Skład chemiczny wód nadosadowych i roztworów porowych w osadach jeziora Wigry

Abstract

Chemical composition of overlying water and pore water in sediments from Wigry Lake.A b s t r a c t. This research was conducted in the area of Wigry Lake, which is one of the largest and deepest lakes in Poland. It consists of several parts which differ in size, depth, number of islands, chemical composition of water and the nature of shores. To assess variations in chemical composition of the pore water and overlying water, seven research positions were selected. They belong to one of three zones: profundal, littoral and dystrophic. Water characteristics are presented in statistical approach, using the background concentrations determined by the probability method. Chemical composition of the overlying water taken from profundal locations is similar to that from littoral parts of the lake. These are multi-ion waters of HCO3–SO4–Ca, HCO3–SO4–Ca–Mg, HCO3–Ca, HCO3–Ca–Mg type. They have low mineralization (268–552 mg/dm3) and are weakly alkaline (pH from 7.49 to 7.77). The situation is different with the composition of the water taken from the dystrophic lake (SO4–Ca–Mg). These are low mineralization (28 mg/dm3) and acid waters (pH = 5.35). Dominant in pore solutions is multi-ion HCO3–Ca, HCO3–Ca–Mg or HCO3–SO4–Ca–Mg water with mineralization 445–2032 mg/dm3 and pH between 7.39–8.23 (littoral positions), HCO3–Ca–SO4 and HCO3–Ca–Mg water with mineralization 479–762 mg/dm3 and pH from 7.59 to 7.89 (profundal positions). Definitely different chemical compositions have pore water from dystrophic lake: hydrochemical type changes with depth, from the HCO3–SO4–Ca, via HCO3–SO4–Ca–Na and HCO3–SO4–K–Ca, to the HCO3–SO4–Na–Ca. Their mineralization is very low (49–69 mg/dm3) and pH changes from 7.25 to 8.01.