Natural radioactivity levels in river, stream and drinking water of the northwestern areas of Pakistan

Natural radioactivity in the aquatic media has been determined by collecting samples of river, stream and drinking water from the northwestern areas of Pakistan. The concentrations of ⁴⁰K, ²²⁶Ra and ²³²Th have been measured using a low background gamma-spectrometer and a 10 cm³ planar intrinsic high purity germanium detector. The annual ingestion of these radionuclides, using local consumption rates (average over the whole population) of 0.9 l^.d^-1, were estimated to be 49.2, 6.2 and 1.1 Bq^.y^-1 for ⁴⁰K, ²²⁶Ra and ²³²Th, respectively. A comparison of the annual intakes of these radionuclides, using annual consumption rates of NCRP, ICRP and FBSP shows that the contribution from natural radionuclides to annual intake is slightly greater for NCRP than for ICRP and FBSP consumption rates. However, the estimated values and weighted means of these radionuclides compare well with the world average. The annual effective dose equivalent from drinking water was found to be 3.6^.10^-6 mSv^.y^-1 (²²⁶Ra), 3.2^.10^-12 mSv^.y^-1 (²³²Th) and 2.1^.10^-6 mSv^.y^-1 (⁴⁰K). These values are lower than those given by NCRP.     

Estimation of radiation doses associated with natural radioactivity in sand samples of the north western areas of Pakistan using Monte Carlo simulation

Summary Activity concentrations of naturally occurring radionuclides, i.e., ²²⁶Ra, ²³²Th and ⁴⁰K, were measured in sand samples of north western areas of Pakistan using gamma-spectrometry. The measured ranges of activity concentrations for ²²⁶Ra, ²³² Th and ⁴⁰K were 36.9-51.9, 52.5-67.6 and 680-784 Bq ^. kg^-1, respectively. Associated external dose was calculated using Monte Carlo simulation technique. A theoretical model to determine the gamma dose rate at 1 m height from the sand was employed for calculation the mass attenuation coefficient and self absorption in sand slab for the gamma-energies of these radionuclides and their progeny. The weighted average values of the measured gamma dose rates were 3.3, 4.5 and 12.4 nGyh^-1 for ²²⁶Ra, ²³² Th and ⁴⁰K, respectively, with effective dose of 0.022±0.004 mSv ^. y^-1. Monte Carlo simulation shows that the sand slabs having more than 15 cm effective thickness contribute very little to the external gamma dose rate. The values of the external dose rate and annual effective dose were found to be much lower than the world average as well as from other countries of the world.     

Discovery of the second highest level of radioactive mineral spring in Iran

Summary One of the high-level natural radiation areas (HLNRAs) in Iran is located in the south of Iran in the Hormozgan province. Uranium and its daughters, such as radium and thorium cause areas of elevated natural radiation. An unknown hypothermal mineral and radioactive spring was discovered containing high-level radiation, 42 mSv ^. y^-1 maximum effective dose around spring was measured. ⁴⁰K, ²²⁶Ra and ²³²Th radionuclides were detected with the maximum activity of 11.80 Bq ^. l^-1, 3.48 Bq ^. l^-1 and 2.52 Bq ^. l^-1, respectively. These activities are the second highest in comparison to those in the Ramsar radioactive springs, especially Ab-e-siah spring, which contains 146.5 Bq ^. l^-1 activity. Ocillatoria spp., Lyngbya spp. and a kind of ciliatawere observed in this spring. The results showed that the radioactive spring falls into the sodium chloride category.     

Radon exhalation and natural radiation exposure in low ventilated rooms

In the first part of this paper, the influence of radon (²²²Rn) exhalation rate from walls and air exchange upon its concentration in room air was considered using a simple mathematical room model. The exhalation rates have been determined in ten low ventilated rooms of ten villas in Jeddah city (Western Province) of Saudi Arabia. An electroprecipitation method has been applied for the determination of the ²²²Rn gas concentration in these rooms. The mean ²²²Rn gas concentration was found to be 46.80±8.80 Bq m^?3. The mean ²²²Rn exhalation rate was estimated to be 20.11±6.90 Bq m^?2 h^?1. The mean inhalation dose due to the exposure to ²²²Rn gas was calculated to be 1.18±2.30 mSv y^?1.The second part of this paper deals with a study of natural radionuclide contents of samples collected from the building materials of these rooms under investigations in part one. Analyses were performed in Marinelli beakers with a gamma spectroscopy system to quantify radioactivity concentrations. The collected samples revealed the presence of the uranium–radium (²²⁶Ra) and thorium (²³²Th) radioisotopes as well as ⁴⁰K. The mean activity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K was determined to be 48.30±5.08, 43.90±5.63 and 223.90±7.55 Bq kg^?1, respectively. These activities amount to a radium equivalent (Ra_eq) of 125.96±15.90 Bq kg^?1 and to a mean value of external hazard index (H_ex) of 0.34±0.04.     

The radioactivity of building materials

Summary Radiation exposure of the population can be increased appreciably by the use of building materials containing above-normal levels of naturally occurring radionuclides of terrestrial origin, as high as 1600 Bq^. kg^-1for ⁴⁰K in granites, 700 Bq^. kg^-1for ²²⁶Ra in phosphogypsum and 360 Bq^. kg^-1for ²³²Th in granites. In a 25-year survey including more than two hundreds of different materials were investigated. Of the materials normally used in the building industry, i.e., red clay bricks, cement of Portland Types I and II, concretes, gravels and sand, contain regular levels of the primordial radionuclides. The adsorbed dose rate in indoor air, in general, does not exceed the dose criterion of 80 nGy^. h^-1or 0.3 mSv^. y^-1for the effective dose. Granites and phosphogypsum are the highly radioactive materials for which the absorbed dose rate in indoor air becomes up to five times higher than the dose criterion. It is recommended to avoid the use of those materials without radioactivity control.     

Radioactivity measurements and radiation dose assessments due to natural radiation in Karabük (Turkey)

In this work, the radionuclide activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in surface soils and radon levels in dwellings of Karabük, Turkey were determined in order to evaluate the environmental radioactivity. Concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K radionuclides were determined using gamma spectrometry with using HPGe detector. The etch track detectors (CR-39) were used to determine the distribution of radon concentrations. The average activity concentrations for ²²⁶Ra, ²³²Th and ⁴⁰K were found as 21.0, 23.5 and 363.5 Bq kg⁻¹, respectively. The calculated average annual effective dose equivalent from the outdoor terrestrial gamma radiation from ²²⁶Ra, ²³²Th and ⁴⁰K is 53.5 μSv y⁻¹. The average radon concentration and annual effective dose equivalent of ²²²Rn in Karabük dwellings were obtained 131.6 Bqm⁻³ and 3.32 mSv y⁻¹, respectively. The evaluated data were compared with the data obtained from different countries.     

Radiological significance of Pakistani marble used for construction of dwellings

Natural radioactivity in various types of marbles available in Rawalpindi/Islamabad industrial area have been assessed using HP(Ge) gamma-ray spectrometer. The concentration of ⁴⁰K, ²²⁶Ra and ²³²Th ranges from 6.15 to 159.65 Bq^.kg^-1, 1.45 to 29.34 Bq^.kg^-1 and 1.16 to 6.28 Bq^.kg^-1, respectively. The radium equivalent activity lies between 5.56 to 33.42 Bq^.kg^-1. The average external and internal indices have been found to be 0.03 and 0.05, respectively. The average absorbed dose rate at 1 m was found to be 6.53 nGy^.h^-1. The estimated annual effective dose rate for whole body was found to be 0.04 mSv^.y^-1. These values are smaller than those predicted by UNSCEAR for normal background areas. The marbles analyzed pose less health hazard as compared to Pakistani baked bricks and other construction materials.     

Natural radioactivity of spring water used as spas in Spain

Spring waters used as spas may contain significant amounts of natural radionuclides, so, in some circunstances, a radiation protection issue can arise for the population and/or the spas workers. EU has identified some groups of employees to be exposed to natural radiation in the 1996 Euratom Directive. Among these are workers of thermal spas who may be exposed to high radiation doses due to high radon concentrations in indoor air. In order to evaluate the potencial risk of the spring waters used as spas, gross-α and gross-β activity, ²²⁶Ra and ²²²Rn concentration levels were measured in 82 spas all over the country. Gross-alpha and gross-beta concentrations ranged from LLD to 17 Bq·l⁻¹ and from LLD to 60 Bq·l⁻¹, respectively. ²²⁶Ra concentrations ranged from <4 to 3,660 mBq·l⁻¹. ²²²Rn concentrations ranged from <4 to 1868 Bq·l⁻¹. Correlations between ²²⁶Ra concentrations and gross-α activity were obtained.     

Radiological hazard analysis of Malaysia’s ceramic materials using generic and RESRAD-BUILD computer code approach

In this study, 52 samples of ceramic materials were studied for ²²⁶Ra, ²²²Rn, ²³²Th and ⁴⁰K natural radionuclides using high-purity germanium detector and relevant radiological hazards parameters were also appraised. Furthermore, the long-term variations of the total effective dose equivalent (TEDE) and effects of wall thickness on TEDE were established and analyzed using RESRAD-BUILD computer code. The observed percentage variations of TEDE are 2% and 8% for ²²⁶Ra and ²³²Th, respectively, while no variation observed for external dose due to ⁴⁰K. The estimated indoor doses from the studied ceramic materials are all below the recommended maximum limit.

     

Determination of radium isotopes in mineral and environmental water samples by alpha-spectrometry

Summary A method for the determination of low-level radium isotopes in mineral and environmental water samples by alpha-spectrometry has been developed. Radium-225, which is in equilibrium with its mother ²²⁹Th, was used as a yield tracer. Radium were preconcentrated from water samples by coprecipitation with BaSO₄and iron (III) hydroxide at pH 8-9 using ammonia solution, then isolated from uranium, thorium and iron using a Microthene-TOPO chromatography column at 8M HCl, separated from barium in a cation-exchange resin column using 0.05M 1,2-cyclohexylenedinitrilotetraacetic acid monohydrate at pH 8.5 as an eluant, and finally electrodeposited on a stainless steel disc in a medium of 0.17M (NH₄)₂C₂O₄at pH 2.6 and current density of 400 mA^. cm^-2, and counted bya-spectrometry. Optimum experimental conditions for radium separation, purification and electrodeposition have been studied and discussed in the paper. The lower limits of detection of the method are 0.11 mBq^. l^-1for ²²⁶Ra, ²²⁸Ra and ²²⁴Ra, respectively, if 2 l of water are analyzed. The method has been checked with a certified reference material IAEA-Soil-6 supplied by the International Atomic Energy Agency and reliable results were obtained. Eighteen water samples collected in Italy have been analyzed with the method, the mean radiochemical yields for radium were 86.2±6.5%. The obtained radium concentrations were in the range of 0.50-60.8 mBq^. l^-1for ²²⁶Ra, of 0.10-25.7 mBq^. l^-1for ²²⁸Ra, and of￡LLD-7.97 mBq^. l^-1for ²²⁴Ra. The ²²⁸Ra/²²⁶Ra and ²²⁴Ra/²²⁶Ra ratios were in the range of 0.189-4.45 and￡LLD-0.941, respectively.     

Natural radioactivity and radiological hazards of building materials in Xianyang,China

Common building materials collected from Xianyang, China were analyzed for the natural radioactivity of ²²⁶Ra, ²³²Th and ⁴⁰K using γ-ray spectroscopy. The average activity concentration of ²²⁶Ra, ²³²Th and ⁴⁰K in the studied building materials ranges from 13.4 to 69.9, 13.1–99.1 and 124.7–915.1 Bq kg^?1, respectively. The measured activity concentrations for these radionuclides were compared with the reported data of other countries and with the worldwide average activity of soil. To assess the radiation hazard of the natural radioactivity in all samples to the people, the radium equivalent activity, external hazard index, internal hazard index, indoor absorbed dose rate and total annual effective dose were estimated. The radium equivalent activities of the studied samples are below the internationally accepted values. The external hazard index and internal hazard index of all analyzed building materials are less than unity. The mean values of indoor absorbed dose rate for all building materials except for lime are higher than the world population-weighted average of 84 nGy h^?1 and the total annual effective dose values of building materials are lower than 1 mSv y^?1 except for some cyan brick samples. The study shows the measured building materials do not pose significant source of radiation hazard and are safe for use in the construction of dwellings.     

210Pb and 210Po concentrations in the Venice lagoon ecosystem (Italy) and the potential radiological impact to the local public and environment

In order to evaluate the possible radiological impact to the local public and environment from a phosphogypsum stockpile, ²¹⁰Po and ²¹⁰Pb concentrations in river water, lagoon water, suspended matter, superficial sediment, algae and bivalves samples collected in Venice lagoon area have been investigated. The results show that the mean ²¹⁰Po and ²¹⁰Pb concentrations in river water are 1.42±0.36 mBq^.l^-1 and 1.46±0.39 mBq^.l^-1 with a mean ²¹⁰Po/²¹⁰Pb ratio of 0.98±0.17 and about 60% of them are associated with the particulate; ²¹⁰Po and ²¹⁰Pb contribution from the phosphogypsum stockpile to the river water is negligible. Higher ²¹⁰Po (2.61-5.67 mBq^.l^-1) and ²¹⁰Pb (1.31-3.62 mBq^.l^-1) concentrations in the lagoon waters have been observed if compared with the literature values. About 60% of ²¹⁰Po and ²¹⁰Pb are found in the soluble form with a mean ²¹⁰Po/²¹⁰Pb ratio of 1.79±1.47. ²¹⁰Po and ²¹⁰Pb concentrations in 28 out 37 sediment samples ranged from 26 to 45 Bq^.kg^-1 (dry weight), only 9 sediments with ²¹⁰Po and ²¹⁰Pb concentrations greater than 45 Bq^.kg^-1 are found and most of them are located 1-4 km near the phosphogypsum stockpile. The elevated ²¹⁰Po and ²¹⁰Pb concentrations in the sediments may be due to the contamination from the phosphogypsum stockpile. The mean ²¹⁰Po/²¹⁰Pb ratio (0.986±0.049) in the sediments shows that ²¹⁰Po and ²¹⁰Pb exist in nearly secular equilibrium. ²¹⁰Po and ²¹⁰Pb concentrations in algae vary with different species. The mean ²¹⁰Po and ²¹⁰Pb concentrations in Gracilaria compress and Ulva laetevirens which show a similar behavior, are 3.18±1.23 Bq^.kg^-1 and 2.42±1.26 Bq^.kg^-1 (fresh weight), respectively, with a mean ²¹⁰Po/²¹⁰Pb ratio of 1.45±0.34. The mean concentration factors with respect to the filtered water are 1096±424 for ²¹⁰Po and 1299±680 for ²¹⁰Pb. The mean ²¹⁰Po and ²¹⁰Pb concentrations in the soft part of Mytilus edulis are 23.2±9.7 Bq^.kg^-1 and 0.537±0.203 Bq^.kg^-1 (fresh weight), respectively, with a mean ²¹⁰Po/²¹⁰Pb ratio of 43.6±10.0. The mean concentration factors with respect to the filtered water are 8006±3351 for ²¹⁰Po and 290±109 for ²¹⁰Pb, showing a very high accumulation effect for ²¹⁰Po. The accumulation behaviors of Cerastoderma glaucum and Tapes philippinarum for ²¹⁰Po are similar to Mytilus edulis, but that for ²¹⁰Pb seems less effective, corresponding to a relatively higher ²¹⁰Po/²¹⁰Pb ratio. The estimated committed effective doses from ²¹⁰Po for the individual local public through ingestion of bivalves are in the range of 0.050-0.231 mSv^.y^-1.     

Radiometric analysis of Chinese commercial granites

Summary Due to the widespread use of granites as building and ornamental materials, measurements of ²²⁶Ra, ²³²Th and ⁴⁰K activities in commercial granites have been carried out using a NaI(Tl)g-ray spectrometer with a matrix-inversion-based spectral stripping technique. The concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in Chinese commercial granite range from 14.5 to 204.7 Bq^. kg^-1, 16.7 to 186.7 Bq^. kg^-1and 185.7 to 1745.6 Bq^. kg^-1, respectively. The mean values of the activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in red and pink commercial granites are all higher than those in black and gray commercial ones. The radium equivalent activity (Ra_eq), the external hazard index (H_ex), the internal hazard index (H_in ) and the annual gonadal dose equivalent (AGDE) were also calculated and compared to the international recommended values. Six types of red commercial granites (CBR, MLR, QXR, PBR, JXR, LQR, YDR and TSR) of China do not satisfy the universal standards.     

Concentration of radionuclides in building and ceramic materials of Bangladesh and evaluation of radiation hazard

The concentration of radioactive²²⁶Ra,²³²Th and⁴⁰K in building and ceramic materials of Bangladesh was investigated by γ-spectrometry with two HPGe detectors. Radium equivalent activities, representative level index values, criterion formula, emanation coefficients and²²²Rn mass exhalation rates were estimated for the radiation hazard of the natural radioactivity in the materials. The activity concentrations of the natural radionuclides, radium equivalent activities, emanation coefficients and²²²Rn mass exhalation rates are compared with the corresponding values for building and ceramic materials of different countries. The radium equivalent activities in the samples varied between 30.9 (mosaic stone) and 328.0 Bq·kg⁻¹ (gypsum). The emanation coefficient of the materials ranged from 7.83 (cement) to 33.0% (soil) and the²²²Rn mass exhalation rate ranged from 2.31 (stone chips) to 118.0 μBq·kg⁻¹·s⁻¹ (gypsum).     

Radioactivity mapping of north western areas of Pakistan

Summary A systematic study of natural and fall-out radionuclides was carried out with the environmental samples of soil, vegetation and water from some regions of North West Frontier Province (NWFP) of Pakistan. The pretreatment of the samples was performed in the laboratory using IAEA recommended methods. The analysis of gamma-emitters such as ⁴⁰K, ²²⁶Ra, ²³² Th and ¹³⁷Cs was performed with a high purity germanium detector (HPGe). For the determination of ⁹⁰Sr, a liquid scintillation counting system was used. The average specific activities of ⁴⁰K, ²²⁶Ra, ²³² Th and ¹³⁷Cs have been found to be 307±101 Bq ^. kg^-1, 10.2±3 Bq ^. kg^-1, 24±6 Bq ^. kg^-1 and 2.8±1.3 Bq ^. kg^-1, respectively, in soil samples. Vegetation samples have smaller values of specific activities and even the analysis of water samples showed values less than LLD for earlier reported radionuclides. Other parameters like hazard indices, radium equivalent activities, absorbed dose rates and effective dose equivalents have also been determined. All these parameters have values less than their respective limiting values representing that the surveyed areas have no significant hazard from health point of view. Analysis of ⁹⁰Sr for all the samples showed results below LLD. The present study provides a general background of the detectable radionuclides for the surveyed areas that will be helpful in any radiological emergency.     

Measurement of natural radioactivity and radiation hazard assessment in the soil samples of Visakhapatnam,Andhra Pradesh,India

The present work aims to measure and estimate radioactivity and hazardous radiation indices of the soil. Soil samples were collected from various locations in the Visakhapatnam district in Andhra Pradesh, India. The measurement of specific activity of ²²⁶Ra, ²³²Th, and ⁴⁰K radionuclides is carried out with the help of HP-Ge based gamma spectrometer system. Activity concentration of radionuclides in the samples ²²⁶Ra, ²³²Th and ⁴⁰K ranged from 20 ± 2 to 91 ± 2 Bq.kg^-1, 45 ± 3 to 365 ± 3 Bq.kg^-1, and 400 ± 9 to 607 ± 8 Bq.kg^-1, and the respective mean values are 53.36 Bq.kg^-1, 203.74 Bq.kg^-1 and 479.19 Bq.kg^-1. The measured mean value of the absorbed dose rate is 171.41 nGy.h^-1, which was beyond the worldwide mean outdoor value of 60 nGy.h^-1. Thus, the annual effective dose estimated from the above value is 1.04 mSv.y^-1. The correlation was done among the measured ²²⁶Ra, ²³²Th, and ⁴⁰K activity concentrations. The estimated radium equivalent dose is 381.60Bq.kg^-1. The estimated health hazard index and annual effective dose rates of dwellers of Visakhapatnam were studied and compared to Indian average values. The study will help to generate the baseline data for assessing hazard indices to the public and geological mapping of natural radiation in India.     

Determination of uranium isotopes in environmental samples by alpha-spectrometry

A new and accurate method for the determination of uranium isotopes (²³⁸U, ²³⁴U and ²³⁵U) in environmental samples by alpha-spectrometry has been developed. Uranium is preconcentrated from filtered water samples by coprecipitation with iron(III) hydroxide at pH 9-10 using an ammonia solution and the precipitate is dissolved in HNO₃ and mineralized with H₂O₂ and HF; uranium in biological samples is ashed at 600 °C, leached with Na₂CO₃ solution and mineralised with HNO₃, HF and H₂O₂; uranium in soil samples is fused with Na₂CO₃ and Na₂O₂ at 600 °C and leached with HCl, HNO₃ and HF. The mineralized or leaching solution in 2M HNO₃ is passed through a Microthene-TOPO (tri-octyl-phosphine oxide) column; after washing, uranium is directly eluted into a cell with ammonium oxalate solution, electrodeposited on a stainless steel disk and measured by alpha-spectrometry. The lower limits of detection of the method is 0.37 Bq^.kg^-1 (soil) and 0.22 mBq^.l^-1 (water) for ²³⁸U and ²³⁴U and 0.038 Bq^.kg^-1 (soil) and 0.022 mBq^.l^-1 (water) for ²³⁵U if 0.5 g of soil and 1 litre of water are analyzed. Five reference materials supplied by the IAEA have been analyzed and reliable results are obtained. Sample analyses show that, the ²³⁸U, ²³⁴U and ²³⁵U concentrations are in the ranges of 0.30-103, 0.49-135 and 0.02-4.82 mBq^.l^-1 in waters, of 1.01-7.14, 0.85-7.69 and 0.04-0.32 Bq^.kg^-1 in mosses and lichens, and of 25.6-53.1, 26.4-53.8 and 1.18-2.48 Bq^.kg^-1 in sediments. The average uranium yields for waters, mosses, lichens and sediments are 74.5±9.0%, 80.5±8.3%, 77.8±4.9% and 89.4±9.7%, respectively.     

Radiological mapping in the granodiorite area of Bergama (Pergamon)-Kozak,Turkey

As higher radiation levels are associated with granodiorite area and the maps are more practical to interpret the results of radiological survey, the distributions of the specific activities of ²²⁶Ra, ²³²Th, ⁴⁰K in soil-granite samples and indoor ²²²Rn activities throughout the granodiorite area of Bergama (Pergamon) were mapped in detail. Samples from the granites and soils underlying Kozak-Bergama (Pergamon) granodiorite area were collected and analyzed by HPGe gamma spectrometry system, while indoor radon levels in 20 dwellings of rural areas at this area were measured by the alpha track etch integrated method. This paper represents the baseline maps of natural radioactivity levels (²²⁶Ra, ²³²Th, ⁴⁰K and ²²²Rn) and corresponding absorbed dose rates from outdoors terrestrial gamma radiation.     

Radon concentration in dwellings in Aomori Prefecture, Japan

To obtain an average dose from ²²²Rn to the people in Aomori Prefecture where the first Japan"s nuclear fuel cycling facilities are now under construction, we surveyed ²²²Rn concentrations in 109 dwellings in the Prefecture from 1992 to 1996. The outdoor ²²²Rn concentrations were also measured in gardens of 15 dwellings. The ²²²Rn concentrations were measured with passive ²²²Rn detectors which used a polycarbonate film for counting a-ray and could separate concentrations of ²²²Rn from ²²⁰Rn. Counting efficiencies of the detectors were calibrated with a standard ²²²Rn chamber in the Environmental Measurement Laboratory in USA and in the National Radiological Protection Board in UK. Geometric means of ²²²Rn concentration were 13 and 4.4 Bq^.m^-3 in the dwellings and outdoor, respectively. These values were consistent to nationwide survey results in Japan. The ²²²Rn concentrations in the dwellings depended on their age. The concentrations were higher in recent dwellings than in older ones. The radiation dose from ²²²Rn was estimated, taking into account the occupancy factor for inside and outside of dwellings. The annual dose was 0.32 mSv^.y^-1, and 99% of the dose came from the exposure to ²²²Rn inside the dwelling.     

Natural radiactivity of fresh waters in Serbia

Statistical tests were performed on the -spectrometry measurement data obtained during the last decade for the natural radionuclides⁴⁰K,²²⁶Ra and²³²Th, in water samples collected from the Danube River, the Sava River and its tributaries, ground waters and artificial lakes. The lognormal radiopotassium distribution indicates a single statistical population. The presence of break points in the frequency distribution plots indicates that data for²²⁶Ra and²³²Th do not come from a single statistical population. The annual iongestion of⁴⁰K,²²⁶Ra and²³²Th was calculated and expressed in Bq y^–1.