Surface Layer Of Bottom Sediments Research Articles

Grain Size Distribution, Organic Carbon and Geochemical Markers in the Surface Layer of Bottom Sediments in the Northeastern Part of the Kara Sea

The upper layer of bottom sediments in the northeastern part of the Kara Sea is studied. It is shown that the composition of sediments is dominated by silt, the proportion of sand increases towards the shore. The content of organic carbon (average value — 1.1% wt.) is close to the average content in sediments of the Kara Sea, increasing at deep-sea stations. The revealed linear relationship between the content of organic carbon and the surface area of sediment shows that sorption on the particles surface is the predominant accumulation form of organic matter (OM) in sediments. The average n-alkanes concentration in the analysed samples is 1.1 μg/g of sediment, the distribution spectrum is dominated by terrigenous origin odd high-molecular homologues.

Distribution features of <sup>238</sup>U, <sup>232</sup>Th and <sup>226</sup>Ra in bottom sediments of the shelf and continental slope of Svalbard

The features of the distribution of concentrations of238U,232Th and226Ra in the surface layer of bottom sediments in the bottom sediments of the shelf and continental slope of Svalbard are considered. The content of226Ra,232Th, and238U varied in the range 22–134.3, 22.4–50.9, and 10.9–37.7 Bq/kg, respectively. The amount of226Ra nonequilibrium with238U (226Raex) ranged from 23 to 73% of the total226Ra content in sediments. The maximum concentrations of226Ra,238U,232Th and226Raex(134.3, 37.7, 50.9, and 98.2 Bq/kg, respectively) were obtained in the area of increased bioproductivity (Eagle Trough). In this zone, the relationship between the concentrations of226Ra and226Raexwith the content of organic matter in sediment is well expressed, the correlation coefficients areR= 0.94 and 0.92, respectively, which indicates a significant contribution of the biological community to the accumulation of226Ra in bottom sediments. The226Ra concentration and the226Ra excess value are negatively related to the redox potential of the sediment (R= –0.88). This pattern is also true in other areas of the Svalbard waters. In general, for the entire array of observations, the concentrations of238U and232Th increase with increasing content of organic carbon in the sediment (R= 0.72 and 0.7, respectively). The concentrations of238U and232Th decrease with increasing Ccarbcontent in the sediment (R= –0.79 and –0.81, respectively). The data obtained indicate the need to take into account the226Ra excess when assessing the total natural radioactivity of marine sediments, the value of which may exceed the radioactivity of238U and232Th.

Grain Size Distribution, Organic Carbon, and Geochemical Markers in the Surface Layer of Bottom Sediments in the Northeastern Kara Sea

Grain Size Distribution, Organic Carbon, and Geochemical Markers in the Surface Layer of Bottom Sediments in the Northeastern Kara Sea

RADIOACTIVITY OF SURFACE MARINE SEDIMENTS OF THE CHAUN BAY. ANALYSIS OF NATURAL AND ANTHROPOGENIC ENVIRONMENTAL FACTORS

The paper presents data on the spatial distribution of activity concentration of natural (232Th, 226Ra, 40K) and anthropogenic (137Cs) radionuclides in the surface layer of bottom sediments of the Chaun Bay of the East Siberian Sea. The measured activity of 232Th and 226Ra is typical for bottom sediments of the Arctic coastal zone and corresponds to the global level. The level of 137Cs activity in bottom sediments showed the absence of local sources of anthropogenic contamination in Chaun Bay, while the mean 40K activity concentration was 1.8 times higher than the global average. The results of statistical analysis showed that the dynamics of riverine run-off, thermoabrasion and currents, as well as aeolian and sea ice transport of sedimentary matter, are the main factors that determined the differences in the behaviour of the studied radionuclides in the surface bottom sediments of the Chaun Bay.

Environmental effects of potentially toxic elements and the magnetic susceptibility distribution in the surface bottom sediments in the Vistula estuary (Gulf of Gdańsk, Poland)

PurposeThis study is aimed at analyzing the spatial distribution of magnetic susceptibility and the content of potentially toxic elements (PTEs) in the surface layer of bottom sediments in the Vistula estuary (Gulf of Gdańsk, Poland) in relation to local sedimentary conditions. We also assessed the usefulness of magnetic susceptibility measurements to identify changes in sediment properties caused by anthropogenic factors.Materials and methodsBottom sediments were collected along three transects using the Van Veen grab sampler. The following properties were determined: granulometric composition, organic matter and carbonate content, pH, electrical conductivity, and heavy metal content (Cd, Cr, Cu, Fe, Ni, Pb, and Zn). Specific (mass) magnetic susceptibility (χ) was measured using the MS2 Bartington® laboratory magnetic susceptibility meter. To characterize the conditions of the sedimentary environment in the study area, statistical analysis was performed on selected parameters of grain size distribution, such as mean grain diameter (Mz) and sorting (σ1) indices.Results and discussionThe research showed significant differences in the sedimentary environment (erosion vs. deposition processes) along the studied transects which were controlled by the wave regime, sea currents, and river water inflow. Open-water sediments were richer in organic matter and more saline than deltaic sediments, which in turn were characterized by higher pH and higher carbonate content. The highest mean total content of Pb, Cu, Ni, and Zn and the highest magnetic susceptibility (χ) were determined in open-water sediments, while the highest Fe and Cr values were obtained for deltaic sediments. Statistically significant differences between these sediments were found only for organic matter (LoI), Pb, Cu, and Cd content. Magnetic susceptibility showed a moderate correlation with Pb, Cu, Cd, and Zn (rs 0.4–0.6).ConclusionPTE content and magnetic susceptibility of sediments showed a very high heterogeneity within the study area, depending mainly on the location (delta vs. open waters), grain size composition, and organic matter content. Our results demonstrated that magnetic susceptibility analysis is an easy method that can be used to complement the identification of technogenic changes in the marine environment.

Surface Bottom Sediments of the North Atlantic on the Transect along 59.5° N

An analysis of the lithological, isotope-geochemical, and micropaleontological parameters of the surface layer of bottom sediments in the North Atlantic was made at 26 stations on the profile along 59.5° N. The distribution of humidity and granulometric composition of sediments reflects vertical/circumcontinental zonality, since fine-grained and water-saturated material accumulates in the deepest parts of the Iceland Basin and the Labrador and Irminger seas, which are farthest from land. Larger masses of calcium carbonate are also formed there, but organic carbon is unevenly distributed. Both vertical/circumcontinental and climatic (circulation of the warm North Atlantic water) zonalities affect the mineral composition of the sediment fraction 0.063 mm. The accumulation of diatoms, radiolarians, and planktic foraminifers in sediments reflects both vertical/circumcontinental and, to a greater extent, climatic zonality. Variations in the isotopic oxygen and carbon ratios in the shells of benthic and planktic foraminifers require a complex interpretation involving data on the parameters of various surface and bottom water masses. The distribution of planktic microfossil assemblages according to cluster analysis shows areas of distribution of different water masses with a clear boundary along the eastern margin of the Subpolar Gyre. The distribution of “cluster” assemblages of benthic foraminifers does not correspond much to that of planktic microfossils, reflecting the division of the water area into abyssal and shallow water areas.

ЗАСТОСУВАННЯ ГІДРОАКУСТИЧНИХ МЕТОДІВ ПІД ЧАС ГЕОХІМІЧНИХ ДОСЛІДЖЕНЬ РОЗПОДІЛУ ЗАБРУДНЮВАЧІВ У ПОВЕРХНЕВОМУ ШАРІ ДОННИХ ВІДКЛАДІВ

The article presents the results obtained during the long-term field studies of the characteristics of the sedimentary matter metal-containing component distribution within the territories of industrial cities, in particular, Zaporizhia city. Based on field contact and remote studies, one of the aspects of the problem was studied, namely the peculiarities of iron concentrations distribution in the surface layer of bottom sediments of the Dnipro river. Key practical approaches to the application of a new complex method of field observations are outlined, which combine the possibilities of express planar surveying with the determination of geochemical characteristics of river sediments. The methodology of combining contact geochemical studies of iron distribution in surface bottom sediments with the performance of a side view of a remote route survey using sonar is substantiated. Herewith, the possibility of determining the lithological differences of the surface layer of bottom sediments under the conditions of determining the average concentrations of iron for the main material types of sediments is assumed. The results of two-year research based on the data of fieldwork revealed promising perspectives for the development of such a complex of observations in the case of systematization of the direction, additional testing of the technological component in various test areas of the water area, as well as the development of an appropriate methodological foundation.

Features of 226Ra, 232Th, 238U Distribution in the Surface Layer of Bottom Sediments in the Northern Part of the Laptev Sea

Features of 226Ra, 232Th, 238U Distribution in the Surface Layer of Bottom Sediments in the Northern Part of the Laptev Sea

Characteristics of Bottom Sediments in the Coastal Areas of the Crimean Peninsula

The aim of this work was to assess the influence of physical, chemical, and hydrochemical factors on the characteristics of bottom sediments in various areas of the shelf of the Crimean Peninsula. The data obtained during the cruises of the RV “Professor Vodianitsky” in the fall of 2018 and summer of 2019 were analyzed. Hydrochemical analyses of the bottom waters were carried out using standard hydrochemical methods. Profiles of dissolved oxygen, hydrogen sulfide, and oxidized and reduced forms of iron in pore waters were obtained, and the geochemical characteristics of bottom sediments were determined. The features of their spatial and vertical distributions were considered. Pelite-aleuritic sediments with inclusions of sandy material and shell detritus prevailed in the coastal zone of the Crimean shelf. The organic carbon content varied from 0.5–0.6% in the gravel–sand sediments of the Kerch pre-strait area to 2.5–2.7% in the northwestern part. The prevalence of suboxic conditions was noted, and the main processes in the sediment upper layer were controlled mainly by reactions involving iron. In some areas of the southern coast of Crimea and the Kerch pre-strait area from the Sea of Azov, the development of anoxic conditions in the surface layer of bottom sediments was recorded.

Toxic metal pollution of aquatic ecosystems of European Union nature protection areas in a region of intensive agriculture (Lake Gopło, Poland)

The paper presents the results of research into toxic metal concentrations in the surface layer of bottom sediments in Lake Gopło. The research objectives were to identify the levels and spatial variability of Cu, Pb, Cd, Zn, Ni, Cr, As and Hg concentrations, their potential sources and the determinants of pollution levels. Metal contamination of the sediments was assessed using the geoaccumulation index (Igeo), pollution load index (PLI) and ecological risk index (RI). Chemometric methods (Pearson correlation, principal component analysis (PCA) and cluster analysis (CA) were used to determine the relationship between sampling sites and concentrations of toxic metals, thereby identifying the sources of contamination. The research found that grain-size composition, carbonate content and organic matter content in the bottom surface sediments of Lake Gopło are all characterised by low diversity. Therefore, the lithological features of the sediments are not a major factor in the concentrations and spatial variability of the metals. It was found that the metal concentrations in the great majority of samples were above regional geochemical background levels. The geochemical indices (Igeo, PLI, RI) indicate that the degree of toxic metal pollution in the sediments is slight in the central and southern parts of the lake and high in the northern part. The chemical analysis results showed that the samples in the central and southern parts of the lake differ little in their shares and concentrations of individual metals. This provides evidence that, as well as geogenic sources, their presence in sediments can be associated with non-point sources related to agricultural activities and with atmospheric sources (mainly the products of fossil fuel combustion). The higher concentrations of metals (especially Ni, Cd, Cr and Hg) in the northern part of the lake are influenced by the supply of industrial and communal pollutants from the lakeside town of Kruszwica. A factor limiting the migration of pollutants from the northern part of the lake towards the south is the lake’s morphology of the lake, which hinders water exchange between the northern part and the rest of the lake.

СОДЕРЖАНИЕ И ПРИРОДА УГЛЕВОДОРОДОВ ВО ВЗВЕСИ ПОВЕРХНОСТНЫХ ВОД И ДОННЫХ ОСАДКАХ КЕРЧЕНСКОГО ПРОЛИВА

The results of studying the concentration and composition of hydrocarbons in the suspension of surface water and in the surface layer of bottom sediments in the Kerch Strait in July 2020 in comparison with 2019 and with earlier studies in other regions of the Black Sea are presented. Despite the high concentrations of aliphatic hydrocarbons (especially in the water of the strait (on average 78 μg/L) and in coarse-grained sediments (47 μg/g)), the composition of alkanes did not correspond to the oil composition due to the rapid transformation of petroleum aliphatic hydrocarbons. The factor analysis revealed that the pollution has two sources: the main, pyrogenic (from transport) and, to a lesser extent, the oil one.

Hydrocarbon pollution in the waters and sediments of the Kerch Strait

The results of studying the content and composition of aliphatic hydrocarbons and polycyclic aromatic hydrocarbons in the suspended particulate matter of surface waters and in the surface layer of bottom sediments in 2019–2021 in the Kerch Strait in comparison with earlier studies in other areas of the Black Sea (Theodosia Gulf, Tuapse area, Coastal waters of the Crimean Peninsula, Big Sochi, Central part of the Sea) are presented. Despite the high concentrations of aliphatic hydrocarbons (especially in the waters of the strait itself: 28–254 on average 87 μg/L. The highest content of aliphatic hydrocarbons was confined to the cross-section through the Kerch Strait. Accumulation of aliphatic hydrocarbons, as well as the suspended particulate matter, occurs in the western part of the Strait, which is associated with the predominant wind direction and coastal orography. The composition of alkanes did not correspond to the smooth distribution of homologues characteristic of oil. Their distribution was bimodal in most samples, which may indicate a mixed genesis of alkanes. Among the low-molecular-weight alkanes either even numbered autochthonous alkanes n-C16, C18, C22, arising during the microbial transformation of aliphatic hydrocarbons, or n-C17, indicating the inclusion of phyto- and zooplankton alkanes, prevailed. Despite the different sources of hydrocarbons input, the distribution of the total concentrations of aliphatic hydrocarbons and polycyclic aromatic hydrocarbons basically coincided. Polycyclic aromatic hydrocarbons composition was dominated by fluoranthene and pyrene, which are formed in high-temperature combustion processes Low values of the Σnaphthalenes/Phen ratio (0.05–0.11) may indicate an insignificant inclusion of petroleum polyarenes.In contrast to suspension of surface waters, the highest content of hydrocarbons in the surface sediments was found not in the strait, but at stations in areas with aleurite-pelitic sediments, which is due to the pattern of currents in these areas and the higher sorption capacity of finely dispersed sediments. The average Corg content in July 2020, was 1.8 times lower (0.34%) than in September 2019 (0.63%), and aliphatic hydrocarbons, on the contrary, was 2.2 times higher (47 μg/g) than in April 2019 (21 μg/g). In surface sediments the maximum concentration of aliphatic hydrocarbons was established in July 2020 (233 μg/g), and the highest average content in July 2021 (58 μg/g). This area is also associated with higher concentrations of aliphatic hydrocarbons in the composition of Corg –≥1%. The composition of alkanes in surface sediments differed from their composition in suspension. The ratio of low-to-high molecular weight homologues (L/H = 0.08–0.54) was lower and the odd-to-even ratio (CPI = 1.19–4.58) was higher than in particulate matter. Due to the coarse composition of sediments, the content of polycyclic aromatic hydrocarbons in their surface layer was lower (0–631 ng/g) compared to other areas of the Black Sea. In their composition, along with fluoranthene and pyrene, methylated naphthalene homologues also belonged to the dominant compounds. Correlation analysis of individual polyarenes, as well as factor analysis, indicates their mixed genesis oil + pyrogenic, with the preference of the latter in most samples. The entry of pollutants into the marine environment increases the hydrocarbons content in water and bottom sediments, creating a modern hydrocarbon background.

О некоторых закономерностях изменения плотности в литосфере Северной Евразии

A method is proposed for calculating the normal compaction curve of rocks for the deep parts of the lithosphere. It is based on the analysis of petrophysical characteristics and interpretation of gravitational anomalies. The main regularities of density changes in the lithosphere of Northern Eurasia are investigated. It has been shown that the density section of the region’s lithosphere is characterized by alternation of paragenetically connected decompacted-compacted (relative to normal compaction) rock complexes at all levels of the lithosphere from the surface layers of bottom sediments to the mantle. These zones of decompacted-compacted rocks complexes have a global distribution.

Hydrocarbons in Water and Bottom Sediments in Kerch Strait

The article gives the results of studies of the concentration and composition of aliphatic hydrocarbons in suspension in surface water and in the surface layer of bottom sediments in April and September 2019 in Kerch Strait compared with other regions of the Black Sea. Notwithstanding the high concentrations of aliphatic hydrocarbons (especially, in the water of the strait itself, i.e., 110–160 µg/L and in sand sediments, i.e., 16–63 µg/g), the composition of alkanes was not of petroleum type because of the rapid transformation of petroleum hydrocarbons. The pollution of water and sediments in the strait manifested itself in a higher concentration of hydrocarbons in the composition of lipids and Corg, in the presence of naphthene-aromatic compounds in alkane composition, and in the predominance of phytane over pristine.

The Density of Bottom Sediment Particles in Water Bodies

The density of particles in the bottom deposits of water bodies is an important characteristic, which determines the rate of interaction between bottom water layers with the surface layer of bottom sediments and which in the modern studies cannot be assumed constant. In the presented article, the variability of this characteristic is evaluated for Lake Ladoga. This variability requires correction of the existing procedures for particle-size analysis of bottom sediments in natural water bodies.

Heavy metals in the bottom sediments of the coastal zone of the eastern part of the Gulf of Finland

For each summer from 2014 to 2019 the total concentrations of copper, zinc, cadmium, and lead in the surface layers of bottom sediments in the coastal zone of the eastern part of the Gulf of Finland were measured. The northern coast in the area of the city of Primorsk currently sees the rate of the pollution of surface-level bottom sediments with heavy metals decrease, although the concentration levels remain high. On the southern coast in the area of the city of Lomonosov the pollution of the bottom sediments is on the rise due to the ongoing construction of the Bronka seaport. In the Koporskaya and Grafskaya Bays a massive growth of macroalgae caused a further accumulation of metals in the bottom sediments, which are greatly impacted by climatic fluctuations.

Grain Size Distribution of the Surface Layer of Bottom Sediments in the Barents Sea

The paper presents data from a granulometric analysis based on the results of studying of 44 surface (0–5 cm) sediment samples obtained on cruise 67 of the R/V Akademik Mstislav Keldysh (2016) from different parts of the Barents Sea. Pebble and gravel material is found in surface sediments as an admixture scattered throughout the sea. Such a chaotic distribution pattern is apparently associated with ice rafting. Coarse material is most common in the Barents Sea off the coast of the Kola Peninsula, Novaya Zemlya, and Svalbard, where it accumulates due to coastal abrasion, glacial exaration and bottom erosion. In addition, the >1 mm fraction is widespread at depths where fine fractions are stirred and washed away. The most common sediments in coastal shallow waters are sands. Sands (0.1–1 mm) are widespread in the southern and southeastern regions of the sea, in the region of the Pechora test area, the Kanin Shoal, the Kola Peninsula shallows; and in the northwest, off the coast of Svalbard. With increasing depth, coarse sediments are replaced by mixed sediments with a low pelite admixture. Fine-grained sediments are prevalent in the central part of the sea. Sediments with a pelitic fraction (<0.01 mm) of more than 50% occupy about 70% of the Barents Sea. They are widespread in deep-sea depressions and troughs, as well as in the numerous fiords of the Northern Island of Novaya Zemlya and Franz Josef Land.

Sources and Generation Parameters of the Hydrocarbon Background of Bottom Sediments in Small Estuaries of the Tatar Strait

The paper presents data on the composition of organic matter (OM) in the surface layer of bottom sediments (BS) in two small estuaries in the southwestern part of the Tatar Strait (as of summer of 2014 and 2016). The concentration of hydrocarbons (HC) varied from 0.01 to 2.0 mg/g. The HC content in the uniform silt–psammite sediments (0.55–1.47 mg/g) was higher than the biogenic background level (≈0.1 mg/g). The percentage of HC carbon of total Corg (TOC) in the sediments of Muchke Lake (2.68% on average) was much higher than that in Toki Lake and than the value of ≤1% assumed as an indicator of the absence of a hydrocarbon load. The percentage of autochthonous OM (determined from the chlorophyll a content) in the sediments of weakly flowing Muchke Lake is 41% of TOC, and the value for flowing Toki Lake is 18%. The data obtained in the course of this study are consistent with the molecular composition of the n-alkanes: the OM of Muchke Lake is dominated by that of hydrobiont origin, whereas the OM of Toki Lake consists mostly of terrigenous–humic compounds. The n-alkanes contain much compounds typically produced by bacterial synthesis, which indicates that microorganisms played an important role in forming the hydrocarbon background of sediments in the small estuaries.

Transformation of Dissolved Matter Runoff in the Ural River Mouth

The distribution of dissolved major- and trace elements in the mixing zone of the Ural River and the North Caspian waters was studied based on the natural observations data from 2016–2017. Conservative behavior was established for most of major ions (Na, K, Mg, SO4) and some trace elements (Li, Rb, Cs, Sr, Co, Ni, Cu, Zn, Sb, Ga, Y, U, B, F, Cr, Ge, Mo, W) with common parameters of relationships between their concentrations and chloride content for different years. The distribution of components of the carbonate system is controlled by chemogenic precipitation of calcium carbonate at the mouth beach. This process leads to the removal from solution up to 11–17% calcium and 6–8% hydrocarbonates carried by river runoff, and a simultaneous decrease in the pH value. Nutrients are involved in the processes of biological assimilation and regeneration. The mixing zone of the Ural River and Caspian waters is characterized by: (a) phytoplankton consumption of large amounts of silicon and nitrates (up to 58–88 and 61–67%, respectively, of their content in riverine waters), (b) removal of significant part (up to 18–25%) of nitrites, and (c) additional input of phosphates into solution, presumably from pore waters of the surface layer of bottom sediments in amounts 1.5–3 times greater than those removed with river runoff. A distinctive feature of barium migration is an additional input into solution (up to 20%) at the initial stage of salinization owing to the desorption from terrigenous material. The coagulation and flocculation of organic and organo-mineral colloids lead to the removal of significant part (up to 25–100%) of dissolved manganese, iron, aluminum, and rare-earth elements runoff, as well as to the removal of lead, titanium, zirconium, and hafnium from solution in amounts 1.1–6 times greater than their contents in the river water mass.

Hydrocarbons in the Water and Bottom Sediments of the Barents Sea during Ice Cover Variability

Aliphatic hydrocarbons (HCs) were studied in water and bottom sediments sampled during cruises 67th and 68th (August–September 2016 and July–August 2017, respectively) of the R/V Akademik Mstislav Keldysh in the Barents Sea to determine the lateral and interannual variability of their concentrations and composition. It has been established that the HC distribution in water was mainly determined by natural factors and depended on the hydrological peculiarites in different areas of the sea. From autumn 2016 to summer 2017, hydrocarbon concentrations slightly increased (on average, from 3 to 5 µg/L), which was related to a change in the biochemical composition of organic matter likely owing to the decrease of ice area. The content of HCs decreased mainly with the depth. An exception was observed in the area of troughs and deposits, where nepheloid bottom layers demonstrated an increase of HC concentration in suspended matter and in the surface layer of bottom sediments, whereas sedimentary sequence showed no correlation between HC distribution and organic carbon.