Examination of a relationship between 137Cs concentrations in soils and plants from alpine pastures

An essential prerequisite of the soil/plant transfer factor concept is the presence of a statistically significant relationship between the contents of a given radionuclide in the soil and plant. To examine the existence of such an association for a semi-natural environment we determined for two typical alpine pastures in Germany and Italy the concentrations of fallout-137Cs in soil and plants. To be able to detect such a relationship sensitively, we selected at the German site 100 plots (area 1 mx1 m) within a 100 mx100 m area and assessed the corresponding plant and soil 137Cs contents. All frequency distributions of the soil and plant 137Cs contents at both sites were found to be lognormal. The results showed that increased plant 137Cs concentrations were not significantly associated with increased soil 137Cs contents, even though the 137Cs contents in the soil there varied by one order of magnitude. This result was also supported by the observations at the Italian pasture site, where 24 plots were selected. Possible reasons and consequences of these findings are discussed. To examine also the relation between potassium and radiocesium, 40K was determined in all samples. These results revealed a very strong but negative correlation between 40K and 137Cs in the plants of both pastures, which shows that, when a large variety of different plant species is considered, radiocesium and potassium do not necessarily behave in an analogous way. In addition, a statistically significant, negative relationship between 40K in the soil and 137Cs in the plants was found. Possible reasons for this observation are discussed