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.

The ability to predict the consequences of an accidental release of radionuclides relies mainly on the level of understanding of the mechanisms involved in radionuclides interactions with different components of agricultural and natural ecosystems and their formalisation into predictive models. Numerous studies and databases about contaminated agricultural and natural areas have been obtained but their use to enhance our prediction ability has been largely limited by their unresolved variability. Such variability seems to stem from incomplete knowledge about radionuclide interactions with the soil matrix, soil moisture, biological elements in the soil and additional pollutants, which may be found in such soils. In this project, we investigated mainly the role of the biological elements (plants, mycorrhiza, microbes) in: radionuclide sorption/desorption in soils and radionuclide uptake/release by plants. Because of their chemical nature importance, the bioavailability of three radionuclides: caesium, strontium, and technetium have been followed. The role of one additional non-radioactive pollutant (copper) has been scrutinised. Role of microorganisms (Kd for caesium and strontium in organic soils is much greater in the presence of microorganisms than in their absence), plant physiology (changes in plant physiology affect radionuclide uptake by plants), the presence of mycorrhizal fungi (interferes with the uptake of radionuclides by plants), have been demonstrated. Knowledge acquired from these experiments has been incorporated into two mechanistic models CHEMFAST and BIORUR specifically modelling radionuclide sorption/desorption from soil matrices and radionuclide uptake by/release from plants. These mechanistic models have been incorporated into an assessment model to enhance its prediction ability. 


Zebrafish were exposed to different concentrations of waterborne uranium (0, 20, 100 and 500 μg U.L-1) and were sacrificed for blood sampling after different exposure periods (12h, 36h, 72h, 5, 10 and 20 days) in order to assess DNA integrity in erythrocytes, using the comet assay and flow cytometry. Concurrently, uranium bioaccumulation was studied in the remaining tissues to understand the potential genotoxic biomarker responses. Both genotoxic assays revealed significant effect of waterborne uranium on DNA integrity of fish erythrocytes. However, comet assay only succeeded in detecting such an effect after a 20-day exposure whereas flow cytometry analysis showed a uranium concentration effect for any exposure duration. Regarding uranium bioaccumulation, significant effects of both uranium concentration and exposure duration have been highlighted in this experiment.

Environmental radiation levels are modified in regions where the oil industrial activity is more aggressive, such as in the Zulia State and the Orinoco's Oil Belt. In these regions Venezuela is producing 1750 thousand barrels of oil from the near-to-the-surface or deep oil drilling, being its 2003 total OPEC market share 2932 thousand barrels of oil per day [1]. Petroleum constitutes an important source of energy and as the majority of natural sources it contains radionuclides and their disintegration products. The combustion of oil concentrates in the ashes those radioelements, which later enters the environment by different pathways producing adverse effects on the quality of man life. The concentration of radioelements varies greatly between oil fields, and then still requiring local survey studies in this area. Moreover due to the recent national interest in recycling processes, it becomes important to take care in the selection of materials that may contain by-products of industrial origin. In fact the oil ashes and other mining by-products are employable in the building industry. The concentration of radioactivity and heavy metals in crude oil, fuel oil N$^{\circ}$ 6 and the ashes from power plants were determined. The analysis includes the two major thermoelectric power plants in Venezuela, Ricardo Zuluaga on the northern seaside of Caracas and Planta Centro on the littoral of Carabobo State. The study covers different samples: fuel oil N° 6, heavy and medium petroleum as well as fuel Oil N°6 ashes. Gamma spectrometry was used for measuring 226Ra, 214Pb, 214Bi, 228Ac, 212Pb, 212Bi, 208Tl and 40K, and heavy metallic cations were determined by ICP-MS, which also allows the direct determination of 232Th and 238U. In this material (oil ashes) the total activity concentration is above 300 Bq.kg-1. Some criteria from the literature have been compared and used to investigate the applicability of oil ashes as an additive for building materials. The combustion concentrate also heavy metal cations, as is the case of Pb, Ni, Mn, V, Zn among others. The found high metal concentrations can represent an important environmental risk since the high amount of sulfates in the Venezuelan oil and ashes contributes to their dissolution and bioavailability.

In aquatic ecosystems, sediments constitute a reservoir for many of the most persistent chemicals that are introduced into surface waters. Sediments provide a habitat for various benthic macroinvertebrates, which could be exposed to sediment-associated chemicals both directly and via food intake. These organisms play an important role on the structure and the functioning of aquatic ecosystems. Among the non-biologically essential metals, data concerning uranium (U) fate and effects on freshwater benthic macroinvertebrates are sparse. The present study aimed at estimating effects of a chronic U exposure on Chironomus riparius larvae. To achieve this goal, a 10-d laboratory bioassay was performed exposing, via the sediment, first instar larvae to a gradient of U concentrations (0, 2.97, 6.07, 11.44, 23.84 μg U/g dry wt). Significant negative effects on mortality, development time and growth were detected at 6.07, 6.07 and 2.97 μg U/g dry wt, respectively. The results underlined a possible impact of U at the population level at environmentally occurring U concentrations. This study confirmed the need for more research on the role of U on benthic macroinvertebrate.

The metal bioaccumulation levels in target-organs associated with microlocalisation approaches at the subcellular level provide information for the understanding of the metabolic metal cycle. These findings could be used to select relevant biomarkers of exposure and to focus on specific contaminated organelles to study potential biological effects. Moreover, the metal accumulated in the cytosol fraction can be bound to macromolecules in order to be eliminated and/or to induce a potential cellular effect. Tissular distribution, transfer efficiency from water and subcellular fractionation were investigated on the freshwater bivalve, Corbicula fluminea after uranium aqueous exposure. The subcellular fractionation was performed while measuring associated uranium to each cellular different fraction as follows: cellular debris and nuclei, mitochondria and lysosomes, membranes, microsomes and cytosol. In our experimental conditions, the accumulation in the cytosol fraction was low and more than 80 % of the total uranium in gills and visceral mass was accumulated in the insoluble fraction. Main results presented in this paper come from light and electron microscope observations of subcellular fractions (nuclei/debris and lysosomes/mitochondria) in order to validate the efficiency of the fractionation technique. An adaptation of the fractionation technique is proposed. This set of data confirms high differences of fractionation efficiency as a function of used fractionation technique and organs/biological model.

Comparative analysis of water from natural reservoirs located near a place of the underground nuclear explosion with rock outburst (Perm region) and the radium production industry storage cell (Komi Republic) with contrast levels of radioactive and chemical contamination was performed for the first time using bioindication and chemical analysis. Bioindication was carried out with anaphase-telophase chromosome aberration assay on A. schoenoprasum L. meristematic root tip cells. Even at very low levels of specific activity, both natural (238U, 232Th, 226Ra, 210Po, 210Pb) and artificial (90Sr, 137Cs, $^{230,240}$Pu) radionuclides contribute significantly (59-91 %) to an induction of genotoxic and toxic effects. The chemical factors strengthened or weakened the cytotoxicity effects and may modify a formation of certain type of chromosome disturbances. Our results clearly indicate that combined exposure to metal ions and radionuclides at levels officially adopted as permissible for humans may act synergistically and result in significant damage to different biota species.


The global framework of this study is to go further in the understanding of the involved mechanisms of uranium and selenium internalisation at the subcellular level and of their toxicity towards several aquatic organisms. In this context, the applications and performances of a Scanning Transmission Electronic Microscope (STEM), which is fitted with a CCD camera and an Energy-Dispersive-X-Ray (EDX) analysis are reported. This equipment provides a direct correlation between a histological image (0.34 nm resolution) and a clear expression of element distribution. Demonstration of the usefulness of this method to understand the bioaccumulation mechanisms and to study the effect of the pollutant uptake at the subcellular level has been performed for target organs of a metal (U) and a metalloid (Se) in various biological models: a freshwater crayfish (Orconectes Limosus) and a unicellular green alga (Chlamydomonas reinhardtii)). TEM-EDX analysis revealed the presence of U-deposits in gills and digestive gland in crayfish. In the alga, the accumulation of Se was found in electron-dense granules within the chloroplast with ultrastructural changes and starch accumulation.

In the radiobiological studies of aquatic organisms, fish eggs are a favorite subject for experimental work because of easy availability of embryos and the possibility of observing the development of embryos within eggs. Data from Russian/FSU publications concerning the effects of ionizing radiation on the survival and development of fish eggs were compiled within the framework of the EC Project EPIC “Environmental Protection from Ionizing Contaminants in the Arctic" (2000-2003). Comparative analysis was performed for effects on roe of two representative fish species: cold-water fish salmon (Salmo salar), and pike (Esox lucius), which is widespread predatory fish from the temperate climatic zone.

Pinus sylvestris L. populations growing at the territory affected by nuclear waste storage facilities were monitored in 1997-2002. Cytogenetic damage levels within root meristem of seedlings significantly exceed corresponding controls. Populations experiencing man-caused influence have a higher seeds radioresistance and enlarged cytogenetic variance. These are considered as an indication of adaptation processes in the studied pine populations. An analysis of the structure of ecological-genetical variability is carried out. Changes of two components of the intrapopulational variance were studied in dependence on time and man-caused impact. The first component is engaged to the genetically determined variability of biological characteristics intrinsic for the species and is dominant in studied tree populations. The second is responsible for the variance originating from anthropogenic contamination of the natural habitat. A tendency of destabilizing dynamics and increasing mean values of intraclass correlation coefficient that is a measure of contribution from heterogeneity among trees into total cytogenetical variability is demonstrated under conditions of chronicle technogenic impact on pine populations.

A recent review of radiation effects data highlighted that information on the effects of low-dose, chronic exposure was, at best, fragmentary. These data are required to define the dose effect relationships, which must underpin assessments of the impact of ionising radiation on biota. In response, four Good Practice Guides (GPGs) have been produced as part of a protocol development framework that aims to harmonise experimental approaches, with a view to ensuring that appropriate endpoint data are collected and reliable dose effect relationships determined. The GPGs cover test species selection, endpoint selection, radiation exposure and experimental design considerations. A key guides researchers through the GPGs and the decisions made are recorded on a pro-forma, which is the basis of the experimental protocol. This paper describes the first application of the framework to a radiation effects study. The framework has been adopted by the UK Environment Agency as a document upon which future Agency-funded experimental work in this field will be based. It is hoped that the framework will gain acceptance in the wider scientific community and enable knowledge gaps to be addressed, in order that successful protection of non-human biota can be demonstrated.


Iodine-129 is a radionuclide of major concern in the international safety assessments for deep geological storage and disposal of nuclear waste because it migrates quickly through the geosphere to the biosphere and then from the soil to humans through the food-chain. However, in organic soils the 129I may be immobilized over a long time period, and so these soils represent a potential accumulation point in the biosphere. Effects of long residence times of iodine in soils are scarce. The present paper gives some insight on the aging of stable iodine under natural conditions. Stable iodine was introduced as KI in 1987 at the base of a sphagnum bog to simulate arrival of iodine via a groundwater discharge from the geosphere. Fifteen years later, the groundwater, the soil and the vegetation have been sampled and analysed for iodine. The results we present give insight on the mobility of “aged" iodine, the retention properties of the peat, and provide iodine transfer factors for native boreal plant species. This study demonstrates bogs present good sinks for iodine and limit the transfer of iodine to some of the “wildlife" food-chains.

The reported work aimed at modeling process of radionuclide migration from the near-surface waste burial (trench no.22) containing nuclear fuel particles to the unsaturated zone and aquifer. The developed global model of the waste site accounts for dissolution of reactor fuel particles, vertical radionuclide transport in the unsaturated zone, and horizontal transport in the underlying aquifer by advection-dispersion mechanisms. It is based on the following sub-models: the geostatistical model for radioactivity distribution in trench; the radionuclide source term model describing dissolution of fuel particles, radionuclide redistribution in the trench body and unsaturated zone (STERM1D) and the two- and three-dimensional contaminant transport in the aquifer (MODFLOW - MT3D). Modeling work included sensitivity analyses, calibrations and eventually validation tests for the global model by means of comparison of model predictions to experimental data. In addition, a preliminary step by step validation process was applied to “elementary" sub-models. The developed modeling methodology is mostly suited for producing spatially averaged parameter values (such as radionuclide concentrations in trench porous solution, integral radionuclide release to aquifer) and is applicable for long-term predictions on a scale of decades assuming that hydrological and geochemical conditions remain steady state.

Uranium and related decay-chain radionuclides remain important subjects of study for a number of reasons. Uranium has the potential to be chemically toxic near mining and processing facilities, and the decay-chain radionuclides can contribute substantially to radiation dose. Establishing an air quality standard for U in Canada has also been tentatively based on its accumulation and toxicity in soil. This paper summarizes two studies. The first investigated the mobility in soil, uptake by plants and ecotoxicity of U near a U refining facility. Because of the presence of co-contaminants, a large number of other elements were measured to fully characterize the samples. In general, the soil solid/liquid partition coefficients, Kd, for U were high enough that leaching is not a dominant process. Plant/soil concentration ratios (CRs) were not consistently different compared to background sites. The second study measured plant/soil CRs for 210Pb, 210Po, 226Ra, 228Ra, 228Th, 230Th, 232Th and 238U on a series of sites across Canada, with emphasis on background sites with possible human food-chain connections. Secular equilibrium was rarely observed, especially in plants.

The EC 3rd and 4th framework programs have produced several models and Decision Support System (DSS) in order to assess the radioactive contamination of terrestrial ecosystems. However a critical evaluation of such systems had not been undertaken. The EVANET-TERRA network has been established in order to perform such a task. A comprehensive methodology have been adopted; the uncertainty and sensitivity analysis have been performed in order to establish the differences between conceptual and constructed model, while the model-scenario comparison has been used to determine how the predictions fit empirical data. A synthesis of the current state-of-the-art regarding terrestrial radioecological models has been produced and recommendations have been made for further research needs.