Aquatic life oxygen requirements

We can use Henry s law to verify that the concentration of oxygen in lake water is normally adequate to sustain aquatic life, which requires a concentration of at least 1.3 X 10-4 mol-L 1. The partial pressure of oxygen is 0.21 atm at sea level, so the molar solubility of oxygen is... 

Fish and other aquatic life will require water to be oxygenated. 

This equation indicates that every molecule of urea requires 9/2 molecules of oxygen for complete oxidation. The oxygen required for the reactions depletes the receiving water of oxygen, causing the death of aquatic life. 

Industries, especially those that generate electric power, use a tremendous amount of water to cool steam and condense it back to water. This water is normally taken from a lake or stream, used in the cooling process, and then returned to the same body of water. If the heated water is returned directly to the lake or stream, the increase in temperature may cause the oxygen levels to decrease below those required for the survival of certain types of fish. The increased temperature may also trigger or repress natural cycles of aquatic life, such as spawning. 

The concentration of Oj in water required to support aerobic aquatic life is about 4.0 mg dm T What is the minimum partial pressure of oxygen in the atmosphere that can achieve this concentration ... 

Several important characteristics of unpolluted water should be noted. One of these is gas solubility. Since it is required to support aquatic life and maintain water quality, oxygen is the most important dissolved gas in water. Water in equilibrium with air at 25°C contains 8.3 milligrams per liter (mg/L) of dissolved O2. Water alkalinity (see Section 11.6) is defined as the ability of solutes in water to neutralize added strong acid. Water hardness is due to the presence of calcium ion, Ca +, and, to a lesser extent, magnesium ion, Mg. ... 

The small amount of a nonpolar gas that does dissolve may be vital. At 25°C and 1 atm, the solubility of Oj is only 3.2 mL/lOO. mL of water, but aquatic animal life requires it. At times, the solubility of a nonpolar gas may seem high because it is also reacting with solvent. Oxygen seems more soluble in blood than in water because it bonds to hemoglobin in red blood cells. Carbon dioxide, which is essential for aquatic plants and coral-reef growth, seems very soluble in water ( of H2O at 25°C and 1 atm) because it is dissolving and reacting ... 

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