Home – Home – Jornals – Chemistry for Sustainable Development 2014 number 1

Regularities of the formation of Alpine flora of the Badzhal Mountain Range were described related to the specifics of natural and climatic conditions and history of development of the region.

Mycorrhizal symbiosis between plant roots and mycorrhizal fungi are almost ubiquitous. These interactions contribute a largely to soil autotrophic respiration (R_A), influence soil heterotrophic respiration (R_H) and respond strongly to such climatic changes as temperature and precipitation. The aim of the present study was to explore how variation of temperature and precipitation influence R_A and R_H in global forest ecosystems that are classified by the mycorrhizal type of the dominant plants. The results show slight variation for R_A and significant change for R_H among different mycorrhizal strategy types. In forests with predominating arbuscular mycorrhiza (AM) the R_A and R_H are trifling higher than in non-AM type forests. The responses of R_A and R_H to temperature and precipitation were highly variable among different mycorrhizal strategies. For example, the changes of R_A and R_H are more dependent on precipitation than temperature in AM-forest, and temperature accounted more for their variations in forests of the other three mycorrhizal types. As far as we know, this study was the first to evaluate the influence of different mycorrhizal strategies on forest R_AA and R_H and their response to temperature and precipitation.

Eighty species of macromycete were detected as the result of studying the biota of agaricoid and gasteroid fungi growing in dryad tundras of Altai-Sayan mountain area; 19 of them were first to be found in South Siberia. The basis of microbiota comprised species of arctoalpine element (37,5 % of the total number of species) and multizonal element (22,5 %) of families Russulaceae, Cortinariaceae, Strophariaceae and genera Cortinarius, Inocybe, Russula. On the trophic level mycorrhiza-formers (22,5 % of the total number of species) and humic saprotrophs (17,5 %) predominated.

Species composition and evolution dynamics of cyanobacteriae and algae of Lake Kalatch (Omsk region) were studied. The studied cyanobateriae and algae proved to be highly abundant and had little floristic affinity to phytoplankton. Small-celled cyanobacteriae and Chlorococcales predominated. The term “cryophyton” was suggested to describe photosynthetic organisms living in the ice.

The article presents the results of investigation of genetic diversity, structure and the degree of differentiation of “island” Scotch pine populations ( Pinus sylvestris L.), growing on the territory of South Siberia (south of Krasnoyarskiy krai, Khakasia, Tuva, Buryatia) and in the north-eastern part of Mongolia. Twenty isoenzyme loci had been analyzed to obtain the given results.

Investigation of phenotypical variety of cones and seeds in southern Siberian Scots pine populations (Krasnoyarskiy krai, Khakassia, Tuva, Buryatia) was carried out using the methods of A. I. Vidyakin [2004]. The analysis was conducted on the basis of 5 index features and 6 qualitative features. The populational level of 7 features was confirmed. These features also proved appropriate to be used as markers of genetic variability of southern Siberian Scots pine populations.

The link between productivity of aboveground and underground biomass and variability of electrophoretic spectra of seeds polypeptides was established on the basis of the analysis of 6 populations of a valuable medicinal species – Hedysarum theinum Krasnob. The protocols for microclonal propagation of perspective samples were developed. The most efficient multiplication was achieved in MS medium supplemented with 5 µM BAP, 200 mg/l of glutathione and 200 mg/l of casein hydrolyzate. The shoots were successfully rooted on half strength MS basal medium supplemented with 7 µM NAA.

During the vegetational seasons in 1976-2005 respiration and growth of vegetative organs of model Scots pine trees at the climax stage of their current increment in forest steppe of Baikal area were studied. The study of respiration was based on the strong connection between respiration of vegetative organs, its growth and temperature. Respiration rate was measured using area-based and oven-dry weight estimation. Regardless of the basis of the study, vegetative organs respiration rate decreased from apical meristems in the direction of the organs’ base. The relation between respiration of above- and underground organs appeared to be 3 : 2 and almost 2 : 1 respectively. During the period of study the Scots pine respiration rate increased approximately by two; average area-based respiration rate amounted to 32,8 and 36,9 kg of CO₂ respectively.

Differences in winter dormancy depth of Scots pine in provenance trials were revealed during the analysis of zero level of fluorescence parameters and chlorophylls and abscisic acid content. Obtained results correspond with the data received from the study of morphological features of needles and phenological observations. Trees of southern climatype, which differ in morphological features of needles and speed of phenophase transition, have deeper winter dormancy compared to the northern climatype. Due to climatic changes, trees of northern climatypes are expected to be more vulnerable during the periods of winter-spring thaws which previously were not typical for northern regions.

The article presents the analysis of seasonal, intra- and interpopulation variations in bioactive substances content in leaves of Nitraria sibirica Pall. Different areas in the south of West Siberian Plain and Altay-Sayan mountain region were taken into consideration.

It was proved that dwarf apple trees descended from tall-growing forms. This presumption was justified by comparative analysis of morphological features, ITS1 sequence identity and presence of genetic streams between the studied forms. It was also suggested that formation of dwarf forms in the present case is the initial phase of ecological speciation. Wide scatter of F_st values in different loci among the studied groups, ecologically mediated selection against hybrids and parallel formation of dwarf forms of apple trees all attest to this supposition.

The affect of temperatures and soil pollution by fluorides on the early growth stages of Crepis tectorum from polluted and unpolluted habitats was studied experimentally. The character and degree of combined influence of pollution and temperature; different directions of rebound depending on temperature, the studied index and origin of the population; variations in phenotypic flexibility in connection with temperature in polluted habitats were discussed.

The effect of SO₂ on the chain reaction of hydrogen oxidation in the autoignition region (T = 470–510 ^oC and p < 200 torr) is studied. In the absence of SO₂ under flow conditions, the process occurs in a low-temperature flame mode with a characteristic pale blue glow. With the addition of sulfur dioxide, SO₂ is transformed to elemental sulfur and a new phenomenon is observed. At a small contact time (less than 4–5 s), the process enters the mode of intermittent flames. Dependences of the rate and intensity of light flashes on pressure, temperature, and contact time are studied. An interpretation of the observed phenomenon is given.

A kinetic mechanism for combustion of hydrogen azide (HN₃) comprising 61 reactions and 14 flame species (H₂, H, N, NH, NH₂, NNH, NH₃, HN₃, N₃, N₂H₂, N ₂H₃, N₂H₄, N₂, and Ar) was developed and tested. The CHEMKIN software was used to calculate the flame speed at a pressure of 50 torr in mixtures of HN₃ with various diluents (N₂ and Ar), as well as the self-ignition parameters of HN₃ (temperature and pressure) at a fixed ignition delay. The modeling results of the flame structure of HN₃/N₂ mixtures show that at a 25–100% concentration of HN₃ in the mixture, the maximum temperature in the flame front is 25–940 K higher than the adiabatic temperature of the combustible mixture. Analysis of the mechanism shows that burning velocity of a HN₃/N₂ mixture at a pressure of 50 torr is described by the Zel'dovich–Frank-Kamenetskii theory under the assumption that the burn rate controlling reaction is HN₃ + M = N2 + NH + M (M = HN₃) provided that its rate constant is determined at a superadiabatic flame temperature. The developed mechanism can be used to describe the combustion and thermal decomposition of systems containing HN₃.

Specific features of the unsteady flame in a microchannel with a controlled wall temperature are theoretically studied within the framework of a one-dimensional diffusion-thermal model. The case with the channel wall temperature increasing in the gas flow direction and the channel size being smaller than the critical value determined on the basis of the ambient temperature is considered. Depending on the flow rate of the combustible mixture of gases through the channel, either flame stabilization or alternation of flame repetitive extinction/ignition is possible. The influence of the characteristic length of channel wall heating on the domains of existence of various combustion modes is studied for the first time. The theoretical study shows that there exists a critical value of the temperature gradient in the channel walls, below which the regime of flame repetitive extinction/ignition is no longer observed. At small values of the temperature gradient, a hysteresis phenomenon is found, which is associated with different changes in the flame position in the cases with increasing and decreasing flow rates of the gas.

In this paper, the effect of the flame holder geometry on the flame structure of a mixed hydrogen–hydrocarbon fuel is numerically studied. The fuels used in this study are 100% H₂, 50% H₂ + 50% CH₄, and 100% CH₄. Numerical results obtained by using the κ–ε and β-PDF models show good agreement with experimental data. The results show that increasing both the flame holder length and hydrogen percentage in the fuel decreases the flame length. The flame temperature decreases with decreasing flame holder length. Adding hydrogen to methane increases the peak temperature of the flame and moves its location toward the burner inlet. It is observed that the dependence of the flame length as a function of the flame holder diameter has a minimum at a certain value of the latter. The flame temperature is higher for smaller flame lengths.

External manifestations of the heterogeneous combustion front are characterized. Gas-dynamic aspects of the phenomenon are considered, and experimental data on the change of combustion modes during natural filtering of an air mixture are analyzed. Results of an investigation of the bifrontal structure of the combustion zone in a horizontal plane layer during convective gas transfer are presented.

Combustion of ammonium perchlorate (20–90%) mixtures with ferrocene is studied. It is demonstrated that, depending on the ratio of the components in the examined compositions, in addition to the usual gas-phase combustion model, another possible combustion mechanism exists. A somewhat unusual condensed-phase (c-phase) model may be realized, in which the heat-generating reaction occurs in a foam/aerosol layer at the temperature of evaporation of the less volatile component, which the surface temperature is defined by evaporation of the more volatile component. The efficiency of ferrocene depends on the propellant combustion mechanism: in systems that obey the gas-phase combustion mechanism, the influence of ferrocene addition is higher than the influence of addition of a hydrocarbon fuel; in systems with the c-phase mechanism of combustion, ferrocene addition produces a significant effect. Depending on the ratio of the components, ferrocene first acts in these compositions simply as a highly reactive fuel; it is only in fuel-enriched compositions with a high equivalence ratio that the burning rate increases owing to catalysis of the combustion process by the ferric oxide on the soot skeleton.

The effects of the particle size of powder components, the relative density of the sample, and the degree of dilution of the mixture by thermally inert materials on the pore structure of self-propagating high-temperature synthesis products obtained in the combustion process involving melt were experimentally studied using the (Ti + 26% Si)–Al₂O₃ system as an example. Special techniques of quantitative metallographic analysis allowing for the analysis of materials with complex pore space structure were used.

It is found that the main factors determining the synthesis parameters of tungsten carbide by mechanically stimulated thermal explosion are the structure of carbon modifications and the degree of their aromaticity. The prospects of using carbon modifications obtained from plant raw materials for the synthesis of tungsten carbide with a low content of sulfur are discussed.

Physical and chemical processes of gasoline combustion in internal combustion engines are considered. A model of combustion evolution in gasoline-driven engines, which explains some specific features of the processes in internal combustion engines, is proposed.

Experimental studies were performed to investigate the dependence of the laminar flame velocity in dust clouds of Al, Mg, Zr, Fe, and B particles on the physicochemical parameters (fuel concentration and composition, particle size distribution) and hydrodynamic conditions of the combustion process (semi-open tubes, free clouds of particle–air mixtures). Heat conduction was found to make a predominant contribution to the overall heat transfer in the combustion wave. The main causes of instability of laminar flames (acoustic disturbances, interfacial exchange, forced and natural convections), transient phenomena, and vibrational and turbulent combustion of dust were studied experimentally.

A reduced two-stage model of detonation combustion of methane in oxygen and air for equimolar and fuel-lean mixtures is proposed. One-dimensional structures of the detonation wave are calculated for different ratios of the fuel and oxidizer corresponding to the overdriven and Chapman–Jouguet regimes. A comparison of the calculated dependences of the detonation velocity on the methane concentration in the methane–air mixture with available published data reveals their reasonable agreement.

Results of measurements and processing of sizes, energy, and power of radiation of a cloud formed after an explosion of 50/50 TNT/RDX and TNT cast charges with masses ranging from 0.01 kg to 1000 tons on the ground surface and at different heights in air are presented; the measurements and data processing are performed within wide temporal (up to 10 s/kg^1/3) and spectral (up to 28 m m) intervals. The results are compared with available published data. These explosives have the maximum radiative characteristics owing to the high content of carbon in explosion products. Under conditions of explosions in air, the measured emitted energy approaches 50% of the explosion energy. In the case of ground explosions, the radiation is anisotropic because of screening by ejected soil, and the ratio of energies emitted upward and along the ground surface can exceed the order of magnitude.

A numerical simulation of the initiation of PETN by a laser pulse was performed. The heat-conduction equation was solved in a cylindrical coordinate system taking into account multiple reflection of the light beam, zero-order exothermic reaction, and melting. A criterion for the ignition of explosives by a laser pulse with multiple reflection of the light flow was obtained. The calculation results are in satisfactory agreement with experiment and the ignition criterion. Dependence of the critical energy density on the light beam radius is due to radial heat transfer. The ignition threshold can be controlled by changing the reflection coefficient of the back surface of the sample.

The explosion of PETN of density 1.73 g/cm³ was first initiated by the second-harmonic pulse of a Q-switched neodymium laser. It is shown that the primary process of energy absorption in this case is PETN molecule ionization involving two-photon absorption. The critical initiation energy density corresponding to a 50-% probability of explosion is 12.3 J/cm².

A new method for determining the dynamic friction coefficient of explosives is presented. The method combines the physical model of friction sensitivity with theoretical analysis and numerical calculations. Experimental measurements of the dynamic friction coefficient of steel indicate that the proposed method is effective, provides secure and reliable data, and can be used to calculate the dynamic friction coefficient between cyclonite (RDX) and steel.

Various mechanochemical approaches to improving the sorption properties of metal materials accumulating hydrogen are discussed. Some experimental results illustrating the possibilities of each approach are presented. It is established that the sorption characteristics of known metal accumulators of hydrogen can be improved by affecting their structure, morphology and surface properties with the help of the mechanical activation and mechanical alloying with various kinds of additives. The possibility to search for new hydrogen-absorbing materials through the mechanochemical synthesis of metastable composites of components of various natures including thermodynamically immiscible components was demonstrated. These composites may possess a high reactivity with respect to hydrogen and serve as precursors for the synthesis of new phases. The synthesis of intermetallic compounds and hydride phases directly during the mechanochemical treatment also opens opportunities for the preparation of new materials promising for hydrogen storage.

Synthesis method is based on grinding coarse aluminium powder in the planetary centrifugal mill in the presence of a surface-active organic substance that promotes a decrease in the size of aluminium particles and covers the resulting products with a film that is impermeable for oxygen. The synthesis is carried out in the flow of high-purity nitrogen. At a temperature of 300–400 °C, the organic film is evaporated from the precursor particles, aluminium surface, active toward nitriding, shows up, and the reaction takes place at a temperature of about 750 °C. The yield of the product is about 100 %, its oxygen content is less than 0.6 mass % (the detection limit for the method used). Because of low temperatures, the resulting powder is weakly agglomerated; particle size varies within the range 350–500 nm.

The products of the joint mechanical activation of kaolinite with polymers (Sevilen, poly-N-vinylpyrrolidone and polyamide PA-6) in a high-energy ball mill were studied by means of IR spectroscopy and X-ray phase analysis. It was established that for definite polymer content of the initial mixture the mechanochemical interaction of kaolinite with polymer occurs, and the chemical bond is formed between them.

Mechanocomposites composed of tungsten and zirconiums interacting with the former according to the equilibrium diagram of states were studied. The composition, structure and morphology of the samples obtained at the stages of mechanical activation are considered. The effect of the introduction of organic compounds into W/Zr mechanocomposites is studied.

Mechanical milling is widely used for the purpose of efficient mixing of the components of particle-reinforced composite materials, which are further obtained in a bulk form by consolidation of the milled powder mixtures. Using the Ti₃SiC₂–Cu system as an example of a metal matrix composite with a ductile matrix and a reinforcement phase prone to chemical interaction with the matrix at elevated temperatures, we show that the effect of the preliminary mechanical milling of the components is seen not only in the uniformity of distribution of the reinforcing particles in the matrix but also in the consolidation behavior of the powders. The influence of the presence of composite agglomerates in the milled mixture on the processes induced by heating during consolidation is demonstrated by detonation spraying of the mechanically milled and mixed Ti₃SiC₂–Cu powders in comparative experiments and Spark Plasma Sintering of the Ti₃SiC₂–Cu agglomerates of different morphology. Interparticle interactions that are affected by the presence/absence of composite agglomerates and their morphology are the interfacial chemical reactions, the degree of transformation and melting of the copper matrix in the contact regions.

Glauconite and glauconite sand were used as starting materials. To prepare adsorbents on the ground of glauconite, mixtures of glauconite sand and sodium dihydrophosphate NaH2PO4 at various weight ratios (1 : 1, 2 : 1, 3 : 1, 4 : 1) were subjected to the mechanical activation (MA) in a planetary mill. MA products were studied by methods of X-ray phase and thermal analysis. Degrees of sorption for ions of manganese, cuprum, nickel and zinc were determined from appropriate solutions of sulphates within the concentration range of 60–1000 mg/L.

Thermal decomposition of the samples of cold-weather storage bitumen (heating with water vapour) was studied by means of thermogravimetric analysis. Bitumen was treated to remove water according to the regulations and with higher temperature and treatment time than those stated in the regulations. The effect of mechanically activated mineral additive and the additive imitating pyrobitumen on thermolysis was considered. Calculated activation energies of thermal decomposition of bitumen samples are reported.

Radiation-thermal synthesis of ferrite Ni_0.75Zn_0.25Fe₂O_4. was investigated. Comparative analysis of the reactivity of mechanically activated mixtures obtained from commercial oxides and from metal nanooxides was carried out. It was shown that the formation of mechanocomposite was necessary for the efficient reaction.

Single-phase superfine LiCo_1–yFe_yPO₄ solid solutions were synthesized with the use of a mechanochemically stimulated carbothermal reduction of iron and cobalt oxides throughout the entire range of 0 ≤ y ≤ 1. The mechanical activation was carried out using an AGO-2 planetary mill. According to the scanning electron microscopy, the average primary particle size of the samples synthesized ranges within 200–250 nm. According to the XRD phase analysis, all the samples crystallize in the orthorhombic system, with space group Pnma. The volume of the unit cell increases with increasing the content of iron in samples. According to Mцssbauer (NGR) spectroscopy, all iron ions are in the oxidation state 2+ in an octahedral environment typical for olivine. Electrochemical properties of Li_{1 – y}Fe_yPO₄ were investigated by means of galvanostatic cycling. It has been demonstrated that with the increase of Fe content a marked shift in the potential of the Co²⁺/Co³⁺ pair toward lower voltage values occurs, whereas the potential of the Fe²⁺/Fe³⁺ pair remains almost unchanged.

A solid-phase waste-free and energy-saving synthesis with the use of mechanical activation of single-phase cathode material Na₂FePO₄F (sp. gr. Pbcn) for sodium and lithium accumulator has been implemented. It has been demonstrated that the product is formed already at the stage of mechanical activation (MA) and is crystallized in the course of subsequent annealing up to 600 °С, whereas heating up to 700 °С results in decomposing the product formed to give Na₃PO₄, Fe₃O₄, Na_0.11FeF₃ and Na₃Fe₂(PO₄)₃. Electrochemical properties of Na2FePO4F have been studied in a cell with a lithium anode and lithium electrolyte. According to results of the studies the specific capacity of Na2FePO4F surface-modified with carbon is equal to 115 mA ⋅ h/g at a rate of cycling amounting to C/10. It has been found that the process of chemical and electrochemical replacing Li by Na in the structure of Na2FePO4F is completed by the formation of a compound with the composition NaLiFePO4F (sp. gr. Pbcn).

Lithium γ–monoaluminate was obtained as a result of mechanochemical activation of the mixture of lithium carbonate and aluminium hydroxide in AGO-2 planetary activator, followed by the thermal treatment. The effect of mixture composition and humidity on the phase composition and specific surface of lithium γ–monoaluminate was studied. It was shown that in the variation of the composition and humidity of the mixture the specific surface area of the final product decreases significantly (from 13 to 0.2 m²/g).

The anomalous effect of graphite on the degree of wear of copper milling bodies was studied quantitatively. It was shown that mechanical activation of the system diamond–graphite–silicon with copper milling bodies led to the formation of copper-containing semi-products and stable coatings on the surface of milling bodies.

The temperature anomalies and long-term depressions of ozone in the stratosphere observed after large-scale volcanic eruptions are poorly explained from the point of view of modern ideas about composition of the stratospheric aerosol of the volcanogenic nature. However, such post-volcanic phenomena could occur in case when the aerosol comp its surface. The basic opportunity of forming nanosized carbon aerosol (less than 0.1 μm in size) in the stratosphere in case of powerful Plinian type volcanic eruptions is shown in the paper. Estimates of the amount and lifetime of these particles allow explaining long-term temperature anomalies and the ozone depression in the stratosphere after volcanogenic perturbations.