Air Saturation Lab Report
Dissolved oxygen enters water through the air and plant. Dissolved oxygen produce by the atmosphere and the process is called air saturation. The gasses a stable body of water with no stratification, dissolved oxygen will remain at 100% air saturation. 100% air saturation means that the water is holding as many dissolved gas molecules as it can in equilibrium. At equilibrium, the percentage of each gas in the water would be equivalent to the percentage of that gas in the atmosphere like its partial pressure. The water will slowly absorb oxygen and other gasses from the atmosphere until it reaches equilibrium at complete saturation. This process is sped up by wind-driven waves and other sources of aeration. In deeper waters, DO can remain below 100% due to the respiration of aquatic organisms and microbial decomposition. These deeper levels of water often do not reach 100% air saturation equilibrium because they are not shallow enough to be affected by
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the waves and photosynthesis at the surface.
In addition to plant-generated oxygen, the earth’s atmospheric pressure is constantly pushing tiny molecules of dissolved-oxygen gas into the surface waters.
The process is known as diffusion. As oxygen gas is pushed into water, excess oxygen from the water is simultaneously being released into the air. Wind and wave action or mechanical aerators accelerate diffusion by creating more surface area for oxygen to enter the water.
Water’s unique ability to hold and release oxygen makes it possible for fish and other animals to breathe (respire) underwater. However, oxygen concentrations in aquatic environments are rarely stable. When the sun is shining and aquatic plants (including algae) are photosynthesizing at full capacity, oxygen is plentiful. However, after the sun sets, photosynthetic activity and hence, oxygen concentration is greatly reduced. Usually there is a dissolved oxygen buffer in the water to last until morning, when the process begins again. However, if something alters the pattern, oxygen can be
depleted.
Dissolved oxygen is also produced as a waste product of photosynthesis from phytoplankton, algae, seaweed and other aquatic plants. Light can penetrate water, though the depth that it can reach varies due to dissolved solids and other light-scattering elements present in the water. Depth also affects the wavelengths available to plants, with red being absorbed quickly and blue light being visible past 100 m. In clear water, there is no longer enough light for photosynthesis to occur beyond 200 m, and aquatic plants no longer grow. In turbid water, this photic (light-penetrating) zone is often much shallower. Regardless of wavelengths available, the cycle doesn’t change. In addition to the needed light, CO2 is readily absorbed by water (it’s about 200 times more soluble than oxygen) and the oxygen produced as a byproduct remains dissolved in water. The basic reaction of aquatic photosynthesis remains:
CO2 + H2O → (CH2O) + O2
However, the aquatic photosynthesis is light dependant due to the wavelength that the sunlight can reach. The photosynthesis also only takes place on day time and oxygen produced will peak during daylight hours and decline at night.
the waves and photosynthesis at the surface.
In addition to plant-generated oxygen, the earth’s atmospheric pressure is constantly pushing tiny molecules of dissolved-oxygen gas into the surface waters.
The process is known as diffusion. As oxygen gas is pushed into water, excess oxygen from the water is simultaneously being released into the air. Wind and wave action or mechanical aerators accelerate diffusion by creating more surface area for oxygen to enter the water.
Water’s unique ability to hold and release oxygen makes it possible for fish and other animals to breathe (respire) underwater. However, oxygen concentrations in aquatic environments are rarely stable. When the sun is shining and aquatic plants (including algae) are photosynthesizing at full capacity, oxygen is plentiful. However, after the sun sets, photosynthetic activity and hence, oxygen concentration is greatly reduced. Usually there is a dissolved oxygen buffer in the water to last until morning, when the process begins again. However, if something alters the pattern, oxygen can be
depleted.
Dissolved oxygen is also produced as a waste product of photosynthesis from phytoplankton, algae, seaweed and other aquatic plants. Light can penetrate water, though the depth that it can reach varies due to dissolved solids and other light-scattering elements present in the water. Depth also affects the wavelengths available to plants, with red being absorbed quickly and blue light being visible past 100 m. In clear water, there is no longer enough light for photosynthesis to occur beyond 200 m, and aquatic plants no longer grow. In turbid water, this photic (light-penetrating) zone is often much shallower. Regardless of wavelengths available, the cycle doesn’t change. In addition to the needed light, CO2 is readily absorbed by water (it’s about 200 times more soluble than oxygen) and the oxygen produced as a byproduct remains dissolved in water. The basic reaction of aquatic photosynthesis remains:
CO2 + H2O → (CH2O) + O2
However, the aquatic photosynthesis is light dependant due to the wavelength that the sunlight can reach. The photosynthesis also only takes place on day time and oxygen produced will peak during daylight hours and decline at night.