Investigating the Effect of Temperature and Salinity on the Concentration of Dissolved Oxygen in Water
Lab #5: Dissolved Oxygen Lab
Be sure to read and understand the below instructions BEFORE the lab!
Experiment 1: Investigating the Effect of Temperature and Salinity on the Concentration of Dissolved Oxygen in Water
Introduction:
In an aquatic environment, oxygen must be in a solution in a free state (O2) before it is available for use by organisms (bio-available). Its concentration and distribution in the aquatic environment are directly dependent on chemical and physical factors and are greatly affected by biological processes. In the atmosphere, there is an abundance of oxygen, with about 200 mL of oxygen/1 L air. In an aquatic environment, there are about 5-10 mL O2/1 L water. The concentration of the oxygen in aquatic environments is a very important component of water quality.
At 20C, oxygen diffuses 300,000 times faster in air than water, making the distribution of oxygen in air relatively uniform. Spatial distribution of oxygen in water, on the other hand, can be highly variable, especially in the absence of mixing by currents, winds, and tides.
Other chemical and physical factors – such as salinity, pH, and especially temperature- can affect the dissolved oxygen (DO) concentration and distribution. Salinity, usually expressed as parts per thousand (ppt), is the content of dissolved salts in water. Generally, as temperature and salinity increase, the solubility of oxygen in water decreases.
The partial pressure of oxygen in the air above the water affects the amount of DO in the water. Less oxygen is present at higher elevations since the air itself is less dense; therefore the water at high elevations contains less oxygen. At 4,000 meters in elevation (13,000 feet), the amount of dissolved oxygen in water is less than two-thirds what it is at sea level. All of these physical factors, along with oxygen concentration, work together to increase diversity in aquatic habitats.
Oxygen from the atmosphere is mixed into the water through
Be sure to read and understand the below instructions BEFORE the lab!
Experiment 1: Investigating the Effect of Temperature and Salinity on the Concentration of Dissolved Oxygen in Water
Introduction:
In an aquatic environment, oxygen must be in a solution in a free state (O2) before it is available for use by organisms (bio-available). Its concentration and distribution in the aquatic environment are directly dependent on chemical and physical factors and are greatly affected by biological processes. In the atmosphere, there is an abundance of oxygen, with about 200 mL of oxygen/1 L air. In an aquatic environment, there are about 5-10 mL O2/1 L water. The concentration of the oxygen in aquatic environments is a very important component of water quality.
At 20C, oxygen diffuses 300,000 times faster in air than water, making the distribution of oxygen in air relatively uniform. Spatial distribution of oxygen in water, on the other hand, can be highly variable, especially in the absence of mixing by currents, winds, and tides.
Other chemical and physical factors – such as salinity, pH, and especially temperature- can affect the dissolved oxygen (DO) concentration and distribution. Salinity, usually expressed as parts per thousand (ppt), is the content of dissolved salts in water. Generally, as temperature and salinity increase, the solubility of oxygen in water decreases.
The partial pressure of oxygen in the air above the water affects the amount of DO in the water. Less oxygen is present at higher elevations since the air itself is less dense; therefore the water at high elevations contains less oxygen. At 4,000 meters in elevation (13,000 feet), the amount of dissolved oxygen in water is less than two-thirds what it is at sea level. All of these physical factors, along with oxygen concentration, work together to increase diversity in aquatic habitats.
Oxygen from the atmosphere is mixed into the water through