This article presents geochemical, mineralogical and microbiological characteristics of five samples of modern bottom sediments in the littoral zone of the high-mountain salty lake Issyk-Kul. The 16S rRNA gene sequencing method shows that the microbial community consists of organic carbon degraders (representatives of phyla: Proteobacteria, Chloroflexi, Bacteroidota and Verrucomicrobiota and families Anaerolineaceae and Hungateiclostridiaceae), photosynthetic microorganisms (representatives of Chloroflexi, phototrophic Acidobacteria, purple sulphur bacteria Chromatiaceae and cyanobacteria) and bacteria of the reducing branches of the sulphur biogeochemical cycle (representatives of Desulfobacterota, Desulfosarcinaceae and Desulfocapsaceae). The participation of microorganisms in processes in the formation of a number of authigenic minerals (calcite, framboidal pyrite, barite and amorphous Si) is established. The high diversity of microbial communities indicates the presence of labile organic components involved in modern biogeochemical processes in sediments. The active destruction of organic matter begins at the water-sediment interface.

Laboratory modeling of Cs, Sr, U, Pu immobilization by phytoplankton of the river Upa, affected after the Chernobyl accident, has been carried out. Certain conditions are selected for strong fixation of radionuclides in bottom sediments due to biogeochemical processes. The process of radionuclide removal from the water phase via precipitation was based on their accumulation by phytoplankton, stimulated by nitrogen and phosphorus sources. After eight days of stimulation, planktonic phototrophic biomass, dominated by cyanobacteria of the genus Planktothrix, appears in the water sample. The effectiveness of U, Pu and Sr purification via their transfer to bottom sediment was observed within one month. The addition of ammonium sulfate and phosphate (Ammophos) led to the activation of sulfate- and iron-reducing bacteria of the genera Desulfobacterota, Desulfotomaculum, Desulfosporomusa, Desulfosporosinus, Thermodesulfobium, Thiomonas, Thiobacillus, Sulfuritallea, Pseudomonas, which form sulphide ferrous precipitates such as pyrite, wurtzite, hydrotroillite, etc., in anaerobic bottom sediments. The biogenic mineral composition of the sediments obtained under laboratory conditions was verified via thermodynamic modeling.

The molecular and crystal structure of the title compound, (C₈H₁₁N₄O₂)₂[PtCl₆], synthesized from hexachloroplatinic acid and caffeine in methanol, was studied by single-crystal X-ray diffraction. The caffeinium cations form a double layer via hydrogen bonds and π-stacking interactions. The Hirshfeld surface analysis showed that the largest contribution to the crystal packing is made by H...H (31.2%), H...Cl/Cl...H (22.6%), O...H/H...O (21.9%) contacts for the cation and H...Cl/Cl...H (79.3%) contacts for the anion.

Sergei Krivonogov was not included as an author in the original publication