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MS: Fachverband Massenspektrometrie
MS 9: Accelerator Mass Spectrometry IV
MS 9.2: Vortrag
Freitag, 15. März 2024, 11:30–11:45, HS 3042
Environmental 99Tc concentrations determined by AMS — •Karin Hain1, Stephanie Adler1, L. Keith Fifield2, Fadime Gülce1, Martin Martschini1, Stefan Pavetich2, Stephen G. Tims2, and Robin Golser1 — 1University of Vienna, Faculty of Physics, Austria — 2Australian National University, Research School of Physics, Australia
In the last 4.5 years we have intensively studied possibilities of analyzing environmental concentrations of the anthropogenic radionuclide 99Tc (t1/2 =2.1·105 yr) with AMS. The applied techniques for isobar suppression comprised the gas-filled analyzing system (GAMS) at the TU Munich and an 8-anode ionization chamber at the Australian National University (ANU, Canberra), both using a tandem accelerator with a terminal voltage of up to 14 MV. Experiments using the 3 MV tandem at VERA investigated the application of Ion-Laser InterAction Mass Spectrometry (ILIAMS). While all three methods achieved a 99Ru suppression that enabled detection of Tc from global fallout, i.e. a blank level below 5·106 at/sample, none of them could make use of the 97Tc spike added for normalization to obtain absolute concentrations owing to its omnipresent isobar 97Mo. At ANU, we have followed the example of TU Munich and used the 93Nb12+ current for normalization, achieving a precision of 15% when extracting TcO− and NbO− from the ion source. This allowed the determination of the 99Tc concentration in selected samples from different environmental reservoirs, including 1 g peat bog samples and 10 L water samples from the Pacific Ocean and European rivers.
Keywords: Technetium-99; global fallout; peat bog; Pacific Ocean