Correlations between potassium, rubidium and cesium ((133)Cs and (137)Cs) in sporocarps of Suillus variegatus in a Swedish boreal forest

An analysis of sporocarps of ectomycorrhizal fungi Suillus variegatus assessed whether cesium (¹³³Cs and ¹³⁷Cs) uptake was correlated with potassium (K) or rubidium (Rb) uptake. The question was whether intraspecific correlations of Rb, K and ¹³³Cs mass concentrations with ¹³⁷Cs activity concentrations in sporocarps were higher within, rather than among, different fungal species, and if genotypic origin of sporocarps within a population affected uptake and correlation. Sporocarps (n = 51) from a Swedish forest population affected by the fallout after the Chernobyl accident were studied. The concentrations were 31.9 ± 6.79 g kg⁻¹ for K (mean ± SD, dwt), 0.40 ± 0.09 g kg⁻¹ for Rb, 8.7 ± 4.36 mg kg⁻¹ for ¹³³Cs and 63.7 ± 24.2 kBq kg⁻¹ for ¹³⁷Cs. The mass concentrations of ¹³³Cs correlated with ¹³⁷Cs activity concentrations (r = 0.61). There was correlation between both ¹³³Cs concentrations (r = 0.75) and ¹³⁷Cs activity concentrations (r = 0.44) and Rb, but the ¹³⁷Cs/¹³³Cs isotopic ratio negatively correlated with Rb concentration. Concentrations of K and Rb were weakly correlated (r = 0.51). The ¹³³Cs mass concentrations, ¹³⁷Cs activity concentrations and ¹³⁷Cs/¹³³Cs isotopic ratios did not correlate with K concentrations. No differences between, within or, among genotypes in S. variegatus were found. This suggested the relationships between K, Rb, ¹³³Cs and ¹³⁷Cs in sporocarps of S. variegatus is similar to other fungal species.     

Cesium accumulation by fish following acute input to lakes: a comparison of experimental and Chernobyl-impacted systems

An uptake parameter u (L kg⁻¹ d⁻¹) and a loss rate parameter k (d⁻¹) were estimated for the patterns of accumulation and loss of ¹³³Cs by three fish species following an experimental ¹³³Cs addition into a pond in South Carolina, USA. These u and k parameters were compared to similar estimates for fish from other experimental ponds and from lakes that received ¹³⁷Cs deposition from Chernobyl. Estimates of u from ponds and lakes declined with increasing potassium concentrations in the water column. Although loss rates were greater in the experimental ponds, the times required to reach maximum Cs concentrations in fish were similar between ponds and lakes, because ponds and lakes had similar retentions of Cs in the water column. The maximum Cs concentrations in fish were largely determined by initial Cs concentrations in the water column. These maximum concentrations in fish and the times required to reach these maxima are potentially useful indicators for assessments of risks to humans from fish consumption.     

Sorption of selenate on soils and pure phases: kinetic parameters and stabilisation

This study was conducted to identify the principle selenate carrier phases for two selected soils, by comparing their reactivity with selenate to that of pure phases of the solids. Silica, calcium carbonate, aluminium hydroxide, goethite, bentonite and humic acid were selected as the main soil carrier phases. Comparisons were made first on the parameter values obtained with the best fit of a kinetic sorption model which can discriminate instantaneous sorption from kinetically limited sorption. Then comparisons were made of the ability for each solid to stabilise selenate by measuring the ratio of the partition coefficient for sorption (Kd_sorption) over that of the desorption (Kd_desorption). Kinetics and stabilisation were used to help elucidate the nature of interactions with the test solid phases for a large range of selenate concentrations. The experiments were conducted over 165 h in batch reactors, the solid being isolated from the solution by dialysis tubing, at two pH (5.4 and 8) and three selenate concentrations (1 × 10⁻³, 1 × 10⁻⁶ and 1 × 10⁻⁸ mol L⁻¹). The results obtained showed that only aluminium hydroxide can sorb selenate throughout the studied pH range (pH 5.4 to 8.0). The sorption capacity on this mineral was high (Kd_sorption > 100 to 1 × 10⁴ L kg⁻¹) and the selenate was mainly stabilized by the formation of inner sphere complexes. The sorption on goethite occurred at pH 5.4 (Kd_sorption 52 L kg⁻¹), mainly as outer sphere complexes, and was null at pH 8. On silica, a weak sorption was observed only at pH 5.4 and at 165 h (Kd_sorption 4 L kg⁻¹). On bentonite, calcium carbonate and humic acid no significant sorption was observed. Concerning the two soils studied, different behaviours were observed for selenate. For soil Ro (pH 5.4), Kd_sorption was low (8 L kg⁻¹) compared to soil Bu (pH 8) (70 L kg⁻¹). The sorption behaviour of selenate on soil Ro was mainly due to outer sphere complexes, as for goethite, whereas for soil Bu the sorption was mainly attributed to inner sphere complexes followed by reduction mechanisms, probably initiated by microorganisms, in which no steady state was reached at the end of the 165 h experiments. The sorption of selenate decreased when concentrations reached 1 × 10⁻³ mol L⁻¹, due to solid saturation, except for aluminium hydroxide. Reduction of selenate seemed also to occur on goethite and soil Ro, for the same concentration, but without preventing a decrease in sorption. Thus, this work shows that the comparison of selenate behaviour between soil and pure phases helps to elucidate the main carrier phases and sorption mechanisms in soil.     

Evaluation and assessment of 25 years of environmental radioactivity monitoring data at Tarapur (India) nuclear site

The evaluation and assessment of monitoring data generated over a period of 1983-2007 (25 years) of a nuclear facility is presented. Time trends of particulate radioactivity, correlation between ¹³⁷Cs in discharge canal seawater and station discharged activity and correlation of ¹³⁷Cs, ⁶⁰Co, and ¹³¹I in marine species such as sponge and Nerita (gastropod) and corresponding discharged activity are discussed. The concentration of ¹³⁷Cs and ¹³¹I in seawater versus biota are discussed. A good correlation between ¹³⁷Cs in seawater and ¹³⁷Cs in liquid waste discharged was observed (R² = 0.8, p < 0.001). Similarly, correlation was good for Nerita and discharged concentration of ¹³⁷Cs, ¹³¹I and ⁶⁰Co (R² = 0.55-0.73 and p < 0.001). The measurements over the years indicated that there is no accumulation of radionuclides in either the terrestrial or aquatic environments. The mean ¹³⁷Cs decreased from the pre-operational levels: 7.0-3.6 Bq kg⁻¹ in soil, 0.91-0.016 Bq L⁻¹ in milk and 0.28-0.036 Bq kg⁻¹ in vegetation. Similarly, the mean ⁹⁰Sr in these matrixes decreased from 3.9 to 0.26 Bq kg⁻¹; 0.37-0.011 Bq L⁻¹ and 0.34-0.022 Bq kg⁻¹ respectively. Cesium-137 of about 700 μBq m⁻³ was measured in the air filter disks during 1986 and there was a decrease of three orders of magnitude in concentration over the 25 years. The evaluation of environmental data indicated that the radionuclide concentrations and potential impacts, in terms of effective dose to the members of public, have significantly reduced since 1969.     

Radionuclides in marine mammals off the Portuguese coast

Radionuclide analyses were performed in tissue samples including muscle, gonad, liver, mammary gland, and bone of marine mammals stranded on the Portuguese west coast during January-July 2006. Tissues were collected from seven dolphins (Delphinus delphis and Stenella coeruleoalba) and one pilot whale (Globicephala sp.). Samples were analyzed for ²¹⁰Po and ²¹⁰Pb by alpha spectrometry and for ¹³⁷Cs and ⁴⁰K by gamma spectrometry. Po-210 concentrations in common dolphin’s muscle (D. delphis) averaged 56 ± 32 Bq kg⁻¹ wet weight (w.w.), while ²¹⁰Pb averaged 0.17 ± 0.07 Bq kg⁻¹ w.w., ¹³⁷Cs averaged 0.29 ± 0.28 Bq kg⁻¹ w.w., and ⁴⁰K 129 ± 48 Bq kg⁻¹ w.w. Absorbed radiation doses due to these radionuclides for the internal organs of common dolphins were computed and attained a 1.50 μGy h⁻¹ on a whole body basis. ²¹⁰Po was the main contributor to the weighted absorbed dose, accounting for 97% of the dose from internally accumulated radionuclides. These computed radiation doses in dolphins are compared to radiation doses from ²¹⁰Po and other radionuclides reported for human tissues. Due to the high ²¹⁰Po activity concentration in dolphins, the internal radiation dose in these marine mammals is about three orders of magnitude higher than in man.     

Ecological half-life of Cs in mosses and lichens in the Ordu province,Turkey by Cevik and Celik

Twenty-one years after the Chernobyl accident, lichen and moss samples were collected from the Ordu province, which was already chosen for a related study some years ago. It was observed that ¹³⁷Cs activity concentration ranged from 31 to 469 Bq kg⁻¹ in the moss and from 132 to 1508 Bq kg⁻¹ in the lichen samples. The decrease of the activity concentrations in the present measurements (2007) relative to those in 1997 (over a period of 10 y) indicated ecological half-lives between 1.8 and 10.4 y for the moss and between 2.1 and 13.7 y for the lichen samples. It was observed that ¹³⁷Cs was still eminent in the area studied. Moreover, ⁴⁰K activity concentrations and K element concentrations were measured and their relationships were discussed.     

Radiological maps for Trabzon, Turkey

The activity concentrations and absorbed gamma dose rates due to primordial radionuclides and ¹³⁷Cs have been ascertained in 222 soil samples in 18 counties of the Trabzon province of Turkey using a HPGe detector. The mean activity concentrations of ²³⁸U, ²³²Th, ⁴⁰K and ¹³⁷Cs in soil samples were 41, 35, 437 and 21 Bq kg⁻¹, respectively. Based on the measured concentrations of these radionuclides, the mean absorbed gamma dose in air was calculated as 59 nGy h⁻¹ and hence, the mean annual effective dose due to terrestrial gamma radiation was calculated as 72 μSv y⁻¹. In addition, outdoor in situ gamma dose rate (D) measurements were performed in the same 222 locations using a portable NaI detector and the annual effective dose was calculated to be 66 μSv y⁻¹ from these results. The results presented in this study are compared with other parts of Turkey. Radiological maps of the Trabzon province were composed using the results obtained from the study.     

Cesium and strontium sorption by selected tropical and subtropical soils around nuclear facilities

The dynamics of Cs and Sr sorption by soils, especially in the subtropics and tropics, as influenced by soil components are not fully understood. The rates and capacities of Cs and Sr sorption by selected subtropical and tropical soils in Taiwan were investigated to facilitate our understanding of the transformation and dynamics of Cs and Sr in soils developed under highly weathering intensity. The Langmuir isotherms and kinetic rates of Cs and Sr sorption on the Ap1 and Bt1 horizons of the Long-Tan (Lt) and the A and Bt1 horizons of the Kuan-Shan (Kt), Mao-Lin (Tml) and Chi-Lo (Cl) soils were selected for this study. Air-dried soil (<2 mm) samples were reacted with of 7.5 × 10⁻⁵ to 1.88 × 10⁻³ M of CsCl (pH 4.0) or 1.14 × 10⁻⁴ to 2.85 × 10⁻³ M of SrCl₂ (pH 4.0) solutions at 25 °C. The sorption maximum capacity (q_m) of Cs by the Ap1 and Bt1 horizons of the Lt soil (62.24 and 70.70 mmol Cs kg⁻¹ soil) were significantly (p < 0.05) higher than those by the A and Bt1 horizons of the Kt and Cl soils (26.46 and 27.49 mmol Cs kg⁻¹ soil in Kt soil and 34.83 and 29.96 mmol Cs kg⁻¹ soil in Cl soil, respectively), however, the sorption maximum capacity values of the Lt and Tml soils did not show significant differences. The amounts of pyrophosphate extractable Fe (Fe_p) were correlated significantly with the Cs and Sr sorption capacities (for Cs sorption, r² = 0.97, p < 1.0 × 10⁻⁴; for Sr sorption, r² = 0.82, p < 2.0 × 10⁻³). The partition coefficient of radiocesium sorbed on soil showed the following order: Cl soil ? Kt soil > Tml soil > Lt soil. It was due to clay minerals. The second-order kinetic model was applied to the Cs and Sr sorption data. The rate constant of Cs or Sr sorption on the four soils was substantiality increased with increasing temperature. This is attributable to the availability of more energy for bond breaking and bond formation brought about by the higher temperatures. The rate constant of Cs sorption at 308 K was 1.39-2.09 times higher than that at 278 K in the four soils. The activation energy of Cs and Sr sorbed by the four soils ranged from 7.2 to 16.7 kJ mol⁻¹ and from 15.2 to 22.4 kJ mol⁻¹, respectively. Therefore, the limiting step of the Cs⁺ or Sr²⁺ sorption on the soils was diffusion-controlled processes. The reactive components, which are significantly correlated with the Langmuir sorption maxima of Cs and Sr by these soils, substantially influenced their kinetic rates of Cs and Sr sorption. The data indicate that among components of the subtropical and tropical soils studied, short-range ordered sesquioxides especially Al- and Fe-oxides complexed with organics play important roles in influencing their capacity and dynamics of Cs and Sr sorption.     

Radioactivity measurements in moss (Hypnum cupressiforme) and lichen (Cladonia rangiformis) samples collected from Marmara region of Turkey

The present study was conducted to compare the ¹³⁷Cs, ⁴⁰K, ²³²Th, and ²³⁸U activity concentrations in epigeic moss (Hypnum cupressiforme) and lichen (Cladonia rangiformis). The activity levels in 37 moss and 38 lichen samples collected from the Marmara region of Turkey were measured using a gamma spectrometer equipped with a high purity germanium (HPGe) detector. The activity concentrations of ¹³⁷Cs, ⁴⁰K, ²³²Th, and ²³⁸U in the moss samples were found to be in the range of 0.36-8.13, 17.1-181.1, 1.51-6.17, and 0.87-6.70 Bq kg⁻¹ respectively, while these values were below detection limit (BDL)-4.32, 16.6-240.0, 1.32-6.47, and BDL-3.57 Bq kg⁻¹ respectively in lichen. The average moss/lichen activity ratios of ¹³⁷Cs, ⁴⁰K, ²³²Th, and ²³⁸U were found to be 1.32 ± 0.57, 2.79 ± 1.67, 2.11 ± 0.82, and 2.19 ± 1.02, respectively. Very low ¹³⁷Cs concentrations were observed in moss and lichen samples compared to soil samples collected from the same locations in a previous study. Seasonal variations of the measured radionuclide activities were also examined in the three sampling stations.     

Time-dependency of the Cs contamination of wild boar from a region in Southern Germany in the years 1998 to 2008

Following the Chernobyl accident, ¹³⁷Cs contamination levels of wild boar in some districts of Southern Germany are still exceeding thousands of Bq kg⁻¹. While the long term ¹³⁷Cs concentration in forest plants, mushrooms, and roe deer meat has decreased significantly, for wild boar it has remained constant during the last decade. Between 1998 and 2008, we analysed the muscle meat of 656 wild boars shot in the district (“Landkreis”) Ravensburg. The ¹³⁷Cs activity concentration showed considerable variability from less than 5 up to 8266 Bq kg⁻¹ and it followed a seasonal pattern, which is attributed to changes in dietary habits, fodder availability, meteorological conditions and specific behaviour of ¹³⁷Cs in wild boar organism. T_ag values for wild boars from the district Ravensburg varied from 0.008 to 0.062 m² kg⁻¹ during 2000–2008.     

Transfer parameter values in temperate forest ecosystems: a review

Compared to agricultural lands, forests are complex ecosystems as they can involve diverse plant species associations, several vegetative strata (overstorey, shrubs, herbaceous and other annual plant layer) and multi-layered soil profiles (forest floor, hemi-organic and mineral layers). A high degree of variability is thus generally observed in radionuclide transfers and redistribution patterns in contaminated forests. In the long term, the soil compartment represents the major reservoir of radionuclides which can give rise to long-term plant and hence food contamination. For practical reasons, the contamination of various specific forest products has commonly been quantified using the aggregated transfer factor (T_ag in m² kg⁻¹) which integrates various environmental parameters including soil and plant type, root distribution as well as nature and vertical distribution of the deposits. Long lasting availability of some radionuclides was shown to be the source of much higher transfer in forest ecosystems than in agricultural lands. This study aimed at reviewing the most relevant quantitative information on radionuclide transfers to forest biota including trees, understorey vegetation, mushrooms, berries and game animals. For both radiocaesium and radiostrontium in trees, the order of magnitude of mean T_ag values was 10⁻³ m² kg⁻¹ (dry weight). Tree foliage was usually 2–12 times more contaminated than trunk wood. Maximum contamination of tree components with radiocaesium was associated with (semi-)hydromorphic areas with thick humus layers. The transfer of radionuclides to mushrooms and berries is high, in comparison with foodstuffs grown in agricultural systems. Concerning caesium uptake by mushrooms, the transfer is characterized by a very large variability of T_ag, from 10⁻³ to 10¹ m² kg⁻¹ (dry weight). For berries, typical values are around 0.01–0.1 m² kg⁻¹ (dry weight). Transfer of radioactive caesium to game animals and reindeer and the rate of activity reduction, quantified as an ecological half-life, reflect the soil and pasture conditions at individual locations. Forests in temperate and boreal regions differ with respect to soil type and vegetation, and a faster decline of muscle activity concentrations in deer occurs in the temperate zone. However, in wild boar the caesium activity concentration shows no decline because of its special feeding habits. In the late phase, i.e. at least a few months since the external radionuclide contamination on feed plants has been removed, a T_ag value of 0.01 m² kg⁻¹ (fresh weight) is common for ¹³⁷Cs in the muscles of adult moose and terrestrial birds living in boreal forests, and 0.03 m² kg⁻¹ (fresh weight) for arctic hare. Radiocaesium concentrations in reindeer muscle in winter may exceed the summer content by a factor of more than two, the mean T_ag values for winter ranging from 0.02 to 0.8 m² kg⁻¹ (fresh weight), and in summer from 0.04 to 0.4 m² kg⁻¹. The highest values are found in the year of initial contamination, followed by a gradual reduction. In waterfowl a relatively fast decline in uptake of ¹³⁷Cs has been found, with T_ag values changing from 0.01 to 0.002 m² kg⁻¹ (fresh weight) in the three years after the contaminating event, the rate being determined by the dynamics of ¹³⁷Cs in aquatic ecosystems.     

Contrasting cesium dynamics in neighboring deep and shallow warm-water reservoirs

To measure the long term retention and seasonal dynamics of an initial 4 kg addition of ¹³³Cs into an 11.4-ha, 157,000 m³ reservoir (Pond 4, near Aiken, South Carolina, USA), the concentrations and inventories of ¹³³Cs in the water column were measured at periodical intervals for 522 days following the 1 August, 1999 release. After rapid declines in concentrations and inventories during the first 90 days, the ¹³³Cs concentrations in the water column declined at an average proportional rate of 0.004 d⁻¹. However, there were periods of less rapid and more rapid rates of declines, and these were correlated with periods of increasing and decreasing K concentrations in the water column. The decline rates were less and the K concentrations greater in the winter than in the summer. In the deeper, neighboring monomictic reservoirs of Par Pond and Pond B, a yearly cycle of increasing and decreasing ¹³⁷Cs concentrations in the water column is driven by anoxic remobilization of Cs from the sediments into a persistent summer hypolimnion. In Pond 4, whose mean depth of 1.6 m is too shallow to support a persistent anoxic hypolimnion, the pattern of yearly dynamics for K and Cs appear to be related to the accumulation and release of these elements from the extensive, seasonal macrophyte communities. The contrasting results between Pond 4 and Pond B suggest that a full appreciation of the relative importance of 1) anoxic remobilization and 2) accumulation and release by macrophytes in these systems remains to be established.     

Natural radioactivity levels in topsoil from the Pearl River Delta Zone, Guangdong, China

Concentrations of the natural radionuclides ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K have been measured by γ-ray spectrometry in 796 topsoil samples from the Pearl River Delta Zone (PRDZ) of Guangdong, China. The mean concentrations for ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K were found to be 140 ± 37 Bq kg⁻¹, 134 ± 41 Bq kg⁻¹, 187 ± 80 Bq kg⁻¹ and 680 ± 203 Bq kg⁻¹ dry mass, respectively. These values were all higher than the mean values in soil for China and the world. Outdoor air-absorbed dose rates, calculated from activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K, ranged from 86 to 237 nGy h⁻¹, with a mean value of 165 ± 46 nGy h⁻¹. The corresponding annual outdoor effective dose rate per person was estimated to be between 0.11 and 0.29 mSv y⁻¹, with a mean value of 0.20 ± 0.06 mSv y⁻¹, which was also higher than the world mean value of 0.07 mSv y⁻¹. The radium equivalent activity (Ra_eq) and the external hazard index (I_r) resulted from the natural radionuclides in soil, were also calculated and found to vary from 230 to 676 Bq kg⁻¹ and from 0.6 to 1.8, respectively. The Ra_eq and the I_r in all the investigated regions were up to 75% higher than the set limits of 370 Bq kg⁻¹ and 1.0, respectively.     

Natural radionuclide concentrations in two phosphate ores of east Algeria

Ore is considered as an important source of many elements such as the iron, phosphorus, and uranium. Concerning the natural radionuclides, their concentrations vary from an ore to other depending on the chemical composition of each site.In this work, two phosphate ores found in East of Algeria have been chosen to assess the activity concentration of natural radionuclides represented mainly by three natural radioactive series ²³⁸U, ²³⁵U and ²³²Th, and the primordial radionuclide ⁴⁰K where they were determined using ultra-low background, high-resolution gamma-ray spectroscopy.The measured activity concentrations of radioactive series ranged from 6.2 ± 0.4 to 733 ± 33 Bq.kg⁻¹ for the ²³²Th series, from 249 ± 16 to 547 ± 39 Bq.kg⁻¹ for the ²³⁸U series, around 24.2 ± 2.5 Bq.kg⁻¹ for the ²³⁵U series, and from 1.4 ± 0.2 to 6.7 ± 0.7 Bq.kg⁻¹ for ⁴⁰K.To assess exposure to gamma radiation in the two ores, from specific activities of ²³²Th, ⁴⁰K and ²²⁶Ra, three indexes were determined: Radium equivalent (Ra_eq), external and internal hazard indexes (H_ex and H_in), their values ranged from 831 ± 8 to 1298 ± 14 Bq.kg⁻¹ for Ra_eq, from 2.2 ± 0.4 to 3.5 ± 0.7 Bq.kg⁻¹ for H_ex, and from 4.2 ± 0.7 to 4.5 ± 0.7 Bq.kg⁻¹ for H_in.     

Temporal changes of 7Be, 137Cs and 210Pb activity concentrations in surface air at Monaco and their correlation with meteorological parameters

Results of analysis of ⁷Be, ¹³⁷Cs and ²¹⁰Pb on aerosol filters carried out from 1998 to 2010 in Monaco show that a weak correlation between activity concentrations of these radionuclides in the atmosphere and meteorological parameters has been found for ⁷Be and temperature (r = 0.50), ²¹⁰Pb and temperature and humidity (r = 0.43 and 0.41, respectively), and ¹³⁷Cs and precipitation (r = 0.51). The minimum and maximum ⁷Be activity concentrations were observed during 2000 and 2009, corresponding with the maximum and minimum solar activity, respectively. The maximum ¹³⁷Cs activity concentration found in May-June 1998 was due to the accident at Algeciras in Spain. The deposition velocities of ⁷Be, ¹³⁷Cs and ²¹⁰Pb depended on the precipitation rate, and attained maximum values during dry seasons. The investigated radionuclides may be used as atmospheric tracers, especially in long-term periods.     

Seasonal and inter-annual variation of Beryllium-7 deposition in birch-tree leaves and grass in the northeast upland area of the Czech Republic

The activity concentrations of Beryllium-7 (⁷Be), a naturally occurring radioisotope produced in the atmosphere, were measured in leaves of birch-trees, above-ground parts of grass, soil and rainwater in the mountain massive Kralicky Sneznik (the northeast of the Czech Republic, altitude about 750 m) in the years of 2005, 2006 and 2007. Dried and ground samples of the plants and soils, and water samples from wet deposition were used to determine the ⁷Be content using a semiconductor gamma spectrometer. The ⁷Be values ranged from 147.0 to 279.6 Bq kg⁻¹, from 48.7 to 740.8 Bq kg⁻¹, from 2.1 to 8.7 Bq kg⁻¹, and from 0.6 to 1.9 Bq kg⁻¹ in birch-tree leaves, grass samples, soils, and rainwater, respectively. Insignificant inter-annual variations but significant increase in the ⁷Be activity concentrations during the spring and summer months were observed in birch-tree leaves and grass samples. The seasonal variation of the ⁷Be concentrations in grass samples correlated (R² = 0.4663 and 0.6489) with precipitation. No similar correlation was found for ⁷Be in birch-tree leaves. Beryllium-7 content in birch-tree leaves and in aerial parts of grass was mainly caused by direct transport of ⁷Be from wet deposition into aerial parts of the observed plants.     

Natural and artificial radioactivity determination of some medicinal plants

Several medicinal plants used in Italy were analysed to determine natural and artificial radioactivity in those parts (leaves, fruits, seeds, roots, peduncles, flowers, barks, berries, thallus) used generally as remedies. The radionuclides were determined by alpha (²³⁸U, ²¹⁰Po) and gamma (²¹⁴Pb-Bi, ²¹⁰Pb, ⁴⁰K and ¹³⁷Cs) spectrometry. ²³⁸U ranged between <0.1 and 7.32 Bq kg_dry⁻¹; ²¹⁰Po between <0.1 and 30.3 Bq kg_dry⁻¹; ²¹⁴Pb-²¹⁴Bi between <0.3 and 16.6 Bq kg_dry⁻¹; ²¹⁰Pb between <3 and 58.3 Bq kg_dry⁻¹; ⁴⁰K between 66.2 and 3582.0 Bq kg_dry⁻¹; ¹³⁷Cs between <0.3 and 10.7 Bq kg_dry⁻¹. The percentage of ²¹⁰Po extraction in infusion and decoction was also determined; the arithmetical mean value of percentage of ²¹⁰Po extraction resulted 20.7 ± 7.5.     

Bioaccumulation of Ra by plants growing in fresh water ecosystem around the uranium industry at Jaduguda, India

A field study has been conducted to evaluate the ²²⁶Ra bioaccumulation among aquatic plants growing in the stream/river adjoining the uranium mining and ore-processing complex at Jaduguda, India. Two types of plant group have been investigated namely free floating algal species submerged into water and plants rooted in stream & riverbed. The highest ²²⁶Ra activity concentration (9850 Bq kg⁻¹) was found in filamentous algae growing in the residual water of tailings pond. The concentration ratios of ²²⁶Ra in filamentous algae (activity concentration of ²²⁶Ra in plant Bq kg⁻¹ fresh weight/activity concentration of ²²⁶Ra in water Bq l⁻¹) widely varied i.e. from 1.1 × 10³ to 8.6 × 10⁴. Other aquatic plants were also showing wide variability in the ²²⁶Ra activity concentration. The ln-transformed filamentous algae ²²⁶Ra activity concentration was significantly correlated with that of ln-transformed water concentration (r = 0.89, p < 0.001). There was no correlation between the activity concentrations of ²²⁶Ra in stream/riverbed rooted plants and the substrate. For this group, correlation between ²²⁶Ra activity concentration and Mn, Fe, Cu concentration in plants were statistically significant.     

Cs in a raised bog in central Sweden

The vertical distribution of ¹³⁷Cs activity in peat soil profiles and ¹³⁷Cs activity concentration in plants of various species was studied in samples collected at two sites on a raised bog in central Sweden. One site (open bog) was in an area with no trees and only a few sparsely growing plant species, while the other (low pine) was less than 100 m from the open bog site and had slowly growing Scots pine, a field layer dominated by some ericaceous plants and ground well-covered by plants. The plant samples were collected in 2004–2007 and were compared with samples collected in 1989 from the same open bog and low pine sites. Ground deposition of ¹³⁷Cs in 2005 was similar at both sites, 23?000 Bq m⁻². In the open bog peat profile it seems to be an upward transport of caesium since a clear peak of ¹³⁷Cs activity was found in the uppermost 1–4 cm of Sphagnum layers, whereas at the low pine site ¹³⁷Cs was mainly found in deeper (10–12 cm) layers. The migration rate was 0.57 cm yr⁻¹ at the open bog site and the migration centre of ¹³⁷Cs was at a depth of 10.7, while the rate at the low pine site was 0.78 cm yr⁻¹ and the migration centre was at 14.9 cm. Heather (Calluna vulgaris) was the plant species with the highest ¹³⁷Cs activity concentrations at both sites, 43.5 k Bq⁻¹ DM in 1989 decreasing to 20.4 in 2004–2007 on open bog and 22.3 k Bq kg⁻¹ DM in 1989 decreasing to 11.2 k Bq⁻¹ DM by the period 2004–2007 on the low pine site. ¹³⁷Cs transfer factors in plants varied between 0.88 and 1.35 on the open bog and between 0.48 and 0.69 m² kg⁻¹ DM at the low pine site.     

Analytical results and effective dose estimation of the operational Environmental Monitoring Program for the radioactive waste repository in Abadia de Goiás from 1998 to 2008

This paper presents the results of the Environmental Monitoring Program for the Radioactive waste repository of Abadia de Goiás, which was originated from the accident of Goiania, conducted by the Regional Center of Nuclear Sciences (CRCN-CO) of the National Commission on Nuclear Energy (CNEN), from 1998 to 2008.The results are related to the determination of ¹³⁷Cs activity per unit of mass or volume of samples from surface water, ground water, depth sediments of the river, soil and vegetation, and also the air-kerma rate estimation for gamma exposure in the monitored site.In the phase of operational Environmental Monitoring Program, the values of the geometric mean and standard deviation obtained for ¹³⁷Cs activity per unit of mass or volume in the analyzed samples were (0.08 ± 1.16) Bq.L⁻¹ for surface and underground water, (0.22 ± 2.79) Bq.kg⁻¹ for soil, and (0.19 ± 2.72) Bq.kg⁻¹ for sediment, and (0.19 ± 2.30) Bq.kg⁻¹ for vegetation. These results were similar to the values of the pre-operational Environmental Monitoring Program.With these data, estimations for effective dose were evaluated for public individuals in the neighborhood of the waste repository, considering the main possible way of exposure of this population group.The annual effective dose obtained from the analysis of these results were lower than 0.3 mSv.y⁻¹, which is the limit established by CNEN for environmental impact in the public individuals indicating that the facility is operating safely, without any radiological impact to the surrounding environment.