[en] The RUVFRU model is a fruit-specific model that was developed by the University of Veszprem (Hungary) during participation in the Fruits WG. The model includes most of the dynamic processes by means of a compartmental system, starting from acute deposition. These are described by first order differential equations. The endpoint of the model is the activity concentrations of the compartments that represent the air and the parts of the soil and the fruit bearing vegetation for each radionuclide and for each fruit. These can be used as input data to estimating doses in the case of countermeasure planning after a nuclear emergency. The growth of vegetation (mass and interception) is described by sigmoidal curves. The rate constants between compartments depend generally on seasonality (temperature) and some of them are mass-dependent. The model can take into consideration several agricultural activities like ploughing, replanting and pruning. Most of the parameter values originate from IAEA and Hungarian publications presenting results of post Chernobyl measurements carried out in Europe

[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] The DOSDIM model is an example of a non-fruit specific model that was used to calculate the transfer of radionuclides to fruit. Only calculations for strawberries were carried out. For plant specific parameters, those for leafy vegetables were used to estimate interception by the strawberry plant and those for root vegetables to calculate the translocation rate. The parameter for root uptake was derived from the TF values given in the Fruit Review (Section 2). Only translocation from external plant surfaces to fruit was considered. For deposition during flowering time, it was assumed that the translocation parameters from external plant surfaces to blossoms are the same as for fruit and all radioactivity translocated to blossoms will eventually be found in the fruit (conservative approach)

[en] FRUTI-CROM is a fruit-specific model that was developed by CIEMAT (Spain) during participation in the Fruits WG. FRUTI-CROM started from an existing model CROM (vegetable sub-model) designed to evaluate radionuclide concentration in different compartments of the environment and to assess the radiological impact to man from routine and accidental releases. The model considers the following processes: dry or wet deposition, interception by vegetation surfaces, translocation from external surfaces to edible part of plant, root uptake, adhesion of soil particles onto vegetation surfaces. To simplify the model, a number of these processes are taken into account by use of composite parameters that describe the effect of two or more interaction processes. Processes that can lead to the reduction of radionuclide concentrations in vegetation include radioactive decay, growth dilution, wash-off, pruning, harvesting, leaching and soil fixation

[en] ASTRAL is an IPSN bespoke software designed for a single (acute) deposition and dedicated to assessing post-accident situations in the environment. Starting from deposition it calculates concentrations of radionuclides in food products, enables comparisons with regulatory levels and calculates radiation doses received by man through ingestion, inhalation of particles after resuspension, and external exposure to radionuclides deposited onto the soil. ASTRAL, has no fruit specific sub-model, but there is a sub-model that is used for fruit vegetables: it is assumed that fruit are produced throughout the year (market garden scenario). The model and parameters for the fruit vegetable class have been chosen, as this class covers a wide variety of plants, from vegetables such as tomatoes and beans, to strawberries

[en] This report contains a description of the activities carried out by the Fruits Working Group and presents the main results such as conceptual advances, quantitative data and models on the transfer of radionuclides to fruit in the context of the overall objective of BIOMASS Theme 3. The aim of the study was to improve understanding of the processes affecting the migration of radionuclides in the fruit system and to identify the uncertainties associated with modelling the transfer of radionuclides to fruit. The overall objective was to improve the accuracy of risk assessment that should translate to improved health safety for the population and associated cost savings. The significance of fruit, intended as that particular component of the human diet generally consumed as a dessert item, derives from its high economic value, the agricultural area devoted to its cultivation, and its consumption rates. These are important factors for some countries and groups of population. Fruits may become contaminated with radioactive material from nuclear facilities during routine operation, as a consequence of nuclear accidents, or due to migration through the biosphere of radionuclides from radioactive waste disposal facilities. Relevant radionuclides when considering transfer to fruit from atmospheric deposition were identified as ³H, ¹⁴C, ³⁵S, ³⁶Cl, ⁹⁰Sr, ¹²⁹I, ¹³⁴Cs and ¹³⁷Cs. The transfer of radionuclides to fruit is complex and involves many interactions between biotic and abiotic components. Edible fruit is borne by different plant species, such as herbaceous plants, shrubs and trees, that can grow under different climatic conditions and may be found in agricultural or natural ecosystems. A review of experimental, field and modelling information on the transfer of radionuclides to fruit was carried out at the inception of the activities of the Group, taking into account results from a Questionnaire circulated to radioecologists. Results on current experimental studies have also been discussed during the biannual meetings of the Group. These findings, as well as results from those experimental studies reported directly to the Group and key interactions reported in the literature, are reported below. Radionuclides reach fruit by three principal routes: (i) deposition to soil, vertical migration in soil, root uptake, migration to the fruit (and other plant parts); and/or (ii) deposition to exposed plant surfaces, translocation to plant interior, migration to the fruit (and other plant parts); and/or (iii) deposition to exposed fruit surfaces. The relative significance of each pathway depends upon the season during which contamination occurs, upon the stage of plant development and upon how this development is affected by climatic, edaphic and management factors. Root uptake followed by migration to the fruit is represented in literature by the soil to plant Transfer Factor (TF), a parameter that relates radionuclide concentration in fruit to that in the soil. A collection of data on TFs for fruit crops provides ranges for caesium, strontium, plutonium and americium. The variability in TF for a given radionuclide is mainly ascribable to differences in soil properties, rather than differences between fruit species. TF values for caesium are the most variable and cover six orders of magnitude. Concentration in the fruit varies both as the fruit develops and according to the time of contamination relative to production of the fruit. For caesium, complex patterns in concentration may be observed during a growing season as a result of the combination of rate of transfer to the fruit, rate of biomass production of the fruit, and degree of water content. Fruit storage before consumption as well as industrial or domestic processing may reduce the activity concentration in the foodstuff that is actually consumed, with implications for assessments of doses from releases of radionuclides to the environment

[en] Full text: SPADE (Soil Plant Animal Dynamic Evaluation) is the name given to a suite of codes used to assess the impact of potential radioactive discharges on man through the ingestion of contaminated food. Radionuclide inputs to SPADE are results from atmospheric dispersion calculations, measured or assumed concentrations in air (Bq m-3) and/or deposition rates (Bq m-2s-1) to ground. The quantity of radionuclides reaching the above ground compartments of the plant from atmospheric sources is determined according to the interception fraction which takes account of changes in plant biomass with season. Depending on the model, plants or leaves are divided into external and internal components to allow particulate deposition to be distinguished from radioactive gases and vapours. Radionuclide distribution in plants depends on both the physiological characteristics of the plant and the physico-chemical properties of the radionuclide. Material lost from the plant by wash-off is partitioned between either soil solution and organic matter, or 'soil available' and 'soil unavailable', as appropriate. Transfers from soil to plant occur via root uptake and are assumed to vary with soil layer depth, as a function of the root distribution throughout the soil profile. Consequently the transfer of radionuclides from soil to root is represented in SPADE by a single transfer rate, normalised for each of the ten layers in the soil model according to root distribution. SPADE models radionuclide uptake by three types of fruit crops: herbaceous, shrubs and trees. Parameter values used in SPADE are those specified in the scenarios where appropriate. Where parameter values for some processes were not provided in the scenarios, SPADE default values were used. Pruning was considered for both blackcurrants and apple trees according to information supplied in the scenarios. Strawberry plants were replaced every two years and debris was removed from the field. The SPADE suite of codes is used by the United Kingdom Food Standards Agency (formerly part of the UK Ministry of Agriculture, Fisheries and Food - MAFF) for regulatory purposes. Input parameters for the models are selected to provide realistic predictions that are towards the upper end of observed concentrations in food products. On this basis the output from SPADE is a best estimate prediction. This is reinforced by the use of scenarios that are likely to produce high concentrations, e.g. deposition to crops at a time when transfer to the edible component is likely to be greatest. The fruit plant model in SPADE [Thorne and Coughtrey, 1983] consists of six compartments, representing internal leaf, external leaf, stem, fruit, storage organs and root. Movement of radionuclides within the plant model is controlled by empirically derived rate constants and parameters are derived for three broad categories of fruit plant: herbaceous, shrub and tree. Models are implemented in SPADE for 20 elements. and the following discussion considers the iodine models for fruit. Two experimental programmes have been undertaken in connection with the development of the SPADE fruit models for herbaceous and shrubby fruit crops [Kirton et al., 1987; Donnelly and Carini, 1998]. The data from these experiments provide valuable information for model validation. Foliar absorption may be an important pathway for the uptake of radionuclides deposited on external plant surfaces, and is represented by transfers between the external leaf and internal leaf compartments. Not all compartments in the model are directly linked, and in some cases transfers occur in one direction only. Ten internal transfers occur in the standard fission/activation plant model. Interception by plants takes account of changes in plant biomass with season. Depending on the model, plant or leaves are divided into external and internal components to allow particulate deposition to be distinguished from radioactive gases and vapours. Passage through the stomata and incorporation into the mesophyll is therefore represented by partitioning a fraction of the intercepted deposit to the internal compartment. The original default parameters for iodine [Coughtrey and Thorne, 1981] were based largely on data for cereals, but were modified in the case of tree and shrub fruits to allow for more rapid transfer from stem to root so that the root store could serve as a reservoir through subsequent seasons. Loss of radionuclides from external plant surfaces to the soil is modelled as transfer to the surface layer of the soil model and include losses arising from leaf fall. The parameters for the three fruit models for iodine in SPADE (herbaceous, shrub and tree) are similar with the following exceptions. Differences for herbaceous fruit crops are as follows: the root store is switched off; there are crop-specific transfers from root to stem and from stem to internal leaf; and, internal to external leaf was chosen to reflect cereals rather than fruit crops. As concerns the other two fruit crop types the return from the root store reservoir is slower for tree fruit than for shrub fruit by an order of magnitude. The process of root uptake is modelled as the transfer of radionuclides from soil solution to the plant root compartment. The transfer rate is also assumed to vary with soil layer depth, both as a function of the root distribution throughout the soil profile and as a function of the deposit distribution in soil. Consequently, the transfer of radionuclides from the soil solution to root is represented by a discrete transfer from each of the 10 layers in the soil model. The soil model is not considered further here. (author)