About 150 lakes located in different natural zones of Western Siberia were investigated during performance of a number of grants of the Russian Federation which are carried out on the basis of Tyumen State University. Hydrochemistry and Hydrobiology water have been studied in most of these lakes. Sediment samples were collected from some of lakes in the different depths. The columns of the sediments were separated step by step -1 cm. Grain size of sediments, the general geochemical indicators, composition of a water extract, the content of organic substance, heavy metals were defined in each layer.
Increasing the mineralization in the direction to more southern latitudes is the general regularity in hydrochemistry of lakes. Also the indicator рН has zone specifics. Swamped taiga with the dominance of woody vegetation, for which organic acids are the result of the decomposition, is characterized by high contents of H+. It leads to acidify natural water to pH ~ 4.5-5.5. Acidity of waters goes down by a natural way with advance to the south and reaches median indexes 7.4-7.9. In general, waters of tundra and taiga of Western Siberia have low concentrations of trace elements. Reduced moisture and carbonate content of forest soils cause accumulation of elements such as Zn, Pb.
Step-by-step analysis of the sediments reveals some of general patterns and features in the distribution of geochemical indicators on the depth of sediments of lakes, which located in different climatic zones, including the lakes Tobol-Ishim forest steppe included in the Ramsar Convention.
Increasing the organic matter content in the upper layers of sediment is observed for lakes all zones. The trend to increase of a mineralization and рН is observed also for the majority of lakes. In some of lakes increase of concentration of some metals in the sediments is noted in recent years. Quantitative indicators considerably differ across climate zones, but as a whole trend are similar.
Thus, the geochemical characteristic of sediments of lakes, which are not exposed to anthropogenic influence, allows speaking about a general trend of increasing water mineralization, рН and contents of organic matter. Probably these changes can be bound to existence of climatic changes in the considered region.
*The study was supported by a project of the Tyumen State University aimed at executing Resolution 220 of the Government of the Russian Federation, and the Russian Foundation for Basic Research (project no. 14-05-00956-a).