Which factor has the most significant influence on the solubility of dissolved oxygen (DO) in water?

The solubility of dissolved oxygen (DO) in water is primarily affected by temperature. As water temperature increases, the solubility of oxygen decreases. This is because warmer water has higher kinetic energy, which allows gas molecules, such as oxygen, to escape more readily into the atmosphere. Conversely, cooler water can hold more dissolved oxygen due to lower kinetic energy, which makes it more conducive for gas molecules to remain in solution.

While pH level, salinity, and pressure can also influence the solubility of DO, their effects are less significant compared to temperature. Changes in pH can affect biological processes and the chemical forms of oxygen, salinity can impact gas solubility as freshwater and saltwater have different capacities for dissolved gases, and pressure influences gas solubility to some extent—particularly at great depths in oceans. However, these factors do not have the same prominent and direct impact on DO solubility as temperature does. Thus, understanding the temperature's role is crucial for assessing aquatic environments and managing oxygen levels in wastewater treatment processes.