Distribution Of Bottom Sediments Research Articles

Authigenic Minerals of the Derbent and South Caspian Basins (Caspian Sea): Features of Forms, Distribution and Genesis under Conditions of Hydrogen Sulfide Contamination

This paper presents the results of complex lithological, mineralogical, and geochemical studies of bottom sediments of deep-water basins of the Caspian Sea (Derbent and South Caspian Basins) in areas contaminated by hydrogen sulfide. In the course of complex studies, numerous manifestations of authigenic mineral formation associated with the stage of early diagenesis have been established. Authigenic minerals belonging to the groups of sulfates (gypsum, barite), chlorides (halite), carbonates (calcite, low Mg-calcite; kutnohorite), and sulfides (framboidal pyrite), as well as their forms and composition, have been identified by a complex of analytical methods (X-ray diffractometry (XRD), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS); atomic absorption spectroscopy (AAS); coulometric titration (CT)); the nature of their distribution in bottom sediments has been assessed. Carbonates and sulfates are predominant authigenic minerals in the deep-water basins of the Caspian Sea. As a part of the study, differences have been established in the composition and distribution of associations of authigenic minerals in the bottom sediments in the deep-water basins. These are mineral associations characteristic of the uppermost part of the sediments (interval 0–3 cm) and underlying sediments. In the Derbent Basin, in sediments of the interval 3–46 cm, an authigenic association is formed from gypsum, calcite, magnesian calcite, siderite, and framboidal pyrite. An association of such authigenic minerals as gypsum and calcite is formed in sediments of the 0–3 cm interval. In the South Caspian Basin, in sediments of the interval 3–35 cm, an association of such authigenic minerals as gypsum, halite, calcite, magnesian calcite, and framboidal pyrite is formed. The association of such authigenic minerals as gypsum, halite, calcite, magnesian calcite, kutnohorite, and framboidal pyrite is characteristic of sediments of the 0–3 cm interval. We consider the aridity of the climate in the South Caspian region to be the main factor that determines the appearance of such differences in the uppermost layer of sediments of the basins. Judging by the change in the composition of authigenic associations, the aridity of the South Caspian increased sharply by the time of the accumulation of the upper layer of sediments (interval 0–3 cm). Taking into account lithological, mineralogical and geochemical data, the features of the processes of authigenic mineral formation in the deep-water basins of the Caspian Sea under conditions of hydrogen sulfide contamination have been determined. Analysis of the results obtained and published data on the conditions of sedimentation in the Caspian Sea showed that hydrogen sulfide contamination recorded in the bottom layer of the water column of the deep-water basins of the Caspian Sea may affect the formation of authigenic sulfides (framboidal pyrite), sulfates (gypsum), and carbonates (calcite and kutnohorite) associated with the activity of sulfate-reducing bacteria in reducing conditions.

Forms of transfer of microelements in river network and their distribution in bottom sediments in coal mining regions

Forms of transfer of microelements in river network and their distribution in bottom sediments in coal mining regions

Геоморфологические аспекты преобразования крупного равнинного водохранилища (по данным измерений на Краснодарском водохранилище)

The article considers the results of the analysis and generalization of the materials of bathymetric surveys of the Krasnodar reservoir in 2005, 2016 and 2021. The Krasnodar reservoir occupies a key position in the Kuban reclamation complex, so its transformations caused by siltation cannot be underestimated. Special attention is paid to the geomorphological aspects of the transformation of the reservoir bed in the process of siltation, which directly affects the morphometric characteristics of the reservoir. According to a series of bathymetric surveys, digital elevation models of the basin and maps reflecting the distribution of bottom sediments and the processes of morpholithogenesis of the bed were constructed. During the period 2005–2021, the volume of sediment accumulation in the main reservoir, excluding the separated Tcshikskoe reservoir and deltaic sediments of the dividing bridge, amounted to 127 million m³. The greatest contribution to geomorphological transformations is made by fluvial processes, with the participation of which deltas of rivers flowing into the reservoir (Kuban, Belaya, Pshish, etc.) and estuarine avandeltas are formed. So, for 2016–2021. within the mouth of the Kuban seashore, the volume of sediments amounted to 9.36 million m³ or 38 % of the total volume of the siltation body in the reservoir, and the increment of the siltation layer over 5 years reached 2–3 m or more. Within the zone of variable backwater in the open part of the water area, bottom sediments are distributed relatively evenly with an increment of the sediment layer over 5 years of 0.01–0.4 m. The lowest rates of sediment layer increment were observed in the dead volume zone—less than 2 cm per year. During the study period, a decrease in the average annual volume of situation was recorded, which presumably indicates a gradual attenuation of the siltation process as the volume of the reservoir decreases.

Reconstruction of the Long-Term Dynamics of Particulate Concentrations and Solid–Liquid Distribution of Radiocesium in Three Severely Contaminated Water Bodies of the Chernobyl Exclusion Zone Based on Current Depth Distribution in Bottom Sediments

Given the importance of understanding long-term dynamics of radionuclides in the environment in general, and major gaps in the knowledge of 137Cs particulate forms in Chernobyl exclusion zone water bodies, three heavily contaminated water bodies (Lakes Glubokoe, Azbuchin, and Chernobyl NPP Cooling Pond) were studied to reconstruct time changes in particulate concentrations of 137Cs and its apparent distribution coefficient Kd, based on 137Cs depth distributions in bottom sediments. Bottom sediment cores collected from deep-water sites of the above water bodies were sliced into 2 cm layers to obtain 137Cs vertical profile. Assuming negligible sediment mixing and allowing for 137Cs strong binding to sediment, each layer of the core was attributed to a specific year of profile formation. Using this method, temporal trends for particulate 137Cs concentrations in the studied water bodies were derived for the first time and they were generally consistent with the semiempirical diffusional model. Based on the back-calculated particulate 137Cs concentrations, and the available long-term monitoring data for dissolved 137Cs, the dynamics of 137Cs solid–liquid distribution were reconstructed. Importantly, just a single sediment core collected from a lake or pond many years after a nuclear accident seems to be sufficient to retrieve long-term dynamics of contamination.

Reconstruction of time changes in radiocesium concentrations in the river of the Fukushima Dai-ichi NPP contaminated area based on its depth distribution in dam reservoir's bottom sediments

Radionuclide depth distribution in bottom sediments in deep-water zones of dam reservoirs, where no sediment mixing occurs, can be used to reconstruct time changes in particulate activity concentrations of radionuclides strongly bound to bottom sediments. This approach was used to analyze the 137Cs concentration profile in a bottom sediment core collected from Ogaki dam reservoir on the Ukedo River in the Fukushima Dai-ichi nuclear power plant contaminated zone in October 2019. The derived 137Cs particulate concentrations provided a basis for estimating the dissolved concentration and its temporal trend in the Ukedo River, using the mean value of the apparent 137Cs distribution coefficient. The reconstructed particulate and dissolved 137Cs concentrations and their temporal trends are consistent with monitoring data. The annual mean particulate and dissolved 137Cs wash-off ratios were also calculated for the period of eight years after the accident. Interestingly, the particulate 137Cs wash-off ratios for the Ukedo River at Ogaki dam were found to be similar to those for the Pripyat River at Chernobyl in the same time period after the accident, while the dissolved 137Cs wash-off ratios in the Ukedo River were an order of magnitude lower than the corresponding values in the Pripyat River. Both the particulate and dissolved 137Cs wash-off ratios in the Ukedo River declined faster during the first eight years after the FDNPP accident than predicted by the diffusional model, most likely, due to greater natural attenuation and, to some extent, remediation measures implemented on the catchments in Fukushima.

Spatial distribution of bottom sediments of the near-dam ples of Kuibyshev Reservoir

The composition of bottom sediments and the patterns of their spatial distribution are determined by external (type of underlying surface of the catchment area, anthropogenic development, intensity of soil erosion) and internal (water regime, intensity of water exchange, morphometry of the basin) factors. The analysis of the granulometric composition of the bottom sediments of the near-dam ples of the Kuibyshev Reservoir showed the relative uniformity of the ples soil in terms of size. At the same time, depending on the location of the sampling points, certain patterns of distribution of the size of bottom sediments in space are traced.

Anoxic in situ production of bacterial GMGTs in the water column and surficial bottom sediments of a meromictic tropical crater lake: Implications for lake paleothermometry

Branched glycerol monoalkyl glycerol tetraethers (brGMGTs) are membrane-spanning lipids which were initially identified in marine settings and have more recently been found in peats and lake sediments. In the latter settings, their abundance relative to that of the branched glycerol dialkyl glycerol tetraethers (brGDGTs) appears to increase under warmer climate conditions. Furthermore, their relative distribution in bottom sediments from an altitudinal transect of East African lakes has been linked to local mean annual air temperature (MAAT). To shed light on their sources and identify potential environmental factors driving their production in lakes, we investigated their occurrence and distribution in the water column, surficial lake-bottom sediments, and catchment soils of Lake Chala, a permanently stratified (meromictic) tropical crater lake in East Africa. Data from the water column comprise both suspended particulate matter (SPM) collected monthly at eight depth intervals between 0 and 80 m for 17 consecutive months, and settling particles collected monthly at a depth of 35 m over a period of 53 months. In catchment soils, brGMGTs are either relatively scarce or absent. In the water column, their occurrence is dominated by four of the seven known brGMGTs and mostly limited to the anoxic zone. Whereas the spatial distribution and concentration of brGMGTs in SPM were strongly influenced by the seasonal cycle of strong water-column stratification alternating with deep mixing, this trend is not consistent on the multi-year timescale of the settling-particles record. Moreover, their relative distribution in both SPM and settling particles did not respond to temperature variation during the studied interval. In contrast to the water column, surficial lake-bottom sediments contain the full suite of known brGMGTs in a distinct and spatially uniform fractional abundance, strongly suggesting that the majority of brGMGT production takes place there. BrGMGT-inferred MAAT for the Chala area reasonably estimates measured MAAT and conforms to the East African lake brGMGT calibration. Our results have important implications for the use of brGMGTs as proxy for MAAT, in that outside of the equatorial zone the presumably greater offset between bottom-water temperature and MAAT may create a bias towards cold-season air temperature. Regardless, the more singular source of brGMGTs in lake sediments is an advantage for paleotemperature reconstruction compared to brGDGTs, which several studies now indicate to have a mixed aquatic and terrestrial source of which the relative contribution cannot easily be disentangled or assumed to have been constant through time.

Modeling of 14C Vertical Distribution in Bottom Sediments of the Ignalina Nuclear Power Plant Cooling Reservoir

The Ignalina Nuclear Power Plant (INPP) in Lithuania is a rare case when lake water is used instead of river or sea water for cooling. Lake Drūkšiai with water residence time of 3–4 year and undisturbed sediment layers is a unique system to assess the impact of a nuclear facility on the aquatic ecosystem with a sufficiently high temporal resolution. We constructed a model of radiocarbon cycling processes in lake ecosystem which evaluates the 14C specific activity vertical distribution in two organic sediment fractions: alkali-soluble and alkali-insoluble. Model calculations proved that during the first 15 years of operation since 1983, 14C annual aqueous releases from the INPP were in water dissolved inorganic carbon form and varied in the range of 2.4 ÷ 3.7 × 108 Bq/year. The results of the modeling of hypothetic scenarios also showed that there was the only one episode of elevated releases from the INPP in 2000–2001, which changed the interaction between the two organic sediment fractions for the period of 2000–2006. It was caused most probably by released chemicals from INPP but not by 14C contamination. Interaction processes between both sediment fractions recovered to its original state after 2006, indicating that the released additional chemical compounds lake ecosystem have been cleaned-up.

Comparison of methane distribution in bottom sediments of shallow lagoons of the Baltic and Black Seas

Comparison of methane distribution in bottom sediments of shallow lagoons of the Baltic and Black Seas

Oceanographic and environmental characteristics of a coupled coastal bay system: Baía de Ilha Grande-Baía de Sepetiba, Rio de Janeiro, Brazil

Baía de Ilha Grande and Baía de Sepetiba are two connected coastal bays in southeastern Brazil just west of Rio de Janeiro. They are favored for tourism and recreation, provide most of the potable water for the city of Rio de Janeiro, are the site of the only two nuclear reactors in Brazil, a deep-water oil terminal, a Federal container port, and hundreds of industries. The bay system experiences mixed mainly semidiurnal tides and currents. Hundreds of sediment samples and cores plus side scan-sonar surveys were used to map the bottom sediment distribution. Long-term measurements from two moored instruments yielded two sets of time series of water level, currents, temperature, and salinity, which were used to analyze the salient ocean processes in the two bays. The temperature time series and extensive CTD profiling indicated the occurrence of cold-water intrusion events into Baía de Ilha Grande, with temperatures ranging from 16 °C to 20 °C, in spring to late summer (October–April). The intrusions are ascribed to coastal upwelling of South Atlantic Central Water as a result of synoptic northeasterly winds and the westward translation of cold core eddies and meanders from the region of Cabo Frio. The calculated mean sea level varies annually by 50 cm with a peak in June and a trough in November due to atmospheric pressure variations (5%), steric changes (28%), but mostly due to wind and Ekman effects. Spectral analysis was applied to analyze the water level and current time series. The results indicated both tidal asymmetry and the existence of a pronounced quarter-diurnal seiche oscillation in the coastal bay-system parallel to the coast.

Distribution of Bottom Sediment in Lekok Water, Pasuruan Regency, East Java

Lekok water is one of the open waters. This will greatly affect the sedimentation process in Lekok water. The purpose of this study is to examine the distribution of bottom sediments in Lekok Water, Pasuruan Regency. The study was conducted in October-November 2019 using ekman grab at 9 site points. Sediment samples were obtained then analyzed in the laboratory to determine the grain size, as well as statistical calculations to analyze the distribution of the sediment. Based on the results of the study note that sediments distributed in Lekok Water are generally dominated by three types of sediments namely: sandy loam, loam and silt loam. Sorting values are in a well-sorted to the moderately well-sorted condition where the sediment conditions are well sorted. The skewness value is skewed positively where the value indicates a positive skewed sedimentary condition. The value of kurtosis is in the leptokurtic condition where the sediment from station 1 to station 9 is homogeneous.

Ecology of Meiobenthos Inhabiting the Local Biotopes of Gas Seeps in Coastal Waters of Crimea: Taxonomic Composition and Distribution in Bottom Sediments

The present study reports results of investigation of meiobenthos from shallow-water gas seeps of Cape Tarkhankut (North-Western Crimea). The meiobenthic communities at the gas seeps have been found to be suppressed and less abundant than the zoobenthos in the surrounding seabed substrates. The density peaks of seep meiofauna are confined to the upper 0–3 cm layer, in contrast to the surrounding sands, where much more abundant meiofauna is located deeper in the sediment layer. Dominant and subdominant meiobenthic taxa are Nematoda, Foraminifera (Allogromiida), and Polychaeta. It is highly likely that among the meiofauna that was found in the seep marine sediments, there was a significant percentage of dead bodies from the surface layers, trapped inside the microbial mat because of the high growth rate of the bacterial substrate. Sulfidic seep sediments reduce the concentration of oxygen within the 1.5 m near-bottom layer. Seep sediments form specific “extreme” biotopes, where the environment rich in organic matter is combined with high concentrations of hydrogen sulfide and lack (or complete absence) of oxygen

Features of Bitumoid Distribution in Bottom Sediments of the Barents Sea

The results on the content, composition, and distribution of chloroform bitumoids (CBs) in the Holocene sediments of the Barents Sea are presented (Cruise 68 of the R/V Akademik Mstislav Keldysh, July–August 2017). Depending on the sedimentation conditions, CB concentrations varied on average (μg/g of dry mass) as follows: Novaya Zemlya Archipelago (174) > Svalbard Archipelago (131) > Western part (78) > Central part (69) > Franz Josef Land (52). Hydrocarbons comprised almost half (46% on average with the maximum of 85%) in the composition of CBs. Their distribution in the thickness of sediments is different and depends not only on the particle-size composition of sediments and the content of organic matter in them, but also on the variability of redox conditions and fluid flows of hydrocarbons from a sedimentary stratum. Therefore, markers of alkane composition and IR-Fourier spectra indicated both sedimentary (Murmansk bank, the Franz Josef Land shelf) and point oil (shelf of Svalbard Archipelago, Medvezhinskii Trench) sources of hydrocarbons.

Grain size distribution and chemistry of the brackish Lake sediment in Korea

To determine the grain size distribution and chemical characteristics of bottom surface sediments in shallow brackish lagoons, we studied sediment samples collected from the entire horizontal lake area and in vertical profiles from three stations in Lakes Youngrang and Hwajinpo, on the eastern coast of Korea. Vertical and horizontal grain size distributions of the bottom sediments indicated predominantly sand- and silt in both lakes. The vertical distribution of C/N ratios ranged from 6.14 to 11.92 in Lake Youngrang, and 6.74 to 12.34 in Lake Hwajinpo. The horizontal distribution of C/N ratios in Lake Youngrang ranged from 6.1 to 17.6, whereas they ranged from 4.4 to 12.1 in Lake Hwajinpo. C/N ratios showed locally different responses to the origin of allochthonous (partial region) and autochthonous (entire region) organic materials. Horizontally, bottom sediment with low δ<sup>13</sup>C and high δ<sup>15</sup>N in Lake Youngrang were likely to be influenced by autochthonous organic material derived from primary production, and would be affected by N inputs from sources. In contrast, high δ<sup>13</sup>C and low δ<sup>15</sup>N sediments in Lake Hwajinpo were likely to be influenced by cyanobacteria.

Mercury and other heavy metals in the bottom sediments of Lake Loshamye (national park “Smolensk Lakeland”)

In 2008–2010, monitoring work in the national park «Smolensk Lakeland» showed an excess of mercury in the water of Lake Loshamye located in the protected area of the natural reserve. In 2014–2019, together with the staff of the national park, we studied the ecological and geochemical features of the catchment area and the water area of Lake Loshamye. We studied the patterns of distribution of several heavy metals: Hg, Cr, Mn, Fe, Co, Cu, Zn, As, Cd, Pb, Sr. We did not find an anthropogenic influence on the catchment area; this article presents the results of the study of the bottom sediments of the lake. As a result of the work, we determined that all heavy metals have a natural distribution in this lake, except mercury. High values of mercury in bottom sediments (up to 1000 ppb) are not typical for such natural object. The median of the sample is 152 ppb, and it is four times higher than expected mercury content considering its content in the soils of the catchment area and 2–5 times higher than the values obtained for similar objects by other researchers. The analysis of the patterns of mercury distribution in bottom sediments indicates a one-time, local anthropogenic pollution of the lake.

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.

Fortnightly variability of total suspended solids and bottom sediments in a macrotidal estuarine complex on the Brazilian northern coast

Macrotidal estuaries are highly dynamic and complex environments that need to be understood in many aspects. In this context, the study of sediments is an important tool in the understanding of the processes in estuarine environments. The aim of the present study was to characterize the temporal and spatial distribution of total suspended solids (TSS) and bottom sediments of the Arraial Bay Estuarine Complex and their dynamics under different tidal conditions during different periods. Nine stations were selected within Arraial Bay Estuarine Complex, in Maranhense Gulf, where water samples were collected at two depths in different periods and tide conditions. The following parameters were analyzed: temperature, salinity, turbidity, total suspended solids (TSS), and bottom sediments for grain size analysis, in addition to cross sections to calculate the estuarine flow rate. Temperature, and pH, was within the expected range for the region, with little spatial or temporal variation. The precipitation and the hydrodynamics caused by tidal movements in the region are important controllers of salinity, estuarine flow, TSS and turbidity, which showed spatial and temporal variations. There is a predominance of fine material, mainly composed of silt, which suggests that mangroves are important in the supply and imprisonment of these sediments within the estuarine complex. In addition, tides play an important role in the distribution of suspended and bottom sediments, and in the dynamics of the resuspended one, controlling TSS concentrations and distributions of bottom sediments along the estuarine complex.

Analysis of bottom sediments of small lakes in Central Karelia

Data on the particle size distribution of bottom sediments in small lakes of Central Karelia are presented. Sediment fraction sizes in the study area Lake Torosjarvi varied from very fine sand to silty clay. The prevalent fraction was coarse silt. The paleo-hydrodynamic environment for sedimentation of the rocks was analyzed using the genetic diagram by R. Passega. Three intervals were characterized as turbidite deposits, the rest of the intervals fell in the zone of deposits left by low-velocity streams. The study of changes in sedimentation in Lake Torosjarvi suggests there occurred five shifts in the dynamic water regimes in the course of the lake formation.

РАСПРЕДЕЛЕНИЕ МЕТАЛЛОВ (Cu, Zn, Ni, Co, Cr, Pb, Fe И Mn) В ПОВЕРХНОСТНОМ СЛОЕ ДОННЫХ ОСАДКОВ СРЕДНЕГО И ЮЖНОГО КАСПИЯ

Atomic absorption determinations of a group of heavy metals (Cu, Zn, Ni, Co, Cr, Pb, Fe, Mn) in 190 samples of surface bottom sediments of the Middle and Southern Caspian Sea that were sampled by crab in middle of XX century (the collection of G.N. Baturin) and in 30 samples of recent sampling by grab also (2012–2015) were carried out. The aim of the investigations was to construct the schematic maps of heavy metal distribution in bottom sediments of both parts of the Caspian Sea on the materials of a half of century prescription that may serve as a base for comparison with the data of recent researches in frameworks of the program “The Caspian Sea System” under leadership of academic A.P.Lisitzin from 2012 till present time. The comparison between chemical composition of old and new sediment samples was realized, their similarities and divergences were revealed and probable reasons of divergences were presented. The maps of distribution of several metals (Fe, Mn, Co, Cr) are submitted together with necessary for interpretation maps of CaCO3, Corg and some other. It was shown that the structure of maps for all metals investigated was very similar because all these metals had concern to the group of iron.

Bottom Sediments Reveal Inter-Annual Variability of Interaction between the Ob and Yenisei Plumes in the Kara Sea

River discharge is the main source of terrigenous sediments in many coastal areas adjacent to estuaries and deltas of large rivers. Spreading and mixing dynamics of river plumes governs transport of suspended sediments and their deposition at sea bottom at these areas. Generally river plumes have very large synoptic and seasonal variability, which cannot be reconstructed from structure of bottom sediments due to their small accumulation velocity. However, bottom sediments can be indicative of variability of river plumes on inter-annual and decadal time scales. In this study we focus on the large Ob and Yenisei buoyant plumes formed in the central part of the Kara Sea. These plumes interact and mix in the area adjacent to the closely located Ob and Yenisei gulfs. Suspended sediments carried by these river plumes have significantly different geochemical characteristics that can be used to detect Ob or Yenisei origin of bottom sediments. Using new geochemical methods we revealed dependence between spreading patterns of these plumes and spatial distribution and vertical structure of bottom sediments in the study area. This relation is confirmed by a good agreement between local wind and discharge conditions reconstructed for 1948–2001 and vertical structure of bottom sediments.