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.

New results of a palynological study of the Lake Doroninskoe sediments (Eastern Siberia, Transbaikalia)

This article presents the results of the study of the bottom sediments of the meromictic Lake Doroninskoe. For the study, the method of spore-pollen analysis was used. The record showed that during the accumulation of 65 cm of the sediment layer in the Chita-Ingodinskaya depression, pine and larch predominated along the ridges, with steppe and meadow associations in the lower parts of the depression. According to regional correlations, the distribution of light-coniferous-taiga vegetation in Transbaikalia occurred as early as the Middle Holocene, and it did not undergo cardinal changes until modern times. According to these data, sediments may have accumulated during this time period.

Biological control of incrusting organisms and sediments in Chilean oyster cultures

The oyster culture has the incrusting organism as problem for production, in this context, it evaluated as biological control against incrusting organism and sediments the introduction of gastropod Tegula atra (Lesson, 1830) in Chilean oysters (Triostrea chilensis Phillippi, 1844) cultures in conditions of starvation presence and absence located in floating cages and bottom cultures. The predation and mechanic effect on T. atra grazing generated a decreasing in seven days of 19.8% and 13.7% of incrusting organisms in cage culture and bottom sediments by effects of gastropods without starvation respectively. Whereas it had a decrease of 12.6% and 11.4% of incrusting organisms in cage culture and bottom sediments by effects of gastropods with starvation respectively. The incrusting organism removed were mainly algae, colonial ascidia, polychaeta, bryozoan and small crustaceans.

Contamination of the Dzheltulak-1 river basin under alluvial gold mining (the Amur region)

The purpose of the introduced research is to study the environmental impact of placer gold mining. The object of the study is natural and natural-man-made geosystems of the Dzheltulak-1 river located in the Amur region. The content of the main cations and microelements in water samples was determined by atomic emission and mass spectral methods. The content of micro- and rock-forming elements in bottom sediments and soils was determined by X-ray fluorescence using XRF-1800 X-ray spectrometer (Shimadzu, Japan). The results of the conducted studies indicate that the contents of iron, manganese, copper, aluminum, vanadium, molybdenum, mercury and ammonium ions exceed commercial fishery standards in a significant part of the surface water samples. It is found out that settlement ponds negatively affect the water quality in the river Dzheltulak-1 downstream due to the dam drainage. The highest concentrations of dissolved forms of mercury were noted in the water of the settlement ponds. The gross content of arsenic in the samples of bottom sediments and soils exceeds sanitary and hygienic standards by 2.7–14.5 times. The distributions of mercury as the most dangerous pollutant among the biogenic components of geochemical landscape were worked out in detail. Mercury contamination of soils was classified according to the forms of mercury occurrence: free, physically sorbed, chemisorbed, sulfide and isomorphic. It has been shown that the free form is characteristic of fresh mercury contamination due to the use of prohibited technological schemes for gold-bearing sands separation by the amalgamation method.

MICROPLASTICS POLLUTION MONITORING IN BOTTOM SEDIMENTS OF THE SEVASTOPOL REGION RECREATION ZONES

A study of the concentration of microplastic pollution (MP) in the bottom sediments of the water areas adjoining recreation zones (RZ) of the Sevastopol region in 2018 - 2020 was carried out. An increase in MP was registered practically in all areas, the average values of MP concentration were 13.4 items•kg-1 dry weight. As for the shape of microplastics (MPs) particles, the maximum share was made up by frag-ments (50-83%), fibers were also numerous (33%). A significant increase in the concentration of MP on the 0-20 m section of the underwater coastal slope from the water edge was recorded in zones with an open water area and presence of a cliff. The revealed level of MP is comparable to that in the Mediterra-nean, Caspian, Baltic Seas, but an order of magnitude lower than in other regions of the World Ocean.

Investigation of the nature of suspended matter under the influence of the facies-genetic characteristics of bottom sediments

The purpose of this study is to obtain a mathematical model to assess the influence of the facies and genetic characteristics of bottom sediments on the distribution of suspended matter during dredging.The addressed problem is associated with the detrimental effect of bottom sediments during hydraulic works on the ecological state of a water body. An increase in the level of technogenic turbidity leads to redistribution of the thermal conductivity of water masses and corresponding deterioration in the habitat of aquatic organisms. The development of a mathematical model for the distribution of suspended matter is an urgent task, the solution of which will allow us to analyze the area of distribution of each of the facies of bottom sediment during dredging operations.A mathematical model of the distribution of facies of suspended matter during dredging operations based on the finite difference method has been developed. Software for modeling and visual representation of the process of propagation of facies of suspended matter in the water space of the Gorin River during dredging operations has been developed using C# software, Visual Studio software development environment.The scientific novelty of the performed work is a qualitative and quantitative assessment of the distribution of suspended solids during dredging operations under conditions of hydrogeological uncertainty.

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.

STATE OF BOTTOM SEDIMENTS OF THE VORONEZH RESERVOIR IN THE PLACES OF WATER DISCHARGE FROM THE TREATMENT FACILITIES OF THE CITY OF VORONEZH

Рассмотрена проблема загрязнения Воронежского водохранилища в пределах Воронежской городской агломерации, в местах сброса вод с очистных сооружений предприятий левого берега. В работе использованы результаты количественного химического анализа донных отложений, выполненных на базе эколого-аналитической лаборатории факультета географии, геоэкологии и туризма Воронежского госуниверситета, а также данные мониторинга, предоставленных Федеральной службой по надзору в сфере природопользования и Департаментом природных ресурсов и экологии Воронежской области. База данных включает результаты наблюдений с 2000 по 2021 год. По составу осадков прослежена история аккумуляции загрязнителей, выделены проблемные зоны водоема в каждом исследуемом периоде. Выполнен пространственно-временной анализ содержаний загрязняющих веществ, рассчитаны «кларки концентрации» тяжелых металлов, по которым для каждой точки наблюдения в порядке возрастания значения признака построен ранжированный ряд. На основании лабораторных исследований и результатов их статистической обработки с применением корреляционного анализа сделаны выводы о перспективах существования и развития Воронежского водохранилища. Проверены корреляционные связи между «кларками концентрации» и суммой выпавших осадков за календарный и за гидрологический год. По содержаниям сероводорода в различные годы, сделаны выводы о диапазоне колебания концентраций и формировании цикличного процесса. Выделена зона устойчивой деградации водоема. Ее формирование происходит выше и ниже сброса с городских очистных сооружений левого берега города. Результаты многолетних наблюдений за качеством донных отложений указывают на значительную техногенную нагрузку со стороны Воронежской городской агломерации. Недостаточная очистка воды, медленная скорость течения и турбулентность природной воды ускоряет процесс естественного эвтрофирования водоема. The author considers the problem of pollution of the Voronezh water reservoir within the Voronezh urban agglomeration, in places of discharge of water from the treatment facilities of enterprises of the left bank. The paper uses the results of quantitative chemical analysis of bottom sediments performed on the basis of the ecological and analytical laboratory of the Faculty of Geography, Geoecology and Tourism of Voronezh State University, as well as monitoring data provided by the Federal Service for Supervision of Nature Management and the Department of Natural Resources and Ecology of the Voronezh Region. The database includes the results of monitoring from 2000 till 2021. On the basis of the composition of precipitation the author detected the history of accumulation of pollutants; as well she identified problem areas of the water reservoir in every study period. The author performed a spatio-temporal analysis of the contents of pollutants, calculated the "concentration clarkes" of heavy metals, according to which she created an ordered series for each observation point in ascending order of the attribute value. Based on laboratory studies and results of their statistical processing using correlation analysis the author draws some conclusions concerning the prospects for the Voronezh water reservoir existence and development. The correlations between the "concentration clarkes" and the amount of precipitation for the calendar and hydrological year have been verified. Based on the hydrogen sulfide content in different years, the author concludes about the range of concentration fluctuations and the formation of a cyclic process. She identified the zone of stable degradation of the water reservoir. Its formation occurs above and below the discharge from the municipal sewage treatment plants of the left bank of the city. The results of long-term observations of the quality of bottom sediments indicate a significant anthropogenic load on the part of the Voronezh urban agglomeration. Insufficient water purification, slow flow velocity and turbulence of natural water accelerate the process of natural eutrophication of the water reservoir.

Commercial exploitation of Kуiv reservoir as a fishery water body (a review)

Purpose. To analyze an array of special scientific literature and summarize the obtained information on the commercial exploitation of the Kуiv reservoir as a fishery water body. To review main abiotic conditions of the reservoir, which exist and form the specificity of its commercial use by the fishery industry of Ukraine. To highlight the historical course of their impact on the fish fauna of the Kyiv Reservoir and general forecasts for its future transformations. Findings. An overview of scientific publications devoted to the specifics of commercial exploitation of the Kуiv reservoir as a fishery water body from the moment of its creation to the present day were presented. In particular, following was analyzed: hydrological regime, color and chemical composition of water, oxygen regime, accumulation of heavy metals, formation of bottom sediments and landscape. In addition, the radioecological situation in the reservoir was anazyed, both general and in three most significant areas for fisheries — in bottom sediments, macrophytes, and fish fauna. The literature data on the specificity of the above-mentioned abiotic factors in this reservoir, which form the hydro-ecological feature of this reservoir, were generalized. The main directions of their influence on the ichthyofauna of the Kуiv reservoir, which affect the possibility of its commercial exploitation, were described. The share of anthropogenic origin in the composition of the above-mentioned abiotic factors and the consequences of its impact were highlighted. The perspective ways of further development of the Kiev reservoir as a fishery water body of strategic importance for Ukraine were shown. Practical Value. The review may be useful for scientists, PhD students, students, government authorities, and private entrepreneurs involved in research process or exploatation of aquatic living resources in internal water bodies, primarily in the Kуiv reservoir. Keywords: Kуiv reservoir, fishery water body, hydrological regime, water chemical composition, water oxygen regime, heavy metals, bottom sediments, landscape formation, radioecological situation.