The large wetland area with its numerous aquifers in the extreme south of the Ljubljana basin is a very important water resource with very complicated hydrological structure. Tritium and oxygen isotope composition were therefore determined, beside others parameters such as concentrations of gamma-ray emitters and geochemical parameters (Ca2+, Mg2+, Na+, K+, Cl-, SO4 2-, NO3-, HCO3. Conductivity, pH, H-2). Obtained results confirmed existance of many different types of groundwaters in the basin and clarify the status of lower aquifers.
The requirement that the true value of an anctivity cannot be negative is used for transformation of raw observed values into expected activity values. The probability distribution of the activity values is a truncated normal distribution and the expected value and the variance of the activity value are derived from the observed value and its standard deviation. It has been shown that the standard deviation of the activity value is less than the standard deviation of the observed value and that the ratio of the standard deviation of the activity value and the expected value is less than one.
The article presents the application of isotope methods in the study of groundwater transport processes in the unsaturated zone of the Selniška Dobrava coarse gravel aquifer. The estimation of groundwater flow characteristics was based on experimental work in lysimeter. Based on long-time isotope investigations with the use of lumped parameter models, mean residence time and mean matrix flow velocity in the aquifer unsaturated zone were calculated.
Activity concentrations of 40K and 3H in drinking water from four sources in the vicinity of NPP Krško for the period from 1996 to 2010 are presented. Their correlation with geological data confirmed the presence of at least two different aquifers. Activites are compared with 77 sources of drinking water from other parts of Slovenia. These activities concentrations vary by more than an order of magnitude. The largest values were found in northeastern part of the country.
A method for measuring the low-activity concentration of 238U in water is described. Samples of 50 L were evaporated and the dry residue after evaporation was measured. Typically, 30 g of material was obtained for the samples processed in this way. The decision threshold resulting from gamma-ray spectrometric measurements was assessed to 1.5 Bq/m3. A total od 26 samples of ground awter were processed and activity concentrations up to 20 Bq/m3 were measured. However, most of the results were in the range arround 5 Bq/m3.