München 2004 – wissenschaftliches Programm

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UP: Umweltphysik

UP 8: Hydrosph
äre und Boden II

UP 8.4: Fachvortrag

Montag, 22. März 2004, 17:15–17:30, HS 020

DATING OF YENISEI SEDIMENTS USING Po-210 ALPHA-SPECTROSCOPY — •Hanna Paliachenka, Eckehard Klemt, and Gregor Zibold — Fachhochschule Ravensburg-Weingarten, Doggenriedstr., D-88250 Weingarten

In 1999 and 2001 sediment samples were taken from various locations in the river Yenisei in central Sibiria and the vertical distribution of radionuclides was determined. Gamma-spectrometric dating of sediment layers of the river is not possible using the standard Pb-210 method (46.5 keV) due to the emission of 46.6 keV X-rays of the omnipresent Eu-152. Therefore, as Pb-210 and Po-210 (T1/2 = 138 d) are in radioactive equilibrium we extract only the unsupported Po-210 which is then measured alpha-spectrometrically. In this way systematic uncertainties due to the subtraction of concentrations determined by different methods are avoided. The results of these measurements are compared to other methods of dating using various isotope ratios and to the outcome of a model which describes the vertical distribution of radionuclides in the sediment.