Foliar uptake of 134Cs and 85Sr in strawberry as function by leaf age

In this paper a study of the foliar uptake and translocation of 134Cs and 85Sr in a herbaceous fruit plant is presented. In particular, absorption, translocation and loss of these radionuclides in strawberry plants have been studied in relation to the age of contaminated leaves. Strawberry plants were contaminated by distributing droplets of an aqueous solution containing 134CsCl and 85SrCl2 on the surface of two leaves per plant. One half of the plants was contaminated through two young leaves, a second half through two old leaves. Sets of plants were collected 1 day, 7 days and 15 days after contamination. One half of them was rinsed with double distilled water before gamma analysis. Rinsing contaminated leaves removes on average 55% of the applied 134Cs and 45% of 85Sr. The activity removed decreases during the 15 days of the experimental study, both for 134Cs and for 85Sr, suggesting an increase in foliar absorption during this period. The activity removed does not differ between old and young leaves. "External loss" is lower for young than old contaminated leaves. "Internal loss" through translocation occurs mainly for 134Cs. Translocation coefficients from contaminated leaves to fruits are two orders of magnitude higher for 134Cs (4.0%), than for 85Sr (0.05%). Leaf to fruit translocation coefficients for 134Cs are higher from young leaves (5.8%), than from old leaves (2.3%).     

Ventomod: a dynamic model for leaf to fruit transfer of radionuclides in processing tomato plants (Lycopersicon esculentum Mill.) following a direct contamination event

This paper presents results on the calibration and validation of a model (Ventomod) for leaf to fruit transfer of (134)Cs, (85)Sr and (65)Zn in processing tomato plants after leaf contamination. Several models (e.g. FARMLAND) that deal specifically with the transfer of radionuclides to fruits are adaptations of models that were developed for agricultural crops such as leafy green vegetables. "Ventomod" represents a dynamic evaluation model exclusively built for the short-term behaviour of radionuclide depositions. It forecasts the level of radionuclide contamination in ripe processing tomato fruits following an accidental radionuclide release into the atmosphere. A validation of the developed model by data sets from an independent experiment showed that the model successfully reproduced the observed radionuclide distribution and dynamics in tomato fruits. The level of uncertainty was within the normal range of similar assessment models. For a more general use of this model further testing with independent data sets from experiments obtained under different environmental conditions and data from other horticulturally important plant species would be desirable.     

A model testing study for the transfer of radioactivity to fruit

This paper compares predictions of the foodchain model SPADE with experimental data for the transfer of (134)Cs and (85)Sr to strawberry plants following acute foliar and soil contamination. The transfer pathways considered in this exercise included direct deposition to fruit, leaf-to-fruit, soil-to-leaf and soil-to-fruit transfers. Following foliar contamination, the difference between predicted and measured radionuclide activity values varied between a factor of 0.5-10 for fruit and 4.5-7 for leaf. Following soil contamination, the difference between predicted and measured values varied between a factor of 3-74 for fruit and 32-44 for leaf. In all cases the difference between measured and predicted values was smaller for (85)Sr than (134)Cs. Measured and predicted activities were higher for leaf than fruit. Both measured and predicted (134)Cs concentrations in fruit and leaf are higher when deposition occurs at ripening than at anthesis. These results confirm the need for more data on fruit, even for Cs and Sr, to support models in predicting the transfer of radionuclides to fruit crops. Ongoing research projects funded by the UK Food Standards Agency aim to provide some data on radionuclide transfer to herbaceous, shrub and tree fruits, which will help improve radiological assessment models in order to provide better protection for consumers.     

Radionuclide transfer to fruits: a critical review. Introduction

This paper provides a brief introduction to fruit, their definition, classification and geographical distribution. In the following review, the term "fruit" refers not to a well-defined botanical plant part but, in the horticultural sense, to a component of the human diet generally consumed as a dessert item. Plants that bear fruits cover a vast range of morphological and physiological traits. A generic classification of fruit-bearing plants is proposed for use in studies on radionuclide transfer to fruit.     

Radionuclide transfer to fruits: A critical review. Foreword

After completion of the (Validation of Environmental Model Predictions) (VAMP) and (BIOspheric Model Validation Study) (BIOMOVS II) Programmes, the Division of Radiation and Waste Safety of the IAEA decided to promote a new co-ordinated research programme to continue activities in the area of biosphere modelling. As a result, the BIOMASS Programme on BIOsphere Modelling and ASSessment was launched in Vienna in October 1996. The Programme is scheduled to finish in October 2000. The overall objective of BIOMASS is to provide an international focal point in the area of biosphere assessment modelling. There are 3 Themes and 11 working groups in BIOMASS. The objective of the Theme 3 Fruits Working Group is to improve understanding of the uptake and transfer of radionuclides from different sources to fruit. As part of the work programme, a review was undertaken of the experimental, field and modelling information on the transfer of radionuclides to fruit.     

Attitudes of rural population in emergency exposure situations

People growing crops in kitchen gardens eat locally self-produced food and are the subject of growing attention as the potential for a more sustainable development. A survey was carried out in two provinces in northern Italy to gather information on the consumption of local horticultural products, peoples’ expectations of authorities in the case of a nuclear accident and peoples’ behaviour in the absence of official information. Results show that up to 70% of the owners of kitchen gardens possess diets comprised of more than 60% of self-produced vegetables and can be regarded as particular groups of population. In the case of a dispersion of radioactive material, the local population would take advantage of official information on preventive measures to protect farms and local crops from contamination. Results of the survey show differences in the attitude of the population due to age, gender and past experience.     

Modelling and experimental studies on the transfer of radionuclides to fruit

Although fruit is an important component of the diet, the extent to which it contributes to radiological exposure remains unclear, partially as a consequence of uncertainties in models and data used to assess transfer of radionuclides in the food chain. A Fruits Working Group operated as part of the IAEA BIOMASS (BIOsphere Modelling and ASSessment) programme from 1997 to 2000, with the aim of improving the robustness of the models that are used for radiological assessment. The Group completed a number of modelling and experimental activities including: (i) a review of experimental, field and modelling information on the transfer of radionuclides to fruit; (ii) discussion of recently completed or ongoing experimental studies; (iii) development of a database on the transfer of radionuclides to fruit; (iv) development of a conceptual model for fruit and (v) two model intercomparison studies and a model validation study. The Group achieved significant advances in understanding the processes involved in transfer of radionuclides to fruit. The work demonstrated that further experimental and modelling studies are required to ensure that the current generation of models can be applied to a wide range of scenarios.     

Post-deposition transport of radionuclides in fruit

This paper considers two main pathways for contamination of fruit by radionuclides: (i) absorption after deposition directly to exposed fruit surfaces, and (ii) absorption after deposition to other exposed plant surfaces followed by translocation to fruit. The aim is to collect the available information on fruit from temperate regions, identify the factors affecting post deposition processes in fruit plant systems, identify gaps in knowledge and give recommendations for future work. The majority of information available on above-ground absorption and further translocation to fruit concerns 134Cs and 85Sr in soluble form in apple, strawberry and grapevine. In general, 85Sr is absorbed and translocated to a lesser extent than is 134Cs. The rate of absorption and translocation depends on the physiological stage and age of the plant, and varies between different plant species and varieties.     

Spatial analysis of plant detritus processing in a Mediterranean river type: the case of the River Tirso Basin,Sardinia, Italy

The river continuum concept represents the most general framework addressing the spatial variation of both structure and function in river ecosystems.In the Mediterranean ecoregion,summer drought events and dams constitute the main sources of local disturbance to the structure and functioning of river ecosystems occurring in the river basin.In this study,we analysed patterns of spatial variation of detritus processing in a 7th order river of the Mediterranean ecoregion(River Tirso,Sardinia0Italy)and in three 4th order sub-basins which were exposed to different summer drought pressures.The study was carried out on phragmites australis and Alnus glutionsa leaf detritus at 31 field sites in seasonal field experiment Detritus processing rates were higher for Alnus glutionsa than for Phragmites australis plant detritus.Processing rates of Alnus glutionsa leaves varied among seasons and study sites from 0.006d^-1 to 0.189d^-1 and those of Phragmites australis leaves ranged from 0.0008d^-1 to 0.102d^-1,with the lowest values occurring at sites exposed to summer drought.Seasons and sites accounted for a significant proportion of such variability.Alder detritus decay rates generally decreased with increasing stream order,while reed detritus decay rates generallyincreased on the same spatial gradient.Summer drought events affected these spatial patterns of variation by influencing significantly the decay rates of both plant detritus.The comparisons among and within sub-basins showed strong negative influence of summer drought on detritus processing rates.Similarly,in the entire River Tirso basin decay rates were always lower at disturbed than at undisturbed sites for each stream order;decay rates of reed detritus remained lower at those sites even after the end of the disturbance events,while alder decay rates recovered rapidly from the summer drought perturbations.The different recovery of the processing rates of the two leaves could also explain the different patterns of spatial variation observed between the two leaves.     

Radionuclide transfer to fruit in the IAEA TRS 364 Revision

Information on the transfer of radionuclides to fruits was almost absent in the former TRS 364 “Handbook of parameter values for the prediction of radionuclide transfer in temperate environments”. The revision of the Handbook, carried out under the IAEA Programme on Environmental Modelling for RAdiation Safety (EMRAS), takes into account the information generated in the years following the Chernobyl accident and the knowledge produced under the IAEA BIOMASS (Biosphere Modelling and Assessment) Programme in the years 1997–2000. This paper describes the most important processes concerning the behaviour of radionuclides in fruits reported in the IAEA TRS 364 Revision and provides recommendations for research and modelling.