No 3 (2023)

The Kazbek segment differs from the adjacent Central and Eastern segments of the Greater Caucasus megavault by the relative narrowing of the main zones and their latitudinal orientation. The main units of the segment comprise the zones of central elevations and northern and southern flanks. The application of orotectonic method allowed us to subdivide these zones into a number of regional and local late-stage structures separated by active faults. There are three suture zones. The pattern block structures are separated mainly by downthrows. The original data obtained, which are not presented in standard materials on geological survey, are useful for construction design and in solving geoecological tasks.

As a result of monitoring observations, it was found that the frequency of subsidence in different sections of the railway embankment in different years is associated with different engineering and geological conditions and leading cryogenic processes. It requires the special geocryological zoning of the territory adjacent to the railway to develop an engineering protection strategy. The criteria for ranking areas with embankment settlements according to their hazard degree, which are divided according to spatial and temporal characteristics are proposed. It was revealed that the long-term climate changes lead to a regional change in geocryological conditions (primarily the temperature regime of soil). The extreme climatic events and variable technogenic loads cause activation or attenuation of cryogenic processes.

Despite the wide distribution of sulfate and carbonate karst in the study area, the nontraditional, rarely encountered karst types are also registered. These are clastokarst, karst of calcareous tuffs, sulfide karst, salt karst and marble karst. For each of these nontraditional types of karst, the conditions and factors of development were determined according to the karstic rock composition. Calcareous tuff karst is the least common in the study area, meanwhile clastokarst is widespread. Calcareous tuff karst is spread in the westernmost part of the Southern CisUrals, in the eastern outskirts of the Volga-Ural anteclise; and clastokarst is found in the western margin of the Yuryuzan-Sylva depression of the CisUrals marginal foredeep. Sulfide karst is developed in the plains of the Southern TransUrals within the Magnitogorsk megazone of the Ural folded system, and salt karst occurs in the flat foothills of the Southern Urals within the Belaya Megadepression and the Shikhan-Ishimbai saddle of the CisUrals marginal foredeep. It has been established that the previously identified areas of clastokarst distribution in the west of the area under consideration are not confirmed by modern and Pleistocene forms of its manifestation. The negative impact of clastokarst on economic facilities and humans is comparable to the impact of the most common and dangerous sulfate karst, and this must be taken into account when designing and constructing new buildings and engineering structures. Salt karst is manifested in artificial leaching of rock salt at a depth, such salt is necessary for the production of soda ash (JSC “Soda”); the formed voids are used as underground storage facilities for oil products (OJSC Podzemneftegaz). Calcareous tuff karst is a rare type of karst in the region under consideration, it can be observed at the complex natural monument “Shumilovsky waterfall”. Surface manifestations of sulfide karst can be a search feature of new copper-sulfide deposits. Non-traditional types of karst have both positive and negative practical implications. Karst in marble complicates the development of mineral deposits, and clastokarst complicates the economic development of the territory. Calcareous tuff karst creates unique local landforms, and sulfide karst is of practical importance in the search for new mineral deposits. On the one hand, salt karst determines the extraction of minerals deposits and contributes to the creation of useful underground storage facilities, on the other hand, it destroys them.

The strongest earthquake in the Urals registered during the period of instrumental observations, with a magnitude of M_L-5.4 occurred in the area of Katav-Ivanovsk city, Chelyabinsk region, on 05.09.2018. In October 2018, Institute of Geophysics, the Ural Branch RAS organized temperature and radon observations. The conducted studies have shown that the behavior patterns of the volume radon activity (VRA) established for the tectonic event preparation in the subduction zone (Southern Kuriles), are also true for the South Ural region. The natural phenomena caused by the earthquake 2018 preparation are analyzed. During the observation period from 28.11.2018 to 23.05.2019, there was an increase in temperature with a gradient of 0.02°C per month. The observed patterns of VRA abnormal behavior before aftershocks in the Katav-Ivanovsk area are typical for the compression zone in the radon monitoring area. It is noted that the assumed compression deformations were manifested in the hydrogeodynamic field at least 10 years before the event proper. The proximity of earthquake foci to the identified aseismic zone within the boundaries of the East European Platform, the Pre-Ural Regional Trough, and the Bashkir anticlinorium indicates the most likely places of seismic events. The arranged temperature and radon monitoring network in the epicentral zone by observing aftershocks has shown the possibility of tracking the earthquake preparation process.

The problem of water body pollution with heavy metals is still relevant. From the viewpoint of technogenic load, the most hazardous pollutants are elements Hg, Cd, Zn, Pb, Cu, Cr, Co, Ni, Fe, Mn, and As. To systematize the research, the objects of different hierarchical levels were identified. Based on many years of experimental work, contamination of sediments with heavy metals was assessed for the Upper Volga system, i.e., Lake Seliger, an unregulated section of the Upper Volga, Ivankovskoe and Uglichskoe reservoirs. The largest taxon is the basin of the reservoir with the adjoining watershed area with cities and towns located on it, tributaries of various orders, smaller elements of natural and natural-technogenic relief. Urban and settlement agglomerations located on the coasts of reservoirs and unregulated areas or within watersheds are smaller in area, but no less significant in their role in water body pollution. Small rivers contribute to pollution/purification, which can contribute to the flow of both clean and polluted silty material into large watercourses. Different areal and temporal survey modes are offered for taxa of different hierarchy. The practical results of studies of the content in sediments of the listed objects of heavy metals – Cr, Co, Ni, Zn, Cd, Pb, As, Fe and Mn are presented. Described or provided references to the methods used in the experiments. The general picture of pollution is presented and the tendencies of its change in space and time are noted.

PJSC Nizhnekamskneftekhim is one of the largest petrochemical companies in Europe. Industrial production was launched there in 1967. Production waste is stored in a sludge reservoir and waste landfill. The landfill has been operating since 1982. It is equipped with systems of surface and underground drainage, impervious curtains, and two belts of observation wells. More than 0.5 million m³ of mostly solid waste III-V classes of hazard has been accumulated there. The landfill capacity is depleted by more than 80%. Its operation has led to a significant groundwater level rise (4.0–4.5 m) and groundwater pollution, the water salinity reaching 12.75 g/l, and hardness, 73.9 mmol/l. These negative hydrogeoecological effects are primarily due to increased atmospheric recharge of groundwater and the active interaction of atmospheric precipitation with the waste substance. There is plan to reconstruct the landfill. It involves encapsulating the waste in a watertight reservoir confined by artificial geosynthetic materials with extremely low filtration properties. Hydrodynamic and balance methods were used to determine the infiltration supply of groundwater in natural and disturbed conditions, productivity of underground drainage; the continuously formed flow rate of polluted groundwater, which is not intercepted by drainage system (with the flow discharge equal to 116.7 m³/day); as well as modern and predicted (postreconstruction) water balances. The effectiveness of the existing engineering protective structures of the landfill was assessed. It is shown that the planned reconstruction should lead to a decrease in the groundwater level and its pollution degree. In this case, the concentrations of organic substances, which are the priority pollutants, will decrease most intensely. The geological environment of the landfill site is characterized by significant buffer (protective) properties. They control just local spreading of contaminated groundwater. According to the data of numerous different-time sampling at a distance of 1.0–1.5 km from the landfill in the direction of groundwater current spreading, no signs of pollution caused by the landfill operation are registered. The main processes determining the self-purification of groundwater are as follows: dilution of polluted water by pure infiltration nutrition, the minimum layer of which is 67.6 mm/year; chemo- and biodestruction of pollutants, their sorption, diffusion-dispersion scattering and precipitation as pH–Eh conditions change.

The article discusses two different ways to classify space images of Landsat-8 satellite by the example of the sand massif in the Kazan-Veshensky key area, the Rostov-on-Don region. The first method is a semi-automatic raster classification with training (SC) of selected reference areas, the second is a normalized vegetation index (NDVI). Taking into consideration K.N. Kulik typology of sands, the following classes are distinguished in the satellite image, i.e., open, slightly overgrown and overgrown sands. Also, shrub and herbaceous (plants in the vegetative state), pine forest plantations, and native forest with tree splits were marked as individual classes. The degree of sand overgrowth with native vegetation was estimated according to the projective cover. The resulting raster images were vectorized for further work. The estimation of cartographic image classification accuracy by the Cohen’s Kappa index was calculated. This work is necessary to identify the most reliable method for deciphering the selected area images. The resulting map can be used for initial assessment of phytoecological conditions of agrolandscapes in the sandy massif area. On the basis of cartographic images, by setting from 70 to 100 points in each class and checking their reliability by using archival satellite image for 07.07.2020, error matrices were complied, which permitted us to calculate the total interpretation accuracy. For semi-automatic classification with training, it constitutes 80.7%, and NDVI – 74.3%. According to the vegetation index with a smaller error, the classes of open sands and weakly overgrown sands were distinguished, in other cases the SC method turned out to be more accurate. Cohen’s Kappa coefficient in the semi-automatic classification with training is 77.4%, NDVI – 70.5%. The difference in classification accuracy is almost 7%. Thus, the optimal method for preliminary analysis of the Kazan-Veshensky sand massif key area using Landsat-8 satellite images is a semi-automatic classification with training.