The amount of oxygen that may become dissolved in a given amount of water is most related to

• A. Turbidity
• B. Total dissolved solids
• C. Hardness
• D. Temperature

Answer: (D)

Dissolved oxygen capacity in water is governed by oxygen solubility, which depends on temperature. As temperature increases, the solubility of oxygen decreases, so cold water can hold more dissolved oxygen than warm water. That makes temperature the factor that most directly determines how much oxygen can be dissolved in a given amount of water. Turbidity involves suspended particles and can influence oxygen levels indirectly through microbial activity and light, but it does not set the water’s capacity to hold oxygen. Hardness and total dissolved solids describe mineral content and do not control oxygen solubility.