The Choygan area of southern Siberia, Russia hosts a variety of CO 2-rich thermal mineral and other waters emerging from springs at temperatures between 7 • C and 39 • C. Chemical analyses of the spring waters (n = 33) were carried out to characterise the waters and determine their origin. A continuum of compositions was observed between relatively lower temperature (7 • C) HCO 3-Ca-Na dominated waters with relatively low amount of total dissolved solids (TDS) and high Eh, and higher temperature (39 • C) HCO 3-Na-Ca dominated waters with higher TDS and lower Eh-this reflects largely conservative mixing of these components between near surface low temperature, oxidising groundwaters and higher temperature, more reducing thermal waters derived from a deeper geothermal reservoir. Stable isotopic data are consistent with all the water ultimately being derived from meteoric water that has undergone varying degrees of isotopic fractionation following evaporation. The inferred δ 18 O and δ 2 H isotopic composition of the unfractionationed meteoric waters is lighter than that expected that of mean annual local precipitation, which together with a strong negative correlation between δ 18 O and the elevation of the sampled discharging springs, suggests recharge at higher elevations (1600 m to 3000 m; average 2600 m). Reservoir temperature, calculated using geothermometers and an analysis of saturation indices of plausible reservoir minerals, ranged from 70 • C to 100 • C at an inferred depth of 2 to 3 km. Not all chemical components were found to follow conservative mixing behaviour. In particular, (i) the CO 2 contents of the waters were highly variable, suggesting either varying degrees of degassing and/or near discharge admixture with air, and (ii) SO 4 concentrations in the lower temperature thermal CO 2-rich waters were highly variable, suggesting a role of near surface oxidation processes, for example of pyrite, in modifying the concentration of redox sensitive components. Limited δ 13 C data are consistent with the CO 2 predominately being derived from dissolution of metamorphic/igneous carbonate minerals in the reservoir. Based on geological conditions, isotope and chemical data, a conceptual circulation model of the Choygan hydrothermal system is proposed.

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The flora of small non-flowing lakes of the Narach lake group located on the territory of the Narachanski National Park (Belarus, Minsk region, Myadelsky district) was studied. The taxonomic composition of the flora numbering 126 species of vascular plants belonging to 85 genera from 42 families was revealed. Three plant species which are included in the list of protected taxa in Belarus were found – Liparis loeselii (L.) Rich. (Lake Shestakovo), Aldrovanda vesiculosa L. (Lake Shestakovo) and Isoëtes lacustris L. (Lake Beloe). Based on the annotated list of species presented in the work, taxonomic, geographical, ecological-coenotic and ecobiomorphological analyzes of the flora of water bodies were performed. According to the taxonomic and environmental structure, the flora of the studied lakes is shown to be traditional for this territory. The differences in the flora of the studied lakes are mainly due to their trophic status and, to a lesser extent, due to the diversity of biotopes and the nature of the anthropogenic load. Information on the nature of overgrowing of these water bodies is provided.