Depth profiles of long lived radionuclides in Chernobyl soils sampled around 10 years after the accident

Depth profiles of the long-lived radionuclides, ¹³⁷Cs, ⁹⁰Sr, Pu isotopes and ²⁴¹Am were examined in undisturbed sandy, peaty and Podsol soils in the Chernobyl 30 km exclusion zone sampled around 10 years after the accident. Two Podsol soils, which have different radioactive deposition characteristics, have also been examined. Activity ratios of ^239,240Pu/¹³⁷Cs, ⁹⁰Sr/¹³⁷Cs, and ²⁴¹Am/¹³⁷Cs in the 0-1 cm layer of the two Podsol soils differed very much. Speciation of the radionuclides by sequential selective extraction was examined in the soils. Depth profiles of the soils have been analyzed according to the speciation results and soil characteristics.     

A new reference material for radionuclides in the mussel sample from the Mediterranean Sea (IAEA-437)

A new Reference Material (RM) for radionuclides in mussel (Mytilus galloprovincialis) from the Mediterranean Sea (IAEA-437) is described and the results of the certification process are presented. Four radionuclides (⁴⁰K, ²³⁴U, ²³⁸U, and ^239+240Pu) have been certified, and information values on massic activities with 95% confidence intervals are given for nine radionuclides (¹³⁷Cs, ²¹⁰Pb(²¹⁰Po), ²²⁶Ra, ²²⁸Ra, ²²⁸Th, ²³⁰Th, ²³²Th, ²³⁵U, and ²⁴¹Am). Results for less frequently reported radionuclides (⁹⁰Sr, ¹²⁹I, ²³⁸Pu, ²³⁹Pu, and ²⁴⁰Pu) are also reported. The RM can be used for quality assurance/quality control of the analysis of radionuclides in mussel samples, for the development and validation of analytical methods and for training purposes. The material is available in 200 g units.     

Proficiency test exercise on the determination of natural levels of radionuclides in mushroom reference material

The results from a proficiency test exercise for the determination of natural levels of radionuclides in mushroom reference material carried out by laboratories in six different countries are discussed. These laboratories submitted data on seven radionuclides, namely ¹³⁴Cs, ¹³⁷Cs, ⁴⁰K, ⁹⁰Sr, ²⁴¹Am, ²²⁶Ra, and ²¹⁰Po. However, only the data received for three of these radionuclides could be statistically evaluated to obtain consensus mean values and confidence intervals (at a significance level of 0.05). The contents of ¹³⁴Cs, ¹³⁷Cs and ⁴⁰K were quantified as 4.4, 2,899 and 1,136 Bq/kg, respectively.     

Reference material for radionuclides in sediment IAEA-384 (Fangataufa Lagoon sediment)

A reference material designed for the determination of anthropogenic and natural radionuclides in sediment, IAEA-384 (Fangataufa Lagoon sediment), is described and the results of certification are presented. The material has been certified for 8 radionuclides (⁴⁰K, ⁶⁰Co, ¹⁵⁵Eu, ²³⁰Th, ²³⁸U, ²³⁸Pu, ^239+240Pu and ²⁴¹Am). Information values are given for 12 radionuclides (⁹⁰Sr, ¹³⁷Cs, ²¹⁰Pb (²¹⁰Po), ²²⁶Ra, ²²⁸Ra, ²³²Th, ²³⁴U, ²³⁵U, ²³⁹Pu, ²⁴⁰Pu and ²⁴¹Pu). Less reported radionuclides include ²²⁸Th, ²³⁶U, ²³⁹Np and ²⁴²Pu. The reference material may be used for quality management of radioanalytical laboratories engaged in the analysis of radionuclides in the environment, as well as for the development and validation of analytical methods and for training purposes. The material is available from IAEA in 100 g units. Retired from IAEA in 2003.     

Natural radionuclides and cesium-137 content in Arabian Gulf bottom sediments

The activity concentration of natural radionuclides and¹³⁷Cs in the bottom sediment samples from the coastal area of Kuwait on the Arabian Gulf have been determined by -ray spectrometry with REGe detector. The data for the samples are very similar to those obtained for surface soil samples in Kuwait.¹ Two parent-progeny ratios for:^23$Th–²²⁶Ra and²²⁸Ac–²⁰⁸Tl to evaluate the geochemical behavior of the radionuclides have been estimated. The existence of a serious disequilibrium between²³⁴Th and²²⁶Ra for samples taken from the vicinity of Kuwait islands and the Ras Al-Zoor area was found. The strait between the coast of Kuwait and Bubiyan island is proposed for the future sedimentation rate determinations on the basis of²¹⁰Pb measurements. No serious contamination by technogenic radionuclides for this region of Arabian Gulf was observed.     

Radionuclide variations in the air over Monaco

Radionuclides in aerosols and precipitation have been analyzed by IAEA-MEL in Monaco since 1987 and 1999, respectively, to identify their behavior in the atmosphere and delivery into the northwestern Mediterranean Sea. While the concentration of ⁷Be in aerosols has been affected by the stratospheric-tropospheric mixing and precipitation, the concentration of ¹³⁷Cs in aerosols has been influenced by a combination of local meteorological conditions and re-suspension of ¹³⁷Cs from soil. Higher concentrations of ⁷Be, ¹³⁷Cs, ^239,240Pu and ²⁴¹Am in precipitation occurred during spring and summer. The highest deposition rates of these radionuclides were observed in spring and autumn during periods of high precipitation. A good correlation was found between the amount of precipitation and depositional flux for ⁷Be, but not for ¹³⁷Cs, ^239,240Pu and ²⁴¹Am. This indicates that the wet process as well as the dry process seem to be important factors in determining the annual deposition for transuranic radionuclides and ¹³⁷Cs.     

The Effect of Carbonate Soil on Transport and Dose Estimates for Long-Lived Radionuclides at a U.S. Pacific Test Site

The United States conducted a series of nuclear tests from 1946 to 1958 at Bikini, a coral atoll, in the Marshall Islands (MI). The aquatic and terrestrial environments of the atoll are still contaminated with several long-lived radionuclides that were generated during testing. The four major radionuclides found in terrestrial plants and soils are cesium-137, strontium-90, plutonium-239+240 and americium-241. Cesium-137 in the coral soils is more available for uptake by plants than ¹³⁷Cs associated with continental soils of North America or Europe. Soil-to-plant ¹³⁷Cs median concentration ratios (CR) (kBq·kg^-1 dry weight plant/kBq·kg^-1 dry weight soil) for tropical fruits and vegetables range between 0.8 and 36, much larger than the range of 0.005 to 0.5 reported for vegetation in temperate zones. Conversely, ⁹⁰Sr median CRs range from 0.006 to 1.0 at the atoll versus a range from 0.02 to 3.0 for continental silica-based soils. Thus, the relative uptake of ¹³⁷Cs and ⁹⁰Sr by plants in carbonate soils is reversed from that observed in silica-based soils. The CRs for ^239+240Pu and ²⁴¹Am are very similar to those observed in continental soils. Values range from 10^-6 to 10^-4 for both ^239+240Pu and ²⁴¹Am. No significant difference is observed between the two in coral soil. The uptake of ¹³⁷Cs by plants is enhanced because of the absence of mineral binding sites and the low concentration of potassium in the coral soil. Cesium-137 is bound to the organic fraction of the soil, whereas ⁹⁰Sr, ^239+240Pu and ²⁴¹Am are primarily bound to soil particles. Assessment of plant uptake for ¹³⁷Cs and ⁹⁰Sr into locally grown food crops was a major contributing factor in: (1) reliably predicting the radiological dose for returning residents and (2) developing a strategy to limit the availability and uptake of ¹³⁷Cs into locally grown food crops.     

Chemometry of the distribution and origin of 226Ra, 228Ra, 40K and 137Cs in the soil near the lignite fired plants of West Macedonia (Greece)

The distribution and origin of natural ⁴⁰K,²²⁶Ra and²²⁸Ra and artificial ¹³⁷Cs have been investigated in the surface soil of a West Macedonia basin at four lignite fired power plants. No significant increase in specific activity of soil due to natural radionuclides of coal has been found. The specific activities of ²²⁶Ra, ²²⁸Ra and ⁴⁰K are equal to those of Greek soils. Radiocesium activity is slightly higher in the first 10 cm layer. The application of chemometrical methods confirmed that the radionulides ²²⁶Ra, ²²⁸Ra and ⁴⁰K are natural components of the soil and they do not originate from fly ash. This revised version was published online in July 2006 with corrections to the Cover Date.     

239,240Pu,241Am and137Cs in soils from several areas in China

This paper gives the first data on^239,240Pu and²⁴¹Am in Chinese soils. Surface soil samples with a set of 0–5 cm and 5–20 cm depth were collected from Beijing, Taiyuan, Shijiazhuang and Jinang of China in 1990, and^239,240Pu,²⁴¹Am and¹³⁷Cs, including naturally occurring radionuclides, in these samples were measured to evaluate their present levels and distributions. From these results, the average accumulated depositions were estimated roughly to be 24±13 MBq/km² for^239,240Pu, 10±5 MBq/km² for²⁴¹Am and 1.2±0.7 GBq/km² for¹³⁷Cs. The activity ratios of^239,240Pu/¹³⁷Cs and²⁴¹Am/^239,240Pu ranged from 0.016 to 0.026 with a mean value of 0.020±0.004 and 0.35 to 0.49 with a mean value of 0.43±0.05, respectively.     

Some aspects of determination of radionuclides at the former Semipalatinsk Nuclear Test Site

There is investigated a radionuclide composition of the soil samples, selected in various parts of former Semipalatinsk Nuclear Test Site (SNTS). The gamma-spectrometric method was used for determination of¹³⁷Cs and²⁴¹Am. For determination of⁹⁰Sr and isotopes of plutonium a radiochemical separation was used. The results of determinations show a distinction in distribution of radionuclides on depth for various investigated areas and for various size fractions of surface layers. The study of the size fractions has shown an enrichment of a magnetic faction by²⁴¹Am.     

90Sr, 137Cs, 238Pu, 239+240Pu and 241Am levels in terrestrial and marine ecosystems around the Italian base in Antarctica

During the last 14 years the Radioecology Laboratory of Parma University and the General Chemistry Institute of Urbino University collaborated on a radioecological programme having the aim to observe the evolution of antropogenic radioactivity in Antarctica in the period 1987-2001. The artificial radionuclides considered were ⁹⁰Sr, ¹³⁷Cs, ^239+240Pu,²³⁸Pu and ²⁴¹Am. The contamination seems to be higher in the continental environment rather than in the marine one. Mosses, algae and lichens showed the highest values for all radionuclides analyzed. The results prove that the Antarctic continent is interested by radioactive pollution. As far as ¹³⁷Cs is concerned, a progressive decrease was observed.     

Analysis of 36Cl in Savannah River Site radioactive waste

The present work shows the activity levels of ²²⁶Ra, ²²⁸Ra, ⁴⁰K and ¹³⁷Cs in bottom sediments collected from eight locations of Mumbai Harbour Bay. The study has shown that ⁴⁰K and ²²⁸Ra concentration is nearly uniform throughout the studied area while ²²⁶Ra and ¹³⁷Cs are more concentrated in the southern regions of the bay. The significant variation in the activity levels of radionuclides within the study site might be due to their sorption/desorption processes onto the surface of sediment materials. The low mean value of ²²⁶Ra/²²⁸Ra ratio (0.72) in the sediments indicates that ²³⁸U has relatively greater solubility and mobility than ²³²Th. Similarly, low activity ratio (0.18) for ¹³⁷Cs/⁴⁰K reflects the presence of very high content of ⁴⁰K in sediment due to presence of primary minerals in sediment. Silt and clay were reported to dominate the composition of the sediment. A significant positive correlation between ²²⁶Ra and ²²⁸Ra and ¹³⁷Cs and ⁴⁰K suggest a similar origin of their geochemical sources and identical behavior during transport in the sediment system.     

Study of 137Cs, 90Sr, 239,240Pu, 238Pu and 241Am behavior in the Chernobyl soil

The vertical distribution of ¹³⁷Cs, ⁹⁰Sr, ^239,240Pu, ²³⁸Pu and ²⁴¹Am was determined in soil samples collected from the Chernobyl exclusion zone in 1994. The results show very close distribution profiles for all radionuclides, with about 90% of the total activity of each nuclide lying between the surface and the fourth centimeter. Sequential extraction methods were used to determine the association of radionuclides in soil. The data on vertical distribution of radionuclide species were used to calculate their vertical migration parameters.     

Influence of plant roots upon the mobility of radionuclides in soil, with respect to location of contamination below the surface

The movement of⁸⁵Sr,¹³⁷Cs,⁵⁴Mn and⁶⁰Co in the 50 cm soil profile was studied with and without the presence of plant roots (triticum aestivum) in order to investigate the influence of roots and depth contamination upon the migration of radionuclides. The water table was maintained manually at 3 cm from the bottom. The physiochemical characteristics (E_h Fe^–2, NH ₄ ⁺ , pH and moisture content) as well as the total and extractable radioactivity were investigated. In the discrete contamination, where the location of contamination varied within the soil profile (0–5, 25–30 or 45–50 cm from the top), the influence of location upon the movement of these radionuclides was also studied. It was found that the changes in the soil physicochemical characteristics influenced the mobility of the four radionuclides. The extractability of⁵⁴Mn and⁶⁰Co was significantly increased in the reducing region of the soil, whereas that of⁸⁵Sr,¹³⁷Cs was not. Plant roots excerted significant effects upon the soil characteristics, via, reducing the E_h pH and moisture content of the soil; increasing the extractability of both⁵⁴Mn and⁶⁰Co from the depth of 35 cm downwards. Radionuclide migration occurred via physicochemical and biological transport. The biological transport via plant roots was of particular importance for¹³⁷Cs. Location of contamination had a significant influence upon the mobility of radionuclides. The migration of radionuclides was in the sequence of contamination in middle>bottom>top. The degree of the influence varied with radionuclides concemed. In the top layer contamination, the rank of the migration from the contamination layers, on the other hand⁵⁴Mn,⁶⁰Co and¹³⁷Cs were more mobile and the movement was:⁸⁵Sr⁵⁴Mn⁶⁰Co>¹³⁷Cs. In the middle and bottom contamination layers, on the other hand,⁵⁴Mn and⁶⁰Co and¹³⁷Cs were more mobile and the movement was⁸⁵Sr⁵⁴Mn⁶⁰Co>¹³⁷Cs. The results provide evidence conceming the soil-root interaction influencing the transfer efficiency of radionuclides from below the soil surface into the human food chain.     

Radioisotopes of thirteen elements in intertidal coastal and estuarine sediments in the Irish Sea

A survey has been carried out of⁴⁰K,⁶⁰Co,⁹⁹Tc,¹⁰⁶Ru,¹²⁵Sb,¹²⁹I,¹³⁴Cs,¹³⁷Cs,¹⁵⁴Eu,²²⁶Ra,²²⁸Ra,²³⁷Np,²³⁸Pu,^239,240Pu,²⁴¹Pu,²⁴¹Am,²⁴²Cm, and^243,244Cm activities in sediments from the Irish Sea. Several of these radionuclides were measured independently at two separate laboratories to enable the intercomparison of the results produced. The comprehensive data set generated allows the present spatial distributions of these radionuclides in coastal sediments to be examined in relation to sediment textural characteristics and by comparison with earlier survey, enables the temporal trends in their activities to be determined. In general all artificial radionuclides showed lower activities in sediments in response to falling discharges from Sellafield and relationships with either grain size, distance from Sellafield or both. Isotope ratios were similar to cumulative weighted activity ratios rather than present day values due to sediment mixing. Pu levels supplied evidence for the lag in response of sediment deposits with increasing distance from Sellafield due to sediment transport.     

Investigation of the solid phase speciation of90Sr,137Cs,239Pu and241Am in soils determined by extraction and ultra-filtration methods

Bio-availability of radionuclides in soil is influenced by their chemical form and association with different geo-chemical phases. The solid phase speciation of aged⁹⁰Sr,¹³⁷Cs,²³⁹Pu and²⁴¹Am in three common agricultural soil types was investigated using separate extractions with seven reagents. Six of these are commonly used to determine radionuclide association with readily exchangeable forms, carbonates, iron and manganese oxides and organic phases. Trimethyl-chlorosilane was also included because of its ability to extract radionuclide-humate complexes from soil. The extract from this part of the study was subsequently subjected to ultra-filtration to determine the association of radionuclides with different molecular size fractions. The results from this speciation study are discussed in terms of availability for plant uptake.     

238Pu, 239+240Pu, 241Am, 90Sr and 137Cs in mountain soil samples from the Tatra National Park (Poland)

Activity concentrations and inventory for ²³⁸Pu, ^239+240Pu, ²⁴¹Am, ⁹⁰Sr, and ¹³⁷Cs in soil from Tatra Mountains of Poland are presented. Soil samples were collected using 10 cm diameter cores down to 10 cm and sliced into 3 slices. Details of the applied procedure are described with the quality assurance program. The maximum activity concentrations found for various samples were: 1782±13 Bq/kg, 17.4±0.9 Bq/kg, 3.4±0.3 Bq/kg and 84±7 Bq/kg for ¹³⁷Cs, ^239+240Pu, ²⁴¹Am and ⁹⁰Sr, respectively. The maximum cumulated deposition of ^239+240Pu is 201±8 Bq/m². The origin of radionuclides is discussed, based mostly on the observed isotopic ratio of Pu. Significant correlations were found between ^239+240Pu, ²⁴¹Am and ¹³⁷Cs. The effective vertical migration rate seems to be in the order of: ⁹⁰Sr≫Pu>Am>Cs.     

Leaching of uranium,radium and thorium from vertisol soil by ground water

Shallow land burial is routinely used for the disposal of low-level radioactive waste. Natural processes causing leaching of radionuclides can lead to contamination of surrounding ground water and soil by the radionuclides. The comparative leachability of radionuclides U_(nat), ²²⁶Ra, ²²⁸Ra and Th_(nat) from the soil of a radioactive waste disposal site, by ground water was evaluated. The probability of leaching was obtained in the following order Ra (≈77%) > U (≈40%) > Th (≈20%). Observed ratios (OR) were calculated to correlate leachability of radionuclides to that of major cations Ca²⁺ and Mg²⁺. The leaching of the radionuclides was seen to be dependent on Ca²⁺ and SO₄²⁻ leached from the soil. This study provides sitespecific leachability of radionuclides, that can be used as indicator of the tendency for migration or retention in soil. It can play an important role during an unforeseen accident like breach of containment at the waste disposal site leading to contamination of soil and ground water and causing hazard to public via drinking water route.     

Physicochemical fractionation of americium, thorium, and uranium in Chernozem soil after sharp temperature change and soil drought

A sequential extraction procedure was used to study the changes in the physicochemical forms of americium (Am), thorium (Th), and uranium (U) in laboratory-contaminated Chernozem soil as a result of sharp variations of the environmental temperature and soil moisture. The influence of freezing and soil drought on the radio-ecological hazard was evaluated three months after radioactive contamination with aqueous solutions of ²⁴¹Am, ²³⁴Th, and U. The subsequent changes in the physicochemical forms of the actinides, caused by sharp increases in the environmental temperature and soil moisture, were examined for one month. The data showed that continuous freezing increased the potentially mobile forms of Am and Th but had the opposite effect on U. Prolonged soil drought did not influence the fractionation of Am and Th but led to the redistribution of U between the carbonates and organic matter and caused its immobilisation. The sharp increase in the temperature of the frozen soil caused the immobilisation of Am and Th and increased the potential mobility of U. The warming and enhanced humidity of the dry soil led to the immobilisation of Am and redistribution of U between the soil phases.     

Natural and Artificial Radionuclides in Selected Lignites from Istanbul

The radioactivity levels of Istanbul environs lignites were determined. The gamma-spectrometric technique has been used for the determination of activity levels of naturally occurring radionuclides ^235+238U, ^228+232Th, ⁴⁰K, ²²⁶Ra and fallout radionuclides ¹³⁷Cs in lignites taken from 7 different parts of Istanbul. Concentration of ²³⁸U, ^228+232Th, ⁴⁰K, ²²⁶Ra ¹³⁷Cs and ²³⁵U were found up to 1.6 ppm, 1.7 ppm, 4.9 ppm, 56.8 Bq/kg, 34 Bq/kg, 1.8 Bq/kg, 1.6 Bq/kg, respectively. In addition total alpha- and beta-activity levels in lignite samples were found to be 7.6 and 15 eps, respectively.