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[en] Owing to its geographical location, the Black Sea has been one of the marine basins most contaminated with artificial radioactivity. During the pre-Chernobyl period, the main source of radioactive contamination of the Black Sea was the global fallout from the atmospheric nuclear weapon tests, which peaked in 1962 before the 1963 Test Ban Treaty was signed between the main nuclear states. As maximum global fallout was observed within the 40-50oN latitude band that runs exactly across the Black Sea, this semi enclosed water body received high levels of the fallout radionuclides derived from the atmospheric weapons testing. Being a closest marine body to the Chernobyl site, the Black Sea and its broad drainage areas have received substantial amounts of the long-lived artificial radionuclides, particularly 90Sr, 137Cs, and plutonium isotopes, released into the atmosphere from the damaged nuclear reactor and delivered with the air masses moving south- and westward from the accident area. Besides direct atmospheric deposition, the Black Sea received (and continues to receive) additional radioactive input by river runoff, particularly to its northwestern area from the Danube and Dnieper Rivers. Resulting from contribution of the above-mentioned sources of radioactive contamination of the Black Sea, the 90Sr concentration in its water ranks second after the Irish Sea, and third after the Baltic Sea with respect to 137Cs concentration in seawater. Overview of results. Extensive radioecological studies performed during the last decades have showed that post-Chernobyl evolution and levels of man-made radioactivity in the Black Sea were governed, except radioactive decay, by the large-scale oceanographic, biogeochemical and ecological processes, which control the self-cleaning of the Black Sea environments against the radioactive contamination: first of all the vertical water mixing, which dilutes the surface radionuclide concentrations, the loss through the Bosporus Strait connecting the Black Sea with the Mediterranean, and sedimentary scavenging of sorption reactive radionuclides on sinking particles. Because of effects of these factors the initial inventory of Chernobyl-derived radionuclides has decreased abruptly, reaching currently the pre-accident level, except estuarine zones particularly of the Danube and Dnieper Rivers account for 75 % of the total river runoff to the Black Sea and 95 % of the runoff entering the NW Black Sea. In turn, study of the post- Chernobyl dynamics of radionuclide concentration in different compartments of the Black Sea ecosystem gave a unique opportunity to evaluate a number of hydrological, geochemical, and ecological processes and to trace their long-term changes, achieving eventually an integrated assessment of potential capability of the Black Sea for self-purification against both nuclear and non-nuclear pollutants
[en] Deuterium excess is defined as d-excess=δ2H-8*δ18O where δ2H and δ18O are the isotopic compositions of a water molecules. It has shown potential in climatic studies for tracing past and present precipitation processes. It is also a measure of the relative proportions of δ2H and δ18O in water and can be visually depicted as an index of the deviation from the global meteoritic water line (GMWL) in the 2D space defined by the coordinates δ2H and δ18O. The characteristic geographic diversity influences the climate in Slovenia considerably. Consequently, there is a mixture of continental, Alpine, and sub-Mediterranean climate which is reflected also in the isotopic composition of precipitation and other components of the hydrological cycle (i.e. surface water, vadose zone water, and groundwater) in the area. Therefore, the main purposes of this study are: - to collect all available hydrogen and oxygen stable isotopic data of various components of hydrological cycle in Slovenia and it's near surrounding, and - to analyse the ranges and statistical distributional characteristics with particular emphasis on the d-excess values.
[en] The aims of this study were mainly: (i) the identification and differentiation of the main anthropogenic nitrogen sources in the Marano Lagoon (Italy) and its catchment area; and (ii) the assessment of the intra-lagoonal water circulation, the morphological development of the lagoon and its anthropogenic pressure by applying a combined approach of hydrochemical, isotopic and remote sensing techniques. To achieve the aforementioned targets analyses of stable isotope signatures of nitrate, boron, water and sulphate have been used. Moreover the residence times of groundwater were determined by the tritium-helium dating method. To characterize the chemical composition of the different water types the concentrations of the major ions and nutrients as well as the physicochemical parameters have been measured. Remote sensing techniques have been applied to assess the spatial distribution of most superficial algal flora, water temperature as well as the key environmental and morphological changes of the lagoon since the beginning of the 1970s.
[en] A stable isotope analyst has to make a number of important decisions regarding how to best determine the 'true' stable isotope composition of analysed samples in reference to an international scale. It has to be decided which reference materials should be used, the number of reference materials and how many repetitions of each standard is most appropriate for a desired level of precision, and what normalization procedure should be selected. In this paper we summarise what is known about propagation of uncertainties associated with normalization procedures and propagation of uncertainties associated with reference materials used as anchors for the determination of 'true' values for δ''1''3C and δ''1''8O. Normalization methods Several normalization methods transforming the 'raw' value obtained from mass spectrometers to one of the internationally recognized scales has been developed. However, as summarised by Paul et al. different normalization transforms alone may lead to inconsistencies between laboratories. The most common normalization procedures are: single-point anchoring (versus working gas and certified reference standard), modified single-point normalization, linear shift between the measured and the true isotopic composition of two certified reference standards, two-point and multipoint linear normalization methods. The accuracy of these various normalization methods has been compared by using analytical laboratory data by Paul et al., with the single-point and normalization versus tank calibrations resulting in the largest normalization errors, and that also exceed the analytical uncertainty recommended for δ13C. The normalization error depends greatly on the relative differences between the stable isotope composition of the reference material and the sample. On the other hand, the normalization methods using two or more certified reference standards produces a smaller normalization error, if the reference materials are bracketing the whole range of isotopic composition of unknown samples. These conclusions are in agreement with the approach proposed by Coplen et al. for the stable carbon isotope referencing. These studies strongly support the use of two-point or multi-point normalisation methods based on regression line as producing the most reliable results Paul et al.