How much dissolved oxygen is normally contained in water (by volume)?

How much dissolved oxygen is normally contained in water (by volume)?

• A. 10-15%
• B. More than 25%
• C. 5-8%
• D. Less than 1%

Answer: (D)

Dissolved oxygen is a gas that is present in water in very small amounts. Even at typical aquatic oxygen levels measured in mg per liter, the corresponding volume of O2 as a fraction of the water is a tiny portion—generally well under 1%. For example, about 8 mg of O2 per liter translates to roughly 0.5–0.6% of the water’s volume as gas, depending on temperature. Higher solubility at very low temperatures can push it closer to 1%, but it stays less than a full percent of the water’s volume.

Dissolved oxygen is a gas that is present in water in very small amounts. Even at typical aquatic oxygen levels measured in mg per liter, the corresponding volume of O2 as a fraction of the water is a tiny portion—generally well under 1%. For example, about 8 mg of O2 per liter translates to roughly 0.5–0.6% of the water’s volume as gas, depending on temperature. Higher solubility at very low temperatures can push it closer to 1%, but it stays less than a full percent of the water’s volume.