The impact of the Danube Iron Gate Dam on heavy metal storage and sediment flux within the reservoir

Construction of the Danube Iron Gate Dam for hydroelectricity, 943 km from the mouth of the Danube River, is changing sediment transport due to its retention in the Iron Gate Reservoir (IGR), potentially causing heavy metal enrichment, re-distribution within the solid phase, exchange or re-suspension on sediment–water interface. The concentrations of heavy metals (Cu, Zn, Pb and Cd) in water and sediment during a five-year period along the IGR were determined. The fluxes of heavy metals from river water to sediment due to sedimentation were determined, as well as their fluxes from the bottom sediment to the sediment–water interface due to sediment re-suspension at high flow rate, when fluvial erosion takes place and removes part of the previously deposited sediment from the river bed, in a yearly amount between 2 and 9%, depending on the hydraulic regime in the IGR.