Trace element study in Tisa River and Danube alluvial sediment in Serbia

Abstract

The contaminated sediment serves as a long-term source of toxic elements, since that mobility and transport in the environment of these elements are strongly influenced to associated solid phase. In this study, the modified Tessier sequential extraction procedure was applied for the fractionation of Cd, As, Hg, Cu, Zn, Cr, Pb, Ni and V in the sediments (Tisa River and canal sediments - Danube alluvial formation), to obtain an overall classification of trace element pollution in these areas through its spatial distribution. Investigations of this region are important due to the widespread occurrence of metal mining activities throughout the Tisa and Danube drainage basins and possibilities of contamination with toxic elements at studies localities. Five steps of the sequential extraction procedure partitioned elements into CH3COONH4 extractable (F1), NH2OH center dot HC carbonate extractable and easily reducible (F2), H2C2O4/(NH4)2C2O4 moderately reducible (F3), H2O2-HNO3 organic extractable (F4), and HCl acid soluble residue (F5). Analyses of the extracts were performed by flame atomic absorption spectrometry. To indicate the degree of risk of toxic elements, risk assessment code and contamination factor have been used. The results of partitioning study indicate that more easily mobilized forms (metals in adsorbed/exchangeable/carbonate forms or bound to amorphous Fe and Mn oxyhydroxides and Fe and Mn oxides) were predominant for copper, zinc, cadmium and lead, which can be used as indicators for input from anthropogenic source. In contrast, the largest amount of chromium and nickel were associated with the inert fraction, which reduced their solubility and rendered them immobile under natural conditions and indicative of natural origins. Most of remaining portion of metals was bound to ferromanganese oxides fraction. It is concluded that sequential extraction results proved useful to distinguish between anthropogenic and geochemical sources of elements in the sediments.