Geochemical characteristics of the sapropel sediments of small lakes in the Ob’–Irtysh interfluve

Abstract

More than 20,000 lakes with sapropel sediments are located in southern West Siberia. The work is aimed at an integrated geochemical study of ten sapropel lake systems: a geochemical description of the lake waters, hydrobiological analysis, and analysis of the sapropels (phase and chemical analyses of inorganic matter and elemental analysis of organic matter). The geochemical landscape and low-flow regime of the waters of Siberian small lakes favor massive growth of living organisms. The anaerobic medium at the water/sediment boundary promotes the burial of organic matter as terrigenous material builds up. Based on the results, the sapropels are classified by chemical and mineral compositions into organic, organic siliceous, organic carbonate, organic carbonate-siliceous, and carbonate-siliceous. The sapropels inherit the contents of elements in soils and parental rocks, but the presence of considerable amounts of organic matter in the sediment determines their lower contents with respect to those in the soils of water catchment areas (except U, Cd, Hg, Ca, Sr, and Mn). Biochemical formation of pyrite and calcite is observed in the lake bottom sediments. The calcite formation in the sapropel sediments of Lakes Barchin, Bergul’, Kankul’, and Itkul’ determines their high Ca, Sr, Mn, and Mg contents. Comparison of data on the anion composition of the waters and the organic and mineral compositions of the sapropels has shown that the formation of low-ash biogenic sapropel takes place in lakes whose waters contain a considerable amount of dissolved organic matter and in which HCO3− is a predominant anion. No effect of the cation composition of the waters (Na, Ca, and Mg) on the sapropel composition has been detected. Therefore, Lakes Kankul’, Kachkul’nya, Bergul’, Barchin, and Kambala are the sapropel lake systems with the highest potential.

Authigenic Carbonates in the Water–Biota–Bottom Sediments’ System of Small Lakes (South of Western Siberia)

“…The occurrence and development of small lakes is directly related to the formation of terrain and changes in natural and climatic conditions. The study of sedimentation processes in small lakes has shown that there is a certain set of factors that affects the sediment's geochemical composition [3][4][5][6][7][8][9][10]. The hallmark of each lake is the composition of the water, bedrock, and soil of the catchment area, the sediments and biota, and the life processes which occur both in the lake itself and the corresponding coastal zone.…”

Role of natural and climatic factors in formation of autochthonic organic substance streams in small lakes of the south of Western Siberia

“…Being sensitive to the increased concentration of chlorides (note: only increase in chlorides concentration up to 1 g/l brings to an increase in phytoplankton production), phytoplankton production is practically independent of mineralization. At the same time, with phytoplankton production growth, an increase in nitrogen compound concentrations occurs in water due to the rapid development of nitrogen-fixing cyanobacteria (Strakhovenko et al, 2014).…”

Freshwater Sapropel: Biologically Active Components and Methods of Extraction

“…Generally, fine-grained sediments can deposit alongside the organic sapropel matter, often resulting in a transition from pure sapropel to an almost organic-free mud or 'sapropel mud' (Gomes et al, 2013). Sapropel is thus a rich organic matter that has in it the remains of water organisms (phytoplankton, zooplankton, and macrophytes) and whose formation process differentiates it from its peat precursor (Strakhovenko et al, 2014;Leonova et al, 2015). Sapropel has long been used as a remedy both in veterinary and human medicine.…”

“…Freshwater sapropel is usually found as sediments in lakes, and in some cases in marshes and bogs as well, while brackish water sapropel forms in marine reservoirs. Both types are formed by biochemical, microbiological and mechanical processes (Strakhovenko et al, 2014). Freshwater sapropel is mostly found in the territory of northern and eastern Europe.…”