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The paper presents the results of experimental studies of scenarios of diffusion combustion of a microjet of hydrogen flowing out of a cylindrical micronozzle with a diameter of 200 μm. The hydrogen microjet is ignited near the nozzle exit and at a distance. The experimental data are compared with the data previously obtained, and the results are expressed in dimensionless parameters (in terms of Reynolds numbers). It is established that the stabilization of flame during the outflow of a circular micro jet of hydrogen is associated with the presence of heating of the nozzle by a spherical flame region covering the nozzle section. The hysteresis of the diffusion combustion process of circular hydrogen microjets is shown depending on the ignition location of the microjet (near or far from the nozzle exit) and the change in the flow rate (growth or decrease).

Experimental data on the diffusion combustion of a round hydrogen microjet in a concurrent coaxial flow are presented. The effects on the combustion of a concurrent air flow and an air flow premixed with nanopowder of TiO2 are of interest. The hydrogen microjet emanates from a round micronozzle, which is surrounded by a coaxial slit to produce the concurrent flow. Combustion events found in these conditions are similar to those observed in the previous studies on the diffusion combustion of hydrogen microjets at subsonic and supersonic velocities. In a subsonic range, the so-called “bottleneck-flame region” is generated close to the nozzle exit, while in high-speed conditions, the flame separates from the nozzle. At increasing velocity of both the hydrogen microjet and the concurrent flow, the “bottleneck-flame region” is still found and the combustion becomes more intense. The “bottleneck-flame region” is suppressed at the microjet velocity approaching transonic values.

This paper presents experimental data on the effect of inert (He, N2, Ar, CO2) and reactive (СН4, O2, CF3Br, (CH3O)3PO) gas additives to hydrogen and ambient air on flame blow-off during diffusion combustion of a hydrogen microjet emanating from a micronozzle into air. It is found that the addition of the above gases to hydrogen narrows the microjet velocity range of stable combustion of hydrogen. For hydrogen with the additives studied, the critical velocity of flame blow-off depends primarily on the mean molecular weight of the combustible mixture. When the gases are added to the air surrounding the diffusion flame, the critical velocity of flame blow-off is determined by their inhibiting effect on the chemical reactions of hydrogen oxidation. The results can be used to determine the minimum concentrations of flame-suppressing additives required to prevent the ignition and combustion of hydrogen in its accidental releases.

In this paper the results of experimental studies of the combustion of a round microjet of hydrogen in a ring subsonic coaxial air jet are presented. It is shown that the combustion scenario for a subsonic hydrogen jet outflow is associated with the presence of a “bottleneck flame region” and nozzle heating, but the initial spherical shape of the flame region is transformed into a cylindrical one. It was found that the combustion of a round microjet of hydrogen in a satellite ring coaxial air jet at a supersonic outflow velocity is accompanied by the presence of supersonic cells.

The paper describes how the acoustic impact on an impinging jet induces a maldistribution in the radial velocity field within the nearwall zone of spreading jet. The r.m.s. velocity pulsation level in the nearwall jet is lower than in the natural jet. A higher length of the laminar flow zone in a microjet was noted. The development of sinusoid-type instability facilitates a higher combustion efficiency for a propane-butane fuel mixture in the impinging microjet; this reduces the soot emission. The tests demonstrated that the zero acoustic impact makes the flame spectrum more yellow (including the flame from the nearwall zone). This testifies about deficiency of oxidizer (air) and soot presence in the combustion products. The combustion efficiency for diffusive flame in the impinging jet depends on the nozzle diameter and nozzle-target distance.

The results of experimental investigations of the features of diffusion combustion during the interaction of a round supersonic microjet of air in the center and a coaxial (coflowing ring) jet of hydrogen. Such combustion is accompanied by a number of new phenomena: the formation of a cone-shaped flame near the nozzle сutoff, the locking of the combustion region in this cone, the presence of small-scale supersonic cells in the resulting flow, and the formation of laminar sections and their turbulization.

The experimental research results on diffusion combustion of a round hydrogen microjet flowing from a slit micronozzle at subsonic and supersonic speeds are presented. For the first time, four scenarios of diffusion combustion of a round hydrogen microjet have been identified, including supersonic combustion in the presence of supersonic cells both in air and in hydrogen. It has been found that flame stabilization for a subsonic microjet velocity of hydrogen is associated with the presence of a “bottleneck flame region” leading to the nozzle choking phenomenon, and flame stabilization for a supersonic microjet flow is associated with the presence of supersonic cells. A hysteresis of the diffusion combustion process of a plane microjet of hydrogen is found depending on the method of ignition of the microjet (near or far from the nozzle exit) and the direction of change in the rate of its outflow (growth or decrease).

The hydrogeochemical features of river water in different parts of Kamchatka Peninsula have been identified in terms of a wide (57) range of macro- and microelements by quantitative analysis methods—mass-spectrometry and atomic-emission analysis with inductively coupled plasma. Relatively high concentrations of chemical elements are typical of water that forms near active volcanoes of the Northern group in the peninsula and on Kamchatka Western coast in the territory with the least thickness of the soil-pyroclastic mantle. River water hydrochemistry is poorest in regions of the southeastern coast of the peninsula, where soil surface horizons overlay young, poorly transformed volcanic ash and, as an exception for Kamchatka as a whole, a positive geochemical correlation was found to exist between water and the total soil chemistry. General features of water hydrochemistry in Kamchatka include generally low concentrations of chemical elements compared with river water Clarkes; a high iron content of waters in all parts of the peninsula; a general absence of a correlation between the qualitative elemental composition of waters with the composition of the upper part of the soil-pyroclastic mantle.

The link of the chemical composition of the plant with the active volcanism of Kamchatka, is determined by the stable occurrence into the composition of the priority chemical elements for plants, volcanic ashes and soils: Ca, Mg, Mn, P, Cu, Zn and Sr. An elevated geochemical background of Kamchatka plants relative to the bulk chemical composition of the peninsula’s soils was established. The contents of Br, Hg, Hf, Sb, Ga, W, K relative to the clarks for living matter in the plants of the region are exceeded by 3–5 times. Against the background of small variations in the contents of chemical elements in plants of different regions, the relatively rich biogeochemical background of the Western region of the southern province (the western coast of Kamchatka) is determined, where most ancient near-surface volcanic ashes for Kamchatka are transformed into humus-accumulative horizons. On the territory of young volcanic ash fallout in the immediate vicinity of volcanoes, the relative richness of vegetation with chemical elements and the poverty of soils by mobile forms of elements have been established. On the contrary, at a distance from the volcanoes in the zone of far transfer fallout ashes, there is a marked relative poverty of plants and soil richness of available chemical elements.

The relationship between the chemical composition of plants and the active volcanism of Kamchatka is determined by the fact that the dominant chemical elements for the plants, volcanic ashes, and soils are invariably Ca, Mg, Mn, P, Cu, Zn, and Sr. We have found an increased geochemical background for Kamchatka plants relative to the bulk chemical composition of the soils in the peninsula. The concentrations of Br, Hg, Hf, Sb, Ga, W, and K relative to the clarkes in living matter were higher by factors of 3 to 5 in the plants of this region. While the concentrations of chemical elements in plants of different areas are subject to little variation, we found a relatively rich biogeochemical background in the Western Area of Southern Province (the western coast of Kamchatka); in this area the oldest (for Kamchatka) near-surface volcanic ashes have been transformed into accumulative humus horizons. It was found for the area where young volcanic ashes were deposited in the proximity of active volcanoes that the vegetation is relatively rich in chemical elements and the soils are depleted in mobile forms of elements. Farther from the volcanoes, however, in the zone where ashes of remote origin were deposited, one notes a comparative depletion in the plants and an enrichment in the soils in relation to accessible elements.

In this paper, we presented the results of experimental studies of the diffusion combustion of a plain hydrogen microjet flowing from a slit micronozzle at subsonic and supersonic speeds. For the first time, four scenarios of diffusion combustion of a plain hydrogen microjet including supersonic combustion in the presence of supersonic cells in both air and hydrogen are presented. The stabilization of the subsonic combustion of a hydrogen microjet was established to be due to the presence of a «bottleneck flame region» while the stabilization of the supersonic combustion of a microjet was found to be associated with the presence of supersonic cells. The observed hyster­esis of diffusion combustion of a plain hydrogen microjet depends on both the method of igniting the microjet (near or far from the nozzle exit) and the direction of change in the rate of its outflow (growth or reduction).

Volcanic soils of Kamchatka have the low contents of most the chemical elements in relation to their overall prevalence in the soils of continents and volcanic soils of Europe. Relatively increased gross contents of elements typical for volcanic rocks of medium and basic composition: Na, Ca, Mg, Cd, Mn, Co, Cu, and steadily low contents of elements characteristic of acid volcanics: La, Ce, Pr, Nd, Nb, Hf, Tl, Rb and Th, is most characteristic of the soils of different areas of the peninsula. The existing in the past and currently observed different conditions of volcanism in the previously allocated soil areas of Kamchatka determine the diversity of the chemical composition of the soils in these territories.

The Kamchatka volcanic soils have low concentrations of most chemical elements relative to their general abundances in continental soils and in European volcanic soils. The soils in different areas over the peninsula most typically involve higher bulk compositions of the elements that are typical of intermediate and basic volcanic rocks: Na, Ca, Mg, Cd, Mn, Co, and Cu, and persistently lower concentrations of the elements that are characteristic for acidic volcanic rocks: La, Ce, Pr, Nd, Nb, Hf, Tl, Rb, and Th. The diversity in the chemical composition of soils in the soil areas of Kamchatka as identified previously is controlled by the different conditions of volcanism that have existed in these areas in the past that also are observed at present.

Common geochemical features of volcanic near-surface ashes of Kamchatka (ashes located under the surface organogenic soil horizons) are their depletion by most chemical elements in comparison with average indicators for volcanic rocks of corresponding composition and relative enrichment of a limited range of elements, mainly typomorphic for main rocks (P, Mg V, Cr, Cu, Zn, Zr, Sb). Against the background of small variations in the contents of chemical elements in the ashes of different areas of the peninsula, the range of their priority elements is determined by their petrochemical composition. The active activity of the Northern group of volcanoes of Kamchatka causes a relatively high content of mobile forms of elements in the near-surface ashes of the Northern province in comparison with the ashes of the southern part of the peninsula.

The common geochemical features of Kamchatka near-surface ashes (ashes that underlie surface organogenic soil horizons) include their depletion in most chemical elements compared with the average figures for volcanic rocks of the same composition and their relative enrichment in a narrow range of elements, mostly those which are typomorphic for basic rocks (Р, Mg, V, Cr, Cu, Zn, Zr, and Sb). Viewed upon the background of small variations in the concentrations of chemical elements in ashes from different areas in the peninsula, the range of their dominant elements is controlled by their petrochemical composition. The vigorous activity of Kamchatka’s Northern Group of Volcanoes has produced relatively higher concentrations of mobile forms of elements in the near-surface ashes of the Northern Province compared with the ashes found in the southern part of the peninsula.

In this paper, we presented the results of experimental studies of the diffusion combustion of a plain hydrogen microjet flowing from a slit micronozzle at subsonic and supersonic speeds. For the first time, four scenarios of diffusion combustion of a plain hydrogen microjet including supersonic combustion in the presence of supersonic cells in both air and hydrogen are presented. The stabilization of the subsonic combustion of a hydrogen microjet was established to be due to the presence of a «bottleneck flame region» while the stabilization of the supersonic combustion of a microjet was found to be associated with the presence of supersonic cells. The observed hyster­esis of diffusion combustion of a plain hydrogen microjet depends on both the method of igniting the microjet (near or far from the nozzle exit) and the direction of change in the rate of its outflow (growth or reduction).

The possibility of state estimation for a dynamic system with nonlinearities in the equations of dynamics and measurements using the Singular Transformations Method is discussed. The features of the proposed approach application are considered. For a methodological example, the equations for the required estimates are specified and the estimation accuracy analysis is carried out.

The paper discusses the possibility of increasing the efficiency of the Kalman type filters for nonlinearities in the dynamics and measurement equations by using a special finite-difference equation to choose the linearization point. The simulation results of navigation data processing problem illustrate the effectiveness of the proposed approach

The effect addition of inert (He, N2, Ar, CO2) and reacting (СН4, O2, CF3Br, (CH3O)PO) gases in a hydrogen or in coflowing air stream on lift-off diffusion flame conditions of hydrogen micro jet effluxed from the round micro nozzle was experimentally studied. Using the schlieren technique a critical hydrogen flow rate was established at which the flame of the hydrogen microjet detaches from the nozzle when introducing additives of the studied gases into both air and hydrogen. It has been established that the addition of all the studied gases to the hydrogen leads to a decrease in the velocity range of its microjet at which flame stabilization is possible, regardless of whether the gases introduced into hydrogen are inert or reactive. It is shown that in the case of the addition of various gases to the hydrogen, the main factor determining the critical flow rate at flame lift-off from the micro nozzle is the average molecular weight of the H2 gas mixture with additives. At addition of the studied gases into the coflowing air, the critical flow rate of H2 is determined by their affect on the chemical reactions of hydrogen oxidation (inhibition effectiveness), as well as by a decrease in oxygen concentration due to dilution of air by additives. The data obtained are of interest to hydrogen energy in terms of determining the limits of sustainable combustion of the hydrogen microjet, as well as determining the minimum phlegmatizing concentrations of additives of inhibitors and fire suppressant in the air, preventing the ignition and explosion of hydrogen in case of emergency at its leak.

Results of experimental studies of the round hydrogen microjet interaction with a coaxial air for supersonic speed jets efflux are presented in this work. It is shown that interaction of round and coaxial air jets at their supersonic efflux leads to appearance of a train small/large-scale and, on the contrary, large/small-scale supersonic cells on a resultant jet with growth and reduction of speed of its efflux, respectively. It is found that the result of the round and coaxial air jets interaction at their supersonic efflux does not depend on geometrical parameters of a round and coaxial exit nozzle.

Experimental data on the phenomenon of nozzle choking at diffusion combustion of a high-speed hydrogen microjet at its ignition close to the nozzle are presented. As is found, such a phenomenon is due to the nozzle heating by the «bottleneck flame region» which is generated at the origin of microjet. This flow region persists up to transonic velocities of the microjet preventing from cooling of the nozzle and the transition to supersonic speed. In the case of hydrogen ignition far from the nozzle exit in supersonic conditions, the «bottleneck flame region» is suppressed, the flame becomes detached from the nozzle which is no longer heated so that the supersonic range is attained. The subsonic combustion of hydrogen microjet is stabilized by the «bottleneck flame region» while the supersonic one becomes more stable at the generation of shock cells. The results of the present study provide new details on the combustion of hydrogen microjets and could by useful for the operation of different burners.

Results of experimental studies of features of the round hydrogen microjet combustion in a coaxial air jet are presented in this work. It is shown that the combustion scenario is connected with existence of the «bottleneck flame region». This fact correlates with the similar scenarios of the diffusion hydrogen microjet combustion at subsonic efflux velocity investigated by us earlier. It is revealed that the spherical shape of the “bottleneck flame region” is transformed to a cylindrical shape. It is found that the round hydrogen microjet combustion in a coaxial air jet at supersonic efflux velocity is accompanied by existence of supersonic cells both in a hydrogen microjet and in a wake of coaxial air jet. Round hydrogen microjet supersonic combustion in a coaxial air jet is connected with a flame separation from a nozzle exit.

Results of experimental studies of the round air microjet interaction with a coaxial hydrogen jet at its combustion for supersonic speed jets efflux are presented in this work. It is revealed that combustion of the coaxial hydrogen jet with growth of its speed efflux is accompanied by all scenarios, observed at study of the round and plane hydrogen microjets diffusion combustion. However, “bottleneck flame region” undergoes considerable geometrical deformations because of specifics of a flame of a coaxial jet. It is shown that “bottleneck flame region” is transformed from Y-shaped to spherical shape in the activity of growth of a coaxial jet speed efflux. It is found that a round air microjet interaction with a coaxial hydrogen jet at its combustion is accompanied by several new phenomena: existence of cone-shaped area a coaxial jet combustion near a nozzle exit; existence of small-scale supersonic cells on a resultant flame; absence of the hydrogen combustion efflux from combustion region of a coaxial jet near nozzle exit; flame-out from combustion region of a coaxial jet near nozzle exit that leads to hydrogen ignition downstream, its intensive combustion and sharp acoustic noise occurrence; existence of a turbulent flame, to its separation from a nozzle exit and transition to supersonic combustion of a resultant jet.

Results of the experimental studies of a round hydrogen microjet combustion in a coaxinal jet of air and SiO2 nanopouder mixture efflux from a slot-hole (multinozzle) coaxial nozzle at subsonic and supersonic efflux velocity are presented. It is shown that scenarios of a hydrogen microjet combustion in a coaxinal jet of air and nanopouder mixture are similar to scenarios of diffusion combustion of a hydrogen microjet at subsonic and supersonic efflux velocity. Existence of “bottleneck flame region” is revealed at subsonic and a flame separation from a nozzle exit at supersonic efflux velocity. It is found that with efflux velocity growth of jets it is possible to observe intensification of the luminescence of the flame at the boundary between the jet of hydrogen and air / nanopowder mixture and existence of «bottleneck flame region» as in a laminar coaxial jet and in a flame of a hydrogen microjet combustion. On the other hand, it is possible to observe actually disappearance of the «bottleneck flame region» at approach to transonic efflux velocity.

The data processing problem in attitude and heading reference system based on two units of micromechanical gyroscopes is considered as a special class of information processing problems from two measurement sources. A novel algorithm used for processing the measurements data from two units of micromechanical gyroscopes is proposed, which can improve orientation system performance while reducing the requirements for external sensors. A mathematical error model of micromechanical gyroscopes and orientation system is given, considering the rotation of the measurement units, and the advantages of the proposed method is analyzed in comparison with other algorithms.

The results of experimental investigations of the micronozzle-chocking phenomenon under diffusion combustion of a hydrogen microjet at a high outflow velocity in the case of ignition of hydrogen near the nozzle cut are presented. It is found that the cause of micronozzle chocking is the heating of the nozzle walls from the flame-neck region retained up to transonic velocities and preventing nozzle cooling and the passage of the hydrogen jet to the supersonic-flow velocity. It is shown that hydrogen ignition far from the nozzle cut with a developed hydrogen supersonic flow into the flooded space leads to the disappearance of the flameneck region, flame detachment from the nozzle cut, and, correspondingly, termination of the nozzle heating and the possibility of the microjet coming out at the supersonic-flow velocity for the hydrogen jet. It is established that the flame-neck region is a stabilizing factor for the subsonic combustion of a hydrogen microjet up to transonic velocities. In the second case, the presence of supersonic cells stabilizes the supersonic diffusion combustion of the hydrogen microjet.

The article presents qualitative data on the study of the process of diffusion combustion during the outflow of a gas jet from a nozzle apparatus with a certain arrangement of nozzles. The nozzle apparatus is a round nozzle with a straight channel and a coaxially located annular slot. In the experiments, hydrogen or methane was supplied through an annular slot, and the air was supplied through a central circular micro nozzle. The main features of the diffusion combustion of hydrogen and methane during the outflow from the nozzle apparatus are revealed and a qualitative comparison of the processes is carried out. In both cases, at the initial stage, laminar combustion is observed near the nozzle exit and a breakthrough of the flame front occurs with the release of an incombustible mixture of combustible gas and air. At a high flow rate, the flame separates from the nozzle exit. The fundamental difference is that hydrogen exhibits significantly better combustion stabilization characteristics at the nozzle exit.

The objective of this work is an experimental study of the influence of initial and boundary conditions at the nozzle exit upon diffusion combustion of a hydrogen microjet. It is found that the initial mean velocity profile and the presence (or absence) of a material with large heat capacity surrounding the nozzle exit may have a pronounced effect on the flame structure and combustion of the round hydrogen microjet. The rates of fuel consumption (i.e., the efflux velocities of hydrogen) providing diffusion combustion of the round hydrogen microjet, the flame detachment, and the origination of the «bottleneck flame» in the cases of a top-hat and a parabolic mean velocity profiles at the nozzle exit are determined. The variations of the extent of «bottleneck flame» with the hydrogen flow rate are made clear. Also we examine the diminution of the extent of «bottleneck flame» with the growth of hydrogen flow rate in three cases of initial conditions at the nozzle exit.

It has been revealed that changes in the chemical composition of soils after the input of volcanic ash under conditions of a cold humid climate depend on granulometric and lithogeochemical compositions of eruption products, the ways and forms of the input of chemical elements to soil, the period of the year, and weather conditions at ash falls. The lithogeochemical composition of ash mainly determines the type of change in the total composition of soils. Variations in the contents of mobile forms of elements depend mainly on the period of year and meteorological conditions during ash falls. Most mobile compounds (99.3%) of many elements are transported to soil upon ash falls not as components of ash particles, but in gas- and watersoluble forms directly from the dispersion medium of the volcanic aerosol. The following regularities were revealed in soils at a distance of 25 km from the centers of eruption: (i) the increase in the total contents of elements and the removal of their mobile forms in winter and (ii) the accumulation of mobile compounds, a drop in their total compounds, and soil acidification with a significant (about 1.5 times) decrease in the degree of base saturation of soils in summer.

Experimental data are presented on the effect of inert (He, N2, Ar, CO2) and reactive (SH4, O2, CF3Br, (CH3O)3PO) gas additives to hydrogen flow and ambient air on flame separation during diffusion combustion of a hydrogen microjet emanating from a round micronozzle into air. The micronozzle is a stainless steel tube with an inner diameter of 0.5 mm, a length of 30 mm, and a wall thickness of 0.1 mm. The shadow method is used to determine the critical hydrogen velocity at which the flame of the hydrogen microjet separates from the nozzle upon injection of additives into air and into the hydrogen flow. It is found that the addition of the above gases to hydrogen narrows the microjet velocity range in which stabilization of the flame can be achieved with injection of both inert and reactive additives. For the hydrogen flow with the additives studied, the critical velocity of flame separation from the micronozzle depends primarily on the mean molecular weight of the gas mixture. In the case of the addition of the gases to the air surrounding the diffusion flame, the critical velocity of flame separation is determined by their effect on the chemical reactions of hydrogen oxidation (inhibiting effect) and by the reduction of oxygen concentration due to air dilution with the additive. The results could be of interest to experts in hydrogen energetics for determining the conditions of stable hydrogen microjet combustion and the minimum concentrations of flame-suppressing additives to air preventing the ignition and combustion of hydrogen after its accidental release.

The problem of methods application for decentralized processing of information in case of nonlinear polynomial algorithms implementation in individual measurement modules is considered. Recursive algorithms of polynomial filtering are proposed as an example of processing the calculated coordinates, inertial system readings, and measured distances to two responder beacons. The results of simulation of a centralized scheme of measurements processing and the scheme based on the federated filtering algorithms are presented.

In the second part of the present study, experimental results on the round and plane hydrogen microjets diffusion combustion at various nozzle diameter depending on microjet velocity are shown. Of special interest is the contribution to the combustion process of the so-called «bottleneck flame» region which is observed at diffusion combustion of hydrogen both in the round and plane microjets. The «bottleneck flame» appears as a spherical closed volume of laminar combustion at mixing of the hydrogen microjet with ambient air. This spherical volume is surrounded by a narrow layer of density gradient overcoming which the laminar microjet and its flame become turbulent. A diminution of the «bottleneck flame» with growth of the microjet velocity is revealed.

In the first part of this study, experimental (hot–wire and visualization) results on the effect of transverse acoustic oscillations on characteristics of round and plane air microjets at low Reynolds numbers and on their propane and hydrogen combustion are presented. In both cases, the transverse acoustic excitation results in the flame bifurcation. A phenomenon observed at the nozzle exit is the so-called «bottleneck flame». This is found both at acoustic excitation and without it at combustion of hydrogen. More details on this phenomenon are given in the second part of the study titled as: “Features of diffusion combustion of hydrogen in round and plane high-speed microjets (Part II)”.

This study is devoted to experimental investigation of hydrogen-combustion modes and the structure of a diffusion flame formed at a high-velocity efflux of hydrogen in air through round apertures of various diameters. The efflux-velocity range of the hydrogen jet and the diameters of nozzle apertures at which the flame is divided in two zones with laminar and turbulent flow are found. The zone with the laminar flow is a stabilizer of combustion of the flame as a whole, and in the zone with the turbulent flow the intense mixing of fuel with an oxidizer takes place. Combustion in these two zones can occur independently from each other, but the steadiest mode is observed only at the existence of the flame in the laminar-flow zone. The knowledge obtained makes it possible to understand more deeply the features of modes of microjet combustion of hydrogen promising for various combustion devices.

It is found that the overwhelming majority of mobile forms of the chemical elements (up to 99%) that are thought to produce favorable effects when they arrive with volcanic ash to soils and supply additional elements that enhance the bioproductivity of ecosystems do not come in the form of ash particles, but in a gas-dissolved form directly from volcanic aerosol. Volcanic ash when considered independently of volcanic eruptions does not contain considerable amounts of accessible forms of chemical elements that would enable us to consider them as sources of nutrient elements for living organisms. However, the extensive range of elements that are contained in ash in ratios that are necessary for effective life activities invests these elements with catalytic properties that regulate the nutrient regime of plants and that can be used in agriculture in combination with lower amounts of traditional fertilizers to produce substantial (up to 72%) yield increases and to improve the quality of agricultural products.

The geochemical features of volcanic soils (Andosols) in the northern soil province of Kamchatka are identified. The background regional concentrations (Cbr) of most of chemical elements in the studied soils are lower than their average concentrations in soils of the world and in the European volcanic soils. Only Na, Ca, and Mg are present in elevated concentrations in all the studied soils in the north of Kamchatka. Regional background concentrations of elements are exceeded by 1.6 times in the area of active ashfalls of the Tolbachik volcano and by 1.3 times in the area of active ashfalls of the Shiveluch volcano. The concentrations of mobile forms of elements in these areas exceed their regional background concentrations by 2.1 and 2.6 times, respectively.