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The paper is based on grain size analyses as well as on the macroscopic lithologic description of a large number of samples collected from the bottom of the Danube. Unlike previous papers on sedimentology, which were limited to the textural characterisation of sediments from the various sectors of the Danube, this paper attempts a new approach of the sediment dynamics. The interpretation of histograms, of cumulative curves or of the Passega diagram is used in the attempt to explain the dynamic and genetic reasons for the presence of a particular type of sediment in locations characterised by different environmental energy conditions. [ABSTRACT FROM AUTHOR]

Understanding the natural evolution of a river–delta–sea system is important to develop a strong scientific basis for efficient integrated management plans. The distribution of sediment fluxes is linked with the natural connection between sediment source areas situated in uplifting mountain chains and deposition in plains, deltas and, ultimately, in the capturing oceans and seas. The Danube River–western Black Sea is one of the most active European systems in terms of sediment re-distribution that poses significant societal challenges. We aim to derive the tectonic and sedimentological background of human-induced changes in this system and discuss their interplay. This is obtained by analysing the tectonic and associated vertical movements, the evolution of relevant basins and the key events affecting sediment routing and deposition. The analysis of the main source and sink areas is focused in particular on the Miocene evolution of the Carpatho-Balkanides, Dinarides and their sedimentary basins including the western Black Sea. The vertical movements of mountains chains created the main moments of basin connectivity observed in the Danube system. Their timing and effects are observed in sediments deposited in the vicinity of gateways, such as the transition between the Pannonian/Transylvanian and Dacian basins and between the Dacian Basin and western Black Sea. The results demonstrate the importance of understanding threshold conditions driving rapid basins connectivity changes superposed over the longer time scale of tectonic-induced vertical movements associated with background erosion and sedimentation. The spatial and temporal scale of such processes is contrastingly different and challenging. The long-term patterns interact with recent or anthropogenic induced modifications in the natural system and may result in rapid changes at threshold conditions that can be quantified and predicted. Their understanding is critical because of frequent occurrence during orogenic evolution, as commonly observed in the Mediterranean area and discussed elsewhere. [ABSTRACT FROM AUTHOR]

Abstract: This paper provides the first critical synopsis of contamination by selected trace elements in the whole Danube Delta (Romania/Ukraine) to: identify general patterns of contamination by trace elements across the Delta, provide recommendations to refine existing monitoring networks and discuss the potential toxicity of trace elements in the whole Delta. Sediment samples were collected between 2004 and 2007 in the three main branches of the Delta (Chilia, Sulina and Sfantu Gheorghe) and in the secondary delta of the Chilia branch. Samples were analyzed for trace elements (Cd, Co, Cr, Cu, Ni, Pb, V, and Zn) and TiO2, Fe2O3, MnO, CaCO3 and total organic carbon. Cluster analysis (CA) and Principal Component Analysis (PCA) showed that levels of Cd, Cu, Pb, and Zn were influenced by anthropogenic activities. At the opposite, concentrations of Cr and Ni largely originated from the weathering of rocks located in the Romanian part of the Danube catchment and naturally rich in these elements. Data analysis using Self-Organizing Maps confirmed the conclusions of CA/PCA and further detected that the contamination tended to be higher in the Chilia and Sulina arms than in the Sfantu Gheorghe arm. The potential ecological risks due to trace element contamination in the Danube Delta could be identified as moderate and localized, provided that the presence of the natural sources of Cr and Ni was properly considered. The available results suggest that monitoring sediment quality at the mouths of Sulina and Sfantu Gheorghe arms is probably enough to get a picture of the sediment quality along their entire lengths. However, a larger network of monitoring points is necessary in the Chilia and secondary Chilia delta to account for the presence of local point sources and for the more complex hydrodynamic of this part of the Danube Delta. [Copyright &y& Elsevier]

Summary: In this work, an interferometric ALOS PalSAR dataset acquired between 2007 and 2010 is used to measure water level changes for the first time within a hydrographical unit of the Danube Delta in Romania at the Black Sea. When the Differential Synthetic Aperture Radar Interferometry (DInSAR) technique was applied, it revealed a previously unknown and spectacular dynamic of the water levels in Danube Delta. The results are presented in the form of water level change maps for different periods of time. The DInSAR measurements for a number of locations are compared with extrapolated water level change values obtained from an existing mathematical model of the hydrological regime in the Danube Delta. The comparison shows a very good correlation between DInSAR measurements and the mathematical model, showing that this method using L-band ALOS PalSAR data and applied to a wetland area of Danube Delta can be used to increase the spatial density of water level measurements and contributes to a better understanding of hydrological processes. [ABSTRACT FROM AUTHOR]