The stable isotopic composition of hydrogen and oxygen (δ2H and δ18O) and the tritium activity (A) were monitored in monthly collected precipitation at Ljubljana (Reaktor) during the period 2007-2010. Monthly and yearly isotope variations are discussed and compared with those observed over the period 1981-2006 and with the basic meteorological Parameters for Ljubljana (Bežigrad) and Ljubljana (Hrastje) stations for the period 2007-2010. The mean values for δ2H and δ18O, weighted by precipitation amount at Ljubljana (Reaktor), are -59.4 ‰ and -8.71 ‰. The reduced major axis local meteoric water line (LMWLRMA) is δ2H = (8.19 ± 0.22)×δ18O + (11.52 ± 1.97), while the precipitation weighted least Square regression results in LMWLPWLSR-Re δ2H = (7.94 ± 0.21)×δ18O + (9.76 ± 1.93). The lack of significant difference in the LMWL slopes indicates a relatively homogeneous distribution of monthly precipitation as well as the small number of low-amount monthly precipitation events with low deuterium excess. The deuterium excess weighted mean value is 10.3 ‰ which indicates the prevailing influence of the Atlantic air masses. The temperature coefficient of δ18O is 0.30 ‰/°C. Tritium activity in monthly precipitation shows typical seasonal variations, with a weighted mean tritium activity in this period of 8.5 TU. No decrease of mean annual activity is observed.
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