2.1 Dissolved Oxygen
The dissolved oxygen test measures the amount of lifesustaining
oxygen dissolved in the
water. Natural waters in equilibrium with the atmosphere will contain dissolved oxygen
concentrations ranging from about 5 to 14.5 mg O2 per liter depending on the water
temperature, salinity, and altitude. The dissolved oxygen (DO) concentration present in water
reflects atmospheric dissolution, as well as autotrophic and heterotrophic processes that
respectively, produce and consume oxygen. DO is the factor that determines whether