No abstract

This study elucidates the importance of assessing mass biases due to sample pre-treatment for uranium isotope ratio analysis.

Activity concentration of (238)U, (234)U, (226)Ra, (228)Ra, (210)Pb and (210)Po in tap water from selected springs and private wells in the area of the former uranium mine at Žirovski Vrh were determined. A total of 22 tap water samples were collected at consumer's houses. The results show that the activity concentrations of uranium in water samples are in range (0.17-372) and (0.22-362) mBq L(-1) for (238)U and (234)U, respectively. Radium activity concentrations are in range (0.14-16.7) and (0.9-11.7) mBq L(-1) for (226)Ra and (228)Ra, respectively. (210)Po activity concentration is in range (0.28-8.0) mBq L(-1) and can be regarded as the lowest amongst all analysed radionuclides. The range for (210)Pb is (0.5-24.6) mBq L(-1). Based on the results obtained for activity concentrations of six radionuclides, the committed effective dose for three different age groups of population were estimated. It was found that the committed effective dose was well below the recommended value of 100 μSv year(-1), ranging from 2.3 to 34.3 μSv year(-1) for adults, from 3.5 to 32.0 μSv year(-1) for children (7-12 years) and from 3.0 to 23.3 μSv year(-1) for infants.

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, 234U/238U activity ratios, and δ238U 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 234U/238U activity ratios, which are consistently negatively correlated with the discharge at most analyzed sites. Large 238U/235U isotope fractionation occurred during bedrock weathering, and the large variability of the measured δ238U values is seemingly unrelated to the lithological characteristics of the bedrock or discharge. Our results confirm that 234U/238U 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.