Isotopic composition of precipitation at the Station Portorož, Slovenia - period 2007-2010

Abstract

The stable isotopic composition of oxygen and hydrogen (δ18O and δ2H) and the tritium activity (A) were monitored in precipitation at synoptic Station Portorož (Slovenia) during the period 2007-2010. Monthly and yearly isotope variations are discussed and compared with those observed over the period 2001-2006 and with the basic meteorological parameters. The mean values for δ18O and δ2H, weighted by precipitation, are -6.28 ‰ and -41.6 ‰, and these values are 0.35 ‰ and 1.6 ‰ higher but not significantly different than for the period 2001-2006. The reduced major axis (RMA) local meteoric water line (LMWLRMA) for the period 2007-2010 is δ2H = (8.14 ± 0.25)x δ18O + (8.28 ± 1.64), while the precipitation weighted least square regression (PWLSR) results in LMWLPWLSR δ2H = (7.87 ± 0.28) δ18O + (7.97 ± 1.87). The deuterium excess (δ) weighted mean value is 8.6 ‰ and is 1.2 ‰ lower than in 2001-2006, while the temperature coefficient of δ18O is 0.21 ‰/°C and is for 0.02 ‰/°C higher than for the previous period. The mean Mediterranean precipitation index (MI) for the period 2007-2010 is 2.3. Lower values of MI and deuterium excess than in the preceding period indicate stronger continental climatic character during Observation period, however the differences are not statistically significant. The weighted mean tritium activity is 6.4 TU, which is 0.5 TU lower but not significantly different than in 2001-2006.