Systematization of Organic-Mineral Bottom Sediments in Small Lakes of the Southern Western Siberia: A Landscape Zonation Context

The systematization of organic-mineral bottom sediments of 38 small lakes in the south of Western Siberia has been carried out, taking into account landscape and sapropelation zones. The study covers the subtaiga, forest-steppe, steppe and subzones of ribbon forests, where 494 samples of bottom sediments were taken. The analytical work was performed at the Analytical Center for multi-elemental and isotope research SB RAS (Novosibirsk) using a set of modern analytical methods: determination of ash content, elemental composition (AAS, ICP-AES, and X-ray fluorescence), mineralogy (X-ray Diffraction, SEM). To systematize bottom sediments, the classification of bottom sediments developed by the authors was applied based on ash content (types), Si/Ca ratio (classes) and the type of dominant primary production (genetic species). The relationship between the distribution of bottom sediment types and landscapes, as well as sapropelation zones, has been identified. Organic-mineral and mineral-organogenic types prevail in the subtaiga/forest-steppe (intensive zone of sapropelation). Mineralized sapropels and mineral silts dominate the steppe/ribbon forests landscape (a zone of weak sapropel formation). Organogenic bottom sediments are extremely rare in all landscapes and sapropelation zones. The distribution of sediment classes among all the lakes considered is uneven, with the predominance of lakes with a silicon sediment class. Planktonic-macrophytic and macrophytic-planktonic genetic species are predominant regardless of the landscape and sapropelation zone. Local features of the geochemical and mineral composition in nearby lakes have been established using the example of Lakes Peschanoe and Chistoe (forest-steppe landscape), which is due to differences in the genetic species of sapropel. The proposed systematization makes it possible to assess the resource potential of sapropels for agriculture and reclamation, and serves as a basis for monitoring anthropogenic and climatic impacts. The unique composition of the bottom sediments of each individual lake underscores the need for detailed geochemical analysis when planning environmental management.