Dissolved Gases in Water.
Dissolved Gases in Water. No naturally occurring body of water is free of dissolved gases. Natural and drinking water are in equilibrium with the air, and so will contain dissolved gases such as nitrogen, oxygen and carbon dioxide. Precise levels will depend on temperature, pressure and location.
Their spatial and temporal distribution is dependent on factors such as precipitation, inflow and outflow, physical factors like temperature, movement of water and chemical factors such as solution processes, combination and precipitation of reactions, complex formation etc.
Among the dissolved gases in water, oxygen and carbon dioxide are direct indicators of biological activity of water bodies.
Dissolved Oxygen is used for respiration by aquatic plants and animals.
Dissolved Carbon Dioxide is used for photosynthesis by aquatic plants.
Dissolved gases, particularly oxygen and carbon dioxide, are of interest because their concentrations in river water are influenced by biological processes of photosynthesis and respiration. The solubility of dissolved gases is temperature dependent and therefore it is useful to express concentrations as a percent saturation; that is, relative to the expected concentration for a solution in atmospheric equilibrium. Departures from equilibrium concentrations occur when the rate at which gases are exchanged with the atmosphere is slow relative to rates at which gases are produced or consumed through biological activity.