No 6 (2019)

This paper reviews the development of engineering geological studies at the Ocean seabed in the Russian Federation for the last 50 years in relation to the works undertaken by Engineering Geology Laboratory of the Ocean seabed – the department of FSBI “VNIIOkeangeologiya”. The potential perspectives of the Ocean mineral resources exploration and extraction attract the attention of experts to the seabed engineering geology. This includes an analysis of the geological, engineering geological and other survey results undertaken so far, as well as the future planning for the engineering geological studies in the Ocean seabed.

Suffusion processes and their influence on the stability of the Rostov NPP site are investigated. Geological, tectonic, geomorphological, hydrogeological conditions, as well as anthropogenic factors affect the development and intensification of suffusion. These conditions and factors include the following: predominance of Pliocene and Quaternary sands in the geological cross-section; the presence of clay aquiclude underlying sandy deposits; natural seasonal and human-induced fluctuations of the water level in the Tsimlyansk reservoir; as well as pumping of groundwater. The buried relief in the shape of a slope dissected by erosional gullies are also of great importance. These erosional depressions are probably channels, along which sand is removed to the Tsimlyansk water reservoir. It is suffusion that may be the reason of surface subsidence that causes deformation of ground basements and inclinations of some engineering structures at NPP. Recent tectonic conditions control the formation of active zones and fracturing in the mantle deposits favoring percolation of surface water. Suffusion amplified by tectonic and technogenic factors results in the subsidence of soil basement in some places at the NPP site, displacement of reference marks, and inclination of engineering structures.

In 2016-2017, we have detected numerous organic frost boils on the surface of khasyrey peat plateau in the southern tundra part of Pur-Taz interfluve (the north of West Siberia). They are related to the microrelief depressions in polygons and to the swales between tussocks. Cross-sections, cryogenic structure, properties of peat in active layer (moisture, density, heaving, chemical composition) and peat distribution within the khasyreys were studied. In the active layer, we distinguished soil and vegetation cover, upper and middle solid layers of weakly decomposed peat, lower layer of a well decomposed peat. Under the microrelief depressions, the top of permafrost is lowered, thickness and moisture of decomposed peat is increased due to the recent thawing in comparison to the elevated parts of polygons. In the cross-sections of seasonally thawing peat, we determined injections of organic matter from the lower layer of peat to the surface. We propose the mechanism of organic frost boils formation in peat plateau due to the injections during the summer seasons of 2016-2018 against the increase of a thaw depth without freezing. During the observation period, the amount of frost boils on polygonal peat plateau was found to increase.

This study aims at investigating the allocation conditions of rock dumps in the South zone located in the Elkon uranium mine region (the Southern Yakutia), and also at determining their radiation parameters as sources of technogenic contamination of the soil-vegetation cover and surface waters, and assessing the danger of these dumps for people. In this study, the generally accepted geographical methods were used, including comparative geographical and geochemical methods, as well as a combination of various radiometric research methods. The radiation parameters of the rock dumps of the South zone of the Elkon uranium mine region, the content and distribution of uranium, radium and radon in surface waters, as well as ²³⁸U content in technogenic soils at different distances from radioactive contamination sources were studied. It was found that the most active dumps, in terms of their radiation parameters, are located close to the radioactive ores, with the EDR of 1600-2150 μR/h, effective specific activity - 20441-23640 Bq/kg, and uranium content of 1637-1888 mg/kg. The ranking of the studied dumps according to the degree of radiation hazard showed that 12 out of 31 dumps (39%) belong to the safe category, 6 (19%) belong to the category of potentially dangerous, and 5 and 8 (16% and 26%) were classified as dangerous and very dangerous respectively. In the conditions of the mountainous terrain, cold and humid climate of the studied area, these rock dumps, which are unevenly spread in mountain and taiga landscapes over the area of about 500 km², are the main source of radioactive contamination of soil and vegetation cover and surface waters. The maximum contents of uranium, radium and radon in the studied surface waters were 180×10^-7 g/L, 4.7×10^-12 g/L and 256.8 Bq/L respectively, which are 100, 8 and 198 times higher than their background concentrations in waters of natural landscapes. In the studied technogenic zones, a direct relationship was registered between the pollution intensity in surface water and that in the drained alluvial soils formed in the floodplains of these watercourses.

The quantitative chemical analysis of snow cover has been carried out for the Vorkuta agglomeration territory. The on-site ingress of pollutants in close proximity to industrial enterprises in Vorkuta is calculated. The schematic maps of substance distribution in snow in the studied area are built using space images. The control levels of aerotechnogenic pollution are established for the city, industrial zones and adjacent territories for the purpose of subsequent ecological monitoring. The pH value of snowmelt water reaches 6.5-7.2 due to a high content of alkaline components (calcium and magnesium carbonates) in snow. The snow cover of the Vorkuta agglomeration is highly enriched with heavy metals. The maximum permissible concentrations are exceeded for manganese, nickel, aluminum, vanadium, molybdenum and mercury. High concentrations of mercury in snow are supposedly related to coal combustion at the thermal power plant. After that mercury may be occluded on a surface of coal particles and ashes. It is shown that it is possible to establish the zones of the greatest aerogenic impact according to the content of mercury and vanadium in the snow. Factor analysis was used to identify the mechanisms of pollutants and factors forming the chemical composition of the snow cover. The share of elements in the suspended solids is more than 60% of their total content in snowmelt water. High concentrations of suspended particles (up to 720 mg/dm³) were observed in the snow of Vorkuta. The most severe pollution of the snow cover is registered in close proximity to thermal power plant №2. According to the calculations of the total pollution index, the highest excess of substance increment over the background level was noted in the sanitary protection zone around the thermal power plant №2.

Urbanized areas are considered as single natural and technogenic systems. Ensuring safe development of urban areas is associated with natural risk assessments. It is proposed to carry out a special zoning of urban areas. In the selected areas, risk is formed according to certain scenarios. The proposed zoning involves a successive subdivision of the city territory by natural and technological factors using usually only one feature at each step. As a result, we come up with relatively homogeneous areas. Thus, a consistent division of a total into parts for each group of factors is achieved. Various combinations of these factors are also taken into account when distinguishing typological taxons.