Dissolved oxygen characterization

Bailey R.T., Cruickshank F.R., Deans G., Gillanders R.N., Tedford M.C., Characterization of a fluorescent sol-gel encapsulated erythrosine B dissolved oxygen... 

The OUR is an activity-related quantitative measure of the aerobic biomass influence on the relationship between the electron donor (organic substrate) and the electron acceptor (dissolved oxygen, DO). It is a measure of the flow of electrons through the entire process system under aerobic conditions (Figure 2.2). The OUR versus time relationship of wastewater samples from sewers becomes a backbone for analysis of the microbial system. This relationship is crucial for characterization of the suspended wastewater phase in terms of COD components and corresponding kinetic and stoichiometric parameters of in-sewer processes. 

An estuary provides a particularly varied chemical environment which is characterized by strong ionic strength and pH gradients ranging from river to sea end members values. In addition one can usually observe a slight pH and dissolved oxygen minimum in the estuary itself which is enhanced in polluted estuaries. 

Seawater contains about 3.5% salts, in which the content of sodium chloride is about 80%. The concentration of dissolved salts as well as temperature and pressure influence the physical properties of seawater. The total salt concentration is usually called salinity . Salinity is generally measured by the electrical conductivity or determination of chloride content. At present, salinity(S) is defined as S = 1.80655 Cl (Cl is the concentration of chloride in seawater) [5]. Dissolved oxygen and silica are usually measured as additional parameters to characterize seawater. The concentrations of nitrogen and phosphorus are the indices of nutrients and measure the fertility and production of the oceans. 

Figure 15.6. Photosynthesis and respiration, (a) A well-balanced ecosystem may be characterized by a stationary state between photosynthetic production, P (rate of production of organic material) and heterotrophic respiration, R (rate of destruction of organic matter). Photosynthetic functions and respiratory functions may become vertically segregated in a lake or in the sea. In the surface waters the nutrients become exhausted by photosynthesis, (b) The subsequent destruction (respiration) of organism-produced particles after settling leads to enrichment of the deeper water layers with these nutrient elements and a depletion of dissolved oxygen. The relative compositional constancy of the aquatic biomass and the uptake (P) and release (R) of nutritional elements in relatively constant proportions (see equation 3) are responsible for a co-variance of carbon, nitrate, and phosphate in lakes (during stagnation period) and in the ocean an increase in the concentration of these elements is accompanied by a decrease in dissolved oxygen, (c, d) The constant proportions AC/AN/AP/AO2 typically observed in these waters are caused by the stoichiometry of the P-R processes.

Anaerobic - Describes a situation or an area characterized by the lack of oxygen. The term can also be used in reference to organisms such as some bacteria that can survive and grow in the absence of gaseous or dissolved oxygen. For example, many marine sediments are anaerobic below a depth of a few centimetres from the surface. Oil deposited in such areas degrades slowly and is primarily associated with anaerobic types of microorganisms. 

Pore waters in oxic zones are characterized by a dissolved oxygen content greater than 0.5 ml/1. Oxic carbonates prevail in (i) subaerial environments, such as the vadose zone where the pores are periodically filled with gas, air and/or water (ii) immediately below the sediment-water interface in aquatic environments and (iii) in the phreatic zone below the water table where all the pores are regularly filled with water. The thickness of the oxic zone depends on the penetration, by diffusion or advection, of oxygen below the sediment surface. Oxygen diffusion into pore waters is largely controlled by the organic content and the rate of deposition. In marine and lacustrine sediments the... 

The rated indicators, on the other hand, include the content of dissolved oxygen, active chlorine, ammonia and ammonia ions, iron, manganese, aluminium, zinc, magnesium, calcium, phosphates, nitrites, nitrates, chlorides, sulphates, humin substances, all dissolved constituents, anions of tensides, copper, hydrogen carbonates and pH value. This category also includes radioactivity characterized by total volume alpha-activity, and in surface waters also by total volume beta-activity. 

Many chemical reactions in wine are characterized by electron transfers, leading to the oxidation and reduction phenomena. These reactions occur simultaneously and continue until an oxidation-reduction equilibrium is reached. The oxidation-reduction potential of a wine is an observation of the oxidation and reduction levels of the medium at a certain equilibrium. This value is quite comparable to pH as a measurement of a wine s acidity. Its value is linked to the quantity of dissolved oxygen, just as pH depends on the quantity of (H+) protons. Furthermore, it is possible to define the normal potential Eq of a given oxidiz-ing/reducing couple when half the component is oxidized and half is reduced. This characterizes the wine s oxidation capacity in the same way as p indicates the strength of an acid. 

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