Radiological impacts of natural radioactivity in Abu-Tartor phosphate deposits, Egypt.

Phosphate and environmental samples were collected from Abu Tartor phosphate mine and the surrounding region. The activity concentration of 226Ra (238U) series, 232Th series and 40K were measured using a gamma-ray spectrometer. The activities of uranium isotopes (238U, 235U and 234U) and 210Pb were measured using an alpha spectrometer and a low-background proportional gas counting system, respectively, after radiochemical separation. The results are discussed and compared with the levels in phosphate rocks from different countries. It seems that the Abu Tartor phosphate deposit has the lowest radioactivity level of exploited phosphate of sedimentary origin. 226Ra/238U, 210Pb/226Ra, 234U/238U and 226Ra/228Ra activity ratios were calculated and are discussed. The radioactivity levels in the surrounding region and the calculated exposure dose (nGy/h) will be considered as a pre-operational baseline to estimate the possible radiological impacts due to mining, processing and future phosphate industrial activities. To minimize these impacts, the processing wastes should be recycled to the greatest possible extent.     

Natural radionuclides in Austrian mineral water and their sequential measurement by fast methods

Ten samples of Austrian mineral water were investigated with regard to the natural radionuclides (228)Ra, (226)Ra, (210)Pb, (210)Po, (238)U and (234)U. The radium isotopes as well as (210)Pb were measured by liquid scintillation counting (LSC) after separation on a membrane loaded with element-selective particles (Empore Radium Disks) and (210)Po was determined by alpha-spectroscopy after spontaneous deposition onto a copper planchette. Uranium was determined by ICP-MS as well as by alpha-spectroscopy after ion separation and microprecipitation with NdF(3). From the measured activity concentrations the committed effective doses for adults and babies were calculated and compared to the total indicative dose of 0.1 mSv/a given in the EC Drinking Water Directive as a maximum dose. The dominant portion of the committed effective dose was due to the radium isotopes; the dose from (228)Ra in most samples clearly exceeded the dose from (226)Ra.     

Environmental characterization and radio-ecological impacts of non-nuclear industries on the Red Sea coast

The Red Sea is a deep semi-enclosed and narrow basin connected to the Indian Ocean by a narrow sill in the south and to the Suez Canal in the north. Oil industries in the Gulf of Suez, phosphate ore mining activities in Safaga-Quseir region and intensified navigation activities are non-nuclear pollution sources that could have serious radiological impacts on the marine environment and the coastal ecosystems of the Red Sea. It is essential to establish the radiological base-line data, which does not exist yet, and to investigate the present radio-ecological impact of the non-nuclear industries to preserve and protect the coastal environment of the Red Sea. Some natural and man-made radionuclides have been measured in shore sediment samples collected from the Egyptian coast of the Red Sea. The specific activities of 226Ra and 210Pb (238U) series, 232Th series, 40K and 137Cs (Bq/kg dry weight) were measured using gamma ray spectrometers based on hyper-pure germanium detectors. The specific activities of 210Po (210Pb) and uranium isotopes (238U, 235U and 234U) (Bq/kg dry weight) were measured using alpha spectrometers based on surface barrier (PIPS) detectors after radiochemical separation. The absorbed radiation dose rates in air (nGy/h) due to natural radionuclides in shore sediment and radium equivalent activity index (Bq/kg) were calculated. The specific activity ratios of 228Ra/226Ra, 210Pb/226Ra, 226Ra/238U and 234U/238U were calculated for evaluation of the geo-chemical behaviour of these radionuclides. The average specific activity of 226Ra (238U) series, 232Th series, 40K and 210Pb were 24.7, 31.4, 427.5 and 25.6 Bq/kg, respectively. The concentration of 137Cs in the sediment samples was less than the lower limit of detection. The Red Sea coast is an arid region with very low rainfall and the sediment is mainly composed of sand. The specific activity of 238U, 235U and 234U were 25.3, 2.9 and 25.0 Bq/kg. The average specific activity ratios of 226Ra/228Ra, 210Pb/226Ra and 234U/238U were 1.67, 1.22 and 1.0, respectively. The relationship between 226Ra/228Ra activity ratio and sample locations along the coastal shoreline indicates the increase of this ratio in the direction of the Shuqeir in the north and Safaga in the south where the oil exploration and phosphate mining activities are located. These activities may contribute a high flux of 226Ra. The concentration and distribution pattern of 226Ra in sediment can be used to trace the radiological impact of the non-nuclear industries on the Red Sea coast.     

Daily ingestion of 232Th, 238U, 226Ra, 228Ra and 210Pb in vegetables by inhabitants of Rio de Janeiro City

The concentrations of the naturally occurring radionuclides 232Th, 238U, 210Pb, 226Ra and 238Ra were determined in the vegetables (leafy vegetables, fruit, root, bean and rice) and derived products (sugar, coffee, manioc flour, wheat flour, corn flour and pasta) consumed most by the adult inhabitants of Rio de Janeiro City. A total of 88 samples from 26 different vegetables and derived products were analyzed. The highest contribution to radionuclide intake arises from bean, wheat flour, manioc flour, carrot, rice, tomato and potato consumption. The estimated daily intakes due to the consumption of vegetables and derived products are 1.9 mBq of 232Th (0.47 microg), 2.0 mBq of 238U (0.17 microg), 19 mBq of 236Ra, 26 mBq of 210Pb and 47 mBq of 228Ra. The estimated annual effective dose due to the ingestion of vegetables and their derived products with the long-lived natural radionuclides is 14.5 microSv. Taking into account literature data for water and milk from Rio de Janeiro the dose value increases to 29 microSv, with vegetables and derived products responsible for 50% of the dose and water for 48%. 210Pb (62%) and 228Ra (24%) were found to be the main sources for internal irradiation.     

Distribution and mobilization of U, Th and 226Ra in the plant-soil compartments of a mineralized uranium area in south-west Spain

The activity concentrations of natural uranium isotopes (238U and 234U), thorium isotopes (232Th, 230Th and 225Th) and 226Ra were studied in soil and vegetation samples from a disused uranium mine located in the Extremadura region in the south-west of Spain. The results allowed us to characterize radiologically the area close to the installation and one affected zone was clearly manifest as being dependent on the direction of the surface water flow from the mine. The activity concentration mean values (Bq/kg) in this zone were: 10,924, 10,900, 10,075 and 5,289 for 238U, 234U, 230Th and 226Ra, respectively, in soil samples and 1,050, 1,060, 768 and 1,141 for the same radionuclides in plant samples. In an unaffected zone, the activity concentration mean values (Bq/kg) were: 184, 190, 234 and 7251 for 235U, 234U, 230Th and 226Ra, respectively, in soil samples and 28. 29, 31 and 80 in plant samples. The activity concentrations obtained for 232Th and 228Th showed that the influence of the mine was only important for the uranium series radionuclides. The relative radionuclide mobilities were determined from the activity ratios. Correlations between radionuclide activity concentrations and stable element concentrations in the soil samples helped to understand the possible distribution paths for the natural radionuclides.     

Radiological hazards of Narghile (hookah, shisha, goza) smoking: activity concentrations and dose assessment

Narghile (hookah, shisha, goza, "water-pipe") smoking has become fashionable worldwide. Its tobacco pastes, known as moassel and jurak, are not standardized and generally contain about 30-50% (sometimes more) tobacco, molasses/juice of sugarcane, various spices and dried fruits (particularly in jurak) and, in the case of moassel, glycerol and flavoring essences. Tobacco contains minute amounts of radiotoxic elements such as (210)Pb, (210)Po and uranium, which are inhaled via smoking. Only very few data have been published on the concentrations of natural radionuclides in narghile tobacco mixtures. Consequently, the aim of this study was to draw first conclusions on the potential hazards of radioactivity in moassel tobacco in relation to narghile smoking. The results indicate the existence of a wide range in the radioactivity contents where the average (range) activity concentrations of (238)U, (234)Th (226)Ra, (210)Pb, (210)Po, (232)Th and (40)K, in Bq/kg dry weight were 55 (19-93), 11 (3-23), 3 (1.2-8), 14 (3-29), 13 (7-32), 7 (4-10) and 719 (437-1044)Bq/kg dry weight, respectively. The average concentrations of natural radionuclides in moassel tobacco pastes are comparable to their concentration in Greek cigarettes and tobacco leaves, and lower than that of Brazilian tobacco leaves. The distribution pattern of these radionuclides after smoking, between smoke, ash and filter, is unknown, except for (210)Po during cigarette smoking and from one existing study during moassel smoking. Radiological dose assessment due to intake of natural radionuclides was calculated and the possible radio-toxicity of the measured radionuclides is briefly discussed.     

Transfer of (40)K, (238)U, (210)Pb, and (210)Po from soil to plant in various locations in south of Syria

Transfer factors of (40)K, (238)U, (210)Pb, and (210)Po from soil to some agriculture crops in various locations in south of Syria (Dara'a and Assuwaydaa districts) have been determined. Soil and vegetable crops (green pepper, cucumber, tomato, and eggplant), legumes crops (lentil, chickpea, and broad bean), fruit trees (apple, grape, and olives) and cereals (barley and wheat) were collected and analyzed for (238)U, (210)Pb, and (210)Po. The results have shown that higher transfer factors (calculated as Bqkg(-1) dry wt. plant material per Bqkg(-1) dry wt. soil) for (210)Po, (210)Pb and (238)U were observed in vegetable leaves than fruits and cereals leaves; the highest values of transfer factor (TF) for (238)U were found to be 0.1 for straw of chickpea. Transfer factors for (210)Po varied between 2.8x10(-2) and 2 in fruits of eggplant and grain of barley, respectively. In addition, several parameters affecting transfer factors of the radionuclides were evaluated. The results can be considered as base values for TF of natural radionuclides in the region.     

Distribution of natural radionuclides in the production and use of phosphate fertilizers in Brazil

The Brazilian phosphate fertilizer is obtained by wet reaction of igneous phosphate rock with concentrated sulphuric acid, giving as final product, phosphoric acid and dehydrated calcium sulphate (phosphogypsum) as by-products. Phosphoric acid is the starting material for triple superphosphate (TSP), single superphosphate (SSP), monoammonium phosphate (MAP) and diammonium phosphate (DAP). The phosphate rock used as raw material presents in its composition radionuclides of the U and Th natural series. Taking this into account, the main aim of this paper is to evaluate the fluxes of natural radionuclides and radioactive disequilibria involved in the Brazilian industrial process of phosphoric acid production; to determine the content of radioactivity in several commercial fertilizers produced by this industry; to estimate their radiological impact in crop soils and the long term exposure due to their application. Radiological characterization of phosphate rock, phosphogypsum and phosphate fertilizers was performed by alpha and gamma spectrometry. The fertilizer samples, which are derived directly from phosphoric acid, MAP and DAP, presented in their composition low activity concentrations for 226Ra, 228Ra and 210Pb. As for U and Th, the concentrations found in MAP and DAP are more significant, up to 822 and 850Bqkg(-1), respectively. SSP and TSP, which are obtained by mixing phosphoric acid with different amounts of phosphate rock, presented higher concentrations of radionuclides, up to 1158Bqkg(-1) for (238)U, 1167Bqkg(-1) for (234)U, 1169Bqkg(-1) for 230Th, 879Bqkg(-1) for 226Ra, 1255Bqkg(-1) for 210Pb, 521Bqkg(-1) for 232Th, 246Bqkg(-1) for 228Ra and 302Bqkg(-1) for 228Th. Long term exposure due to successive fertilizer applications was evaluated. Internal doses due to the application of phosphate fertilizer for 10, 50 and 100 years were below 1mSvy(-1), showing that the radiological impact of such practice is negligible.     

Direct comparison of 210Po, 234Th and POC particle-size distributions and export fluxes at the Bermuda Atlantic Time-series Study (BATS) site

Particle-reactive, naturally occurring radionuclides are useful tracers of the sinking flux of organic matter from the surface to the deep ocean. Since the Joint Global Ocean Flux Study (JGOFS) began in 1987, the disequilibrium between ²³⁴Th and its parent ²³⁸U has become widely used as a technique to measure particle export fluxes from surface ocean waters. Another radionuclide pair, ²¹⁰Po and ²¹⁰Pb, can be used for the same purpose but has not been as widely adopted due to difficulty with accurately constraining the ²¹⁰Po/²¹⁰Pb radiochemical balance in the ocean and because of the more time-consuming radiochemical procedures. Direct comparison of particle flux estimated in different ocean regions using these short-lived radionuclides is important in evaluating their utility and accuracy as tracers of particle flux. In this paper, we present paired ²³⁴Th/²³⁸U and ²¹⁰Po/²¹⁰Pb data from oligotrophic surface waters of the subtropical Northwest Atlantic and discuss their advantages and limitations. Vertical profiles of total and particle size-fractionated ²¹⁰Po and ²³⁴Th activities, together with particulate organic carbon (POC) concentrations, were measured during three seasons at the Bermuda Atlantic Time-series Study (BATS) site. Both ²¹⁰Po and ²³⁴Th reasonably predict sinking POC flux caught in sediment traps, and each tracer provides unique information about the magnitude and efficiency of the ocean's biological pump.     

Distribution of (226)Ra-(210)Pb-(210)Po in marine biota and surface sediments of the Red Sea, Sudan

Activity concentration levels and ratios of (226)Ra, (210)Pb and (210)Po are presented in multicellular marine algae, molluscs, coral as well as in surface marine sediments collected from the shallower waters of the fringing reefs area extending towards north and south (Flamingo bay) of PortSudan harbour, Sudan. The analyses were performed adopting alpha-spectrometry, liquid scintillation and Cerenkov counting techniques. Surface sediments from this coastal region are poor in their radioactivity content in contrast to similar data reported from different coastal areas around the globe. There is surface enrichment of (210)Pb and (210)Po with respect to their progenitor (226)Ra as it is evident from the activity ratios of (210)Pb/(226)Ra (3.03+/-1.79) and (210)Po/(226)Ra (2.23+/-1.56). Among marine plants and animals investigated, the green algae species, Halimeda, and coral species, Favites, show substantial concentration of radium at 8.2Bq/kg and 21.9Bq/kg dry weight, respectively. Similarly, the highest concentration of (210)Po was met in Favites at 38.7Bq/kg followed by brown algae, Cystoseria sp., at 32.6Bq/kg. There is no variation seen among algal species for (210)Pb uptake, however, converse to radium and polonium, Favites (coral) was found to contain the minimum concentration of lead (3.88Bq/kg). In most species there is preferential accumulation of polonium over its parent radium as indicated by (210)Po:(226)Ra activity ratio with Cystoseria (brown algae) showing the highest value at 8.81. On the other hand, (210)Po:(210)Pb activity concentration ratio revealed that coral species Favites (9.97) and the brown algae Sargassum (1.85) have a greater tendency to accumulate (210)Po over (210)Pb, while in the rest of species; this ratio is less than unity.     

Distribution of uranium and radium isotopes in an aquifer of a semi-arid region (Manouba-Essijoumi, Northern Tunisia)

Groundwaters from the Sebkhet Essijoumi drainage basin, situated in northern Tunisia, West of the city of Tunis, were sampled and analyzed for uranium and radium isotopes. Low (234)U/(238)U activity ratios coupled with relatively high (228)Ra and (238)U concentrations were found in the Manouba plain phreatic aquifer, at the northern part of the basin, where remote sensing has indicated that this plain corresponds to the main humid zone of the area. Low (234)U/(238)U ratios probably reflected short residence time for waters in the Manouba plain, and high ratios longer residence time in the south, where water reaching the phreatic aquifer seems to have previously circulated in rocks constituting the southern hills. Assuming that, in the Manouba plain aquifer, the groundwater flows downstream from the Oued Lill pass area to the South-West of the Sebkha, the difference in the (228)Ra/(226)Ra activity ratio suggests that the residence time of water has been 2.8 years longer near the Sebkha than upstream.     

Distributional U, Ra, Pb and Po in soil

A soil profile from 0 to 90 cm was collected in an undisturbeded area of Cape Cod, Massachusetts. Five centimeter increments of the profile were analyzed for ^234,238U, ²²⁶Ra, ²¹⁰Pb and ²¹⁰Po. The factors affecting the activity distribution of these naturally-occurring radionuclides are discussed for this particular soil type.     

Determination and comparison of uranium and radium isotopes activities and activity ratios in samples from some natural water sources in Morocco.

Radiochemical results (238U, 226Ra and 228Ra activities; 234U/238U, 228Ra/226Ra and 226Ra/238U activity ratios) are reported for 42 natural water samples collected from wells, hot mineral springs, rivers, tap water, lakes and irrigation water in 15 Moroccan locations. Results show that 238U activity varies between 4.5 and about 309 mBq l(-1) in wells, 0.6 and 8.5 mBq l(-1) in hot springs, 9.7 and 28 mBq l(-1) in rivers, 2.5 and 16 mBq l(-1) in tap waters and between 6 and 24 mBq l(-1) in lakes. The 234U/238U activity ratio varies in the range 0.87-3.35 in all analyzed water samples except for hot springs where it reaches values higher than 7. Unlike well water, mineral water samples present low 238U activities and high 234U/238U activity ratios and 226Ra activities. The highest activity of radium in mineral water is 150 times higher than the highest activity of 226 Ra found in well water. 226Ra/238U activity ratios are in the ranges 0.07-1.14 in wells, 0.04-0.38 in rivers, 0.04-2.48 in lakes, and 1.79-2115 in springs. The calculated equivalent doses to all the measured activities are inferior to the maximum contaminant levels recommended by the International Commission of Radioprotection and they do not present any risk for public health in Morocco.     

Disequilibrium between uranium and its progeny in the Lake Issyk-Kul system (Kyrgyzstan) under a combined effect of natural and manmade processes

The Kadji-Sai abandoned field of U-bearing brown coal on the southern coast of Lake Issyk-Kul (Kyrgyzstan) poses a threat of radioactive pollution to the world's fifth deepest and second largest pristine highland lake. The valleys of ephemeral streams in the lake catchment are filled with coarse-grained sand and clay, with a background U--Ra activity of 35--55 Bqkg(-1). High activity areas vs. this background come from three sources: (1) scarce outcrops of uraniferous brown coal and mining wastes containing fragments of this coal with (238)U/(226)Ra ratios of 0.8 due to uranium losses through weathering; (2) manmade anomalies caused by a radioactive waste dump, where U was extracted from the ash of coal burnt at a coal-fired power plant. As a result, the (238)U/(226)Ra ratios become 0.15--0.25; (3) six catch pools terraced below the mine, where U activity decreases downslope, and (238)U/(226)Ra ratios reach 150--200. Uranium lost in the extraction process may have been retained on the terraces. The distribution pattern of radionuclides in the bottom sediments of the lake is controlled by water depth and offshore distance. The upper section of homogeneous limy--argillic deposits in the lake center remains undisturbed by currents, as indicated by regular sub-exponential distribution of atmospheric (137)Cs and (210)Pb(atm). Sedimentation rate in the lake center for the past century, found from (210)Pb, was 0.32 mmyr(-1). (238)U/(226)Ra in deep-water sediments was about 3. The activity of uranium adsorbed by sediments from the lake water was estimated by subtraction of the Ra-equilibrium component from the total U activity. Thus, the flux of dissolved U to the bottom sediments was as 2.07 x 10(-7)gcm(-2)yr(-1). The upper section of near-shore deposits was disturbed by currents, with (137)Cs and (210)Pb(atm) more or less uniformly distributed in this layer. Peaks of (226)Ra and (210)Pb occur at different depths from 5 to 20 cm below the sediment surface, with (238)U/(226)Ra ratios 0.28--0.44. The presence of mullite in these sediments indicated that radioactive ash penetrated into the lake in the past. At present, (226)Ra in the ash is buried under a non-radioactive cap.     

Natural radionuclides in bottled water in Austria

Concentration levels of 226Ra, 222Rn and 210Pb were analyzed in domestic bottled waters commercially available in Austria. Concentrations up to 0.23 Bq/l, with a geometric mean of 0.041 Bq/l were found for 226Ra. Concentrations for 222Rn ranged from <0.12-18 Bq/l, the geometric mean being 0.54 Bq/l. Lead-210 was analyzed in selected samples, the concentrations ranging from <2 to 34 mBq/l, with a geometric mean of 4.7 mBq/l. Ingestion doses resulting from consumption of these waters were calculated for the geometric mean and the maximum concentrations of the three radionuclides. The effective dose equivalents for different age groups of the population due to the intake of 226Ra range from 0.001 to 0.22 mSv/y and of 210Pb from 0.0003 to 0.05 mSv/y. Ingestion doses from 222Rn are low compared to those from 226Ra and 210Pb, ranging from 0.0001 to 0.011 mSv/y for adults and children, respectively. The doses are compared to the total ingestion dose from dietary intake of natural radionuclides on an annual basis.     

226Ra/238U disequilibrium in an upland organic soil exhibiting elevated natural radioactivity

This paper presents the results of a study into the anomalous 226Ra/238U disequilibrium (226Ra/238U of 0.5-9) exhibited by an upland organic soil in Co. Donegal, Ireland. Radiochemical speciation of 226Ra, 238U and 225Ra indicates that in this organic soil the high 226Ra/238U ratio is due to loss of 235U relative to 226Ra via oxidation and mobilisation of 238U in the upper layers of the soil and subsequent loss in solution. At the lower, more reducing depths of the soil profile, 238U and 226Ra are essentially in equilibrium. Loss of 238U appears to occur primarily from the easily oxidised organic and iron oxide fractions of the soil, samples exhibiting high 226Ra/238U ratios displaying significantly lower 238U levels in these fractions than samples whose ratio is below the average value for the soil of the valley. Selective enrichment of 226Ra by plants or preferential leaching of 226Ra from the underlying rock is not supported by the results of this study.     

Characterization of the TE-NORM waste associated with oil and natural gas production in Abu Rudeis, Egypt

The present study was conducted to characterize the Technically Enhanced Naturally Occurring Radioactive Materials (TE-NORM) waste generated from oil and gas production. The waste was characterized by means of dry screening solid fractionation, X-ray analysis (XRF and XRD) and gamma-ray spectrometry. Sediment of the TE-NORM waste was fractionated into ten fractions with particle sizes varying from less than 100 microm to more than 3 mm. The results showed that the TE-NORM waste contains mainly radionuclides of the 238U, 235U and 232Th series. The mean activity concentrations of 226Ra (of U-series), 228Ra (of Th-series) and 40K in the waste samples before fractionation (i.e. 3 mm) were found to amount to 68.9, 24 and 1.3 Bq/g (dry weight), respectively. After dry fractionation, the activity concentrations were widely distributed and enriched in certain fractions. This represented a 1.48 and 1.82-fold enrichment of 226Ra and 228Ra, respectively, in fraction F8 (2.0-2.5 mm) over those in bulk TE-NORM waste samples. The activity ratios of 238U/226Ra, 210Pb/226Ra, 223Ra/226Ra and 228Ra/224Ra were calculated and evaluated. Activity of the most hazardous radionuclide 226Ra was found to be higher than the exemption levels established by IAEA [International Atomic Energy Agency, 1994. International Basic Safety Standards for the Protection against Ionizing Radiation and for the Safety of Radiation Sources. GOV/2715/94, Vienna]. The radium equivalent activity (Ra-eq), radon (222Rn) emanation coefficient (EC) and absorbed dose rate (Dgammar) were estimated and these are further discussed.     

Determination of specific activity of (226)Ra, (232)Th and (40)K for assessment of radiation hazards from Turkish pumice samples

The specific activity of (226)Ra, (232)Th and (40)K in 52 Turkish pumice samples collected from 11 geographical areas located in Central Anatolia, Eastern Anatolia, Mediterranean and Aegean regions was determined by gamma-ray spectrometry with a high-purity germanium (HPGe) detector. The specific activity of (226)Ra, (232)Th and (40)K ranged from 12.7+/-0.5 to 256.2+/-9.1Bqkg(-1) with a mean of 89.1+/-65.2Bqkg(-1), 12.3+/-1.0 to 237.9+/-12.2Bqkg(-1) with a mean of 87.0+/-61.4Bqkg(-1) and 300.1+/-5.5 to 1899.0+/-30.8Bqkg(-1) with a mean of 1211.9+/-419.8Bqkg(-1), respectively. Elemental concentrations were determined for U (from 1.0 to 20.7ppm with a mean of 7.2+/-5.3ppm), Th (from 3.0 to 58.6ppm with a mean of 21.4+/-15.1ppm) and K (from 1.0 to 6.1% with a mean of 3.9+/-1.3%). The radium equivalent activity (Ra(eq)), the activity index, the emanation coefficient, the (222)Rn mass exhalation rate, the indoor absorbed dose rate and the effective dose rate were estimated for the radiation hazard of the natural radioactivity in all samples. The calculated mean Ra(eq) value was 306.6+/-177.7Bqkg(-1) (54.6+/-5.5 to 737.6+/-49.0Bqkg(-1)) for all pumice samples. This value is lower than the recommended limit value of 370Bqkg(-1) for building raws and products. The emanation coefficient and the (222)Rn mass exhalation rate of all samples ranged from 29.4 to 42.9% with a mean of 36.2% and from 11.0 to 196.4muBqkg(-1)s(-1) with a mean of 73.5muBqkg(-1)s(-1), respectively. The mean indoor absorbed dose rate and the corresponding mean effective dose rate were 274.6+/-153.6nGyh(-1) (50.4-644.6nGyh(-1)) and 1.35+/-0.75mSvy(-1) (0.24-3.16mSvy(-1)), respectively. For all pumice samples the mean indoor absorbed dose rate is about three times higher than the population-weighted average of 84nGyh(-1), while the mean effective dose rate values except for PUM 05, PUM 06, PUM 10 and PUM 15 exceed the dose criterion of 1mSvy(-1).     

Radionuclides and metals in freshwater mussels of the upper South Alligator River, Australia

During an inspection of the old Rockhole Mine area in Kakadu National Park in 1999, it was found that a small amount of tailings from the former South Alligator uranium (U) mill had been uncovered by wet season rain and road works. Samples of sediment, water and freshwater mussels, Velesunio angasi, were collected from the South Alligator River, near and at the confluence of Rockhole Mine Creek, and adjacent to the exposed tailings. The 228Ra/226Ra activity ratios in sediments and mussel tissue indicate a small influence from the tailings and from Rockhole Mine adit water on 226Ra concentrations. The uptake of 226Ra in mussels does not correlate with other alkaline-earth metals. Mussel U concentrations are higher immediately downstream of Rockhole Mine Creek, but there is no noticeable increase in the immediate vicinity of the tailings area. A hypothetical ingestion of 2 kg of mussels from the sites was used to estimate the committed effective dose for a 10-year-old child resulting in a figure of 0.23 mSv per annum, of this total dose, 69% is attributed to 210Po. Only 0.03 mSv per annum can be directly linked to impacts of the tailings.