Heidelberg 2006 – wissenschaftliches Programm
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UP: Umweltphysik
UP 2: Hydrosph
äre
UP 2.2: Fachvortrag
Montag, 13. März 2006, 16:45–17:00, A
Spatial distribution of helium in lacustrine sediments — •Yama Tomonaga1, Matthias S. Brennwald1, and Rolf Kipfer1,2 — 1Water Resources and Drinking Water, Eawag, Switzerland — 2Institute of Isotope Geochemistry and Mineral Resources, ETHZ, Switzerland
Conventional thinking argues that He degassing from solid Earth occurs very heterogeneous in the spatial domain and is focused on fractures zones in the crust. Lacustrine sediments in lakes represent an frame to assess the He emanation on relative small but defined spatial scales. The fluid transport in the sediment column can be described as an advective - diffusive transport where He migrates through the porewater phase of the sediment. Based on the gradient of the He concentrations within the sediment column the local He flux can be estimated at relative small spatial scales. Here we present the first He concentration data measured in two sediment cores from Lake Van (Turkey). One core being taken in a fracture zone transecting the lake basin shows a strong He gradient. The second core was taken far away from the fracture zone. There, the measured concentrations are much smaller and hardly any vertical He gradient could be observed. The results add direct experimental evidence to the hypothesis that He emanation is restricted on (large) fracture zone and does not occur homogeneous over the crust.