Destruction Of Organic Matter Research Articles

Study of Free-living Protozoa in Azerbaijan

The article provides data on the biological significance of two groups of free-living Protozoa: testate amoebae and free-living ciliates. Their importance and role in the main biological processes of production and destruction of organic matter in both water and soil ecosystems are indicated. A review of the knowledge of these two groups of Protozoa in Azerbaijan is given in chronological order, indicating the most important publications of the early authors as well as modern ones. A review of modern works on the ecology of free-living Protozoa was carried out, including practical importance for humans (The use of Protozoa as indicators of the organic pollution degree and in toxicological studies).

Effect of Bacterial Fertilizers on the Microbiological Activity of Segregated Chernozem in Spring Barley Crops

In the field experiment, in the Voronezh region on the territory of the Voronezh FASC, changes in the microbiological activity of the soil under the influence of bacterial associative biological products and mineral fertilizers during 2021–2022 were studied. Microbial strains were used for pre-sowing seed treatment. The soil of the experimental site is ordinary (segregational) medium–humus heavy loamy chernozem. The availability of available forms of batteries is medium and high. The barley variety is Talovsky 9. The cultivation technology is generally accepted in the zone. The preservation of soil fertility and its rational use due to changes in the direction of microbiological processes in the soil with the use of diazotrophs has been established. Associative preparations slowed down the processes of mineralization of humic substances. The number of bacteria associated with the destruction of organic matter decreased. With the complex use of mineral fertilizers with rhizobacteria, the number of nitrifiers responsible for denitrification processes and losses of soil nitrogen significantly decreased. A significant increase in the natural background of fertilization of the number of soil fungal microflora under the influence of diazotrophs was noted.

PHOTOCHEMICAL TRANSFORMATION OF DISSOLVED ORGANIC MATTER AND BEHAVIOR OF METALS IN THE WATERS OF THE SOUTHERN TAIGA BOG COMPLEX, WESTERN SIBERIA

Link for citation: Raudina T.V., Smirnov S.V., Istigechev G.I., Pokrovsky O.S. Photochemical transformation of dissolved organic matter and behavior of metals in the waters of the southern taiga bog complex, Western Siberia. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 9, рр. 182-193. In Rus. The relevance. Dissolved organic matter is one of the largest biologically available sources of carbon in terrestrial and aquatic ecosystems, and its dynamics are critical to local and global carbon cycles. Destruction of organic matter during migration determines the biological cycle of elements and their stability. Important processes that lead to the transformation or removal of the dissolved organic matter are bio- and photodegradation. To date, enough research has been carried out to study the composition of humic substances, forms of metals, and the processes of migration of organo-mineral compounds in natural waters of the taiga zone, Western Siberia. Work is underway to study the dissolved organic carbon bioavailability, but the mechanisms of its photochemical transformations in different seasons of the year have not been studied. At the same time, photochemical mineralization of dissolved organic compounds largely regulates the biogeochemical cycles of elements by changing their bioavailability, the intensity of carbon dioxide emission from surface waters into the atmosphere, and the removal of dissolved trace elements through precipitation and coagulation. The main aim is to assess changes in the chemical composition and the rate of the dissolved organic matter and dissolved metals removal in the waters of the southern taiga bog complex (Western Siberia) under the sunlight exposure on a spatio-temporal scale. Objects: soil waters within different bog landscapes (open sedge-sphagnum fen, tall ryam (pine-shrub-sphagnum phytocenosis with high pine trees), and waterlogged mixed forest) of the Bakchar bog complex located in the southeastern part of the Ob-Irtysh interfluves, the Vasyugan plain. The waters were taken at a depth by digging a pit (40´40 cm area, 40 cm depth), which allowed the surrounding gravitational water to fill it up to the depth of 10–20 cm. The sampling took place during two field period in 2020 (June and October). Methods. pH, water temperature, specific conductivity (Cond) and dissolved oxygen were measured using a multiparameter instrument (WTW MULTI 3430 SET). The dissolved organic carbon was measured by a high-temperature thermic oxidation method using a Shimadzu TOC-LCPN analyzer, with an uncertainty of 2 %. The absorbance was measured at wavelengths up to 800 nm, 1 nm step using quartz 10 mm cuvette on a Cary-50 spectrophotometer. Major cations (Ca, Mg, Na, K), Si, and trace metals were determined with an ICP-MS Agilent CE 7500 with In and Re as internal standards and three various external ones. In the photodegradation experimental design, we followed the methodology which is sunlight exposure of sterile filtered (0,2 μm) samples in quartz reactors in the outdoor pool. Results. The authors revealed the influence of photodegradation on the qualitative and quantitative composition of dissolved organic substances and the behavior of metals in water samples of bog landscapes of the taiga zone of Western Siberia on spatiotemporal scales. It was established that from 3 to 30 % of the dissolved organic carbon can be removed from soil water under the influence of sunlight with maximum values in early June. At the same time, in autumn, despite the decrease in the amount of solar radiation, the photodegradable DOC can also reach 10–12 %. In general, there is a decrease in the percentage of the dissolved organic carbon loss in the waters in the row fen>ryam>forest. The dissolved organic carbon removal can be associated both with the transition of a part into an inorganic form, and with the destruction of high-molecular organic substances. A significant change (p<0.05) in the optical parameters is noted, which is consistent with the behavior of the dissolved organic matter during photolysis. In addition, under the influence of insolation, the transformation of organo-mineral compounds occurs, which leads to a change in the forms of metals. The greatest losses relative to control were observed for rare earth elements (Y, La, Ce, Pr, Nd), as well as Ti, V, which in some cases reach 70 % (more significant in fen waters). These trace elements show behavior similar to dissolved organic carbon,  Al and Fe, which confirms the importance of organic and organo-Fe-Al-colloids determining the behavior of most elements in acidic waters with a high content of organic matter.

Gas ebullition associated with biological processes in radioactively contaminated reservoirs could lead to airborne radioactive contamination

BackgroundStorage reservoirs of radioactive waste could be the source of atmospheric pollution due to the efflux of aqueous aerosol from their water areas. The main mechanism of formation of aqueous aerosols is the collapse of gas bubbles at the water surface. In this paper, we discuss the potential influence of biological factors on gas ebullition in the water areas of the radioactively contaminated industrial reservoirs R-9 (Lake Karachay) and R-4 (Metlinsky pond) of the Mayak PA. The emission of the released non-dissolved gases captured with gas traps in reservoir R-9 was (88–290) ml/m2 per day (2015) and in reservoir R-4 (270–460) ml/m2 per day (2016). The analysis of gas composition in reservoir R-4 (60% methane, 35% nitrogen, 2.4% oxygen, 1.5% carbon dioxide) confirms their biological origin. It is associated with the processes of organic matter destruction in bottom sediments. The major source of organic matter in bottom sediments is the dying phytoplankton developing in these reservoirs. ConclusionThe obtained results form the basis to set a task to quantify the relationship between the phytoplankton development, gases ebullition and radioactive atmosphere contamination.

The Primary Crop of Phytoplankton and Total Organic Matter Destruction in Varvara Reservoir, One of the Main Reservoirs of Azerbaijan

The role of phytoplankton in regulating the flow of physico-chemical processes in ecosystems, including hydrobionts, which is involved in the formation of biological products, the circulation of substances in the life of reservoirs, the creation of their energy source, is very large. Fhytoplankton ecosystems are very sensitive to abiotic factors and anthropogenic influences to many physical, chemical and biological factors present in the environment. Therefore, phytoplankton is considered the basis of trophic relationships in the hydroecosystem.

Nutrient Flux under the Influence of Melt Water Runoff from Volcanic Territories and Ecosystem Response of Vilyuchinskaya and Avachinskaya Bays in Southeastern Kamchatka

Nutrient fluxes with river runoff can largely determine the state of coastal water ecosystems. The Vilyuchinskaya and Avachinskaya Bays of Kamchatka Peninsula were surveyed on 4–5 July 2022, just after the peak of the spring–summer flood of the Vilyucha and Avacha Rivers associated with the snow melting in volcanic areas. Additionally, water sampling was performed in river water in December 2022, in the period of winter low water. A general undersaturation of CO2 of surface waters was observed in the Vilyuchinskaya and Avachinskaya Bays. Strong supersaturation of CO2 of the near-bottom waters was observed, due to microbial destruction of organic matter, especially in Avachinskaya Bay. This organic matter was formed as a result of photosynthesis in the water column, which subsequently gravitated to the bottom and concentrated in specific bottom depressions in the studied bays. In these depressions, black sediments were found, in which sulfate reduction occurred. The porewater of sediments had a very high concentration of organic carbon, dissolved and organic nitrogen, and phosphates, as well as CO2 partial pressure. The source of nutrients for the studied bays is tephra (volcanic suspended particles), which covers all the watersheds, including the soil and snow, as a result of volcanic activity in the study region. Based on the calculated nutrient fluxes in river runoff for the summer and winter seasons and the DIN/DIP ratios in river, sea, and pore waters, the causes of phytoplankton blooms, including the occurrence of red tides, are discussed. The maximum flux of nutrients and, accordingly, phytoplankton blooms should be expected in the years with the highest volcanic activity and high summer air temperatures, since the melting of nutrient-rich snow and ice will be maximum. This will determine the flux of nutrients in the river runoff of the Kamchatka Peninsula and contribute to phytoplankton blooms.

Destruction mechanism of organic matter enrichment controlled by tectonism in the lower Silurian organic-rich marine mudstone in the western South China Block

This destruction mechanism of organic matter enrichment plays an important role in improving the mudstone sedimentary structure system. For the lower Silurian marine mudstone in the western South China Block, the destruction mechanism of organic matter enrichment is unclear, with previous studies ignoring the control from paleogeography and spatial differences. Lamination is a typical sedimentary structure in mudstone and different types of lamination in mudstones can reflect a range of depositional environments. Lenticular lamination, composed of arranged lenses of variable composition, is a common type of lamination in marine mudstone and mainly occurs in organic-lean mudstone. The origin of lenticular lamination remains controversial, and a multidisciplinary approach is needed that integrates sedimentology, petrography, and paleogeography. The main objectives of this approach are to (1) interpret the formation mechanism of lenticular laminations in the Longmaxi marine mudstone, and (2) discuss the significance of lenticular lamination to organic matter destruction. The results not only allow for a complete understanding of the destruction mechanisms of the Silurian marine mudstones but also provide new insights into the sedimentary processes of marine mudstone.

Relationship between coal composition, coal facies, and desorbed methane gas content: Thermal histories and exhumation processes in the middle Magdalena Valley basin, Colombia

We analyzed a total of 25 coal samples from high volatile bituminous to medium volatile bituminous range from 2 wells drilled in the Landázuri area of the Middle Magdalena Valley Basin at the Eastern Colombia Cordillera. This study reveals the relationship between the measured gas concentration, petrographic characteristics, and coal facies. We identify that gas desorption in coal seams is related to maceral composition.Three coal seam groups were defined in Landázuri 1 based on petrographic and statistical evaluation. Two groups were identified in Landázuri 2 based on gas content.The evaluation of maceral content and preservation of reflectance vitrinite found that the highest desorbed gas values correlate with the abundance of inertinite and structured inertinite macerals, followed by the percentage of vitrinite. Structured inertinite lumens may serve as macro/mesopores which allow for higher gas desorption because they are free of mineral matter or other macerals.Using existing coal facies diagrams, two types of coal facies were differentiated: lower delta plain (fen, marsh) and back-barrier low moor developed in a humid environment, where reotrophic conditions prevail and herbaceous and aquatic/marginal vegetation predominate.The relationship of these transitional facies with gas content shows are not directly related to the higher gas values measured at Landázuri. Instead, the relationship between the high degree of destruction of organic matter in these facies (marine incursions and other flows) and the measured gas content shows the importance of quantifying the structured macerals as potential gas retainers.Using low-temperature thermochronometers apatite fission-track, and (U–Th)/He in zircon, combined with vitrinite reflectance data, we reconstructed time-Temperature histories for areas near the wells. Differences in gas content can be explained by an asynchronous behaviour of the burial-cooling processes in this part of the Colombian Eastern Cordillera. Our work shows it is possible to distinguish gas desorption in coal seams based on the maceral composition.

Microbial Diversity and Authigenic Mineral Formation of Modern Bottom Sediments in the Littoral Zone of Lake Issyk-Kul, Kyrgyz Republic (Central Asia).

This article presents geochemical, mineralogical and microbiological characteristics of five samples of modern bottom sediments in the littoral zone of the high-mountain salty lake Issyk-Kul. The 16S rRNA gene sequencing method shows that the microbial community consists of organic carbon degraders (representatives of phyla: Proteobacteria, Chloroflexi, Bacteroidota and Verrucomicrobiota and families Anaerolineaceae and Hungateiclostridiaceae), photosynthetic microorganisms (representatives of Chloroflexi, phototrophic Acidobacteria, purple sulphur bacteria Chromatiaceae and cyanobacteria) and bacteria of the reducing branches of the sulphur biogeochemical cycle (representatives of Desulfobacterota, Desulfosarcinaceae and Desulfocapsaceae). The participation of microorganisms in processes in the formation of a number of authigenic minerals (calcite, framboidal pyrite, barite and amorphous Si) is established. The high diversity of microbial communities indicates the presence of labile organic components involved in modern biogeochemical processes in sediments. The active destruction of organic matter begins at the water-sediment interface.

ECOLOGICAL WATER QUALITY

Water quality – is a description of water’s chemical and biological composition and physical properties, which characterize it as an abiotic component of aquatic ecosystem and determine its suitability for specific consumption purposes.
 Ecological water quality (environmental water quality) – refers to the ecological  well-being of  an aquatic ecosystem, with the main focus on protection of the aquatic environment and human life and health. It comprises a complex of physical,  chemical,  biological  and  other  parameters  reflecting specific features of abiotic and biotic components of aquatic ecosystems.
 The requirements for physical, chemical and biological properties of water are set in the water quality standards, which may be developed by particular countries or introduced by international organizations.
 Ecological water quality depends upon natural and human factors. Natural factors are in their turn divided into abiotic (for example, geological, meteorological, hydrological) and biotic (for example, the ratio of primary production and organic matter destruction). The main human factors affecting water quality include  artificial  modification of  aquatic ecosystems’ hydrological conditions  and  their pollution with diverse chemical compounds.
 There are a lot of approaches to  ecological  water quality  assessment according  to both  abiotic (physical and chemical) and biological parameters. Physical and chemical methods take into account such parameters as water transparency, suspended particulate matter concentration (turbidity), ion composition, water hardness, total dissolved salts content, nutrients and organic matter  content, dissolved  gases  concentration,  pH.  Biological  methods  are  based  upon  assessing  the  living organisms’ (biological indicators’) response to mineral and organic substances, present in water. Various living organisms can be used as biological indicators: algae, in particular – diatoms, higher aquatic plants, different species of aquatic invertebrates and fishes. While physical and chemical methods characterize water quality at the moment of sampling, biological  methods  provide  an integral picture of water quality for a certain time period. Besides, biological methods are more informative, because they reflect the aquatic ecosystem’s response to pollution.
 On the whole, the most reliable data on ecological water quality can be obtained by combining physical, chemical and biological methods.

Primary production and destruction of organic matter in Lake Arakhley (Eastern Transbaikalia, Russia)

Global climate changes affect water ecosystems. Long-term observations of climatic variables are indicative of cyclic climate changes. The fluctuations result in changes in water levels in lakes, which, in turn, alter primary production processes. Planktonic algae are the main drivers of primary production. This research continues long-term studies on hydroecology of Lake Arakhley. The lake is used for fishery and recreation. This work aims to estimate production and destruction processes in Lake Arakhley during the current transitional period between dry and wet years. To this end, we performed field studies on Lake Arakhley in August from 2016 to 2021, during the season of maximum precipitation, in the central and littoral zones of the lake. Primary production of phytoplankton in water was estimated by the oxygen light and dark bottle method. Sampling was carried out to assess physical and chemical parameters of water using a multiparameter water quality instrument. Lake Arakhley features the low level of mineralization under alkali conditions and relatively stable level of mineralization registered from 2016 to 2021. Macrophytes zone expanded after the massive flooding of the shore in 2021 hence alterating the values of such environmental factors as oxygen levels, total and mineral phosphorus, with destruction prevailing over organic matter production. Depth and transparency however contribute to significant production of organic matter in the lake. The findings can be used as the groundwork for the sustainable management of the lake.

Structural and Functional Changes in Bacterial Population of the Lake as a Response to Hydrotechnical Construction (by Example of Opechen Nyzhne Lake, Kyiv, Ukraine)

The paper deals with structural and functional indicators of bacterioplankton and bacteriobenthos of Opechen Nizhny Lake before (2016-2018) and after (2019-2021) its hydrotechnical reconstruction and improvement of the surrounding areas are presented. The analysis of seasonal dynamics of bacterioplankton, bacteriobenthos, eutrophic and oligotrophic bacteria, bacteria with a damaged cytoplasmic membrane (dead cells) and bacteria with active electron transport chain (alive cells) number in water and bottom sediments, intensity of destruction and bacterial decomposition of organic matter in water was analyzed. Significant development of sanitary-indicative microorganisms in the lake water was revealed. The comparative analysis of the quantitative development and functioning of the bacterial population of the lake over two investigated periods was carried out. The results obtained can be used to reveal the mechanisms of formation and functioning of pollution-resistant microbial communities in anthropogenically polluted and reconstructed water bodies, as well as their role in the self-purification processes.

Destruction of total organic matter and the primary product of phytoplankton in the main reservoirs of Azerbaijan

Destruction of total organic matter and the primary product of phytoplankton in the main reservoirs of Azerbaijan

БАКТЕРИОБЕНТОС САПРОПЕЛЯ СЕРОВОДОРОДНОГО ОЗЕРА ШУНГАЛДАН (НАЦИОНАЛЬНЫЙ ПАРК «МАРИЙ ЧОДРА» РЕСПУБЛИКА МАРИЙ ЭЛ)

The first results of the study of the bacterial community in sapropel bottom sediments of hydrogen sulfide Lake Shungaldan are presented.The quantitative and dimensional-morphological structure was determined, the taxonomic composition of bacteriobenthos was established. The total abundance of bacteria was 11.41×109cells mL-1 of silt, the biomass was 1.15 μg mL-1of silt. A feature of the size-morphological structure is a significant predominance of bacteria with linear sizes of 1.0-2.0 μm (85% of the total abundance) and the dominanceof bacillus-shapedcells (83%). As part of the bacteriobenthos community, 31 taxa, including class Cyanobacteria, family Enterobacteriaceae, 20 taxa of genus and 9 taxa of species ranks.The basis of the community consists of bacteria that carry out the sulfur cycle, and microorganisms with a fermentation type of metabolism. The dominant are sulfate-reducing bacteriaof thegeneraDesulfobacterium, Desulfotomaculum, butyric bacteria of the genusClostridium, Butyrivibrio, anaerobic fermenter-dissipotrofof the genus Spirochaeta, facultative anaerobe Aeromonas.The bacteria of the iron cycle occupy secondary positions. In the sapropel of the lake, one of the main strategies for the destruction of organic matter are implemented – dissimilation sulfate reduction and anaerobic fermentation.

Вплив органічних добрив різного походження на мікробіологічну характеристику ґрунту за вирощування фундука

Goal. To evaluate the influence of organic fertilizers of different origins on the number of microorganisms of the main ecological and trophic groups in the soil for the cultivation of hazelnuts in the conditions of the Southern Steppe of Ukraine. Methods. Generalization and analysis of materials of scientific research, microbiological, field, statistical. The results. In the soil of hazelnut plantations, the dynamics of the development of microorganisms of various eco-trophic groups were studied: ammonifiers, nitrifiers, streptomycetes, spore microorganisms, microorganisms that dissolve organic phosphates, microorganisms that dissolve mineral phosphates, nitrogen fixers, oligotrophs. Conclusions. An increase in the number of microorganisms of the main ecological and trophic groups (ammonifiers, nitrifiers, streptomycetes, spore microorganisms, microorganisms that dissolve organic phosphates, microorganisms that dissolve mineral phosphates, nitrogen fixers, oligotrophs) was established due to the introduction of cattle manure and biofertilizers No. 1 and No 2. The parameters of the mineralization – immobilization coefficient (0.02–0.07) indicate the predominance of the processes of synthesis over the destruction of organic matter in all variants of the experiment. The oligotrophic index (indicator of soil availability with easily digestible nutrients) indicates a high availability of nutrients (0.003–0.03). This shows that the use of organic fertilizers of various origins will not disrupt the functional structure of the soil microbial coenosis.

The use of diffusion chambers in embryotoxic research

Introduction. Currently, there are no standard methodological approaches that allow assessing the danger to human and animal reproduction of poorly soluble chemicals (industrial waste, products of destruction of organic substances, polymer materials), including substances that form complex poorly soluble systems with environmental objects. It may be impossible or ineffective to use standard routes of administration of such substances and complexes to assess their reproductive hazard. An attempt to find an experimental model for conducting toxicological and embryotoxicological studies that allow assessing the danger of prolonged interaction of poorly soluble compounds directly with tissue fluids was the main aim of the work. The study aims to investigate the possibility of using diffusion chambers to assess the reproductive hazard of poorly soluble chemicals. Material and methods. In experiments with chemicals, the researchers placed samples of dry preparations in the inner cavity of one of the rings. Experts sealed the ring on both sides with millipore membranes. The diffusion chambers obtained in this way were implanted into the abdominal cavity or under the skin in the cervical region of female rats during the most sensitive days of pregnancy to pathogenic effects. Results. When implanting diffusion chambers to animals, the possibility of assessing the embryotoxic properties of poorly soluble chemicals, such as bitumen-salt masses, polymer materials and coatings, etc., as well as soil contamination with substances potentially dangerous to the reproductive function of humans and animals is shown. With the help of diffusion chambers, experts assessed the embryotoxic activity of known dysmorphogens, cyclophosphamide, cadmium sulfate, as well as a number of polymer materials (di-paraxilylene film, acrylic acid copolymer, silloxane rubber), Scientists assessed soil contamination with a known insecticide and acaricide - endosulfan. Limitations. In the work, the experts used diffusion chambers with a volume of 400, 900 or 3000 m3. Conclusion. As a result of the experiments conducted, scientists determined that the presented method can be used to assess the reproductive hazard of poorly soluble chemicals (products of destruction of organic matter, polymer and endoprosthesis materials), when assessing the risk of prolonged presence of foreign bodies in tissues, when assessing soil contamination in places of chemical accidents, rocket crashes, storage and destruction of chemical weapons. Ethics. The study was carried out in compliance with the rules of bioethics approved by the European Convention for the Protection of Vertebrates Used for Experimental and Other Purposes (Protocol No. 4 of 8.11. 2022).

Organic Matter Destruction in the Kondopoga Bay, Onego Lake, under Changing Anthropogenic Load

Organic Matter Destruction in the Kondopoga Bay, Onego Lake, under Changing Anthropogenic Load

Controls on the accumulation of Early Cretaceous organic-rich fine-grained deposits in a mixed marine siliciclastic-carbonate distal settings of the Neuquén Basin, central-western Argentina

Deposition of black shales occurred under specific conditions that need to combine in a precise way the rate of production and the rates of destruction and dilution of organic matter. Whereas good progress has been made in the determination of the role of production and destruction of organic matter, the role of dilution of the organic components still remains comparatively understudied. In mixed siliciclastic-carbonate marine systems, the dilution of organic matter by non-organic components could be detrital and/or biogenic in origin, adding more complexity to the understanding of these particular types of black shales. In the present contribution, we studied the mixed siliciclastic-carbonate distal deposits of the late Hauterivian Agua de la Mula Member (Agrio Formation) in the Neuquén Basin. Through a combination of sedimentological, petrographic, SEM, and geochemical analyses we define the origin of the fine-grained components, reconstruct the environmental evolution, and determine the role of the production, preservation, and dilution of the organic matter. The results indicate that the unit is predominantly composed of calcite (>47%), whereas illite is the major component among the clay minerals. Thin sections and SEM studies suggest that the carbonate fraction is dominantly composed of nannofossils, i.e. biogenic in origin, and subordinately micarbs (diagenetic, but with a potential biogenic precursor). Thus, the composition of the distal deposits is mostly controlled by the input of detrital illite. The organic geochemistry and XRF data reveal that the most appropriate conditions for the accumulation of organic matter are the transgressive intervals, near the base, with a predominant effect of the rate of the production over the preservation. On the other hand, the dilution of organic matter is mainly driven by the rate of production of biogenic calcite. Interestingly, previous studies showed that in more proximal settings (but still offshore to basin realms) the dilution is controlled by siliciclastic components. Finally, organic geochemistry suggests that most of the organic matter produced is marine in origin (type II), but towards the top of the section it switches to mixed marine and terrestrial (type III to IV), likely related to a progradation of the shallower system and the consequent increase in the input of terrestrial-derived components.

ГЕОХИМИЯ РАННЕГО ДИАГЕНЕЗА ЛИМНОГЛЯЦИАЛЬНЫХ ОТЛОЖЕНИЙ НА ПРИМЕРЕ ОЗЕР НОРИЛО-ПЯСИНСКОЙ ВОДНОЙ СИСТЕМЫ (РОССИЙСКАЯ АРКТИКА)

For the first time, some features of the early diagenesis of bottom sediments of glacial lakes in the Arctic zone of Russia (Pyasino and Melkoe) were studied using long drilling cores. For the first time, the chemical composition of pore waters for the entire thickness of bottom sediments was determined for the lakes of the Russian Arctic. The enrichment of pore waters with biogenic compounds NO3 –, PO4 3– and dissolved organic carbon (DOC) is shown to be a consequence of microbiological destruction of organic matter (OM), as a result of which the labilest components of OM pass into the pore water, and reducing environment arises in the sediments. An increase in Fe, Mn, Al, As, B, Ba, Co, Mo, Ni, Si, Sr, V, Y concentrations in pore waters was found in comparison with supra-bottom water due to the diagenesis of bottom sediments. The role of OM in changes concerned with mineral composition of sediments and formation of authigenic minerals (pyrite, calcite) was shown. Sediments poor in OM are characterized by low concentrations of reduced forms of S (sulphur in the composition of Fe sulphides, H2S, thiosulphfates, etc.), which indicates a low intensity of bacterial sulfate reduction processes.

Potent Effects of Green Synthesized Zinc Nanoparticles Against some Cariogenic Bacteria (Streptococcus mutans and Actinomyces viscosus)

Objectives: Tooth decay is an irreversible complication of calcified tooth tissues that is characterized by demineralization of the inorganic part and destruction of organic matter in the tooth and often leads to the formation of cavities. In the present study, we investigated the antibacterial effect of zinc nanoparticles (ZnNPs) green synthesized with Lavandula vera DC. by microwave method on Streptococcus mutans and Actinomyces viscosus compared with chlorhexidine. Material and Methods: ZnNPs were green synthesized using L. vera extract using the microwave and were characterized by scanning electron microscope, X-ray diffraction technique, nano-sizer-zetacizer, and Fourier-transform infrared spectroscopy. Antibacterial effects were evaluated through determining the minimum inhibitory concentration (MIC) of ZnNPs in comparison with chlorhexidine on standard strains of S. mutans and A. viscosus, by microbroth dilution method according to Clinical and Laboratory Standards Institute guidelines. Results: The absorption peak of ZnNPs was in the range of 230–330 nm. The size of ZnNPs varied from 30 to 80 nm, while most nanoparticles were between 50 and 60 nm. The best MIC related to ZnNPs + chlorhexidine was reported with 1.66 and 1.66 μg/ml for S. mutans and A. viscosus, respectively. Furthermore, the lowest MICs related to ZnNPs alone were obtained with 13.33 and 16.33 μg/ml for S. mutans and A. viscosus, respectively. ZnNPs + chlorhexidine in comparison with chlorhexidine had a significant (P < 0.05) antibacterial effect and inhibited the growth of both bacteria. Conclusion: ZnNPs especially combined with chlorhexidine exhibited promising antibacterial effect in comparison with chlorhexidine alone. However, further studies are needed to clarify the accurate mechanisms and toxicity of ZnNPs.