Distribution of heavy metals in bottom sediments of floodplain lakes and their parent river – a case study of the Slupia

Concentration of trace elements in bottom sediments can be a result of natural accumulation or caused by anthropogenic factors. The content of heavy metals (Cd, Cr, Cu, Ni, Mn, Pb and Zn) in bottom sediments of oxbow lakes and river-bed of the Słupia River at Słupsk was determined. Sediment samples were taken from two oxbow lakes: naturally disconnected and artificially re-connected with the river. The research showed variation in the content of the elements in sediments in relation to the accumulative and erosive activity of the river. At the water inflow into the re-connected oxbow lake, the transporting strength of the river decreased, which favoured the accumulation of heavy metals. The content of heavy metals in bottom sediments taken from the re-connected floodplain lake at the outlet was several-fold lower than at the inlet, for example there was 11-fold less Mn, 9-fold less Cu 9-fold, 3-fold less As and half the amount of Cd, Cr and Ni. The content of heavy metals at the outlet was similar to the one found in sediments of the oxbow lake separated from the river.