Levels Of Natural Radionuclides Research Articles

External gamma radiation levels and natural radioactivity in soil around a phosphate fertilizer plant at Mumbai

Fertilizers containing phosphate have been used worldwide in increasing quantities in order to replenish natural nutrients, which are being continuously depleted from the soil by virtue of farming activities. Phosphate rocks together with potassium ores and nitrogenous compounds are the main raw materials used for industrial fertilizer production. Rock phosphate ore processing and disposal of phosphogypsum contribute to enhanced levels of natural radionuclides in the environment. The levels of naturally occurring radionuclides such as 238U, 232Th, 226Ra and 40K in soil samples collected around a phosphate fertilizer plant were estimated. Radium equivalent activity, external hazard index and external dose rate due to natural gamma background at various locations around the plant were also measured.

Natural radioactivity assessment of a phosphate fertilizer plant area

Rock phosphate ore processing and disposal of phosphogypsum contribute to enhanced levels of natural radionuclides in the environment. The concentration of naturally occurring radionuclides in soil, rock phosphate and phosphogypsum samples collected around a phosphate fertilizer plant were determined. Also the external background gamma levels were surveyed.238U, 232Th, 226Ra and 40K activities in soil samples were 21–674Bq/kg, 11–44Bq/kg, 22–683Bq/kg and 51–295Bq/kg respectively. The external background gamma radiation levels in the plant premises were ranging from 48 to 133 nGy/h.

Radioactivity measurements in soils surrounding four coal-fired power plants in Serbia by gamma-ray spectrometry and estimated dose

The study of spatial distribution of activity concentration of 238U, 226Ra, 210Pb, 232Th, 40K, and 137Cs radionuclides in the surface soil samples (n = 42) collected in the vicinity of four coal-fired power plants in Serbia is presented. Radioactivity measurements in soils performed by gamma-ray spectrometry showed values [Bqkg-1] in the range: 15-117 for 238U, 21-115 for 226Ra, 33-65 for 210Pb, 20-69 for 232Th, 324-736 for 40K, and 2-59 for 137Cs. Surface soil radio-activity that could have resulted from deposition of radionuclides from airborne discharges or resuspension of ash from disposal sites showed no enhanced levels. It was found that variation of soil textural properties, pH values, and carbonate content influenced activity levels of natural radionuclides while radiocesium activities were associated with soil organic matter content. Modification of some soil properties was observed in the immediate vicinity (<1 km) of power plants where the soil was more alkaline with coarser particles (0.2-0.05 mm) and carbonates accumulated. Calculated average values of the absorbed gamma dose rate and annual external effective dose originating from the terrestrial radionuclides were 69.4 nGy/h and 0.085 mSv, respectively.

The measurement of gamma-emitting radionuclides in beach sand cores of coastal regions of Ramsar, Iran using HPGe detectors

Radionuclides which present in different beach sands are sources of external exposure that contribute to the total radiation exposure of human. 226Ra, 235U, 232Th, 40K and 137Cs analysis has been carried out in sand samples collected at six depth levels, from eight locations of the northern coast of Iran, Ramsar, using high-resolution gamma-ray spectroscopy. The average Specific activities of natural radionuclides viz., 226Ra, 235U, 232Th, 40K and 137Cs, in the 0–36cm depth sand were found as: 19.2±0.04, 2.67±0.17, 17.9±0.06, 337.5±0.61 and 3.35±0.12 Bqkg−1, respectively. The effects of organic matter content and pH value of sand samples on the natural radionuclide levels were also investigated. Finally, the measured radionuclide concentrations in the Ramsar beach were compared with the world average values, as reported by UNSCEAR (2000). None of the studied beaches were considered as a radiological risk.

Submarine groundwater discharge: Natural radioactivity accumulation in a wetland ecosystem

Submarine groundwater discharge (SGD) has attracted the interest from the scientific community over the past decade for its impact on biogeochemical cycles of coastal ecosystems and/or management of water resources. SGD is associated with a flow of natural radionuclides (Ra isotopes and 222Rn), which are often used as SGD tracers that can significantly increase the natural background radiation. Although in many circumstances the discharge is produced directly to the sea and therefore the increase of natural radioactivity levels can generally be considered negligible due to a dilution processes, the discharge into coastal wetlands (marshes, coastal lagoons or ponds), with somewhat restricted exchange with the open sea, may require a detailed study of the distribution of natural radionuclides and their effects on the coastal ecosystem. The Peníscola marsh is a Mediterranean coastal wetland where such studies may be of special interest because it is fed exclusively by groundwater, mainly discharging from a deep aquifer with high natural radioactivity content.In the Peníscola marsh, brackish groundwater discharging through the wetland sediments is enriched in radionuclides to maximum values of 2.8 and 616kBqm−3 of 226Ra and 222Rn, respectively. These high dissolved concentrations result in high levels of 222Rn in air (up to 36Bqm−3) and 210Pb and 210Po dissolved in water (20 and 5.7Bqm−3, respectively). These elevated levels of natural radionuclides in the Peníscola marsh are also responsible of the significant increase in 210Po and 210Pb contents in both fish and plants.

Transfer of natural radionuclides from hay and silage to cow’s milk in the vicinity of a former uranium mine

After the closure of the former Žirovski Vrh uranium mine in Slovenia, mining and milling wastes were deposited on two waste piles, which are located close to the mine. These wastes contain elevated levels of natural radionuclides from the uranium decay chain. Due to different migration processes (erosion, aerial deposition, through groundwater), these radionuclides can be transported via fodder into cow’s milk, which is an important foodstuff for Slovenian people. Therefore, natural radionuclides were analysed in the transfer food chain from soil to cow’s fodder and cow’s milk. After sampling, 238U, 234U, 230Th, 226Ra, 210Pb and 210Po were determined using radiochemical separation methods and alpha spectrometry or proportional counting. Hay and silage to milk concentration ratios (kg dry weight L−1) were calculated and were 0.260 for 238U, 0.255 for 230Th, 0.070 for 226Ra, 0.021 for 210Pb and 0.019 for 210Po. The calculated annual ingestion dose due to milk consumption for the natural radionuclides analysed was 9 μSv/year for adults and 389 μSv/year for infants with the highest contribution of 210Po (51% for adults and 63% for infants) and 210Pb (36% for adults and 24% for infants). This study provides new data quantifying the transfer of natural radionuclides to milk, which is a parameter for which there have been very few previously reported values.

Effects of Food Diet Preparation Techniques on Radionuclide Intake and Its Implications for Individual Ingestion Effective Dose in Abeokuta, Southwestern Nigeria

The radioactivity measurements in food crops and their diet derivatives and farm soil samples from Abeokuta, one of the elevated background radiation areas in Nigeria have been carried out in order to determine the concentration levels of natural radionuclides (40K, 226Ra and 232Th). The activity concentrations of the natural radionuclides in the samples were determined via gamma-ray spectrometry using a 76 mm × 76 mm NaI(Tl) detector. Different common food crops representing the major sources of dietary requirements to the local population were collected for the measurements. The collected food crops were prepared into their different derivable composite diets using preparation techniques locale to the population. Using available food consumption data and the activity concentrations of the radionuclides, the ingestion effective doses were evaluated for the food crops and diet types per preparation techniques. For the tuberous food crop samples, the annual ingestion effective doses in the raw and different composite diets were 0.02 - 0.04 μSv and cumulatively 0.04 - 0.05 μSv while in the non-tuberous crops the doses were 0.44 - 0.70 μSv and cumulatively greater than 1 μSv respectively. Results of the study indicate that method of diet preparation is seen to play a major role in population ingestion dose reduction especially for tuberous crops than in non-tuberous crops. The study also showed that more ingestion dose could be incurred in diets prepared by roasting techniques. The result of the study will serve as a useful radiometric data for future epidemiological studies in the area and for food safety regulations and policy implementations in the country.

Natural variation in 210Po and 210Pb activity concentrations in the urine of Finnish population groups

A study to determine activity concentrations of (210)Pb and (210)Po in the urine of certain Finnish population groups was conducted, to investigate the variation in natural background level of urinary excretion. The study participants were divided into three groups mainly based on their diet. The first group comprised recreational fishermen and the second group represented people consuming more reindeer meat than an average Finn, while people using drinking water with very high activity concentrations of (210)Po were selected for the third group. The fourth group was a control group. The mean urinary excretion of (210)Po in groups 1 and 2 was 73 and 100 mBq d(-1), respectively. These values were higher than the value of the control group (20 mBq d(-1)) and the mean values reported in the literature. The mean daily urinary excretion of (210)Pb in groups 1 and 2, 70 and 52 mBq d(-1), was also slightly higher than that in the control group (32 mBq d(-1)). In contrast, the excretion rates of both (210)Po and (210)Pb for the members of group 3 were one to two orders of magnitude higher than those reported in the literature. This was clearly due to the elevated levels of natural radionuclides in their drinking water. The present study demonstrates the importance of possessing good knowledge of the background levels, in order to allow the determination of the additional exposure due, for example, to the malevolent use of radiation.

The effects of physico-chemical properties on natural radioactivity levels, associated dose rate and evaluation of radiation hazard in the soil of Taiwan using statistical analysis

Activity concentrations using gamma-ray spectrometer and distributions of natural radionuclides in soil samples collected were investigated to assess the environmental radioactivity and characterization of radiological hazard. The average concentrations of 238U, 232Th series and 40K in the 5 cm depth soil were 22.53, 33.43 and 406.62 Bq kg−1, respectively, which was within world median ranges in the UNSCEAR 2000 report. The average absorbed dose rate estimated by soil activity and annual effective doses were 49.32 nGy h−1 and 60.48 μSv, respectively. Since the soil is an important building material, the mean radium equivalent activity (Raeq), external (Hex) and internal (Hin) hazard index using various models given in the literature for the study area were evaluated as 101.72 Bq kg−1, 0.27 and 0.34, respectively, which were below the recommended limits. The effects of pH value, conductivity, true density and textural properties of soil samples on the natural radionuclide levels were also studied. The application of cluster analysis (CA) and principal component analysis (PCA), coupled with Pearson correlation coefficient analysis, were utilized to analyze the data, identify and clarify the effects of physico-chemical properties on natural radioactivity levels. The CA and PCA results showed that the former method yielded three distinctive groups of the soil variables whereas the latter one yielded the number of variables into three factors with 87.5% variance explanation.

Radiochemical characterization of mineral waters in the Eastern Black Sea Region, Turkey

This study has evaluated the levels of natural radionuclides and chemical components of mineral waters in the Eastern Black Sea Region (Turkey). The mean activity concentrations of (226)Ra, (232)Th, (137)Cs, (40)K, gross alpha and gross beta were found as 129, 33, 28, 714, 125 and 170 mBq L(-1), respectively. Due to consumption of mineral waters, the radiological impact of them on the inhabitants was calculated by taking the annual intake into account through ingestion of aforementioned radionuclides. The estimated effective doses from mineral water were found to be 13.20 μSv year(-1) ((226)Ra), 2.74 μSv year(-1) ((232)Th), 0.13 μSv year(-1) ((137)Cs) and 1.62 μSv year(-1) ((40)K). The overall contribution of these radionuclides to the committed effective dose from a year's consumption of mineral water in the region is therefore estimated to be only 17.69%, which is in concordance with the recommended WHO value (100 μSv year(-1)). The chemical analysis results showed that these waters contain Na, Al, P, Cl, K, Ca, V, Mn, Fe, Ni, Cu and Zn elements. These values were evaluated and compared with the internationally verified values. This study provides important information for consumers and authorities because of their internal radiochemical exposure risk from mineral water intake.

Radiochemical Characterization of Phosphogypsum for Engineering Use

The new phosphogypsum (PG) waste management policy allowed to reduce the negative environmental impact of this residue by finding better alternatives uses with an extremely limited radiological impact. Building material could be one of these alternatives that could lead to the production of final products with good mechanical properties and very limited radionuclides content. The optimization of the radioactive levels in the building materials when PG is used for its production requires the previous knowledge of the content of naturally occurring radionuclides in the PG waste. This article aims the radioactive characterization of two different PG sources (from Spain (Fertiberia S.A., Huelva) and Tunisia (Sfax), before being incorporated in building materials. For this purpose, the natural selected radionuclides content belonging to uranium and thorium decay series and 40K was determined, by means of two different methods: i) gamma spectrometry with high-purity germanium detectors and ii) laser-induced kinetic phosphorimetry (KPA-11 Chemcheck Instruments Inc., Richland, WA). Also, the semiquantitative chemical composition, the mineralogical study and the morphological aspect of the PG samples were analysed. The results obtained from both techniques show that 226Ra and 210Po are the main source of the radioactivity in both studied PG samples. However, PG samples from Tunisia present low natural radionuclide levels (30.7 Bq?kg–1 average value for 238U, 188 Bq?kg–1(226Ra), 163 Bq?kg–1(210Pb), 12.4 Bq?kg–1 (232Th)) compared to the level of natural radionuclides in PG samples from Huelva (102 Bq?kg–1 average value for 238U, 520 Bq?kg–1(226Ra), 881 Bq?kg-1(210Pb) and 8 Bq?kg-1 (232Th). Both PG fulfil European Commission Recommendation (ECR) for the maximum activity concentrations of naturally-occurring radionuclides for industrial by product used in building materials in the European Union.

A first order assessment of the potential radiological impact of foodstuffs grown in a catchment area influenced by mining and mineral processing industries

Natural radioactivity is associated with the vast mineral resources in South Africa in such concentrations that the radionuclides from the natural uranium and thorium decay series are found to pose concern for public exposure to communities living around these areas. Consumption of water and food is usually the most important route by which natural radionuclides can enter the human body and assessment of natural radionuclide levels in different foods and diets is therefore important to estimate the intake of these radionuclides by man. Sensitive measurement of three major radionuclides (in addition to 238 U, 234 U, 232 Th, 226 Ra, 224 Ra and 223 Ra) is necessary to calculate the estimated annual dose with a high degree of certainty i.e. 230 Th, 210 Pb and 210 Po, while 231 Pa, 227 Ac and 228 Ra also require improved sensitivity. In order to evaluate the yearly dose due to an individual source at a screening level of 25 μSv/a, one is faced with a required lower limit of determination (LLD) of 0.1 to 0.5 Bq/kg for certain foodstuffs. In this study the potential radiological impact of foodstuffs grown in a catchment area influenced by mining and mineral processing industries in South Africa, was determined by measuring the natural radionuclides in a number of foodstuffs collected from the area. The radionuclides were measured by non-destructive techniques such as Instrumental Neutron Activation Analysis (INAA) and low background gamma spectrometry. The assessment of natural radionuclides in foods allowed us to evaluate the items that present the highest risk to the population, and compare this to the limits established by the National Nuclear Regulator (NNR). From the public’s point of view it is important to ensure the population that the contaminant levels in specific food as a result of mining activities, do not exceed the permissible limits. For the majority of the analysed foodstuffs, the estimated dose was less than 250 μSv/a. Overestimation of dose, due to poor measurement detection limits, was clearly indicated for some of the samples. For most of the analysed nuclides, suitable data for evaluation of the yearly dose at the screening level of 25 μSv/a was obtained by broad energy gamma analysis of ashed samples. However, nuclides such as 230 Th, 210 Po and 231 Pa has to be analysed by radiochemical separation through acid destruction of dried foodstuffs followed by individual element separations to provide suitable data with a low enough LLD not to result in an overestimation of the calculated dose.

Estimation of dose rates to humans exposed to elevated natural radioactivity through different pathways in the island of Ikaria, Greece

A radiological survey has been carried out in the island of Ikaria based on the natural radionuclide inventory in abiotic environment and the consequent dose rate assessment for the critical groups of population. The island of Ikaria-Aegean Sea, Greece is characterised by the presence of mineral and thermo-mineral springs, which have an apparent influence on natural background radiation of the island. The levels of natural radionuclides in spring water (either for spa treatment and household use), potable water (local domestic network), and rock and soil samples were measured in this island. The concentrations of (222)Rn and natural gamma emitters were found to be significantly elevated in spring water and some rock and soil samples. In terms of NORM and TENORM, the external and internal dose rates (mSv y(-1)) were estimated in three groups of population selected on the basis of water use as: habitants of the island, working personnel and bathers in spa installations. According to the derived results, the working personnel in the thermal spa installations are exposed to significant radiological risk due to waterborne (222)Rn with a maximum dose rate up to 35 mSv y(-1), which led to overexposure in terms of the 20 mSv y(-1) professional limits. Therefore, this group can be considered as the critical one for the radiological impact assessment in the island.

Comparison of two sequential extraction protocols for fractionation of natural radionuclides in soil samples

Revised BCR (Bureau Communautaire de Référence) and the Schultz modification of Tessier´s sequential extraction protocols are compared for fractionation of uranium, thorium and radium in soil samples. Six soil samples were collected near to the uranium mill tailings waste pile and some of them had enhanced levels of natural radionuclides. The samples were processed by both protocols and the radionuclide content assayed by alpha spectrometric determination. The analysis revealed that results obtained by the two protocols are not fully comparable as data are mostly protocol- and element-dependent. Nevertheless, general conclusions about potential source of the particular radionuclide, which could be drawn from the specific study carried out, are mostly similar for both protocols.

Natural radioactivity as an impact factor in drinking water quality

This study has evaluated the levels of natural radionuclides in spring water and drilled water, which are used as potable water reservoirs and samples from the local water supply network, in the island of Ikaria in the Aegean Sea and potable spring water in Loutraki in the Korinthiakos Gulf, Greece. The activity concentrations of 226Ra and 222Rn were in the range of <0.1–0.7 Bq l-1 and <0.1–114 Bq l-1, respectively. The radiological impact on the habitants, due to consumption of drinking water, was calculated taking into account the annual intake, through ingestion, of 226Ra and 222Rn. In order to estimate the radiological impact from 222Rn inhalation, due to its release from water, the mean contribution of the waterborne 222Rn to the indoor air concentrations was evaluated on the basis of the transfer coefficient of 10-4 from water to air. The effective dose equivalents due to 226Ra ingestion were in the range of 25–175 &b.mu;Sv y-1, with the maxima reaching the recommended limit of 100 &b.mu;Sv y-1. The effective dose equivalents due to 222Rn ingestion were in the range of 0.1–114 &b.mu;Sv y-1. For both radionuclides, the highest doses were corresponding to the ingestion of potable spring water, compared to the drilled and tap water. The resulting effective dose equivalent from the inhalation of the waterborne 222Rn, in equilibrium with its daughters, was in the range of 0.36–85 &b.mu;Sv y-1. According to our results, the ingestion of 226Ra presents the higher impact factor of natural radioactivity in drinking water of the studied areas and appropriated remedies should be taken.

Fractionation of natural radionuclides in soils from the vicinity of a former uranium mine Žirovski vrh, Slovenia

As a result of former uranium mining and milling activities at Žirovski vrh, Slovenia, 0.6 million tons of uranium mill tailings (UMT) were deposited onto a nearby waste pile Boršt. Resulting enhanced levels of natural radionuclides in UMT could pose threat for the surrounding environment. Therefore, sequential extraction protocol was performed to assess mobility and bioavailability of 238U, 234U, 230Th and 226Ra in soils from the waste pile and its surrounding. The radionuclides associated with exchangeable, organic, carbonate, Fe/Mn oxides and residual fraction, respectively, were determined. Results showed that the highest activity concentrations for the studied radionuclides were on the bottom of the waste pile. In non-contaminated locations, about 80% of all radionuclides were in the residual fraction. Considering activity concentrations in the UMT, 238U and 234U are the most mobile. Mobility of 226Ra is suppressed by high sulphate concentrations and is similar to mobility of 230Th.

Concentrations of Natural Radionuclides in Municipal Supply Drinking Water and Evaluation of Radiological Hazards

Naturally occurring radionuclides are always present in groundwater used for drinking and cultivation purposes. Intake of these radionuclides through ingestion of drinking water results in radiation doses to humans, which may cause radiological health hazards. This article presents the results of measured concentrations of naturally occurring radionuclides of 226Ra, 232Th, and 40K in municipal supply drinking water in metropolitan Lahore city of Pakistan and an evaluation of consequent gamma radiation doses to the consumers. Multiple water samples were collected from all nine municipal towns of Lahore city of Pakistan and analyzed using gamma spectrometry technique. Mean concentrations of 226Ra, 232Th, and 40K in water samples were of the order of 104 ± 35, 69 ± 17, and 625 ± 85 mBq l− 1 respectively. Mean annual effective radiation doses due to ingestion of all three natural radionuclides from intake of drinking water for age groups of 2–7, 7–12, 12–17 and ≥ 17 years (adults) were evaluated, which were found below the World Health Organization (WHO) (Geneva, Switzerland) recommended limit of 0.1 mSv y− 1. It was observed that as pH increases, concentrations of 226Ra and 232Th decrease in water samples. However, a linear positive correlation was found between 226Ra concentration and water chemical parameters such as, total dissolved solids (TDS) and sulphates content. Data generated in this study may be helpful in establishing background levels of natural radionuclides in drinking water that could be used to distinguish additional contributions when a contamination event occurs in future, as well as, for inception of safety standards by the concerned authorities to maintain radioactive contamination free drinking water supplies for the general public.

The effects of physicochemical properties on gamma emitting natural radionuclide levels in the soil profile of Istanbul

The inventory of gamma-emitting radionuclides was determined in soil samples collected at six depth levels, from 15 locations in Istanbul metropolis. The activity concentrations of (232)Th, (238)U, (40)K were measured by means of gamma spectrometry. The average activity concentrations of (232)Th, (238)U, (40)K in the 30-cm depth soil were found as 32.1, 27.4, 393.1 Bq kg(-1), respectively. The mean value of the absorbed dose rate (D), annual effective dose equivalent (AEDE) from the outdoor terrestrial gamma radiation, Ra equivalent activity (Ra(eq)), and the external hazard index (H(ex)) were calculated as 48.7 nGy h(-1), 59.7 muSv, 104.1 Bq kg(-1), and 0.28, respectively. The effects of organic matter content, textural properties, and pH value of soil samples on the natural radionuclide levels were also investigated. The relations between natural radionuclide level and the physical and chemical properties of studied soil samples were mainly clarified with cluster analysis and Pearson correlation.

The natural radioactivity in vicinity of the brown coal mine Tusnica – Livno, BiH

Coal mine Tusnica is located in South-West part of Bosnia and Herzegovina in the municipality Livno. Coal mine Tusnica consists of two surface coal mines. The first one is brown coal surface deposit called Drage and second one is lignite deposit called Table. The brown coal deposit shows increased levels of natural radionuclides. The highest absorbed dose rate is recorded in the center of the surface coal mine Tusnica-Drage (500 nGy h-1 ) as result of the increased content of uranium and radium in coal (average specific activity of U-238 is 623 ± 23 Bq kg-1 and Ra-226 is 1191 ± 5 Bq kg-1 ). Levels of natural radionuclides in the vicinity of the surface deposit Drage in agricultural soil (about 3 km of the centre mine) are slightly increased due to the use of the coal ash and coal dust for fertilization of the land (U-238 is 142 ± 11 Bq kg-1 and Ra-226 is 197 ± 2 Bq kg-1 ). Obtained results in soil-plant-animal products chain does not show significantly increased levels of natural radionuclides due to the fact that mentioned radionuclides, in general, have a low transfer factors in soil-plant-animal products chain.

Technological exchanged natural radioactivity in vicinity of the Coal Burning Power Plant Kakanj, BiH

CBPP Kakanj is one of the most important Coal Burning Power Plants in Bosnia and Herzegovina (producing power of 450 MW, waste storage site of 5 000 000 tons). Mapping of the measured gamma-dose rate has been performed with the goal of identifying the hot spots in the area of 3×3 km surrounding CBPP Kakanj, with special emphasis on the waste storage site (1×1 km). Maximum measured of the gamma-dose rate surrounding CBPP Kakanj was 140 nGy h-1 and in the area of waste storage site 210 nGy h-1 . Average levels of natural radionuclide in agricultural soil samples in vicinity of CBPP Kakanj are: for 238 U is 41 ± 4 Bq kg-1 , 232 Th is 32 ± 1 Bq kg-1 , 226 Ra is 27 ± 2 Bq kg-1 and 40 K is 486 ± 9 Bq kg-1 . Obtained results in soil-plant-animal products chain does not show significantly increased levels of natural radionuclides due to the fact that mentioned radionuclides, in general, have a low transfer factors in soil-plant-animal products chain.