Association of Chernobyl-derived 239+240Pu, 241Am, 90Sr and 137Cs with different molecular size fractions of organic matter in the soil solution of two grassland soils

Radiocesium is normally bound only rather weakly and unspecifically by humic substances, in contrast to the actinides Pu and Am. Recently, however, it was observed that fallout ¹³⁷Cs in the soil solution from an Of-horizon of a podzol forest soil (slightly decomposed plant material) was associated essentially only with one single size fraction of the humic substances. In deeper soil layers with well humified material (AOh-horizon), radiocesium was associated with all size fractions of the dissolved organic matter (DOM). To examine whether this unexpected behaviour is also observable for DOM isolated from other soils, we determined the association of fallout ¹³⁷Cs,⁹⁰Sr,²³⁸Pu, ^239+240Pu and ²⁴¹Am with various size fractions of DOM from in situ soil solutions isolated from two layers (0–2 cm and 2–5 cm) of two grassland soils (a soddy podzolic soil and a peat soil) within the 10 km zone of the nuclear reactor at Chernobyl (Ukraine). The four size fractions of DOM as obtained by gel filtration of the soil solution were (mean nominal molecular weight in daltons): fraction I: ≥2000, fraction II: 1300; fraction III: 560, fraction IV: inorganic compounds. The results for the well humified DOM (humus accumulation horizon of podzol, deeper layer of peat soil) showed that Pu and Am are essentially associated with the high molecular weight fractions, while Sr is present only in the `inorganic' fraction. Radiocesium is found in all the size fractions separated. A quite similar pattern was also found for Pu, Am, and Sr in the soil solution from only slightly decomposed plant material (0–2 cm of peat soil), but not for radiocesium. This radionuclide was again essentially only observable in one single low molecular weight fraction of DOM. The above results thus support our recent observations in the different horizons of a forest podzol mentioned above, even though no reason for the different binding of radiocesium by well humified soil organic matter and by only slightly decomposed plant material can be given at present. The data demonstrate, however, that information on only the total amount of a radionuclide in the soil solution will not be sufficient to interpret or predict its fate adequately in the soil. Received: 13 February 1998 / Accepted in revised form: 14 July 1998     

90Sr, 137Cs, 238Pu, 239+240Pu,and 241Am radionuclides in macrophytes within the Krasnensky flood plain: species specificity of concentration and distribution in phytocenosis components

The analysis of the content of radionuclides 90Sr, 137Cs, 238Pu, 239 + 240Pu and 241Am in water vegetation of flood plain reservoirs has allowed studing features of radionuclide accumulation by various species of macrophytes and revealing bioindicators of radionuclide contamination. Thus species-specificity of radionuclide accumulation can essentially change the contribution of different species to a percentage ratio of the radionuclide content in phytomass of reservoirs in comparison with fund of higher aquatic plants.     

Long-term effects of combined exposure to external 137Cs gamma-radiation and incorporated 239Pu

A study was made of the delayed effects of mixed exposure to 137Cs-gamma-radiation (a single exposure) and 239Pu (a single intravenous injection) in doses approximating optimal blastomogenic ones. The results are calculated per 1 cGy of weighted mean dose within the body with regard for RBE (1 cSv), per cent of osteosarcomas (per 1 cGy in endosteum and periosteum). A conclusion is made of a complete summation of main biological effects per 1 cSv of the dose absorbed.     

Plutonium,241Am,90sr,and137cs concentrations in some antarctic matrices

A radioecological survey in Antarctica shows that the^239+240Pu,²³⁸Pu,²⁴¹Am,⁹⁰Sr, and¹³⁷Cs activities were detectable in nearly all the samples. The activity level of^239+240Pu,²⁴¹Am, and¹³⁷Cs in antarctic sediments was about 5–20 times lower than in the northern Adriatic Sea sediments, but the²³⁸Pu activities were relatively high. It was interesting to note that the⁹⁰Sr concentrations in all the sediments tended to be low, which could be the result of the easier exchangeable behavior of⁹⁰Sr in water. High concentrations were detected in mosses and lichens and their activity levels were comparable to those in central Italy. The radionuclide ratio analyses show that the major part of^239+240Pu,²⁴¹Am,⁹⁰Sr, and¹³⁷Cs was a result of nuclear weapon tests. The higher²⁴¹Am/^239+240Pu ratio was observed and it could perhaps be the result of fallout of nuclear weapon tests prior to 1962. The²³⁸Pu/^239+240Pu ratio in the antarctic matrices was about seven times higher than in the Northern hemisphere and it could be inferred that the major part of²³⁸Pu was originating from the SNAP-9A satellite accident.     

Self-renewal capacity of murine hemopoietic stem cells under internal contamination with239Pu and241Am

Summary The self-renewal capacity of murine pluripotent hemopoietic stem cells (CFU-S) of vertebral bone marrow was studied under conditions of short-term and long-term internal contamination with²³⁹Pu or²⁴¹Am in female mice. Measurement of the CFU-S self-renewal capacity was carried out using double transplantation assay. To evaluate the production of differentiated progeny of stem cells average erythroblast numbers/visible spleen colony and⁵⁹Fe-uptake/colony were computed. The marrow cellularity/vertebra and the number of CFU-S/vertebra were decreased and affected more by²³⁹Pu than by²⁴¹Am. The production of erythroblasts per a single CFU-S and the⁵⁹Fe-uptake/colony were reduced, similarly the numbers of secondary spleen colonies and of secondary CFU-S in primary colonies. The above changes resulting from impaired functions of surviving CFU-S were more serious with²⁴¹Am than with²³⁹Pu. The biological effects of plutonium and americium appeared independent of the phase of contamination.     

Determination of soil-to-plant transfer factors of 137Cs and 90Sr in the tropical environment of Bangladesh

Soil-to-plant transfer factors (TF) of ¹³⁷Cs and ⁹⁰Sr have been determined for different plants/crops, such as rice, beans, peanuts, pineapple, cabbage, tomato, spinach and grass. They were obtained from radioisotope experiments on plants grown in pots under outdoor ambient tropical conditions for three growing seasons (1994–1996). In the case of ¹³⁷Cs and concerning the above mentioned plants/crops, the average TFs were found to be 0.28, 0.25, 0.77, 0.19, 0.23, 0.28, 0.59 and 0.18, respectively. In the case of ⁹⁰Sr, the average TFs were found to be 0.82, 0.51, 0.20, 0.82, 0.69, 0.59, 0.91 and 0.84, respectively. A minor seasonal variation was observed. This study provides a database of TFs for tropical environments to be used, e.g., for radiological safety assessment models. Received: 14 October 1997 / Accepted in revised form: 9 February 1998     

The optimization of the soil acidity of agrocenosis contaminated 137Cs and 90Sr: threshold parameters

During the field researches were determined the differences between agrochemical optimum of the acidity of the Sod-podzol loamy sand soil, which provides high productivity of the crops and the pH-value, which provides the minimal accumulation of 137Cs and of 90Sr by the biomass (the ecological optimum). On the average for the majority of the agricultural plants the minimal accumulations of 137Cs and of 90Sr are noticed under pHKCl 6.7, which is higher than agrochemical optimum on 0.7. The efficiency of liming under the discrimination of 137Cs and of 90Sr is much higher in soils with low values of pH. On the average, in crop rotation due to decreasing of the acidity in the soil from 4.9 to 5.9 pHKCl, the crop yield has grown on 9%, 137Cs contents has decreased on 16.7%, 90Sr--on 23.7%. The further decreasing of the soil acidity (from 5.9 to 6.8 pHKCl) was poorly effective: the productivity didn't change essentially. The transfer of 137Cs decreased on 8.9% and of 90Sr on 8.4%.     

Studies on the lysosomal binding of 141Ce, 239Np, 239Pu and 241Am in rat and syrian hamster liver using carrier-free electrophoresis

The binding of ¹⁴¹Ce, ²³⁹Np, ¹³⁹Pu and ²⁴¹Am in the liver of rats and Syrian hamsters, following injection in essentially monomeric form, was analyzed by carrier-free electrophoresis at 4–9 days and several months after radionuclide injection. In contrast to density gradient methods lysosomes can be clearly separated from other cell organelles by carrier-free electrophoresis. These, and previous results from this and other laboratories confirm that lysosomes are the main initial binding site for these four radionuclides in the livers of rats and Syrian or Chinese hamsters. Light microscopic autoradiography showed that at all the time intervals studied ²⁴¹Am was more or less uniformly distributed in the liver of all three species. Thus, the changes in the electrophoretic pattern of the nuclides, observed at later time periods in hamsters, cannot be explained by gross redistribution phenomena such as accumulation in macrophages.     

The analysis of coefficient of 137Cs transfer from soil into potato in relationship with 137Cs content in soil and plant mineral feed

The soil-potato transfer factor for 137Cs (TF) was estimated by using results of 137Cs activity concentration measurements in 214 samples of soil and potato taken at fields with various level of contamination with 137Cs. The relationships between the coefficient TF and soil characteristics (acidity pH (KCl), content of K2O, P2O5, CaO and MgO in soil) and soil contamination with 137Cs have been analysed. The results show that the TF values tend to decrease with increasing concentration of 137Cs, K2O, P2O5, and CaO in considered sod-podsolic sandyloam soil. The regression function describing the TF dependence of 137Cs, K2O, P2O5, and CaO content in soil has been derived.     

137Cs and 90Sr distribution peculiarities in soil and accumulation by pine tree wood and bark depending on edaphotops

The range of researches was made on 137Cs and 90Sr distribution regularities in pine tree plantations depending on different edaphic conditions. It is shown that total radionuclide amount in the forest litter depends on its thickness and is thought to be 10 to 70% for 137Cs and 20 to 60% for 90Sr. When soil fertility come increases from trophotop "A" to "C", 137Cs and 90Sr transfer factors for wood reduce. Soil humidity increase for each grade of trophic net results in increase of 137Cs transfer factors to wood and decrease for 90Sr. Total activity of 37Cs and 90Sr in pine wood plantation depends on plantation productivity and radionuclide transfer factors depending on different plantation conditions. In the most prevailing edaphotops pine wood accumulates 1-3% of 137Cs and 6-11% of 90Sr from total activity of radionuclides in biogeocenosis.     

Influence of clay mineral type and organic matter content on the uptake of239Pu and241Am by plants

Summary The uptake of²³⁹Pu and²⁴¹Am from different clay mineral-organic matter-sand mixtures simulating contrasting soil types was examined in growth chamber experiments. The mixtures represented various combinations of organic matter (0, 5 and 10%), kaolinite (11 type) and montomorillonite (21 type) clay minerals, each at the levels of 5, 10 and 25%, and purified quartz sand (as filler).Results indicated a marked reduction in uptake of both²³⁹Pu and²⁴¹Am with increase in organic matter as well as clay content of the mixtures. The Pu Concentration Ratios (CRs) ranged from (2.5–7.0)×10^–3 in the case of kaolinite-organic matter mixtures, and from (0.9–5.5)×10^–3 in the case of montmorillonite-organic matter mixtures. The corresponding values of Am Concentration Ratios (CRs) obtained were (1.9–725.4)×10^–3 in the case of kaolinite-organic matter mixtures, and between (0.7–3.5)×10^–3 for the montmorillonite-organic matter mixtures.Reduction in the uptake of²⁴¹Am with increasing clay content was more pronounced in the montmorillonite clay-organic matter mixtures as compared to that in the case of kaolinite-organic matter mixtures. While similar qualitative reduction in²³⁹Pu CRs with increasing clay content was observed, the reduction was less marked than in the case of²⁴¹Am. The values for Am CRs were higher than the corresponding Pu CRs in kaolinite based mixtures whereas in the case of montmorillonite-organic matter mixtures Pu CRs exceeded the Am CRs.Increasing organic matter content and its interaction with both kaolinite and montmorillonite clay minerals were found to be equally effective in reducing the uptake of²³⁹Pu as well as²⁴¹Am by plants.     

Comparative assessment of the danger of inhaling 239Pu and 241Am based on the degree of leukopenia in dogs

From the analysis of the results of examination of 96 dogs it is concluded that the estimate of a relative danger of breathing transuranium radionuclides with different metabolism rates (polymeric 239Pu and monomeric 241Am), according to degree of leukopenia is more reliable when it is compared with a mean weighed dose per whole organism than the dose per individual "critical" organ.     

Comparison of the accumulation of 137Cs and 90Sr by six spring wheat varieties

The uptake of ¹³⁷Cs and ⁹⁰Sr by six varieties of spring wheat (Triticum aestivum) was compared in field trials on land contaminated by the Chernobyl accident. All the experimental varieties are officially adopted for agricultural use in Belarus and are used in large-scale production. Under identical conditions of nutrition, the productivity of the varieties varied significantly by a factor of 1.3. The extent of ¹³⁷Cs and ⁹⁰Sr accumulation by wheat grain, quantified as the concentration ratio, differed between the varieties by as much as a factor of 1.6, for both radionuclides. There was a significant linear positive correlation between the ⁹⁰Sr activity concentration in grain and straw, and the calcium concentration. The correlation between ¹³⁷Cs and potassium was not significant. The results suggest that certain varieties of spring wheat used in normal agricultural practice accumulate less ¹³⁷Cs and ⁹⁰Sr into grain than others. Some spring wheat varieties accumulated relatively less ¹³⁷Cs, but did not accumulate less ⁹⁰Sr. One variety, Quattro, had a significantly lower uptake of both ⁹⁰Sr (for grain) and ¹³⁷Cs (for both grain and straw) than that of the other varieties tested. The reduction efficiency achieved by the use of these varieties, however, is not as high as that achieved by soil amelioration techniques in the past. Nevertheless, since there are no additional costs or production losses associated with these varieties, their use in the contaminated areas is worth considering as a simple, practical, and effective contribution to reducing the uptake of both ⁹⁰Sr and ¹³⁷Cs and allowing farmers to produce food-grade grain.     

Radiosensitivity and proliferative activity of vertebral CFU-S surviving in mice injected with oncogenic activities of 239Pu or 241Am

Survival, radiosensitivity and capability to produce differentiated progeny were followed in CFU-S from lumbar vertebrae of mice injected with 198.6 kBq 239Pu/kg or 208.6 kBq 241Am/kg. The CFU-S assay and 59Fe uptake into spleen colonies were used. The number of CFU-S from treated mice was significantly lower than in controls. Higher radiosensitivity of CFU-S from 239Pu- or 241Am-treated mice was demonstrated using additional exposure to 0.5 Gy X-rays 1, 24, 48, 72 hrs after cell transplantation and expressed more precisely by survival curves obtained 1 hr after the marrow cell injection. The effect of 239Pu on CFU-S was characterized by Do 0.58 Gy (n = 0.91) and that of 241Am by Do 0.64 Gy (n = 0.91); corresponding control values were Do 0.89 Gy, n = 1.11. Lower iron utilization due not only to the decreased CFU-S numbers, but also to the defective production of erythroid cells per one CFU-S was found. Complexity of radiation effect on hemopoietic stem cells was demonstrated by the present study.     

The accumulation of radionuclides 137Cs and 90Sr by different kinds and grades legumes crops

The decision of protein problem on contaminated by radionuclides territories as a result of the accident on Chernobyl NPP is not possible without increase of the sowing areas legumes crops (peas, lupine, soybean). Introduction in agricultural manufacture of grades with a low level of accumulation radionuclides (peas--Aist, Polesskay, Gomelskay Agat; soybean--Severnaya zvezda, Mageva) will allow to receive agricultural production adequate "Republican allowable levels of the contents of 137Cs and 90Sr in agricultural raw material and forages" on arable lands at their higher density of radioactive contamination: 137Cs--1300-1480 kBq/m2 (35.0-40.0 Ci/km2): 90Sr--18.5-37.0 kBq/m2 (0.50-1.00 Ci/km2).