Express assessment of air quality in several settlements of Eastern Eurasia based on the results of snow geochemical studies

Parshin Alexander Vadimovich ORCID: 0000-0003-3733-2140 PhD in Geology and Mineralogy Director; Institute of Siberian School of Geosciences; Irkutsk National Research Technical University Senior Researcher; Institute of Geochemistry SB RAS 3 Akademika Kurchatov str., Irkutsk, Sverdlovsk region, 664074, Russia sarhin@geo.istu.edu Other publications by this author     Cherednichenko Aleksandr Evgen'evich Student; Institute of Siberian School of Geosciences; Irkutsk National Research Technical University 3 Akademika Kurchatov str., Irkutsk, Sverdlovsk region, 664074, Russia ssg@geo.istu.edu Goryachev Ivan Nikolaevich Head of the Department of Ore Geology; Siberian School of Geosciences; Irkutsk National Research Technical University 3 Akademika Kurchatov str., Irkutsk, Sverdlovsk region, 664074, Russia ivan.goryachev@geo.istu.edu Ikramov Zieviddin Lutfiddin ugli Postgraduate student; Institute of Siberian School of Geosciences; Irkutsk National Research Technical University 3 Akademika Kurchatov str., Irkutsk, Sverdlovsk region, 664074, Russia ziyoviddin.ikramov1992@gmail.com Trusova Valentina Valer'evna PhD in Technical Science Senior Researcher; Siberian School of Geosciences; Irkutsk National Research Technical University Senior Researcher; Vinogradov Institute of Geochemistry SB RAS 3 Akademika Kurchatov str., Irkutsk, Sverdlovsk region, 664074, Russia vvtrusova@gmail.com Kurina Anastasiya Vladimirovna Research Engineer; Siberian School of Geosciences; Irkutsk National Research Technical University 3 Akademika Kurchatov str., Irkutsk, Sverdlovsk region, 664074, Russia kurinanaya@geo.istu.edu

Kachor Ol'ga Leonidovna Doctor of Technical Science Head of the Department of Geoecology; Siberian School of Geosciences; Irkutsk National Research Technical University 3 Akademika Kurchatov str., Irkutsk, Sverdlovsk region, 664074, Russia olgakachor@geo.istu.edu

1. Introduction

The study of the state and possible pollution of atmospheric air is one of the most important components of environmental quality management systems and forecasting of its changes ^[1]. Such studies are carried out as part of engineering and geological surveys, assessment of the background state of the natural environment of new sites, as part of fundamental and exploratory scientific research, as part of ensuring the technospheric safety of industries, in the search for mineral deposits, and in many other cases. Currently, a widespread variant of atmogeochemical geoecological studies is maximum-one-time, daily or seasonal measurements carried out at stationary posts or mobile stations, in which air is pumped through filters or through automatic gas analyzers using special equipment and concentrations of various indicators are measured in units of concentrations or the number of particles attributed to the volume of air (mcg/^m3, mg/^dm3). The result becomes available in in situ mode, or after air is pumped through the filters, the residue on them is examined in the laboratory. This approach underlies the monitoring systems of atmospheric air quality in many countries of the world and the recommendations of the World Health Association ^{[2, 3, 4]}. Within the framework of national and international air pollutants rationing systems, appropriate standards of maximum permissible exposure or sanitary standards have been developed, including a set of controlled parameters and their permissible and limit values. ^{[5, 6, 7, 8]}. Depending on the atmospheric air control program (complete, incomplete, or abbreviated), the main and specific pollutants are recorded. The main ones include suspended solids, carbon and nitrogen oxides, sulfur dioxide, benz(a)pyrene, and formaldehyde; depending on the industrial infrastructure of a locality, ammonia, hydrogen sulfide, chlorine, phenol, and heavy metals may be specific. The stationary version of monitoring systems makes it possible to effectively carry out systematic monitoring of the state of atmospheric air near already known sources of impacts, while such sources are naturally located within economically developed areas where there is electricity, roads, buildings and structures in which equipment can be marked. Maximum one-time or daily mobile complexes allow either to carry out an assessment of atmospheric pollution "here and now", or to react in some other way (for example, organoleptically) to the fact of what is happening at the moment, but has not yet been completed pollution. Such complexes can be relatively mobile.

Both described variants of atmogeochemical studies have a number of disadvantages. Thus, the maximum one-time assessment does not allow us to record the facts and the degree of significance of processes that are not taking place at the moment. Thus, a wide variety of errors can be made, for example, omitting significant but intermittent impacts, or, conversely, mistaking a man-made anomaly for the background state of the atmosphere. In addition, to perform comprehensive studies of a significant number of indicators, it is necessary to use a significant amount of equipment and complexity, which is problematic to deliver to hard-to-reach areas, for example, by light helicopter and easily damaged during off-road transportation. Research requires a highly qualified specialist and all-terrain vehicles to transport equipment and provide its power supply. Stationary observation systems, which make it possible to record changes in the state of the atmosphere over a long period of time and thus minimize the risks of missing significant but short-term impacts, cannot be used in areas remote from infrastructure, for example, when assessing the background state of the environment in the framework of projects of prospecting and exploration of mineral deposits, since it is impossible in practice to ensure their autonomous operation in a remote area without any infrastructure or people. At the same time, the current level of attitude to issues of geoecology and environmental protection requires a reliable assessment of the background conditions of atmospheric quality and their scientifically based monitoring not only at existing industrial facilities, but also at the first stages of economic development of new territories. For example, according to the new "Strategy for the development of the Mineral Resource Base of the Russian Federation until 2050", the environmental component becomes very important not only at the stage of field development, but also at the stage of prospecting and exploration, that is, when there are no roads, electricity, etc. on the site, in this case, even an instant assessment, not to mention Constant monitoring is extremely problematic to implement. The same applies to any infrastructure projects.

An effective solution to this problem is due to the fact that many of the new infrastructures or mining projects in the northern part of Eurasia are located in regions with long winters and stable snow cover, which will allow using the method of snow geochemical surveying to study and monitor air quality. Snow as a depositing medium absorbs a wide variety of pollutants, it lies for several months and therefore provides an informative assessment of the load as a whole, it can be studied for a large number of chemical, physical and mineralogical parameters, selection does not require complex equipment, and the spatial detail of research can be very high. In this regard, such a campaign is already widely used in scientific research. Its wider spread in the practice of environmental control is hindered by several factors, and the two most significant, according to the authors, are related to the fact that the above–mentioned rationing principles are tied to the volume of air per unit of time and therefore cannot be translated into snow samples, which are a combination of soluble forms of pollutants in snow water and solid residue - insoluble forms in in the form of dust. There are standards for a limited number of parameters (for example, dust load), as well as principles for calculating and classifying the degree of complex pollution ^[9]. However, these principles are based on a comparison of the detected concentrations of pollutants with their background atmospheric and geochemical parameters (anomaly contrast coefficients), which forms the second problem of snow and geochemical studies – fragmentary knowledge of remote geosystems in the northern territories, which often does not allow us to confidently judge the parameters of the geochemical background. In this case, standard approaches to snow geochemical studies form a number of problems, which, as well as their solutions, are the subject of this article. In general, this study is aimed at developing the theoretical basis of snow geochemical geoecological research systems as an important means of optimizing economic development of a significant area and a part of Russia rich in natural resources. The features of the atmospheric state in several areas with significantly different levels of economic activity, located in different landscape and morphological conditions in a significant area from the Ural Mountains to the Pacific Ocean, are studied and shown. The purpose of detailed characterization of the atmospheric and chemical situation in each region was not set: the work is aimed at studying the possible ranges of man-made and natural variability of concentrations of insoluble and soluble forms of pollutants in the air of industrial and background territories within the northeastern part of Eurasia, and at demonstrating typical atmogeochemical/snow geochemical situations according to the authors. In this work, the chemical composition of solid residue and snow water was studied and a comparative assessment of the median and maximum concentrations between several objects in the Urals, the Baikal Region, and Primorye was carried out, and the observed features of the snow and geochemical situation were analyzed. As a result, a completely non-exhaustive, but nevertheless quite reliable and, in the opinion of the authors, useful for a wide range of researchers, a basis for designing and interpreting the results of snow geochemical studies has been formed.

2. Objects and methods of research

First of all, the authors consider it necessary to comment on the choice of facilities and the amount of work on each of them, namely, to explain why different numbers of samples were taken in different areas (Fig. 1). The fact is that this study has strict time and personnel constraints, since the field part is implemented by first-year students of the IRNTU within the framework of basic educational disciplines for the accelerated formation of comprehensive practical competencies for them ^[10], and if we organize large-scale snow and geochemical studies that require a large amount of equipment in the Irkutsk region for their detailed study is quite realistic [11-13, etc.], then samples from the regions of the Urals and Primorye, as well as remote small villages of the Baikal region, students they are selected during the winter holidays completely independently, based on their available capabilities. In any case, within the framework of this study, a full cycle of snow and geochemical studies is carried out: a GIS project is being prepared for each area with the selection of a priori optimal points for studying the state of the atmosphere, samples of seasonal snow are taken from them, after which a standard cycle of laboratory preparation and chemical analysis of the samples obtained is carried out: melting, filtration, drying of filters with solid residue, weighing, chemical analysis. The students received the necessary tools, such as chemical ash-free filters, bags, shovels, etc. Depending on how far they live and which transport they use to return to the University, they had the opportunity either to carry out the entire sample preparation cycle at home and bring snow water and solid residue to the laboratory, or to bring bags of snow and process them at the Institute. After the chemical analysis data was improved, geostatistical processing was performed and tables and concentration diagrams were created, which are then publicly available on the geoportal. geo.istu.edu .

As a result, the objects of research in 2025 were:

- Part of the Sverdlovsky district of Irkutsk in the Akademgorodok district and the Universitetskiy microdistrict.

- The popular and actively built-up suburban cottage settlements of Nikolov Posad, Polet, Berezovy, Forrest Home, Rusy, Sergiev Posad, Novo-Irkutsky, Greenhill in the Irkutsk region, which themselves do not contain objects of negative impacts (except for possible furnace heating), but may be influenced by industry, energy, and transport.

- Several settlements significantly remote from Irkutsk as the main center of economic activity in the Baikal region, both theoretically background to the state of the atmosphere (Bokhan) and having a certain (mining) mono-industry (Cheremkhovo, Novonukutsky). In the first case, the state of the atmosphere should correspond to the regional background of the Baikal region, which is influenced only by global atmospheric transport processes (assuming that such a single background exists), in the second case, we should see the influence of the mining industry.

- In the western part of the Russian Federation, Chelyabinsk, a major center of metallurgy and mechanical engineering, has become an object of research with a priori high level of anthropogenic load. Four samples were taken here in areas adjacent to large industrial facilities as well as recreational areas (parks, cottage settlement).

- The facility in the eastern part of the Russian Federation is located in Primorye, this is the city of Spassk-Dalny (1 sample).

The general scheme of the research is shown in Figure 1.

Fig. 1. Objects of snow geochemical research: 1 - Chelyabinsk, 2 – Irkutsk and Irkutsk region, 3 – Cheremkhovo, 4 – Nukutsky district, 5 – Bokhan, 6 - Spassk-Dalny.

A catalog of more precise reference points of sampling is given in Table 1.:

Table 1. Snow sampling points in various regions of Eastern Eurasia

In all cases, sampling is carried out according to a standard procedure, taking into account the requirements of GOST R 70282-2022 "Environmental protection. Surface and groundwater. General requirements for ice and precipitation sampling". Samples were taken from open areas located at a distance from obvious sources of local impacts using plastic blades, then placed in plastic bags. The volume of snow collected was recorded (the depth of the snow cover and the area of the hole are measured).

The samples were analyzed in the Chemical Analytical Laboratory of the Siberian School of Geosciences, accredited in accordance with the established procedure in accordance with ISO/IEC 17025-2019. After snow melting and filtration of snow water, a chemical analysis of the solid residue on the filters and filtered meltwater was carried out. The volume of meltwater before filtration and the mass of the solid residue on the filters were also measured, the solid residue was dried at room temperature and weighed using Analytical XP204 laboratory scales with a sensitivity of ± 0.1 mg. The solid residue was analyzed by X-ray fluorescence analysis ^[14]. The snow water was analyzed using the ICP-AES method.

This paper considers the most common pollutants of the first and second hazard classes of substances entering the soil from emissions: As, Pb, Zn, Cu, Ni, and Fe. This choice of elements corresponds to the most common set of studies in the initial assessment of the background condition of subsurface areas before the start of their geological study, as a result of which the features of their accumulation in the snow cover of the northern territories, the most promising for the discovery of new mineral deposits, is an extremely urgent task for scientific and methodological support of preliminary and monitoring studies of the state of the atmosphere. Also, the behavior of these elements in comparison with macronutrients, gases, integrated dust load and other parameters controlled within the framework of standard monitoring programs described in the introductory part of the article is significantly less studied and described in the literature.

3. Results

The research results are presented in the form of tables and diagrams with estimates of the average and limiting parameters of the concentrations of each element and small cartograms for those areas where there are more than four or five samples, which makes it possible to compare different areas with each other and study the ranges of possible variability of atmospheric and biochemical parameters. Of course, these mathematical estimates are based on a statistically unrepresentative amount of data, but the purpose of the study is not to reasonably calculate reliable descriptive statistics for each studied area or locality, but primarily to study the possible ranges of variability of the studied parameters and their median values. To ensure this, samples were taken in characteristic (not random) locations of each studied area, and the authors hope that the discussions below will allow readers to agree that, at least at a semi-quantitative level, the data obtained allow us to draw fairly reliable conclusions about the features of the atmospheric chemistry of the studied areas, as well as some well-founded methodological comments.

3.1. Chelyabinsk

The city of Chelyabinsk is one of the anti-leaders of the Russian air pollution rating ^[15]. The high level of atmospheric pollution generated, among other things, by an electrometallurgical plant, a zinc plant, a pipe rolling plant and a metallurgical plant, as well as by enterprises of the energy industry in the city and district, has not been ignored by researchers, including using snow geochemical research methods ^{[16; 17; 18, 19 and others]}, however, the issues of Only one paper is devoted to the study of the chemical composition of the solid residue, and it does not provide quantitative data ^[20]. The chemical parameters of snow water were better studied by their predecessors ^{[18; 19; 21]}.

Table 2 presents the results of chemical analytical studies of solid residue and snow water.

Table 2. Concentrations of elements in the solid and liquid phases of snow in Chelyabinsk

As can be seen from the table, the solid residue of the snow cover is characterized by high concentrations and significant variability in the concentrations of the studied elements. It should be noted that even the minimum concentrations of iron are so high that they are beyond the upper limit of the range of determination of the analysis method used.

At the same time, soluble forms of pollutants are significantly less pronounced and are often below the sensitivity limit of the ICP-AES technique. Interestingly, iron and nickel appear to have virtually no water-soluble forms at all. Comparing the results obtained with the data ^[22] obtained for the Smolino Lake natural monument located in the southern part of the region, we can note the fundamental convergence of the data obtained for Pb, Zn and Cu. The concentrations of Cu and Pb found by us are on average two times lower, and Zn is 3 times higher, which apparently correctly reflects the features of atmospheric pollution in the central and southern parts of Chelyabinsk, however, it should be recognized that in this case, the study of snow water is less informative than solid residue.

Let's consider the geospatial features of atmospheric pollution. Figure 2 shows a diagram of the location of sampling points in Chelyabinsk.

Fig. 2. The layout of sampling points in Chelyabinsk

The southwestern sampling point for seasonal snow is located in the center of the Chelyabinsk Urban Forest, a relict pine forest with an area of 12 square kilometers, a natural monument of regional significance located in the western part of the city. The northern point is located next to the Chelyabinsk Metallurgical Combine, the largest enterprise in the Metallurgical district of the city, which produces a wide range of products: cast iron, rolled steel, semi–finished steel products made of carbon and special steel and corrosion-resistant steel. The eastern point is located in the Traktorozavodsky district, next to the Chelyabinsk Tractor Plant, which is also a priori a known source of anthropogenic impact. The fourth point, located between the second and third, was selected in the V.V. Tereshkova Children's Park, which is located in the city center next to Lenin Avenue.

Fig. 3. Schemes of pollutant concentrations in the solid residue of the Chelyabinsk snow cover

According to the data obtained, the cleanest area of the studied area is Tereshkova Park (the southwestern part of the site). The maximum concentrations of arsenic, lead, and zinc in the solid residue of the snow cover are located in the Metallurgical District (adjacent to the Chelyabinsk Metallurgical Plant). Concentrations of these elements are also high in the Traktorozavodsky district, and nickel and copper are maximally manifested here. But the highest concentration of copper was recorded in the children's park. Tereshkova is located in the city center, and concentrations of nickel and zinc are also quite high here.

However, when trying to move from such a qualitative interpretation of the level of "more here – less here" to an assessment of the degree of air pollution in the research area and a scientifically based characterization of the geoecological situation, we will encounter the problem of rationing the values indicated in the introductory part of the article. The fact is that the concentrations of pollutants in snow water and solid residue are not normalized either in Russia or in general world practice, as a result of which we cannot draw conclusions about air quality based on the data presented in Figure 2 and Table 2 (maps or concentration tables). In order to characterize the level of air pollution, current practice uses an approach based on assessing the degree of pollution of an area by several pollutants in total, for which a complex load indicator Zc is calculated ^{[21, 23, etc.]}:

Zc = ∑(Kci + ... + Kcn) — (n — 1), where:

· n is the number of definable summable substances;

· Kci is the concentration coefficient of the i—th chemical element, equal to the multiplicity of its excess content over the background value.;

· Kcn is the concentration coefficient of the nth chemical element.

This indicator is officially normalized in accordance with ^[24], as a result of which it can be used to justify decision-making on environmental quality or to compare the total degree of air pollution of several facilities with different composition of anthropogenic load. However, this approach is not a complete solution to the problem of the effective use of snow geochemical studies as a tool for scientific and especially regulatory-based environmental monitoring or assessment of air quality, since it is based on the calculation of contrast coefficients - the multiplicity of excess detected concentrations over the background value, which in turn must be determined in some scientifically sound way. or calculate it.

There are two main approaches used for this.:

- comparison with "background" points ^{[23; 25; 26; 27]} from areas where a priori there is no pollution, or with the corresponding MPC/ODC values;

- calculation methods, the most common of which is the assumption of the median value of pollutant concentrations for the geochemical background ^{[28; 29]}.

The second option is well applicable to natural geochemical environments in general, within which there are isolated significant man-made anomalies. The first option requires a good understanding of the regional geochemical situation, and it is of little use in poorly or fragmentally studied areas during the initial geoecological assessment. In addition, this approach is very unstable – with minor absolute changes in the values of the geochemical parameters of the background point (due to analytical errors, due to small local impacts in the area of the point, due to its selection in a slightly different location, etc.), the contrast coefficients can change significantly. Let's consider both options in relation to the received data.

In this case, the contrast coefficients of the anomalies relative to the median value for all elements are in the range of 1.2 – 2 times, that is, the contrast of the anomalies is low. However, the object under study is actually completely man-made, as a result of which the natural background cannot be found here by the method of median averaging, and in this way the average level of atmospheric pollution in the city will be determined (the materials given later in the article will show how significant it is), and this level will be taken as the background. If, however, the parameters of the point with the lowest detected concentrations of pollutants are forced to be taken as the natural state of the environment (especially since, according to the current requirements for environmental engineering ^[30], the point in the urban forest fully meets the criteria for the background), then the contrast coefficients will be much higher - from 1.5 for Cu to 12 for Ni. At the same time, it is obvious that if the background point had been located in a different place, the contrast coefficients, like the entire Zc indicator, would have taken on a completely different value. For example, in ^[21], which compared the level of atmospheric pollution in Chelyabinsk and Moscow, the maximum KC to the background points in both cities was 18, while the coordinates and chemical parameters of the background for neither Moscow nor Chelyabinsk were given.

According to the authors, the above case as a whole perfectly characterizes the entire complex of problems of introducing snow geochemical studies as an air-conditioned means of assessing air quality. Obviously, it is the well-known (e.g. from the literature) parameters of the local or regional background for different areas of the "winter" regions and for different components of the snow cover (water, solid residue) that would allow researchers to relate to the same background values, which would make it possible to bring the results of various studies into the same dimensions, effectively compare different areas based on the contrast of anomalies and complex load indicators, and provide comparative estimates of air quality.

This study is aimed at developing such a theoretical basis, for which we will further compare the above estimates of the average and ranges of variability of the chemical parameters of the components of the snow cover of Chelyabinsk with other regions and districts. This will allow a more reasonable assessment of the air quality in each of the studied locations, as well as create a certain basis for the territories that have not yet been studied.

3.2. Baikal region

Unlike the industrial areas of the southern Urals, the Baikal region belongs to the UNESCO World Natural Heritage Sites, as a result of which its natural ecosystems must remain in an unchanged state, and the Russian Federation is responsible for their preservation. In this regard, the issues of the natural geochemical background and the degree of excess over it in this region are of particular importance. However, both historically and currently, the region is experiencing serious impacts from various sources of economic activity – the mining and metallurgical industries, aircraft engineering, facilities of the fuel and energy complex, and a number of others. As a result, a number of cities and towns in the Irkutsk region, as well as industrial cities in the Urals, are regularly included in the list of settlements with the highest levels of ambient air pollution in Russia ^{[31; 33]}. At the same time, it is worth noting that due to the presence in Irkutsk of a large scientific center with several institutes of the Russian Academy of Sciences and two large universities conducting research in the fields of Earth and environmental sciences, the main large cities and towns are quite well studied geoecologically, including snow survey methods ^{[12; 13; 23; 25; 26; 27; 28; 32; 33; 34 and many others]}, although previously only soluble forms of pollutants were studied. Due to this, various authors use both their own and previously published background chemical parameters of snow water, and a computational approach is also used. At the same time, generalizing data have not yet been formed for the solid residue, and areas remote from the main industrial facilities have been studied only in fragments, as a result of which the geochemical parameters of their snow cover are often not established.

The districts of the Irkutsk region are further considered in the order of reducing the level of anthropogenic load – according to a priori concepts.

3.2.1. Irkutsk region

The city of Irkutsk and the surrounding settlements (Shelekhov, Angarsk) are regularly included in the anti-rating of air quality. In this study, we focused on suburban areas and cottage settlements (including those with prestigious expensive real estate), in which, unlike the central part of the city, undisturbed seasonal snow samples can be taken (Fig. 4).

Fig. 4. Snow sampling scheme in Irkutsk suburbs

It should be noted that these suburban areas are not necessarily far from known major sources of impacts. For example, Zone 1 borders the Irkutsk Oil and Fat Processing Plant and the Novo-Irkutskaya CHPP, and the Irkutsk Aluminum Plant is located a few kilometers southwest of zone 2, that is, significantly closer than the central part of the city.

As can be seen from Table 3, the concentrations of pollutants in the solid residue of snow cover in the suburbs of Irkutsk are several times lower than in Chelyabinsk, and the situation with snow water is more complicated.

Table 3. Concentrations of some pollutants in the solid residue of snow cover and snow water of the western suburbs of Irkutsk

Thus, the median concentrations of pollutants in the solid residue of the Irkutsk region snow cover are 1.5 (Cu) – 12 (Zn) times lower than in Chelyabinsk. The contrast coefficients for the median background are approximately the same as those recorded in Chelyabinsk (up to 2 times), but the KK relative to the minimum values is many times higher - from 9 (As) to more than 100 (Ni), the distribution of concentrations in cartographic form can be estimated from Fig. 5.

Fig. 5. Schemes of pollutant concentrations in the solid residue of the Irkutsk region snow cover

This can be explained by at least three positions: firstly, the recorded specific geochemical background of the Baikal region with low natural concentrations of a number of parameters, secondly, the high level of local impacts, and thirdly, the fact that in Chelyabinsk, we probably recorded and compared not with the true regional natural background, but still with a somewhat polluted state of the atmosphere. The first position will be verified further by comparing the data obtained with the results obtained in areas of the Baikal region with no industry. The second position is beyond doubt, since the research sites are located in a well-known technogenically loaded area. As for the third position, the existing level of research does not allow us to judge it reasonably – in most published works on snow and geochemical studies in Chelyabinsk, only soluble forms of pollutants were considered ^{[19, 22, etc.]}, the only study of insoluble forms known to the authors ^[20] does not contain primary results of chemical analytical studies, only their results are given. interpretation based on unspecified environmental regulations.

Using median estimates (and in this case the anomaly contrast coefficients are similar), the level of atmospheric pollution in Chelyabinsk and Irkutsk region should be recognized as approximately the same, which is obviously completely unfair in an ecological sense, based on the multiple concentrations of pollutants in the solid residue.

As for the soluble forms of pollutants, first of all, it should be noted that copper concentrations in the Irkutsk region are significantly more variable, while the minimum values here are below the ICP-AES detection limit, the maximum values are ten times higher than in Chelyabinsk, and the median is about twice as high. From this it can be concluded that the territory of Chelyabinsk is fairly evenly polluted with soluble forms of copper, while in the suburbs of Irkutsk pollution may be more serious, but local. The situation for lead and zinc in Irkutsk is more favorable, there are only isolated points with values that lie in the field of determining the methods of analysis, while the median is significantly below the limit (unlike Chelyabinsk). As a result, cartographic representations of the distribution of elements in snow water are not provided. The situation with water-soluble arsenic in Irkutsk is slightly better, with nickel slightly worse (based on the fact that the median value for the Irkutsk region is still determined at the quantitative level). The general observation is that the behavior of water-soluble forms does not correlate at all with the concentrations of pollutants in the solid phase, and also that in a clean atmosphere (apparently corresponding to the natural background of the Baikal region), the concentrations of pollutants in snow water apparently lie below the detection limit of inductively coupled plasma atomic emission spectrometry.

3.2.2. Cheremkhovo

Cheremkhovsky district is located 120 kilometers north of the regional center. It is the center of the mining (coal) industry, but there are no other significant sources of impact here, and the village itself is quite far removed from other large industrial centers.

In order to record both the background environmental parameters and the maximum anthropogenic load, four samples were taken on the territory of the city of Cheremkhovo itself, located in the Industrial District, central park and on the outskirts of the city, and two more in the nearby village of Alyokhino. The sampling scheme is shown in Fig. 6.

Fig. 6. Sampling scheme in Cheremkhovsky district of Irkutsk region

The results of chemical analytical studies are presented in tabular form in Table 4.

Table 4. Concentrations of some pollutants in the solid residue of snow cover and snow water of the Cheremkhovsky district of the Irkutsk region

As can be seen, the median values of the pollutants studied in the solid residue of the snow cover in the Cheremkhovsky district are 1.5 (Zn) – 8 (Cu) times lower than in the Irkutsk region, and 10 (As, Cu, Ni) – 30 (Zn) times lower than in Chelyabinsk. At the same time, the contrast ratio of anomalies in the median background ranges from 1.1 for Fe to 2 for Ni, that is, the average contrast of anomalies with this approach is comparable to both Irkutsk and Chelyabinsk. The minimum detected values of As, Pb, and Ni are similar to those recorded in the Irkutsk region (taking into account the XRF analysis margin of error of 10-15%). Based on this, it can be assumed that such values are close to the regional background. The minimum concentrations of iron in Cheremkhovo are about 30% lower, and copper, on the contrary, is almost twice as high, but the median values of these elements in Irkutsk are still significantly higher. Cartographic representations are shown in Figure 7.

Fig. 7. Schemes of pollutant concentrations in the solid residue of the snow cover of the Cheremkhovsky district

As for snow water, only Ni and Cu can be confidently determined in it, and the median concentrations of Cu in Cheremkhovo are similar to Irkutsk, and Ni is twice as low. A comparison of both regions of the Baikal region with the Urals for this component of the snow cover shows the different nature of the geochemical situation and at the same time indicates the need to study both components of the snow cover – both the solid and the soluble phases, since it is obviously impossible to characterize the atmogeochemical situation in a cartographic form based on the traditional approach to studying snow water in any of the studied areas.

3.2.3. Bohan

Bokhan is a small village located at the same distance from Irkutsk as Cheremkhovo (120 km), but on the other bank of the Angara River. It is located 60 km from Cheremkhovsky district in a straight line to the east, and directly downwind. There are no large industrial enterprises.

Two snow samples were taken in Bokhan (Fig. 8), and in one of them the amount of solid sediment was insufficient for X-ray fluorescence analysis.

Figure 8. Sampling scheme in the Bokhansky district of the Irkutsk region

The values of all elements in the snow water were below the ICP-AES detection limit. Thus, the geochemical parameters of the snow residue given in Table 5 relate to the only point located directly in the village on Komsomolskaya Street, while the second point, located in the cemetery area, and in the sense of being the background, remains impossible to characterize, which indicates that the geochemical parameters of snow in the Baikal region, They are not affected by anthropogenic influences, but are at a very low level.

Table 5. Concentrations of some pollutants in the solid residue of snow cover and snow water of the Bokhansky district of the Irkutsk region

When comparing the "urban" background of Bohan with Cheremkhovsky, it can be noted that the concentrations of zinc and copper are comparable, and the contents of the remaining elements in Bohan are many times lower. Consequently, the previously detected concentrations of As in ~8-9 ppm and Pb in 10-13 ppm are still not the regional background of the Baikal region and are at least 40-50% formed by anthropogenic impact. The situation with Ni is more stable. Apparently, in all the studied areas of the Irkutsk region, in the absence of anthropogenic influences, it should not be present in solid residue samples in measurable quantities.

3.2.4. The Novonukutsky district

The last studied area of the Baikal region is Novonukutsky. It is located even further from the largest industrial cluster facilities in the Baikal region (~200 km from Irkutsk to the north), however, the village itself has a gypsum quarry and a drywall factory. Figure 9 may give the mistaken impression that all the samples were taken outside the locality, but in fact three samples were taken in the center and on the outskirts of the Zarechny microdistrict, located less than a kilometer from the industrial facilities of the drywall plant.

Fig. 9. Sampling scheme in the Novonukutsky district of the Irkutsk region

Theoretically, open-pit mining can generate an increased dust load in the research area, however, there was very little solid sediment in the snow at all three sampling points (Table 6).

Table 6. Concentrations of some pollutants in the solid residue of snow cover and snow water of the Novonukutsky district of the Irkutsk region

Only the concentration of Zn was reliably determined in the snow water. The single concentrations of Cu, Ni, and Pb are lower than in other studied settlements of the Baikal region.

Thus, the results obtained are at first glance uninformative, but the insufficient volume of solid residue, which does not allow chemical analysis, for natural environments, can be noted as a steady trend. Replacing XRF analysis with more precision methods will not solve the chemical-analytical problem, since for acid decomposition during inductively coupled plasma spectrometric methods, the weight of the sample is also at least five grams. Therefore, in order to ensure successful snow and geochemical studies of potentially undisturbed areas, for example, within the framework of programs for preliminary assessment of the background of new geological exploration sites in the northern regions of the Irkutsk region and regions similar in natural conditions, it is necessary to provide for sampling of snow in the maximum possible volume – preferably more than 10 or even 20 kg.

3.3. Primorye

Man–made environmental pollution in the Far Eastern Federal District is formed by various sources of impacts - mining, road transport, facilities of the fuel and energy complex, the construction industry, metallurgy, military-industrial complex enterprises, and marine and railway transport ^{[35; 36]}. Due to the presence of research organizations of various specialization and departmental subordination, the quality of atmospheric air is not ignored, a significant number of researchers use a wide variety of methods, from modeling based on stationary observation systems to studies of micro–sized particles in flushes from plant needles ^[37-39]. As a result, the main large cities have been well studied, but small settlements and the background atmospheric and chemical parameters of geosystems have not been sufficiently studied ^[36].

The continental regions of Primorsky Krai are usually characterized by the precipitation of large amounts of snow, as a result of which the methods of snow geochemical surveying have significant potential here, however, the most important chemical parameters of the solid residue of the snow cover have apparently not been studied at all.

The Spassky district, located about 200 kilometers from Vladivostok to the north, was chosen as the object of this study. The city of Spassk-Dalny, which is the center of the Primorye construction industry, is among the most polluted cities in the region ^[40], while unlike a number of other large settlements it is not so overloaded with vehicles: the main sources of air pollution in the city are Novospassky Cement Plant and JSC Spassky Asbestos Cement Products Plant, located within the city limits. cities, as well as the railway and the goods transported on it. Its advantageous location, a long period of standing snow cover, and the possibility of sampling on nearby large lakes formed the prerequisites for a detailed study of the atmospheric chemistry of the area. However, unfortunately, the winter of 2024-2025 turned out to be very warm ^[41], as a result of which practically no high–quality seasonal snow could be detected during the available time, and only one fully conditioned sample was taken in the studied area - of sufficient volume and without traces of additional anthropogenic influences in relation to atmospheric pollution. It is located on a private plot near the city center (about 1 km away from the city administration) (Fig. 10), and thus can correctly characterize the general features of the state of the atmosphere in the settlement itself.

Fig. 10. Location of the sampling point in the Spassky district of Primorye

Table 7 shows the results of the chemical analysis of the components of the snow cover.

Table 7. Concentrations of some pollutants in the solid residue of snow cover and snow water of the Spassky region of Primorye

According to the results obtained, the quality of atmospheric air in the city of Spassk-Dalny is generally significantly better than in the Irkutsk region or, even more so, in Chelyabinsk. The concentrations of pollutants in the solid residue are closer to small settlements in the Baikal region, with only increased concentrations of iron, which corresponds to the data of their predecessors, who noted increased concentrations of iron oxide, steel, and pyrite particles in snow and pine needles ^[36].

At the same time, no soluble forms of pollutants were detected, with the exception of lead. Interestingly, elevated concentrations of both lead and a number of other pollutants (Cu, Fe) in the snow water of Spassk were noted in the previously cited study. However, sampling points with such abnormal concentrations of Cu, Fe, and Pb were localized strictly at points located tens of meters from the railway, and data from the predecessors are not provided at more remote points. Our sampling point is located 1 – 1.5 km from the railway infrastructure and there are no other known nearby sources of impacts, therefore, most likely, dust pollution in the city is local. In addition, the predecessors studied freshly fallen rather than seasonal snow, as a result of which, even if the selection points completely coincide, the research results may not completely coincide, as noted in the introductory part of the article. In general, the local background of the city can be considered close to the small towns of the Baikal region.

4. Discussion of the results

In the table. 8 and 9 show a comparison of the detected concentrations of pollutants for all studied areas in solid residue and snow water, respectively.

Table 8. Variability of chemical parameters of seasonal snow solid residue

Table 9. Variability of chemical parameters of snow water

A summary diagram of the median concentrations of all the pollutants studied in all regions (except Novonukutsky) is shown in Fig. 11.

Fig. 11.Summary chart of the median concentrations of all pollutants studied in all regions (except Novonukutsky)

The presented data allow us to formulate the following statements:

1) Chelyabinsk is certainly the absolute "leader" in terms of average and median concentrations of pollutants in the solid residue of snow cover. The minimum detected values here often exceed the maximum detected values in other localities. The minimum values of geochemical parameters are typical for areas of the Baikal region remote from the main production infrastructure, and often such facilities are characterized by the inability to determine concentrations of pollutants: in solid residue due to insufficient residue on filters, and in snow water due to its high purity. The first problem can be overcome by collecting high-volume snow samples, and such a situation should be foreseen in advance when using snow geochemical surveying as a method of background atmospheric and chemical environmental studies of sites with a priori no industry.

2) When trying to generate maps of the level/degree of air pollution using standard methods based on the calculation of contrast coefficients and integral pollution indicators relative to the "median" background, in the absence of a significant number of points with a natural geochemical situation within the tablet (as it almost always will be in areas with a high level of anthropogenic load), researchers may encounter the fact that that the degree of air pollution in populated areas with actually orders of magnitude different amounts of pollutants in the air will seem comparable. So, in the above examples, in all the studied areas, the contrast coefficients relative to the median background are approximately at the same level - within 2.

3) The results presented in the tables are a cautious attempt to solve this problem by identifying the regional background. At the same time, from a comparison of tables 8 and 9, it is quite obvious that studies of the solid residue of snow cover provide significantly more informative information, especially from the point of view of mapping the quality of the atmosphere, since these data in the vast majority of cases are characterized by both the presence and significant variability. Thus, no measurable concentrations of iron and nickel were found in any sample of meltwater. Arsenic was correctly detected only once in Chelyabinsk. Lead has measurable variability only in Chelyabinsk, zinc in Chelyabinsk and Novonukutsk, copper in Chelyabinsk and Cheremkhovo. According to the authors, this directly indicates that monitoring, and especially assessment of the background condition of new sites in areas not subject to obvious anthropogenic impacts, cannot be based solely on studies of soluble forms of pollutants in snow water – that is, the most traditional and widely used approach to snow geochemical studies. In this regard, an attempt was made to study the variability of the chemical parameters of the solid residue for various natural and anthropogenic environments, since there are few such reference data in the literature that allow us to somehow relate to the obtained concentration values (are they low or high?).

4) However, this attempt can and should be criticized from at least two positions. Firstly, the values given in the article are based on an insufficiently representative factual base. For various reasons, unable to perform detailed snow and geochemical surveys similar to the Irkutsk agglomeration in all the studied areas, the authors tried to select single samples in such a way that they best characterized both the minimally and maximally polluted areas of the research objects, however, there is no There is no evidence that this has been fully successful. Nevertheless, it seems to us, and it follows from the data and arguments presented in the work, that at least the general atmospheric and biochemical features of various regions and, more broadly, various natural and anthropogenic situations have been recorded and presented. In this case, the specified minimum values could be treated as reference and even conditionally background values, but for this it is necessary to take into account the second problematic position, namely that the concentration of pollutants in the solid residue of snow cover, measured in ppm, mg/kg and similar values, is not necessarily obvious in itself. an indicator of the degree of air pollution. The fact is that such a parameter does not contain information about the amount of this residue, as a result of which the actual intake of pollutants per unit of time per unit area can vary widely – a low concentration of a particular element in a large amount of dry residue will seem more dangerous than a high concentration in a minimal volume, although in fact the first case in an environmental This poses a much greater danger. The paper notes that in areas with a low level of anthropogenic load, the dry residue may be low or practically nonexistent, and in this case, minimal introduction of the pollutant will give a very high concentration of it. These features and ways of working with them are described in the literature ^[42], and they should be taken into account. However, for monitoring studies of the area, the purpose of which is to record changes in the situation, with a constant sampling network, concentration parameters may be sufficient.

5. Conclusions

And the authors hope that, despite the limited amount of factual material, they were able to quite clearly characterize the general features of the behavior of pollutants in various components of the snow cover for characteristic man-made and man-made environments, identify and present some characteristic situations that researchers will encounter in practice, namely:

1) It is shown that in all cases, both under high load conditions and in background areas, it is absolutely necessary to study not only snow water, but also solid residue, in order to accurately characterize the state of the atmosphere.

2) When studying the solid residue, researchers will face two problems - perhaps an insufficient amount of material for chemical and analytical studies in areas not subject to serious anthropogenic influence or natural high dust load, and the difficulty of interpreting the measured concentration parameter as an environmental characteristic. Appropriate recommendations are provided to address both issues.

3) The approximate "background" parameters and the limits of their variability for a number of regions of the eastern part of Eurasia are given. The patterns of behavior of chemical characteristics in various natural and anthropogenic environments are shown. These data make it possible to supplement the existing theoretical basis of atmospheric and geoecological studies, since these data can be treated as a scientific basis for calculating contrast coefficients and complex pollution indicators. The identified parameters of the solid residue are especially important due to the objective lack of scientific data on its "normal" and "abnormal" concentrations for various areas and levels of atmospheric pollution.

4) Based on a comparison of data on different areas, the air quality in Chuliabinsk, Irkutsk region, a number of settlements in the Baikal region and in the Spassky region of Primorye is characterized. It is shown that the pollution of Chelyabinsk's atmosphere with heavy metals and arsenic is many times higher than other populated areas, even contributing to the Russian air quality anti-rating. It is shown which levels of chemical parameters can be treated as fairly universal, since they are stable and observed in various areas.

It seems that further gradual addition of public scientific and literary sources with new data on snow geochemistry of various districts and regions will form the necessary scientific and methodological basis for the widespread use of snow geochemistry not only in scientific, but also in conditioned environmental studies and surveys, as it will be possible to reasonably judge the normality or anomaly of the recorded parameters for the region, area, a polygonal item.