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Tracing Environmental Radionuclides (40K, 226Ra, 210Pb And 137Cs) In Soil Under Coniferous Stands In The Czech Republic

Ryoko Fujiyoshi, Yoshihiro Satake, Takahiro Sato, Takashi Sumiyoshi, Sadashi Sawamura

Depth profiles of environmental radionuclides (40K, 226Ra, 210Pb, 137Cs) in forest soil provide information on the “in situ” situation occurring or having been occurred within a soil horizon of interest. Degree of soil homogeneity could appear on variability of depth profiles of lithogenic nuclides (40K and 226Ra). The level of 40K activity concentration is reflected by the underlying lithology. Change in its concentration with soil depth in the upper portion may suggests biological activity like root uptake of this nuclide. Fallout nuclides like 137Cs and a part of 210Pb did not always show the surface enrichment, which would be caused by bioturbation, surface runoff and/or canopy effect of the stands as well as anthropogenic intervention. Mean values of annual burial rate of 137Cs may roughly be estimated for several soils giving exponential decrease in activity concentration with depth within the upper 20 cm layer of the soil. The values were about 1-2 mm/y independent of the soil type. Similar values were also obtained from the 210Pb profiles at the same sites.