Stuttgart 2012 – wissenschaftliches Programm
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MS: Fachverband Massenspektrometrie
MS 6: Poster
MS 6.1: Poster
Dienstag, 13. März 2012, 16:30–19:00, Poster.IV
A year-by-year record of 236U/238-U in coral as a step towards establishing 236-U from nuclear weapons testing fall-out as oceanic tracer — •Stephan Winkler1, Peter Steier1, and Jessica Carilli2 — 1University of Vienna, Faculty of Physics, Vienna, Austria — 2Australian Nuclear Science and Technology Organisation, Lucas Heights, Australia
Since uranium is known to behave conservatively in ocean waters, 236-U has great potential in application as oceanic tracer. 236-U (t1/2=23.4Ma) was introduced into the oceans by atmospheric nuclear weapon testing with amount estimates ranging from 700kg to 1500kg. Thus a resulting initial average 236-U/238-U ratio of at least 5e-9 is expected for an oceanic mixed layer depth of 100m. This ratio is already higher than the natural pre-nuclear background, which is expected to be at 10e-14 levels.
Even the elevated ratios of global stratospheric fall-out are beyond the capabilities of ICPMS and TIMS methods. However, the exceptional sensitivity and ultra-low background for 236-U of the Vienna Environmental Research Accelerator's Accelerator Mass Spectrometry system allows us to measure down to 10-13 detection limits.
We present a year-by-year record of 236-U/238-U for a Caribbean coral core covering years 1944 to 2006, thus allowing to us put constraints on the oceanic input of 236-U by atmospheric testing. Moreover modelling of the results also demonstrates the capabilities of 236-U as oceanic tracer.