PHYSICO-CHEMICAL PARAMETERS OF WATER OF EROSION-THERMOKARST LAKES IN THE YAKUTIAN ARCTIC

Abstract

The paper considers the main physical and chemical parameters of 33 erosion-thermokarst lakes, one ofthe most widespread types of water bodies in Yakutia, formed largely due to the melting of permafrost ground ice. Theconsidered lakes have a small mirror area and shallow depth. The water of the lakes is ultrafresh, mostly very soft, and characterized by low transparency. pH varies in wide ranges from weakly acidic to alkaline values. The water is distinguished by high natural concentrations of total iron and phosphate. Silicon concentrations vary widely, reaching maximum values in the water of northern taiga lakes. The content of ammonium ions in the water of the lakes differs greatly, which may be caused by the influence of local conditions on the accumulation of this biogenic component in water. The ionic composition is dominated by hydrocarbonates (in 88 % of the water bodies) and calcium ions (in 70 % of thesample). In terms of combinations of cations and anions, there dominate magnesium-calcium (45 % of the lakes) andhydrocarbonate waters (76 % of the lakes). Water transparency demonstrates a statistically significant increase with anincrease in the lakes’ altitude above sea level, while silicon concentration increases (zonally) with moving from north tosouth of the study area. These regularities are noted against the background of parallel changes in the ionic compositionand mineralization of water. According to the totality of the investigated hydrochemical parameters, the lakes can bedivided into 2 groups: a cluster of non-forested areas and a group of lakes of northern taiga. The selected lake groupsdiffer significantly in the main hydrochemical parameters: mineralization, total hardness, pH, concentrations of total iron,silicon, and phosphates.