Cesium and cobalt transfer from soil to vegetation on permanent pastures.

The Cs transfer from soil into pasture vegetation was investigated by using a variation of experimental conditions: (I) 67 pots with 7 kg soil from 3 marshy and 1 sandy site in the lower Weser region in Northwest Germany are used in a greenhouse with 134Cs under 8 different experimental procedures for 2 harvests; (II) 3 undisturbed 50 kg lysimeters were observed for 137Cs and 60Co transfer under outdoor conditions for 4 harvests, depth profiles of the activity were determined afterwards; (III) the transfer of the atmospheric fallout 137Cs directly to the vegetation and from soil to vegetation after preventing its direct uptake by plastic covers was determined at 4 locations in the open pasture. The experiments resulted in higher Cs transfer in the case of podzolic soil and/or direct injection of Cs solution into the rooting zone of old permanent pasture vegetation while the Cs transfer was about 2-4 fold lower when the radioactive solution was applied to newly sown grass. Transfer often decreases with increasing age of Cs in the soil. In addition, statistical analysis of the widely scattered data did not show significant results for the influence of type of marsh, experimental procedure, soil factors with pH of (4.5-6.1), organic carbon, amount of added Cs (microquantity), exchangeable, K, and total Ca. Some figures are given for 60Co. The observed transfer factors, combined from all experiments appear lognormally distributed with median values 0.22 on podzolic and 0.09 on marshy soils (Bq/kg fresh plant per Bq/kg air dried soil).