Heavy metal concentrations in the sediment profiles of the anthropogenically transformed plociduga reservoir

The aim of the present study was to determine the level of contamination of the bottom deposits in the former lake Plociduga in Olsztyn by selected heavy metals (Zn, Pb, Cr, Cd). Today Plociduga is a transformed wetland ecosystem, surrounded by urbanized areas (residential housing, industrial development). The main point sources of pollution are the outlets of two storm water drains. The study was conducted in 2009. Samples of bottom deposit cores were collected in two separate parts (northern and southern) of the former lake. The study revealed very high concentrations of lead, zinc and chromium in the uppermost layer of the sediments in the part of the ecosystem fed by rainwater. The concentrations of the analyzed elements were substantially lower in deeper sediment layers and in the samples collected in the southern part of the ecosystem, not exposed to the direct pollutant inflow. The accumulation of heavy metals in the surface layers of bottom deposits is indicative of the poor ecological condition of the investigated ecosystem and increased human pressure resulting from progressive urbanization.