|Autoren des Beitrags|
|Titel des Beitrags||How to get maximal information from an excess Pb-210 vertical distribution of a sediment core samples in the Ruiru-Reservoir, Kenya, close to the equator|
|Titel veröffentlicht in ...||Book of abstracts of the 4th International Conference on Polonium and Radioactive PB Isotopes|
|Erscheinungsjahr||2019||Seite (von - bis)||47||Publikations-Art||Kongressschrift / Tagungsband|
|Abstract :||It will be shown that with the piecewise Constant Rate Supply (pwCRS) model of Appleby (2001) usually reasonable depth age relations can be derived for sediment cores of European prealpine lakes. Typically, the intervals of piecewise constant rates are taken between sampling and 1986 (Chernobyl), between 1986 and 1963 (NWT), and before 1963. In the approximation of the pwCRS model, short term deviations from an exponential 210Pb-decrease are due to variations in the sedimentation rate whereas long term deviations are due to a change in the 210Pb supply rate.
As the Ruiru-Reservoir is located close to the equator, 137Cs from Chernobyl is not present and the nuclear weapons testing 137Cs gives only little, statistically limited information. Moreover, the imprint of the transition from soil to sediment after flooding the reservoir in 1949 in the sediment core has to be discussed with respect to lamination, 210Pb, magnetic susceptibility and 40K.
In contrast to the pwCRS model, we assign individual sedimentation rates and 210Pb-fluxes to each sediment layer having measured their density and 210Pb activity concentration. Moreover, some interdependencies of sedimentation rate and 210Pb-flux in the determination of e.g. age or activity concentration of the sediment layers are used as further restrictions in the optimisation of sedimentation rates and 210Pb-fluxes.
As we have just one long time interval from 2017 down to 1949, statistical reasons may lead to the occurrence of negative activity concentrations of the excess 210Pb at larger depths, which have to be dealt with. The solution is the limited use of sliding averages with boundary conditions, which ensure that the total activity is not influenced.
Results of parameter optimization of this procedure will be shown and depth-age relations of the Ruiru-sediment based on different assumptions will be discussed and compared to that of other sediments.
Appleby, P.G., 2001. Chronostratigraphic technique in recent sediments. In: W.L. Last and J.P. Smol (Eds.), Tracking Environmental Change Using Lake Sediments, Volume 1: Basin Analysis, Coring, and Chronological Techniques. Kluwer Academic Publishers, Dordrecht, The Netherlands, pp. 171203.
Bachelorstudiengang Physikalische Technik
Fakultät Technologie und Management
Institut für Angewandte Forschung (IAF)
Schwerpunkt Energie und Umwelt (IAF)
Dr. rer. nat.
Radioökologische Studien und Untersuchungen