In the frame of the IRSN Chernobyl Pilot Site Project, a waste trench containing hot particles was instrumented to study the fate of radioactive pollutants. Results have shown the formation of a 90Sr plume in the downstream aquifer, mainly present in the Aeolian layer after 15 years. Laboratories experiments were performed to analyse the transport of 90Sr and 137Cs in the Aeolian sand in both saturated and unsaturated conditions. Batch experiments were performed to study the chemical equilibrium state of the soil/solution system under static conditions. Stirred flow-through reactor experiments were performed to study the kinetics and reversibility of sorption reactions at the surface of solid particles under dynamic conditions. Column experiments in the structured porous media were also performed in saturated and unsaturated flow conditions. Experimental data pointed out a non-linear, instantaneous and reversible sorption process of 90Sr. 137Cs exhibits a non-linear behaviour with a partial irreversible sorption process. A suitable cation-exchange model was used to describe the solute/soil reactions. The former model was coupled with transport models to describe behaviour of 90Sr and 137Cs in both saturated and unsaturated steady flow conditions. Main transport parameters were identified and discussed. An effective simple Kd type approach to describe radionuclides transport properties under unsaturated conditions was evaluated

It is well known that the bioavailability of artifical radionuclides such as 90Sr, 137Cs and 239+240Pu in contaminated soils depends on the source term origin of the contamination. Altough the behaviour of the mentioned radionuclides in the soil is also influenced by the time passed from the contamination event and the characteristics of the contamination receiving soils. The objective of the present work is to analyse the different bioavailability and possible chemical-physical associations of 90Sr, 137Cs, and 239+240Pu in soils located in different Spanish ecosystems (Almeria and Cáceres provinces) by application of a sequential extraction procedure based on the NIST standard sequential extraction protocol. The resulting fractions obtained are: a) water soluble and exchangeable, b) associated to organic matter, and c) residual fraction. They will be studied jointly with the polluting sources (deposit of nuclear fallout-50s and 60s, Palomares accident in 1966 and the cesium release by Acerinox in 1998) in each ecosystem to interpret the observed behaviour of radionuclides.

The basis premise of many radiological assessments is the assumption that the transfer of many radionuclides from soil to herbage and hence animal derived food products is a positive linear relationship for a given set of ecological conditions. However, a number of authors have published results, which they conclude demonstrate non-linear transfer of radiocaesium to plants and animals with transfer being highest when soil concentrations are lowest. Whilst we may expect non-linear transfer of radionuclides under homeostatic control or present in comparatively large chemical quantities, there appears no credible hypothesis to support such an observation for radiocaesium. In this paper we review those articles, which have reported non-linear radiocaesium transfer and also analyse novel data. We argue that saturation of Cs uptake as suggested by some other authors is unlikely. Sampling bias, statistical data distribution and countermeasure application are suggested as potential contributors. However, we have not been able to provide a conclusive reason for such observations. Given the important implications for foodchain modelling further consideration of available data is required to more comprehensively answer this question

The nuclear accident that occurred in Palomares in 1966 caused the release of plutonium weapon grade particles into a Mediterranean ecosystem, and consequently, urban and farming areas were contaminated with this material. Several studies focused on the characterization and behaviour of transuranides have been carried out in the area. In this work, the solubility evolution of plutonium is analysed for a period of more than 30 years, as well as the influence that the incorporation of cow urine into organic fertilizers has on the solubility of the mentioned element. The average value of the plutonium solubility in water determined in five samples was 0.0082% in 1986. However, determinations carried out in samples taken in 1999 and 2000 indicated an increase of the plutonium solubility of two orders of magnitude. In order to check the influence of organic fertilizers on the solubility of plutonium, a solubility test was carried out using cow urine as extracting solution. The results show that the solubility of plutonium can reach a value equal to 14%, which is similar to the one obtained with sodium pyrophosphate acting as extracting solution. Thus, these results are a clear warning of what might happen if organic fertilizers are used in transuranic-contaminated soils.

99Tc and 79Se, two long-lived radionuclides, are supposed to be highly mobile in soils, because of their anionic forms. Their behaviours in the soil are often considered only from a physico-chemical point of view, although the microorganisms can affect either directly or indirectly their speciation. This study demonstrates the role of the microbial compartment in the retention of Se and Tc in soil by comparing experiments with soils constrained to different microbiological status (sterile / raw / amended). Kd coefficients for Se and Tc were determined in batch experiments, whereas transport of Se and Tc was investigated through column leaching experiments. Kd for Se was enhanced for the raw soil without amendment compared to the value obtained for the sterilised soil. The retention of Se was higher again in the amended soil. Besides, a biofilm, which can directly retain Se, was obtained at the entrance of the amended soil column. This effect was less obvious for Tc in batch experiments, but was revealed by leaching experiments where a high quantity of Tc was retained in the amended soil columns. These results give strong evidence that microorganisms are responsible for a greater retention of Se and Tc in soil.

In surface soils, the native physical and chemical properties of the abiotic components control most of the sorption-desorption processes. Moreover, micro-organisms may significantly modify the speciation of trace elements and/or radionuclides and subsequently determine their fate, to a large extent. Micro-organisms, mainly bacteria and fungi, develop many strategies that may affect indirectly or directly the behaviour of trace elements. Due to their activity, changes in the pore-water composition, e.g. pH, redox-potential, may occur in relation with organic acid production or solid phase alteration, reduction or oxidation of metallic oxi-hydroxides, and mineralization of organo-metallic complexes. Micro-organisms may also directly modify the speciation of radionuclides as a result of bio-accumulation in living cells, biosorption on cellular components, direct reduction or oxidation, biomethylation, etc. Each one of these microbial processes may either increase or decrease radionuclide mobility, depending on the element, the soil reactivity and the environmental conditions. The resulting effect of these processes is still poorly known. This literature review intends to present a comprehensive overview of the role of micro-organisms on radionuclide mobility. It aims at classifying these elements, regarding to their potential sensitivity to these microbial processes. It summarizes the theoretical effect of these mechanisms, resulting in a potential increase or decrease of the solid-liquid distribution. The environmental significance of such processes for various biogeochemical radionuclides cycles still remains to be confirmed by experiments. (This study is part of a research program supported by Andra).

This paper presents new data on concentration factors (CFs: concentration kg-1 biota/concentration l-1 seawater) for several marine species-radionuclide pairs, in three regions: coastal waters of Ireland, eastern Irish Sea and coastal waters of Norway. The CFs were estimated using data from long-term monitoring programmes, obtained for radiological protection purposes. The practical constraints of using such data sources are discussed. CFs were obtained for a range of fin fish, crustaceans, molluscs and brown seaweed, for one or more of the following radionuclides: 99Tc, 137Cs, $^{239,240}$Pu and 241Am. In general, there was a relatively high degree of variability in the values obtained, and it was not possible to discern systematic regional or time-dependent differences. However, for two datasets in the eastern Irish Sea (137Cs in winkles and crabs) and a number of datasets (137Cs in various species of fish) in the western Irish Sea there was a statistically significant increase in the CF over the monitoring periods. Significant gender differences were found for 99Tc in lobster. The results are compared with current IAEA recommendations and are discussed in relation to the influence of contemporaneous discharges and the possible impact of remobilised radionuclides on bioavailability.


Cellular growth and intracellular concentrations of selenite in the unicellular green alga Chlamydomonas reinhardtii showed considerable variability between replicates at ambient concentrations of Se that became toxic to the alga. However, growth inhibition was well correlated to the cellular quota of selenite; the correlation between absorbed selenite and toxicity was better than the simple correlation between ambient selenite and toxicity usually used to express metal toxicity, suggesting selenite toxicity is mainly linked to intracellular accumulation. It is usually expected that effects of contaminants on organisms depend on internal concentrations. These results confirm this hypothesis.

The fifth framework EU project BORIS (Bioavailability Of Radionuclides In Soils: role of biological components and resulting improvement of prediction models) had three scientific objectives. The first was to improve understanding of the mechanisms governing the transfer of radionuclides to plants. The second was to improve existing predictive models of radionuclide interaction with soils by incorporating the knowledge acquired from the experimental results. The last and third objective was to extract from the experimental results scientific basis for the development of bioremediation methods of radionuclide contaminated soils and to apprehend the role of additional non-radioactive pollutants on radionuclide bioavailability. This paper is focused on the second objective. The purpose of the BORIS assessment model is to describe the behaviour of radionuclides in the soil-plant system with the aim of making predictions of the time dynamics of the bioavailability of radionuclides in soil and the radionuclides concentrations in plants. To be useful, the assessment model should be simple and use only a few parameters, which are commonly available or possible to measure for different sites. The model shall take into account, as much as possible, the results of the experimental studies and the mechanistic models developed in the BORIS project. The adopted approach was to introduce in the assessment model a quantitative relationship between bioavailability of the radionuclides in soil and the soil properties. To do this an operational definition of bioavailability was proposed. Here, operational means experimentally measurable, directly or indirectly, and that the bioavailability can be translated into a mathematical expression. This paper describes the reasoning behind the chosen definition of bioavailability and how it was used in the assessment model.

The biogeochemical behaviour of americium in subsurface soils plays a dominant role on its potential migration, but is currently poorly known. This research investigates the relevant processes controlling americium biogeochemical speciation in the rhizosphere of an agricultural soil. Lixiviation tests were performed on columns packed with a calcareous soil contaminated with 241Am, under steady-state unsaturated or saturated hydric flow conditions. The columns were percolated with various soil solutions, containing citrate and/or glucose to simulate root exudates. The bio-physico-chemical parameters of the outlet solutions were monitored continuously. The percolation of a solution in equilibrium with the soil or containing low exudate concentrations (10-4 M) released less than 5 mBq/cm3 of americium. Poor remobilisations were also observed when injecting 10-2 M glucose solutions, despite effective glucose microbial degradation, production of secondary ligands, and important chemical changes. On the contrary, percolation of 10-2 M citrate solution released 1000 times more americium, in accordance with previous studies. 10000 times greater releases were observed when glucose was added to citrate at 10-2 M. The remobilisation of americium resulting from both dissolution of calcite and iron oxides, and complexation by citrate, as well as the applicability of simple parameterisation of partition coefficient are discussed.

A set of countermeasures aimed at reducing 137Cs uptake by plant products includes agrochemical measures based on changes in the soil properties after the application of ameliorants. The dynamic models for studying the effect of the application of potassium fertilizers and dolomite powder on 137Cs accumulation in plants are presented. Conceptual approaches to the development of models are based on the identification of mechanisms governing a complex of physico-chemical processes in soil after the use of ameliorants. The developed models were parameterized for soils of the coniferous forest located in the Bryansk region in area suffered from the radioactive fallout after the Chernobyl accident. Effects of ameliorants and time of their application on 137Cs behaviour in the soil-plant system are assessed. The contribution of soil chemical and biological processes to the decrease in the radionuclide uptake by plants is estimated.

The absorption behavior of technetium (Tc) and rhenium (Re) through plant roots was studied using nutrient solution culture. Radish samples, grown in culture solutions for 20-30 days in a greenhouse, were transferred into plastic vessels containing nutrient solutions contaminated with multitracer solutions including 95mTc and 183Re. The plant samples were grown individually for 1-7 days under laboratory conditions. The activities of radionuclides in nutrient solutions and oven-dried plant parts (roots, fleshy roots and leaves) were measured with Ge detecting systems. The concentrations of 95mTc and 183Re in the nutrient solutions after harvesting the plants were almost the same as those in the initial solution, though about 2 mL of the nutrient solution was lost per day per plant pot due to transpiration. Possibly, the radionuclides were taken up with water through the plant roots. The distributions of Tc and Re in the plants showed no differences, thus, soluble Tc and Re absorption mechanisms by plant samples were the same. It is suggested that Re could be used as a geochemical tracer for Tc in soil environments.

It is important to obtain local transfer factors (TFs) of long-lived radionuclides for assessment of radioactive waste disposal, because climates, soil types and vegetation can affect TFs. Global fallout 90Sr and 137Cs are good tracers to obtain the TFs under natural conditions, however, their radioactivity levels in plants are extremely low. To close the gap, analyses of stable isotopes and natural radioisotopes in rice and wheat grains and their associated soils collected throughout Japan were carried out in order to obtain TFs under equilibrium conditions. We focused on rice and wheat, because the consumption of cereals is very high in Japan and other Asian countries. About 40-50 elements such as Cs, Sr, Th and U in plant and soil samples were measured by ICP-MS and ICP-OES. From the data, TFs of stable elements were calculated; among the values, TFs of Cs and Sr for rice and wheat were compared with the TFs of 137Cs and 90Sr. Using the elements' concentrations data, we proposed a `Reference rice' (brown rice and polished rice) and a `Reference paddy soil' to provide elemental composition data which can serve as reference values in mathematical transfer models and which allows the comparison of data for other crops.

In this work TF values for 90Sr and 137Cs were measured for reference plants grown in lysimeters containing soils representative of large agricultural areas in Brazil: Ferralsol, Nitisol and Acrisol. These results were discussed in the light of pedological analyses and results from the follow sequential chemical extraction protocol: 1) slightly acidic phase containing readily bioavailable elements; 2) easily reducible phase containing elements bound to Mn oxides; 3) oxidizable phase containing elements bound to labile organic matter; 4) alkaline phase containing mainly elements bound to Fe compounds; 5) resistant phase not potentially available to crops. These results showed that the main soil factors influencing the 137Cs transfer to these soils were: exchangeable K, organic matter and iron oxides content. These results showed that 90Sr plant uptake was influenced by exchangeable Ca. All these finds are in accord with previous studies and seems confirm the vulnerability of Ferralsol and Acrisol to 137Cs contamination


There is a need to confirm that the environment is being adequately protected from the contaminants released into it. In the field of environmental radioactivity, modelling and assessment tools are being developed to assess the impact of ionising radiation on wildlife. There is also a need to fill gaps in the scientific data upon which these assessments are based. New documentation has been produced by the UK Environment Agency to provide guidelines on structuring experiments (using environmentally relevant chronic doses) and on selecting suitable non-human species and endpoints for study. It is anticipated that this documentation will be used to direct future experiments. This paper presents the results of the first of these experiments on chronic low-level radiation exposure on soil fauna. Soil fauna species the earthworm Eisenia fetida and the woodlouse Porcellio scaber were segregated and continuously exposed to one of six radiation doses (background, 0.2, 0.4, 1.5, 4.0 and 8.0 mGyh-1) for a total of 16 and 14 weeks respectively. The endpoints of mortality, number of viable offspring and average weight of an individual were recorded. This paper presents the results for Porcellio scaber.

The objectives of the present work were (1) to estimate the bioaccumulation of natural uranium (U) in a representative freshwater fish and (2) to assess the response of parameters involved in the defense against reactive oxygen species, in relation with the metal concentration and the exposure duration. Juvenile rainbow trout (Oncorhynchus mykiss) were exposed to a range of U concentrations in water (20, 100 and 500 μg U l-1) during 10 days. The activity of antioxidant enzymes superoxide dismutases (SOD) and catalase were measured in trout liver. In parallel, U analysis were performed in water and in trout gills. A significant accumulation of U occurred in trout gills in relation with the concentrations of U in water. SOD and catalase activities were both decreased by the exposure to U. U seemed to partly inhibit the antioxidant system of trout, indicating a potential enlarged sensitivity of exposed fish to oxidative damages. 


Results of laboratory, “green-house" and long-term field experiments carried out on different plant species (spring barley, Scots pine, bulb onion and others) to study ecotoxical effects of low doses and concentrations of such common environmental factors as acute and chronic g-radiation, heavy metals, pesticides, artificial and heavy natural radionuclides, are presented. Special attention is paid to ecotoxic effects of chronic low dose exposures, synergistic and antagonistic effects of different factors' combined action. The results of long-term field experiments in the 30-km Chernobyl NPP zone and in the vicinity of a radioactive wastes storage facility are discussed. The data presented suggest that the further evolution of investigations in this field would issue in the development of a theoretical bases and practical procedures for environmental protection against radioactivity, taking into account the new experimentally confirmed facts about the presence of such essentially important singularities as the nonlinearity of a dose-effect relationship, radiation-induced genomic instability, phenomenon of radioadaptation, increased probability of synergetic and antagonistic effects of the combined action of different nature factors.

This work aims at determining early effects of uranium on the green microalga Chlamydomonas reinhardtii. First, the global effect on growth rate inhibition of exponentially-growing cultures was assessed on favourable conditions for uranium bioavailability (e.g. pH=5), EC50-24hrs equals roughly to 150 nM whatever the uranium isotopic composition considered (depleted U or 233U). Then, the sensitivity of different parameters representative of (i) oxidative stress (GSH/[GSH + 0.5 GSSG] ratio) (ii) metal detoxifying (phytochelatins production) and (iii) photosynthetic activity (chlorophyll fluorescence) was tested. Setting assay of different forms of glutathione and phytochelatins by HPLC was firstly optimised with cadmium-contaminated cells. This assay completed by chlorophyll fluorescence and algal growth was subsequently applied on samples contaminated by 150 nM of depleted uranium or 233U. No phytochelatin was produced in our experimental conditions. No difference of GSH/[GSH + 0.5 GSSG] ratio was shown between control and contaminated algae. This result suggests that the algae could be stressed before contamination due to culture condition. Chlorophyll fluorescence measurement showed photosynthetic activity inhibition after 24 hrs, in the same way for depleted uranium and 233U. Thus, the effect observed on the photosynthetic activity could be mainly attributed to the chemical toxicity of the metal.