The presence of some artificial and natural radionuclides in a Eucalyptus forest in the south of Spain

Long-lived artificial radionuclides (137Cs, 90Sr) were studied in a Eucalyptus plantation located in the south-west of Spain. Radionuclide concentrations were determined in different types of samples corresponding to specific forest components (soil, trees, herbs and litter). Depth profile distributions were obtained in two selected core soils. Two layers were separately measured in three other cores. The concentration factor, defined as the ratio between the mean activity concentration in a component and the mean activity concentration in the soil, was calculated for each component. The biomass of different components was estimated in order to evaluate the total density concentration (Bq/ha) of the artificial radionuclides (137Cs, 90Sr) in the Eucalyptus plantation. The transfer of the radionuclides between the different forest components can be inferred from the results. Additionally, other naturally occurring radionuclides (40K, 226Ra, 228Ra, 228Ac) were determined for comparison. Transport of radionuclides from forest to a nearby pulp mill is also discussed.     

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.     

Natural radionuclides and (137)Cs distributions and their relationship with sedimentological processes in Patras Harbour, Greece

Surficial and subsurficial sediment samples derived from gravity cores, selected from the harbour of Patras, Greece, were analyzed for grain size, water content, bulk density, specific gravity, organic carbon content and specific activities of natural radionuclides and (137)Cs. The specific activities of (232)Th, (226)Ra, (40)K and (137)Cs were measured radiometrically. The radionuclides (238)U and (232)Th were also analyzed using the INAA. The differences found between the specific activities of the natural radionuclides measured by the two methods are of no statistical significance. The sediment cores selection was based on a detailed bathymetric and marine seismic survey. Through the study of the detailed bathymetric map and the seismic profiles it was shown that ship traffic is highly influential to the harbour bathymetry. The granulometric and geotechnical properties of the sediments and therefore the specific activities of the natural radionuclides and (137)Cs seem to be controlled by the ship traffic. Relationship between radionuclide activity concentrations and granulometric/geotechnical parameters was defined after the treatment of all the analyses using R-mode factor analysis. The natural radionuclide activities are related to the fine fraction and bulk density of the sediments, while (137)Cs is mainly influenced by the organic carbon content. In addition, (238)U and (226)Ra seem to be in close relation with the heavy minerals fraction in coarse-grained sediments with high specific gravity.     

Seasonal variations in radionuclide transfer in a Mediterranean grazing-land ecosystem.

We made quarterly determinations of the transfer coefficients and effective transfer coefficients for the radionuclides 137Cs, 90Sr, 40K, 226Ra, 228Ra and 228Th over a full annual cycle, in a Mediterranean grazing-land ecosystem. The input and output fluxes of the radionuclides between the different compartments of this ecosystem were quantified for the following processes: root uptake; variation in root and aerial biomass; pasture production; translocation; leaf fall; efflux due to grazing action; resuspension and subsequent aerial deposition of radionuclides. We observed there to be a marked seasonal variation for this type of ecosystem in both the transfer coefficients and the radionuclide fluxes, which impedes the soil-plant transfer being characterized on the basis of values that are constant with time.     

Distribution of gamma-ray emitting radionuclides in the environment of Burullus Lake: I. Soils and vegetations

The concentrations and distribution of gamma-ray emitting isotopes in Burullus Lake were investigated with the aim of evaluating the environmental radioactivity. Particularly in wetlands, natural properties of the environment can cause the actual inventory to be different from the activity originally deposited. The mean concentrations of (226)Ra, (232)Th and (40)K were 14.3, 15.5 and 224 Bq/kg, respectively, in the coastal soils. On the other hand, soil samples from the islands had mean concentrations of 13.5, 17.4 and 341 Bq/kg for (226)Ra, (232)Th and (40)K, respectively. Samples from coast and islands show evidence of possible transfer and accumulation of the (137)Cs radionuclide. The mean (137)Cs activity concentrations in the soil samples were 1.2 and 15.1 Bq/kg in the coast and islands, respectively. The vertical migration of (137)Cs was studied based on its content in the consequently located three soil layers down to 30 cm depth. The radium equivalent, dose rate in air and annual dose equivalent from the terrestrial natural gamma-radiation were evaluated. The mean activity concentrations of the gamma-ray emitting radionuclides in vegetation were relatively low.     

Significant radioactive contamination of soil around a coal-fired thermal power plant

Soil samples were collected around a coal-fired power plant from 81 different locations. Brown coal, unusually rich in uranium, is burnt in this plant that lies inside the confines of a small industrial town and has been operational since 1943. Activity concentrations of the radionuclides 238U, 226Ra, 232Th, 137Cs and 40K were determined in the samples. Considerably elevated concentrations of 238U and 226Ra have been found in most samples collected within the inhabited area. Concentrations of 235U and 226Ra in soil decreased regularly with increasing depth at many locations, which can be explained by fly-ash fallout. Concentrations of 235U and 226Ra in the top (0-5 cm depth) layer of soil in public areas inside the town are 4.7 times higher, on average, than those in the uncontaminated deeper layers, which means there is about 108 Bq kg(-1) surplus activity concentration above the geological background. A high emanation rate of 222Rn from the contaminated soil layers and significant disequilibrium between 238U and 226Ra activities in some kinds of samples have been found.     

Natural radioactivity in winter wheat from organic and conventional agricultural systems

The distribution of natural radionuclides was studied in winter wheat plants collected from three sites in Belgium during 2004-2007. Activity concentrations of ⁴⁰K, ²²⁶Ra, ²²⁸Ra and ²²⁸Th in organically and conventionally grown wheat, and in the corresponding soil samples, were determined using ultra low-level gamma-ray spectrometry. The observed soil-to-wheat concentration ratios were calculated for the different parts of the wheat plant (root, stem and grain) in the two agricultural systems (organic and conventional). There were large variations in radionuclide activity concentrations between the sites and fields, but no significant difference between conventionally and organically grown wheat plants was observed.     

Soil to leaf transfer factor for the radionuclides ²²⁶Ra, ⁴⁰K, ¹³⁷Cs and ⁹⁰Sr at Kaiga region, India

Transfer factors are the most important parameters required for mathematical modeling used for environmental impact assessment of radioactive contamination in the environment. In this paper soil to leaf transfer factor for the radionuclides ⁴⁰K, ²²⁶Ra, ¹³⁷Cs and ⁹⁰Sr is estimated for Kaiga region in Karnataka state, India. Among the plants in which study is carried out, ²²⁶Ra, ⁴⁰K, ¹³⁷Cs and ⁹⁰Sr activity in leaves of herbaceous plants is higher than that of tree leaves. Soil to leaf transfer factor for ²²⁶Ra, ⁴⁰K, ¹³⁷Cs and ⁹⁰Sr was found to be in the range of 0.03-0.65, 0.32-8.04, 0.05-3.03 and 0.42-2.67 respectively.     

Classification of soil samples according to their geographic origin using gamma-ray spectrometry and principal component analysis

A principal component analysis (PCA) was used for classification of soil samples from different locations in Serbia and Montenegro. Based on activities of radionuclides ((226)Ra, (238)U, (235)U, (40)K, (134)Cs, (137)Cs, (232)Th and (7)Be) detected by gamma-ray spectrometry, the classification of soils according to their geographical origin was performed. Application of PCA to our experimental data resulted in satisfactory classification rate (86.0% correctly classified samples). The obtained results indicate that gamma-ray spectrometry in conjunction with PCA is a viable tool for soil classification.     

Quantification of transfer of U, Ra, Th, K and Cs in mosses of a semi-natural ecosystem

There is a lack of appropriate data on transfer of some radionuclides on many terrestrial biota groups. To expand the available data concentration ratios of ²³⁸U, ²²⁶Ra, ²³²Th, ⁴⁰K and ¹³⁷Cs in mosses are presented in this paper. The relationship between concentration ratios of radionuclides and physicochemical characteristics of the underlying soil was also investigated. The data on concentration ratios obtained here will provide a useful addition to the currently used database of transfer parameters, particularly for natural radionuclides.     

Radioactivity in tobacco leaves

The radioactivity in tobacco leaves collected from 15 different regions of Greece before cigarette production was studied in order to find any association between the uptake of the naturally occurring radionuclides and the isotopes of cesium of Chernobyl origin. The activities of the isotopes of radium, 226Ra and 228Ra, in the tobacco leaves reflected their origin from the soil by root uptake rather than from fertilizers used in the tobacco cultivation. Lead-210 originated from the air and was deposited onto the tobacco leaves and trapped by the trichomes. Potassium-40 in the tobacco leaves was due to root uptake either from soil or from fertilizer. The isotopes of cesium, 137Cs and 134Cs, in the tobacco leaves were due to root uptake and not due to deposition onto the leaf foliage as they still remained in soil four years after the Chernobyl reactor accident but were absent from the atmosphere in rain washout (precipitation) and gravitational settling.     

Comparative analysis of (239)Pu, (137)Cs, (210)Pb and (40)K spatial distributions in the top soil layer at the Baltic coast

This paper presents the results of an investigation into the spatial distribution of radionuclides of artificial ((239,240)Pu, (137)Cs) and natural ((210)Pb, (40)K) origins in the upper (0-5 cm) soil layers on the Baltic coastline of Lithuania ( approximately 5 km(2) area). The samples were analysed by gamma ray spectrometry and combined radiochemical procedures. The highest (210)Pb, (239,240)Pu and (137)Cs activity concentrations were determined in the forest samples, whereas (40)K activity was rather homogeneous across the study area. Relatively high (239,240)Pu and (40)K activity concentrations were determined along the surf zone. The (210)Pb and (137)Cs activity concentrations showed a gradual increase from the surf zone to the forest. The average activity concentrations of (239,240)Pu, (137)Cs, (210)Pb and (40)K in the beach and forest samples, respectively, were as follows: 0.32+/-0.08 and 0.74+/-0.14; 50+/-4 and 1190+/-50; 4.7+/-2.0 and 48+/-6; 186+/-15 and 216+/-17 Bq/kg.     

Biomagnification of 7Be, 234Th, and 228Ra in marine organisms near the northern Pacific coast of Japan

Enrichment of natural radionuclides of thorium, radium and beryllium in several kinds of marine organisms was investigated near the Pacific coast of Miyagi Pref., Japan. The radioactivity of 7Be, 210Pb, 234Th, 238U, 228Ra and 137Cs was measured using gamma spectrometry. High concentrations of 234Th were observed in ascidian livers (50-400 Bq/kg dry) and excrement (2000-2900 Bq/kg dry), although the parent 238U concentrations were less than 3 Bq/kg dry. Such extreme disequilibrium between 238U and 234Th activity was observed in other organisms (barnacles, mussels and brown algae). Relatively high concentrations of 228Ra were detected in ascidian livers and were observed to decrease according to its half-life (5.75 year), suggesting disequilibrium with its parent 232Th. High concentrations (about 1900-5000 Bq/kg dry) of 7Be were detected in ascidian liver. Possible mechanisms for the observed biomagnification and bioaccumulation of these radionuclides in the organisms analyzed were proposed.     

Relationships between sea-bed radionuclide activities and some sedimentological variables

Natural radionuclides (232Th, 226Ra, 40K) and 137Cs, coming from atmospheric radioactive fallout, have been measured in sea-bed sediments of the Bay of Cádiz (South Western Spain). In this report, multivariate analysis methods have been employed to study the relationships between the activities of the radionuclides and some sedimentological variables like granulometric facies, organic content and apparent density. The correlation functions found show that it is possible to determine, with a satisfactory degree of approximation, the granulometric facies of the sediments using only radiometric information.     

Natural radioactivity, dose assessment and uranium uptake by agricultural crops at Khan Al-Zabeeb, Jordan

Khan Al-Zabeeb, an irrigated cultivated area lies above a superficial uranium deposits, is regularly used to produce vegetables and fruits consumed by the public. Both soil and plant samples collected from the study area were investigated for their natural radioactivity to determine the uranium uptake by crops and hence to estimate the effective dose equivalent to human consumption. Concentrations of (238)U, (235)U, (232)Th, (226)Ra, (222)Rn, (137)Cs and (40)K in nine soil profiles were measured by gamma-ray spectrometry whereas watermelon and zucchini crops were analyzed for their uranium content by means of alpha spectrometry after radiochemical separation. Correlations between measured radionuclides were made and their activity ratios were determined to evaluate their geochemical behavior in the soil profiles. Calculated soil-plant transfer factors indicate that the green parts (leaves, stems and roots) of the studied crops tend to accumulate uranium about two orders of magnitude higher than the fruits. The maximum dose from ingestion of 1 kg of watermelon pulp was estimated to be 3.1 and 4.7 nSv y(-1) for (238)U and (234)U, respectively. Estimations of the annual effective dose equivalent due to external exposure showed extremely low values. Radium equivalent activity and external hazard index were seen to exceed the permissible limits of 370 Bq kg(-1) and 1, respectively.     

Assessment of natural and anthropogenic radioactivity levels in rocks and soils in the environs of Swieradow Zdroj in Sudetes, Poland, by in situ gamma-ray spectrometry

The natural radioactivity of 40K, 208Ti, 212Pb, 214Pb, 228Ac, and the fallout of 137Cs in typical rocks and soils of Swieradów Zdrój area (Sudetes Mountains, Poland) were measured in situ using a portable gamma-ray spectrometry workstation. The measurement points were chosen for different regional lithology: within hornfelses of the Szklarska Poreba schist-belt, quartz rocks, gneisses of the Swieradów Zdrój unit, leucogranites, leptinites, mica schists of the Stara Kamienica belt, and finally the zones of the southern and northern contacts of the Stara Kamienica schist-belt with leucogranites and gneisses of the Lesna unit, respectively. 40K activity varied in the range from about 320 Bq kg(-1) (quartz) to 1200 Bq kg(-1) (gneisses). The activity concentrations associated with 228Ac (232Th series) varied in the range from 25 Bq kg(-1) (quartz) to 62 Bq kg(-1) (leucogranites), whereas activity concentration of 226Ra varied in the range from about 31 Bq kg(-1) (hornfelses) to 122 Bq kg(-1) (leucogranites). Relatively low deposits of 137Cs were noted in the investigated area, where the activity concentrations ranged from 4001 (hornfelses) Bq m(-2) to less than 154 Bq m(-2) (leucogranites).     

The derivation of radionuclide transfer parameters for and dose-rates to an adult ringed seal (Phoca hispida) in an Arctic environment

Radionuclide transfer parameters and dose-rates for an adult ringed seal from Svalbard have been determined based on empirical and estimated tissue activity concentrations and detailed dietary and habitat information. Whole-body equivalent concentration factors determined for anthropogenic radionuclides ranged from 10(1) ((90)Sr) to 10(2) ((137)Cs, (238)Pu and (239,240)Pu), while natural radionuclides ranged from 10(2) ((210)Pb) to 10(4) ((210)Po). Employing a dietary composition of 40% fish, 40% zooplankton and 20% benthic invertebrates, a whole-body biological half-life of 29 days was derived for (137)Cs. A total dose-rate of approximately 0.19microGyh(-1) (1.7mGya(-1)) was derived for an adult ringed seal; this dose-rate is virtually entirely attributable to the internal components of (210)Po and (40)K. The dose-rates associated with the presence of anthropogenically derived radionuclides in the present assessment fall many orders of magnitude below the dose-rates at which any biological effects would be expected.     

Aerial measurements on uranium ore mining, milling and processing areas in Germany

The paper describes aerial measurements at several sites containing residues from uranium mines, waste rock dumps and tailings ponds of the Wismut company in Saxony and Thuringia. For the measurements, a computerized gamma-ray spectrometer equipped with a HPGe-detector and a NaI(Tl)-detector array with a volume of 121 was used. Radioactive anomalies from natural radionuclides have been detected and mapped. The activity concentrations of 226Ra, 228Th and 40K in areas with elevated radioactivity from natural radionuclides were determined from aerial measurements. Ground-based measurements--as far as available--confirmed these results. The mean 226Ra activity concentrations in the different waste rock dumps were found to be in the range 370 to 1600 Bq kg-1. The highest mean 226Ra activity concentrations were measured for the tailings ponds with values up to 1300 Bq kg-1. For 40K and 208Tl, activity concentrations of 860 and 40 Bq kg-1, respectively, were obtained as averages of all measurements. These values are commonly found in the environment. In general, there is reasonable agreement between the results measured with different detectors and measuring methods.     

Radioactivity concentrations of 40K, 134Cs, 137Cs, 90Sr, 241Am, 238Pu and 239+240Pu radionuclides in Jordanian soil samples

In November 2000, surface and core soil samples were collected from different regions of Jordan. The samples were analyzed by direct gamma spectrometry and combined radiochemical separation procedure to quantify (40)K, (134)Cs, (137)Cs, (90)Sr, (241)Am, (238)Pu and (239+240)Pu radioactivity. Concentrations (Bq.kg(-1) dry weight) have been observed to vary in the range 1.5-2.6 for (134)Cs, 2.8-11.4 for (90)Sr, and 0.13-0.48 for (241)Am, 0.016-0.062 for (238)Pu, 0.28-1.01 for (239+240)Pu and 155-543 for (40)K. The typical concentration of (137)Cs found in topsoils (0-2 cm) ranged in 7.5-576 Bq.kg(-1), dry weight. These values were greater than those observed in samples taken at greater depths (up to 32 cm). Activity ratios of (134)Cs/(137)Cs, (90)Sr/(137)Cs, (239+240)Pu/(137)Cs, (238)Pu/(137)Cs, (241)Am/(137)Cs, (239+240)Pu/(238)Pu and (241)Am /(238)Pu have mean values of 0.0049 (R=1), 0.29 (R=0.76), 0.41 (R=0.90), 0.39 (R=0.85), 0.41 (R=0.88), 7.72 (R=0.97) and 16.66 (R=0.98), respectively. The underlying concentrations were correlated and relatively higher than those reported in neighboring countries. One moss sample, as a biomonitor indicator, was measured and evaluated along with the soil samples. Its data showed higher concentrations of all measured radionuclides due to accumulations over years. The depth distribution of the fission product (137)Cs and the total deposition (Bq.m(-2)) were also studied in selected samples. Estimations of the annual effective dose equivalent due to (137)Cs-soil contamination showed values up to more than 200 microSv.     

Activity concentrations of 226Ra, 228Ra, 210Pb, 40K and 7Be and their temporal variations in surface air

Activity concentrations of the long-lived natural radionuclides ²²⁶Ra, ²²⁸Ra, ²¹⁰Pb, ⁴⁰K and of ⁷Be in surface air were measured twice monthly at a semi-rural location 10 km north of Munich (FRG) for at least three years. For the time interval 1983–1985, all values were found to be distributed log-normally, with geometric means (in μBq m⁻³) of 1·2 for ²²⁶Ra, 0·5 for ²²⁸Ra, 580 for ²¹⁰Pb, 12 for ⁴⁰K and 3500 for ⁷Be. Reflecting their common origin, the activity concentrations of ²²⁶Ra and ⁴⁰K are correlated with surface air dust concentrations (geometric mean 59 μg m⁻³). Seasonal variations of ²¹⁰Pb and ⁷Be air activity concentrations are established for the time interval 1978–1985.The contribution of local soil activity to the air activity concentrations of these radionuclides and of natural uranium is discussed. Resuspension factors are found to be of the order of 10⁻⁹m⁻¹.