Lower Danube River: Characterization of sediments and pollutants

Abstract

Sediment-associated pollutants are transported by rivers as suspended load and bed load under specific flow conditions. In particular conditions part of pollutants (e.g. metals) could be incorporated into the alluvial deposits, and over time, became a major source of the river contamination. The hydrology, the riverbed morphology and the characteristics and quality of river sediments of the Lower Danube have been studied yearly in the 2009 – 2013 period using different methodologies (single and multi-beam bathymetry, ADCP measurements of current velocity and suspended load, sediment sampling using grabs and corers, laboratory analyses). Yearly measurements and sampling have been carried out on more than 70 cross-sections on the Lower Danube course, between km 1072, where the river enters the Romanian territory, and the Black Sea. From each cross-section, one to three sediments samples were analysed for determining the sediment grain size, mineralogy and chemical composition using different laboratory methodologies, as X-ray fluorescence and AAS techniques for Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Ti, V and Zn. The obtained multiannual data allowed identifying the main anthropogenic pollution by heavy metals zones along the river. The Romanian tributaries of the Danube have been sampled and analysed separately for evaluating their role in the general environmental state of the region. The influence of the Danube River water, sediment and pollutants supply to the NW Black Sea has been also studied.