Distribution of 210Ро in lichen thalli

Resumo

Distribution of ²¹⁰Po in thalli of soil and wood (epiphytic) lichens was studied. Four fractions containing the corresponding ²¹⁰Ро forms were obtained by sequential extraction: (1) intercellular, (2) extracellular, (3) intracellular, and (4) insoluble thallus residue. The ²¹⁰Ро uptake by lichens is mainly passive, as the total content of the radionuclide in fractions 1, 2, and 4 reaches 88–97%. From 3 to 12% of ²¹⁰Ро is taken up actively (fraction 3), and for soil lichens this parameter is approximately 2.75 times higher than for epiphytic lichens. Presumably, ²¹⁰Ро is supplied into soil and epiphytic lichens in the form of different chemical compounds and is therefore characterized by different bioavailability.