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[en] Full text: The FRUITPATH model is a generic fruit-specific model for radionuclide accumulation in fruits that was developed by I Linkov and D. Burmistrov (USA) during participation in the Fruits WG FRUITPATH calculates a time series of inventories for a specific radionuclide distributed within the fruit system compartments. The number of compartments can be defined by the user for specific fruit types. For example, apple can be represented by the Tree, Organic Layer, Labile Soil, Fixed Soil and Deep Soil. FRUITPATH focuses on a generic ecosystem application. It is a wholly probabilistic model that incorporates uncertain model parameters as probability distributions and predicts distribution for the output radionuclide concentrations in fruit compartments. For generic model application, uncertain model parameters are estimated from literature that includes different fruit and soil types. For site-specific applications, the available literature data are limited to the ecosystems similar to the site under consideration; site-specific parameters are thus estimated. Further model calibration, based on site-specific measurements, can be accomplished by using Bayesian updating procedures. The radionuclide source term in FRUITPATH is total deposition to the ground (Bq m-2). Partitioning of radionuclides between plant and soil organic layer compartments is based on a the plant interception fraction. Material removal from the plant is characterised by the time dependent removal time. Transfer from soil to plant is described by the uptake rate that depends on plant biomass and plant type. The FRUITPATH framework is flexible to include scenario-specific conditions, for instance, for the BIOMASS calculations, modelling of pruning was added. (author)

[en] As a result of the Chernobyl nuclear power plant accident in 1986, large forested areas in Europe were contaminated by radionuclides. Extensive societal pressure has been exerted to decrease the radiation dose to the population and to the environment. Thus, in making abatement and remediation policy decisions not only economic costs, but also human and environmental risk assessment are desired. Forest remediation by organic layer removal, one of the most promising cleanup policies, is considered in this paper. Ecological risk assessment requires evaluation of the radionuclide distribution in forests. The FORESTPATH model is used for predicting the radionuclide fate in forest compartments after deposition as well as for evaluating the application of the remedial policy. Time of intervention and radionuclide deposition profile was predicted as being crucial for the remediation efficiency. Risk assessment conducted for a critical group of forest users in Belarus shows that consumption of forest products (berries and mushrooms) leads to about 0.004% risk of a fatal cancer. Cost-benefit analysis for forest cleanup suggests that complete removal of organic layer is too expensive for application in Belarus

[en] Fungi are one of the most important components of forest ecosystems, since they determine to a large extent the fate and transport processes of radionuclides in forests. They play a key role in the mobilization, uptake and translocation of nutrients and are likely to contribute substantially to the long-term retention of radiocesium in organic horizons of forest soil. This paper gives an overview of the role of fungi regarding the transfer and cycling of nutrients and radionuclides, with special emphasis on mycorrhizal symbiosis. Common definitions of transfer factors, soil-fungus and soil-green plant, including their advantages and limitations, are reviewed. Experimental approaches to quantify the bioavailability of radionuclides in soil and potential long-term change are discussed

[en] Concentrations of ¹³⁷Cs and stable Cs were determined in plant, mushroom, lichen and soil samples collected at two forest sites with different contamination levels in Belarus in 1998. The concentration of ¹³⁷Cs in soil was the highest in near-surface organic layers (Of and Oh horizons) and decreased with depth in the mineral layers, whereas the concentrations of stable Cs were almost constant in the soil profile. The levels of ¹³⁷Cs and stable Cs in biological samples varied depending both on the species and the plant part sampled. Even though different species and parts of the same species were included, the concentration ratios of ¹³⁷Cs to stable Cs were fairly constant for samples collected at the same forest site, and were in the same order of magnitude as the ¹³⁷Cs to stable Cs ratios for the organic soil layers. This finding suggests that ¹³⁷Cs, mainly deposited on the forest ecosystems from the Chernobyl accident in 1986, was well mixed with stable Cs within the biological cycle in the forest ecosystems by 1998. The transfer factor for each biological sample of ¹³⁷Cs was almost the same as that of stable Cs, if they were calculated based on the concentrations in the Of+Oh layer. This suggests that the stable-Cs-based transfer factor could be used as equilibrium transfer factor of ¹³⁷Cs for different types of biological samples in the forest

[en] Air surveys, whole-body counting, bioassays or combination of these measurements can be utilized for purposes or assessing internal doses to determine compliance with occupational dose equivalent limits. Air sampling with a little support provided by whole body counting and/or bioassays was often relied on in dose calculations. The utility of air sampling for internal dose reconstruction is addressed in this paper through the probabilistic analysis of environmental factors and their impact on dose estimates. In this paper we attempt to reconstruct an internal dose due to inhalation of beta + gamma emitting radionuclides for a contractual electrician, Mr. X. The data available for reconstruction of internal dose for Mr. X was found to be highly variable and uncertain. Uncertainty describes a lack of knowledge about a parameter, this lack of knowledge theoretically can be reduced, e.g., if more measurements were to be taken (for example, estimated activities for alpha-emitting radionuclides are uncertain due to the influence of naturally-occurring alpha-emitters). Variability describes the existence of different values that represent different environmental conditions (for example, the air concentrations of radionuclides may vary over time because of the different tasks performed by workers in the area). Variability can not be reduced by additional data collection because the varying values reflect the variable nature of the environment, not a lack of data. The high variability in measured air concentrations in the restricted areas of a LWR nuclear power plant where he worked do not allow adequate reconstruction of his individual internal dose using deterministic methods and therefore probabilistic methods are desirable. The guidance for probabilistic assessment developed by the United States Environmental Protection Agency as well as recommendations of the National Council of Radiation Protection provide an adequate framework for probabilistic reconstruction of Committed Effective Dose Equivalent (CEDE) for Mr. X. The total internal intake was calculated using Monte-Carlo simulations and then translated to dose using dose conversion factor. The results of the analysis reveal a broad distribution in dose estimates. The resulting dose distribution is significantly skewed to the high doses. The mean dose estimate is significantly different from the median dose. Median doses, which are often required for litigation in similar cases (to estimate if somebody, more likely than not, has received a dose above specified limit), should therefore be estimated using probabilistic techniques since using the mean for deterministic estimates may lead to erroneous conclusions for non-symmetric data distributions. Sensitivity analysis was conducted to determine which of the input parameters contributed most to the uncertainty in internal dose estimates. The spatial and temporal variations in air concentration measurements were found to be among the most significant contributors. Internal dose estimates that use individual air surveys supported by bioassay and whole-body counting data are desirable for internal dose reconstruction. (author)

[en] The Chernobyl Nuclear Power Plant accident in 1986 caused radionuclide contamination in most countries in Eastern and Western Europe. A prime example is Belarus where 23% of the total land area received chronic levels; about 1.5 X 10⁶ ha of forested lands were contaminated with 40-190 kBq m^-2 and 2.5 X 10⁴ ha received greater than 1,480 kBq m^-2 of ¹³⁷Cs and other long-lived radionuclides such as ⁹⁰Sr and ^239,240Pu. Since the radiological dose to the forest ecosystem will tend to accumulate over long time periods (decades to centuries), we need to determine what countermeasures can be taken to limit this dose so that the affected regions can, once again, safely provide habitat and natural forest products. To address some of these problems, our initial objective is to formulate a generic model, FORESTPATH, which describes the major kinetic processes and pathways of radionuclide movement in forests and natural ecosystems and which can be used to predict future radionuclide concentrations. The model calculates the time-dependent radionuclide concentrations in different compartments of the forest ecosystem based on the information available on residence half-times in two forest types: coniferous and deciduous. The results show that the model reproduces well the radionuclide cycling pattern found in the literature for deciduous and coniferous forests. Variability analysis was used to access the relative importance of specific parameter values in the generic model performance. The FORESTPASTH model can be easily adjusted for site-specific applications. 92 refs., 5 figs., 6 tabs

[en] Concentrations of pollutants in the atmosphere have increased dramatically over the last century and many of these changes are attributable to anthropogenic activities. The influence of acid rain has been well studied, but there has been no extensive exploration of other pollutants, such as toxic chemicals, heavy metals and radionuclides. Natural ecosystems, especially forests, tend to accumulate many of these pollutants which subsequently can affect ecosystem health. These contaminants may be very damaging to the environment in Eastern Europe, where the rapid disappearance of forest is the result not only of contamination but also of poor forest management practices. The current book is designed to reduce the uncertainty in our current knowledge of forest radioecology. The three topics it embraces are (a) Modelling, (b) Measurements and Data, and (c) Countermeasures and Risk Assessment

[en] Ecological modeling is a powerful tool which can be used to synthesize information on the dynamic processes which occur in ecosystems. Models of radionuclide transport in forests were first constructed in the mid-1960's, when the consequences of global fallout from nuclear weapons tests and waste disposal in the environment were of great concern. Such models were developed based on site-specific experimental data and were designed to address local needs. These models had a limited applicability in evaluating distinct ecosystems and deposition scenarios. Given the scarcity of information, the same experimental data sets were often used both for model calibration and validation, an approach which clearly constitutes a methodological error. Even though the carry modeling attempts were far from being faultless, they established a useful conceptual approach in that they tried to capture general processes in ecosystems and thus had a holistic nature. Later, radioecological modeling attempted to reveal ecosystem properties by separating the component parts from the whole system, as an approach to simplification. This method worked well for radionuclide transport in agricultural ecosystems, in which the biogeochemistry of radionuclide cycling is relatively well understood and can be influenced by fertilization. Several models have been successfully developed and applied to human dose evaluation and emergency response to contaminating events in agricultural lands

[en] Coastal areas adjacent to the Black Sea, particularly in Crimea, have suffered from inappropriate human activities, poorly regulated industry and former naval bases. Industrial and municipal wastewater pollutants draining into the three major European rivers (the Danube, Dniestr, and Dnieper) and dumping in the open sea result in an enormous increase in contamination level of ecosystems of the Black Sea. In spite of this, Crimea and its adjacent waters is still a globally important center of biological diversity, with an enormous and exciting range of habitats within a comparatively small area. The problem now is to evaluate economically feasible remediation and ecologically sustainable cleanup/reuse alternatives for the most contaminated sites of this area. One of the principal methodological components of such evaluation is a risk-based decision protocol that provides support in analysis of ecological value and reuse options for a chosen site. This paper presents the results of development of a spatially explicit risk assessment technique to be implemented as a part of the decision-making process and gives an example of its application to contaminated marine ecosystems. The model is suggested that takes into account several principal assumptions: (i) spatial heterogeneity of contamination of forage is known and mapped within known location of receptor's habitat, and (ii) the receptor movement and timescale are determined by location, volume and attractiveness of local habitat and forage resources. This implies two models: Spatially Explicit Exposure Assessment Model that calculates internal exposure resulting from ingestion of contaminated feeds, and Probabilistic Receptor Migration Model that generates motivation of behaviour of a receptor while feeding. In the first model, time-dependent accumulation of contamination in receptor tissue is defined by the differential balance equation that takes into account forage consumption rate and excretion rate. In the second model, the velocity of receptor's migration in each cell is inversely proportional to the forage volume and habitat quality presented. The model allows depicting the receptor migration traces within habitat area. The model also gives possibility to implement two principal algorithms. The basic or deterministic algorithm is when the receptor migration within habitat area is equiprobable and the concentration fields of contaminants in forage resources are averaged all over the migration area. The semi-probabilistic algorithm reflects the probability of the receptor's presence and duration of presence in the given zones taking into account habitat quality and attractiveness of various forage resources in these zones. The spatial distribution of concentration of the contaminants in forage resources of habitat area is also taken into account. The later algorithm allows revealing many interesting effects that may specify exposure assessment, e.g., some data on incorporated activity and their deviation depends on configuration of migration zone. It was shown in model calibration study that exposure estimates for fish, anthozoa and other aquatic populations in areas containing spatially localized contaminants are functions of spatial factors, such as the receptor's average foraging area, the size of the habitat, and the specific distribution of contamination. We present a software prototype that calculates accumulation of polychlorinated biphenyls by fishes and their higher order predators, including humans. This study was partially supported by GEF/UNDP and NATO. (author)