Role and uncertainty of foliar transfer in radiological impact assessments: State of the art and future actions

Sensitivity analyses have shown major role of foliar transfer for many radionuclides in the context of radiological impact assessments. A review of the published literature about foliar transfer focusing on translocation factors was carried out in order to constitute an updated database on one hand and to use the appropriate existing values of translocation parameters for modeling on the other. Translocation describes the distribution of radionuclides within the plant after foliar deposition and radionuclide absorption onto the surface of leaves. It mainly depends on elements and the plant growth stage. The collected data was derived from both in-field and greenhouse experiments. It was analysed to select those coming from a contamination simulating sprinkling irrigation or rain. This work not only allowed us to carry out a diagnosis on the values themselves but also enabled us to ascertain missing data needs. In order to compensate for the lack of data on important radionuclides concerning radioactive waste (129I, 36Cl, 79Se), experimental studies have been launched

Late contralateral hyperhidrosis in lateral medullary infarcts.

This study describes unilateral increases of sweating reactions observed in the months after contralateral medullary infarct; evaluation of sympathetic cutaneous response may help to explain sweating disorders. After the discovery of the clinical phenomenon in one case, patients admitted between 1990 and 1993 were systematically evaluated clinically and electrophysiologically. In a group of five patients presenting with lateral or dorsal medullary lesions, two exhibited an increase of contralateral sweating reactions that appeared 6 to 8 months after stroke, were elicited by effort and exposure to heat and stress, and were more severe over the forehead, face, and upper trunk. In one case, this was clinically associated with an absence of sweating on the side of the lesion. During the late phase after stroke, in three patients presenting with lateral medullary lesions, electrophysiological evaluation revealed significant asymmetry of the sympathetic skin response, which was higher on the side contralateral to the lesion than on the ipsilateral side. In one patient, no response could be elicited by stimulations applied on the side of the lesion. Contralateral hyperhidrosis can be observed in the late phase after lateral medullary infarct and is likely due to lesion of the sympathetic pathway passing through the lateral medulla, which inhibits sudomotor neurons. Evaluation of sympathetic skin response may help to explain such clinical disorders

Influence d'acides organiques sur la désorption de l'américium 241 et du neptunium 237 à partir d'un sol cultivé acide

Effect of organic acids on 241 americium and 237 neptunium desorption from an acidic cultivated soil. Naturally occurring organic substances have been recognised as one important factor affecting the behaviour in the environment of transuranic actinides. This experimental study aims at evaluating if some naturally occurring carboxylic acids (vanillic, citric, lactic, oxalic) would affect 241Am or 237Np availability in an acidic agricultural soil. Data show that these acids enhance the desorption of americium and neptunium from the soil, with a noticeable effect of citric acid. The fraction desorbed is multiplied by more than 10 for 0.1 M citric acid, and by 3 or 4 with other acids, in relation with the complexation of radionuclides with these acids. The desorption increases with molar concentration of the acids because of the decrease of pH in acidified soils, except for oxalic acid. The soil moisture conditions seem to affect the desorption results: the percentage desorbed is approximately 10 times lower for batch experiments (saturated conditions) than for centrifugation corresponding to unsaturated soil conditions. These preliminary data are mainly qualitative, but they show that it could be interesting to take into account more realistic physico-chemical conditions when measuring desorption ratios for cultivated soils

Root uptake by cultivated vegetables of radionuclides coming from contaminated algae used as organic manure in soil

In certain areas of the French Atlantic coast, algae of marine origin are used as organic fertilizer, particularly for vegetables cultivation. An experiment was carried out to estimate the transfers of radioactivity towards agricultural productions, which could result from this practice in the case where algae were contaminated. Algae (fucus vesiculosus) were cultivated in aquarium with seawater containing a mixture of radionucléides : 22Na, 60Co, 90Sr, 99Tc, 106Ru, 125Sb, 134, 137Cs, 238, 239+240Pu, 241Am, 244Cm. These algae were mixed, in a lysimeter, with a silty-sandy soil. Some vegetables, potatoes, lettuces, radishes, beans, tomatoes were cultivated on this manured soil. The soil to plant concentration ratios are given for the edible organs of the plants grown the year following the addition of algae in the soil and for cultures made several years later. On the other hand chemical extractions were performed to evaluate the bioavailable fraction of radionuclides in the soil

Root uptake by cultivated vegetables of radionuclides coming from contaminated algae used as organic manure in soil

In certain areas of the French Atlantic coast, algae of marine origin are used as organic fertilizer, particularly for vegetables cultivation. An experiment was carried out to estimate the transfers of radioactivity towards agricultural productions which could result from this practice in the case where algae were contaminated. Algae (fucus vesiculosus) were cultivated in aquarium with sea water containing a mixture of radionucléides: 22Na, 60Co , 90Sr, 99Tc , 106Ru , 125Sb, 134,137Cs , 238,239+240Pu, 241Am , 244Cm. These algae were mixed, in a lysimeter, with a silty-sandy soil. Some vegetables, potatoes, lettuces, radishes, beans, tomatoes were cultivated on this manured soil. The soil to plant concentration ratios are given for the edible organs of the plants grown the year following the addition of algae in the soil and for cultures made several years later. On the other hand chemical extractions were performed to evaluate the bioavailable fraction of radionuclides in the soil

Translocation of 125I, 75Se and 36Cl to Wheat edible parts following wet foliar contamination under field conditions

International audienceApart from radiocaesium and radiostrontium, there have been few studies on the foliar transfer of radionuclides in plants. Consequently, specific translocation factor (ftr) values for 129I, 79Se and 36Cl are still missing from the IAEA reference databases. The translocation of short - lived isotopes, 125I and 75Se, and of 36Cl to wheat grain were measured under field conditions following acute and chronic wet foliar contamination at various plant growth stages in the absence of leaching caused by rain. The translocation factors ranged from 0.02% to 1.1% for 125I (a value similar to Sr), from 0.1% to 16.5% for 75Se, and from 1% to 14.9% for 36Cl. Both 36Cl and 75Se were as mobile as Cs. The phenomenological analysis showed that each element displayed a specific behavior. Iodide showed the lowest apparent mobility because of its preferential fixation in or on the leaves and a significant amount probably volatilized. Selenite internal transfer was significant and possibly utilized the sulphur metabolic pathway. However bio - methylation of selenite may have led to increased volatilization. Chloride was very mobile and quickly diffused throughout the plant. In addition, the analysis underlined the importance of plant growth responses to annual variations in weather conditions that can affect open field experiments because plant growth stage played a major role in ftr values dispersion. The chronic contamination results suggested that a series of acute contamination events had an additive effect on translocated elements. The highest translocation value obtained for an acute contamination event was shown to be a good conservative assessment of chronic contamination if data on chronic contamination translocation are lacking. The absence of rain leaching during the experiment meant that this investigation avoided potential radionuclide transfer by the roots, which also meant that radionuclide retention on or in the leaves was maximized. This study was therefore able to obtain accurate translocation factors, which are probably among the highest that could be recorded. © 2012 Elsevier Ltd