Wyszogrod Island (Vistula River, Poland) sediments: hydrological explanation of heavy metal concentrations

Abstract

Alluvial sediment transport in rivers is considered as one of the most dynamical natural processes. The sediments in the fluvial system can be temporarily stored at the surface of floodplain channel bars and islands. The middle reach of the Vistula River has preserved its natural braided channel pattern with the large islands, but the water is also heavily contaminated. Wyszogrod Island is more than 100 years old, and the sequence of its sediments can be used for dating the regional environment contamination history. The development of the island has been studied using old topographic maps, which have been calibrated by a CAD-Raster program using affinite transformation. The sediment samples have been collected in three specified profiles, and an analytical procedure of sequential chemical extractions for the partitioning of trace elements Fe, Mn, Cr, Cu, Pb, Zn, and Ni in different grain sizes has been carried out. High concentration of heavy metals compared to the island's concentration background values could be found in active sediment traps, where practically every year floods deposit some material. The top layer sediments of the structurally older parts of the Island, which are overflooded only by major high flood events, are also contaminated. Perceptible declines of the heavy metal concentrations in the youngest top layer sediments confirm improvement of the Vistula River environment in the last years. Combined investigations of historical cartographic materials together with the available hydrological data analysis provide adequate results in structuring younger sediment depositions in the floodplain area near Wyszogrod. This can help to optimize future field sampling campaigns and the interpretation of the complex mosaic structure of trace element concentrations in younger Vistula River island sediments.