ASSESSMENT OF RIVER SEDIMENT QUALITY ACCORDING TO THE EU WATER FRAMEWORK DIRECTIVE IN LARGE RIVER FLUVIAL CONDITIONS. A CASE STUDY IN THE LOWER DANUBE RIVER BASIN
Authors:   Geological Institute of the Bulgarian Academy of Sciences, Acad. Georgi Boncev St., bl. 24, 1113 Sofia, Bulgaria, HIKOV Atanas , VÎJDEA Anca-Marina ,   Geological Institute of Romania IGR, 1 Caransebeș St., RO-012171 Bucharest, Romania, PEYTCHEVA Irena ,   Geological Institute of the Bulgarian Academy of Sciences, Acad. Georgi Boncev St., bl. 24, 1113 Sofia, Bulgaria, JORDAN Gyozo ,   Eötvös Loránd University, Egyetem tér 1-3, H-1053, Budapest, Hungary, MARJANOVIĆ Prvoslav ,   Jaroslav Černi Water Institute, Jaroslava Cernog 80, 11226, Belgrade, Republic of Serbia, MILAKOVSKA Zlatka ,   Geological Institute of the Bulgarian Academy of Sciences, Acad. Georgi Boncev St., bl. 24, 1113 Sofia, Bulgaria, FILIPOV Petyo ,   Geological Institute of the Bulgarian Academy of Sciences, Acad. Georgi Boncev St., bl. 24, 1113 Sofia, Bulgaria, VETSEVA Milena ,   Geological Institute of the Bulgarian Academy of Sciences, Acad. Georgi Boncev St., bl. 24, 1113 Sofia, Bulgaria, BALTRES Albert ,   Geological Institute of Romania IGR, 1 Caransebeș St., RO-012171 Bucharest, Romania, ALEXE Veronica Elena ,   Geological Institute of Romania IGR, 1 Caransebeș St., RO-012171 Bucharest, Romania, BĂLAN Lidia-Lenuța ,   Geological Institute of Romania IGR, 1 Caransebeș St., RO-012171 Bucharest, Romania, MARJANOVIĆ Marko ,   Jaroslav Černi Water Institute, Jaroslava Cernog 80, 11226, Belgrade, Republic of Serbia, CVETKOVIĆ Vladica ,   University of Belgrade, Faculty of Mining and Geology, Djusina 7, 11000 Belgrade, Republic of Serbia, SARIĆ Kristina ,   University of Belgrade, Faculty of Mining and Geology, Djusina 7, 11000 Belgrade, Republic of Serbia
Published: February 2023

Increase of pollution of surface water and water sediments with hazardous substances (HSs) in the Danube River Basin requires implementation of systematic monitoring and evaluation of the sediment quality. The present study is focused on the ’South Danube’ Test Area (SDTA) that covers parts of the Lower Danube Basin in Romania, Serbia and Bulgaria. The SD area represents an extended region where Danube reaches its largest widths and depths and where pollution (industrial, mining, agricultural, waste etc.) from tributaries and land is supposed to accumulate in the sediments. Sampling of river bottom sediment (BS), suspended sediment (SS) and overbank (floodplain) sediment at two layers (0-5 cm in the top layer (FS TS) and 40-50 cm in the bottom layer (FS BS)), was carried out at 11 locations in order to analyze the concentration and distribution of 8 metal(oid)s (Cu, Pb, Zn, Cd, Hg, Ni, Cr, As), 6 polycyclic aromatic hydrocarbons (PAHs) and 6 pesticides as hazardous substances. The 2013/39/EU Directive and EU Water Framework Directive standards were used to sediment quality assessment. As a whole, the concentrations of heavy metals in the sediments are comparatively low and are around the normal values for soils. On the other hand, some sampling sites and sediment types have high or very high metal concentrations which exceed intervention levels. Our study well recognizes mining pollution sources in the Danube tributaries Borska Reka, Timok, Ogosta, Malak Iskar and Iskar from past and/or recent mining activity. This pollution is limited to the Danube tributaries and around their confluences into the Danube River. The concentration of heavy metals is strongly diluted in the Danube River and drops around normal values. The studied sediments reveal low concentrations of PAHs. Only fluoranthene content is higher in most of the sediment types and sampling sites on the Danube River, but exceeds the interventional level only at Pristol and at Hârșova. Our results show that the sediments in the Danube River are more polluted with PAHs than its tributaries. The identified organic compounds are assumed to be generated during incomplete or low temperature combustion processes or during road transportation and/or the navigation on the Danube River.