Variations in the Chemical Composition of Bottom Deposits in Anthropogenic Lakes

摘要

South-central Poland has thousands of anthropogenic lakes. Our study investigated the diversity of the chemical composition and concentration of trace elements in the lake bottom deposits. Particle size distribution was determined using sieve analysis and the combined areometric-sieve method. Concentrations of oxides (SiO_2, TiO_2, A1_2O_3, Fe_2O_3, MnO, MgO, CaO, Na_2O, K_2O, P_2O_5) were determined in sediments using the ICP method. Moreover, loss on ignition was measured and concentrations of Zn, Pb, Cu, Cd, and Ni were determined. Concentrations of As, Ba, Cs, Cr, Co, Ag, and Th were determined using the INAA method. Study results revealed considerable variation in the particle size distribution and chemical composition of bottom sediments. In broad terms the dominant grain size is >0.1 mm. Two other fraction sizes account for roughly equal proportions of the rest, i.e. 0.1-0.02 mm and <0.02 mm. As concerns overall composition, SiO_2 dominated in samples, particularly those where loss on ignition was low. Bottom sediments in the lakes varies in chemistry and pollution levels. The scale of pollution is illustrated by the range of variability of average contents of trace elements in the bottom deposits, e.g.: As (7-63 mg·kg~(-1)), Ba (262-1,630 mg·kg~(-1)), Cs (1.6-134.0 mg·kg~(-1)), Zn (83-3,720 mg·kg~(-1)), Pb (28-731 mg·kg~(-1)), Cr (22-146 mg·kg~(-1)), Cd (0.5-50.3 mg·kg~(-1)), and Cu (9-197 mg·kg~(-1)). The deviations from geochemical background standards found in the bottom sediments of the water bodies examined make them exceptional on a global scale.