A STUDY OF SOME CONDITIONS INFLUENCING THE RATE OF EXCHANGE OF OXYGEN IN BLOOD IN VITRO

Remediation of PCE-contaminated aquifer by an in situ two-layer biobarrier: laboratory batch and column studies

Ceria-zirconia (Ce-Zr) solid solution is widely used as an oxygen storage material, which is a key component in the automotive three-way catalysts. The Ce-Zr solid solution is usually used with noble metals supported on their surface. Thus the evaluation of oxygen storage capacity (OSC) should be conducted on the Ce-Zr solid solution loaded with a noble metal. The measured OSC of noble-metal-loaded Ce-Zr solid solution consists of two parts; one is the stored oxygen within the solid solution itself, and the other is the adsorbed oxygen on the surface of the supported noble metal particles. Therefore, it is necessary to clarify the influence of the noble metal on the measured OSC, and this will also help to ascertain the exact OSC of the solid solution itself. In this research, the authors tried to clarify the above issues by characterizing the OSC performance on Ce-Zr solid solutions with Pt loading from 0.0001 to 10 wt%. We found that, increasing the Pt loading makes the oxygen storage and release rate higher. Temperature increase also makes the oxygen storage rate higher, however, the oxygen release rate is not affected by the temperature. The apparent OSC saturated above a certain level of Pt loading and temperature. The saturated OSC increased with increasing temperature.

The kinetics of oxygen uptake and release by human, salamander (Amphiuma means), and artificially constructed red cells were measured under a variety of physiological conditions using stopped-flow, rapid mixing techniques. The results were analyzed quantitatively using the generalized, three-dimensional disc model that was developed in two previous publications (Vandegriff, K. D., and Olson, J. S. (1984) Biophys. J. 45, 825-835 and Vandegriff, K. D., and Olson, J. S. (1984) J. Biol. Chem. 259, 12609-12618). The apparent rate of gas exchange is governed primarily by the oxygen flux at the red cell surface. In the case of uptake, this flux is roughly independent of intracellular chemical reaction parameters and inversely proportional to the thickness of the unstirred solvent layer which is adjacent to the red cell surface. For release experiments in the presence of high concentrations of sodium dithionite, the flux at the cell surface is inversely proportional to the oxygen affinity of the intracellular hemoglobin and roughly independent of the thickness of the external unstirred solvent layer. As a result, the effects of cell size, internal heme concentration, and pH are expressed differently in the two types of kinetic experiments. The rate of oxygen uptake depends on roughly the second power of the surface area to volume ratio of the erythrocyte, whereas the rate of release is much less dependent on the size and shape of the red cell. The half-time of oxygen uptake is directly proportional to intracellular heme concentration for cells of equivalent geometries; the half-time of oxygen release is linearly dependent on internal heme concentration but, at low heme concentrations, is determined primarily by the rate of oxygen dissociation from hemoglobin. The rate of cellular oxygenation is roughly independent of pH and internal 2,3-diphosphoglycerate concentration; in contrast, the rate of deoxygenation depends markedly on these conditions. As the pH is lowered or the internal diphosphoglycerate concentration is raised, the overall oxygen affinity of the cell suspension decreases severalfold, and the rate of oxygen release increases by roughly the same extent.

The annual regimes of estimated rates of oxygen and carbon dioxide exchange between water surface and the atmosphere was compared for two water bodies with different sizes and hydroecological conditions: the deep oligotrophic Lake Baikal and the small mesotrophic–eutrophic Mozhaisk Reservoir with water exchange rate 150 times greater than that of Baikal. The obtained, very large, differences between the rates of gas evasions and invasions in the lake and the reservoir allow the rates of these processes to be used as integral characteristics for the parameterization of the self-purification capacity of freshwater bodies from organic pollutants.

As an important oxygen storage material, ceria-zirconia solid solution is widely used in automotive three-way catalysts. For the Ce-Zr solid solution being usually used with a noble metal, the evaluation of oxygen storage capacity (OSC) should be conducted with the Ce-Zr solid solution loaded with a noble metal. The measured OSC of noble-metal-loaded Ce-Zr solid solution consists of two parts: the stored oxygen within the solid solution itself and the adsorbed oxygen on the loaded noble metal particles. Therefore, it is very necessary to clarify the influence of metal loading on the measured OSC in order to ascertain the exact OSC of the solid solution itself. In this research, the authors attempted to clarify the above issues by characterizing the OSC performance of Ce-Zr solid solutions with platinum (Pt) loading from 0.0001-10 mass%. We found that increasing the amount of Pt loading increases the oxygen storage and release rates and that increasing the temperature also increases the oxygen storage rate, although the oxygen release rate is not affected by increasing the temperature. The apparent OSC reached saturation over a certain amount of Pt loading and temperature. The saturated OSC increased with increasing temperature.

There is general agreement today that intracellular diffusive transport of HbO2 and O2 limits the rate of oxygen uptake or release by the blood in the exchange vessels. Recent hemorheological results have shown that the mammalian erythrocyte exhibits fluidity as its most unique rheological property: it can be deformed continuously and rapidly, shear and normal stresses can be transmitted to the interior of the cell where systems of laminar flow are induced. These mechanical properties lead to the question whether or not intracellular convection does take place in the erythrocyte and to what extent it plays a part in gas exchange. A method was developed which subjects oxygen-saturated solutions and cell suspensions to an artificial but well defined flow (cone-plate-viscosimeter), and allows simulataneous determination of the initial O2 release indices under standardized conditions (O2 saturation, temperature, time, diffusion area, and difference of O2 partial pressure). The results strongly suggest that intracellular flow resulting from the physiological erythrocyte deformation in flow can supplement the O2 release from intact cells through a convective transport of HbO2 and O2 molecules. The example of osmotic shrinking shows that red cell fluidity is not only a precondition for normal flow in the microcirculation, but also for the normal gas exchange of the cells.

The absorption capacity of oily sludge pyrolysis residue was utilized to prepare oxygen-releasing composites for groundwater remediation. The physical properties of the oily sludge pyrolysis residue were specific surface area of 13.936 m2/g and main pore size on the order of nanometers. The pyrolysis residue was nontoxic and would not cause secondary contamination of groundwater. The rate of mass loss of calcium peroxide and the oxygen release rate in water were analyzed. An oxygen-releasing composite containing 35% calcium peroxide, 15% oily sludge pyrolysis residue, 30% fluviatile sand, 10% calcium-based bentonite soil, and 10% deionized water was proposed. Addition of oily sludge to the composite plugged some of the oxygen-releasing surface and slowed the rate of oxygen release. Continuous precipitation of CaCO3 on the surface and in the pores of the composite also reduced the initial oxygen release rate and slowed the overall oxygen release rate.

Rates of oxygen production and inorganic carbon uptake by a mixed culture of phytoplankton were determined in a highly variable light regime. Scatter diagrams of the results revealed a smoothly varying relationship between irradiance and photosynthetic oxygen release except when the rate of oxygen release was depressed by CO2 depletion. There was no indication that the instantaneous rate of oxygen production depended on light intensities received in the recent (5–30 min) past. However, the net rate of inorganic carbon uptake exhibited large, transient fluctuations in response to rapid changes in light as CO2 became depleted (<0.001 mg·liter−1). Spectral analysis showed that the transient fluctuations in inorganic carbon exchange were related to the rate of change in irradiance. Enhanced transport of inorganic carbon into the cells at high pH may account for the highest rates of carbon uptake; diffusional loss of intracellular CO2, photorespiration, or both may account for the highest rates of carbon release. Models derived from incubations at constant light intensities cannot account for the observed fluctuations in inorganic carbon uptake, indicating the importance of light variability, especially in systems that become depleted of CO2.

Effects of light intensity and water temperature on oxygen release from roots into water lettuce rhizosphere

The chemical-looping combustion (CLC) and chemical-looping with oxygen uncoupling (CLOU) processes are novel solutions for efficient combustion with inherent separation of carbon dioxide. These processes use a metal oxide as an oxygen carrier to transfer oxygen from an air reactor to a fuel reactor, where the fuel reacts with the solid oxygen carrier. When solid fuel is used in CLC, the char must be gasified by, e.g., steam to form H2 and CO, that can be subsequently oxidized to H2O and CO2 by the oxygen carrier. In the case of CLOU, the oxygen carrier releases oxygen gas in the fuel reactor. This enables a high rate of conversion of char from solid fuels, because it eliminates the need for the gasification step needed in normal CLC with solid fuels. In this work, the rate of oxygen release and oxidation of an oxygen carrier consisting of CuO supported by MgAl2O4 (40/60 wt %) for the CLOU process is investigated. The oxygen carrier was produced by freeze-granulation, calcined at 950 °C, and sieved to a size range of 125–180 μm. The reaction rates were obtained in a laboratory-scale fluidized-bed reactor in the temperature range of 850–900 °C, under alternating reducing and oxidizing conditions. The rate of oxygen release was obtained using devolatilized wood char as the fuel in N2 fluidization. Care was taken to obtain reliable measurements not affected by the availability of the fuel and temperature increase in the bed during combustion of the fuel with the released oxygen from the carrier. The Avrami–Erofeev mechanism was used to model the rates of oxygen release and the values of ko and Eapp were estimated to be 2.5 × 105 s–1 and 139.3 kJ mol–1, respectively. The rates of Cu2O oxidation were investigated in a flow of 5% O2 at the inlet of the reactor. However, it was observed that the oxidation rate is limited by the oxygen supply, indicating rapid conversion of the oxygen carrier. From the obtained reaction rates, the minimum total amount of the investigated oxygen carrier needed in the air and the fuel reactor is estimated to be between 69–139 kg MWth–1.

Oxygen is known to be released from plant roots, but has seldom been quantified for wetland plants. Our study aims to quantify oxygen release from the roots of one wetland species in China, and use this knowledge as a basis for future modeling. We measured diurnal fluctuations in oxygen release from the roots of Acorus calamus Linn in a modeled constructed wetland (CW) using a titanium () citrate buffer. Oxygen release was monitored every two hours. Maximum oxygen release was recorded in the range of 215.2–750.8 μmolg−1h−1 and occurred around 15:00. The maximum value of photosynthetically active radiation (PAR) was in the range of 1281.8–1712.0 mmolm−2s−1 and occurred around 13:00. Both the oxygen release rate and PAR were found to approach zero at night. Our results indicate that oxygen release depends largely on light intensity and exhibits a diurnal periodicity with release occurring only during daytime. Rate of root oxygen release varied during the daytime and this temporal variation was well described by the Gaussian function. While further validation is needed, we suggest that the Gaussian function may be used as the basis for modeling root oxygen release in natural and constructed wetlands.

Sulfur tolerance and rate of oxygen release of combined Mn–Si oxygen carriers for chemical-looping with oxygen uncoupling (CLOU) is investigated. The oxygen carriers were produced by spray-drying and calcined at 1150 °C. The resistance toward sulfur and the rates of oxygen release were evaluated in a laboratory-scale fluidized-bed reactor. It was found that the combined Mn–Si oxygen carrier is tolerant to SO2, at least up to a partial pressure of 5000 vppm. The rates of oxygen release were determined in the temperature range of 975 to 1100 °C using devolatilized wood char as fuel while fluidizing with N2, to maintain a low oxygen partial pressure surrounding the particles. The Arrhenius parameters ko and Eapp for the release of oxygen were estimated for the investigated materials assuming a zero-order reaction with respect to oxygen. The rates of oxygen release were relatively high, particularly at above 1050 °C. From the obtained reaction rates, the solids inventory required for combustion of coal was determined to be as low as 40 kg/MWth in the fuel reactor at 1100 °C. The results indicated that combined Mn–Si oxygen carriers could be interesting materials for the CLOU process by virtue of their resistance to sulfur deactivation and high rate of oxygen release.

Flow nets are one of the effective tools for illustrating groundwater flow rate and direction. Flow nets of a thermal groundwater system under different reference temperatures are examined in this paper. A 3D mathematical model describing water flow and heat transport is established. The stream function and the equivalent hydraulic head are used to describe the flow field in terms of mass flux. The partial differential governing equations are given by the mass conservation equation of the fluid phase and by the advection–diffusion transport equations of heat. They are solved with the standard Galerkin finite element method. Influence of variation in temperature on thermal groundwater flow nets is illustrated with a simplified 2D vertical steady-state mathematical model. The results show that the equipotential lines are not always orthogonal to the streamlines in a geothermal system of a confined aquifer when the heat flow from below is present and when the temperature increases, the equipotential lines are clearly curved and the skew intersection angles between the streamlines and the equipotential lines decrease. For the node of coordinate of (5000, 0) in the aquifer, when the temperature difference between the top boundary and the bottom boundary is 4 and 10 °C, the skew intersection angle is 85.54° and 78.73°, respectively. When the hydraulic gradients are low, the equipotential lines are clearly curved. However, when the hydraulic gradients are high, the bending of the equipotential lines is not obvious. When the hydraulic gradient increases, the skew intersection angles change relatively little. For the same node when the hydraulic head of the left boundary is 600, 700, 800 and 1,000 m, the skew intersection angle is 78.73°, 84.3°, 86.19° and 87.71°, respectively. When the reference temperature increases, the hydraulic heads and the skew intersection angles increase.

Laboratory-scale investigations using individual T.latifolia and J. effusus plants in hydroponic systems were carried out to evaluate the potentials and differences in the species regarding the release of oxygen into their rhizospheres. Their oxygen release intensities were found to vary between the species and also to depend on the redox state of the rhizosphere. The highest release rates with mean values of 1.1 mg/h plant for T.latifolia and 0.5 mg/h plant for J.effusus were estimated at Eh - - 200 mV for both species. The amounts of oxygen released were sufficient to be of biotechnological relevance for oxidative processes in constructed wetlands. The plants even released oxygen under oxidized rhizospheric conditions and for individual plants, an intensification of the oxygen release was estimated, forming further local release maxima at Eh = 250-400 mV with about 0.2 mg/h plant. The total size of the root system does not significantly affect the intensity of oxygen release; instead, the oxygen release state was governed by the size of the above-ground biomass. The intensification of illumination causes an increase in the oxygen release rates, which is pronounced for T.latifolia but small for J.effusus. Further investigations involving other wetland species and using laboratory-scale, pilot-scale and full-scale wetland systems to evaluate oxygen release are of biotechnological interest.

Oxygen release from manganese ores relevant for chemical looping with oxygen uncoupling conditions