UPTAKE OF CS-134/CS-137 IN SOIL BY CEREALS AS A FUNCTION OF SEVERAL SOIL PARAMETERS OF 3 SOIL TYPES IN UPPER SWABIA AND NORTH-RHINE-WESTPHALIA (FRG)

In 1988 and 1989 soil and winter cereals contaminated with long-lived radionuclides derived from the accident at Chernobyl were sampled in Upper Swabia and North Rhine-Westphalia (NRW). Cs-134, Cs-137 and K-40 were measured and transfer factors Soil-to-Plant (TF(SP)) were determined for radiocaesium in the grain and straw of barley and wheat. Due to the lower deposition of radiocaesium in NRW after the Chernobyl accident, radiocaesium was not detectable in cereals from NRW. In samples from Upper Swabia, one of the most highly contaminated areas in Germany after the reactor accident (43 000 Bq Cs-137/m2), the concentration of radiocaesium in grain was found to be more than one hundred times lower than the concentration of natural K-40. The variation of TF(SP) by about a factor of 43 (grain) and 18 (straw) can be explained by the potassium content of the soil. TF(SP) values, show a pronounced increase below 0.2 meq exchangeable potassium/100 g soil, but do not exceed the value given as a basis for calculation in the German Regulatory Guide of 0.05 (Allgemeine Berechnungsgrundlage). Above the threshold of 0.2 meq K+/100 g, an additional supply of potassium has no effect. Other soil parameters, such as pH value, organic matter content or soil texture, did not have any influence on TF(SP). Possible differences between TF(SP) of the soil types investigated (Fluvisol, Cambisol, Luvisol-Planosol) are concealed by the differing nutrient status of arable soils.