Ecological half-times of 137 Cs and 90 Sr in forest and freshwater ecosystems

More than 200 data sets from the literature of measured time series of activity concentrations and transfer factors concerning: (1) soil, green plants, mushrooms, and game in forests and (2) water, particulate matter, and fish in rivers, reservoirs and lakes in Europe have been analyzed. We used a sum of up to 3 exponential functions to evaluate ecological half-times (Teco). In fresh water systems we fitted lognormal distributions of Teco for 137 Cs (e.g. in the water of 32 European lakes, Teco1 = (0.3*2.2 ± 1 ) years and Teco2 = (5.7*3.9 ± 1 ) years as geometric mean value and standard deviation). Pronounced seasonal variations were observed in suspended matter of Lake Lugano, reflecting the bio-mass cycle of this lake. In forests, ecological half-times for 137 Cs can also be fitted by a lognormal distribution. For Central Europe Teco < 12 years. Extraordinarily high 137 Cs activity concentrations were observed recently in wild boar in Germany. For Eastern Europe the physical half-time is dominant and in some components of the ecosystem the activity concentration is still increasing.