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The article presents numerical experiments results of the interaction process of the air and the flowing water film on the surface of a cellular humidifier during adiabatic air treatment. Experiments were carried out for irrigated packings of various depths using the StarCCM + program. The results obtained can be applied for improving the methods for calculating heat and mass transfer processes and increasing the energy efficiency of units with irrigated packings.

A new experimental method for the determination of the isotopic composition of authigenic uranium in Lake Baikal (Siberia) sediments has supplied a record of (234U/238U)aut ratios during the past 150 ka with a resolution of ca. 200 years. Reconstruction of the (234U/238U)aut activity ratio as a proxy for lake water composition shows that the uranium isotope disequilibrium has not stayed constant throughout this period: it varied greatly in response to regional climate. The 234U/238U activity ratio in Lake Baikal paleowaters was inferred to be high during interglacial time (∼ 1.85–2 during MIS 5.5 and the Holocene; ∼ 1.4–1.7 during MIS 5.1 and 5.3) and dropped to ∼ 1.16 ± 0.01 during glacial time. The variability in the deduced 234U/238U ratios of Lake Baikal waters of the past may have been caused by the climatically-modulated redistribution of contributions of riverine discharges from different provinces of the very large catchment of the lake. Aridity during ice ages was more pronounced in the south of eastern Siberia and in northern Mongolia relative to that in the northern regions of the Lake Baikal watershed. The southern contribution of riverine input into the lake was essentially absent during glacial periods. Records of some elements (Ca/K, Sr/Rb, Si/Al, La/Th, U/Th, CIW) from the bottom sediments of Lake Baikal during the last 0.5 Myr with a resolution of ∼ 2 kyr have also been obtained. Coupling these data with records of weathering indices shows that not only riverine waters but also terrigenous material delivered into Lake Baikal from different regions of the very large watershed during interglacial and glacial times. Glacial erosion delivered fine siliciclastic material (“glacial milk”) mainly from the nearest mountain glaciers situated in the northwestern region of Lake Baikal while during warmer periods terrigenous material was sourced from the surrounding river valleys. A conceptual model for the simulation of the fluvial discharge gradient between the northern and southern provinces of the Lake Baikal watershed is proposed and a first-order simulation of past changes in the contribution of the Selenga River to the lake water budget is given.

A study of 15 gravity cores reveals consistent patterns of lithologic change throughout the Lake Hovsgol basin. Sediments of the last glacial are composed of calcareous clayey silt with an admixture of coarse material from sand to gravel. During the last deglaciation, a basin-wide deposition of finely laminated carbonate mud took place and was ultimately succeeded by the deposition of diatomaceous clayey ooze during the entire Holocene interval. Diatom productivity in Lake Hovsgol during the early Holocene was higher than today, but declined by ca. 6.6 cal ka BP. Sedimentation rate estimates for post-glacial section range from 1.5 to over 6.7 cm/ka for different parts of Lake Hovsgol. Rates appear to have decreased in the late Holocene. The last glacial maximum (LGM) corresponded to a dramatic low stand of Lake Hovsgol on the order of 100 m below today's level, as reflected by littoral facies retrieved in cores from intermediate depths. Age dating of plant fragments in these sediments suggests that lake level started rising no later than 15.4 cal ka BP. By the beginning of the Holocene, Lake Hovsgol evolved from a low-level closed basin lake to an overflowing freshwater lake. The observed dramatic lithologic change and evidence for lake-level change suggest that Lake Hovsgol may in fact serve as a sensitive ‘water gauge’ in continental interior Asia and that the Hovsgol sedimentary record preserves reliable proxies for past changes in effective moisture balance in the Lake Baikal catchment area.

Sedimentary sections from Lake Baikal in Siberia and Lake Hovsgol in Mongolia show that during the Last Glacial Maximum (LGM), planktonic/benthic diatoms, chrysophyte cysts, sponge spicules and zooplankton remains did not accumulate in the lake sediments. The combined data suggest a drastic lowering of photosynthetic production and perhaps the collapse of the ecosystems of both lakes due to significant environmental changes during the LGM. Both lakes were almost uninhabited during the LGM. Starting from ∼12,000 to 13,000 14C years ago, the planktonic communities redeveloped and primary production increased in both lakes. As a result, Holocene sediments contain abundant and well-preserved planktonic/benthic diatoms, stomatocysts, sponge spicules and zooplankton remains. The ecosystem stress in Lake Baikal during glacial time appears to be due to a decrease in nutrient loading from the watershed, lowering of surface water temperature, and very low transparency of water and ice. We believe that endemic species in Baikal survived during glacial ecological catastrophes in refugia that could have been a source of species that invaded and repopulated Baikal after intense and long glacial winters. The ecosystem stress in Lake Hovsgol during glacial time appears to be due primarily to drastic lake level falls, and changes in water chemistry. At the beginning of the Holocene, Lake Hovsgol was reoccupied again by cosmopolitan species probably from surrounding small lakes and rivers. In addition to the LGM results, we also show that Lake Baikal planktonic diatom species diversity during the last 350 ka is closely related to solar insolation fluctuations caused by the 23 and 41 ka cycles of the Earth's precession and obliquity. Our results also indicate that Baikal's planktonic diatom species diversity, as measured by the Shannon–Weiner index, correlates with the oxygen isotope record that represents changes in global ice volume.

This work presents a detailed, orbitally tuned biogenic silica record of continental paleoclimate change during the Brunhes chron. The Brunhes/Matuyama boundary lies within the warm isotopic stage 19 in Baikal, and the boundaries between eight lithological cycles correspond to terminations in the marine oxygen isotope record. The high amplitude and resolution of climatically driven changes in BioSi content in Lake Baikal sediments permits tuning of almost every precessional cycle during the Brunhes and reveals the structure of interglacial stages. For example, the last three interglacial stages (MIS 5, 7, and 9) clearly consist of five substages (a, b, c, d, e) corresponding to precessional insolation peaks. Abrupt and intense regional glaciations in Siberia during substages 5d and 7d were driven by extreme insolation minima. During substage 9d cooling was more gradual in response to more moderate forcing. The impact of strong glaciation is also observed in the middle of stage 15, where full glacial conditions appear to have lasted for over 30,000 yr during substages 15d, 15c, and 15b. Marine oxygen isotopic stage 11 appears to be the warmest period during the Brunhes in the Lake Baikal record, with at least three substages.A new hypothesis is presented regarding the response of the Lake Baikal BioSi record to insolation forcing. Based on the mechanism controlling modern diatom blooms, biogenic silica production is hypothesized to be dependent on changes in the heat balance of the lake and consequently on changes in the thermal structure of the water column. This mechanism is also sensitive to short-term sub-Milankovich cooling events, such as the mid-Eemian cooling, the Montaigu event during substage 5c, and a cooling which appears to be analogous to the Montaigu event during substage 9c. The continuity of the Lake Baikal paleoclimate record, its sensitivity to orbital forcing, and its high resolution make it an excellent candidate for a new “paleoclimatic stratotype” section for continental Asia.

This chapter gives data on the carbon, nitrogen, and phosphorus contents, and their ratios, in the suspended matter (SM), unfiltered water, and sediments of Lakes Baikal and Hovsgol, as well as in their sources (precipitation and tributaries). Both lakes have been found to show similar features (colorless water, an absence of N-NH4 + and N-NO2 -, and a high content of dissolved oxygen) and distinctive factors (contents of silicon and chlorophyll-a, and the vertical distribution of carbon, nitrogen, and phosphorus).

The sedimentary record of Lake Baikal reveals details about the climatic response of continental Asia during the interval 423-362 Ka BP, corresponding to marine oxygen isotope stage MIS 11. The MIS 11 record in Lake Baikal is marked by two plateaus of high biogenic silica content corresponding to MIS 11.3 and 11.2. The middle part of MIS 11 (substage 11.2) exhibits the highest biogenic silica accumulation, reflecting the warmest regional climate, of the last 450 Ka. These interglacial conditions in continental Asia were uninterrupted for about 32 Ka, making MIS 11 the longest interglacial in Siberia, greatly exceeding the duration of interglacial conditions during MIS 5e, 7e and 9e. This extremely long and warm interglacial period of MIS 11.3-11.2 in Siberia ended abruptly with dramatic cooling at 394-390 Ka BP. This cooling resulted in brief mountain glaciation in Siberia due to the amplified response of continental Asia to insolation forcing. The cooling during MIS 11 produced irreversible change in the climate of continental Asia as suggested by diatom succession and by biogenic silica accumulation. Diatom species composition further reveals more complex structure of MIS 11 and makes a strong case for insolation control of diatom production in Lake Baikal.

Publisher Summary This chapter describes the paleoclimatic record over the period of 5 million years based on variations in diatom abundance in the sediments of a 200 m core obtained from Lake Baikal. The data represent a long, continuous continental record of climate changes in Central Asia during the Late Cenozoic. The record shows the climatic cooling trend that started in Pleistocene and is superimposed on the short-term cyclic climatic variations controlled by the Earth's orbital parameters. The record also reveals the presence of the two cold episodes (each about 300 Ka long) at the time intervals 2.82–2.48 Ma and 1.75–1.45 Ma characterized by glaciations at their maximum phases. These cooling periods in Lake Baikal record are also registered as global cooling in other paleoclimate records of the Northern Hemisphere. The continental record of Lake Baikal contains the majority of climatic events found in marine records and demonstrates that continental regions of Asia responded to all major changes in the Earth's climate recorded in the long oxygen isotopic records.