First data on technetium-99 content in the ecosystem of the Yenisei River

The content of a long-lived technogenic radionuclide ⁹⁹Tc in the Yenisei within the territory of radioactive effluents of the Rosatom mining chemical combine (MCC) has been studied. In 2008–2009 the maximal ⁹⁹Tc content in water was registered near the dumping site of the MCC and came to 33 mBq/l. According to analysis of filtered water samples, technetium in the Yenisei water is presented as pertechnetate ion (TcO₄). When moving away from the MCC downstream, the ⁹⁹Tc content in water is decreased, which is caused both by dilution of waste water and by ⁹⁹Tc accumulation by aquatic plants. The ⁹⁹Tc content in the biomass of the aquatic plant Potamogeton lucens came to 82¹⁵ Bq/kg, and the concentration factor (CF) to 8200, which is three times more than the maximal values of the CF of ⁹⁹Tc by the plants in laboratory conditions (2700).     

Change in the circulation regime in the stratified saline Lake Shira (Siberia,Republic of Khakassia)

The in-situ data on the vertical structure and stability of the vertical stratification of saline Lake Shira over the past decade (2007–2015) are analyzed. Simplified mathematical models have shown that strong wind in the autumn of 2014 together with rather thick ice in the winter of 2015 caused a change in the circulation regime of this water reservoir from meromictic (incomplete mixing) to holomictic (compete mixing). Based on the results obtained, a circulation regime for deep saline lakes located in the continental climate zone, in particular, in the arid zones of Southern Siberia (Khakassia, Transbaikal, and Altai) can be predicted under various climate scenarios of the future.     

First data on the uranium content in water of the Yenisei River basin in the area affected by the operation of Rosatom plants

This study is devoted to investigating the content of uranium isotopes in water of the Yenisei River and its tributaries within the territories affected by the operation of Rosatom plants (mining chemical combine, and electrochemical plant). Long-term monitoring of the ²³⁸U content by mass spectrometry carried out in two institutes of the Siberian Branch of the Russian Academy of Sciences first revealed the multiple excess of ²³⁸U over the background content in different areas of the Yenisei River basin, such as the region of the Yenisei River near the effluents of the mining and chemical combine (MCC), and the territories of the Bol’shaya Tel’ and Kan rivers. In these regions, the ²³⁸U content in water reaches 2.1–4.0 μg/l, which exceeds its content upstream from the MCC (0.3–0.6 μg/l) by almost an order of magnitude. The studies of the isotopic composition of uranium in water samples, which were carried out at the Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences, showed the presence of a technogenic isotope of uranium ²³⁶U in the samples from the Bolshaya Tel’ River and revealed the deviation of the isotope ratio ²³⁸U/²³⁵U (167 ± 3 and 177 ± 3) from the equilibrium natural ratio (²³⁸U/²³⁵U = 138). These facts attest to the technogenic origin of part of the uranium in water of the Bol’shaya Tel’ River connected with the activity of MCC. The excess uranium content in the Kan River requires additional studies to ascertain the fraction of uranium of technogenic origin connected with the activity of the electrochemical plant (ECP) (Fig. 1, Table 4).     

Experimental modeling of the influence of the rise in average summer temperatures on carbon circulation in tundra ecosystems

A sealed vegetation chamber was designed and constructed for physical simulation of climate conditions in the Subarctic zone during the spring–summer time. The small laboratory tundra-simulating ecosystem (TSE) was created for comparative evaluation of the rates of soil respiration and of the total balance of carbon fluxes in tundra ecosystems. The test experiment was performed to study the TSE response to a temperature rise in air and soil by 2°C in terms of the intensity of the СО₂ flux. It was shown that this increase in temperature would cause a pronounced shift in the balance of СО₂ production and utilization in the ecosystem from near-zero values to a stable generation of 24 μmol/h of CO₂ per 1 kg of dry biomass.     

Sedimentation rate in Cheko Lake (Evenkia,Siberia): New evidence on the problem of the 1908 Tunguska Event

Doklady Earth Sciences - We estimated the age and sedimentation rate of bottom sediments in Cheko Lake located in southern Evenkia, in the territory of Tunguska Nature Reserve, near the supposed...     

The Influence of Temperature and Humidity on Greenhouse Gas Emission in Experiments on Imitation of the Full Vegetation Cycle of Tundra Ecosystems

Doklady Earth Sciences - Laboratory experiments were conducted in a hermetically sealed growth chamber with two soil samples obtained from the arctic tundra zone with different levels of moisture....     

Okenone in Bottom Sediments as a Proxy for Changes in the Water Level of a Saline Stratified Lake

Doklady Earth Sciences - Long-term measurements show that the sedimentation dynamics of okenone (a carotenoid of purple sulfur bacteria) reflects the abundance of purple sulfur bacteria, the...