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Modeling of Cs-137 input into the sediment and its vertical distribution within the sediment of a shallow eutrophic lake (Kongressschrift / Tagungsband) - Detailansicht


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Titel der Arbeit (title) Modeling of Cs-137 input into the sediment and its vertical distribution within the sediment of a shallow eutrophic lake
Titel der Zeitschrift bzw. Zeitung Book of abstracts and programm of the Second International Conference on Radioecological Concentration processes (50 years later)
Erscheinungsjahr 2016
Seitenzahl (pages) 164
Publikationsart Kongressschrift / Tagungsband
Inhalt
Abstract In order to determine the accumulation of 137Cs from the watershed into the sediment of a shallow eutrophic lake (Vorsee, Southern Germany) the following quantities were measured: 137Cs inventory in the soil of the catchment area, 137Cs activity concentration in water and suspended matter (1988–2016), vertical distribution of the activity in several sediment profiles together with bulk density and portion of exchangeable 137Cs activity.
To describe the input of 137Cs into the sediment and its vertical distribution within the sediment, a sedimentation-diffusion model is developed and implemented in the Matlab software. The model consists of two coupled differential equations describing portions of exchangeable and fixed 137Cs in sediments and comprises terms for fixation, redissolution, sedimentation, retarded diffusion of the exchangeable 137Cs, bioturbation of the total 137Cs, as well as radioactive decay. To solve the differential equations a finite differences method is applied. As a boundary condition the time-dependent 137Cs activity concentration in the lake water described by the Aquascope model (J. Smith) is used. The output of the Aquascope model for the atmospheric nuclear weapons testing and Chernobyl fallouts is calibrated with measured data. It is assumed that the exchangeable activity of the suspended matter is in immediate equilibrium with the water and that the fixed activity increases with the fixation rate f taken from literature. The suspended matter then transports the activity to the sediment. One free parameter of the model is the distribution coefficient KD, and it is compared to the KD-data measured in the water column. Other free parameters are sedimentation rate RS and bioturbation coefficient Dbio. For Dbio a certain depth dependence has to be chosen.
It will be shown that the model is able to describe the broad distribution of 137Cs within sediments of a shallow eutrophic lake where 137Cs is mostly bound on organic matter and its fixation on clay minerals is of less importance. The model output also describes the time-dependent total 137Cs inventory in the sediment of the lake.

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Beteiligte Personen (intern)

 
 
Klemt, Eckehard, Professor Dr. rer. nat.  
 

Einrichtungen

Bachelorstudiengang Energie- und Umwelttechnik
Fakultät Technologie und Management
Hochschule Ravensburg-Weingarten
Institut für Angewandte Forschung (IAF)
Masterstudiengang Umwelt- und Verfahrenstechnik
Schwerpunkt Energie und Umwelt (IAF)

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