Uranium isotopes as a possible tracer of terrestrial authigenic carbonate.

The concentration and isotopic composition of uranium (δ238U, 234U/238U activity ratio) in combination with traditional isotopes (δ18O, δ13C) were examined as potential tracers of authigenic carbonate formation in a karst aquifer. The U concentration and 234U/238U activity ratios in the tufa-precipitating sections of two connected karst rivers (Krka and Zrmanja, Croatia) decreased downstream in water and in precipitated carbonate due to active self-purification processes, i.e. adsorption of isotopically lighter U(VI) on mineral particles, sedimentation and co-precipitation with carbonate. The isotopic composition of carbonate in tufa mostly resembled the 234U/238U activity ratio and the δ238U values of dissolved U in water but was also affected by the presence of detrital carbonate flushed into the river from soil and weathered bedrock. This interpretation was supported by the δ18O and δ13C values of tufa, which were shifted out of equilibrium with river water and dissolved in organic carbon and in their isotopic signature, which showed the presence of lithic carbonate. Large fluctuations of the δ238U values of water, leachable U (eluted in acetic acid buffered with Na-acetate) and residual U fraction could not be fully explained by available data due to the overlapping U isotopic signatures of leachable (mainly carbonate) and residual fractions of soil, bedrock and tufa. Therefore, a long-term, systematic, seasonal and event-based observation of the isotopic composition of dissolved and suspended particulate U in water is necessary. Nevertheless, the U isotopes were found to have the potential to be used as identifiers of authigenic carbonate and the storage of CO2 in terrestrial river sediments, to improve knowledge on fluxes within local and global biogeochemical carbon cycle.

Geostatistical evaluation of the design of the precipitation stable isotope monitoring network for Slovenia and Hungary.

A detailed knowledge of the stable isotope signature of precipitation is the basis of investigations in a variety of scientific fields and applications. To obtain robust and reliable results, the representativity of the currently operating (at least, as of 2018) precipitation stable isotope monitoring stations across Slovenia (n = 8) and Hungary (n = 9) was evaluated on the basis of amount-weighted annual averages with the aim of revealing any redundantly (i.e. over-) represented or un(der)represented areas. In the case of the latter, optimal locations for additional sites were suggested in Slovenia and Hungary. The networks of both countries are design-based systems that need to be fine-tuned for long-term optimized operation. The evaluation of the monitoring network was performed taking into consideration the stations operating in Slovenia and Hungary, as well as closely situated ones operating in neighboring countries. The evaluation was carried out in nine different combinations, using spatial simulated annealing, with regression kriging variance as a quality measure. The results showed that (i) there are over- and un(der)represented areas in the network, an issue requiring remedial action, (ii) the mutual information exchange of the precipitation stable isotope monitoring networks of Slovenia and Hungary increases the precision of precipitation δ18O estimation by ~0.3‰ in a 15-30 km wide zone near the borders, and (iii) by an even greater degree in the neighboring countries' stations. The current research may be termed pioneering in the matter of the detailed geostatistical assessment of spatial representativity of a precipitation stable isotope monitoring network, and as such, can serve as an example for future studies aiming for the spatial optimization of other regional precipitation stable isotope monitoring networks.

Case of Fatal Starvation: Can Stable Isotope Analysis Serve to Support Morphological Diagnosis and Approximate the Length of Starvation?

The diagnosis of death as a result of starvation is established on anthropological measurements, visual appearance of the deceased on external and internal examination, microscopic analysis, laboratory testing, and exclusion of other causes of death. Herein, we present our findings on a case of 95-year-old man who died of starvation. After the diagnosis of starvation was established by traditional forensic medicine methods, we have conducted retrospective segmental analysis of stable carbon (δ13 C) and nitrogen (δ15 N) isotope ratios in hair sample. This method reveals periods of starvation through decrease in δ13 C and increase in δ15 N along the strand of hair. Our analysis revealed the decrease of 0.6 ‰ in δ13 C during the last 10-12 weeks prior to death, similar as reported in other investigations. Also, a decrease of 0.7 ‰ in δ15 N during the last 8-10 weeks prior to death was determined that was different than observed in previous studies.

Historical records of mercury in southern latitudes over 1600 years: Lake Futalaufquen, Northern Patagonia.

Mercury is released to the environment from natural and anthropogenic sources, and through atmospheric transport is distributed globally. Lake Futalaufquen (42.8°S) is an oligotrophic lake located in Los Alerces National Park (Northern Patagonia), providing a remote and unpolluted study system. A lacustrine sedimentary sequence revealed 1600 years of Hg deposition, identifying natural baselines and marked peaks not correlated with long-range atmospheric transport. Organic matter and catchment erosion were discarded as Hg drivers. Natural background, pre-1300 CE Hg concentrations, ranged between 27 and 47 ng g(-1) (accumulation rates from 8 to 15µg m(-2) y(-1)). From 1300 CE on, the Hg background profile did not follow the generally increasing Hg pattern observed in both Southern and Northern Hemisphere since pre-industrial times. It was not until the last century that a 1.6-fold increase is observed in the Hg accumulation rate, considered among the lowest increments in southern South America. Noteworthy local/regional sources of Hg for this area, along with global transport, are forest fires and volcanic activity. Between approx. 1340 and 1510 CE, sharp increase in Hg concentration and accumulation rate (up to 204 ng g(-1) and 51 µg m(-2) y(-1), respectively) were clearly associated with extended fire episodes. Furthermore, high Hg peaks during the last 300 years were associated with volcanic eruptions in northernmost Patagonia together with fairly irregular fire episodes, caused by anthropogenic burning by settling population in the Andes.

Carbon isotopic composition (δ(13)C and (14)C activity) of plant samples in the vicinity of the Slovene nuclear power plant.

δ(13)C values of various plants (apples, wheat, and maize) collected in the vicinity of the Krsko Nuclear Power Plant (Slovenia) during 2008 and 2009 were determined. By measuring dried samples and their carbonized counterparts we showed that no significant isotopic fractionation occurs during the carbonization phase of the sample preparation process in the laboratory. The measured δ(13)C values of the plants were used for δ(13)C correction of their measured (14)C activities.

Atmospheric distribution and deposition of mercury in the Idrija Hg mine region, Slovenia.

The atmospheric distribution and deposition of Hg in the area of the former Idrija Hg-mine, Slovenia, were investigated. Mapping of air Hg(0) concentrations was performed to assess the spatial distribution and major sources of mercury to the atmosphere in the area. In addition, analyses of mercury speciation in the air over Idrija were performed during a 4-day sampling campaign in September 2006 to better understand the fate and transformation of Hg in the atmosphere of this specific mercury polluted site. The speciation results were then compared to the results of mercury speciation in the wet and throughfall deposition sampled on a precipitation event basis from October 2006 to September 2007. The Hg(0) concentration in air was mostly below 10 ng m(-3), with the highest concentration in the area of the former smelter complex exceeding 5000 ng m(-3). Mercury-bearing airborne particles (TPM) seem to dominate the atmospheric Hg deposition, which revealed noticeable variations between precipitation events (11-76 ng m(-2)day(-1)), mostly as a function of the amount of precipitation. Hg in precipitation was largely (∼ 50%) associated with the particulate phase (THg(P)). No correlation was found between the THg(P) and the dissolved phases (THg(D)), suggesting that particulate phase Hg is mostly the result of dry deposition. In the throughfall, significantly higher (2-10 fold) Hg concentrations than in associated event precipitation were observed, mostly due to Hg in the particulate phase (∼ 70% THg). As shown by SEM/EDXS microscopy, an important amount of mercury in the precipitation and throughfall samples is due to the presence of cinnabar particles as a result of the aeolian erosion of cinnabar-containing surfaces in the area.

Recent environmental changes in the shallow Lake Pamvotis (NW Greece): evidence from sedimentary organic matter, hydrocarbons, and stable isotopes.

Lake Pamvotis is a shallow Mediterranean lake located in northwestern Greece that has been recognized as an internationally important conservation site. Here, an unprecedented investigation was undertaken to obtain and evaluate data related to sedimentary organic matter, hydrocarbon content, and stable isotopes of Lake Pamvotis sediments, thus tracking the origin of organic inputs and providing a record of environmental status. The study revealed a distinct spatial distribution of polycyclic aromatic hydrocarbons (PAHs) with values between 34.7 and 1600 microg/kg and a rather uniform pattern for n-alkanes with concentrations falling below 41.4 microg/g. A significant contribution of an unresolved complex mixture indicated anthropogenic petroleum contamination. Further study of relevant indexes and geochemical biomarkers supported a mixed-source input of aliphatic hydrocarbons. With regard to PAHs, there was strong evidence that their dominant origin is pyrogenic. Finally, considerable excursion in delta(13)C(org) was attributed to changes in dissolved inorganic carbon accompanied by increased input of effluents and recycling of organic carbon within the lake, whereas the rise in isotopic composition of nitrogen was associated with agricultural runoff and sewage input from the town of Ioannina.

Comparison of monthly and daily isotopic composition of precipitation in the coastal area of Slovenia.

The stable isotopic composition (delta(2)H and delta(18)O) of short-term (daily) precipitation collected from October 2002 to September 2003 at two stations in a coastal, karstic area in south-western Slovenia was investigated. In addition, monthly composite samples were collected and analysed for comparison with amount-weighted monthly means. The delta(2)H and delta(18)O values obtained show a wide range and reflect seasonal climatic variations. Deuterium excess and local meteoric water lines (LMWLs) were determined and cumulative frequency analysis and coincidence tests were performed. The statistical coincidence test showed that the LMWLs calculated from monthly data for Portoroz and Kozina are coincident, but the LMWLs calculated from daily precipitation events are not. This difference could be explained by the greater variance of the isotopic composition of daily precipitation in comparison to monthly composite samples and also to the influence of evaporation during events below<1 mm at Portoroz during the extremely dry and warm spring-summer season of 2003. Finally, synoptic maps and backward trajectories of a selected precipitation event showed that changes of isotopic composition are related to mixing of air masses originating from the continent and Mediterranean cyclogenesis.

Identification of sources and production processes of bottled waters by stable hydrogen and oxygen isotope ratios.

Bottled water is a food product that considerably depends on the environment from which it originates, not only at the place where it is produced, but predominantly on the conditions in the recharge area of the wells captured for bottling. According to their source and the bottling process, bottled waters can be divided into natural and artificially sparkling waters, still and flavoured waters. These waters originate from various parts of the hydrological cycle and their natural origin is reflected in their hydrogen and oxygen stable isotopic compositions (delta(2)H and delta(18)O). A total of 58 domestic and foreign brands and 16 replicates of bottled waters, randomly collected on the Slovene market in September 2004, were analysed for delta(2)H and delta(18)O. The isotopic composition varied between -83 per thousand and -46 per thousand with an average of -66 per thousand for hydrogen, and between -11.9 per thousand and -7.5 per thousand with an average of -9.6 per thousand for oxygen. This investigation helped (1) to determine and test the classification of bottled waters, (2) to determine the natural origin of bottled water, and (3) to indicate differences between the natural and production processes. The production process may influence the isotopic composition of flavoured waters and artificially sparkling waters. No such modification was observed for still and natural sparkling waters. The methods applied, together with hydrological knowledge, can be used for the authentication of bottled waters for regulatory and consumer control applications.

Stable isotope composition of daily and monthly precipitation in Zagreb.

Stable isotopic compositions (delta2H and delta18O) of daily precipitation collected in the period from October 2002 to March 2003 and monthly precipitation in the period from 2001 to 2003, as well as the corresponding meteorological data (temperature, amount of precipitation), all collected in Zagreb, Croatia, are presented. delta2H and delta18O values, both daily and monthly, show large variations due to large temperature variations and the different origin of the air masses. Variations are larger for daily samples than for composite monthly samples. Good correlation of delta18O with temperature is obtained for both types of samples. On the basis of the correlation between delta2H and delta18O, the local meteoric water line is close to the global meteoric water line. Deuterium excess of both daily and monthly precipitation indicates that in the Zagreb area, the influence of air masses from the Mediterranean area prevails in the autumn period.

Distribution of hydrogen, oxygen and carbon isotopes in the atmosphere of Croatia and Slovenia.

Monitoring of isotope distribution in the atmosphere included isotopes 2H, 3H and 18O in precipitation, and 13C and 14C in atmospheric CO2. This paper presents the results of atmospheric monitoring over Croatia and Slovenia overt the last few years. Monthly precipitations in Zagreb and Ljubljana had been collected since 1976 and 1981, respectively. Between 2000 and 2003 monitoring also included seven stations along the Adriatic coast. Tritium activity in precipitation shows seasonal variations that were most pronounced inland (at the continental stations Zagreb and Ljubljana) and were the smallest in the south Adriatic (Komiza and Dubrovnik). Mean annual tritium activity decreases from the north to the south Adriatic coast. Seasonal variations in delta2H and delta18O in precipitation follow the temperature variations at the sampling stations. Atmospheric CO2 was collected in Zagreb and Plitvice as a composite monthly sample. Both delta14C and delta13C showed seasonal variations. The mean annual 14C activities in Zagreb had been decreasing after the peak reached in the 1960s, and for the last three years the mean 14C activity (delta14C) remained about 30 per thousand.

Geochemical estimation of copper contamination in the healing mud from Makirina Bay, central Adriatic.

The coastal sediment from Makirina Bay in the central Adriatic represents an important source of healing mud (peloid) of high quality organoleptic properties that could in future be used for medical treatment. In this study, we estimated the contamination of the sediment with copper which can cause some undesirable health effects. Concentrations of Cu vary from 12 to 63 mg/kg in surface sediment and are higher in the central part of the Bay where the mud fraction prevails. Different normalizing methods were used, i.e. surface/background ratio, index of geoaccumulation, reference metal normalization, enrichment factor (EF) and grain size normalization, to compensate for the influence of the natural variability in sediment mineralogy and granulometry, and to assess whether the concentrations observed in surface sediment represent background or contaminated levels. Results show that Cu concentrations in the surface sediment are twice as high as local background values but in the same range as many clay materials used for medical treatment in Italy. The results also show that more detailed studies on Cu mobility are necessary prior to actual use of peloid in medical treatment.