The distribution of natural (at the level of global background) and technogenic radionuclides in groundwater of the industrial zone in Sosnovy Bor town, where several nuclear power facilities are operating, was analyzed. The main technogenic radionuclides recorded in groundwater samples are cesium ( 137 Cs), strontium ( 90 Sr), and tritium isotopes. The first two aquifers from the surface are subject to contamination: the Quaternary and the upper zone of the Lomonosov aquifer. Based on extensive material on the engineering and geological studies of the work area, a 3D geological model and hydrodynamic and geomigration models of the industrial zone were constructed. By means of modeling, the extent and nature of changes in hydrogeological conditions of area resulting from the construction and operational drainage of the new stage of the Leningrad Nuclear Power Plant (LNPP-2) were determined. The “historical” halo of radioactive contamination of groundwater forming (1970-1990) at the site adjacent to the NPP, where the storage facility of low- and medium-level radioactive waste is located, falls into the zone of influence. Interpretation of monitoring data allowed obtaining the migration parameters for predictive estimates. Modeling has shown that during the time of the LNPP-2 operation there was no intake of contaminated water by the drainage system of the new power plant.
The paper analyses features of the species composition and diversity of biotic communities living within the ferromanganese nodule fields (the Clarion-Clipperton field), cobalt-manganese crusts (the Magellan Seamounts) and deep-sea polymetallic sulphides (the Ashadze-1, Ashadze-2, Logatchev and Krasnov fields) in the Russian exploration areas of the Pacific and Atlantic Oceans. Prospects of mining solid minerals of the world’s oceans with the least possible damage to the marine ecosystems are considered that cover formation of the sediment plumes and roiling of significant volumes of water as a result of collecting the minerals as well as conservation of the hydrothermal fauna and microbiota, including in the impact zone of high temperature hydrothermal vents. Different concepts and layout options for deep-water mining complexes (the Indian and Japanese concepts as well as those of the Nautilus Minerals and Saint Petersburg Mining University) are examined with respect to their operational efficiency. The main types of mechanisms that are part of the complexes are identified and assessed based on the defined priorities that include the ecological aspect, i.e. the impact on the seabed environment; manufacturing and operating costs; and specific energy consumption, i.e. the technical and economic indicators. The presented morphological analysis gave grounds to justify the layout of a deep-sea minerals collecting unit, i.e. a device with suction chambers and a grip arm walking gear, selected based on the environmental key priority. Pilot experimental studies of physical and mechanical properties of cobalt-manganese crust samples were performed through application of bilateral axial force using spherical balls (indenters) and producing a rock strength passport to assess further results of the experimental studies. Experimental destructive tests of the cobalt-manganese crust by impact and cutting were carried out to determine the impact load and axial cutting force required for implementation of the collecting system that uses a clamshell-type effector with a built-in impactor.
The conditions for the occurrence of near bottom minerals presented in the form of sulphides (the Logachev deposit) and ferro-manganese nodules (The conditions for the occurrence of benthic minerals presented in the form of sulphides (the Logachev deposit) and ferro-manganese nodules (FMN) are considered. An analysis of the structures and parameters of various means of collecting and transporting sulphides and iron ore from the bottom to the surface is given, and the possibility of effectively using vessel lifting on a cable-rope is indicated. Structural schemes for collecting FMN and sulphides in the form of containers on a cable, equipped with manipulators with gripping devices of a disc, drum or clamshell type, are proposed. In them, the capture of rock pieces or FMN is carried out by creating a vacuum in the collectors of the executive bodies and attracting to them pieces of rock or FMN by a pressure drop of water inside and outside the reservoir. It was given the approximate parameters of the mining system. So, for a cable-rope made of kevlar with a diameter of 50 mm, the capacity can be 200-400 thousand tons per year for one installation with different specific mass concentration of FMN per 1 m 2 ) are considered.
The paper reviews the main methods and analyzes modeling results for geochemical processes in the submarine discharge zone of hydrothermal solutions of mid-ocean ridges. Initial data for modeling have been obtained during several marine expeditions, including Russian-French expedition SERPENTINE on the research vessel «Pourquoi Рas?» (2007). Results of field observations, laboratory experiments and theoretical developments are supported by the analysis of regression model of mixing between hydrothermal solutions and sea water. Verification of the model has been carried out and the quality of chemical analysis has been assessed; degree and character of participation of solution components in the hydrothermal process have been defined; the content of end members has been calculated basing on reverse forecasting of element concentration, depending on regression character; data for thermodynamic modeling have been prepared. Regression model of acid-base properties and chloridity of mineralizing thermal springs confirms adequacy of the model of double-diffusive convection for forming the composition of hydrothermal solutions. Differentiation of solutions according to concentrations of chloride-ion, depending on temperature and pH indicator within this model, is associated with phase conversions and mixing of fluids from two convection cells, one of which is a zone of brine circulation. In order to carry out computer thermodynamic modeling, hydro-geochemical and physicochemical models of hydrothermal discharge zone have been created. Verification of the model has been carried out basing on changes of Mn concentration in the hydrothermal plume. Prevailing forms of Mn migration in the plume are Mn 2+ , MnCl + , MnCl 2 . Two zones have been identified in the geochemical structure of the plume: 1) high-temperature zone (350-100 °С) with prevalence of chloride complexes – ascending plume; 2) low-temperature zone (100-2 °С), where predominant form of transfer is a free divalent ion – lateral plume. Sulfate complex in insignificant quantities (1.5 %) is detected in the lateral plume, whereas hydroxide complex is stable at temperatures 325-125 °С and can only be found in the ascending plume. Results of modeling almost fully correspond to field observations. Verification of thermodynamic model proves its adequacy and allows to make a transition to the next stage of research – examination of geochemical dissipation for key ore components of hydrothermal solutions – Fe, Cu, Zn etc.
The article deals with hydrogeochemical processes in the productive strata in the course of oil field development. The impact of flooding on the change of the chemical composition of reservoir water and the possibility of salification are analyzed. Computer thermodynamic modelling of physico-chemical processes is used for prediction of salification in oil fields.
The article deals with the role of groundwater in methane formation in coal fields of North-East Vietnam using the example of Maohe deposit. Main geochemical processes during groundwater filtration in a coal bed are determined.
The results of Russian and international expeditions for investigation of hydrothermal plumes and solutions in the Atlantic tropic zone on deep Mid-Atlantic Ridge hydrothermal fields connected with ultrabasic rocks are considered. Visual observations and sampling using submersibles and tow vehicles show the unsteady character of hydrothermal discharge, phase separation of high-temperature (~350 °C) solutions with high content of hydrogen and methan, iron and manganese, low pH and changeable on time and fields area mineralization. High content of H2 and CH4 could be connected with interaction of ultramafics with seawater on high-temperatures and pressures and serpentinization processes.
Features of submarine hydrothermal discharge and geochemical anomalies in bottom waters of Mid-Atlantic Ridge are observed. In the typical section of hydrothermal halos two major zones could be distinguished: forming by the rising stream gravitationally non-stable structures and more stable formations on the horizon of lateral flow. Discrete structure of hydrothermal plumes and matter differentiation are discussed. Different types of fluid discharge are revealed on the Logatchev field. As a result three kinds of hydrothermal plumes are forming: of positive, neutral and negative buoyancy.
The main geological and thermodynamic conditions of hydrothermal vents formation and activity. Calculation of hydrothermal field vents flow have been made after E.S.Romm model. A comparison of model data with data obtained in the Russian-French expedition «SERPENTINE».
A genesis of hydrothermal solutions of the explored area is observed. A short characteristic of main settings determining the ore-forming features of hydrothermal solutions is given. The groups of elements connected with the hydrothermal solutions-seawater mixing are marked out as well as those coming directly from the magmatic chamber and contacting rocks.
Difference in structural position and influence of ores from different types of sediments on the geochemical characteristic of ores are observed. Results of end member composition correlation analysis show negative link of H 2 S with CH 4 и Н 2 .
Geological and tectonic settings and thermobaric characteristics of hydrothermal activity are confronted with those of gas hydrate formation. Hydrocarbon concentrations and isotopic composition in hydrothermal fluids of mid-ocean ridges with different thickness of sediment cover and marginal oceanic basins are compared. The possible influence of rising thermal fluids on gas hydrate accumulations was analyzed and examples of hydrate formation linked with hydrothermal process are given.
Types of submarine hydrogeological structures with modern hydrothermal activity in the North Atlantic are observed. Most part of noted hydrothermal fields are situated within the limits of the Mid-Atlantic Ridge (MAR). There are inner and outer (relative to main MAR structural elements) suboceanic hydrogeological structures. Axis, hillside and summit hydrogeological massifs are distinguished. Outside MAR volcanogenic massifs with periodical hydrothermal activity are forecasted due to geochemical anomalies in bottom waters.
A physical and mathematical model of the formation of a dispersion halo of a hydrothermal source located on the ocean floor is presented. According to the experimental data, the formation of such a halo occurs in a stratified (two-layer) medium. The system of stationary differential equations of convective diffusion at constant values of vertical and horizontal components of the velocity vector of quasi-convection, diffusion coefficient, absorption coefficient of dissolved matter, taking into account the transition of dissolved matter into solid phase by precipitation or sorption on suspended particles, within each of the layers is solved. Solutions of the simplified system of stationary differential equations of convective diffusion are given. The developed model satisfactorily describes the available experimental data, which allows us to recommend it for theoretical study of the concentration distribution of the mobile component in a hydrothermal halo.
Уже доказана теоретическая и практическая возможность проведения поисков золоторудных проявлений на основе прямых гидрогеохимических показателей - непосредственного обнаружения золота в тех или иных количествах в водах ...
В рельефе современной поверхности Прионежья прослеживаются три террасы с абсолютными отметками гипсометрических уровней 30-60, 60-100 и 100 м и более. Максимальные высоты не превышает 300 м ...
