Uranium concentrations in sediment pore waters of Lake Neusiedl, Austria

The goal of the present investigation was to measure ²³⁴U/²³⁸U activity ratios in pore waters of Lake Neusiedl, Austria, in order to learn more about uranium in groundwaters of the Lake Neusiedl/Seewinkel region. Pore waters of waterlogged sediments (at 1m depth) in the littoral zone of Lake Neusiedl were analyzed. The pore water samples were collected in the National Park Lake Neusiedl/Seewinkel from pristine sites that were not influenced by neighboring fertilized fields or vineyards. Uranium isotopes were extracted from 1.5L of sediment pore water and measured by α-particle spectrometry. Uranium concentrations were found to be unexpectedly high (up to 853μgL^-1) especially in pore waters of salt-rich locations. ²³⁴U/²³⁸U activity ratios were between 0.91 and 1.09 for all pore water samples, irrespective of their origin from the east or west littoral zones of the lake. Uranium and mineral salts concentrations were strongly correlated. ²²²Rn concentrations were low (between 22 and 42BqL^-1). The results provide insight into the high degree of mobility of U(VI) in sedimentary environments, in the presence of migrating Na₂SO₄-type saline waters.