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

Abstract

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 per thousand for delta(18)O and-73.7 to-67.1 per thousand for delta(2)H) and in its tributaries (-9.1 to-8.5 per thousand for delta(18)O and-69.4 to-59.4 per thousand for delta(2)H) 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 delta(13)C(POC) (from-28.9 to-27.4 per thousand) was associated with relatively high C/N ratios (C/N>9), and together with delta(15)N(TPN) 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.

Analysis of isotopic signals in the Danube River water at Tulln, Austria, based on daily grab samples in 2012

“…There are several stable isotopes studies of different parts of the Danube River, a few also of the Upper Danube River, which deal with different partial aspects of the Danube River system [3,[10][11][12][13][14][15][16][17]. This study is based on daily grab sampling through the entire year 2012, which allows a detailed analysis of the seasonal, temperature-and weather-governed progress of stable isotope ratios in river water.…”