Saturated dissolved oxygen values at various temperatures

1. Dissolved oxygen refers to the oxygen content dissolved in water. Also known as oxygen saturation value, it refers to the concentration of dissolved oxygen in a water body when the oxygen exchange between the water body and the atmosphere is in balance. Under normal atmospheric pressure conditions, the saturated dissolved oxygen OS only changes with the water temperature T, and the saturated dissolved oxygen also changes with the atmospheric pressure. The lower the atmospheric pressure, the smaller the OS value. Saturated dissolved oxygen also changes with the salinity of the water. As the salinity increases, the OS value decreases.
2. Its content is related to the oxygen partial pressure in the air and water temperature. The partial pressure of oxygen changes very little, so water temperature is the main influencing factor. The lower the water temperature, the higher the dissolved oxygen in the water. The dissolved oxygen content of clean ground water is close to saturation. When a large number of algae plants grow in the water, the oxygen released by their photosynthesis can make the dissolved oxygen in the water supersaturated.
3. When there is organic matter polluting the water body or a large number of algae die, the dissolved oxygen is continuously consumed and decreased, and even the water body is in an anaerobic state. At this time, anaerobic microorganisms in the water multiply, and the organic matter undergoes putrefaction and decomposition, making the water black and smelly. Therefore, dissolved oxygen in water can be used as an indirect indicator of organic pollution and its degree of self-purification.