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.

The environmental abundances of 129I and 127I in Lower Saxony, Germany, and their pathways to animals and man were investigated. The iodine isotopes are in severe disequilibrium in the different environmental compartments. Today, the environmental isotope ratios range from 10-6 to 10-10. The highest ratios were found in North Sea water, the lowest in deep soil samples and ground water. A differentiation by about a factor of ten between the iodine isotopes was observed for different air-borne iodine species. Time series for iodine in precipitation show a decade-long increase of 129I fallout until the 1990ties and an ongoing constant input of 129I with deposition densities of ~ 15 mBq m-2 per year. In surface waters, a dilution of the fall-out iodine takes place by stable iodine which is just weakly adsorbed in the soils. The isotope ratios in soils and ground waters demonstrate a high mobility and an accumulation of 129I in the water unsaturated soil zones and an efficient migration into water saturated soil layers and ground water. The transfer into the food chain is ruled by the complex situation in the water-soil system. Given the environmental 129I abundances, the relatively low 129I/127I ratios in human thyroid glands (2 × 10-9 - 3 × 10-8) can only be explained by additional iodine sources with low ratios in the diet.

In uranium mill tailings, oxides and oxi-hydroxides are responsible of about 70% of the radium immobilization, half being associated to amorphous forms (mainly iron and manganese oxides/oxi-hydroxides). With time, crystallization of these amorphous forms can occur, inducing a redistribution of radium between solids and solution. If the amount of mobile radium increases, the impact of these tailings on the environment may become significant. The aim of this study is to determine the amount of 226Ra released in solution during the crystallization process of hydrous ferric oxi-hydroxide (HFO) containing 226Ra. A reproducible co-precipitation procedure is developed. The transformation of Ra-HFO co-precipitate in crystallized forms (goethite, hematite, ...) is studied by ageing amorphous solids at 40$^{\circ}$C in different solutions. After co-precipitation, about 20% of the initial 226Ra present in solution is associated to amorphous HFO. At 40$^{\circ}$C, whatever the solution composition (MES or NaClO4), the solid evolution is very slow and, after 3-5 months, no significant amount of crystalline form is noticeable. Simultaneously, the amount of 226Ra present in solution is constant in MES and NaClO4 medium. In comparison, 226Ra sorption shows off inclusion of 226Ra in Ra-HFO precipitate.

We review collated data and available models for estimating the transfer of radionuclides to terrestrial biota within the European Arctic. The most abundant data are for radiocaesium and radiostrontium although many data for natural radionuclides are available. For some radionuclides no data are available for describing transfer to Arctic biota. Allometric-kinetic models have been used to estimate transfer for radionuclide-biota combinations. Predicted values were in good agreement with observed data for some radionuclides although less so for others. There are no bespoke models to enable the dynamic prediction of radionuclide transfer to Arctic biota. A human Arctic foodchain model has been adapted to estimate 137Cs and 90Sr transfer to some Arctic biota. There are many factors of Arctic ecosystems which may influence radionuclide behaviour including short growing seasons, prolonged soil freezing, and effects of low temperatures on biological rates. If exposure to ionising radiation in Arctic ecosystems is to be robustly predicted such factors must be fully understood and incorporated into models.

A number of frameworks have been proposed to assess the protection of wildlife from ionising radiations. In this paper we compare the predictions of transfer parameters recommended by one of these frameworks (FASSET) with observed whole-body 90Sr and 137Cs activity concentrations in a range of mammal and invertebrate species sampled within the Chernobyl exclusion zone. Predicted activity concentrations are generally within the observed ranges and mean predictions for reference organisms are similar to, or circa one order of magnitude higher than, the observed means. However, some predictions are more than one order of magnitude lower than observed values. No data were available for animals to test predictions for the other radionuclides released by the Chernobyl accident. In a separate paper the outputs of this assessment will be used to estimate doses to reference organisms and compare these to observed radiation induced effects reported within the Chernobyl zone.

In this paper we use the FASSET framework to estimate absorbed dose rates for biota within the Chernobyl exclusion zone. The estimated doses are compared to observed biological effects within the Chernobyl exclusion zone and effects expected from summaries of existing knowledge and the extent of contamination. Although paucity of observations under conditions of chronic irradiation makes direct comparison difficult, the biological effects observed in the Chernobyl exclusion zone over the period considered here (1988-2003) are broadly in agreement with those which may have been expected.

This paper presents a dynamic box model for the radionuclide behaviour in rivers on medium- and long-term periods (several days to several years). The river is described as a succession of boxes representative of its different reaches. In each reach, the compartments are the water column and three bottom sediment layers. Called interface, the first layer plays a fundamental role for the vertical exchanges of solid radionuclide phases between the water column and the sediment. The second layer results from the consolidation of the previous one. Its interstitial water is mobile and the dissolved radionuclide phases can be exchanged with the water column. It is called active. The last layer results from the consolidation of the active layer. Its interstitial water is slightly mobile and it is assumed that its dissolved radionuclide phases cannot be exchanged. It is called passive. In each compartment, the model computes the temporal evolution of the radionuclide activities in the main abiotic and biotic components. The abiotic components are the water and different matter classes classified according to their deposit kinetics. The biotic components are phytoplankton, zooplankton, and fish distributed in planktonivorous and omnivorous species, in water column and macrobenthos in bottom sediment.