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Geochemistry of surface sediments of a coastal Lake Sarbsko (northern Poland)

Michał Woszczyk¹, Roman Cieśliński², Waldemar Spychalski³

¹ Department of Quaternary Geology & Palaeogeography, Adam Mickiewicz University, Dzięgielowa 27, 61-680 Poznań, Poland, e-mail: woszczyk@amu.edu.pl

² Department of Hydrology, Gdańsk University, R. Dmowskiego 16a, 80-264 Gdańsk, Poland, e-mail: georc@univ.gda.pl

³ Department of Soil Science, Poznań University of Life Sciences, Szydłowska 50, 60-656 Poznań, Poland, e-mail: spychal@au.poznan.pl

Abstract

The main goal of the presented research was to investigate spatial distribution of surface sediments and to recognize relationships between chemical composition of water and sediments in a coastal Lake Sarbsko (northern Poland). The Lake Sarbsko is a freshwater basin. The water column is well oxygenated and waters exhibit only minor spatial variability of chemical composition indicating rapid and good mixing. Surface sediments of Lake Sarbsko are strongly diversified with respect to chemical composition. The sediments of Lake Sarbsko are characterized by elevated content of terrigenous silica indicating enhanced input of clastic material from the watershed and/or increased dynamics of the lake waters. Moreover, SiO_2ter is strongly negatively correlated with SiO_2biog, organic matter and element contents, which argues for diluting effect of the former towards authigenic components of sediments. Basically, terrigenous silica (quartz) content is highest in the lake shores and declines towards the lake center. Biogenic silica, organic matter and most of elements display reversed tendency. CaCO₃ was encountered in three isolated areas, where it co-occurs with FeS. It is anticipated that precipitation of calcite in Lake Sarbsko resulted from postdepositional processes. Spatial distribution of Fe, Mn, Ca, Mg, Na and K in Lake Sarbsko is also governed by their geochemical affinities to organic matter (Fe), Fe/Mn oxides (Fe, Mn), sulphides (Fe), clay minerals (Na, K, Mg, Mn) and carbonates (Ca, Mn).