Trace elements in lake sediments of the Brda river catchment area / Pierwiastki śladowe w osadach jezior zlewni Brdy

Total of 54 samples (of sediments taken from the surface of 5-cm layer of profundal zone of lakes in the catchment of the river Brda) were tested in presented research. The collected samples were analysed for the concentrations of Ag, As, Ba, Cd, Co, Cr, Cu, Ni, Pb, Sn, Sr, V and Zn, and Al, Ca, Fe, Mg, Mn, P and S, using inductively coupled plasma atomic emission spectroscopy (ICP-AES), after sample digestion in aqua regia. The Hg concentration was determined from solid samples using atomic absorption spectroscopy (TMA). The organic carbon content was determined using the coulometric method. Sediments of most of lakes examined in the Brda catchment area are characterised by low concentrations of trace elements. Sediments contained an average of 0.9 mg/kg of Cd, 0.107 mg/kg of Hg, 8 mg/kg of Ni, 46 mg/kg of Pb, 8 mg/kg of As, 78 mg/kg of Ba, 12 mg/kg of Cr, 94 mg/kg of Zn, 3 mg/kg of Co, 12 mg/kg of Cu, 1.3 mg/kg of Mo, 105 mg/kg of Sr and 16 mg/kg of V. The presence of elevated concentrations of chromium, copper, nickel and vanadium is controlled by a geogenic factor - weathering of glacial deposits containing fragments of igneous and metamorphic rocks which are the source of heavy metals. The presence of elevated contents of Pb, Zn, Hg and Cd is caused by anthropogenic factor. Most of the lake sediments show low concentrations of As, Cd, Cr, Cu, Hg and Ni, which do not pose a threat to aquatic organisms. The concentrations of lead in almost half of the samples are elevated to a level at which a negative effect of this element can be observed. In the case of zinc, the proportion of such samples is about 25%.