Question

effect of pressure on solubility of oxygen in blood at high altitude
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Answer 1

Altitude is increasing, the total atmospheric pressure decreases,

and then the partial pressure of oxygen is also decreasing (assuming a constant proportion of O2 in air).

Answer 2

If the partial pressure increases, then the DO concentration in water will also increase. When the altitude is increasing, the total atmospheric pressure decreases, and then the partial pressure of oxygen is also decreasing (assuming a constant proportion of O2 in air).