, 219.0 ± 35.0 and 265.2 ± 56.3 for the age groups of 0-6 months, 6-12 months and 1-3 years, respectively. 226Ra was not detected in any of the samples, while 232Th was detected in nearly half the samples with concentrations ranging from 0.22 to 0.82 Bq/kg. 137Cs was detected in only two samples with concentrations of 0.94 and 3.15 Bq/kg. The concentrations of 40K and 232Th in cereal were in the ranges of 23-294 and 0.49-1.48 Bq/kg, respectively. The resulting committed dose was assessed and found in the range of 154-613 μSv, with insignificant contribution from 137Cs, which is within the worldwide range but generally higher than the worldwide average of 290 μSv.

Human exposure levels to ionizing radiation in Agbara Industrial Estate: an impact of Industrial activities in Nigeria

A total of fifty-five soil samples were collected from four locations, namely, residential, industrial, dumpsite, and sewage in Agbara industrial estate, Ogun state, Nigeria. The samples were analyzed using a high purity germanium detector (HPGe) to measure the activity concentration of radionuclides. Background radiation measurements were also taken at each point where soil samples were collected using Geiger Muller (GM) counter. The mean activity concentrations measured in the soil samples were 171.33 for ⁴⁰K, 9.11 for ²³²Th, and 5.05 for ²²⁶Ra in Bq/kg. The mean absorbed dose rate in the air due to radionuclides (⁴⁰K, ²³²Th, and ²²⁶Ra) in the soil is calculated to be 14.77 nGy/h, and the mean annual effective dose equivalent (AEDE) is 0.02 mSv/year. The mean equivalent dose rate (EDR) from GM counter for background radiation is 0.22 μSv/h, and the mean annual effective dose rate (AEDR) is 0.39 mSv/year. These values are below the world average values, except EDR and AEDR with mean values higher than the world standard. The comparison of radiation dose rates revealed that radionuclides contributed 6.7% to background radiation. The equivalent dose (ED_organs) for various organs of the body was calculated, and results showed that values do not pose any immediate health hazard. The excess lifetime cancer risk (ELCR) due to exposure to background radiation indicated that the dwellers and industrial workers in the study area may develop cancer over a lifetime due to accumulated dose.

NATURALLY OCCURRING RADIONUCLIDES IN SOIL SAMPLES OF BURETI SUB-COUNTY OF KERICHO COUNTY KENYA

The activity concentration of soil samples of Bureti sub-county was measured using thallium-activated sodium iodide detector. To ascertain the level of radiation hazard to the public, gamma radiation dose rates were also estimated. The average activity concentration due to 40K, 226Ra and 232Th for soil samples are 1164 ± 70, 106 ± 8 and 79 ± 5 Bqkg-1, respectively. An average dose rate of 145 ± 10 nGyh-1 was recorded, which is about 2.5 times higher than the world average value of 60 nGyh-1(UNSCEAR). On the other hand, an average outdoor effective dose of 0.35 ± 0.02 mSvy-1 was measured, which is lower than the ICRP safety limit of 1 mSvy-1. This shows that the radiation hazards from naturally occurring terrestrial radionuclides in Bureti is low and therefore human radiation exposure is within the accepted limits.

Mean ambient dose rate in various cities, inferred from Safecast data

Safecast is a citizen science project, aimed to environmental monitoring. Its main activity is measuring ambient dose rate all over the world. The freely accessible data, currently (January 2020) more than 120 million observations, were used to calculate mean values of dose equivalent rate in various cities where sufficient data is available. The results mainly reflect dose rate from terrestrial radiation, whose variability is controlled by the one of geochemistry, namely the concentrations of uranium, thorium and potassium. Further influence comes from cosmic radiation and in a few cases, from anthropogenic radiation caused by nuclear fallout. Mean dose rate has been calculated for 330 cities and towns worldwide. Results are shown in tables, graphs and as maps.

Baseline levels of natural radionuclides concentration in sediments East coastline of North Cyprus

In this study, surface sediment samples from the North Cyprus East coast of the Mediterranean Sea were collected to determine the concentrations of three main natural radionuclides (²²⁶Ra, ²³²Th, and ⁴⁰K) using a high-resolution HPGe gamma-spectroscopy system. The activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K in the selected sediment samples ranged from 11.5 to 31.6, 11.8 to 24.9, and 391.7 to 1014 Bq kg^-1 dw (dry weight), respectively. The concentration distribution analysis showed that the kurtosis statistics parameter was negative, and the concentration distribution was less peaked than the normal curve. The mean activity concentrations of ⁴⁰K (628.1 Bq kg^-1) in the sediment samples was higher than the worldwide average (420 Bq kg^-1) concentration. The radium equivalent activity, external hazard, internal hazard and gamma activity concentration indexes were calculated to assess the pollution and risk level of radionuclides. The radiological risk assessment indicated that observed values were below the threshold values.

ESTIMATION OF RADIOLOGICAL EXPOSURE LEVELS IN A MINING AREA BASED ON 238U, 226Ra, 232Th and 40K ACTIVITY MEASUREMENTS: A CASE STUDY FOR BEYLIKOVA-SIVRIHISAR COMPLEX ORE SITE IN TURKEY

The study estimated the radiological exposure levels in a mining area for miners in the Beylikova-Sivrihisar (Turkey) complex ore site containing 238U, 226Ra and 232Th. Sixty samples were collected from the study area based on a geologic map. The radionuclide activities were measured using a 78.5% efficient n-type HPGe detector. The measured mean activities were 1871 ± 38 Bq kg-1 for 238U, 1749 ± 5 Bq kg-1 for 226Ra, 3467 ± 9 Bq kg-1 for 232Th and 309 ± 2 Bq kg-1 for 40K. From the measured results, the external effective dose was calculated to be max. 3.80 ± 0.03 mSv y-1 (mean: 2.04 ± 0.03 mSv y-1) for inside gallery and max. 7.59 ± 0.05 mSv y-1 (mean: 4.08 ± 0.05 mSv y-1) for outdoor. Additionally, the external exposure index was calculated to be Hex = 33.5 ± 0.2(mean: 18.2 ± 0.3) and internal exposure index to be Hin = 45.9 ± 0.3 (mean: 22.9 ± 0.4). The results indicate that additional radiation protection measures should be taken during the mining process if an opencast mining is implemented in Beylikova complex ore deposit.

ESTIMATION OF RADIOLOGICAL HAZARDS DUE TO NATURAL RADIONUCLIDES FROM THE ROSTERMAN GOLD MINE TAILINGS, LURAMBI, KAKAMEGA, KENYA

Radiological hazards associated with naturally occurring radionuclides in materials from Rosterman gold mine were assessed by analysis of 30 samples. The gamma-ray spectrometric analysis of tailing samples reported an average activity concentration of 263 ± 13, 123 ± 6 and 84 ± 4 Bq kg-1 for 40K, 232Th and 226Ra, respectively. The average absorbed dose rate was 124 ± 6 nGy h-1, while the annual effective dose of 0.4 ± 0.02 mSv y-1 for indoor and 0.3 ± 0.01 mSv y-1 for outdoor were reported. The mean and range of radiological parameters (external and radium equivalent) calculated from the tailing samples were within the permissible limits and hence mining of gold at Rosterman has no significant radiological health implication on the miners and the surrounding population.

Geochemical behavior of uranium and thorium in sand and sandy soil samples from a natural high background radiation area of the Odisha coast, India

Owing to their natural radioactivity, uranium (U) and thorium (Th) play significant roles in environmental sciences for monitoring radiation dose and in geological sciences for understanding sedimentary processes. The Odisha coastal area, in eastern India, is a well-known high background radiation area that is rich in monazites and rutile. This area was selected to study geochemical characteristics of U and Th in sand and sandy soil samples. The concentrations of U and Th were measured using inductively coupled plasma mass spectrometry (ICP-MS). The median, geometric mean, and standard deviation for U were determined to be 6, 4.5, and 2.5 μg/g and for Th were 186, 123.3, and 3.1 μg/g, respectively. Major element concentrations were evaluated using X-ray fluorescence spectroscopy to get the mineralogical composition and state of chemical weathering. The ratios of Th/U and Th/K varied from 4 to 37 and from 13 to 1058, respectively. These results clearly indicate that the samples from the coastal region were formed in an oxidizing and intense chemical weathering terrestrial environment with an enrichment of radiogenic heavy minerals (monazites and zircon) and clay mineral association. Since the majority of the samples have undergone moderate to intense weathering in the oxidizing environment, U is leached from the soil and sand matrix. Eventually, Th resides in the matrix and becomes a major source for radiation exposure in the environment. The high ratios of Th/U, along with the strong positive correlation between Th and P2O5, evidence the enrichment of the Th-bearing radioactive mineral, monazite, in these samples.