Oxygen regime of rivers in the area of sources of economic impact according to long-term monitoring of the Russian meteorological service

The results of long-term observations of the hydrochemical service of the Russian Meteorological Service on the content of dissolved oxygen in the rivers of Russia are considered. Data on the basins of the Amur, Lena, Ob, Volga for 1988-2007 is analyzed. We compared the average monthly oxygen concentrations above and below the sources of exposure – cities, large industrial enterprises – in total, about 100 paired sections were used. The study showed that in about half of these river sections, sometimes (in 14.8 % of cases) small changes in oxygen concentration (6.5-8.3 %) are observed. Wherein, both a decrease and an increase in oxygen concentration can occur below the sources of anthropogenic impact. The latter is typical for winter time, when the flow of heated wastewater into the river leads to formation of an air-hole and the flow of oxygen from the atmosphere into the water. Small rivers in cities experience the greatest stress; however, in general, for all the rivers under consideration, the anthropogenic change in the oxygen regime of the rivers is small and does not significantly affect the sustainability of the development of the territories.

ON MONITORING THE HYDROLOGICAL AND HYDROCHEMICAL REGIME OF THE BLACK SEA WATERS

The article briefly describes the main facts and milestones in the development of methods for monitoring the hydrological and hydrochemical state of the Black Sea waters from the 19th century to the present day. It is shown that the modern understanding of the hydrological and hydrochemical processes of this unique sea basin resulted from the intensive work of many oceanographers over the past centuries. Par-ticular attention is paid to the oxygen regime of the Black Sea.

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.

Emission of typical pollutants (NOX, SO2) in the oxygen combustion process with air in-leakages

Oxygen combustion, being an alternative to air combustion, is distinguished in a variety of modern coal management technologies by quick and easy removal of CO2 from the combustion process, which is the key merit of this oxy-fuel technology. The laboratory work conducted so far has not directly addressed the issue of air in-leakages in the oxy-fuel system. The previous studies showed that air in-leakages in the combustion system (both under the air and oxygen regime) occur and affect the combustion process. However, there are no direct research studies on the volume of air in-leakages and their impact on the individual stages of combustion, including the emission of gaseous pollutants. This article focuses on the assessment of the impact of air in-leakages on NOx and SO2 emissions for a single-stage coal-dust combustion system. Moreover, these studies were supplemented with measurements on the rate of devolatilisation of volatile matters and, in particular, on the rate of nitrogen compounds released from fuel. The obtained results of combustion in the oxy-fuel atmosphere with the following air in-leakage levels: 10, 15 and 20% were compared to combustion conditions in the air. Air in-leakages in the oxygen combustion system create an additional flow of oxygen and nitrogen appearing in the combustion area, which affects the course of pollutants and their emission. The conducted studies have shown that when adequate tightness of the combustion system is provided, it contributes to the reduced emission of nitrogen compounds.

Changes in the Oxygen Regime in the Deep Part of the Black Sea in 1980–2019

Purpose. Assessing changes in the oxygen regime of the deep-water part of the Black Sea under the influence of climatic and anthropogenic factors over the past 40 years is the goal of the work. Methods and Results. For the analysis, the expedition data (2015–2019) and those from the Databank of the Marine Hydrophysical Institute, Russian Academy of Sciences, (1980–2013) were used. The data for the deep-water part of the Black Sea (the depths exceeding 200 m) were selected from the array. The data on hydrophysical and hydrochemical parameters were subjected to expert assessment, and those including random errors in the values were excluded from the array. Then the average profiles of temperature, salinity, oxygen concentration, oxygen saturation, and nitrates concentration were plotted in the density scale (σt). Averaging was carried out by the inverse distance method followed by additional smoothing by the low-frequency filtering method. Conclusions. Against the background of the tendency of temperature increase in the upper layers of the water column and decrease of winter convective mixing intensity, the oxygen supply diminishes in all the layers of the Black Sea aerobic zone. Having been analyzed, of the data for the 1980–2019 period showed that at the present stage, a "regime shift" resulting from the joint effect of climate changes and anthropogenic load took place in the ecosystem of the deep-water part of the Black Sea. Decrease in the oxygen saturation of water throughout the entire thickness of the aerobic zone shows that the process of the Black Sea basin eutrophication constitutes a significant factor affecting oxygen dynamics in the Black Sea waters.

Changes in the Oxygen Regime in the Deep Part of the Black Sea in 1980–2019

Purpose. Assessing changes in the oxygen regime of the deep-water part of the Black Sea under the influence of climatic and anthropogenic factors over the past 40 years is the goal of the work. Methods and Results. For the analysis, the expedition data (2015–2019) and those from the Databank of the Marine Hydrophysical Institute, Russian Academy of Sciences, (1980–2013) were used. The data for the deep-water part of the Black Sea (the depths exceeding 200 m) were selected from the array. The data on hydrophysical and hydrochemical parameters were subjected to expert assessment, and those including random errors in the values were excluded from the array. Then the average profiles of temperature, salinity, oxygen concentration, oxygen saturation, and nitrates concentration were plotted in the density scale (σt). Averaging was carried out by the inverse distance method followed by additional smoothing by the low-frequency filtering method. Conclusions. Against the background of the tendency of temperature increase in the upper layers of the water column and decrease of winter convective mixing intensity, the oxygen supply diminishes in all the layers of the Black Sea aerobic zone. Having been analyzed, the data for the 1980–2019 period showed that at the present stage, a “regime shift” resulting from the joint effect of climate changes and anthropogenic load took place in the ecosystem of the deep-water part of the Black Sea. Decrease in the oxygen saturation of water throughout the entire thickness of the aerobic zone shows that the process of the Black Sea basin eutrophication constitutes a significant factor affecting oxygen dynamics in the Black Sea waters.

The influence of different oxygen regimes on metabolism and behavior of a soft shell clam Mya arenaria

<p>Hypoxia is widely distributed in coastal benthic habitats and is driven by warming, nutrient pollution and the diurnal cycles of photosynthesis and respiration. Benthic sessile species, such as the soft shell clam <em>Mya arenaria</em>, are commonly exposed to oxygen fluctuations in their habitats which might negatively impact the performance and metabolism of clams. To determine the effects of different oxygen regime on metabolism and behavior of <em>M. arenaria</em>, we exposed the clams for 21 days to chronic (constant) hypoxia at 20% of air saturation, fluctuating (cyclic) hypoxia (~10-50% of air saturation) and normoxia (100% of air saturation). To mimic conditions occurring in coastal hypoxic zones, CO2 and pH levels varied with the oxygen. We assessed the digging performance, bioirrigation capacity and bioenergetics of the clams. Acclimation to constant or cyclic hypoxia did not affect the oxygen consumption of the clams, but the oxygen consumption rates declined at low ambient oxygen concentrations regardless of the acclimation to different oxygen regimes. Clams acclimated to constant hypoxia mainly used lipids, whereas clams acclimated to cyclic hypoxia used carbohydrates as energy fuel. Clams acclimated to constant or cyclic hypoxia dug slower compared to the clams acclimated to normoxia. Furthermore, bioirrigation capacity decreased in clams acclimated to constant hypoxia. Our results indicate that constant and cyclic hypoxia impair bioturbation and bioirrigation capacity of clams which has implications for their ecological function as ecosystem engineers in benthic soft bottom habitats. </p>