This paper presents the results of seasonal observations of the geochemical composition of the waters of the large tributaries of Lake Onego. The mineralogy and geochemistry of the suspended matter and the isotopic composition (oxygen-18 and deuterium) of the river waters were studied for the first time. The dependence of the chemical and isotopic compositions of the tributary water on the season and characteristics of the catchment area (swampiness and lacustrine) was revealed. It is shown that the river waters belong to the bicarbonate class of the calcium group and have low mineralization, high color and a similar composition to the main minerals of the suspended matter. It is determined that the difference between the multielement spectra of the water and suspended matter of the different rivers is closely related to the geological and geomorphological structures of river basins. It is established that the quantitative characteristics of the mineral and organic parts of the suspended matter, the ratios of the different minerals andthe size and patterning of the particles of detrital material in the tributaries differ. The change in the mineralogical and geochemical compositions of the suspended matter of each individual river over the year is insignificant. The influence of the river runoff on the formation of lake waters is manifested in the chemical composition of the lake waters. The quantitative ratios of the main ions, biogenic elements and microcomponents in lake water mainly correspond to their ratios in river waters. The mineral part of the dispersed sedimentary matter of the lake in its geochemical characteristics is close to the suspended matter of the river waters.

Below is data on the microbial diversity of natural organic matter from the Dispersion Train of Sulfide Tailings (northern Salaire Ridge, southwestern Siberia, Russia, Ursk Village). Data was obtained using 16s rRNA amplicon directed metagenomic sequencing on Illumina MiSeq. The raw sequence data used for analysis is available in NCBI under the Sequence Read Archive (SRA) with BioProject No. PRJNA670045 and SRA accession number SRX9314152, SRX9314376. The data sequences of the 16s rRNA gene are presented at the links MW142408-MW142413, MW142414-MW142447.

––We studied the bottom sediments of lake systems located in the taiga landscape of Siberia. In the south of Western Siberia, there are 11 lakes in the subzone of the south taiga and 9 lakes in the subtaiga subzone. On the territory of the south of Eastern Siberia in the taiga zone there are 10 lakes on the southern coast of Lake Baikal, 5 lakes on its east coast and 6 lakes are located on the territory of the national park “Alkhanai” in Transbaikalia. Studies of the chemical composition of water, soil, and sediment samples were conducted at the Analytical Center for Multi-Elemental and Isotope Research SB RAS, Novosibirsk. The use of a complex of modern analytical methods in the study of the same lake samples made it possible to obtain more reliable information (1861 samples of bottom sediment were studied). Quartz and feldspars of pelitic dimension dominate in the mineral composition of the terrigenous fraction, organic matter and authigenic minerals (opal, pyrite, illite and sometimes calcite) are added to them during the bottom sediments formation. The absolute contents of the studied elements in the bottom sediments of all lakes are lower than their concentrations in the upper continental crust and sedimentary rocks of the Russian Plate, with the exception of Si, Hg, Cd. In the lakes of the subtaiga of the south of Western Siberia, an exception was established for Ca in the bottom sediments of which carbonates predominate. Contents variations of a number of elements in the bottom sediments of taiga lakes in different regions do not significantly differ. The dispersion of their concentrations between lakes with a total catchment area and lakes from different regions are comparable (Ca, Sr, Al, Mn, Fe, Cd, Hg, etc.). The current sedimentation rate in natural occurrence in the lakes of the taiga zone (southern Siberia) vary from 1.1 to 2.9 mm/year. Moreover, it is comparable to the current sedimentation rate in the lakes of the forest-steppe and steppe zones of south of Western Siberia.

Mercury speciation and the composition of mercury phases in natural and mining-related environments is studied by the thermal release analysis combined with electrothermal atomic absorption spectroscopy (TA-ET-AAS), as well as scanning electron microscopy with energy-dispersive X-ray microanalysis (SEM-EDS). The analyses are applied to laboratory-made samples bearing mercury selenide and to field samples from sites known for relatively high natural or industrially induced Hg background. They are, namely, material from the dispersion train of the Ursk sulfide tailings (Ursk Village, Kemerovo region) and debris precipitated from snow sampled in the Kurai mercury zone (Aktash Village, Gorny Altai). The TA-ET-AAS method works well in discrimination and identification of Hg sulfide and Hg selenide provided that the samples contain sufficient amounts of both compounds, but the sum HgS + HgSe can be determined at any contents of the two compounds. The presence of both mercury sulfide and mercury selenide in the samples has been confirmed by SEM-EDS microanalysis. The temperature ranges for the mercury species (Hg2+; HgS+HgSe mixture; mercury bound with organic matter (Hg-OM), including CH3Hg+) are identical in the laboratory and field samples. Therefore, the suggested approach can ensure fast and reliable detection of Hg phases in rocks exposed to supergene alteration

This paper presents for the first time data on the lateral distribution of total mercury in the water-suspended matter-bottom sediments system for the entire water area of Lake Onego, the second largest lake in Europe. The patterns of the total mercury vertical distribution in two types of bottom sediments stratification, have been established. The total mercury content in the Lake Onego water averages 0.32 ± 0.07 μg/L. The most common form of mercury in water is dissolved+colloid, with the exception of water samples from the Kondopoga and Povenetsky Bays. In the material of the sedimentation traps, the mercury content is 0.5 ± 0.3 μg/g, and in the upper and lower parts of the bottom sediments section is 0.067 ± 0.003 and 0.041 ± 0.001 μg/g, respectively. The paper considers the factors responsible for the mercury content increasing from the bottom sediments up through the sections. These factors include anthropogenic pollution, migration of Hg and its redeposition at the geochemical barrier together with Fe and Mn.