Transport of Potentially Toxic Elements in Solid Particulate Matter during Flash Flood Events in Upper and Lower Stretch of the Sava River

During extreme hydrological conditions such as flood events, sediments and alluvial soils may become re-suspended. As a consequence, the concentration of solid particulate matter (SPM) in the water column increases. As sediments represent a sink for the contaminants, when such perturbation occurs, the toxic substances may be re-dissolved into the water, causing harmful effects to the freshwater habitat. The purpose of this study was to evaluate the release of potentially toxic elements associated to SPM during flash floods. Two sampling sites on the Sava River were chosen: Litija (Slovenia), where the river has still the characteristics of an alpine river, and in Belgrade (Serbia), where Sava is a lowland river with a flat riverbed, slower flow and bigger quantities of fine-grained sediment. The results of the study showed a good correlation between the SPM mass concentration and water level/discharge. At both sampling sites, elevated concentrations of As, Cd, Cr, Cu, Pb, Ni and Zn were determined in SPM, indicating a moderate level of contamination at Litija and a high level at Belgrade. The results demonstrated that during the two investigated flash flood events limited the dissolution of PTE from SPM-bearing particles.