The oxygenation environment can be important for the sustainability of a particular ecosystem. Insufficient oxygen (environmental hypoxia) can occur in water bodies such as ponds and rivers, tending to suppress the presence of aerobic organisms such as fish. Deoxygenation increases the relative population of anaerobic organisms such as plants and some bacteria, resulting in kill fish and other adverse events. Its net effect is to alter the natural balance by increasing anaerobic concentration to aerobic species.
Oxygenation through water aeration can be part of the environmental improvement of a normally stagnant water body. For example, Bubbly Creek in Chicago, Illinois, is hypoxic (oxygen deprivation) due to its use as an open sewer by the meat packing industry of Chicago but has been oxygenated by incorporating compressed air into its waters, increasing fish populations. Similar techniques have previously been used on the Thames River.
Dissolved Oxygen ( DO ) is measured in standard solution units such as milliliters O 2 per liter (mL/L), milimoles O 2 < per liter (mg/L) and mol O 2 per cubic meter (mol/mÃ,³). For example, in fresh water under atmospheric pressure at 20 ° C, O 2 saturation is 9.1 °, mg/L.
In an aquatic environment, oxygen saturation is a relative measure of the amount of oxygen (O 2 ) dissolved in water compared to equilibrium conditions.
Supersaturation oxygen (ie a saturation level above 100%) can occur naturally. The most common cause is the production of oxygen by an active species of photosynthesis such as plants and algae. According to Henry's law, the equilibrium oxygen concentration is proportional to the partial pressure of the oxygen gas. Since air contains about 21% oxygen, the pure oxygen gas equilibrium concentration equals to nearly 500% of air saturation. Another reason is that the oxygen concentration can slowly adjust to environmental changes. Rapid increase in temperature can reduce the oxygen equilibrium concentration to a value below the actual concentration in water, giving rise to more than 100% saturation until the system has time to balance through diffusion. Supersaturation can sometimes be harmful to the organism and cause decompression disease.
Solubility tables (based on temperature) and corrections for different salinity and pressure can be found on the USGS website. Tables like this DO in milliliters per liter (mL/L) are based on empirical equations that have been worked out and tested:
- ln (DO) = A1 A2 * 100/T A3 * ln (T/100) A4 * T/100 S * [B1 B2 * T/100 B3 * (T/100) 2 ]
where ln is the symbol for natural logarithm and the coefficient takes the following values:
To convert the above DO calculation from mL/L to mg/L, multiply the answer with (P/T) * 0,55130, P = mmHg, T = Kelvin
Video Oxygenation (environmental)
Measurement
The DO level is usually measured using a "coarse oxygenated oxygen" apparatus (RDO) that measures the glow capability of the sample. Increased oxygen levels result in improved characterization of the quenching and allow for accurate measurements to be performed with probes that require minimal maintenance. Prior to the development of redox technology RDO technology was used which measures oxygen levels using clark electrodes. Electrochemical equipment requires sufficient maintenance to remove fouling and prevent membrane degradation. The redox method can also display some cross sensitivity to other gases such as H 2 S.
For small or low concentrations (less than 2 ppm), the RDO equipment sample is significantly better because it does not consume oxygen in the sample (and therefore does not require stirring) or strives to measure zero.
Wet chemical methods such as the Winkler test for dissolved oxygen can also be used for DO measurements but as with all these wet chemical measurements it requires skilled technicians to get accurate results.
Maps Oxygenation (environmental)
See also
- Oxygenation
- Streeter-Phelps equation
References
External links
- Dissolved Oxygen Explained
- Technical Toolbox - Oxygen Solubility in Fresh Water and Sea Water
Source of the article : Wikipedia
0 Comments