Oxygen Diffusion in the Soil‐Plant System V. Oxygen Concentration and Temperature Effects on Oxygen Relations Predicted for Maize Roots 1

1972 ◽  
Vol 64 (6) ◽  
pp. 720-725 ◽  
Author(s):  
R. J. Luxmoore ◽  
L. H. Stolzy
Keyword(s):  
Oxygen Concentration ◽  
Oxygen Diffusion ◽  
Temperature Effects ◽  
Plant System ◽  
Maize Roots

Modelling oxygen transport in soil with plant root and microbial oxygen consumption: depth of oxygen penetration

Soil Research ◽  
2013 ◽  
Vol 51 (6) ◽  
pp. 539 ◽  
Author(s):  
F. J. Cook ◽  
J. H. Knight ◽  
F. M. Kelliher
Keyword(s):  
Diffusion Coefficient ◽  
Redox Potential ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Oxygen Concentration ◽  
Oxygen Diffusion ◽  
Plant Root ◽  
Critical Value ◽  
Critical Values

A set of equations governing oxygen diffusion and consumption in soils has been developed to include microbial and plant-root sinks. The dependent variable is the transformed oxygen concentration, which is the difference between the gaseous concentration and a scaled value of the aqueous oxygen concentration at the root–soil interface. The results show how, as the air-filled porosity decreases, the reduced oxygen flux causes the depth of extinction to decrease. The results also show how the depth of extinction at a particular value of soil water content decreases with increasing temperature, due to increased microbial respiration. The critical value of water content at which the oxygen concentration goes to extinction at a finite depth was compared with alternative calculations with only a microbial sink. By ignoring the feedback of oxygen concentration on root uptake, the alternative calculations yielded substantially higher critical values of water content at all temperatures. Two soil oxygen diffusion coefficient functions from the literature were compared and shown to give significantly different critical values of water content for fine-textured soils, one more realistic than the other. A single relationship between the extinction depth and the ratio of the water content to the critical value was shown to apply for all temperatures and soil textures. The oxygen profiles were used along with a function relating redox potential to oxygen concentration to generate redox potential profiles. This application of the model could be useful in explaining soil biochemical processes in soils. For one such process, denitrification, the depth at which a critical oxygen concentration is reached was calculated as a function of the air-filled porosity and temperature of the soil. The implications of the critical value of soil water content in terms of water-filled pore space and matric potential are discussed in relation to the diffusion coefficient functions and recent literature.

scholarly journals Effect of Dislocation Slip Mechanism under the Control of Oxygen Concentration in Alpha-Case on Strength and Ductility of TC4 Alloy

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1057
Author(s):  
Xin Feng ◽  
Yilong Liang ◽  
Hao Sun ◽  
Shu Wang
Keyword(s):  
Electron Microscopy ◽  
Oxygen Concentration ◽  
Oxygen Diffusion ◽  
Negative Impact ◽  
Dislocation Slip ◽  
Slip Mechanism ◽  
Alpha Case ◽  
Lower Oxygen ◽  
Tc4 Alloy ◽  
Strength And Ductility

The oxygen diffusion layer (alpha-case) is generally considered to have a negative impact on the mechanical properties and applications of titanium alloys. In this study, TC4 alloy specimens with four types of different oxygen concentrations in alpha-case were obtained by controlling the oxygen diffusion process parameters. Scanning electron microscopy and glow discharge spectrometry were employed to characterize the microstructure and oxygen concentration of alpha-case. The effect of alpha-case on strength and ductility of TC4 alloy was investigated via tensile test and new insights were provided. The results indicate that with the increase in the oxygen concentration in the alpha-case, the ductility of the TC4 alloy gradually decreased. Interestingly, the strength of TC4 alloy with the alpha-case first increased and then decreased, resulting in the existence of a peak corresponding to a lower oxygen concentration before the decline of strength. Furthermore, a relatively good ductility match was also observed at the peak. When the oxygen concentration was relatively high, both the strength and ductility decreased. This phenomenon is attributed to the fact that dislocations in the alpha-case controlled by the oxygen concentration were modified from wavy slip to planar slip. Finally, the dislocation’s slip morphology was characterized by transmission electron microscopy.

Microsensor measurement of oxygen concentration in biofilms: from one dimension to three dimensions

2004 ◽  
Vol 49 (11-12) ◽  
pp. 353-358 ◽  
Author(s):  
T. Yu ◽  
C. de la Rosa ◽  
R. Lu
Keyword(s):  
Oxygen Concentration ◽  
Oxygen Diffusion ◽  
Three Dimensional ◽  
Domestic Wastewater ◽  
Three Dimensions ◽  
Base Layer ◽  
One Dimension ◽  
Oxygen Distribution ◽  
Dimensional Measurements ◽  
Degree Of Heterogeneity

In this study, we measured oxygen concentration in biofilms in one dimension in field conditions and in three dimensions in laboratory conditions by using a robust oxygen microsensor in combination with an automation and data acquisition system. The biofilms were on the discs of rotating biological contactors treating domestic wastewater. The results of this study provide experimental evidence on oxygen distribution in wastewater biofilms and on biofilm structure. (1) The three dimensional measurements of oxygen concentration in biofilms revealed “pockets” of oxygen in deep sections of biofilms. In these isolated "pockets," located 600-760 mm from the biofilm surface, dissolved oxygen concentration was as high as 1 mg/L. This depth of oxygen diffusion is deeper than what was determined based on one dimensional measurements. (2) The heterogeneity of oxygen distribution was related to the surface structure of biofilms. The structure of the biofilm surface affected the diffusion boundary layer over the surface and, in turn, the oxygen diffusion and distribution inside biofilms. (3) Oxygen concentration in biofilms changed generally from a high degree of heterogeneity near the biofilm surface to a low degree of heterogeneity in deep sections of biofilms, indicating a cell-clusters-like structure near the surface and a more compact base layer close to the substratum.

scholarly journals NUMERICAL SOLUTION OF THE DIFFUSION EQUATION FOR OXYGEN DIFFUSION IN SOIL

2016 ◽  
Vol 7 (1) ◽  
Author(s):  
Aco Janićijević ◽  
Svetislav Savović ◽  
Alexandar Djordjevich
Keyword(s):  
Finite Difference ◽  
Finite Difference Method ◽  
Diffusion Equation ◽  
Oxygen Concentration ◽  
Difference Method ◽  
Oxygen Diffusion ◽  
Explicit Finite Difference ◽  
Periodical Change ◽  
Explicit Finite Difference Method ◽  
Oxygen Concentrations

By solving the diffusion equation using the explicit finite difference method, oxygen concentrations inside the soil are determined for various periods of time. Two different cases are investigated, with constant and daily changing air oxygen concentrations. It was concluded that the influence of the periodical change of the air oxygen concentration on the oxygen concentration in the soil was more pronounced for smaller diffusion times at smaller lengths of the soil profile.

Effect of Grain Size on Oxidation Resistance of Unalloyed Titanium

2016 ◽  
Vol 879 ◽  
pp. 2187-2191 ◽  
Author(s):  
Y. Yang ◽  
Tomonrori Kitashima ◽  
T. Hara ◽  
Y. Hara ◽  
Yoko Yamabe-Mitarai ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Oxidation Resistance ◽  
Oxygen Concentration ◽  
Oxygen Diffusion ◽  
High Temperature Oxidation ◽  
Boundary Diffusion ◽  
Temperature Oxidation ◽  
Grain Sizes ◽  
Simulation Results

The effect of the grain size on the high-temperature oxidation resistance of unalloyed titanium was experimentally investigated using titanium samples with two different grain sizes of 219 μm and 118 μm. The weight gain during oxidation and the penetration depth of oxygen from a metal surface were larger in the small-grain-size sample compared with the large-grain-size sample. In addition, oxygen diffusion was faster in the substrate of the small-grain-size sample. These results were attributed to the grain-boundary diffusion of oxygen. A steep change in the oxygen concentration was observed at a grain boundary. Our simulation results suggested that slower oxygen diffusion into the inner grain from the surface through the grain boundary with high diffusivity can cause the observed steep change in the oxygen concentration.

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