Distribution of the radionuclide Cs-137 in the soils of a wet mountainous forest in Taiwan

The behavior of Cs-137 was studied in the Yuanyang lake ecosystem, a wet mo untainous forest in subtropical Taiwan. Soils investigated are either parti ally podzolic soils or nearly pure pears with a high organic matter concent ration in the surface layer. Concentration of Cs-137 was highest in the: or ganic surface layers, particularly in the Oe horizon or in the underlying A horizon. The downwards migration to the mineral horizons is limited, in sp ite of the high rainfall. Topography is a critical factor for the distribut ion of Cs-137. It is shown that the concentration of Cs-137 is highest at t he foot of the slope and lower near the summit and near the lakeshore. The variation of the concentration along the landscape has been attributed to e rosion-deposition in combination with surface run-off of the undisturbed fo rest. The amount of Cs-137 in he site studied is significantly higher than at any other place in Taiwan. The accumulation of Cs-137 is attributed to t he high rainfall, which brought large amounts of Cs-137 With the precipitat ion in the early 1960s. A very remarkable feature of the ecosystem is that Cs-137 is not leached to the subsoils, but is stored in the biomass. Due to permanent recycling it remains available, without being leached downward. (C) 1999 Elsevier Science Ltd. All rights reserved.