Water Oxygen Diffusion Research Articles

Innovative passive aeration process for synthetic deoxygenated water

ABSTRACT Aeration is a process of diffusing oxygen into water in order to stimulate the aerobic bacteria for starting wastewater aerobic treatment process. Zero energy aeration systems that do not require electric or mechanical power are known as passive aerators. A new technology for passive aerators using inverted bell siphon principle is innovated, which requires a lot less volume for its installation compared to other passive aeration systems as cascade, spray and perforated tray aerators. A laboratory experimental program investigated the inverted bell siphon system using deoxygenated water with almost zero dissolved oxygen concentration like anaerobic treatment effluent. The system is used to build water pressure through a distribution system used for scattering water in air to diffuse oxygen into it. Holed arm pipe with different hole diameters and numbers, showerhead, fire sprinkler and modified fire sprinkler were tested as distributors to reach the optimum type which verify good oxygen diffusion in water and ensure least possibility of clogging of distributors. Dissolved oxygen concentration was measured for each distributor water effluent. The experiments showed that the modified fire sprinkler achieved higher oxygen diffusion in water and best distribution, in addition to its geometry that prevents the distribution system from clogging.

Enhanced Mass Transfer of Oxygen through a Gas–Liquid–Solid Interface for Photocatalytic Hydrogen Peroxide Production

AbstractSolar‐driven photocatalytic oxygen reduction is a potentially sustainable route for the production of hydrogen peroxide (H2O2). However, this approach suffers from the limited solubility and slow diffusion of oxygen in water. Another problem is that most photocatalytic oxygen reduction systems do not work well with just water. They often require the addition of sacrificial agents such as alcohols. Here, a covalent organic framework (COF)‐based photocatalyst that can reduce O2 to H2O2 efficiently in pure water under visible‐light irradiation is reported. A solar‐to‐chemical conversion of 0.76% is achieved for H2O2 generation. More importantly, the hydrophobic and mesoporous properties of triphenylbenzene‐dimethoxyterephthaldehyde‐COF allow the formation of a triphase interface (gas–liquid–solid) when loading this catalyst onto a porous substrate. The H2O2 production rate reaches ≈2.9 mmol gcat−1 h−1 at the triphase interface by overcoming the mass‐transfer limitation of O2 in water. Notably, this rate is 15 times higher than that in a diphase system (liquid–solid). The photoelectrochemical tests reveal that the increase in yield is closely related to the enhanced mass‐transfer rate and the higher interfacial O2 concentration. Furthermore, the triphenylbenzene part is identified as the reactive site based on theoretical calculations.

Insights into soybean transcriptome reconfiguration under hypoxic stress: Functional, regulatory, structural, and compositional characterization.

Soybean (Glycine max) is one of the major crops worldwide and flooding stress affects the production and expansion of cultivated areas. Oxygen is essential for mitochondrial aerobic respiration to supply the energy demand of plant cells. Because oxygen diffusion in water is 10,000 times lower than in air, partial (hypoxic) or total (anoxic) oxygen deficiency is important component of flooding. Even when oxygen is externally available, oxygen deficiency frequently occurs in bulky, dense or metabolically active tissues such as phloem, meristems, seeds, and fruits. In this study, we analyzed conserved and divergent root transcriptional responses between flood-tolerant Embrapa 45 and flood-sensitive BR 4 soybean cultivars under hypoxic stress conditions with RNA-seq. To understand how soybean genes evolve and respond to hypoxia, stable and differentially expressed genes were characterized structurally and compositionally comparing its mechanistic relationship. Between cultivars, Embrapa 45 showed less up- and more down-regulated genes, and stronger induction of phosphoglucomutase (Glyma05g34790), unknown protein related to N-terminal protein myristoylation (Glyma06g03430), protein suppressor of phyA-105 (Glyma06g37080), and fibrillin (Glyma10g32620). RNA-seq and qRT-PCR analysis of non-symbiotic hemoglobin (Glyma11g12980) indicated divergence in gene structure between cultivars. Transcriptional changes for genes in amino acids and derivative metabolic process suggest involvement of amino acids metabolism in tRNA modifications, translation accuracy/efficiency, and endoplasmic reticulum stress in both cultivars under hypoxia. Gene groups differed in promoter TATA box, ABREs (ABA-responsive elements), and CRT/DREs (C-repeat/dehydration-responsive elements) frequency. Gene groups also differed in structure, composition, and codon usage, indicating biological significances. Additional data suggests that cis-acting ABRE elements can mediate gene expression independent of ABA in soybean roots under hypoxia.

Comparative Proteomic Analysis Provides Insight into the Key Proteins Involved in Cucumber (Cucumis sativus L.) Adventitious Root Emergence under Waterlogging Stress.

Waterlogging is a common abiotic stress in both natural and agricultural systems, and it primarily affects plant growth by the slow oxygen diffusion in water. To sustain root function in the hypoxic environment, a key adaptation for waterlogging tolerant plants is the formation of adventitious roots (ARs). We found that cucumber waterlogging tolerant line Zaoer-N seedlings adapt to waterlogging stress by developing a larger number of ARs in hypocotyls, while almost no AR is generated in sensitive line Pepino. To understand the molecular mechanisms underlying AR emergence, the iTRAQ-based quantitative proteomics approach was employed to map the proteomes of hypocotyls cells of the Zaoer-N and Pepino under control and waterlogging conditions. A total of 5508 proteins were identified and 146 were differentially regulated proteins (DRPs), of which 47 and 56 DRPs were specific to tolerant and sensitive line, respectively. In the waterlogged Zaoer-N hypocotyls, DRPs related to alcohol dehydrogenases (ADH), 1-aminocyclopropane-1-carboxylicacid oxidases, peroxidases, 60S ribosomal proteins, GSDL esterases/lipases, histone deacetylases, and histone H5 and were strongly overrepresented to manage the energy crisis, promote ethylene release, minimize oxidative damage, mobilize storage lipids, and stimulate cell division, differentiation and growth. The evaluations of ethylene production, ADH activity, pyruvate decarboxylase (PDC) activity and ethanol production were in good agreement with the proteomic results. qRT-PCR analysis of the corresponding 146 genes further confirmed the accuracy of the observed protein abundance. These findings shed light on the mechanisms underlying waterlogging triggered cucumber ARs emergence, and provided valuable information for the breeding of cucumber with enhanced tolerance to waterlogging.

Mitochondrial Respiratory Function Induces Endogenous Hypoxia

Hypoxia influences many key biological functions. In cancer, it is generally believed that hypoxic condition is generated deep inside the tumor because of the lack of oxygen supply. However, consumption of oxygen by cancer should be one of the key means of regulating oxygen concentration to induce hypoxia but has not been well studied. Here, we provide direct evidence of the mitochondrial role in the induction of intracellular hypoxia. We used Acetylacetonatobis [2-(2′-benzothienyl) pyridinato-kN, kC3’] iridium (III) (BTP), a novel oxygen sensor, to detect intracellular hypoxia in living cells via microscopy. The well-differentiated cancer cell lines, LNCaP and MCF-7, showed intracellular hypoxia without exogenous hypoxia in an open environment. This may be caused by high oxygen consumption, low oxygen diffusion in water, and low oxygen incorporation to the cells. In contrast, the poorly-differentiated cancer cell lines: PC-3 and MDAMB231 exhibited intracellular normoxia by low oxygen consumption. The specific complex I inhibitor, rotenone, and the reduction of mitochondrial DNA (mtDNA) content reduced intracellular hypoxia, indicating that intracellular oxygen concentration is regulated by the consumption of oxygen by mitochondria. HIF-1α was activated in endogenously hypoxic LNCaP and the activation was dependent on mitochondrial respiratory function. Intracellular hypoxic status is regulated by glucose by parabolic dose response. The low concentration of glucose (0.045 mg/ml) induced strongest intracellular hypoxia possibly because of the Crabtree effect. Addition of FCS to the media induced intracellular hypoxia in LNCaP, and this effect was partially mimicked by an androgen analog, R1881, and inhibited by the anti-androgen, flutamide. These results indicate that mitochondrial respiratory function determines intracellular hypoxic status and may regulate oxygen-dependent biological functions.

Dissolution and Diffusion of Oxygen in Deaerated Water and Escape of Oxygen to the Atmosphere from an Oxygen Saturated Aqueous Solution: An Investigation by a Pulse Radiolysis Technique

Fast reaction of hydrated electrons (eaq−) with oxygen has been used to determine the dissolution and diffusion of oxygen in water by monitoring the decay of eaq− at 700 nm. Hydrated electrons in t...

Turbulence-Driven Metal Release from Resuspended Pyrrhotite Tailings

The use of shallow water covers (up to 2 m) to flood reactive sulfide mine tailings is a common method of reducing the environmental impact of mining. It relies on the low solubility and diffusivity of oxygen in water. In actual tailings ponds, however, wind-induced waves and turbulent mixing can lead to tailings resuspension and increased oxygen transfer. Laboratory experiments and numerical modeling were performed to examine the impact of resuspension on metal release from sulfide mine tailings, and to elucidate the nature of the flow field. The results indicated that resuspended tailings oxidized and released acidity and metals considerably more than tailings at rest. The oxidation and metal release rates increased with an increase in the degree of turbulence-induced mixing in the water cover. Computed wall shear stresses on the surface of the tailings ranged from 0.14 to 0.42 N/m², which were close to, but slightly above, the critical shear stresses of the tailings (0.12–0.17 N/m²). The flow energy was found to be positively correlated to the cumulative release of metals (zinc, nickel, copper, and ferric iron) and sulfate.

Consequences of splenectomy on the compensatory mechanism of cutaneous respiration in the newt

AbstractThe spleen of the newt Triturus cristatus carnifex (Laurenti) hoards erythrocytes when the animal is well oxygenated and releases these into circulation when the animal becomes hypoxic. This mechanism allows the newts, amphibians with prevalently cutaneous respiration, to adapt to both environmental and metabolic changes.Splenectomized specimens were anesthetized with chlorbutol (to eliminate movement and lung respiration) and observed in five different conditions: at 18°C in humid air, stirred water, and still water, and at 6°C and 33°C in humid air. The study demonstrates that the newt does not have substitute sites for erythrocyte accumulation. However, though the spleenless specimens are incapable of controlling their cutaneous oxygen supply, they can regulate their blood volume, which diminishes with decreasing temperature causing marked variations in the erythrocyte concentration and hematocrit value.The splenectomized specimens, raised for over a year at 18°C, present typically steatosic livers, with lipid droplets and extremely low hepatocyte glycogen levels, indicating a state of chronic hypoxia due to the prevalently aquatic habits of the newt. In fact, the spleenless newts have significantly fewer erythrocytes (P < 0.001) than the unoperated animals‐‐a total volume of 2.27 ± 0.46 ml per 100 g of body weight compared to 2.74 ± 0.29 (mean ± standard deviation). The limited quantity of erythrocytes can provide adequate oxygen only at low temperatures and in an airy environment or in moving water, while an immobile animal in still water undergoes hypoxia due to the formation around it of an hypoxic =diffusion boundary layer= caused by the low coefficient of oxygen diffusion in water. © 1993 Wiley‐Liss, Inc.

Hematological changes in the newt during the process of splenic decongestion in reply to hypoxia

Abstract Specimens of the newt, Triturus cristatus carnifex (Laurenti), anesthetized with chlorobutanol and exposed to humid air at 6° C for 300 min, accumulate about 50 of their red blood cells (RBC) in the spleen. When the newts are transferred to still water at 18° C, the spleen releases the RBC back into circulation, emptying itself out completely. This process counteracts the hypoxia caused by both the increase in temperature and low coefficient of oxygen diffusion in water. The analysis of the RBC counts, hematocrit value and percentage volumes of the spleen, blood and plasma (the last measured colorimetrically after injecting 0.05 ml of Evans blue in the conus arteriosus) in groups of newts sampled at various periods during the spleen decongestion reveals the trend of the compensatory process. The emptying out of the spleen takes less than an hour, causing significant increases in the RBC concentration after 15 and 30 min of immersion; the counts then undergo an inflexion which becomes significant ...

Diffusion of oxygen in water and hydrocarbons using an electron spin resonance spin-label technique

The Smoluchowski equation for the bimolecular collision rate of dissolved oxygen molecules with spin labels yielded values for the diffusion constant of oxygen in water that are in agreement with the Stokes-Einstein equation (D infinity T/eta, where eta is the macroscopic viscosity) and with published values obtained by conventional methods. Heisenberg exchange at an interaction distance of 4.5 A occurs with a probability close to one for each encounter. In mixed hydrocarbons (olive oil, paraffin oils) and sec-butyl benzene, D infinity (T/eta)rho, where rho lies between 0.5 and 1. Oxygen diffuses in the hydrocarbons between 10 and 100 times more rapidly than predicted from the macroscopic viscosity. Similar results would be expected for diffusion of oxygen in model and biological membranes. Parallel measurements of rotational diffusion of the spin labels show little correlation with measurements of translational diffusion of oxygen. Dipolar interactions between spin labels and oxygen appear negligible except in the limit of highest viscosities.

Diffusivity of oxygen in water

Diffusivity of oxygen in water

THE DIFFUSION OF OXYGEN IN WATER.

THE DIFFUSION OF OXYGEN IN WATER.