Oxygen-deficient Conditions Research Articles

Regulation of magnetism on Fe- and Ni-doped SnO2 (1 1 0) surfaces by oxygen vacancy and adsorbed O2 molecule

We investigated the ferromagnetism of Fe- and Ni-doped SnO2 (110) surfaces and the regulation of the ferromagnetism on doped surfaces by the oxygen vacancy and adsorbed O2 molecule. The introduction of Fe/Ni dopant can make the nonmagnetic SnO2 (110) surface have a magnetic moment of 3.45 µB/1.97 µB and exhibit stable ferromagnetic coupling. After forming oxygen vacancy under oxygen-deficient conditions, a fraction of the remaining electrons provided by vacancy is acquired by the doped atom, which reduces the number of unpaired electrons in the doped atom d shell, thereby reducing the surface magnetic moment by about 0.6 µB. The oxygen vacancy reduces the magnetization of the bound magnetopolaron, which leads to the weakening of the surface ferromagnetic coupling. The free O2 molecule can exothermically adsorb on the defect surface and fill the oxygen vacancy, forming a magnetic cluster with the doped atom. Although the magnetic moment of the spontaneously adsorbed O2 molecule decreases due to obtaining a small number of electrons from the surface, the magnetic moment of the O2-adsorbed surface increases about 1.0 µB. The magnetic coupling of the O2-adsorbed surface is determined by the competition mechanism of antimagnetic coupling between O2 molecules and ferromagnetic coupling between magnetopolarons.

Содержание нейроглобина в нейронах теменной коры и гиппокампа крыс с церебральной ишемией различной степени тяжести

Introduction. The role of neuroglobin ischemia is still unclear. Some studies indicate its neuroprotective effect due to increased expression of endothelial NOS. Other evidence refutes its significance for neuronal survival under oxygen-deficient conditions, as neuroglobin deficiency appears to increase HIF-1α expression. Materials and methods. The experiments were performed on 56 male outbred white rats weighing 258±18 g. Total cerebral ischemia was simulated by decapitation of animals, whereas the subtotal one was simulated by simultaneous ligation of both carotid arteries. Stepwise subtotal cerebral ischemia was performed by ligating both carotid arteries with an interval of 7 days (subgroup 1), 3 days (subgroup 2), or 1 day (subgroup 3). Results. The study found significant differences in neuroglobin content across three subgroups. In subgroup 1, there was a notable increase in neuroglobin content compared to the control group, with a 13% increase in the parietal cortex (p<0.05) and a 14% increase in the hippocampus (p<0.05). However, subgroup 2 showed a decrease in neuroglobin content, with a 13% decrease in the parietal cortex (p<0.05) and a 7% decrease in the hippocampus (p<0.05). The most significant decrease in neuroglobin content was observed in subgroup 3, with a 31% decrease (p<0.05) in the parietal cortex and a 33% decrease (p<0.05) in the hippocampus. In subgroup 3, the parietal cortex showed a 40% decrease in neuroglobin content compared to subgroup 1 (p<0.05) and a 21% decrease compared to subgroup 2 (p<0.05). Similarly, the hippocampus exhibited a 42.6% decrease in neuroglobin content compared to subgroup 1 (p<0.05) and a 28% decrease compared to subgroup 2 (p<0.05). Conclusion. Thus, the most pronounced disorders of the prooxidant-oxidant balance decreased neuroglobin were observed during a 1-day total cerebral ischemia. Keywords: neuroglobin, ischemia, pyramidal neurons, hippocampus, parietal cortex

Dissolved trace metals (Fe, Mn, Pb, Cd, Cu, and Zn) in the eastern Indian Ocean

The distribution of trace metal micronutrients, which are crucial in many biotic enzymatic reactions, in the eastern Indian Ocean is not well understood. Here, we measured the concentrations of dissolved iron (dFe), manganese (dMn), lead (dPb), cadmium (dCd), copper (dCu), and zinc (dZn) at full depth in the water column of the eastern Indian Ocean (from the Bay of Bengal to the south of the equator). Throughout, dFe was replete in the surface mixed layer (SML). Moreover, the supply of dFe from below the SML and atmospheric deposition met the phytoplankton demand. In the thermocline, the subsurface maxima of dFe coincided with the dissolved oxygen (DO) minima. In addition, the distribution of Fe* in the Bay of Bengal indicated an additional input of dFe into the water column, apart from the biogenic organic particle regeneration. Unlike dFe, other trace metals were not enriched in the oxygen minimum zone, indicating that high Fe* value was caused by the release of dFe from the estuary or continental shelf under oxic conditions. In deep water, dFe, dMn, and dPb levels were low, whereas dCd, dCu, and dZn concentrations increased with depth. However, dFe and dMn levels were elevated in coastal bottom waters, where Fe* values were also high, indicating the supply of these metals from external sources. Exploring the relationship between trace metals and phosphate at the thermocline illustrated how oxygen-deficient conditions in the Bay of Bengal affect trace metal (dCd in particular) and phosphate ratios, compared with the global trend.

Changes of the activity of glutamine synthetase in an experimental model of hypoxic preconditioning

In the present work, the effect of hypoxic preconditioning on the activity of glutamine synthetase in the brain structures of old rats subjected to severe hypoxia was studied. The study of metabolic changes, in particular, some enzymes of glutamate metabolism, in the brain under conditions of oxygen deficiency and during hypoxic training is an actual problem, the solution of which makes it possible to determine possible ways to protect the nervous tissue from hypoxic damage and increase its stability. Hypoxia does not always induce cell death; under certain conditions, hypoxic exposure has a neuroprotective effect. Hypoxic preconditioning increases the resistance of neurons to the effects of more severe forms of hypoxia. In particular, the endogenous neuroprotective mechanism is triggered, the activity of glutamine synthetase increases, and, as a consequence, the neurotoxicity of glutamate decreases.

Analysis of oxidative modification of rat epididymal mitochondrial proteins under normobaric chronic hypoxia and modulation of nitric oxide (II) synthesis

Background. The molecular mechanism of NO effects in adaptation to hypoxia is of interest as a potential point of application in the therapy of fertility disorders.
 Aim. To assess the degree of oxidative modification of epididymal mitochondrial proteins during hypoxia under conditions of experimentally modified NO synthesis.
 Material and methods. Sexually mature rats were divided into four groups of 8 individuals: (1) control (animals without hypoxia); (2) chronic normobaric hypoxia, the animals were kept in a sealed chamber with oxygen reduced to 10% once a day for 14 days; (3) animals with hypoxia were injected with an inhibitor of the synthesis of nitric oxide (II) L-nitroarginine methyl ester at a dose of 25 mg/kg intraperitoneally once a day for 7 days; (4) animals with hypoxia were injected with the substrate for NO synthesis L-arginine at a dose of 500 mg/kg intraperitoneally once a day for 10 days. In the mitochondrial fraction of the head and tail of the epididymis, the activity of superoxide dismutase, the amount of NO metabolites, and the degree of oxidative modification of proteins were evaluated. Statistical analysis was performed using the ShapiroWilk, MannWhitney, and Spearman tests; differences were considered significant at p 0.05.
 Results. Hypoxia led to an increase in the oxidative modification of proteins in the mitochondria of the head of the epididymis 319.12 [240.98; 363.63] c.u./mg protein relative to control 17.89 [15.31; 27.62] c.u./mg protein, p=0.0009. In the mitochondria of the tail of the epididymis, the oxidation of proteins under the studied conditions was less pronounced. The use of L-nitroarginine methyl ester, as well as L-arginine, led to a decrease in the level of oxidative modification of proteins in the head of the epididymis relative to the hypoxia model 39.89 [29.25; 43.17] and 37.25 [34.91; 40.96] c.u./mg of protein, respectively, p=0.0009.
 Conclusion. Mitochondrial proteins in the head of the epididymis are more susceptible to oxidative damage during hypoxia; a decrease in the level of NO metabolites under conditions of oxygen deficiency is associated with a decrease in the oxidative modification of mitochondrial proteins.

Formation of the amorphous multicomponent iron-based alloy during carbothermal reduction of Fe2O3 by waste activated sludge

The process related to the formation of a multicomponent amorphous material during the reduction of α-Fe2O3 with the products of thermodestruction of WAS is studied using x-ray powder diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDS). Because WAS contains sand and clay along with its bio-components, the thermal treatment of WAS is accompanied by the formation of amorphous carbon, SiO2, Al2O3, and multicomponent alloys. At T = 1000 °C, under oxygen-deficient conditions, iron oxide was reduced according to the scheme: α-Fe2O3 → (amorphous phase)main part + (Fe + Fe0.94O)(crystalline)little part. The main product of the Fe2O3 reduction is amorphous iron with a lamellar structure. Newly formed amorphous alloys form interlayers between the iron plates and 3D inclusions. Inclusions of C, SiO2, and Al2O3 agglomerates are observed between the lamellar packs. This macrostructure of the material allows slow cooling of the 3D-samples while preserving the amorphous state of iron.

Paleoenvironment-driven organic matter accumulation in lacustrine shale mixed with shell bioclasts: A case study from the Jurassic Da'anzhai member, Sichuan Basin (China)

The sedimentary environment governs the depositional processes, ecological environments, and hydrodynamics, which affect the accumulation of organic-rich sediments. Some particular issues are unsolved about the organic matter accumulations of lacustrine shale mixed with shell bioclasts due to their alternating deposition. Freshwater bivalve remains are a familiar constituent of the Da'anzhai lacustrine calcareous shale, which indicates enhanced activities of benthic organisms. Under this background, favorable environmental conditions for the deposition and preservation of abundant organic matter may be different from classical models. Total organic carbon and elemental concentration analyses of lacustrine calcareous shale samples from the Jurassic Da'anzhai Member in the Sichuan Basin were carried out to reconstruct the paleoenvironment and reveal the organic enrichment mechanism. Results show that the samples are notably enriched in strontium, phosphorus and biogenic calcium (indicated by excess calcium concentrations) and reveal the mass death event of benthic organisms (including freshwater mussels and gastropods) in paleolakes under the control of climatic transformation. Such enrichment strongly supports the hypothesis that CaO is considered to be a paleoproductivity proxy to some extent. The paleolake was dominated by a warm and humid climate and rapid sedimentation rates and experienced intense chemical weathering, which are characteristic of freshwater input and a high flux of detrital fractions. The variations in the redox state and paleoproductivity are due to climatic shifts, hydrographic restrictions and biological behavior. Furthermore, the organic matter was enriched during both oxygenated and oxygen-deficient conditions. The combination of high sedimentation rates and high sinking influxes of particulate organic carbon reduced the chances of decomposition and thereby facilitated the efficiency of organic matter accumulation in an oxic environment. The low degree of organic matter degradation, moderate sedimentation rates and enhanced phosphorus recycling were responsible for the organic carbon accumulation and preservation in sediments for dysoxic bottom conditions.

Copper catalyzed co‐pyrolysis of polyethylene terephthalate with low and high density polyethylene for liquid fuel production

AbstractBACKGROUNDMunicipal waste contains low density polyethylene (LDPE), high density polyethylene (HDPE), and polyethylene terephthalate (PET) in enormous amount. As these plastics are non‐biodegradable and pose serious threats to the environment, efforts have been made towards their safe disposal with energy recovery and value added chemicals by subjecting them to heat under oxygen deficient conditions. This study deals with the co‐pyrolysis of the three types of waste polymers, with special focus on the conversion of PET into liquid fuel by its interaction with the other two polymers.ResultsThe individual pyrolysis of LDPE and HDPE produced pyrolysis oil, whereas PET produced only wax. The co‐pyrolysis of the three polymers with different mixing ratios showed that PET hindered oil formation and increasing its amount more than 20 wt% in the polymer mixture resulted in wax formation. The thermal process produced 8 wt% pyrolysis oil, 32.3 wt% wax, 39.7 wt% pyro‐gases and 20 wt% coke while the catalytic process with copper catalyst produced 32.5 wt% pyrolysis oil, 3 wt% wax, 46.5 wt% pyro‐gases, and 18 wt% coke under optimum conditions.ConclusionThe thermal pyrolysis oil contained long chain paraffins as major components, while short chain isoparaffin and naphthenes were predominant in the catalytic pyrolysis oil owing to which marked differences were observed in the physicochemical properties of both oils. The fractionally distilled fractions of catalytic pyrolysis oil in gasoline, kerosene, and diesel range showed profound similarities with standard fuels in terms of fuel properties particularly the gasoline range fraction. © 2022 Society of Chemical Industry (SCI).

Paleoenvironmental changes during the early Toarcian Oceanic Anoxic Event: Insights into organic carbon distribution and controlling mechanisms in the eastern Tethys

• Unlike N Europe, TOC contents are significantly varied in lower Toarcian sediments of the eastern Tethys . • Anoxic, but non-sulfidic conditions prevailing during the T-OAE. • Humid climates promoted moderate continental weathering during the T-OAE. • Marine productivity was commonly high during the T-OAE in the eastern Tethyssouthern Qiangtang Basin. • Organic carbon burial and oil shale accumulation sustained by increased primary productivity. The Toarcian Oceanic Anoxic Event (T-OAE; Early Jurassic, ca. 183 Ma) represents an intense Mesozoic organic carbon burial event that was associated with the formation of oxygen-deficient conditions at paleo-shelf seas, as well as in lacustrine settings. Global scale increase in organic carbon accumulation occurred in connection with profound changes in climate conditions and perturbations of biogeochemical cycles. This study presents geochemical data for lower Toarcian and Bajocian-Bathonian sediments exposed in the Bilong Co section, located in the southern Qiangtang Basin of central Tibet. During Early and Middle Jurassic times, the study site was located in the north-eastern marine of the Tethys Ocean. A total of 83 rock samples, spanning the Quse (lower Toarcian) and Sewa formations (upper Bajocian-Bathonian), were analyzed for their total organic carbon (TOC) content, carbon isotopes of bulk carbonate and kerogen, as well as major and trace elements. Data allowed to assess changes in the environmental conditions in the eastern Tethys Ocean and further allowed to reconstruct changes in paleo-weathering conditions, marine primary productivity, and redox regimes that occurred in association with the T-OAE. In addition, factors that controlled the accumulation of organic material in the sediment are discussed. Enrichment factors (EF) of redox-sensitive trace elements, their relationship with TOC, and C org /P total molar ratio attest to predominantly anoxic pore and bottom waters in southern Qiangtang Basin during the T-OAE. On the contrary, oxic conditions prevailed during pre- and post-T-OAE times. During the T-OAE, the development of anoxic conditions were most likely linked to an increase in marine primary productivity, as revealed by C org /P total molar ratio, as well as Al-normalized Ba, and Zn concentrations, and their relationship with TOC. Data further attest to a moderate to low marine primary productivity during pre- and post-TOAE times. During the T-OAE, an increase in the marine primary productivity was linked to intensified continental weathering, facilitated by semi-humid climate conditions. Compilation of TOC data from various depositional settings in the eastern Tethys Ocean revealed a high spatial variability, highlighting the importance of local intrabasinal processes on organic matter accumulation.

Weakening of the biological pump induced by a biocalcification crisis during the early Toarcian Oceanic Anoxic Event

Severe environmental changes during the early Toarcian (Early Jurassic; ∼182 Ma), comprising global warming, elevated pCO2, intensified continental weathering and a high amplitude sea level rise, led to the genesis of a Toarcian Oceanic Anoxic Event (T-OAE), expressed by the widespread occurrence of organic carbon (OC)-rich sediments (black shales) forming on anoxic epicontinental shelves. Here, we show that during the T-OAE black shales in some depocenters have formed under rather low organic carbon accumulation rates (OCAR). We explain this observation by a reduced export efficiency of OC to the sediment, caused by a drastic decline in the abundance of mineral ballast, due to a major biocalcification crisis and the demise of calcareous nannoplankton. The reduction of mineral ballast led to slowing of the sinking speed of particulate organic matter, which thus became more prone to biodegradation. A major sea level rise, accompanying the T-OAE, was associated with retrograding shorelines and shift of depocenters away from the basin centers to more coastal areas. This might have reduced nutrient fluxes to the distal depocenters and diminished surface productivity and export flux in the central basin. Moreover, during sea level rise reduced input of clastics from adjacent landmasses may have led to a decline in organic carbon dilution. A decline in both abundance and size is documented for faecal pellets in core FR-210-078 from the Lorraine Basin, substantiating the scenario of reduced marine primary productivity and organic matter transport efficiency. Accordingly, during the T-OAE low OCAR are here interpreted to reflect a weakening of the biological pump. These new data substantiate the role of organic matter preservation as major factor controlling the formation of black shales during the T-OAE. The Toarcian marine transgression led to an increase in the extent of shelf areas, accompanied by an expansion of oxygen-deficient conditions that favored the preservation of organic matter in shelf sediments. Consequently, despite low OCAR, net C-burial in shelf sea sediments increased during the T-OAE, which may have acted as negative feedback mechanism that caused global cooling in the aftermath of the event.

Obtaining Electroheating Elements Based on Products of Carbothermal Reduction of Fe2O3 by Waste Activated Sludge (WAS)

In this work, the prospects of fabrication of heating elements from heat-treated (sintered) mixtures of waste-activated sludge (WAS) and Fe2O3 under oxygen deficiency conditions are considered. During heat treatment of mixtures in the 800–900 °C temperature interval, Fe2O3 reduces to Fe3O4, Fe0.94O, and Fe. A heat treatment at 1000 °C leads mainly to the formation of amorphous iron doped with carbon, silicon, and aluminum. Based on these compacted mixtures, having different electrical resistivity (from ~ 10–4 up to 10–1 Ω·m), it is possible to fabricate heating elements, whose working temperature ranges from ~ 100 °C up to 600 °C.Graphical

The Role of Aquaporins in Plant Growth under Conditions of Oxygen Deficiency.

Plants frequently experience hypoxia due to flooding caused by intensive rainfall or irrigation, when they are partially or completely submerged under a layer of water. In the latter case, some resistant plants implement a hypoxia avoidance strategy by accelerating shoot elongation, which allows lifting their leaves above the water surface. This strategy is achieved due to increased water uptake by shoot cells through water channels (aquaporins, AQPs). It remains a puzzle how an increased flow of water through aquaporins into the cells of submerged shoots can be achieved, while it is well known that hypoxia inhibits the activity of aquaporins. In this review, we summarize the literature data on the mechanisms that are likely to compensate for the decline in aquaporin activity under hypoxic conditions, providing increased water entry into cells and accelerated shoot elongation. These mechanisms include changes in the expression of genes encoding aquaporins, as well as processes that occur at the post-transcriptional level. We also discuss the involvement of hormones, whose concentration changes in submerged plants, in the control of aquaporin activity.

Sulphur Isotopic Evidence for Upwelling of Anoxic Deep Water as the Cause of End-Permian Mass Extinction from Guryul Ravine Permo-Triassic Boundary Section, Kashmir, India

Abstract The Guryul ravine section in Kashmir, northern India represent archetypal Permian-Triassic Boundary (PTB) section, comprising conformable successions of mixed siliciclastic-carbonate sediments deposited in deep-shelf setting. Availability of high quality sedimentological and fossil records provides unique opportunity to examine the oceanic redox condition across PTB. Here, pyrite sulphur isotopic data, along with total organic carbon (TOC) and redox-sensitive trace elements (RSE) is reported from ~28m thick succession across the PTB and attempted to investigate the reason behind the biotic crisis. The TOC and RSE data support an overall anoxic condition with a broad de-oxygenation trend with time. Majority of pyrite sulphur isotope data, considering ~17‰ δ34S of contemporary ocean, show relatively low offset (34SSO4-H2S =16.4-22.4 ‰) between the marine sulphate and sulphide across the PTB, indicating low oceanic dissolved sulphate concentration (1.7-3.6 mM) and an overall oxygen deficient anoxic condition. A high magnitude (~22 ‰) negative δ34S excursion event, observed in this study, broadly correlates with the first peak of mass-extinction at latest Permian H. praeparvus – C. meishanensis Zone. Upwelling of deep Ocean 34S-depleted sulphidic water onto the ocean surface layer best explains the negative δ34S excursion, and it is suggested that H2S poisoning is the main reason of mass mortality. The long term ocean stagnation and widespread ocean anoxia might have been caused by high-surface temperature related to gigantic release of greenhouse gases to the atmosphere during Siberian trap magmatism.

Nitrite oxidation in oxygen-deficient conditions during landfill leachate treatment

Until recently, all known nitrite oxidation occurred in oxygen-rich conditions but now the oxidation of nitrite into nitrate within a low oxygen or anoxic environment has been observed in the ocean. However, this phenomenon is rarely reported in wastewater treatments and its mechanism is unknown. In this study, the partial nitrification and nitrite oxidation were conducted in no enough oxygen in order to remove nitrogen from landfill leachate, save energy, and save money. The results show that the NH4+-N removal efficiency was 99.4%. During phase I of the anaerobic sequential batch reactor (ASBR), no change in Chemical Oxygen Demand (COD) and ammonium were detected. The nitrite concentration decreased from 107 ± 3 mg/L to 0.16 mg/L during 96 h of oxygen- deficiency, while NO3−-N increased from 152.5 ± 3 mg/L to 253.65 ± 3 mg/L. The main microorganisms involved in this reaction in the ASBR were Nitrite-Oxidizing Bacteria (NOB), including Nitrospira and Nitrolancea, their relative abundances were 3.56% and 0.13%, respectively. The major NOB (Nitrospira) were confirmed by the further metagenomic binning analysis. This finding shows that nitrite oxidation can occur in oxygen-deficient conditions with specific NOB.

Comparison of Waterlogging Tolerance of Three Peach Rootstock Seedlings Based on Physiological, Anatomical and Ultra-Structural Changes

Peach (Prunus persica (L.) Batsch) is a typical shallow-rooted fruit plant with a high respiratory intensity and oxygen demand, which makes it highly susceptible to oxygen-deficient soil conditions resulting from waterlogging. Rootstock waterlogging resistance is essential to the performance of cultivated peaches under waterlogging stress. In comparison to Prunus persica var. persica (‘Maotao’, M) and Prunus davidiana (Carr.) C. de Vos (‘Shantao’, S), Prunus persica f. Hossu (‘Hossu’, H) exhibited superior leaf photosynthetic electron transfer efficiency, a higher rate of mycorrhizal fungi infection in both fine roots and mesophyll palisade cells, as well as earlier air cavity formation in both leaf midvein and fine roots under waterlogging stress. Furthermore, under non-waterlogging conditions, Hossu had greater leaf superoxide dismutase (SOD) activity, higher proline content, and a greater content of starch granules in the pith and xylem ray cells of stems and roots than rootstocks M and S. As a result, Hossu’s tolerance to waterlogging may be due to its higher photosynthetic efficiency, improved tissue oxygen permeability, higher energy metabolism, and increased intracellular mycorrhizal fungus infection rates in both root parenchyma cells and mesophyll palisade cells.

The impact of the mountain factor on the students» cardiorespiratory system

The work is devoted to studying the influence of mountain hypoxia on the state of the students» cardiovascular and respiratory systems. The results of our research indicate that under conditions of hypoxia, the activity of the respiratory system in students significantly increases while the activity of the cardiovascular system slightly decreases. Thus, the cardiac rate at an altitude of 1,600 m was 72.8 beats per minute for female students and 71.0 for males, with 76.2 and 74.8 beats respectively at 170 m. In the midlands, the value of systolic pressure fell to 113.6 mmHg in girls and 110.8 in young men, with the plain indicators at 117.6 and 114.6. The rhythm of breathing in conditions of oxygen deficiency in the surrounding air does not change. The level of respiratory volume in female students at an altitude of 600 and 1600 m was 0.62 l (P <0.05) and 0.68 (P <0.02), with 0.46 at 170 m. In the midlands, the inspiratory reserve volume in girls was 1.93 l (P <0.02), and in the plains it was 1.74. The VC level at the maximum height was 3.92 l (P <0.05) in female students and 4.42 l in male, and at a height of 170 m — 3.46 and 4.06 l, respectively.

КОМПЛЕКСНИЙ ПІДХІД ДО ОЦІНКИ ЗАБРУДНЕННЯ ВАЖКИМИ МЕТАЛАМИ ЕКОСИСТЕМ МАЛИХ РІЧОК ЗАХІДНОГО ПОДІЛЛЯ

The metal content (Ferrum, Cobalt, Manganese, Zinc, Copper) in water, bottom sediments and tissues of freshwater fish (carp, crucian carp, pike, perch) from small rivers of Western Podillya (Seret, Strypa, Zolota Lypa) was studied. High concentrations have been found in the water and bottom sediments of the Ferrum and Manganese, which is probably due to the inflow of these metals from the bottom sediments in conditions of oxygen deficiency. The high content of mobile form of Ferrum, Cobalt, Manganese in the bottom sediments of the Zolota Lypa can lead to secondary pollution of the water column and pose a potential danger to aquatic organisms. Individual mechanisms of accumulation and distribution in the body of fish were established for different metals. Higher concentrations in the liver and gills of the studied fish species of Ferrum, Manganese and Zinc and significantly lower contents of Cobalt and Copper were observed. The metal content in fish tissues was characterized by high variability, had a pronounced tissue and species specificity. Correlation relations between metal content in water, bottom sediments and fish tissues from small rivers of Western Podillia are analyzed. Positive correlations have been established between the content of the gross form of Ferrum in the bottom sediments, in the gills of crucian carp, perch and pike and the liver of perch and pike. The amount of Manganese in the water correlated with the metal content in the gills of carp and pike. The increase in the amount of Zinc in the bottom sediments (gross form) led to its accumulation in the gills of all fish species, as well as in the liver of perch and pike, as evidenced by the high positive values of Pearson's coefficients (0.71-0.91). The Copper content in water and bottom sediments (gross form) correlated with their amount in the liver of perch and pike, which may serve as a bioindication of pollution of aquatic ecosystems by this metal.

Evaluation of oxygen concentration on low-temperature oxidation kinetics of long-flame coal

Oxygen concentration is the vital environmental factor affecting the evolution of coal spontaneous combustion. Long-flame coal was heated from 30 to 800 °C at different oxygen concentrations (3, 5, 9, 13, 17, and 21 mass%) and heating rates (2.0, 5.0, 10.0, and 15.0 °C/min). The thermal reaction process was explored and analyzed. The effects of oxygen concentration on characteristic temperature and related parameters were assessed. The effects of heating rate and oxygen concentration on characteristic temperature and related parameters were evaluated. Under the condition of oxygen deficiency, the oxidation rate of coal was low, it took more time to consume the active groups in a given quality coal, and the increase of oxygen concentration had a strong positive effect on early and late combustion. The apparent activation energy (Ea) increased and decreased the conversion degree of oxygen absorption (mass gain) and high-temperature combustion stage, respectively. With the decrease of oxygen concentration, Ea in each stage decreased. These results contribute to the understanding of the evolution of coal fires in oxygen-lean environments.

Miocene organic-rich layers of the Saouef Formation (Oriental Tunisia); insights into temporal and spatial variability of environmental conditions during deposition

Miocene organic-rich sediments (coal and carbonaceous clays) from the La Falaise section of the Saouef Formation have been investigated by organic petrographic, palynofacies and organic geochemical approaches. The results are compared with data obtained during a previous study of the nearby Saouef section. The sedimentary succession is built up by repetitive sedimentary sequences (i.e., parasequences) deposited during progradation and retrogradation, respectively. The coal, or carbonaceous layers, developed during the establishment of clay-dominated sedimentation.The organic-rich layers within the samples, containing high amounts of mineral matter, are dark brown, with a stratified texture and are classified as humic coal. Microscopically, the huminite group dominates the maceral composition of the carbonaceous clays and lignite (av. 75% mmf). The variable degrees of the tissue preservation index (TPI) and highly fluctuating vegetation index (VI) values provide evidence for different contributions of vascular plants vs. herbaceous vegetation and macrophytes, to peat formation. Higher contributions of macrophytes (e.g., reed grasses) to peat accumulation at La Falaise are concluded, based on n-alkane distributions. High mineral matter contents and changing gelification index (GI), and ground water index (GWI) values, found in both sections, provide evidence for rheotrophic hydrogeological conditions, and peat formation within wet forest swamp to inundated marsh environment. The low sulphur contents attest to peat formation within a freshwater environment and the relative proportions of ββ to (ββ + αβ)-C31 hopanes argue for slightly acidic conditions. In comparison to the results of the Saouef section (average pH of 5.6), a lower pH (4.2) is revealed from the average hopane isomerization ratio of the La Falaise samples.The palynofacies investigation of the La Falaise deposits indicates the dominance of phytoclasts over amorphous organic matter (AOM) in most of the samples and suggests good preservation of the higher plant remains. In contrast, increased degradation of plant tissues under oxygen-deficient conditions is concluded from the enhanced proportions of AOM found in several of the previously investigated Saouef samples. The molecular analysis of hydrocarbons from all the samples indicated the dominance of n-alkanes and hopanoids. The obtained pristane/phytane ratios argue for sub-oxic conditions during peatification at La Falaise, whereas data from our previous study of the Saouef section provided evidence for a reducing environment. Terpenoid hydrocarbon compositions reveal highly variable contributions of conifers and angiosperms to peat formation, consistent with previous findings at the Saouef sampling site. The presence of polycyclic aromatic hydrocarbons (PAHs), as well as fusinite, provides evidence for mire or forest fires.The comparison of the results from lignite of both sections of the Saouef Formation indicate comparable, highly variable conditions during peat accumulation, probably governed by eustatic sea level changes. The peatlands most likely developed due to the establishment of flood basins situated between alluvial ridges. The obtained regional differences are suggested to reflect slightly different hydrological conditions and associated vegetation cover in the peatlands.

BIOSTRATIGRAPHY AND SEDIMENTARY ENVIRONMENTS OF THE LOWER/UPPER CRETACEOUS BOUNDARY DEPOSITS BY SMALL FORAMINIFERA (PIENINY KLIPPEN BELT, UKRAINIAN CARPATHIANS)

The Pieniny Klippen Belt extends 600 km from the Slovakian Carpathians to the Romanian Carpathians. The Pieniny KIippen Belt narrows in the Ukrainian Carpathians. It is called the Pieniny Zone here. The Cretaceous succession of the Pieniny KIippen Belt in the Ukrainian Carpathians consists of the upper part of the Svalyava Formation (Titonian- Neocomian), Tyssalo Formation (Aptian-Senomanian), Puchov Formation (Turonian-Maastrichtian) and Yarmuta Formation (Maastrichtian). This succession is overlapped by the Eocene Vylhivchyk Formation with angular uncomformity. The Lower/Upper Cretaceuous boundary sediments of the Pieniny KIippen Belt in the Ukrainian Carpathians is located in the Tyssalo Formation. The paper presents the results of the analysis of foraminifera from the marls of the Tysalo Formation developed in the Tysalo tract, in the sections of the Tereblya and Luzhanka rivers, in the quarries of Perechyn and Pryborzhavske villages (Transcarpathians region). 27 species of foraminifera were identified in this study in the age range of Late Albian — earliest Turonian including 15 planktonic species and 4 benthic species. The biostratigraphic succession of foraminiferal subdivisions ranging from late Albian to Senomanian is identified. Upper Albian-Senomanian sediments of the Tyssalo Formation are divided into three lithological members. The lower member consists of black limestones and marls with dark grey limestones which correspond to early Late Albian. The middle member is represented by gray and gray-green marls with gray siltstones and sandstones which correspond to middle Late Albian. The upper member consists of light green-gray marls with pink marls which correspond to late Late Albian-Senomanian. The Hedbergella gaultina Zone (late Late Albian), Pseudothalmanninella ticinensis Zone (middle Late Albian) and Parathalmanninella appeninica Zone (late Late Albian) were identified in the Tyssalo Formation both by previous researchers and in the material presented. The layers with Thalmanninella globotruncanoides (early Senomanian), Thalmanninella reicheli Zone (middle Senomanian) and Rotalipora cushmani Zone (later Senomanian) are established in the Tyssalo Formation for the first time. The Lower/Upper Cretaceous boundary corresponds to the boundary between the Parathalmanninella appeninica Zone and the layers with Thalmanninella globotruncanoides, which are not found in the same section due to the intense deformation of the deposits in the Pieniny KIippen Belt. Changes in the generic composition of planktonic foraminifera in the boundary deposits of the Lower and Upper Cretaceous of the Tysalo Formation are gradual, from the dominance of small Biglobigerinella, Globigerinelloides, Hedbergella, Ticinella in the Upper Albian to the bloom of large complex-built Pseudothalmanninella, Rotalipora, Thalmanninella, Parathalmanninella, Praeglobotruncana Pseudothalmanninella, Rotalipora, Thalmanninella, Parathalmanninella, Praeglobotruncana in the Senomanian. The black marls of the lower member contain pyritized foraminifers, so it can be assumed that they were formed in oxygen-deficient botton-water conditions (early Late Albian). In the middle member change in the color of sediments from black to gray and green and the presence of calcareous benthic foraminifera belonging to genera Parella, Anomalina, Pleurostomella, Gavelinella indicate an improvement in oxygen conditions in bottom waters (middle Late Albian). The marl of the upper member is dominated by (70-100% of associations) planktonic foraminifera mainly from the genera Parathalmanninella, Rotalipora, Thalmanninella, Praeglobotruncana, which indicates the depth of the middle batial (late Late Albian-Senomanian).