Dušan Golobočanin

Distribution of stable isotopes in surface water along the Danube River in Serbia

Stable hydrogen and oxygen isotopes were analysed in water samples from the River Danube and its tributaries during a longitudinal survey performed in August 2005 on Serbian territory. Danube river water data ranged from−80‰ to−66‰ for δ2H, and from−11.2‰ to−9.3‰ for δ18O with δ values increasing downstream. The isotopic signatures of the adjacent tributaries (the Tisza, the Sava and the Velika Morava) sampled at the locations close to their confluence with the Danube (Titel, Ostružnica and Ljubičevski most, respectively) just about the time of the campaign were enriched (−67‰ and−63‰ for δ2H, and−9.3‰ and−8.9‰ for δ18O) with respect to the Danube water because of their catchment effects. Hydrogen and oxygen stable isotope values were used in combination with measured physico-chemical and biological parameters to trace hydrological and transport processes in these river systems. The mixing relationships between the Danube main stream and its tributaries were estimated using the mass balance for isotopic composition and electrical conductivity as conservative parameters. Evidence of an incomplete mixing process at the Čenta location, 8 km below the confluence of the Tisza river, with its participation of 88% was shown by its oxygen-18 content. The correlations between river water isotope composition and physico-chemical and biological parameters are discussed. † Revised version of a paper presented at the 9th. Symposium of the European Society for Isotope Research (ESIR), 23 to 28 June 2007, Cluj-Napoca, Romania.

Potential use of environmental isotopes in pollutant migration studies.

Potential Use of Environmental Isotopes in Pollutant Migration Studies This article presents the use of natural abundance stable isotope (hydrogen, carbon, nitrogen, oxygen, chlorine) analysis data as a tool for providing important information about the origin of contaminants, the contribution of different sources to a multi-source plume, characterisation of their complex transport (rate and mechanisms) and for evaluating the success of contaminated site remediation. Isotopic signatures of contaminants are useful tracers of their sources, while isotopic fractionation can be used to quantitatively assess the progress of an environmental process such as biodegradation. This new isotopic approach is reliable and can offer more information than traditional techniques in pollutant migration studies, particularly after waste disposal. During biological degradation of any organic compound, molecules containing lighter isotopes are degraded, and the portion of heavier isotopes in the substrate is increased, identifying specific microbial roles in biogeochemical cycling. Since isotopic fractionation is proportional to degradation, depending on the type of contamination, a microbial degradation of 50% to 99% of the initial concentration can be quantified using isotope ratio measurements. Potencijalna Upotreba Izotopa Važnih za Okoliš u Ispitivanju Migracije Onečišćujućih Tvari Cilj ovog rada je da se prikaže korištenje podataka analize prirodne obilnosti stabilnih izotopa (vodika, ugljika, dušika, kisika i klora) kao alata za dobivanje važnih informacija o porijeklu onečišćujućih tvari, doprinosu različitih multikomponentnih onečišćivača, karakterizaciji njihova kompleksnog transporta (brzine i mehanizma) i praćenja uspjeha remedijacije onečišćenih mjesta. Izotopski sadržaji onečišćujućih tvari koriste se kao traseri za određivanje njihovih izvora, dok se izotopsko frakcioniranje može iskoristiti za kvantitativnu procjenu toka procesa kao što je biodegradacija. Takav nov izotopski pristup je pouzdan i nudi više informacija od tradicionalnih tehnika kontrole putovanja onečišćivala, napose nakon odlaganja opasnog otpada na zemljištu. Za vrijeme biodegradacije nekog organskog spoje molekule koje sadržavaju lake izotope lakše se degradiraju, a dio težih izotopa u supstratu se povećava, što upućuje na mikrobiološku ulogu u biokemijskom ciklusu. Kako je izotopsko frakcioniranje proporcionalno degradaciji zavisno od tipa onečišćenja, korištenjem podataka mjerenja izotopskih odnosa može se procijeniti mikrobiološka degradacija od 50 % do 99 % od početne koncentracije.

Environmental tritium of the Danube basin in Yugoslavia

An overview of environmental distribution of tritium in the Danube basin in Yugoslavia during the period 1976-1990 is presented. Temporal and regional variations of environmental tritium in the Danube along its flow (1425-847 km from the confluence) and its tributaries (the Sava, the Tisa, the Velika Morava and the Timok) at various locations, as well as in alluvial groundwaters, are given. In Belgrade, monthly values of tritium in rainfall ranged from 1.1 to 18.3 Bq litre(-1), with a maximum in the late spring and early summer months. The half-life for decline in concentration was estimated as 8.3+/-1.0 years. The total amount of tritium deposited in the first 6 months during 1976-90 was 35% larger than in the second 6 months for the same period. Seasonal variations were noticeable in rivers and groundwaters, but these were greatly attenuated and smoothed for the latter. Tritium content in the monthly composite samples from the river in the Belgrade region varied between 2.5 and 18.2 Bq litre(-1) for the Danube and from 1.5 to 16.8 Bq litre(-1) for the Sava. The yearly mean values along the Danube and its tributaries ranged from 2.4 to 15.9 Bq litre(-1) with individual measurements 1.0-30.2 Bq litre(-1). The half-lives were between 6.9+/-1.7 for the Velika Morava and 9.4+/-0.9 for the Danube. Groundwaters, particularly ones in the Ranney wells, followed changes of tritium content in the rivers with a time lag from a few days to a month. During the period of observation, tritium content decreased in alluvial waters with half-lives from 9.9+/-1.6 (Belgrade area) to 7.3+/-1.8 (the Velika Morava).

Isotopic characteristics of meteoric waters in the Belgrade region.

Abstract The stable isotope composition of hydrogen (δ2H) and oxygen (δ18O) in monthly precipitation and river water (Sava River and Danube) samples in the Belgrade area gathered between 1992 and 2005 are determined. The local meteoric water line δ2H=7.8 (±0.2) δ18O+7.3(±1.6) (r 2=0.98, n=60, σ=0.52) for the whole period of observation is close to the global meteoric water line. The amount-weighted mean δ2H and δ18O values of precipitation were−65±27 ‰ and−9.4±3.4 ‰, respectively. Good correlation between δ18O values (r>rsim0.67) and ambient temperature and relative humidity was obtained. Stream-water data ranged from−94 to−60 ‰ for δ2H and from−11.0 to ∼5.7 ‰ for δ18O with highly statistically significant difference (p>0.01) between the Sava River and the Danube. In addition, the isotopic compositions of local precipitation and adjacent river water at monitoring sites were compared. Obtained data will give an opportunity to improve the knowledge of mixing stream water and local groundwater, and assessment of potential groundwater risks and pressures in the Belgrade basin.

Evaluation of the origin of nitrate influencing the Ključ groundwater source, Serbia.

This paper describes the use of the dual isotope method involving δ(15)N and δ(18)O measurements of dissolved nitrates to assess the origin and fate of groundwater nitrate at the Ključ groundwater source, Serbia. A sampling campaign was conducted in September 2007 during flow conditions obtaining groundwater from observation wells and river water fed by a shallow aquifer hosted in alluvial (sandy-gravel) sediments. Nitrate isotope ratios ranged from +5.3 to +16.9‰ and δ(18)O(NO(3)) values varied from -2.3 to +5.0‰. Two major contamination sources were identified with isotopic compositions characteristic for nitrate derived from nitrification of soil organic nitrogen (+5.3 to +7.8‰ for δ(15)N) resulting in nitrate concentrations of 33.6 and 78.8 mg/L and nitrate derived from animal wastes or human sewage, e.g. via septic systems, yielding δ(15)N values of +9.9 to +11.9‰ and elevated nitrate concentrations of 31.2-245.8 mg/L. The occurrence of nitrification and denitrification was also revealed based on concentration and isotope data for dissolved nitrate.

Spatial and temporal variability of stable isotopes and biological parameters for the Danube River in Serbia

This paper presents the results of hydrological, physicochemical, biological, and isotopic investigations of the Danube River along the stretch through Serbian territory conducted during four campaigns in September and November 2007, September 2008 and April 2009. The stable isotope values exhibited significant changes both in the Danube (−10.7 to−9.5‰ for δ18O and−73.7 to−67.1 ‰ for δ2H) and in its tributaries (−9.1 to−8.5‰ for δ18O and−69.4 to−59.4‰ for δ2H) depending on the time of survey, which could be partly attributed to the influences of seasonal effects. Results emphasise the dominant role of tributaries inflows from aquifers along the Danube. The very narrow range of δ13CPOC (from−28.9 to−27.4 ‰) was associated with relatively high C/N ratios (C/N>9), and together with δ15NTPN values, the date suggested that, in early spring, a major fraction of particulate organic matter was derived from allochthonous matter. An orthogonal varimax rotation of the principal components analysis identified four latent factors (‘mineral related’, ‘biological’, ‘hardness’, and ‘soil inlets’) which are responsible for the data structure covering 79% of the observed variations among the variables studied. A reliable grouping of samples with respect to the season was found.

Seasonal and Annual Tritium Variations in Belgrade Natural Waters

Characteristics of seasonal and annual variations of tritium concentration completed with hydrological long-term data from 1976–1989 for the Belgrade alluvial aquifer are presented. The highest tritium concentration in precipitation of an average year appears at the beginning of summer with a maximum in June (9 Bq/l) when the amount of precipitation is also high (102 l/m2). The quantity of tritium precipitating in this area was also the largest in the summer, especially in June (922 Bq/M2). Similar variations of tritium concentration was found in the waters of the Danube and the Sava with maxima 11.3 Bq/l (July) and 9 Bq/l (June) respectively. Tritium concentrations orginated from snowmelt influence to the occurrence of higher values during that period which is more distinct in the Sava. The groundwaters and particularly ones in the Ranney wells follow changes of levels, temperature and tritium content in the alluvial of Sava with a time lag from a few days to a month. During the period of observation tri...

Evaluation of the origin of sulphate at the groundwater source Ključ, Serbia

The dual-isotope method of measuring both the δ34S and δ18O values of dissolved sulphate to assess the origin and fate of groundwater sulphate at the Ključ groundwater source, Serbia is applied. A sampling campaign was conducted in September 2007 during low-flow conditions, obtaining river water and groundwater from observation wells completed in a shallow aquifer formed in alluvial sandy–gravelly sediments. In the shallow groundwater, sulphate concentrations ranged from 56.2 to 165.0 mg l−1. The δ34S values of sulphate varied from−5.5 to+3.0 ‰ and values from+1.4 to+4.2 ‰. Oxidation of pedospheric (organic soil S) and lithogenic sulphur sources (e.g. pyrite) were identified as the main causes for the increasing sulphate concentrations in the analysed groundwater. This study shows that combining hydrological, chemical, and isotopic techniques is a powerful approach to identifying sources and processes that control sulphate in water resources.