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FZJ-2018-03657

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Untersuchungen zum Transfer des durch den Reaktorunfall von Tschernobyl abgelagerten Radiocaesiums vom Boden in die Pflanze

Bilo, M. (Corresponding author)FZJ*

1991
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich

Please use a persistent id in citations: http://hdl.handle.net/2128/19052

Report No.: Juel-2546

Abstract: In 1988 and 1989 soil and winter cereals were sampled in Upper Swabia and North Rhine-Westphalia (NRW) in order to measure the radionuclides $^{134}$Cs $^{137}$Cs and $^{40}$K contained in them. Transfer factors Soil-to-Plant (TF$_{sp}$) were determined for radiocaesium in the grain and straw of winter barley and winter wheat. TF$_{sp}$ are defined by the ratio of the concentration of a radionuclide in fresh plant material to its concentration in dry soil. These factors are of particular interest for long-lived radionuclides because of the possible additional radioactive dose received from consuming contaminated foodstuffs. Due to the low deposition of radiocaesium in NRW after the Chernobyl accident of about 2500 Bq $^{137}$Cs/m$^{2}$ and 720 Bq $^{134}$Cs/m$^{2}$, radiocaesium was not detectable in cereals from NRW and the calculation of TF$_{sp}$ was impossible. In contrast to this, a deposition of about 44,100 Bq $^{137}$Cs/m$^{2}$ and 13,500 Bq $^{134}$Cs/m$^{2}$ was calculated for the vicinity of Tannheim, a village in Upper Swabia. Nevertheless, the content of radiocaesium in grain from Upper Swabia was found to be more than one hundred times lower than that of natural $^{40}$K. TF$_{sp}$ for radiocaesium were determined for cereals from the three investigated soil types : Kalkvega (FAO classification : Calcaric Fluvisol), Braunerde (Cambisol) and Parabraunerde-Pseudogley (Luvisol-Planosol). The total variation in TF$_{sp}$ from 54 sampling sites was a factor of 43 (grain) and 18 (straw). However, the values did not reach the calculation basis of the GermanRegulatory Guide of 0.05 (Allgemeine Berechnungsgrundlage). The maximum TF$_{sp}$ for $^{134/137}$Cs in grain of 0.026 is clearly below that limit. The detection of a possible uniform behaviour of radiocaesium in the respective soil type as well as the definition of "typical" TF$_{sp}$ for the well delimited soil types is masked due to the varying nutrient status of arable soils. The variation of TF$_{sp}$ can be explained almost completely by the content of exchangeable and plant-available potassium in the soil. Other soil parameters like pH-value, organic matter content or soil texture did not show any influence on the TF$_{sp}$ because they did not reach extreme values. In contrast to these soil parameters, the potassium content is a less consistent, fast changing soil property. A simple non-linear regression using an exponential model on the exchangeable potassium content in soil explains 57 % of variance of TF Soil-to-Grain for samples from 1988 and 79 % of variance of TF Soil-to-Grain for the 1989 harvest. in the time after the Chernobyl accident a drastic increase of radioactivity in sewage sludge was observed in Upper Swabia. In the Tannheim sewage plant a radiocaesium content of about 12,500 Bq/kg dry matter was measured. In order to obtain further information on the possible radioecological consequences of using this sewage sludge as fertilizer a lysimeter study was carried out with application of the contaminated sewage sludge. Radioactivity in soil and several crops was measured for the growing periods 1989 and 1990. Although the soil type ("worst-case model") could have led one to expect high TF$_{sp}$ the increase of radiocaesium in plants was quite small. A higher uptake of radiocaesium by plants is caused by varying the potassium contents of the soil rather than by the application of the contaminated sewage sludge.

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