Для решения задачи оценки внешней нагрузки на российскую часть р. Иртыш со стороны водосбора использована модель ILLM, учитывающая вклад точечных и рассредоточенных источников в формирование нагрузки. Модель позволяет рассчитывать вынос примесей с водосбора с учетом влияния гидрологических факторов и удержания химических веществ водосбором и его гидрографической сетью. Для обеспечения модели необходимой входной информацией выполнена классификация подстилающей поверхности с использованием снимков со спутников PROBA-V и Sentinel-2. Собраны и проанализированы данные о содержании биогенных элементов (N и P) и микроэлементов (Cu и Zn) в природных (почвенных и речных) водах изучаемой территории. На основе обработки материалов о деятельности более 800 сельскохозяйственных предприятий оценено поголовье скота, внесение органических и минеральных удобрений, а также рассчитано поступление общего азота и общего фосфора в гидрографическую сеть. По результатам моделирования выполнена оценка внешней нагрузки (включающей диффузную составляющую) биогенными элементами (азотом и фосфором) и металлами (медью и цинком) как для всей российской части бассейна р. Иртыш, так и для семи его подбассейнов, в том числе для рек Тобол, Ишим, Омь и Конда. Оценен вклад трансграничной нагрузки на вынос рассматриваемых химических веществ в замыкающих створах трансграничных рек. Показано, что соотношение вклада различных составляющих внешней нагрузки в вынос изменяется в зависимости от водности года. To solve the problem of assessing the external load on the Russian part of the Irtysh River from the catchment, the ILLM model was used. It takes into account the contribution of point and diffuse sources to the formation of the load and makes it possible to calculate the removal of impurities from the catchment. The model takes into consideration the influence of hydrological factors and chemical retention by the catchment and its hydrographic network. In order to provide the model with the necessary input information, classification of the underlying surface types has been performed using PROBA-V and Sentinel-2 satellite images. Data on the content of nutrients (N and P) and trace elements (Cu and Zn) in soil and river waters of the studied territory were collected and analyzed. Based on the processing of materials on the activities of more than 800 agricultural enterprises, the number of livestock, and organic and mineral fertilizer inputs were estimated, and the total nitrogen and total phosphorus inputs to the hydrographic network were calculated. The external load (including the diffusive component) of nutrients (nitrogen and phosphorus) and metals (copper and zinc) was assessed for both the entire Russian part of the Irtysh basin and for seven of its sub-basins, including the Tobol, Ishim, Om and Konda rivers. According to the calculation results, the contribution of the transboundary load to the outflow of the considered chemicals in the outlet sections of the transboundary rivers was evaluated. It is shown that the ratio of the contribution of different components of the external load to the outflow varies depending on the water content of a year.

The authors discuss dynamics of gas bubble and mineral particle in low-viscous fluid. The particle–bubble interaction model represents a system of associated differential algebraic equations. Dynamics of the disturbed system is described using the Lagrangian method. The model takes into account oscillations of bubble surface and attached solid cylindrical particle in the infinitive volume of perfect incompressible liquid. The capillary force retaining the particle on the bubble is governed by the meniscus shape which conditions the wetting angle. The Legendre series expansion is used to represent small axially symmetrical oscillations of the particle–bubble system. The potential and kinetic energies of the system are expressed in terms of the coefficient of this series. The resultant eddy-free velocity field allows including the viscosity effect with regard to the local rates of energy dissipation.

Data on the main sources of nutrient load on Lake Onego watershed were collected along with the available data of field observations of nitrogen and phosphorus inflow into the lake. Mathematical modeling was used to assess the agricultural load onto the lake and its possible decrease due to the introduction of the best available techniques to agricultural production. It was shown that a decrease in agricultural load after the introduction of best available technologies is unlikely to have a significant effect on the ecological conditions of Lake Onego. Simulation calculations were carried out to evaluate an increase in the input of N and P into the lake from fish farms on the watershed under the condition that the rate of fish farming growth in the water bodies in the basin will remain the same up to the year of 2050. It is shown that, in this case, an increase in nutrient load onto the lake by 3.9

A brief literature review on flotation of calcium-bearing minerals is given. It is found that flotation activity of a collector is connected with physisorption of the collector in particle–bubble attachment. The tests prove that physisorption decrease reduces recovery and increases the useful component content /yield ratio in the concentrate. The found correlation is a framework for new approaches to quality improvement of flotation concentrates. The method proposed to select compositions of collectors can enhance selectivity of extraction of useful minerals.

The characteristics of mineral floatability, namely, the wetting angle and the induction time, are examined. The agreement between the predicted floatability using these characteristics and the theoretical and experimental data is accessed. It is found that hydrophobicity defined by the wetting angle is not always a quantitative characteristic of floatation. The floatability predicted using the time of induction and mechanism of physisorption of collecting agents agrees with the tests and actual practice. The successive change in floatability of sulfhydryl and oxyhydryl collectors in transition between different reagents disagrees with the estimate of the collector force determined from the binding energy between the functional group of a collector and the cation of mineral surface. The force estimated as the effect of a physisorbed collector on the water interlayer between bubble and particle adequately describes floatability of minerals. The mechanism of physisorption of a collector is universal relative to different reagents, is applicable to the description of particle–bubble interaction and enables selecting the structure and composition of radical on an effective collecting agent.

The authors propose the galena flotation mechanism based on the joint work of chemisorbed collector and physisorbed lead xanthate in molecular form. It is proved experimentally that the products of interaction between xanthate and lead ions possess surface activity dependent on the concentration ratio and on solution pH. In alkaline range, they spread over the gas–water interface and can remove water from the interlayer between a mineral particle and a gas bubble. In sub-acid medium and at the increased mole ratio of lead ions to xanthate anions, the spreading velocity of the interaction products decreases. The physisorption mechanism of the collector has disclosed the causes of high floatability of galena in the alkaline range of pH and the decreased floatability in the sub-acid domain.

The authors discuss concentration of fluorite from waste at Yaroslavskaya Mining Company. The waste accumulated in the tailings storage for the long operating period contain 11.6–20.7% of fluorite. Old tailings have specific process properties because the initial ore has experienced certain physicochemical treatment during primary processing, and owing to long storage. The package of balanced effects which ensure selective recovery of fluorite is substantiated. The obtained concentrates contain up to 95% CaF2. Production of fluorite concentrates at maximal removal of silicon dioxide, which is a strictly restricted impurity, is discussed. The ways of improving the processing circuit are proposed, and the efficiency of electrochemical treatment of the pulp fluid phase at the final stages of recleaning is proved. It is found to be possible to reduce the silicon dioxide content of the concentrates to 1.25–0.99%.

The causes of coincidence between pH of a solution of collectors, at which the maximal recovery of a target component is reached, and pH of the solution with minimal surface tension are discussed. Based on the physisorption mechanism of a collector, the floatability connection with the surface tension of the solution is explained. It is shown that extraction of ion–molecular associates from the solution and the presumptive increase in the mineral surface hydrophobicity are not an explanation of the increased recovery. The floatability improvement is achieved via removal of the kinetic constraint of the flotation contact by surface-active species of collectors. The increase in the collecting activity of a blend of collectors is explained by the synergetic effect of the decreased surface tension and reduced induction time. The criterion of flotation activity of a physisorbable collector is proposed.

The literature review discloses preferability of using the time of induction rather than the wetting angle as a criterion of coal floatability. The authors analyze kinetics of coal flotation as function of surface properties of heteropolar collectors relative to the gas–liquid interface. The correlation between the spreading velocity of collectors on water surface and the coal flotation kinetics is determined as a case-study of fat coal slurries. Justification is given for using the time of displacement of the boundary between three states of aggregation as the time of induction. From the correlation of the spreading velocity of a collector, displacement time of the contact line (induction time) and the flotation velocity, it is found that flotation activity of the collector is governed by its properties relative to the gas–liquid interface.

The main mechanisms of flotation activation by ions of metals are discussed and critically analyzed. It is shown that ions of metals can be both activators and depressants of flotation. Based on the mechanism of physisorption, it is revealed when metals act as activators and depressants. A method is proposed to stimulate selectivity of extraction of a target mineral in case of undesirable activation of flotation of associate components. The studies can be useful in selection of metal–activator, ratio of concentrations of activator and collector and pH of flotation system.

Flotation of pyrite is examined as function of pH and ferrous ion concentration. To explain depression of pyrite flotation in the neutral pH range and at high concentration of ferrous ions, the mechanism of physisorption of a collecting agent is used. It is experimentally determined that interaction products of xanthate and ferrous ions possess different velocities of spreading over the gas–water interface depending on their concentrations and on the solution pH. Furthermore, they have different influence on the velocity of liquid removal from the interlayer between mineral particle and gas bubble. The mechanism of physisorption of a collecting agent discloses the causes of suppressed flotation of pyrite in the neutral pH zone and increased pyrite flotation in the alkaline medium.

The authors undertake a critical analysis of zinc flotation activation mechanisms, namely, ion exchange and electrochemical, and propose a new mechanism of activation of sphalerite flotation by heavy metal ions. Flotation can be activated by physisorption of the collector in the unit event of particle–bubble attachment. The causes of floatability of sphalerite activated by lead ions in the alkali range of pH are disclosed. The characteristic of zinc as a metal–activator consists in high solvability of zinc and xanthate compounds. The conditions of improved floatability of sphalerite after its activation by zinc ions are determined.

Using the methods of mathematical modeling, changes in runoff and a related removal of nutrients from three small tributaries of the Gulf of Finland as a result of possible regional climate change in the 21st century are projected. The RCP 2.6 and RCP 8.5 are considered as climatic scenarios: these are the best and the worst scenarios in terms of environmental forcing, respectively. It is shown that the RCP 8.5 will lead to an increase in river runoff by not more than 25% relative to 2006-2015. The RCP 2.6 will result in a 6% reduction in runoff. Real climate changes are likely to follow an intermediate scenario. Consequently, the projection of the climate change consequences will be in the interval between the resulting extreme estimates, and extreme changes in the hydrological regime of the catchments of small rivers and corresponding changes in the nutrient removal should not be expected in the region under consideration.

The authors study dynamics of heavy particle attached to the surface of free air bubble in liquid. The bubble with its surface vibrations and the particle are considered as a single mechanical system with geometric constraint. It is assumed that the main forces to govern interaction of these objects are the inertia force due to surface vibration of the bubble and the capillary adhesion force. The stability conditions of particle–bubble flotation aggregate at various initial surface vibrations of the bubble and at different masses of the particle are described. The velocities of the surface vibration modes are governed by the energy of turbulent pulsations in liquid.

The authors test grinding of mining waste material to a preset grain size composition under stagewise increased destructive force and at reduced sliming. The optimized conditions are determined for disintegration of mineral and tin-bearing waste aggregates at minimized micro-size sliming. The quality of the final concentrates can be improved via mechanically activated grinding of roasting stage middlings.

The study focuses on stability of particle–bubble attachment versus the size of particles attached to bubbles, design of a flotation cell and the input energy. The main force to tear away a particle from a bubble is assumed to be the inertia force conditioned by undulation of the gas–liquid interface. It is examined how the bubble surface oscillations influence detachment of particles. The oscillation amplitude is a function of the energy dissipation rate. The energy dissipation rate is determined using the methods of computational hydrodynamics in Ansys Fluent. The calculated sizes of particles produced in frother flotation with regard to coalescence in the froth bed agree with the existing and new experimental data.

The action of the arbitrary physisorbed species of a collector at a mineral is compared with the theoretical evidence on particle–bubble attachment. The lack of the correlation between the hydrophobic behavior, characterized by the wetting angle, and the floatability of minerals, as well as the correlation between the inductance time and the mineral recovery are discussed. The causes of disagreement between the collectability sequence of xanthates, dithiophosphates and dithiocarbamates and the sequence of boost in energy of chemical bond between these reagents and cation of mineral lattice are exposed. Collectabilities of frothers and residues of the collectors are explained. The ways to increase flotation performance are shown, namely, the mineral recovery and the concentrate quality can be improved by means of adjustment of the chemisorbable /physisorbable collector ratio.

The hydrophobic property generated by chemisorbed agent influences selectivity of flotation but not always governs recovery of minerals. It is suggested to evaluate efficiency of a chemisorbed agent by two criteria. First, free surface energy reduction at the moment of local rupture of the liquid interlayer between particle and bubble. Second, displacement of the contact perimeter of three physical states of particle surface under the action of surface forces at their interface. It is found that physisorption conditions collectability of a flotation agent and recovery of a target mineral in concentrate. A physisorbed collector removes liquid from the particle-bubble interlayer. The definition of the physisorbed collector force is given and its essentiality is proved. The physisorbed collector force is effective at the gas–liquid interface rather than mineral–liquid interface, and is not selective. Selectivity of an agent is governed by the chemisorptions/physisorption activity ratio of a flotation agent.

The authors find the collecting activity criteria for slack coal flotation agents. The collectability tests used kerosene, straw oil, thermal gas oil, KETGOL and FLOTEC agents. Efficiency of these agents in slack coal flotation is determined, and the velocities of their films on water surface are found. It is found that the spreading velocities of the collecting agents are correlated with the slack coal flotation performance. The article proposes a new concept of particle–bubble attachment and the floatability criteria for slack coal flotation agents.