Properties Of Bottom Sediments Research Articles

SCIENTIFIC BASIS OF MONITORING THE BOTTOM SEDIMENTS STATE AS AN INDICATOR OF THE ENVIRONMENTAL DANGER LEVEL OF HYDROECOSYSTEMS

The work proposes a method of monitoring the condition of surface water bodies that were subject to the influence of aviation industry enterprises, by studying the contamination of bottom sediments.Using the example of petroleum hydrocarbons - specific pollutants of aviation enterprises, the author proved that bottom sediments are an integral indicator of the level of manmade pollution, an indicator of the ecological safety level of hydroecosystems. The calculated coefficients of bottom accumulation indicate the progressive pollution of the reservoir and the accumulation of the main mass of pollutants in the bottom sediments. The results of studies of the small river, that flows along the airline, show that the bottom sediments belong to the category of “extremely polluted”. The structural and functional properties of bottom sediments enable us to state that, on the one hand, they contribute to the process of self-purification of the water environment by accumulating oil products, but on the other hand, bottom sediments represent a danger to the water column secondary pollution, since when physical and chemical conditions change, pollutants from the bottom sediments can pass into the water masses of the reservoir.

Coupled-Mode Parabolic Equations for the Modeling of Sound Propagation in a Shallow-Water Waveguide with Weak Elastic Bottom

In this work, a mode parabolic equation method with interacting modes accounting for the weak elasticity at the bottom is developed. An important feature of the proposed method is that computations of elastic modes are avoided and that the solution is obtained in the form of expansion over acoustic modes. A numerical technique for solving resulting mode parabolic equations is developed, and the accuracy and efficiency of the resulting solution is validated by a direct comparison against source image solutions in the 3D wedge benchmark problem. Satisfactory agreement of the two solutions is achieved for sufficiently small values of shear wave speed that are typical for soft sediments of the sea bottom. The developed approach may be used for solving 3D problems of sound propagation with the elastic properties of bottom sediments taken into account.

The effect of physicochemical properties of bottom sediments on nitrogen and phosphorus sorption

River and reservoir bottom sediments are characterized by their physical and chemical properties, which affect the quality of water and deposited sediments in reservoirs. The grain composition of sediments is their fundamental property that determines the detachment, transport and sedimentation of sediments. In addition to understanding the dynamics of transport and distribution of particles in the watershed, the granularity is closely related to the mineral and chemical composition of the sediment and plays an important role in terms of its ability to bind contaminants. Other important property of sediment includes the specific surface area, which determines the nature of sediment surface reactions and influences ecosystem level, biological processes.This study investigates sediment properties, including physical properties such as grain-size distribution, specific surface area, organic matter and chemical composition, and their reflections on nitrogen and phosphorus adsorption by the sediments deposited in the small water reservoir. The results clearly indicate the dependence of the content of nutrients (nitrogen and phosphorus) in reservoir sediments on their grain size and specific surface area.

Immobilisation of metals from bottom sediments using two additives and thermal treatment

A major problem associated with the land-based management of bottom sediments is their contamination with metals. The aims of the study were: 1) to use two additives for the immobilisation of metals; and 2) to evaluate the effect of three combustion temperatures on metal content and bottom sediment properties. The mixtures were prepared using contaminated bottom sediment and the following waste materials: cellulosic waste and biomass ash. In the second experiment, the bottom sediment samples were subjected to a thermal process, and three temperatures were chosen 500/800/950 °C. Overall, the addition of cellulosic waste and biomass ash to acidic, metal-contaminated bottom sediments significantly improved the properties of the resulting mixtures, including an increase in the pH value, sorption capacity, macronutrient content, and a decrease in the content and mobility of metals (Cd, Zn, Pb, Cr). The study confirmed the effectiveness of the thermal process on a significant reduction in the ecotoxicity of the sediments, a reduction in total content of elements, and a decrease in their leachability, and thus mobility, with increasing process temperature. The study results revealed that the converted contaminated bottom sediments can be effectively managed, provided that further studies on their technical application are carried out.

Quality of Bottom Sediments of Sołtmany Lake (Masurian Lake District, Poland) in the Light of Geochemical and Ecotoxicological Criteria—Case Study

The quality of bottom sediment is important for the condition of aquatic environments. High levels of potentially harmful components in sediments negatively affect the quality of surface water environments. Lake bottom sediments are commonly used to control the quality of the environment in terms of both heavy metals and harmful organic compounds. This paper presents new data on the compositions of bottom sediments from Sołtmany Lake, located in the Masurian Lake District (Poland). The aim of this study was to determine the physicochemical properties of bottom sediments and to assess their quality based on geochemical and ecotoxicological criteria. The field study was conducted in July 2021. Thirty sediment samples were collected for analysis from six study sites located in the upper central and lower part of the reservoir. Contamination of the bottom sediments with trace metals was determined on the basis of the geoaccumulation index (Igeo), while an ecological risk assessment was carried out on the basis of calculated values of TEC (Threshold Effect Concentration) and PEC (Probable Effect Concentration) indices. The study shows that the concentration of trace metals in sediments was characterised by slight variation and that the maximum values did not exceed: 1.1 mg·kg−1 for Cd, 8.7 mg·kg−1 for Cr, 10.9 mg·kg−1 for Cu, 7.7 mg·kg−1 for Ni, 12.9 mg·kg−1 for Pb and 52.3 mg·kg−1 for Zn. The analyses further showed that the concentration of trace elements in the sediment surface layer increased in the following order: Zn > Pb > Cu > Ni > Cr > Cd. The maximum pH value of H2O was 7.1, while that of KCl was 7.0. The maximum values of Corg, Ntot, P2O5, K2O and Mg were, respectively: 6.1 g·kg−1, 1.4 g·kg−1, 40.2 mg·100 g−1, 31.2 mg·100 g−1 and 35.1 mg·100 g−1. The assessment of the degree of lake pollution is essential for the conservation of biodiversity and the organisation of environmental management activities.

Physicochemical Properties of Bottom Sediments in Maruba Dam Reservoir, Machakos, Kenya

Bottom sediments form an integral part of the aquatic ecosystem, where they serve as important sinks for contaminants. However, management options for bottom sediments require an analysis of the physical and chemical properties. Therefore, the aim of this study was to assess the physicochemical properties of bottom sediments in the Maruba dam reservoir in order to inform their potential use. The bottom sediments were obtained from three sampling points using a vibe-coring device. The samples were analyzed for grain size, sediment bulk density, pH, electrical conductivity, organic matter content, and nutrient content (nitrogen, phosphorous, and potassium) using standard laboratory procedures. The results of the study revealed that the bottom sediments were predominantly clay (56%). The mean pH value of the sediments was 6.63, which was found to be slightly acidic. The concentration of cations and anions in the bottom sediments was found to be quite high, with a mean value of 0.225 dS⋅m−1. The bottom sediments in the reservoir were found to be quite rich in the organic matter content (2.10%) and had a mean bulk density of 0.620 g·cm−3. The macronutrients (nitrogen, potassium, and phosphorous) had mean values of 0.12%, 0.46%, and 12.81 mg·kg−1, respectively. The study established that finely grained particles together with organic matter had a potential effect on the availability of macronutrients in bottom sediments. The concentration of the macronutrients of the bottom sediments evaluated in this study points to their potential use in agricultural activities or even in land reclamation.

Investigating the correspondence of acoustic amplitudes with penetrometer profiles in bottom sediments of a shallow coastal lake: Louisiana

This study correlates side-scan sonar and CHIRP subbottom acoustic amplitudes with cone penetrometer data to expand the limited understanding of the geotechnical properties of sediments in coastal Louisiana's bays. Using cone penetrometer profiles is a methodology for characterizing the sediment properties of the water bottoms and shallow subsurface sediments of coastal water bodies. This study is the first in Louisiana to investigate the potential value of applying this methodology combined with both side-scan sonar images and CHIRP subbottom amplitude analysis to the sediment characteristics of coastal bay bottoms. Penetrometer results demonstrate the sediment-related variability in the shallow subsurface of Sister Lake, in south-central Louisiana, with the majority of tip resistance values under 98.0 kPa (1.0 kg/cm2), with peaks to approximately 686.5 kPa (7.0 kg/cm2). An amplitude analysis technique identified different reflectance regions within Sister Lake from the CHIRP subbottom profile data. Acoustic reflectance is related to sediment “hardness” or resistance. The side-scan sonar and CHIRP amplitude reflectivity results are compared to penetrometer data that quantifies geotechnical properties of surface and near-surface sediments. Insight into the relative hardness of the coastal lake bottom and shallow subsurface deposits is gained through this technique, useful for: (a) identifying areas of erosion (previously buried and consolidated sediments) versus recent deposition; (b) delineating hard bottom areas suitable for cultch plants for state oyster seed grounds; and (c) informing the parameterization, calibration, and validation of numerical models used for predicting the response of coastal systems to future environmental conditions and restoration efforts. Results indicate three distinct penetrometer, side-scan and CHIRP signatures that identify different water bottom and substrate areas within Sister Lake including: 1) clay to organic clay; 2) silt to sand; and 3) oyster cultch and scattered shell. Although amplitude levels of high-resolution acoustic data do not directly quantify the geotechnical properties of bottom sediments, results indicate a close relationship. The analysis procedures developed in this study can be applied in other dynamic aquatic coastal environments by “calibrating” the use of synoptic acoustic methods for large spatial-scale water bottom characterization.

In-situ temperatures and thermal properties of the East Siberian Arctic shelf sediments: Key input for understanding the dynamics of subsea permafrost

Significant reserves of methane (CH4) are held in the Arctic shelf, but the release of CH4 to the overlying ocean and, subsequently, to the atmosphere has been believed to be restricted by impermeable subsea permafrost, which has sealed the upper sediment layers for thousands of years. Our studies demonstrate progressive degradation of subsea permafrost which controls the scales of CH4 release from the sediment into the water-atmospheric system. Thus, new knowledge about the thermal state of subsea permafrost is crucial for better understanding of the permafrost -hydrate system and associated CH4 release from the East Siberian Arctic Shelf (ESAS) – the broadest and shallowest shelf in the World Ocean, which contains about 80% of subsea permafrost and giant pools of hydrates. Meanwhile, the ESAS, still presents large knowledge gaps in many aspects, especially with respect to subsea permafrost distribution and physical properties of bottom sediments. New field data show that the ESAS has an unfrozen (ice-free) upper sediment layer, which in-situ temperature is −1.0 to −1.8 °C and 0.6оС above the freezing point. On one hand, these cold temperature patterns may be related to the presence of subsea permafrost, which currently primarily occurs in the part of the ESAS that is shallower than 100 m, while ice-bearing sediments may also exist locally under deeper water in the Laptev Sea. On the other hand, the negative bottom sediment temperatures of −1.8 °C measured on the Laptev Sea continental slope sediments underlying water columns as deep as down to 330 m may result from dissociation of gas hydrates or possibly from dense water cascading down from the shelf. In contrast, data collected on recent expeditions in the northern Laptev shelf, zones of warmer bottom temperatures are coinciding with methane seeps, likely induced by seismic and tectonic activity in the area. These warm temperatures are not seen in the East Siberian Sea area, not even in areas of methane seeps, yet with little seismic activity.The thermal conductivity and heat capacity of bottom sediments recorded in the database of thermal parameters for the ESAS areas mainly depend on their lithification degree (density or porosity), moisture content, and particle size distribution. The thermal conductivity and heat capacity average about 1.0 W/(m·K) and 2900 kJ/(m3·K), with ±20% and ±10% variance, respectively, in all sampled Arctic sediments to a sub-bottom interval of 0–0.5 m.

Оценка радиационной обстановки в районе расположения АО «ГНЦ НИИАР» до начала эксплуатации ИЯУ МБИР. Часть 2. Водные экосистемы

The analysis of the radiation survey results of freshwater ecosystems of three rivers and the Cheremshansky Bay of the Kuibyshev Reservoir in the vicinity of State Scientific Centre “Research Institute of Atomic Reactors” (SSC RIAR, Institute) before the start of the MBIR fast neutron reactor operation was carried out. The content of natural (K-40, Ra-226, Th-232) and artificial (Sr-90, Cs-137) radionuclides in the main components of freshwater ecosystems: surface and underground waters, bottom sediments, floodplain soils and vegetation, and ichthyofauna was estimated. It has been shown that the specific activity of Cs-137 in the waste water of industrial storm sewerage (PLK-1) of the enterprise is 10-70, Sr-90 2-10 times higher compared to the surface waters of reservoirs of its zone of influence. This is due to the removal of radionuclides from the site of local contamination in the sanitary protection zone of SSC RIAR. In Cheremshansky Bay, downstream, the concentration of radioisotopes decreases by 8-50 times due to dilution processes and their sorption by bottom sediments and hydrobionts. It is noted that the sorption properties of bottom sediments are determined by the presence of organic compounds in their composition. The multidirectional nature of the accumulation of artificial radionuclides in floodplain soils and plants is shown. In some cases, it is determined by the distance from the source of gas-aerosol emissions of radioisotopes and affects the secondary pollution of freshwater ecosystems. Monitoring data demonstrate a stable decrease in the content of artificial radionuclides in surface waters. In Cheremshansky Bay in 2005-2020 for Cs-137 it was 5 times, for Sr-90 it was 3 times. It has been noted that in recent years, the specific activity of artificial radionuclides in sewage of SSC RIAR, surface and underground waters, as well as fish in the zone of enterprise influence is at the level of the regional background and is 1-3 orders of magnitude lower than the current radiological standards. The importance of further radioecological monitoring of freshwater ecosystems in the SSC RIAR location area after the commissioning of the MBIR for assessing the impact of the new reactor on humans and the environment is shown.

The influence of the physicochemical properties of sediment on the content and ecotoxicity of trace elements in bottom sediments

The sorption mechanisms of the trace elements in bottom sediment are not fully understood. The study aim was to analyse the effect sorption capacity of bottom sediments on the content of trace elements and the bottom sediment ecotoxicity. The study found higher content of trace elements caused higher potential toxicity of bottom sediments. However, the PCA analysis indicated that ecotoxicity to Heterocypris incongruens was not related to the trace element content in the sediments. It was found that some of the physicochemical properties of bottom sediments determine the behavior of the test organism. The study revealed a strong relationships between the properties of bottom sediments and trace element sorption, which results from significant differences in the carbonate and organic matter contents. The obtained relationships showed a significant role in trace element sorption of negatively dissociating functional groups (carboxyl, phenolic, alcohol, and carbonyl groups) of Cha, Cfa, Cnh and DOC fraction and of clay minerals. Positive correlation between the metal content and the volume of ultramicropores, cryptopores and residual pores suggest that these pore groups contain reactive sites capable of effective element sorption. In contrast, larger pores turned out to be of marginal importance in trace elements sorption, probably participating only in their migration within the bottom sediment structure. An understanding of the above factors will provide comprehensive information on the fate of trace elements in aquatic systems.

Stages and staging of the study of the seabed for earthmoving systems

The development and development of minerals and building materials in water areas, the laying of underwater communications, planning and dredging underwater are preceded by detailed surveys of soil massifs. They establish the lithology and genesis of deposits, bottom surface bathymetry, physicomechanical, acoustic and other properties of underwater soils. These studies are mainly subordinated to the tasks of geology. At the same time, for the development of the deep-water part of the World Ocean, it is planned to use soil development and transport equipment. The kinematic parameters of the equipment used for engineering and geological research do not correspond to the kinematics of existing or planned underwater systems. Despite some progress in the development of engineering-geological methods for studying the ocean, there are currently no reliable data on the mechanical properties of bottom sediments in natural occurrence. Practically the only way to identify the strength properties of deep-water soils is the sampling method (tubes, grabs, dredges). Soil characteristics are determined from samples brought to the surface in a shore or ship laboratory.
 One of the specific features of the tests being carried out is the consideration of hydrostatic pressure, the effect of which on three-phase soils is especially large. Therefore, it should be expected that the measurement errors of the characteristics of bottom sediments in atmospheric conditions due to the violation of their structural relationships during ascent from great depths can differ by an order of magnitude or more from the true values ​​of the parameters of the soil environment. Thus, in order to determine the operating conditions and set external loads on underwater digging machines, it is necessary to measure the strength, deformation and other characteristics of bottom soils in natural conditions under hydrostatic pressure. This paper considers the methods and technical means used for deep-sea exploration of the seabed. Particular attention is paid to engineering-geological methods, which make it possible at the stage of detailed exploration to obtain not only predictive estimates of the mineral resources of the World Ocean but also to determine the physical and mechanical properties of bottom sediments, on which deep-sea digging machines will have to work.

Sedimentation dynamics within a large shallow lake and its role in sediment transport in a continental-scale watershed

A comprehensive understanding of the sedimentation dynamics within Lake Winnipeg (surface area: 23,750 km2) and its role in sediment transport in the downstream river system was achieved by determining the properties of lake bottom sediment and patterns of sediment accumulation rates and by constructing a conceptual total (i.e., organic and inorganic) sediment budget. Net deposition was the governing process in the South and North Basins, whereas transportation dominated in the Narrows. The largest fluvial source of sediments to the lake, the Red River, supplies 35% of the total sediment load. Although accumulation rates in profundal zones progressively decreased northward from this source at the south end of the lake, high accumulation rates with low inventories of fallout radionuclides in the northern margin of the North Basin indicate a second sediment source, which was determined to be erosion of north shore banks, which accounts for up to 50% of the total sediment load to the lake. The nearshore-offshore gradient in bottom sediment properties in the North Basin confirmed that the signature of this source can reach at least 20 km southward into the lake. However, the properties of bottom sediments, sedimentation dynamics, and sediment budget suggested that some of the materials eroded from the north shore are exported without interaction with the lake bottom and this local sediment source is the dominant source for the downstream river system. It was concluded that Lake Winnipeg effectively disconnects the downstream Nelson River from sediment transport processes in its upstream watershed (953,250 km2).

Experimental laboratory complex for studying the physical properties of artificially formed gas-hydrate-containing sediments

Physical properties of gas hydrate-containing sediments (HCS) are extremely important information for the development of methods for their search and exploration. The presence of gas hydrates in marine bottom sediments significantly changes their physical properties, so they can be detected by marine remote geophysical observations. The physical properties of HCS are very important for detecting the presence of these compounds, estimating the amount of captured gas hydrates by sediments, as well as developing methods for using this resource. Currently, the study of physical properties concerned mainly artificial gas hydrates in the process of formation and decomposition under various thermodynamic conditions in their pure form. Therefore, very little is known about the physical properties of HCS, which makes their detection by remote geophysical surveys too difficult. Development and creation of experimental laboratory modular complex for formation of artificial methane gas hydrates in various lithological-granulometric matrices (sandstones, argillites, siltstones, etc.) and measurement of their physical properties in thermodynamic conditions of bottom sediments of the Black Sea, will increase efficiency technology of methane hydrate deposits development. Under experimental conditions, along with the thermal conductivity and velocities of longitudinal and transverse waves of artificial HCS, the parameters of elastic deformation, strength, and decay characteristics will be measured, which will allow performing theoretical analysis to build models based on different hypotheses of their genesis. At the S.I. Subbotin Institute of Geophysics of the National Academy of Sciences of Ukraine created a model of the installation for the formation and study of the physical properties of HCS. The development is based on the modern technological level of research in the field of thermobaric petro- physical experimental modeling of geological environments, as well as on the use of modern software and hardware laboratory research to obtain physical properties of bottom sediments of various lithological and particle size distribution.

A New Approach to Estimation of the Rheological Properties of Seafloor Sediments during the Sampling Process

This paper is devoted to the problem of studying the rheological properties of seafloor sediments during the sampling process with the use of a gravity corer. The problem of gravity corer penetration through the soil with a complicated visco-elasto-plastic rheology is considered. Estimation of the mechanical properties of bottom sediments is among the most important problems emerging during the exploration of the hydrocarbon fields located on the Arctic shelf. Proper evaluation of the reaction of infrastructure objects to external effects (earthquakes, large waves) is needed to reduce the risks of serious accidents on the shelf. This paper presents a new approach to determining the parameters governing the stability of the infrastructure: static elastic moduli of seafloor sediments and their plastic and viscous properties. The dynamics of gravity corer penetration, with a measurable dependency of its acceleration, acts as a source of information regarding these parameters. The inverse problem of reconstructing the mechanical properties of seafloor sediments from the characteristics of this dependency has to be solved. This paper presents the results of solving the corresponding direct problem with the use of the finite element method. The possibility to estimate the mechanical properties of seafloor sediments from data on parameters such as time passed until the complete cessation of the tube sampler and the depth of its penetration is demonstrated.

Sedimentation rate and physical properties of bottom sediments in the Angara reservoirs under the cyclical conditions of the level regime

Research subject. The article presents the results of a study of sedimentation rate and physical properties of bottom sediments in the Angara reservoirs under controlled level regimes. Materials and methods. The work was based on the materials of fieldwork carried out by the author on the Angara reservoirs in 1972–2017 and open-access literature sources. The physical properties and particle size distribution of bottom sediments were determined by the standard methods of engineering geology. Results. It was found that the controlled level regime determines the time cycles of sedimentation in reservoirs, sources of sediment-forming material, sedimentation rate and ambiguity of the physical properties of bottom sediments. Conclusions. During transgressions, sands, coarse aleurites and fine-aleurite silts accumulate in reservoirs most intensively; however, during regressions, coarse aleurites and aleurite-clayey silts are accumulated. During transgressions, all types of sediments are characterised by the highest sediment density, sediment skeleton density and absorption capacity, while coarse aleurites and fine-aleurite silts exhibit high natural humidity levels. In addition, coarse aleurites are characterised by a high porosity, while fine-aleurite and aleurite-clayey silts are characterised by a high content of organic matter. During regressions, the porosity of sands, fine-aleurite and aleurite-clayey silts increases, the content of organic matter in sands and coarse aleurites increases, and all types of sediments become more saturated with carbonates.

Study of Bottom Sediments of the Chiryurt Reservoir, Dagestan, Russia with a View to their Utilisation in Land Reclamation following Anthropogenic Interference

Aim. To study the physicomechanical and physicochemical properties of bottom sediments of the Chiryurt Reservoir, Kizilyurtovskiy District, Republic of Dagestan, Russia with a view to their possible utilisation as building materials for the production of certain grades of concrete and road asphalt-concrete, as well as for the preparation of soil substrate and as additives to potassium and phosphate mineral fertilizers. Material and Methods . The bottom sediments of the Chiryurt Reservoir, taken from different depths and different reservoir locations, were studied by spectrophoto-metric and granulometric methods. Results. The study identified: particle size distribution of samples of bottom sediments; humus content; soil fertility elements: potassium, nitrogen, phosphorus as well as heavy metal content. Conclusions: 1. Analysis of the bottom sediment samples indicates that the soil fertility elements potassium, nitrogen, phosphorus are not sufficient for them to be used as an independent fertilizer, although they might perhaps be used as an auxiliary additive to a principal fertilizer. The levels of toxicity of heavy metals were found to be very low - much lower than the Maximum Allowable Concentrations. 2. The sediments could be used as soils for the reclamation of land after anthropogenic interference (e.g. after a quarry has been excavated for brick production, after excavations during road construction of roads), for the modification of vertical terrain in settled areas, for landscaping, etc. 3. According to the granulometric analysis of the material composition of the samples, the bottom sediments are 85-90% composed of clay particles (thus there is no need to undertake procedures to separate out the sand fraction). 4. Since peat deposits are present in the bottom sediments of the reservoir, it makes sense to separately assess their volumes for independent development for use as fertilizer for the re-cultivation of floodplain lands.

Estimation of Elastic Stress-Related Properties of Bottom Sediments via the Inversion of Very- and Ultra-High-Resolution Seismic Data

This paper provides an overview of several seismic inversion approaches and their application to very- and ultra-high-resolution marine seismic datasets. The importance of seismic inversion is related to the current demands of the offshore engineering industry for estimates of elastic stress-related parameters of near-surface and bottom sediments. To meet these demands, the seismic inversion methods which facilitate the estimation of elastic properties of the subsurface should be developed for very high-resolution data. Several problems prevent the successful application of seismic inversion to high-resolution datasets. Firstly, borehole measurements, which are routinely applied to constrain seismic inversion, are often not available for the offshore near-surface. Secondly, very- and ultra-high-resolution seismic data are acquired in high frequency ranges, and low-frequency information is absent in such datasets. The elaboration of seismic inversion methods for ultra-high-resolution data is important for both practical and scientific purposes. In the paper, we share our experience in applying acoustic poststack inversion and prestack AVA inversion to very- and ultra-high-resolution marine seismic datasets.

SEM Study of the Magnetic Fraction in Bottom Sediments of Lakes of the Southern Urals

Features of the sedimentation of lakes Bolshoi Kisegach and Turgoyak (Southern Urals) are described by studying the magnetic fractions and magnetic properties of bottom sediments via scanning electron microscopy. The magnetic fraction of lacustrine sediments consists of authigenic and allothigenic minerals.

Composition and physico-chemical properties of bottom sediments in the southern part of the Bratsk Reservoir (Russia)

The paper presents the results of studies of bottom sediments taken from the southern part of the Bratsk Reservoir. The following analyses have been conducted: trace element analysis, particle-size analysis as well as chemical analysis of water, hydrochloric acid and alkaline extracts for 18 samples of the bottom sediments. The granulometric analysis has identified the predominance of fine silt and silty-clayed sediments. The data on the content of trace elements in the bottom sediments of the Bratsk Reservoir is presented in comparison with their content in the natural environment of the Baikal region; the anomaly ratio was used to characterize the excess for trace elements. The chemical analysis of extracts has showed “saline contamination” of mud (silt), high concentration of carbonates in it, as well as the presence of mobile (free) forms of aluminum oxide. In this research, an attempt was made by using a correlation analysis to evaluate the impact of various physical and chemical characteristics of the bottom sediments, such as the content of clay fraction, organic carbon, carbonates, and water-soluble salts on the accumulation of trace elements.

Physical and chemical properties of bottom sediments in surface waters of Central and South Vietnam

In this study, physical and chemical characteristics of bottom sediments in inland waters of Central and Southern Vietnam were investigated, initially according to granulometric compositions, organic matter contents, bulk densities, and natural moisture contents. The main types of sediments in rivers, lakes, reservoirs, former quarries, and ponds were then identified, and similarities between of physical and chemical properties were identified between bottom sediments from water bodies of Vietnam and those from the Volga cascade reservoirs. Moreover, we show common dependencies in the formation of bottom sediments in reservoirs from humid, arid, and tropical monsoon climates.