Spatial variability of fallout-90Sr in soil and vegetation of an alpine pasture

According to the soil-to-plant transfer concept generally used in dose assessment modeling, the plant uptake of a radionuclide should depend linearly on its concentration in the soil. In order to validate this concept for 90Sr in a semi-natural ecosystem, plant and soil samples were taken at 100 plots of a 100×100 m2 area within an alpine pasture near Berchtesgaden, Germany. At three plots, the vertical distribution of 90Sr in the soil was determined in addition. A statistically significant correlation between the soil and plant concentration of 90Sr was not detectable (Spearman correlation coefficient R=−0.116, p>0.05) within the range of the Sr-concentration covered (15–548 Bq kg−1 dry soil and 17–253 Bq kg−1 dry plant material). Thus, the prerequisite of the soil-to-plant transfer concept was not fulfilled for 90Sr at this site. Organic carbon and total nitrogen were also determined in the soil samples. Both elements were highly correlated (R=0.912, p<0.001), their ratio being C/N=10.9±0.7. While C was positively correlated with the 90Sr concentrations in the soil (R=0.342, p<0.001), negative correlations were observed for the plant concentrations (R=−0.286, p<0.01) and the concentration ratios (R=−0.444, p<0.001) of 90Sr. These results are compared with those recently obtained for 137Cs by Bunzl et al. (J Environ Radioactiv 48 (2000) 145).