During austral summer 1978/1979 the content of dissolved oxygen, phosphates, nitrates and nitrites was determined in the waters of Admiralty Bay. Environmental conditions prevailing in Admiralty Bay are compared with the conditions in the open Antarctic waters.
The concentration or the partial pressure of oxygen in an environment can be determined using different measuring principles. For high temperature measurements of oxygen, ceramic-based sensors are the most practical. They are simple in construction, exploration and maintenance. A typical oxygen potentiometric sensor consists of an oxygen ion conducting solid electrolyte and two electrodes deposited on the two sides of the electrolyte. In this paper different structures of potentiometric oxygen sensors with a solid state reference electrode were fabricated and investigated. The fabricated structures consisted of oxygen ion conducting solid electrolyte from yttria stabilized zirconia, a sensing platinum electrode and nickel-nickel oxide reference electrode. The mixture of nickel-nickel oxide was selected as the reference electrode because it provides reliable electrochemical potential in contact with oxygen conducting electrolyte. To avoid oxidation of nickel the reference electrode is sealed from ambient and the mixture of nickel-nickel oxide was formed electrochemically from nickel oxide after sealing. The effectiveness of the sealing quality and the effectiveness of nickel-nickel oxide mixture formation was investigated by impedance spectroscopy.
In this paper a 600 MW oxy-type coal unit with a pulverized bed boiler and a membrane-cryogenic oxygen separator and carbon capture installation was analyzed. A membrane-cryogenic oxygen separation installation consists of a membrane module and two cryogenic distillation columns. In this system oxygen is produced with the purity equal to 95%. Installation of carbon capture was based on the physical separation method and allows to reduce the CO2emission by 90%. In this work the influence of the main parameter of the membrane process – the selectivity coefficient, on the efficiency of the coal unit was presented. The economic analysis with the use of the break-even point method was carried out. The economic calculations were realized in view of the break-even price of electricity depending on a coal unit availability.
The use of hyperbaric oxygen therapy (HBOT) is an accepted method of supporting wound healing in human medicine. Yet, because of the risk of complications associated with HOBT, a safer modification of the therapy, known as L-HOBT (lower pressure and lower oxygen concen- tration), is increasingly used nowadays. Therefore, due to the lack of literature reports regarding the clinical use of L-HBOT in animals, the authors decided to present the results of L-HBOT supportive treatment of postoperative wounds after hemimastectomy compared to classic treat- ment. The study group included 12 bitches divided into two groups: group A (assisted L-HBOT) and group B (classic treatment). In addition to conventional treatment, the supportive therapy included 1.5 hours of hyperbaric chamber therapy for 5 consecutive days, starting 24 hours after surgery (1500hPa pressure and 26% oxygen concentration in the chamber). The patients were followed and evaluated throughout the course of the treatment by two independent doctors. The results of the treatment revealed no negative clinical impact of L-HOBT supportive therapy on the body of the animals. At the same time, postoperative wounds after L-HOBT healed faster and with fewer postoperative complications compared to the control group. This resulted in a shorter treatment period, terminating with an earlier skin suture removal.
The restoration of the anthropogenic Pławniowice water reservoir with the hypolimnion withdrawal method (the Olszewski's tube) began in December 2003. The decision to restore the reservoir had been taken due to its terrible condition resulting from the hypertrophy, which had been indicated by the research from the years 1993–1998.
The following paper presents the results of eight-year-long research into the formation of oxygen conditions and restoration settings. They were compared with the data obtained from the research before the restoration. Positive changes were witnessed. It was showed that grasping the changes in oxygen conditions enables the comparison of oxygen profiles in the same months in subsequent years. The ratio of anoxic water layer thickness to the oxygenated layer thickness was suggested as a factor characterizing oxygen conditions. The area described with an izooxa in the xy coordinate system was suggested as a factor [O2 mg/m2] allowing researchers to understand and describe occurring changes. It was observed that the oxygen solved in water as a result of the restoration occurred in the whole water column in the third decade of July. The oxygen concentration in the hypolimnion gradually rose in May, June and July each year. It was showed that the improvement in oxygen conditions stemmed from progressing oligotrophy of the reservoir.
Biochemical Oxygen Demand (BOD) is an important factor used to measure water pollution. This article reviews recent developments of microbial biosensors with respect to their applications for low BOD estimation. Four main methods to measure BOD using a biosensor are described: microbial fuel cells, optical methods, oxygen electrode based methods and mediator-based methods. Each of them is based on different principles, thus a different approach is required to improve the limit of detection. A proper choice of microorganisms used in the biosensor construction and/or sample pre-treatment processes is also essential to improve the BOD lower detection limit.
Deoxidation of steel with carbon under reduced pressure is often used for increasing the steel purity. Suitable units for this purpose in
foundries are vacuum induction furnaces. Possibilities of increasing the steel purity by deoxidation with carbon in the vacuum induction
furnace were studied for the steel for the petrochemistry of specific composition 25Cr/35Ni. The charge composed of the return material
only was melted in the air. During melting the charge oxidized and the oxidizing slag formed. Chemical composition of steel, morphology,
chemical composition of inclusions in the steel and chemical composition of slag after vacuuming were studied on the basis of samples
taken before and after vacuuming. Temperature and oxygen activity were measured before and after vacuuming. Globular inclusions with
dominant content of silicon and manganese were observed in steel before and after vacuuming. Contents of total oxygen in steel didn’t
change significantly during vacuuming. On the basis of composition of inclusions and measured oxygen activity the activity of Cr2O3
in
inclusions was calculated. A slag sample was taken after vacuuming and equilibrium oxygen activity in steel with regard to the Cr2O3
content in the slag was estimated from the slag composition. Equilibrium oxygen activity in relation to the Cr2O3 content in the slag was
higher than equilibrium activity measured in the steel. For this reason it is not possible, under the studied conditions, to decrease oxygen
content in steel during vacuuming.
Parameters of surface acoustic waves (SAW) are very sensible to change of physical conditions of a propagation medium. In the classical theory formulation, the waves are guided along the boundary of semi-infinity solid state and free space. A real situation is more complex and a medium commonly consists of two physical components: a solid substrate and a gaseous or liquid environment. In the case of stress-free substrate, the strongest impact on SAW properties have surface electrical and mechanical conditions determined by solids or liquids adhering to the boundary. This impact is utilised for constructing sensors for different gases and vapours e.g. (Jakubik et al., 2007; Hejczyk et al., 2011; Jasek et al., 2012). The influence of gaseous environment on the SAW properties is usually very weak and ignored. However, in certain condition it can be significant enough to be applied to sensor construction. In general, it concerns Rayleigh wave devices where energy leakage phenomenon is perceptible, especially when the gas being detected considerably changes the density of environment. The paper presents the results of experiments with oxygen-nitrogen mixture. Their primary aim was focused on finding the dependence of resonant frequency and attenuation in SAW resonator on parameters and concentrations of the gas in the environment.
Operations conducted by petroleum industry generate an entire range of drilling waste. The chemical composition of drilling waste and its toxicity depend primarily on the geological and technological conditions of drilling, the type of drilled rock deposits and on the type and composition of the drilling mud used. In the course of drilling operations, drilling fluids are in constant contact with bacteria, fungi and other organisms infecting the mud. Pioneer species, capable of surviving and using the resources of this specific environment, are selected. For this reason, the effectiveness of microbiota survival on different types of spent drilling muds and in different dilutions with brown soil was measured. Spent drilling muds samples came from drilling operations in various regions of Poland, e.g. Subcarpathia, the Polish Lowland and Pomerania regions. Oxygen consumption after 96 h was around 20 μg·g‒1 dry mass in soil or soil/drilling water-based mud mixture. Soil mixes contained 10 wt% synthetic base, mud had a higher oxygen consumption – 38 μg · g‒1 dry mass. Oxygen consumption decreases sharply as the content of the spent synthetic base mud fraction increases. A higher concentration of spent SBM (35 wt%) reduced the aerobic metabolism by slightly more than 50%. A high concentration of reduced carbon decreased the respiratory quotient (RQ) value to 0.7. All the researched drilling waste shows microbiological activity. At the full concentration of drilling fluids and non-dilution options, the chemical composition (salinity, inhibitors, etc.) strongly inhibits microbiota development and consequently, respiration
Samples for the study were collected from, known from the literature, outcrop profiles in Zarzecze, Radymno, Dybawka, Tarnawce and Pikulice-Nehrybka, situated at the Carpathian border, in the vicinity of the Przemyśl town, close to the San River valley (SE Poland). They represent the Vistulian loess-palaeosol sequences. Carbonates occur mainly in the loesses representing OIS 2 and 3. Pollen analysis, carried out for two profiles (Tarnawce, Radymno), throws light on palaeoecological conditions of loess cover formation and transformation.Isotopic analysis of authigenic carbonates was carried out on carbonate cemented bodies dispersed throughout the loess in forms of nodule, rhizolith and rhizocretion and on bioclasts, mainly snail shells, ostracod valves, and sparse globules (probably the internal shells of the naked snails).In the successions studied, the upper Vistulian loess deposited in environment with poor vegetation, contains rhizo- liths and rhizocretions mainly, while in the middle and lower Vistulian loess with well developed soils, gley horizons, and intercalations of subaqueous sediments, remains of snail shells and ostracod valves prevail. The two main forms of carbonates differ markedly in isotopic composition from one another. These differences seem to be more important than those between samples of one form of carbonates along particular sections. That is the result of numerous factors affecting the fractionation of carbon and, in particular, oxygen stable isotopes in the environment of precipitation of authigenic calcite. The isotopic composition of carbonates cementing sediments is controlled mainly by biominerali- zation of organic matter and local climatic parameters which were rather slightly differentiated during the formation of the studied sediments. The d13C values for bioclasts vary in a broader range than for calcitic cements. Usually the snail shell carbonate is more enriched with heavier carbon isotope than that from ostracod valves, resulting from the isotopic equilibrium with precipitation and with surface waters, respectively. Basing on our study we can conclude that fluctuations of isotope composition of authigenic carbonates make it hard to apply as a paleoclimatic indicator. However, the general trend of d18O variation in analysed carbonate fractions from leoss-palaeosol sequences displays some connections with climatic fluctuations.
The organic carbon (OC)-rich, black shale succession of the Middle Triassic Bravaisberget Formation in Spitsbergen contains scattered dolomite-ankerite cement in coarser-grained beds and intervals. This cement shows growth-related compositional trend from non-ferroan dolomite (0–5 mol % FeCO3) through ferroan dolomite (5–10 mol % FeCO3) to ankerite (10–20 mol % FeCO3, up to 1.7 mol % MnCO3) that is manifested by zoned nature of composite carbonate crystals. The d13C (-7.3‰ to -1.8‰ VPDB) and d18O (-9.4‰ to -6.0‰ VPDB) values are typical for burial cements originated from mixed inorganic and organic carbonate sources. The dolomite-ankerite cement formed over a range of diagenetic and burial environments, from early post-sulphidic to early catagenic. It reflects evolution of intraformational, compaction-derived marine fluids that was affected by dissolution of biogenic carbonate, clay mineral and iron oxide transformations, and thermal decomposition of organic carbon (decarboxylation of organic acids, kerogen breakdown). These processes operated during Late Triassic and post-Triassic burial history over a temperature range from approx. 40°C to more than 100°C, and contributed to the final stage of cementation of the primary pore space of siltstone and sandstone beds and intervals in the OC-rich succession.
Tin dioxide (SnO2) is an n-type semiconductor and has useful characteristics of high transmittance, excellent electrical properties, and chemical stability. Accordingly, it is widely used in a variety of fields, such as a gas sensor, photocatalyst, optoelectronics, and solar cell. In this study, SnO2 films are deposited by thermal atomic layer deposition (ALD) at 180°C using Tetrakis(dimethylamino)tin and water. A couple of 5.9, 7.4 and 10.1nm-thick SnO2 films are grown on SiO2/Si substrate and then each film is annealed at 400°C in oxygen atmosphere. Current transport of SnO2 films are analyzed by measuring current – voltage characteristics from room temperature to 150°C. It is concluded that electrical property of SnO2 film is concurrently affected by its semiconducting nature and oxidative adsorption on the surface.
Silver nanoparticles (AgNPs) are widely used in numerous industries and areas of daily life, mainly as antimicrobial agents. The particles size is very important, but still not suffi ciently recognized parameter infl uencing the toxicity of nanosilver. The aim of this study was to investigate the cytotoxic effects of AgNPs with different particle size (~ 10, 40 and 100 nm). The study was conducted on both reproductive and pulmonary cells (CHO-9, 15P-1 and RAW264.7). We tested the effects of AgNPs on cell viability, cell membrane integrity, mitochondrial metabolic activity, lipid peroxidation, total oxidative and antioxidative status of cells and oxidative DNA damage. All kinds of AgNPs showed strong cytotoxic activity at low concentrations (2÷13 μg/ml), and caused an overproduction of reactive oxygen species (ROS) at concentrations lower than cytotoxic ones. The ROS being formed in the cells induced oxidative damage of DNA in alkaline comet assay. The most toxic was AgNPs<10 nm. The results indicate that the silver nanoparticles, especially less than 10 nm, may be harmful to the organisms. Therefore, risk should be considered when using nanosilver preparations and provide appropriate protective measures when they are applied.
The aim of the presented research was to test different carbon supports, such as graphene oxide (GO), graphene oxide modified with ammonia (N-GO), and reduced graphene oxide (rGO) for catalysts used in a low-temperature fuel cell, specifically a proton exchange membrane fuel cell (PEMFC). Modification of the carbon supports should lead to different catalytic activity in the fuel cell. Reduction of GO leads to partial removal of oxygen groups from GO, forming rGO. Modification of GO with ammonia results in an enrichment of GO structure with nitrogen. A thorough analysis of the used supports was carried out, using various analytical techniques, such as FTIR spectroscopy and thermogravimetric (TGA) analysis. Palladium and platinum catalysts deposited on these supports were produced and used for the oxygen reduction reaction (ORR). Catalytic activity tests of the prepared catalysts were carried out in a home-made direct formic acid fuel cell (DFAFC). The tests showed that the enrichment of the GO structure with nitrogen caused an increase in the catalytic activity, especially for the palladium catalyst. However, reduction of GO resulted in catalysts with higher activity and the highest catalytic activity was demonstrated by Pt/rGO, because platinum is the most catalytically active metal for ORR. The obtained results may be significant for low-temperature fuel cell technology, because they show that a simple modification of a carbon support may lead to a significant increase of the catalyst activity. This could be useful especially in lowering the cost of fuel cells, which is an important factor, because thousands of fuel cells running on hydrogen are already in use in commercial vehicles, forklifts, and backup power units worldwide. Another method used for lowering the price of current fuel cells can involve developing new clean and cheap production methods of the fuel, i.e. hydrogen. One of them employs catalytic processes, where carbon materials can be also used as a support and it is necessary to know how they can influence catalytic activity.
Results of the studies for determining fractions of organic contaminants in a pretreated petrochemical wastewater flowing into a pilot Aerated Submerged Fixed-Bed Biofilm Reactor (ASFBBR) are presented and discussed. The method of chemical oxygen demand (COD) fractionation consisted of physical tests and biological assays. It was found that the main part of the total COD in the petrochemical, pretreated wastewater was soluble organic substance with average value of 57.6%. The fractions of particulate and colloidal organic matter were found to be 31.8% and 10.6%, respectively. About 40% of COD in the influent was determined as readily biodegradable COD. The inert fraction of the soluble organic matter in the petrochemical wastewater constituted about 60% of the influent colloidal and soluble COD. Determination of degree of hydrolysis (DH) of the colloidal fraction of COD was also included in the paper. The estimated value of DH was about 62%. Values of the assayed COD fractions were compared with the same parameters obtained for municipal wastewater by other authors.
Oxygen is an element that is first purposely brought into the steel melt to remove some unwanted elements or to reduce their concentration
(oxidation). In the made cast steel there is on the contrary necessary to reduce the oxygen content with the use of deoxidation to such a
level in order to avoid a reaction with carbon with the formation of CO bubbles. Concentration of oxygen in steel before casting is given,
in particular, by the manner of metallurgical processing and the used deoxidation process. Oxygen is found in molten steels both as
chemically bound in the form of oxides and in the form of oxygen dissolved in the solution – the melt. Chemical composition
of the melt strongly influences the activity of oxygen dissolved in the melt and further on the composition of oxidic inclusions forming in
the melt during the reaction with oxygen. In the Fe-C-Cr-Ni based alloys in the reaction with oxygen greatly participates also chrome,
whose products are often in solid state and they are the cause of forming such defects as e.g. oxidic films.