Home – Home – Jornals – Thermophysics and Aeromechanics 2021 number 6

The nature of the water vapor self-continuum absorption is investigated within fundamental bending and stretching bands at 279-351 K. The integral contribution of the water dimer absorption to the experimental water vapor continuum is preliminary estimated based on the available spectroscopic information as 70-40% in the 1600 cm^-1 band and 90-60% in the 3600 cm^-1 band; the inverse temperature dependence is shown. The analysis of the temperature dependences of the continuum absorption and its components indicates the probable contribution of the water monomer line wings to the continuum along with the absorption by water dimers.

The correlation between the radon influx into the atmosphere and the formation of ions has been studied based on observations at the Fonovaya Observatory of Institute of Atmospheric Optics, Siberian Branch, Russian Academy of Sciences. This correlation is shown to be stable in the period from October to January. In the other months, the correlation is disturbed. However, if the events of nucleation and lightning discharges are removed from the data set, then the correlation is kept throughout the year.

The results of microscopic analysis of 114 samples of solid atmospheric precipitation (snow) taken during two cold periods (2015/2016 and 2016/2017) in the south of Western Siberia for the presence of bioaerosols are presented. With the use of trajectory, synoptic and cartographic analyses, the main regions were identified from which pollen grains and algae arrived with air masses and precipitated with atmospheric precipitation.

The comparison of data on the moisture content of the troposphere obtained from GPS satellite monitoring, radiosondes, and water vapor radiometer measurements at permanent observation points IRKM (Irkutsk, 52°13¢ N, 104°19¢ E, h = 511 m) and BADG (Badary, 51°46¢ N, 102°14¢ E, h = 838 m) is presented. Values of the total zenith tropospheric delay for the BADG observation point derived from processing of the primary GPS data with the GAMIT and Bernese software packages are compared. Time series of tropospheric moisture content for the IRKM station derived from GPS observations and radio soundings and for the BADG station found from GPS observations and water vapor radiometer measurements during 2020 are analyzed and compared. The use of the GPS method for monitoring the moisture content of the troposphere at the network being created in the Baikal region has been substantiated.

The measurements of aerosol backscattering ration in the lower mesosphere by means of sounding at two wavelengths of 355 and 532 nm at lidar stations of Roshydromet from 2012 to 2021 are presented. Appreciable increase in the backscattering ratio R has been observed in the altitude range 50-70 km since 2018. In 2019-2020, the average R attained 1.25 at an altitude of 70 km. The temperature measurements by the Rayleigh method at 532 nm in this period show a positive bias of the temperature of up to +20 K. The two-wavelength temperature measurement method allows one to eliminate this error.

The calculation of the light backscattering matrices of atmospheric hexagonal ice particles distorted with different methods within the physical optics approximation for the case of arbitrary spatial orientation and single scattering was carried out. The hexagonal prism with height of 31.62 mm and external diameter of 22.14 mm, which is typical for “column” shape that is occurs in cirrus clouds, was chosen as the base geometrical shape for distortion. The calculation was carried out for particles generated with three methods of distortion of base facets: tilt, pike, and cavity. The angle of distortion varied from 0 to 50° for every type of particles. The wavelength of incident radiation was equal to 1.064 mm.

Trends in long-term changes in the annual average and seasonal average temperatures within the atmospheric boundary layer in Siberia over 1981-2020, estimated based on observations at 24 aerological stations in winter, spring, summer, autumn, and for the year as a whole, are analyzed. It has been established that during the 40-year period under study, statistically significant positive trends in the annual average air temperature are observed throughout the atmospheric boundary layer over the Siberian territory; the trend value decreases from north to south and with altitude. The main contribution to the regional warming of the atmospheric boundary layer climate over Siberia is made by the spring, summer, and autumn periods. The warming of the boundary layer has intensified in the past decade, from 2011 to 2020.

The annual variability of aerosol microstructure of the near-surface aerosol has been studied based on solving the inverse problem for spectral measurements of aerosol extinction coefficient. The numerical algorithm based on the method of integral distributions was used to solve the inverse problem. The geometrical section, volume concentration, and mean radius of aerosol particles are considered. Aerosol microstructure parameters were estimated for the fine and coarse fractions and the total ensemble of particles. Estimates of the statistical characteristics of the distributions of aerosol microstructure parameters on monthly intervals are obtained. It has been shown that the fine particles make the main contribution to the total geometrical cross section of the near-surface aerosol, which varies within 73-88%. The coarse fraction predominates in the volume content of the near-surface aerosol, averaging about 75% over the entire observation period. During the observation period, the dependences of the monthly mean values of the geometrical cross section and the volume concentration of the fine aerosol had a monotonically increasing character. The volume concentration of fine particles has increased more than four times. The monthly average values of the volume concentration of coarse particles have changed twice.

Results of field and laboratory experiments on non-line-of-sight communication under water and in a model air medium are considered. For the first time, the experiments have been performed for non-coplanar communication schemes of the first (when single scattered radiation was present in the information-bearing signal) and second type (when this radiation was absent). The feasibility of communication through an ice interface with an underwater source was confirmed. It was shown that transition from the coplanar to non-coplanar communication scheme, accompanied by changes in the angles defining mutual orientation of the optical transmitter and receiver axes, can cause nonlinear changes in communication errors. The explanation of this dependence is suggested.

The results of studies of the precipitable water vapor (PWV) at Terskol, Kislovodsk, Nauchny, Sheki, and Hunzakh sites are presented. The comparative analysis of changes in GNSS-derived PWV and PWV estimated from the ERA-5 reanalysis database has been performed. The ERA-5 data make it possible to reveal new sites suitable for millimeter/submillimeter telescopes. In view of the comparatively low total cloud cover, Rutulsky and Agulsky regions are the most promising for building millimeter/submillimeter telescopes in the North Caucasus (Dagestan, mt. Horai (3521 m), Kаtаlnats (3780 m), mt. Karah (2876 m), and mt. Sindaky (2849 m)).

The modified method for retrieving the altitude profiles of the optical turbulence parameters is described. The altitude profiles of the dimensionless turbulent parameter and the structural constant of the air refractive index fluctuations are retrieved from the analysis of the Large Solar Vacuum Telescope data. The optical turbulence profiles are analyzed. It is found that the effective turbulence altitude is close to 2000 m at the site of the Large Solar Vacuum Telescope.

We consider the features of the weakening of the stratospheric polar vortex that precede its breakdown. To analyze the abnormal dynamics of the polar vortices, we used the method of estimating the main parameters of the vortex by delineating its edges using the geopotential values determined from the maximum temperature gradient and maximum wind speed according to the ERA5 reanalysis data. As a result, we showed that the criteria for the abnormal weakening of the polar vortex preceding its breakdown is a decrease in the vortex area to less than 10 million km² and a subsequent decrease in the average wind speed along the vortex edge below 30 and 45 m/s in the lower and middle stratosphere, respectively. In this case, the polar vortex becomes a small cyclone (characterized by high temperatures and the absence of a dynamic barrier) and collapses within three weeks.

The three-dimensional structure of the flow in the near field of a wake behind a cylinder in a slot channel was experimentally investigated. Based on direct measurements of three-component volumetric velocity distributions, the ave-raged flow structure in a wake behind the cylinder is presented for the cylinder height-to-diameter ratio of 0.4 and Reynolds number Re _D = 3500. It is shown that the horseshoe vortices formed in front of the cylinder affect the flow structure significantly. It is found that two quadrupole distributions of mean longitudinal vorticity are formed in the near wake.

Various studies have shown that a baffle installation can enhance heat transfer in the backward facing step flows. It increases the pressure drop in the channel. In this study, the main focus is to find the best installation location and orientation for a given baffle to maximize its thermal performance. A steady incompressible laminar flow is considered in a channel with an expansion ratio of 2. The bottom wall of the channel is partially heated with a constant heat flux. For numerical modeling, the Navier-Stokes equations were solved using the finite element method. Two new concepts entitled the maximum temperature constraint and the performance evaluation parameter (PEP) were defined to characterize the problem. Grid independence study was performed, and the numerical simulation was validated successfully with the published results. As the main result, a small zone close to the step was identified for the baffle installation which gives higher values of the PEP and constrained PEP. It was shown that under the present circumstances, the case ( X _b, Y _b, a ) = (0.3, 0.9, -15°) gives the highest heat transfer enhancement (75 %) and the case ( X _b, Y _b, a ) = (0.3, 0.9, 30°) is the most optimum case from the thermal performance point of view with constrained PEP which is of 1.257.

The article presents the results of studies of a coolant flow behind the mixing intensifier grids of TVS Kvadrat fuel assemblies of the PWR. The purpose of the work is to evaluate the efficiency of mixing the coolant behind the intensifier grids of various designs and to choose their optimal design. To achieve this goal, a number of experiments are carried out on the aerodynamic research stand with scale models of fuel rod bundle fragments of fuel assemblies with mixing intensifier grids, equipped with turbulizing deflectors of various profile shapes. The cells located near the guide channel and regular cells are selected as the research area. The choice of the research area is due not only to the need to obtain a hydrodynamic picture of the coolant flow in characteristic cells and the choice of the optimal shape of the deflector, but also due to the necessary assessment of the influence of transverse coolant flows from the area of the guide channel on the flow motion in adjacent cells. The coolant flow pattern is represented by vector fields of transverse velocities, cartograms of the distribution of transverse and axial velocities, as well as graphical dependences of the distribution of the flow velocity components. Analysis of the spatial distribution of transverse and axial flow velocities allows studying and detailing the flow pattern of the coolant. Evaluation of the efficiency of the coolant mixing behind the grids and determination of the optimal shape of the deflector profile are carried out on the basis of a comprehensive analysis of the hydrodynamic pattern of the coolant flow and the parameters of intracellular vortex formation and intercellular mixing. The experimental results can be used in the engineering justification of structural solutions for the design of active zones of PWR reactors with TVS-Kvadrat. The accumulated database of experimental data is used for verification of CFD programs (both foreign and domestic development), as well as programs for thermal-hydraulic cell-by-cell calculation of active zones.

Two wind tunnels were employed for study of a thick teardrop airfoil with the relative thickness of 40 %. Experiments were conducted for Reynolds number in the range from 2 10⁴ to 12 10⁴ and the angle of attack from -10° to +10°. The weight-in-flow measurements and PIV-method visualization were performed. Experiments revealed a strong impact of the free-stream pulsations on the aerodynamic force coefficients. The following phenomena were demonstrated: drag crisis, hysteresis for the lift force vs. angle of attack, and reversing for the lift force direction. Data analysis investigates the roots of these effects.

The influence of the Pitot probe on total pressure measurements in the near-wall flow in the zone of reattachment of a supersonic separated flow past a compression corner is considered. If the total pressure is measured near the model wall, a local maximum is observed in the region downstream of the reattachment line. This maximum can be either a physical structural element of the separated flow (high-pressure layer in which the total pressure reaches 0.8-0.95 of the free-stream total pressure) or a possible measurement error. The present study reveals the existence of a measured total pressure peak in the boundary layer on a horizontal flat plate and flat wedges. This peak is not associated with the high-pressure flow, but is rather a result of probe interaction with the model wall. The amplitude of this peak is found to depend on the ratio of the probe size and the boundary layer thickness. It is shown that the degree of the probe influence leading to distortion of the measurement results is smaller approximately by an order of magnitude than the maximum value of the measured total pressure in the high-pressure layer in the reattachment zone.

Due to the absence of experimental data for constructing the phase diagram of a liquid and gaseous mixture of hydrogen with oxygen, it is constructed by modeling. Model diagrams previously predicted (Deiters et al., 1993) by two methods (I and II) at pressures up to »100 MPa and a temperature up to »100 K have significant differences, which are considered by the authors as an approximate measure of the uncertainty of the knowledge of the real phase diagram of this mixture. In this paper, the phase diagram of a mixture of hydrogen with oxygen is determined using the previously proposed modified van der Waals model for individual and mixed compounds. Calculations were performed in two (A, B) variants differing in the binary interaction parameter. To control these variants, they were used to construct model diagrams of mixtures of hydrogen with nitrogen, argon, and methane for which there are experimental data in the range of pressures and temperatures comparable to those mentioned above for the mixture of hydrogen and oxygen. Variant B is more realistic as it is in better agreement with experiment compared with variant A. The phase diagram calculated by method B for a mixture of hydrogen with oxygen is close to the calculation by method I, which indicates that it is more realistic than method II.

To investigate the mechanism of the flame-vortex interaction induced by an obstacle, a numerical research of premixed methane-air flame dynamics in an obstructed chamber is described. Numerical simulations are performed with the OpenFOAM open-source CFD code. The simulation images show that the flame propagation process can be divided into four typical stages. A series of instabilities are captured in the simulation during flame propagation. More importantly, the numerical results demonstrate that a longer obstacle allows a sufficient accelerating time, which can give rise to a higher explosion overpressure and faster flame tip speed.

The laminar burning velocities of a stoichiometric CH₄-N₂O mixture diluted with N₂ [30 ÷ 60 % (by volume)] at various initial pressures (1 ÷ 10 bar) and various initial temperatures (273 ÷ 423 K) are obtained by numerical modelling of their premixed adiabatic flames. The modelling is performed with the Cosilab package using the GRI-Mech 3.0 mechanism based on 53 chemical species and 325 elementary reactions. The calculated laminar burning velocities are compared with available literature data. The influence of the initial conditions (pressure, temperature, and N₂ concentration) of CH₄-N₂O-N₂ mixtures on the laminar burning velocities, maximum flame temperature, heat release rate, and peak concentrations of the main reaction intermediates is investigated and discussed. Using the correlations of the laminar burning velocities with the initial pressure and the average flame temperature, the overall activation parameters of CH₄-N₂O oxidation are determined.

Regimes of detonation burning of TS-1 aviation kerosene in an air flow in a flow-type radial vortex combustor 500 mm in diameter with exhaustion toward the center are obtained. The parameters varied in experiments are the diameter of the combustor exit cross section (from 250 to 125 mm) and the shape of one of the combustor walls. The air flow rate in detonation burning regimes is 5.23 ÷ 23.85 kg/s, and the kerosene flow rate is 0.49 ÷ 1.2 kg/s. The fuel-to-air equivalence ratio is varied in the interval 0.58-2.24. Kerosene is bubbled with air before its injection into the combustor. Pulsed detonation with radial waves and continuous spin detonation with one rotating detonation wave with a velocity close to the Chapman-Jouguet detonation velocity are observed. The structure of detonation waves and the flow in their vicinity display no principal differences from those observed previously in a plane-radial combustor with a smaller diameter (204 mm). A strong effect of detonation waves in the combustor on the air and kerosene injection systems is detected. Centrifugal forces acting on the mixture flow and detonation products are enhanced as the combustor exit diameter decreases (as the combustor length increases). For identical specific flow rates of kerosene-air mixtures, the pressure near the cylindrical surface of the combustor in idle runs is found to be higher than that in the case of detonation.

Ti₃AlC₂ and Ti₃SiC₂ single-phase MAX phases were obtained by preliminary mechanical activation (MA) of initial mixtures of powder reactants in a high-energy planetary ball mill with subsequent self-propagating high temperature synthesis (SHS). The MA and SHS products were studied by X-ray diffraction and electron microscopy.

The generation of thermoEMF during combustion of titanium and boron powder mixtures under pressure has been studied. It has been shown that when the boron content in the mixture is less than 2.5 mol, thermoEMF is generated in the form of a constant positive signal, at 2.5 < B < 4.0 mol, it is generated in the form of a constant negative signal, and at B > 4.0 mol, in the form of a negative pulse. The generation of a positive signal is due to the electronic conductivity of titanium particles, and the generation of a negative signal is due to the hole conductivity of boron particles. Experimental dependences of the maximum temperature, average burning speed, and the widths of the combustion wave and thermoEMF on the mole fraction of boron in the mixture have been obtained. It has been shown that the greatest width of the combustion wave is about ~10 mm, and its minimum (critical) width is 1 mm.

The combustion of highly exothermic multicomponent mixtures of Co₃O₄/Cr₂O₃/Nb₂O₅/Al with additives of MoO₃, WO₃, and carbon (graphite) under overload up to 200 g has been studied. It has been shown that the introduction of carbon into the initial mixture has a noticeable effect on the combustion, formation of chemical composition, and structure of combustion products. With an increase in the mass content of carbon in the initial mixture from 0 to 3.9 % the burning rate decreases by more than half, and the rate of dispersion of combustion products and the weight loss increase markedly. Under the action of overload, the two-phase melt of combustion products is stratified into two layers, which crystallize upon cooling. The lower metal layer contains Co, Nb, Cr, W, Mo, C, and impurity aluminum, and the upper layer contains mainly Al₂O₃. With an increase in carbon content above 4.0 %, the separation of the metal and oxide phases stops, and with a further increase, the flammability limit is reached. With an increase in carbon content in the mixture from 0 to 3.9 %, its concentration in the cast composite material reaches 5.4 %, the Al content is about 4.0 % and the content of Co, Nb, Cr, W, and Mo changes slightly. The combustion slag contains reducer metal oxide (Al₂O₃) and Cr₂O₃ impurity dissolved in it.

In this work, differential scanning calorimetry tests are performed on eutectic mixtures of 1-methyl-3,4,5-trinitropyrazole (MTNP) and 3,4-bis(3-nitrofurazan-4-yl)furoxan (DNTF) with different molar ratios, phase diagrams of the melting temperature and composition and those of the melting enthalpy and composition are constructed. Then, the ratio of the lowest eutectic system is obtained on the basis of the phase diagrams, and the lowest eutectic mixture of MTNP/DNTF is characterized by energy dispersive X-ray spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric mass spectrometry, mechanical sensitivity test, and detonation performance calculation. The results show that the ratio of the lowest eutectic system of MTNP/DNTF is 70.3/29.7, and the melting point is 78.9 ^oC, which is very close to the melting point of TNT. Raw MTNP and raw DNTF can be uniformly mixed to form the lowest eutectic, and there is no chemical reaction between the raw materials, only a certain intermolecular force exists. The products of thermal decomposition are H₂O, NO, N₂O, and CO₂. The lowest eutectic mixture also has lower mechanical sensitivity and excellent detonation performance. Thus, the lowest eutectic mixture has a potential to replace molten cast TNT-based explosives, thereby meeting the demands of modern weapons and equipment.

An improved diffuse interface model is proposed to numerically simulate the interaction dynamics between solid explosive detonation and compressible inert materials. The chemical reaction of solid explosive detonation is simplified as the solid-phase reactant is converted into a gas-phase product. Thus, the mixture within a control volume is regarded to be composed of three kinds of components: solid-phase reactant, gas-phase product, and inert materials. Due to their differences in thermodynamic properties, three kinds of components can be thought to be in mechanical equilibrium and thermal nonequilibrium. The evolution equation for the volume fractions of all components is derived on the basis of the entropy production and pressure equality among the components. The evolution equation for the pressure of the mixture is also obtained and added to the diffuse interface model. Thus, the governing equations of the proposed diffuse interface model include the conservation equations for the mass of each component, the conservation equations for the momentum and total energy of the mixture, the evolution equation for the volume fraction of each component, and the evolution equation for the pressure of the mixture. The important characteristics of the proposed model are simultaneous consideration of mass transfer from the chemical reaction and heat exchange from thermal nonequilibrium and also direct calculation of the pressure from the governing equations. The proposed model owns thermodynamic consistency to effectively eliminate nonphysical oscillations near the material interface. Meanwhile, it can apply to arbitrary expressions of the equation of state, allow for any number of inert materials, and also treat large density ratios across the material interface.

In the present study, various test methods in the free field and confined explosions of cast HMX-based thermobaric explosives (TBX) and TNT are applied to quantify the explosion performance of TBX. The results show that the Mach reflection overpressure p and impulse I of TBX in the free field are much larger than those of TNT at the same relative distance from the explosion center. Based on the measured experimental data, semi-empirical formulas for calculating the overpressure at different distances from the TNT and TBX charges are derived. The fireball temperature and the duration of temperature higher than 1 500 ºC of TBX are seen to be significantly greater. The measured peak pressure of the two explosives blast in an explosion tank are compared with the values predicted by modified calculation models, and the results are in good agreement. In addition, the quasi-static pressure generated by TBX in the explosion tank is 30.9 % higher than that of TNT, which obviously reveals thermobaric effects of TBX. Based on the overpressure and quasi-static pressure calculation model, the TNT equivalents of TBX are calculated to correctly evaluate the TBX performance. The related contents in this paper will guide the formulation and performance assessment of TBX.

Results of experiments on loading flat samples of plasticized HMX by a shock wave are presented. Recording is carried out via an X-ray method in which X-ray is triggered by a sensor that responds to the onset of detonation in a sample. The time and place of the onset of detonation and the influence of the initial density of the sample on these parameters are determined. Experimental results are reproduced in finite element calculations. A dependence between the computational model parameters and the initial density of the sample is obtained.

An approximate theoretical analysis of a new method for testing explosive materials for sensitivity to mechanical stress, which is known as the crumbling shell method, has been carried out. In this non-impact method, the rupture of the shell releases the solid explosive material contained in it from the compressive load and allows it to free lateral expansion. In the process of high-speed flow, the substance explodes if the compressive stress is created large enough. The picture of the explosion as a whole seems to be similar to the phenomenon of initiation of an explosion when a charge of a solid explosive material is destroyed by an impact on a pile driver. Therefore, for the mathematical description of the test procedure under consideration, a previously developed model of the radial flow of a viscoplastic explosive material, its dissipative heating and thermal ignition in hot spots of the fluid is partially used. The data obtained on the change in various parameters during the initiation of an explosion make it possible to visualize its course not only within the framework of the method under consideration, but also to generalize them to explosion-like processes in a variety of materials that are suddenly released from a high load.

The reasons for the appearance of unstable large and small waves in the joint zone during explosion welding are investigated. Such waves arise when there are regions on the projected plate with even a small (10 ÷ 16 %), but abrupt (stepwise) change in thickness in the form of grooves obtained by machining. Unstable waves in the vicinity of the steps are formed only in the case when the width of the groove is greater than the thickness of the projectile plate. If the grooves are made on a fixed plate, then unstable waves do not arise. Analysis of the experimental data shows that the size of the waves generated in the bimetal in the vicinity of the steps on the thrown plate is affected by a sharp change in the impact angle associated with the bending of the plate at the places of the steps.

In view of rapid digitalization in the mining business, the authors highlight some associate problems. The definition of a digital twin is explained, and the difference of a digital twin of a solid mineral deposit from the other digital twins in the industry is described. The key function of a digital twin of a mineral deposit consists in updating of the deposit representation and in the use of the updated data in reasoned decision-making concerning mining development. A digital twin is formed using a set of automation tools. The mining and geological information system MINEFRAME integrates and structures the geology and geotechnology data a solid mineral mining in a unified digital space and, thereby, generates a mining plan based on the actual geological information. The methods of geological and geotechnical modeling, including digital twins, enable enhancement of occupational safety and optimization of mining strategy.

The article presents the studies into accumulation, distribution patterns and concentration conditions of radioactive elements in natural coal. The distribution patterns of radioactive elements in coal as function of its grade are also found. The application range of radiation properties of coal and barren rocks is substantiated for identifying the coal-barren rocks interface in longwall top coal caving with gravity coal flow to AFC. The working capacity of the nuclear geophysics method with metallic shielding of a responsive indicator is proved experimentally.

Every year, hundreds of forest fires occur on the territory of the Siberia. It is established that in recent decades there has been an increase in the number and area of forest fires, respectively, the volume of pyrogenic emissions increases too. During fires gas-aerosol emissions are released the volume of which is determined by the intensity of the fire and the burnt forest combustible materials. The paper presents calculations of greenhouse gas emissions from fires in light coniferous forests of the Lower Angara region for 2014-2019. Using data on the amount of forest combustible materials burned in a fire, the mass of greenhouse gases released during fires is calculated, depending on the type of fire, the type of forest and weather conditions that affect the drying of combustible materials., The estimated greenhouse gas emission from fires in light coniferous forests ranges from 5.9 to 37.5 ton/ha, depending on the type of fire and the type of forest. Each year, in the light coniferous forests of the Lower Angara region, greenhouse gas emissions from fires vary from 160 to 5649 thousand tons, on average more than 2300 thousand ton/ha per year. In total, during the period under review, according to the calculated data, more than 16 million tons of greenhouse gases were released during forest fires, with a predominance of CO-CO₂. It is revealed that unfavorable conditions of dispersion of emissions from forest fires are formed in the summer months, characterized by a high frequency of calm, surface inversions and radiation fogs. Relatively favorable weather conditions in the presence of pollution factors for self-cleaning the atmosphere from fire emissions are observed in spring and autumn, when the greatest number of windy days is recorded.

Eutrophic peat(y) (Hypereutric Sapric Histosols) pyrogenic soils on the hammock and hollow of phytogenic microrelief were studied 20 years after a large fire in the swamp spruce forest ( Picea obovata Ledeb.) of the eastern macroslope of the Kuznetsk Alatau. Currently, the burned area occupied by dense shrub-sedge-green moss birch forest ( Betula pubescens Ehrh.). Pyrogenic peat soils (mechanical and chemical underburning), differentiated by elements (groups) of the microrelief, are characterized by a pronounced intra-group spatial heterogeneity of physical and chemical properties ( C_V 21-39 %). However, according to the average indicators of most characteristics, except for moisture of peat, the soils of hammock and hollow do not significantly differ from each other. The content of ash substances is in the range of 52.5-53.5 %, carbon - 20.4-21.2 %, the bulk density is 0.29-0.31 g/cm³, the moisture of peat soil bulk is 49-60.8 %, the soil reaction is mainly slightly alkaline. The process of passive smoldering (below the ignition point) of a peat deposit is accompanied by an additional loss of carbon, which was calculated directly from the element using a natural experiment before and after the fire. The loss value is characterized by high variability ( C_V 34-42 %) due to a variety of thermal effects caused by environmental factors and fire features. Lower level of carbon loss and its weak mosaicity have been objectively identified for the hammock relative to the hollow. Additional carbon loss - limit, average (standard deviation) is: in pyrogenic soils of hammock 1.4-4.4, 2.98 ± 1.05, in the hollow - 0.4-5.7, 3.71 ± 1.57 kg/m². On average, this corresponds to 33.5 t/ha in the burned area, which is equivalent to 122.9 t/ha of CO₂ released into the atmosphere. The intensity of carbon losses in the process of passive smoldering is approximately 3-4 times lower compared to the burning of a peat deposit.

The problem of forest fires in the Far East has always been very acute. The forest fund of the Far Eastern Federal District (Far Eastern Federal District) as a whole is characterized by a high fire hazard and burnability due to the predominance of coniferous species and the complex composition of stands, the presence of various ecosystems and communities, including harems and meadow phytocenoses, as well as a number of geomorphological and climatic features. High classes of natural fire danger cause a greater probability of fires compared to the rest of the Russian Federation. At the same time, the most significant reserves of wood, which is one of the most valuable components of the Far Eastern export, are concentrated here. The article analyzes the dynamics of the area and number of forest fires, as well as the loss of wood on the root for the period from 2009 to 2020 in the Russian Far East, summarizes the reasons for the aggravation of the forest fire situation in recent years and provides general recommendations for reducing its intensity. The results of the study show significant fluctuations in the area and number of forest fires in different periods with an increase in 2016-2020. The average annual area of forest fires in the Far Eastern Federal District is about 2.5 million hectares per year. Over a 12-year period, the annual loss of wood stock is 10.5 million m³. The most affected regions are the Republics of Sakha (Yakutia) and of Buryatia, the Amur Oblast. The causes of fires, both in 1973-2004, and now mainly remain anthropogenic factors. In the zone of cedar-broad-leaved forests, 93 % of forest fires are caused by humans. The solution to the problem of forest burning is not simple and unambiguous and combines a whole set of measures necessary for adoption at the federal and regional levels.

The changes in the physico-chemical parameters of Scotch pine Pinus sylvestris L. wood were studied at an early stage of a fungal infection development in it using the methods of IR-Fourier spectroscopy and scanning electron microscopy (SEM). Analysis of SEM-images of locally damaged wood showed the presence of hyphae both in the intercellular space and in the lumens of single tracheids. From the comparison of the results of analyses of damaged and healthy wood, a number of parameters of the IR spectra were established - a change in the ratio of the absorption intensity at characteristic frequencies (wave numbers, cm^-1) for polymers of wood substance (hemicellulose, cellulose, lignin) and fungi (chitin and glucans) I _1512/898, I _1512/1157, I _1512/894, I _1647/1551, I _1695/1533, I _1620/1564, which allows identifying the presence and degree of exposure to fungal infection on wood. A new version of the assessment of changes in the structure of the wood substance is presented, which consists in a comparative analysis of the second derivatives of the IR absorption spectra of sound and damaged wood. The method significantly improves not only the visualization of changes in the spectra, but also allows to more accurately determine the «addresses» of the impact of a fungal infection on the wood substance by the intensity and frequency of the absorption bands. In addition, it can be used to monitor the appearance of nitrogen-containing compounds because of the presence of fungi. The implemented methodological techniques indicate the possibility of using radial cores in the work for the purpose of conducting their conjugate analysis, «linking» the results of IR-Fourier spectroscopy to the parameters of the annual rings and, in general, to chronologies, as well as correlating them with the morphological and anatomical structure of the annual ring and individual tracheids according to scanning electron microscopy data. The proposed approach to the diagnosis of wood damage at an early stage of the development of a fungal infection is effective, rapid and does not require complex sample preparation

Urban environment contains a broad variety of factors and this is where all living organisms are exposed to heavy stresses. Green plant serve as a natural «air filters» and are among the first to respond to negative changes of growth conditions. Crowns are the tree parts first to respond to negative changes of growth conditions by growing thinner, partially defoliated, and leaves’ (needles’) becoming heavily damaged. We presented the 1999 and 2020 inventories of the woody species of Central Park. Our analysis of the inventory results for species composition revealed thirty three species of trees and shrubs, seven conifer and twenty six deciduous. Judging by the condition of the crowns, the health of the majority of the park trees was poor to very poor. Among deciduous, ash-leaved maple Acer negundo L., balsam poplar Populus balsamifera L., aspen Populus tremula L. and Chinese elm Ulmus parvifolia Jacq. exhibited the poorest health. Tree health has improved, as compared to 1999, due to appropriate treatments and planting of young individuals. We also studied species compositions of invertebrate woody plant feeders and pathogenic fungi. We found that the amount of dust accumulated on the leaves of the trees in the park for a short rainless period was 8.6 to 9.8 times that of a background stand. In 2020, dust precipitated on leaves was 1.6 - 3.4 times less than in 1999. Dust accumulating capability of trees is much dependent on weather conditions. We used the results obtained to word our suggestions for improving the green spaces of the park.

For the key part of the territory of the Sayano-Shushensky Biosphere Reserve, located in the West Sayan mountains, the results of assessing the current state of natural stands of the Siberian stone pine Pinus sibirica Du Tour and its renewal under the canopy of the mother forests for the period from 1984 to 2015 are presented. Based on remote sensing data, cartographic materials of forest inventory and forest planning, their statistical processing and geoinformation analysis, the regularities of the spatial placement of the Siberian stone pine forests and the Siberian larch Larix sibirica forests with a mixture of the Siberian stone pine were revealed in the basin of the Sanzu River (Khemchik mountain ridge). The description and comparison of the main forest inventory characteristics of the Siberian stone pine from the position of the main and secondary species in the composition of the stands is given. It is noted that the process of regeneration under the forest canopy for different high-altitude belts and types of forest does not proceed in the same way. However, the trend of changing the breed in the forest is also obvious: cedar replaces larch and expands the boundaries of potential growth. It is established that the Siberian stone pine retains a stable position and has even expanded the area of domination over the past 30 years both at the upper and lower limits of growth. This is confirmed by the cartographic materials and tables provided. The priority of the environmental-forming functions of mountain the Siberian stone pine forests over forest-raw is justified.

Forest ecosystems play an essential role in climate stabilization, and the study of their capabilities in this aspect is of paramount importance. On the other hand, the current climatic shifts cause changes in their biological productivity, which, in turn, affects the biosphere function of forests. The study of the relationship between the biomass of trees and stands and hydrothermal indicators, in particular temperature and precipitation, is carried out mainly at the local or regional levels, often for indicators that are depersonalized by age, morphostructure of the forest, and also without taking into account the species composition. How climate changes affect the biomass of trees in transcontinental gradients is unknown today. The objective of this study was (a) to verify the operation of the law of the limiting factor at the transcontinental level when modeling changes in the biomass of trees of forest-forming species of Eurasia in relation to geographically determined indicators of temperatures and precipitation, and (b) to test the possibility of using the constructed climate-conditioned models of tree biomass in predicting temporal changes in tree biomass based on the principle of space-for-time substitution. As a result of the implementation of the principles of the limiting factor and space-for-time substitution, a common pattern has been established for the main tree species (genera): in sufficiently moisture-rich climatic zones, an increase in temperature by 1 °C with a constant amount of precipitation causes an increase in aboveground biomass, and in non-deficient zones - its decrease; in warm climatic zones, a decrease in precipitation by 100 mm at a constant average temperature in January causes a decrease in aboveground biomass, and in cold climatic zones - its increase.

A critical analysis is provided for the article: D. N. Klevtsov, O. N. Tyukavina Uglerododeponiruyushchaya sposobnost’ nadzemnoy fitomassy kul’tur sosny obyknovennoy (Pinus sylvestris L.) srednetaezhnogo lesnogo rayona (Carbon-depleting ability of aboveground phytomass in Scotch pine ( Pinus sylvestris L.) plantations of medium-taiga area) // Vestn. KrasGAU (Bull. Krasnoyarsk St. Agr. Univ.). 2018. N. 6 (141). P. 221-224 (in Russian with English title, summary and references).