Berlin 2005 – scientific programme

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ST: Strahlen- und Medizinphysik

ST 6: Strahlenphysik: Retrospektive Strahlendosimetrie I

ST 6.4: Fachvortrag

Tuesday, March 8, 2005, 17:30–17:45, TU HL1

Progress in Modeling the Input and the Vertical Distribution of Cs-137 in Lake Sediments — •Viktorya Putyrskaya^1,2, Eckehard Klemt¹, and Gregor Zibold¹ — ¹FH Ravensburg-Weingarten, Doggenriedstr., 88250 Weingarten — ²International Sakharov Environmental University, Dolgobrodskaya str. 23, 220009 Minsk, Belarus

Our model consists of two coupled partial differential equations which describe the exchangeable and fixed parts of radioactivity in the sediment, respectively. It is based on sedimentation-diffusion equations and it also takes into account fixation and redissolution processes as well as radioactive decay. The input of activity is described by a distribution coefficient KD assuming that the activity concentration of the settling suspended matter is in equilibrium with the lake water. As a boundary condition it is required to know the activity concentration in the water for the integration period. The concentration of competing ions influences the distribution coefficient KD within the sediment where it is responsible for the retarded diffusion. Also the compaction of sediments with depth is taken into account via the measured distribution of bulk density. If larger turbidites are identified on photos of sediment cores and in the distributions of bulk density and of unsupported Pb-210, extra terms are incorporated in the differential equations for their descriptions. To solve this system a finite element method is used. Results for sediments of Lago Maggiore will be shown.