Behavior of neutron-activated uranium dioxide dust particles in the gastrointestinal tract of the rat

The behavior of neutron-irradiated, simulated Chernobyl UO2 particles containing 141Ce, 144Ce, 95Zr, 95Nb, and 103Ru in the gastrointestinal tract was investigated to obtain basic information for dosimetric and risk analyses of nuclear accidents. After the UO2 particles were administered to rats intragastrically, the distribution and retention of specific radionuclides were studied by using whole-body autoradiography and gamma-spectrometric analysis of tissues. None of the radionuclides were detected in liver, kidney, muscle, bone, brain, blood, and urine. Approximately 98% of the total administered radioactivity was excreted in feces within 3 days. A two times greater intestinal retention (about 6%) of 95Nb than for the other radionuclides was observed 1 day after administration. The results indicate that this kind of relatively insoluble particulate material is not absorbed or retained significantly in the epithelial cells of the intestinal wall. Fallout particles containing high-energy beta sources, 106Ru and 144Ce, result in a very high radiation dose (up to several Gy/day) in the vicinity of a hot particle. Niobium-95 with low average beta energy (0.043 MeV (100%)) does not increase the total dose to the GI tract significantly despite its longer retention in the intestine. Evaluation of the biological effects of these particles in the GI tract by using a dosimetric model based on uniform distribution of activity may be misleading.     

Effect of mixed ligand complex therapy on the retention of 95Nb and 144Ce in mice

We have examined in mice the effects of mixed ligand treatments with desferrioxamine B (DFOA), Na3Ca-diethylenetriamine pentaacetic acid (DTPA), and DL-penicillamine (PA) on the retention of a mixture of 95Nb and 144Ce. The results show that 95Nb + 144Ce could be mobilized effectively by simultaneous application of specific agents (i.e., DFOA, DTPA) with no decrease in their efficiencies.     

The distribution in mice of intravenously administered labelled Candida albicans.

The time dependence of the distribution of intravenously injected radiolabelled Candida albicans in the body of mice was studied. The Candida cells were labelled by cultivating them 7 days at 28 degrees C in a medium containing one of the following radionuclides: 46Sc, 95Nb, 59Fe, 144ce, 89Sr, 60Co, 65Zn, 54Mn, 45Ca, 51Cr and 91Y, which are listed in decreasing order in respect to amount bound. The labelled cells were killed by heating them 120 min at 60 degrees C, without loss of immunologic properties. Owing to the amount and strength of binding, 144Ce labelled Candida, together with 14C labelled cells was used in animal kinetic study. A rapid disappearance of the labelled cells from blood, interrupted by a small peak, was paralleled by a transient uptake in lungs and followed by a long lasting accumulation in the liver. The kidneys and spleen revealed only small uptakes of the labelled material.     

Biosorption of radionuclides by Rhizopus arrhizus

The sorption of various radionuclides viz. 233U, 239Pu, 241Am, 144Ce, 147Pm, 152+154Eu and 95Zr from aqueous nitrate medium has been studied using biomass Rhizopus arrhizus. The biosorption of 233U and 239Pu was found to be maximum at pH 6-7 whereas for other trivalent actinides and fission products viz. 241Am, 144Ce, 147Pm, 152+154Eu and tetravalent 95Zr, it was more effective at pH 2. This biomass is a promising sorbant for the treatment of radioactive effluents from nuclear industry. © Rapid Science Ltd. 1998     

Fission-product radionuclides in sediments from the north-east irish sea

Summary 1. Gamma radiation dose-rates over mud-flat areas are shown to be at least ten times those measured over sandy beaches.2. Analysis of the surface sediment layer in an estuarine area 6 miles from the Windscale effluent pipeline shows the major gamma-emitting radionuclides to be⁹⁵Zr,⁹⁵Nb and¹⁰⁶Rh.3. Core sampling has indicated that the radioactivity concentration in silt decreases exponentially with depth from the surface layer.4. It is shown that the gamma dose-rate above silt banks is largely accounted for by the concentration of⁹⁵Zr/⁹⁵Nb in the surface silt layer. The residual gamma dose is probably accounted for by¹⁰⁶Ru/¹⁰⁶Rh distributed beneath the surface layer.5. The accumulation factors of⁹⁵Zr +⁹⁵Nb and¹⁰⁶Ru in the surface silt layer are approximately 1.5×10⁴.6. The relationship of radioactivity concentration in surface silt to distance from the effluent pipeline can be described by a simple power function of distance.

---

Spaltprodukt-Radionuklide in Sedimenten der nordöstlichen Irischen See

Kurzfassung Als Teil einer Untersuchung über die Verbreitung von radioaktivem Abwasser, das von der radiochemischen Aufarbeitungsanlage in Windscale stammt, wurden Messungen der Gamma-Dosisleistung auf Schlickböden in Ästuaren vorgenommen. Es zeigte sich, daß die Dosisleistungen hier mindestens um eine Größenordnung höher sind als die, welche auf reinem Sandboden gemessen wurden. Oberflächensedimente, die hinsichtlich ihrer Radioaktivität untersucht wurden, enthalten als wichtigste Radionuklide die Spaltprodukte⁹⁵Zr +⁹⁵Nb,¹⁰⁶Ru,¹⁴⁴Ce und¹³⁷Cs. Die Konzentrationen der einzelnen Radionuklide stehen in Beziehung zur Abwassermenge. Probebohrungen in Sedimenten zeigten, daß sich die Konzentration der Radioaktivität exponentiell mit der Tiefe ändert. Der Anreicherungsfaktor von⁹⁵Zr +⁹⁵Nb,¹⁰⁶Ru in Oberflächensedimenten von Ästuaren beträgt ungefähr 1,5 × 10⁴, für¹³⁷Cs dagegen 1,0 × 10³. Die Konzentrationen von⁹⁵Zr +⁹⁵Nb,¹⁰⁶Ru und¹⁴⁴Ce in Oberflächensedimenten sind abhängig vom Abstand der Abwassereinleitung bei Windscale.

     

Dose assessment for the Metlino and Muslyumovo populations who lived along the Techa river from 1949 to 1954

In the period from 1949 to 1956, liquid radioactive waste was routinely and accidentally discharged by the Mayak Production Association, Southern Urals, Russia, into the Techa river. Based on a novel approach, the contamination of the Techa river water, the bottom sediments and the adjacent flood plains was modelled, and internal and external doses were estimated for two villages located downstream of the site of liquid radioactive waste release. Altogether, 11 radionuclides that occurred in the liquid radioactive waste were included in the calculations. The results suggest significantly higher doses than previously assumed, with the major contribution in the year 1951. Radionuclides with half-lives of less than 1 year, such as ⁸⁹Sr, ¹³¹I, ⁹⁵Zr+⁹⁵Nb, ¹⁰³Ru+^103mRh, ¹⁴⁰Ba+¹⁴⁰La, and ¹⁴⁴Ce+¹⁴⁴Pr, represent the major sources and, in contrast, long-lived radionuclides, such as ⁹⁰Sr and ¹³⁷Cs that have so far been assumed to be most important, did not dominate the doses. For adults from the village Metlino, located 7 km downstream of the site of liquid radioactive waste discharge, the committed effective doses due to intake of radionuclides were calculated to be about 2.3 Sv, while the external doses were between about 1.2 Sv and 6.9 Sv. On the other hand, for adults from Muslyumovo, located 75 km downstream, the commited effective doses due to intake of radionuclides were calculated to be about 0.5 Sv, while the external doses were between 0.5 Sv and 2.0 Sv. The values for the skin doses to the Metlino and Muslyumovo populations were about 7.1 Sv and 1.3 Sv, respectively. It is concluded that the current dose estimates for the residents of the Techa river need, therefore, reevaluation.     

Flux of certain radionuclides in the blood-clam Anadara granosa Linneaus under environmental conditions

The flux of fission product nuclides, caesium-137. cerium-144. and ruthenium-106, in the Bombay harbour ecosystem has been measured over a period of six years (1970–1976). during which the input of controlled low level radioactive waste was gradually reduced by more than 20 times. Of the various pelagic and benthic species studied, the arcid clam Anadara granosa Linn, showed a specific affinity for all three radionuclides; sequence of the degree of bio-accumulation was Ce ? Ru > Cs. Furthermore, the concentration of these nuclides in the tissues varied with the levels in the sedimentary material, which in turn was related to the inputs, maintaining some kind of equilibrium. On reaching maximum accumulation the levels of all three nuclides in the clam population decreased exponentially with time although the radioactivity was still available especially in the sediment. This decrease of radioactivity is defined as an ‘ecological loss rate’. The ecological half-time for cerium-144 and ruthenium-106 was about 3.6 times longer, and that of caesium-137 significantly shorter, than their respective physical half-lives. The ecological half-times of all three radionuclides were predominantly influenced by the environment rather than by the biological half-lives. This indicates that the biological half-lives of these nuclides were much shorter than their respective ecological half-lives. The biological half-time of caesium-137 was biphasic; the short-lived component had a half-time of about three days and the long-lived component had one of about 15 days.The bio-accumulation of an activation product nuclide cobalt-60 in A. granosa increased with the time of exposure and reached a level significantly higher than that of caesium-137, but was independent of the ambient concentrations and temperature. Thus the species was found to maintain the tissue concentration of fission product nuclides, cerium-144, ruthenium-106, and caesium-137 through adjusting physiological flux rates, in equilibrium with the changing levels of radionuclides in the environmental matrices, but not of the activation product nuclide cobalt-60.     

Radionuclide transfer to marine biota species: review of Russian language studies

An extensive programme of experiments on transfer of radionuclides to aquatic species was conducted in the former USSR starting from the early 1950s. Only a few of these studies were made available in the English language literature or taken into account in international reviews of radionuclide behaviour in marine ecosystems. Therefore, an overview of original information on radionuclide transfer to marine biota species available from Russian language literature sources is presented here. The concentration ratio (CR) values for many radionuclides and for marine species such as: ²³⁹Pu, ¹⁰⁶Ru and ⁹⁵Zr (crustacean), ⁵⁴Mn, ⁹⁰Sr, ⁹⁵Nb, ¹⁰⁶Ru, ¹³⁷Cs ²³⁹Pu, ²⁴¹Am and natural U (molluscs), and ⁵⁴Mn, ⁹⁰Sr, ¹³⁷Cs and ¹⁴⁴Ce (fish) are in good agreement with those previously published, whilst for some of them, in particular, for ³²P and ¹¹⁰Ag (crustaceans), ³⁵S (molluscs), ³²P, ³⁵S, ⁹⁵Nb, and ¹⁰⁶Ru (macroalgae) and ⁶⁰Co and ^239,240Pu (fish) the data presented here suggest that changes in the default CR reference values presented in recent marine reviews may be required. The data presented here are intended to supplement substantially the CR values being collated within the handbook on Wildlife Transfer Coefficients, coordinated under the IAEA EMRAS II programme.     

Radionuclides in siberian Thymallus from radiation-contaminated area in the middle stream of the Yenisei River

Concentration of artificial radionuclides in bodies of arctic grayling from the radioactively contaminated zone of the Yenisei River in the vicinity of the Mining-and-Chemical Combine of Rosatom was investigated in 2007-2010. Gamma-spectrometric analysis revealed artificial radionuclides in all the organs and tissues of fish. The isotope composition was the most diverse (60Co, 65Zn, 85Sr, 99Mo, 106Ru, 137Cs, 144Ce) in internal organs of grayling. The activity of radionuclides increased in internal organs including liver and kidney and in the content of digestive tract of grayling during winter and spring, which coincided with the change in the feeding spectrum of grayling. The trophic transfer factor of radionuclides from zoobenthos (Philolimnogammarus spp.) to whole bodies and muscles of grayling was over 1 (1.8-2.4) only for natural radionuclide 40K. The trophic transfer of artificial radionuclides (60Co, 65Zn, 137Cs) to muscles and bodies of grayling was one-two orders of magnitude less effective.     

Radionuclide accumulation by Anodonta piscinalis Nilsson (Lamellibranchiata) in a continuous flow system

Summary The present investigation has been concerned with the accumulation of radionuclides by the freshwater lamellibranch Anodonta piscinalis Nilsson. Specimens of the animal were exposed for 125 days to approximately constant concentrations of the radionuclides P³², Sr⁸⁹, Cs¹³⁷, Ce¹⁴⁴ and Zr⁹⁵/Nb⁹⁵; in addition Ru¹⁰³ was included among the radionuclides for the last 55 days of the experiment. The investigation was conducted in a model recipient with environmental factors similar to those existing in the animals' biotope in nature. The accumulation of the radionuclides was measured in the body and valves of the lamellibranch. The results indicate that an approximately constant level of radioactivity was reached after one month's exposure in these two parts of the animal. Subsequently the level of radioactivity showed a fluctuating pattern which was ascribed to seasonal and physiological changes. Accumulation of the radionuclides in the test animals varied according to the following sequence, arranged in order of decreasing affinity: P³² > Sr⁸⁹ > Ce¹⁴⁴ > Ru¹⁰³ > Cs¹³⁷ > Zr⁹⁵/Nb⁹⁵. Factors which may complicate the practical use of freshwater lamellibranchs in the monitoring of contaminated recipients are pointed out and discussed.

---

Zusammenfassung Die vorliegende Untersuchung betrifft die Anh?ufung von Radioisotopen bei der Lamellibranchiate Anodonta piscinalis Nilsson. Exemplare dieses Tieres wurden beobachtet w?hrend 125 Tagen bei ann?hernd konstanter Konzentration der Isotopen P³², Sr⁸⁹, Cs¹³⁷, Ce¹⁴⁴ und Zr⁹⁵/Nb⁹⁵ w?hrend 55 Tagen des Experimentes wurde Ru¹⁰³ miteinbezogen. Das Experiment wurde in einem Flussmodell durchgeführt bei gleichen Umgebungsfaktoren wie sie das Tier in seinem natürlichen Biotop findet. Die Anh?ufung der radioaktiven Isotope wurde im K?rper und in der Schale der Lamellibranchiate gemessen. Das Resultat erwies, dass innerhalb eines Monats das Tier eine gewisse Radioaktivit?t erreichte in den zwei geprüften Teilen. Das Radioaktivit?tsniveau wies eine wellenartige Schwankung auf, welche dem Jahreszeitlichen und physiologischen Wechsel zuzuschreiben ist. Die Radioisotope wurden im Tier in folgender Reihenfolge angeh?uft: P³² > Sr⁸⁹ > Ce¹⁴⁴ > Ru¹⁰³ > Cs¹³⁷ > Zr⁹⁵/Nb⁹⁵. Faktoren komplizierter Natur sind für den praktischen Gebrauch der Süsswasserlamellibranchiata in der Radioaktivit?ts überwachung verunreinigter Gew?sser begrenzend, und wurden hier diskutiert.

---

---

This work was performed under International Atomic Energy Agency Research Contract No. 37.     

Radioactive contamination of bottom sediments in the upper reaches of the Techa river: analysis of the data obtained in 1950 and 1951

A stationary sorption model has been developed for re-evaluating and analysing archive data from 1950-1951 on the radioactive contamination of Techa river bottom sediments close to the site of liquid radioactive waste discharge. In general, good agreement was obtained between calculations and measurements, which substantiates further the assumptions and conclusions in two preceding articles, on the radionuclide composition of discharged liquid radioactive waste. Estimates on the effective liquid radioactive waste discharges given here are significantly different from those deduced in the 1950s, i.e. in summer 1950 and October 1951. The results are discussed in relation to the Techa River Dosimetry System 2000 (TRDS-2000) that has recently been presented to serve as a means for estimating doses to the Techa river residents. Parameter values describing the exponential decrease of bottom sediment contamination along the river due to short-lived radionuclides, such as (106)Ru, and (144)Ce, agree reasonably with those used in TRDS-2000. However, for other radionuclides, such as (95)Zr, (95)Nb, (91)Y, (90)Sr and (137)Cs, substantial differences are found. It is demonstrated that water flow rate, width of the river, and surface area of bottom sediments are important parameters which were not adequately taken into account in TRDS-2000. Also, the stirring-up of contaminated bottom sediments and their subsequent transport by the water flow are seen to be an important mechanism that governs the radionuclide transport downstream. This mechanism was not included in the TRDS-2000 model. It is concluded that the sorption model used in TRDS-2000 for the reconstruction of radioactive contamination of water and bottom sediments of the Techa river in 1949-1951, is subject to considerable errors. While the present paper is focussed on details of the dosimetric modelling, the implications for the Techa river dosimetry are major. They will be further elucidated in a forthcoming paper.     

Repeated inhalation exposure of rats to aerosols of 144CeO2. I. Lung, liver, and skeletal dosimetry.

To develop a better understanding of the influence of cumulative radiation dose and dose rate to the lungs on the biological responses to inhaled radionuclides, several studies are in progress at this institute in which laboratory animals have been exposed once or repeatedly to aerosols of insoluble particles containing 144Ce or 239Pu. In the study reported here, F344 rats were exposed repeatedly to aerosols of 144CeO2 beginning at 94 days of age to reestablish desired lung burdens of 1.9, 9.2, 46, or 230 kBq of 144Ce every 60 days for 1 year (seven exposures). Other 94-day-old rats were exposed once to achieve similar desired initial lung burdens of 144Ce. Older rats were exposed once to achieve desired initial lung burdens of 46 or 230 kBq when 500 days of age, the age of the repeatedly exposed rats when exposed for the last time. Control rats were either unexposed, sham-exposed once or repeatedly, or exposed once or repeatedly to stable CeO2. Approximately equal numbers of male and female rats were used. The cumulative beta-radiation doses to the lungs, liver, and skeleton of rats exposed repeatedly were similar to those of rats with similar total lung burdens of 144Ce from a single inhalation exposure. The average beta-radiation dose rate to the lungs of the rats exposed repeatedly was about one-fifth of that in rats with similar total lung burdens after a single exposure.     

Influence of radiation dose patterns on lung tumor incidence in dogs that inhaled beta emitters: a preliminary report

Different radiation dose patterns to the lung from inhaled beta-emitting radionuclides may influence the frequency and kind of biological effects. To determine the magnitude of this influence, groups of Beagle dogs were exposed to aerosols of 90Y, 91Y, 144Ce, or 90Sr in relatively insoluble particles and observed for their life spans. Different dose patterns were achieved by using these radionuclides having similar beta emissions and chemical form but having physical half-lives ranging from 2.6 days to 28 years. The range of initial lung burdens of radionuclides studied resulted in a range of biological effects from early deaths at the highest radiation doses to no discernible effects at the lowest doses. The effective half-lives of the four radionuclides in the lung ranged from 2.5 to 600 days. Within 1.5 years after exposure, some dogs died with radiation pneumonitis and pulmonary fibrosis. Between 1.5 and 10 years after exposure, 42 pulmonary carcinomas and 28 pulmonary sarcomas were observed in 163 dogs that died. Protracted irradiation of the lung from 90Sr or 144Ce resulted in a relatively high radiation dose and produced more total lung tumors but fewer lung tumors per rad than less protracted irradiation from 90Y or 91Y. At 10 years after inhalation exposure, the difference in risk per rad among the different dose patterns was a factor of 4 to 8, indicating that the different radiation dose patterns from inhaled beta emitters do influence lung tumor risk factors, at least at high (greater than 20,000 rad) doses to lung.     

Significance of Trace Element Profile of Blood of Persons with Multiple Caries versus Sound Teeth

In order to determine any possible relation between chemical composition of a person’s blood to formation of dental caries, whole blood was analyzed for 35 inorganic elements (Si, Al, Fe, Ca, Mg, K, Mn, Ti, P, Li, Be, B, V, Cr, Co, Ni, Cu, Zn, As, Sr, Y, Nb, Mo, Ag, Cd, Sn, Sb, Ba, La, Ce, W, Pb, Bi, Zr, and F) in the 15 people having sound teeth as well as an equal number of those having multiple caries. The results showed the absence of 13 elements (Si, Al, Mn, Ti, Be, Co, As, Y, Cd, Ba, La, Ce, and Zr) in the blood of both groups. Of the remaining 22 elements, the results of only seven elements (Fe, P, B, V, Sr, Sn, and F) were significantly different between the two groups. The most remarkable finding of this study was significantly decreased amount of phosphorus, strontium, and fluorine and perhaps increased boron in the blood of persons with caries.     

Measurement of resuspended aerosol in the Chernobyl area

Size distribution measurements of particulate radionuclides were performed at two sites in the Chernobyl 30-km exclusion zone using several cascade impactors. The results obtained in the period September 1986 till June 1993 were discussed with regard to the general assumption of a log-normal activity size distribution in inhalation dose assessment. At Zapolie (a site 14 km from the Chernobyl reactor) a bimodal distribution was observed in 91% of all measured distributions. In most cases the medians were about 4 µm and in the range 20–30 µm. According to soil granulometric data this finding was explained by superimposing two processes: local resuspension and advective transport of radioactive aerosol from highly contaminated territories. The mean air concentration showed an increasing proportion of inhalable particles over the years since the accident. In 1993 the inhalable fraction was about 48% of the total concentration. At Pripyat, a site situated within a highly contaminated area, unimodal types of size distributions were predominant with the median diameters in the range 5–10 µm for ¹³⁷Cs. For the three nuclides ¹³⁷Cs, ¹⁴⁴Ce and ¹⁰⁶Ru, very similar types of distribution were observed. Apparently, the radioactive aerosol was of fuel origin. During a forest fire at a distance of 17 km, the majority of the radioactivity was associated with submicrometer particles with median diameters in the range 0.28–0.50 µm.     

External radiation exposure of residents living close to the Mayak facility: main sources,dose estimates,and comparison with earlier assessments

In 1951 and 1952 specialists from the Mayak production association investigated the radiological situation in the area of the Metlinski reservoir that was located 5-7 km from the site of liquid radioactive waste (LRW) discharge. Based on their measurements of both the specific radioactivity in the water and the dose-rate above the water surface, the gamma-field above the water surface in 1951 was demonstrated to be mainly due to (95)Zr+(95)Nb. The dose-rate at the shore of the reservoir was calculated for the period 1949-1951. In November and December 1951, the gamma-field at the shore was mainly due to (140)Ba+(140)La. For the period 1949-1951, the external exposure of the Metlino population due to the decay of these radionuclides was about 200 R (2 Sv), most of the dose having been produced in 1951. The contribution of (137)Cs to external doses did at that time probably not exceed a fraction of several percent. This finding is in contradiction to the assumptions made in the most recent TRDS-2000 system that was developed to reconstruct the doses to the residents of the Techa river. The results presented here demonstrate that the reconstruction of external doses received by the Metlino population as well as by the Techa river residents can be improved for the most critical period between 1949 and 1954.     

The accumulation of the technogenic radionuclides by mushrooms in the area affected by the activity of the Krasnoyarsk mining-and-chemical industrial complex

The radionuclide content was measured in mushrooms collected in different sites situated in the zone of the radiation influence on the Mining-and-Chemical Combine at Zheleznogorsk and on the control site, near Krasnoyarsk, in 2002-2004. The analytical investigations of fruiting bodies of 12 mushroom species have revealed three gamma-emitting radionuclides: 7Be, 40K (natural) and 137Cs (artificial). It was found that only three species contain 7Be; activity concentration of 40K is not species- and site-dependent, averaging 1600 Bq/kg. All collected samples contain 137Cs, and its accumulation by mushrooms is species-specific. Suillus concentrates more 137Cs activity than other species and can be used as a bioindicator of soil contamination with radiocesium. The average activity concentration of 137Cs in Suillus granulatus collected in the sites subjected only to aerosol discharges of the MCC is more than twice higher than 137Cs content of the mushrooms collected in the control site--"Krasnoyarsk". The maximum activity concentration of 137Cs in Suillus samples collected in the sites that receive 137Cs with the flood water is an order of magnitude higher, amounting to 8624 Bq/kg. The analysis of the radionuclide distribution in a mushroom shows that 40K activity concentration is the same in caps and stems of Suillus, and 137Cs concentration in Suillus caps is 1.7-2.3 times higher than in stems. Binding of radionuclides by mushroom biomass was determined by chemical fractionation; it was found that the highest activities of 137Cs and 40K are in the exchange-adsorption fraction (56 to 71% of the total content of a radionuclide) and in the organic fraction (23 to 37%). Calculations were made for determination of the coefficients of 40K and 137Cs transfer from the soil to the fruiting body of Suillus.     

Uptake of natural and man-made radionuclides by lichens and mushrooms

Summary Due to the large absorbing surface of the mycelium that grows in the upper parts of the soil mushrooms take up higher amounts of¹³⁷Cs and⁴⁰K than lichens. Besides these nuclides only the long-lived radionuclides¹²⁵Sb and⁶⁰Co could be measured; but not the short-lived fission-products¹⁴⁴Ce,⁹⁵Zr and⁹⁵Nb which probably decayed before absorption into the mycelium. These nuclides, however, are present in lichens because of their surface structures which enable high foliar deposition.The¹³⁷Cs-content of lichens is probably due to absorption by the mycobiont and seems to be used to satisfy their potassium-requirements. Mushrooms on the other hand are characterized by a relatively stable potassium-content and a wide ranging¹³⁷Cs-content which depends on the availability in different substrates. Occasionally the natural radionuclides²³⁸U and²²⁶Ra could be detected in mushroom and lichen samples, showing no correlation with the natural radionuclide content of the soil.     

Biosorption of long lived radionuclides using immobilized cells of Saccharomyces cerevisiae

The efficacy of immobilized Saccharomyces cerevisiae (biomatrix) for the sorption of different metal ions and its potential applications in nuclear waste treatment were investigated. The sorption of radionuclides such as ²³³U, ²⁴¹Am, ¹⁴⁴Ce, ¹³⁷Cs and ⁹⁰Sr was studied under different experimental conditions. More than 95% sorption of UO₂ ²⁺, Pu⁴⁺, Am³⁺ and Ce³⁺ could be obtained in the pH range 1 to 2 of the aqueous solutions. However the sorption of Cs⁺ and Sr²⁺ were negligible under the similar experimental conditions. The infrared spectra and scanning electron microscopic images of the control and uranium-bearing biomatrix were studied to understand the chemistry of metal uptake by this biomatrix.     

Modification of 144Ce tissue deposition by mixed ligand complex treatment in mice

The individual effect of desferrioxamine-B (DFOA), Na3Ca-diethylene-triaminepentaacetic acid (DTPA), DL-penicillamine (PA) and Na-salicylate (SA) has been examined as well as the effect of mixed-ligand treatment on the retention and elimination of 144Ce in mice. It was found that 144Ce could easily be mobilized by a single dose of DTPA. Mixed-ligand (MLCs) treatment did not change the deposition characteristics and translocation kinetics of 144Ce.