The stable isotopic composition of hydrogen and oxygen (δ 2 H and δ 18 O) and tritium activity ( 3 H) are monitored in monthly precipitation at Ljubljana since 1981. Here we present complete set of numerical data and the statistical analysis for period

The stable isotopic composition of hydrogen and oxygen (δ O + (9,76 ± 1,93). Nakloni izra~unanih premic so si med seboj podobni, kar nakazuje, da je porazdelitev padavin relativno homogena in da je {tevilo mese~nih vrednosti z nizkim devterijevim presežkom majhno. Srednja tehtana vrednost devterijevega presežka zna{a 10,3 ‰ in nakazuje prevladujo~i vpliv zra~nih mas iz Atlantika.Temperaturni koeficient za δ 18 O pa zna{a 0,30 ‰/°C. Tudi podatki o aktivnosti tricija v mese~nih padavinah kažejo sezonske spremembe. Srednja tehtana vrednost zna{a 8,5 TU in ne nakazuje padajo~ega trenda.

The stable isotopic composition of oxygen and hydrogen (δ 18 O and δ 2 H) 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 δ 18 O and δ 2 H, 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 (LMWL RMA) for the period 2007-2010 is δ 2 H = (8.14 ± 0.25)×δ 18 O + (8.28 ± 1.64), while the precipitation weighted least square regression (PWLSR) results in LMWL PWLSR δ 2 H = (7.87 ± 0.28)×δ 18 O + (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 δ 18 O 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. Izvleček V prispevku obravnavamo izotopsko sestavo kisika in vodika (δ 18 O in δ 2 H) ter aktivnosti tricija (A) v mesečnih vzorcih padavin, ki smo jo spremljali na sinoptični postaji Portorož (Slovenija) v obdobju 2007-2010. Analizirali smo mesečne in letne spremembe izotopske sestave padavin in jih primerjali z nizom podatkov za obdobje 2001-2006 ter z osnovnimi meteorološkimi parametri. Srednje tehtane vrednosti δ 18 O in δ 2 H določene ob upoštevanju izmerjene količine padavin znašajo

Abstract. Tritium (3H) as a constituent of the water molecule is an important natural tracer in hydrological sciences. The anthropogenic tritium introduced into the atmosphere unintentionally became an excellent tracer of processes on a time scale of up to 100 years. A prerequisite for tritium applications is to know the distribution of tritium activity in precipitation. Here we present a database of isoscapes derived from 41 stations for amount-weighted annual mean tritium activity in precipitation for the period 1976 to 2017 on spatially continuous interpolated 1 km×1 km grids for the Adriatic–Pannonian region (called the AP3H_v1 database), with a special focus on post-2010 years, which are not represented by existing global models. Five stations were used for out-of-sample evaluation of the model performance, independently confirming its capability of reproducing the spatiotemporal tritium variability in the region. The AP3H database is capable of providing reliable spatiotemporal input for hydrogeological application at any place within Slovenia, Hungary, and their surroundings. Results also show a decrease in the average spatial representativity of the stations regarding tritium activity in precipitation from ∼440 km in 1970s, when bomb tritium still prevailed in precipitation, to ∼235 km in the 2010s. The post-2010 isoscapes can serve as benchmarks for background tritium activity for the region, helping to determine potential future local increases in technogenic tritium from these backgrounds. The gridded tritium isoscape is available in NetCDF-4 at https://doi.org/10.1594/PANGAEA.896938 (Kern et al., 2019).

The stable isotopic composition of hydrogen and oxygen (d O pa zna{a 0,13 ‰/°C. Srednja tehtana vrednost devterijevega presežka (deuterium excess) zna{a 9,8 ‰ in se spreminja sezonsko ter odraža vpliv razli~nih zra~nih mas (atlantskih ali sredozemskih). Tudi aktivnost tricija v mese~nih padavinah kaže sezonske spremembe. Srednja tehtana vrednost zna{a 6,9 TU.

ABSTRACT. Anthropogenic activities that introduce an excess of nutrients and other pollutants into rivers and lakes are causing significant changes in their aquatic environment. Excessive nutrients greatly accelerate eutrophication, and lake marl formed during eutrophication differs from that formed in oligotrophic water.We analyzed recent sediment cores from Prone and Kozjak lakes located in Plitvice National Park, central Croatia.Analyses consisted of 14C activity of calcareous lake marl, the ratio of stable isotopes (b13C, 5180), organic compounds in the sediment and the distribution of diatoms. Previous 14C activity measurements helped to determine the sedimentation rate and thus the time period of increased input of nutrients into lakes. We determined the increased 14C activity in lake sediments caused by nuclear bomb effect in recent depth profiles. We attributed the sudden increase in diatom species, Cyclotella operculata unipuctata andAchnanthes clevei rostrata, in the uppermost 5-cm layer, to eutrophication of the lake water.We performed a molecular characterization of hydrocarbons isolated from the sediments, and applied computer-assisted high-resolution gas chromatography/mass spectrometry to estimate contributions of biogenic, fossil and pyrolytic hydrocarbons.

In this report we present dating of archaeological samples performed since 1995 in the Radiocarbon Laboratory of the Rudjer Bošković Institute. Several samples from the period before 1995, which were not included in our previous data lists, are given as well. Sample preparation, proportional counter technique, and processing of data are essentially the same as reported earlier (Srdoč et al. 1971, 1979; Obelić 1989). The quality assurance and quality control system according to ISO 17025 has been improved within the IAEA TC Regional Project on Quality Control and Quality Assurance for Nuclear Analytical Techniques. The laboratory participated in 14C intercomparison studies (Horvatinčić et al. 1990; Krajcar Bronić et al. 1995; Bryant et al. 2001; Radiocarbon 2001). We use Oxalic Acid I as modern standard, and anthracite and marble as background standards.

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