Depletion of oxygen

OXYGEN DEFICIENCY Depletion of oxygen content in an atmosphere to below the normal 21%. Exposure to <18% must not be permitted. Concentrations 6% to 10% oxygen can lead to loss of consciousness. 

High concentration of metal ions and depletion of oxygen... 

Although this chemistry is complex, the basic process is reduction of iron oxide by carbon in an atmosphere depleted of oxygen. Archaeologists have found ancient smelters in Africa (in what is now Tanzania) that exploited this chemistry to produce iron in prehistoric times. Early African peoples lined a hole with a fuel of termite residues and added iron ore. Chamed reeds and charcoal provided the reducing substance. Finally, a chimney of mud was added. When this furnace was fired, a pool of iron collected in the bottom. 

One has to be careful, however, in defining time constants. The first important step is to set up the correct equations appropriately. If the prime interest is not the accumulation of oxygen in the liquid as defined previously, but the depletion of oxygen from the gas bubbles, then the appropriate balance equation becomes... 

The role of cell respiration has been taken into account to interpret the azo-dye conversion by particle-supported biofilm under aerobic conditions [5, 24]. The rapid depletion of oxygen expected/measured as one moves inside the biofilm promotes the establishment of the anoxic conditions needed for azo-dye conversion. 

Stations 23 and 24, located in the LSLE, have been subjected to hypoxic conditions since the 1980s. With depletion of oxygen in the bottom waters, the sediment oxygen penetration depth decreased, and Fe oxides, concentrated in the oxic sediment layer, were reductively dissolved and released adsorbed arsenic. Hence, the low oxygen levels during the last 25 years in the bottom waters is reflected in more reducing conditions in the sediment and increases in both dissolved and HA-extractable Fe and As. 

The first effect of paper mill wastewater discharge is the depletion of oxygen in the receiving waters, caused by oxygen-consuming microbial degradation of... 

The main effects of dose rate are due to an increase in temperature of the polymer and depletion of oxygen (for irradiation in air) at high dose rates. It seems unlikely that direct effects of dose rate should occur for electron, gamma and X irradiation, due to the low spatial density of the ionizations and excitations. 

Figure 12. Modeling and measurement of oxygen surface diffusion on Pt. (a) Model I adsorbed oxygen remains in equilibrium with the gas along the gas-exposed Pt surface but must diffuse along the Pt/YSZ interface to reach an active site for reduction. Model II adsorbed oxygen is reduced at the TPB but must diffuse there from the gas-exposed Pt surface, which becomes depleted of oxygen near the TPB due to a finite rate of adsorption, (b) Cotrell plot of current at a porous Pt electrode at 600 °C and = 10 atm vs time. The linear dependence of current with at short times implies semi-infinite diffusion, which is shown by the authors to be consistent only with Model II. (Reprinted with permission from ref 63. Copyright 1990 Electrochemical Society, Inc.)...

Anaerobic conditions often develop in hydrocarbon-contaminated subsurface sites due to rapid aerobic biodegradation rates and limited supply of oxygen. In the absence of O, oxidized forms or natural organic materials, such as humic substances, are used by microorganisms as electron acceptors. Because many sites polluted by petroleum hydrocarbons are depleted of oxygen, alternative degradation pathways under anaerobic conditions tend to develop. Cervantes et al. (2001) tested the possibility of microbially mediated mineralization of toluene by quinones and humus as terminal electron acceptors. Anaerobic microbial oxidation of toluene to CO, coupled to humus respiration, was demonstrated by use of enriched anaerobic sediments (e.g., from the Amsterdam petroleum harbor). Natural humic acids and... 

There is some experimental evidence which indicates that in dilute suspensions the inactivation is a function of concentration (BIO). There is considerable doubt as to whether or not this is an artifact caused by the depletion of oxygen in the system at the higher cell concentrations (H21). (See Sec. IY6b.)... 

Admittedly, when a cloud of droplets is burning in stoichiometric proportions in air, the last traces of the burning droplets must burn in atmospheres almost depleted of oxygen. Thus the reaction rate may be very poor, if high gas temperature does not more than offset low oxygen concentration. Nevertheless, the droplet at least will be exposed... 

It is apparent that the double-cell sensor can be operated in the limiting current mode (which corresponds to large values of Vg, of the order of 600 to 800 mV). The advantage of this mode of operation is that errors associated with the measurement of small values of Vg (e.g, less than 100 mV) are avoided. However, limiting current operation is generally undesirable since the problems associated with complete depletion of oxygen at the cathode of the pump cell can seriously limit the performance of the device. It is... 

NIDA s list of irreversible effects include hearing loss, limb spasms, brain damage, and bone marrow damage. Serious but potentially reversible effects include liver and kidney damage, and depletion of oxygen from the blood. 

Kemp, W.M., Sampou, P., Garber, J., Tuttle, J., and Boynton, W.R. (1992) Seasonal depletion of oxygen from bottom waters of Chesapeake Bay—roles of benthic and planktonic respiration and physical exchange processes. Mar. Ecol. Prog. Ser. 85, 137-152. 

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