[Alpha-spectroscopic determination of 210Pb and 210PO in snow samples]

The concentrations of 210Pb and 210PO in several snow samples were determined using alpha-spectrometry. After 5 l of snow-melt water was subjected to coprecipitation of both nuclides with AlPO4, the solvent extraction procedure with TBP (tri-butyl phosphate)-isopropyl ether was applied to purify the polonium fraction, followed by the spontaneous electro-deposition on a Ni-sheet. The alpha-spectrum was measured with a Si(Au)-semiconductor detector coupled with a multichannel pulse-height analyzer. After the first determination of 210PO, the concentration of 210Pb was estimated from second measurement of 210PO grown newly from the remaining Pb-fraction during the storage period of more than 3 months. In these analytical procedures, 212Pb and 208PO tracers were conveniently utilized for the determination of collection yield for 210Pb and of the final chemical yield of 210PO, respectively. The contents of 210PO and 210Pb in the fresh snow were 3--30 mBq/l(81--810 fCi/l) and 250--720 mBq/l (6.8--19.5 pCi/l), respectively, and the residence time of 210Pb was given to be 6--12 days from the decay-growth relationships of both nuclides.