Uptake of Radionuclides by Bryophytes in the Chornobyl Exclusion Zone

The Chernobyl nuclear disaster released huge amounts of radionuclides, which are still detectable in plants and sediments today. Bryophytes (mosses) are primitive land plants lacking roots and protective cuticles and therefore readily accumulate multiple contaminants, including metals and radionuclides. This study quantifies Cs-137 and Am-241 in moss samples from the cooling pond of the power plant, the surrounding woodland and the city of Prypiat. Activity concentrations of up to 297 Bq/g (Cs-137) and 0.43 Bq/g (Am-241) were found. Cs-137 contents were significantly higher at the cooling pond, where Am-241 was not detectable. Distance to the damaged reactor, amount of original fallout, presence of vascular tissue in the stem or taxonomy were of little importance. Mosses seem to absorb radionuclides rather indiscriminately, if available. More than 30 years after the disaster, Cs-137 was washed out from the very top layer of the soil, where it is no more accessible for rootless mosses but possibly for higher plants. On the other hand, Cs-137 still remains solved and accessible in the cooling pond. However, Am-241 remained adsorbed to the topsoil, thus accessible to terrestrial mosses, but precipitated in the sapropel of the cooling pond.