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

Abstract

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 parts per thousand to -66 parts per thousand for delta(2)H, and from -11.2 parts per thousand to -9.3 parts per thousand for delta(18)O with delta 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, Ostruznica and Ljubicevski most, respectively) just about the time of the campaign were enriched (-67 parts per thousand and -63 parts per thousand for delta(2)H, and -9.3 parts per thousand and -8.9 parts per thousand for delta(18)O) 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 Centa 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.