Gis and Radioecology: A Data Perspective

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10th EC GI & GIS Workshop, ESDI State of the Art, Warsaw, Poland, 23-25 June 2004

GIS AND RADIOECOLOGY: A DATA PERSPECTIVE G. Dubois1, T. Tollefsen1, P. Bossew2, M. De Cort1, 1

Emissions and Health Unit, Institute for Environment and Sustainability, Joint Research Centre Directorate, European Commission, Ispra, Italy 2

Department of Physics and Biophysics, University of Salzburg, Austria

ABSTRACT Geographic Information Systems (GIS) have proven to be very valuable tools in radioecology. After the Chernobyl nuclear power plant accident, GIS have been further developed and used to describe deposition patterns, quantify levels of radioactivity and model the transfer of radionuclides in various ecosystems. Radioecological models rely, among other parameters, on transfer factors (TFs), which are defined as the ratio of the concentration of a radionuclide in a receiving compartment to the concentration in the source compartment. Consequently, the ability of these models to predict correctly the behaviour of radionuclides in the environment depends not only on a correct description of these compartments by means of thematic maps, but also on a correct definition of a number of variables that affect the transfer and that are also derived from these maps. By reviewing a few GIS developed in the field of radioecology, we here discuss the use and needs of the main thematic maps involved in radioecological modelling, with an emphasis on the prediction of radionuclide concentrations in the human food-chain at the European scale. KEYWORDS: Radioecology, decision support systems, thematic maps INTRODUCTION The major part of radioactive fallout deposited onto the ground after the Chernobyl accident (April 1986) remained close to the soil surface due to its very slow vertical migration in most soils. This is particularly true for 137Cs, which is the most important radionuclide as far as long-term doses to humans are concerned, given the fallout composition in central and western Europe (in regions of Ukraine, Belarus and Russia closer to Chernobyl this is different due to the much higher contribution of 90Sr, Pu and 241Am). Therefore, in most undisturbed soils, even 18 years after the accident, most 137Cs is located in the upper 10 cm of soil. (90Sr usually migrates much faster.) This slow migration of 137Cs can be caused by its fixation by clay minerals which have a high sorption capacity for Cs, or by its residence (often cycling) in the organic top layer of soil, litter and humus in forests, the carpet-like root zone typical for upland and alpine environments, or the lichen carpet in tundra ecosystems. While the former type of fixation keeps the Cs largely away from biosphere, the latter type can lead to a high bio-availability; well-known examples of relatively high contamination of human foodstuff are wild mushrooms, alpine raw milk and the tundra food chain (Skuterud et al., 1997; Fesenko et al., 2001; Howard et al., 2002). Natural ecological processes, such as erosion and run-off, and human activity, such as irrigation and ploughing, further contribute to the redistribution of radionuclides in the environment. Hence, in the case of a nuclear accident, appropriate countermeasures take into account the regions where the contamination levels exceed a critical threshold as well as those

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areas where the bio-availability of the radionuclides within the ecosystem is enhanced. The identification of more “vulnerable” regions is essential, not only because food concentration levels of radionuclide activity that are above those permitted remain a problem of actuality (wild mushrooms, berries and game regularly show higher radioactive levels), but also because it would allow decision-makers to identify, anticipating a certain accident scenario, the regions where the contamination of the human food-chain might be higher. The obvious need for new radioecological tools that are able to handle thematic maps and the clear transboundary character of the radiological consequences of the Chernobyl accident have motivated the European Commission to fund a number of radioecological projects in which Geographic Information Systems (GIS) have played a key role. The outcome of these projects has shown that GIS can not only help to delineate contaminated areas in Europe, but also aid in understanding the fate of the radionuclides within the human food-chain. In a recent workshop, Semioshkina et al. (2003) presented a thematic network called EVANET-TERRA whose main objective is to assess and compare the various decision support systems developed in terrestrial ecology. This should help to identify the relative weaknesses and strengths of these tools and later facilitate the integration of the best features into a harmonized and coherent unique product. Given the evaluation of models and functionality found in these tools, we feel that the choice and use of the thematic maps involved should also be evaluated, since these are deeply involved in the modelling and thus influence the decision-making process. Hence, it is the purpose of this presentation to review the GIS developed in the field of radioecology from another perspective, namely, from the data. Briefly summarised, the main projects in which these GIS were developed during the 4th Framework Programme are: SAVE (Spatial Analysis of Vulnerable Ecosystems in Europe): a raster GIS was developed for predicting fluxes of radiocaesium (137Cs) into European foods. A number of environmental variables that affect the overall transfer of these radionuclides into the food chain were incorporated within a decision support system. (Howard et al., 1999). RESTORE (Restoration Strategies for Radioactive contaminated Ecosystems): conceptually similar to SAVE, this project involved a different raster GIS and has focused mainly on CIS countries. The implemented models were furthermore covering others aspects of radioecology such as the 137Cs redistribution as a result of both overland flow-induced soil erosion and soil translocation due to tillage (van der Perk et al., 2000, 2001). CESER (Countermeasures: Environmental and Socio-Economic responses): it focused on the assessment of radioecological countermeasures, such as deep ploughing, application of special fertilisers, changes in the feeding of livestock or even changes in land use, that are taken in case agricultural land is contaminated (Salt et al., 2000). RODOS (Real-time On-line Decision Support system for off-site emergency management in Europe): this project is certainly the most ambitious one. It aims to cover all aspects of decision making in the case of nuclear power plant accidents, even at the broadest spatio-temporal scales: from the first minutes of an accidental release up to the long-term management of contaminated territories. Models and data bases of RODOS can be customized to handle different sites and plant characteristics as well as geographical, climatic and environmental

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variations in Europe. Its operational application requires on-line coupling to radiological and meteorological real-time measurements and meteorological forecasts from national weather services (Ehrhard et al., 1997). Expected to benefit from the experience gained in the above three projects, RODOS is still ongoing and will not be further discussed here (for more information, see http://www.rodos.fzk.de/). The INTAS project 94-2361 was independent from those mentioned above. It is cited here since it had a non negligible impact on the strategy usually chosen to prepare deposition maps. With the title “Soil pollution: cartography, risks, decision support systems”, this project focused on the implementation of more advanced interpolation techniques, mainly geostatistical functions and stochastic simulations, in a radiological decision support system (Arutyunyan et al., 1996). Only very recently have such functions been implemented in the major GIS. Obviously all these projects have very much in common: the GIS developed are mainly raster-based and share a similar design. We have identified the maps and derived variables used by these GIS, either by using the tools directly and/or through the various progress reports of the projects. Table 1 lists the spatial data sets used as well as their main characteristics. From this table one will find very similar needs in terms of thematic maps: to run the models one would need information about radioactive deposition levels, soil types and land usage. However, these maps have different sources or vector maps have been rasterised in different ways and may therefore not provide the same information and/or have the same uncertainties. Table 2 summarizes the formats of the output maps from the tools. These models also use other non-spatial information such as dietary habits, but their use and relevance are not further explored in this context. To further assess the needs as well as the impact of these spatial data sets in the field of radioecology, we present briefly the fundamentals of terrestrial radioecology in the following chapter. Theme/property 137 Cs deposition Soil map - source - year - extent - scale/detail Soil properties - soil texture - clay content - organic matter content - pH - exchangeable K+ - Ca - phosphate (P2O5) - bulk density Land cover/land use - source - year - input data

SAVE European Atlas of 137 Cs deposition European Soil Database European Soil Bureau 1998 EU-25+ 1:1,000,000

RESTORE European Atlas of 137Cs deposition Various UA, BY, RU sources 48 areas of UA, BY, RU

Yes Yes (from soil map) Yes (from soil map) Yes (from soil map) Yes (from soil map) Yes (from soil map)

Eurasia Land Cover USGS-EROS Data Centre 1992-1993 NOAA AVHRR

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CESER Simulated data Coverage of different soil types found in Scotland Macaulay Land Use Research Institute Variable Scotland 1:25,000 – 1:50,000

Yes Yes Yes Yes Yes Yes Yes Land use Various

Land cover The Scottish Office 1988

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- extent - scale/detail Elevation - source - year - extent - scale/detail - vertical detail - vertical accuracy Administrative boundaries - source - year - scale/detail

Pan-Europe 1 km x 1 km

Scotland 1:25,000 Elevation contours The Ordnance Survey Variable 1:10,000 5-10 m contour intervals Parish boundaries Digitised from maps Maps >50 years old 1:250,000

Table 1. Thematic maps used by decision support systems used in radioecology

Risk/impact maps - extent - resolution

SAVE EU-15 + NO 5 km x 5 km

RESTORE Cs-contaminated zone of UA, BY, RU 1 km x 1 km

CESER 9 Scottish catchments 10 m x 10 m

Table 2. Output maps of the decision support systems used in radioecology

RADIOECOLOGY AND MODELLING Much of the work done in the field of radioecology has been compiled and published in two major books edited by Warner and Harrison (1993) and Kirchmann and Van der Stricht (2001). We refer the reader to these books for further information about the information presented hereafter. Atmospheric release Ecological models are generally constructed around a structure that is defining the relationships between the various compartments involved. In the case of an accidental release of radionuclides in the atmosphere, the most probable contamination scenario in Europe is a terrestrial transfer of radionuclides into the human food-chain rather than an aquatic one. Consequently, most efforts have focused on the terrestrial modelling The most severely contaminated areas, with the exception of the immediate surroundings of the power plant, were contaminated by the washout of the plume. As a result of this wetdeposition process, the deposition patterns presented clear spatial structures over very large distances (see Figure 1), related to the meteorological situation (air movement and precipitation) in the days after the accident. Local storms, fog and rain were also at the origin of so-called hot spots which are small areas with contamination levels much higher than those observed in the surrounding areas. In terms of radioactivity concentrations, the biggest contributor initially was radioiodine. The impact of its strong volatility and radiotoxicity as well the importance of the related grass-

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cow-milk chain is balanced by its half-life of 8 days. For what concerns long-term doses, the main contribution comes from radiocaesium (137Cs) and radiostrontium (90Sr), both with a physical halflife of about 30 years. Because modelling with GIS has focused mainly on long-term management of contaminated territories, we will concentrate on these last elements only. 137Cs and 90Sr have an ecological behaviour that is similar to K and Ca, respectively. This property explains that 137Cs, when adsorbed within illitic clay minerals, can remain almost irreversibly fixed for years (Cremers et al., 1988). In general, most radionuclides migrate vertically in soil very slowly, that is roughly with a speed of around 0.1-1 cm per year in most European soils. Soil-to-plant transfer To predict the flux of the deposited radionuclides within the food-chain, radioecologists rely largely on transfer factors (TF) that are determined experimentally. The TF for a certain element is defined as the ratio of the concentration of this element in a receiving compartment (e.g. plant, animal) to the concentration in the source medium (e.g. soil, water, forage). Clearly, the number of parameters that affect these transfers can be large and, as a result, literally thousands of TFs have been measured since the beginning of radioecology in the 1950s. Unfortunately, because the transfer mechanism controlled by many parameters of the source and target compartments often is complicated, one will regularly encounter TFs for similar compartments with reported values that vary by 2 or 3 orders of magnitude. By comparing TFs of 137 Cs in different soils, one would draw the following conclusions: the soil type texture (mainly its clay content), pH value, cation exchange capacity and organic matter are the main parameters that affect radiocaesium mobility between compartments. With decreasing values of pH, clay content or K content, the uptake of radionuclides will generally increase (see e.g. Table 3). TF for Grass 1.1 E-02 2.4 E-02 5.3 E-02

Soil conditions Clay, loam, pH = 6 Sand, pH = 5 Peat, pH= 4

TF for Fodder 1.7 E-02 2.9 E-02 3.0 E-02

Soil conditions Clay, loam, pH = 6 Sand, pH = 5 Peat, pH= 4

Table 3. Examples of TF for grass and fodder in different soils. (IAEA, 1994)

Another (over)simplification one can reasonably implement within models for immediate assessments of the consequences of an accident is to consider the uptake of the radionuclides not specific to the plants. On the other hand, the uptake is nuclide-specific, since it may be high for one type of nuclide but low for another: e.g., soil-plant transfer of Sr is generally much higher than for Cs, whereas for elements such as Pu, Eu or Th there is, on the other hand, almost no uptake by plants. Plant-to-animal transfer Just as for the soil-to-plant transfer, the modelling of radionuclide transfer from plant to animal is traditionally based on TFs that express the ratio of the radionuclide activity concentration in meat or milk (Bq/kg or Bq/l) to the daily intake expressed by the concentration of the radionuclides in the diet (Bq/kg) times the dietary intake (kg/d). Here again, the number of

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parameters that affect the TF values is very large, and we will cite only a few such as species, age and weight of animal, time of year. GIS DATA AND RADIOECOLOGY “The aim of the EUROGRID database is to provide the necessary data to estimate the radiological impact and the economic consequences in case of a large nuclear accident. The data taken into account are populations, land use, agricultural productions, livestock and employment for different sectors of the economy. These data are compiled on a 10 000 km2 grid basis.” (Bonnefous & Despres, 1992). Much progress has been made in the last decade to generate European thematic maps that present harmonized information at a European scale. From the above mentioned 100 km by 100 km cell size, current decision support systems working at a European scale can work at a resolution of 5 by 5 km as shown in Table 1. To highlight the current needs from the data viewpoint, we review the most important thematic maps. Maps of radiocaesium deposition The radioactive deposition data used by the decision support systems presented here are in a raster format. In reality, measurements of radioactivity have a sampling support that can be considered as points in space, and an interpolation step is thus needed to generate a continuous estimation of the radioactive depositions. The result of such a processing, that is the raster map, is very much affected by the choice of the algorithm and by a large number of parameters that need to be chosen carefully. A European Report has been dedicated to this issue (Dubois et al., 2003), and we will not develop this topic here. We will only underline the need for automated and robust interpolation algorithms to be implemented within the GIS, especially for emergency situations. The maps of radiocaesium deposition used in the projects discussed here had generally a main source, which is the atlas of caesium deposition on Europe after the Chernobyl accident (De Cort et al., 1998). For the preparation of this atlas, around 400,000 measurements of 137Cs made in almost all European countries were collected, validated and finally interpolated to establish the European map shown in Figure 2. The preparation of this map highlighted the strong need for harmonized measurement methods and sampling strategies, given the lack of homogeneity in sampling locations, as shown in Figure 2. Measurements were indeed made either in laboratories, in situ, or even from helicopters and airplanes. Furthermore, a number of measurements were made initially in Bq/(kg soil) and thus had to be converted to Bq/m2, i.e. deposition density. Still, much remains to be done to assess properly the uncertainty of these maps. Raster maps with a resolution of 4 km2 have been generated during the preparation of the atlas. These were used to draw isolines of concentration levels and estimate the total deposition for each country. Because of the large variety of sampling densities, the preparation of a single raster radiocaesium map for all Europe to be used for modelling purposes would not have been very meaningful: adjacent cells would not have contained comparable information. As a matter of fact, cell sizes would have varied from 1 km2 to more than 15,000 km2 between countries. Ownership rights of the datasets further complicated the release of a single European data set. As a result, the radiocaesium raster maps used in SAVE and RESTORE were derived from information provided initially in vector format (van der Perk et al., 2000). Such a conversion process inevitably results in a loss of information about the underlying variability of the deposition patterns. This loss is

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further accentuated by the original choice of the quasi-logarithmic scale used to set the isoline levels. There is still a need for a European map of radiocaesium deposition in a raster format for the modelling of fluxes and of the potential risks of contamination. This need is illustrated by the fact that environmental monitoring programs regularly still report values of radioactivity in food that exceed the maximum permitted levels of 600 Bq/kg. This is particularly the case for wild mushrooms that have a very complicated ecological behaviour (Gillett et al., 2000). The lack of detailed information about the habitats of these mushrooms combined with the problem of a very patchy pattern of 137Cs contamination in forests makes it rather challenging to identify the areas where such contamination may occur. Soil maps Many radioecological models for soil-to-plant radiocaesium transfer are based on a model developed by Absalom et al. (2001). The soil characteristics required by this model are organic matter content, pH value, cation exchange capacity (CEC) and clay percentage. For applications at the European level, these parameters could be derived from the European Soil Database, which is currently the most detailed and harmonised spatial soil database that currently exists for Europe (European Soil Bureau, 1999). Most of the soil property data is based on expert judgement of typical soils rather than direct measurements. By means of pedotransfer rules, new attributes can be inferred from those that already exist in the database. These rules assume that a confidence level is attributed to the individual inferred attributes (Daroussin et al., 1996). The output attributes are given as class values: given the low level of precision of the input attributes, the thresholds selected for class intervals represent a compromise between established values in soil sciences and the possible precision level at this scale. For instance, to estimate the topsoil (0-30 cm) organic carbon content from this database, a pedotransfer rule has been developed that uses six input parameters: three for FAO soil names, one each for soil texture, regrouped land use class and accumulated temperature. The output attribute is given in four classes: high (>6%), medium (2.1-6.0%), low (1.1-2.0%) and very low (15%) than the lower limit of 6% of the highest class estimated by the pedotransfer rule, so this method does not separate them from soils with less organic content that fall into this class (Rusco et al., 2001). Most studies of organic carbon content have assigned measured data from a small number of points, deemed to be representative of a particular soil type, to polygons on a soil map that

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represent much larger areas with no measured values. This is an important restriction, because soil characteristics can vary greatly within pedologically defined soil maps that can be mapped (Jones et al., in press). Topsoil organic carbon content, for example, can have a coefficient of variation of between 50 and 150% for the same pedological group (Batjes, 1996). Jones et al (2003) have developed a new method for estimating organic carbon topsoil in Europe. It combines revised pedotransfer rules applied to the European Soil Database with processing of thematic data on harmonised spatial data layers in 1 km by 1 km raster format. The data layers have been calibrated by actual measurements where available. The results are much improved over previous approaches. More generally, this team has produced a set of raster layers for mapping other soil parameters found in the database. For radioecological modelling, these spatial datasets should be used as input to the soil-to-plant transfer models in order to improve the results obtained from the GIS considered above. © EC/IGCE, Roshydromet / Minchernobyl (UA) / Belhydromet

Figure 1. Map of 137Cs deposition in Europe after the Chernobyl accident (De Cort et al., 1998)

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Figure 2. Sampling locations of 137Cs measurements used for the preparation of the map shown in Figure 1. (De Cort et al., 1998)

Dietary habits The third main thematic map needed for modelling radionuclide concentrations in the human food-chain is one that describes European dietary habits. The decision support systems discussed here are using mainly national and regional statistics collected from different sources as shown in Table 4: Theme/property Dietary habits - source

SAVE

RESTORE

Eurostat, national statistical offices, FAO

- extent - scale/detail

EU-15 + NO Regional

- food categories

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Norwegian Radiation Protection Authority (as found in van der Perk et al., 2001) Local case studies in CIS countries Regional (30 km around Chernobyl) to local farms 6

Table 4 Data on dietary habits used by GIS developed in radioecology

The report of Crout et al. (1999) on SAVE clearly shows the lack of harmonized methodologies between countries to define dietary habits. Therefore, most of the estimates of the apparent

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consumption used in SAVE were derived from the following equation on the basis of information found in database of the FAO: Apparent consumption = Production + Imports – Exports + Stock Exchange Per capita values were obtained by dividing the total apparent consumption by population, something that can be further scaled down to regional levels. Food categories had to be further disaggregated to products that are more relevant from a radioecological point of view. Clearly, much remains to be done to have accurate local information: in a case study involving RESTORE (van der Perk et al., 2001), it has been shown that the effect of increased radiocaesium ingestion by consumption of private products, in particular milk and mushrooms, to that based on state shop products can be amounted to a factor of almost 20. To the difficulty of identifying at a European scale the part of the population that has a particular diet that should be considered at risk (e.g. hunters and forest workers who are consuming larger quantities of reindeer, mushrooms, berries and freshwater fish), one can add the problem of converting statistics that are attributed administrative boundaries in an information that is in a raster format. CONCLUSIONS Considerable work has been done in using GIS in the field of radioecology during the eighteen years that have followed the Chernobyl accident. New tools and methodologies have been developed and very large quantities of information (measurements, transfer factors) have been collected. Time is now certainly ripe to compare the various works done so far in a constructive way to consolidate the existing experience and to better highlight the main issues that remain to be explored. The survey made here about the main thematic maps used in radioecology by these GIS has underlined the lack of harmonised information as well as the many uncertainties associated to the main variables derived from these maps that propagate in the radioecological models. In order to efficiently compare the various methodologies implemented within these GIS and provide coherent responses in radioecology in the case of future accidents, we believe there is an urgent need to identify the most appropriate European thematic maps and assess their suitability and relative uncertainties for radioecological modelling. One is used in radioecology to work with generic values for first approximation; however, the specificity of radioecological models could certainly be enhanced by improving the way GIS data are used. The European Soil Database is clearly an essential dataset and its potential as well as its limitations for radioecological modelling still remains to be fully explored. The need for such an exploration is further supported by the fact that soil treatments to reduce the mobility of the radionuclides remain among the most important and extensively measured used. The similarities between models used in radioecology with those used for predicting the behaviour of heavy metals in the environment further underlines the need for more collaboration between environmental modellers in general and the actors involved in the development of European harmonised datasets. One would also expect such collaboration to resolve the many limitations one is encountering due problems with data ownerships, political and institutional issues.

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ACKNOWLEDGEMENTS We would like to acknowledge Bob Jones of the European Soil Bureau for providing us with substantial support in using the European Soil Database. BIBLIOGRAPHY Absalom, J. P., Young, S. D., Crout, N. M. J., Sanchez, A., Wright, S. M. , Smolders, E., Nisbet, A. F., and A. G. Gillett (2001). Predicting the transfer of radiocaesium from organic soils to plants using soil characteristics, Journal of Environmental Radioactivity, 52(1): 31-43. Arutyunyan, R.V., Bolshov, L.A., Demianov, V.V., Glushko, A.V., Kabalevski, S.A., Kanevsky, M.F., Kiselev, V.P., Koptelova, N.A., S.F. Krylov, Linge, I.I. Martynenko, E.D., Pechenova, O.I. Savelieva, E.A., Serov, A.N., Haas, T., Maignan, M. (1996). Environmental decision support system on base of geoinformational technologies for the analysis of nuclear accident consequences. In: The radiological consequences of the Chernobyl accident. EUR 16544 EN, EC, pp. 539-542. Batjes, N.H. (1996). Total carbon and nitrogen in the soils of the world. European Journal of Soil Science 47: 151-163. Bonnefous, S., and A. Despres (1992). The European data base EUROGRID: methodological problems and recent developments. In: Proceedings of the 8th International Congress of the International Radiation Protection Association, Montreal, May 17-22, Vol.1, pp. 269272. (In French) Cremers, A., Elsen, A., De Preter, P., and A. Maes (1988). Quantitative analysis of radiocaesium retention in soils. Nature 335:247 – 249. Crout, N., Gillett, A., Absalom, J. and S. Young (1999). SAVE-IT: Spatial and Dynamic Prediction of Radiocaesium Transfer to Food Products. Part 2: Data Bases. Institute of Environmental Science, University of Nottingham, UK. Daroussin, J. and D. King (1996). A pedotransfer rules database to interpret the Soil Geographical Database of Europe for environmental purposes. In: Proceedings of The use of pedotransfer in soil hydrology research in Europe. Orléans, France, 10-12 October 1996. De Cort M., Dubois G., Fridman S., Germenchuk M., Izrael Y., Janssens A., Jones A., Kelly G., Knaviskova E., Matveenko I., Nazarov I., Pokumeiko Y., Sitak V., Stukin E., Tabachny L., Tsaturov Y. and S. Avdyushin (1998). Atlas of Caesium 137 deposition on Europe after the Chernobyl accident. EUR 16733 EN/RU, EC. 176 pp. Dubois, G., and P. Bossew (2003). Spatial analysis of 137Cs in the environment: an overview on the current experience. In: Mapping radioactivity in the environment. Spatial Interpolation Comparison 1997. G. Dubois, J. Malczewski & M. De Cort (Eds.), EUR 20667 EN, EC, pp. 21-36. Ehrhard, J., Brown, J., French, S., Kelly, G.N., Mikkelsen, T. and H. Müller (1997). RODOS: Decision-Making Support for Off-Site Emergency Management after Nuclear Accidents. Kerntechnik 62 (2-3): 122-128.

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European Soil Bureau (1999). European Soil Database v1.0 metadata June 1999: Soil Geographical Database of Europe v. 3.2.8.0. Joint Research Centre, Ispra, Italy. http://esb-net.jrc.it/ Fesenko, S. V. , Soukhova, N. V., Sanzharova, N. I., Avila, R., Spiridonov, S. I. , Klein, D., and P. -M. Badot (2001). 137Cs availability for soil to understory transfer in different types of forest ecosystems, The Science of The Total Environment, 269 (1-3): 87-103. Gillett, G., and N.M.J. Crout (2000). A review of 137Cs transfer to fungi and consequences for modelling environmental transfer. Journal of Environmental Radioactivity, 48: 95–121. Howard, B. J., Wright, S. M., and C. L. Barnett (1999). Spatial Analysis of vulnerable ecosystems in Europe: Spatial and dynamic prediction of radiocaesium fluxes into European foods (SAVE). Final report. Commission of the European Communities. Grange-over-Sands: Institute of Terrestrial Ecology, 65 pp. Howard, B. J., Wright, S. M., Barnett, C. L., Skuterud, L., and P. Strand (2002). Estimation of critical loads for radiocaesium in Fennoscandia and Northwest Russia. Journal of Environmental Radioactivity, 60(1-2): 209-220. IAEA (1994). Handbook of parameter values for the prediction of radionuclide transfer in temperate environments. TRS-364, Vienna. Jones, R.J.A., Hiederer, R. Rusco, E., Loveland, P.J. and L. Montanarella (in press). Estimating organic carbon in the soils of Europe for policy support. Submitted October 2003 to European Journal of Soil Science. Kirchmann, R., and E. Van der Stricht (2001). Radioecology: radioactivity and ecosystems. Fortemps. Rigina, O., and A. Baklanov (2002). Regional radiation risk and vulnerability assessment by integration of mathematical modelling and GIS analysis. Environment International, (27)7: 527-540. Rusco, E., Jones, R.J.A. and G. Bidoglio (2001). Organic matter in the soils of Europe: Present status and future trends. EUR 20556 EN. Office for Official Publications of the European Communities, Luxembourg. Salt, C. A., and M. Culligan Dunsmore (2000). Development of a spatial decision support system for post-emergency management of radioactively contaminated land. Journal of Environmental Management, 58(3): 169-178. Skuterud, L., Travnikova, I. G., Balonov, M. I.., Strand, P., and B.J. Howard (1997). Contribution of fungi to radiocaesium intake by rural populations in Russia. Science of Total Environment, 193: 237–242 Van der Perk, M., Burema, J.R., Burrough, P.A. , Gillett, A.G., and M.B. van der Meer (2001). A GIS-based environmental decision support system to assess the transfer of long-lived radiocaesium through food chains in areas contaminated by the Chernobyl accident. International Journal of Geographical Information Science, 15(1): 43-64. Van der Perk, M., Lev, T., Gillett, A. ., Absalom, J.P. , Burrough, P.A. , Crout, N.M.J. , Garger, E.K. , Semiochkina, N. , Stephanishin, Y.V. , and G. Voigt (2000). Spatial modelling of

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transfer of long-lived radionuclides from soil to agricultural products in the Chernigov region, Ukraine. Ecological Modelling 128: 35-50. Semioshkina, N., Voigt, G., and D. Tarsitano (2003). Evaluation and network of EC – Decision Support Systems in the field of terrestrial radioecological research – EVANET. In: Proceedings of the 5th Eurosafe Forum, Paris, pp. 39-51. http://www.eurosafe-forum.org/ Warner, F., and R. M. Harrison (1993). SCOPE 50 - Radioecology after Chernobyl: Biogeochemical, Pathways of Artificial Radionuclides. John Wiley and Sons.

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