20.500.12556/RUL-133790 Comparison of uranium isotopes and classical geochemical tracers in karst aquifer of Ljubljanica River catchment (Slovenia) The karst aquifer of the Ljubljanica River catchment, which has numerous springs and sinks, presents an interesting environment for studying hydrogeological processes. This study aims to explore the behavior of U isotopes and to evaluate their use as tracers of hydrogeochemical processes as an alternative to classical geochemical tracers (i.e., physicochemical parameters, elemental ratios, and alkalinity) involved in water–rock interactions and water flow in this karst water system. Basic hydrochemical parameters, as well as the spatiotemporal variations of total U concentrations, $^{234}$U/$^{238}$U activity ratios, and δ $^{238}$U values, were monitored in water samples from springs and sinks under different hydrological conditions. The bedrock as the source of dissolved and detrital U was also analyzed. Multi-collector inductively couple plasma-mass spectrometry results reveal variations of the $^{234}$U/$^{238}$U activity ratios, which are consistently negatively correlated with the discharge at most analyzed sites. Large $^{238}$U/$^{235}$U isotope fractionation occurred during bedrock weathering, and the large variability of the measured δ$^{238}$U values is seemingly unrelated to the lithological characteristics of the bedrock or discharge. Our results confirm that $^{234}$U/$^{238}$U activity ratios in water can be used as a tracer for studying changes in groundwater flows and the mixing of waters of different origins under different hydrological conditions. karst aquifer uranium isotopes groundwater Ljubljanica River catchment true false true Angleški jezik Ni določen Članek v reviji 2021-12-15 10:55:35 2021-12-15 10:55:36 2022-09-13 03:52:39 0000-00-00 00:00:00 2020 0 0 29 str. iss. 7, art. 2064 Vol. 12 2020 0000-00-00 Zaloznikova Objavljeno NiDoloceno 0000-00-00 0000-00-00 0000-00-00 502/504 2073-4441 10.3390/w12072064 24241155 RAZ_Rovan_Leja_2020.pdf RAZ_Rovan_Leja_2020.pdf 1 C1F47C2751BE1F36E9F71F75B7A14C9E 7ba77c3280dc6cc000613d9620b7622de2125660b1eecb6d22a0c5c156ae34b0 3ad2f3f3-5d8d-11ec-abdb-00155dcfd717 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=152125 https://www.mdpi.com/2073-4441/12/7/2064 0 2d7aa1b9-5d8d-11ec-abdb-00155dcfd717 https://repozitorij.uni-lj.si/Dokument.php?lang=slv&id=152124 Fakulteta za gradbeništvo in geodezijo 0 0 0