Vol 44, No 7 (2017)

Urban subsurface space is considered to be a dynamic multicomponent system, which includes sandy-clayey soils, groundwater in different state, microbiota, gases, and underground facilities (either as foundations or as surrounding walls), or engineering structures (tunnels of different purpose, hazardous industrial-waste storages, etc.). Special attention is paid to the significance of hydrogeological studies, primarily, to the influence of hydrodynamic and physicochemical conditions and aquifer chemistry on soils, stress and strain state of the stratum, deformation of structures, and the formation of corrosiveness of subsurface medium. The main factors that govern groundwater composition within zones with different contamination level in megacity territory are analyzed. Results of studying the effect of various aquifers on the conditions of construction and operation of above-ground and subsurface structures are presented. Recommendations for assessing the hydrogeological conditions as a part of geotechnical survey are given.

The need to take into account the geoecological restrictions in planning and designing urban territories is considered. Geoecological restrictions are analyzed and systematized. The criterion for assessing the priority of restrictions is the degree of their hazard for various recipients. An algorithm of a procedure for such assessment is given. Approaches to zoning by geoecological restrictions for newly developed and reorganized territories are proposed. Successive analysis and compilation of maps are considered. The map of zoning an urbanized territory by geoecological restrictions and its use for designing will facilitate the formation of an environment favorable for human activity and sustainable development of urban territories.

Crimean water resources are limited, failing to fully meet the drinking and economic needs of the region. Over 50 years, the problems of water resources in Crimea were solved by using Dnieper water supplied through North-Crimean Canal; however, after the integration of Crimea into Russia, Ukraine suspended water supply. At the aggravation of political situation between Russia and Ukraine, the situation in the water-management sphere in the Republic of Crimea looks very complicated. The water-management problems of Crimea should be solved based on its own potential. Groundwater resources are the leading factor of sustainable development of Crimean Region at the present stage.

Geochemical processes involving redox reactions and leading to either formation or transformation of geochemical barriers may be largely induced or enhanced by microbial activity. The microbial reduction of uranium is studied as a strategy for rehabilitation of uranium-containing groundwater. The bioremediation mechanism converts dissolved uranium(VI) into low-solubility U(IV). The processes involving dissimilatory reducing bacteria, which facilitate the reduction and retention of U(VI) in soils and rocks, are considered. The diversity of microorganisms involved in anaerobic reduction of uranium is shown. The geochemical conditions that may affect the rate of microbial reduction of U(VI) are specified, i.e., the presence of nitrate ions, phosphate ions, calcium ions, and iron oxides. The mechanisms of their action are examined. Geochemical barriers with the participation of microorganisms are proposed for the rehabilitation of groundwater with uranium removed from groundwater and deposited locally as a result of microbial reduction of U(VI).

The geochemistry of a dry dump of arsenic production wastes and a groundwater protection zone were studied with the use of macro- and microanalysis of aqueous and hydrochloric-acid extracts. The accumulation of water-soluble forms of the microcomplex is maximal in the surface layer of the cinder dump, in sulfate-acid zone. Here, aluminosilicates suffer acid destruction. The downward motion of sulfate-iron front at a decrease in medium acidity is accompanied by gypsum formation and the hydrolysis of sulfate salts with subsequent formation of Fe, Al, and Mn hydroxides. The technogenic geochemical sorption barriers, which form in this process, ensure self-conservation of pollution source. In the protection zone, carbonate-alkaline barrier completes the immobilization process. Over the 70 years of dump existence, only a small part of its immobilization potential have been utilized. The sulfate-acid process can be suppressed through the isolation of the dump from atmospheric moistening. The vulnerability of water objects is zero. The evacuation of the dump is not required, as local reclamation is enough.

The article considers the procedure aimed to identify and select the factors, events, and processes that can have an effect on the long-term safety of radioactive waste repository to be constructed at The Yenisei Site (Krasnoyarsk krai). The geological factors to be taken into account in the development of scenarios for safety assessment are determined. Tentative quantitative forecasts of radionuclide migration are made taking into account possible climate evolution and vertical rise of the territory. The sensitivity of radionuclide migration model to variations in these factors is assessed.

The effect of land reclamation on the migration and accumulation of heavy metals and some pollutants in small rivers is determined. The study was conducted in the Middle Amur lowland in different phases of hydrological regime and at different extent of floodplain inundation. The formation of the hydrological regime in small rivers in this area is governed by the irregular annual runoff distribution. The seasonal character of flood periods requires water samples to be taken before spring flood (April) and after floods have passed (September–October), and at various extent of floodplain inundation. The field studies of water-courses were carried out in 2009–2014. The water samples were analyzed to determine the concentrations of heavy metals (iron, manganese, copper, nickel, cobalt, lead and zinc), suspended substances, organic carbon (total, dissolved, and suspended), humic and fulvic acids, and volatile organic compounds. The mobility of heavy metals in surface watercourses was shown to reflect the effect of drainage and surface runoff from soil horizons, an increase in the concentrations of suspended and organic compounds, especially, fulvic acids, which enhance their geochemical mobility. During floods, an increase in heavy metals washout from floodplain soils and the dilution of their concentrations causes the formation of a single-type concentration series of heavy metals. In addition, the processes of pollutants migration show an effect of changes in the geomorphological characteristics of floodplain–channel complexes and a decrease in flow velocity in watercourses in the areas where land reclamation was applied. Thus, all factors mentioned above lead to a decrease in water pollution index in the river.

The study area refers to the class of highly complex geotechnical conditions. Hazardous geological processes (HGP) are active here, including high seismicity up to 7 points MSK-64, karst, suffosion, subsidence and collapses of land surface, underflooding and flooding, erosion, ecological processes, etc. Large industrial plants with hazardous production and complex infrastructure are in operation here. One such plant is the First Berezniki Potassium Production Mine (BPPM-1), which have been operated since 1954. Its mine field extends below the industrial zone and the residential quarters of the town. An accident took place here in 2006, resulting in the inundation of the entire mined-out space with a volume of more than 80 million m3 and the formation of huge collapses of land surface in 2007, 2010, 2011, and 2015. The geological structure of a mine in the Verkhnekamskoe deposit of potassium salts is used as an example to discuss the effect of two leading groups of geological factors on the formation of karst sinkholes. Analysis is given to the hydrodynamic conditions and geomechanical structure of the above-salt rock stratum, whose synergy determines the diversity of models of possible development of deformations and collapses of land surface. The article gives the possible development schemes of land surface collapses above the mined-out space. The objective of the study is to assess and forecast the development of hazardous geological processes in the territory of Berezniki T. based on the geotechnical interpretation of the available materials of geological works, engineering surveys, and integral monitoring observations.

A method is proposed for assessing the seismic resistance of soils, involving the analysis of seismic data (with soil conditions taken into account), the choice and specification of amplitude–frequency spectrum parameters, experimental studies of soil samples with specified cyclic load parameters, analysis of the dependence of soil behavior on the overload factor, and calculating the ultimate overload factor based on the comparison of accepted and ultimate effect levels. The paper gives the results of practical application of the developed approach to assessing the seismic resistance of a shelf area in the Northern Caspian Sea.