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The Effect of Altitude on Oxygen Saturation

The amount of oxygen that any medium, such as water, can dissolve is its oxygen saturation. Oxygen is an essential element in a life on Earth and in chemical and environmental processes. At sea level, the pressure of the atmosphere is equivalent to 30 feet of water pressing down on a person̵7;s head. This air pressure decreases with increasing altitude because of the Earth̵7;s gravity. The gravitational pull between the Earth and air molecules is stronger when molecules are closer to the Earth̵7;s surface.

Atmosphere
- Oxygen constitutes 21 percent in all of the four layers of the Earth̵7;s atmosphere. With increasing height from the Earth̵7;s surface these are the troposphere, the stratosphere, the mesosphere and the ionosphere. The stratosphere contains 90 percent of the atmosphere̵7;s ozone, although its concentration is equivalent to only 9 parts per million in the atmosphere as a whole.
Blood
- Red blood cells, or hemoglobin, are proteins that carry oxygen within the bodies of humans and other vertebrates. The lower air pressure at high altitudes makes it difficult for oxygen to enter the lungs through breathing and results in hypoxia, or oxygen deprivation. The body acclimatizes over time to the altitude by producing more hemoglobin to carry oxygen and lungs increase in size to take in more of the thin air and its oxygen.
Water
- The oxygen saturation of water behaves in a complex way. The concentration of oxygen in water is about 1 percent. Its solubility in water increases as the salinity of the water decreases. Fresh water, the water present at high altitudes on land, contains more oxygen than seawater. Gas solubility decreases as air pressure decreases so oxygen saturation in water will decrease with altitude. Lower temperatures increase the solubility of gas in water. Colder temperatures at higher altitudes increase oxygen saturation in water.
Soil
- Air and oxygen are present in the pore spaces between soil grains. Oxygen levels generally decrease with depth in the soil as soil grains compact and pore space decreases. Soils with large pores have good drainage and hold more air and less water. The main demand for oxygen in soil is for the respiration (breathing) of plant roots and microorganisms. Microbial and plant root respiration increases as temperature increases. Temperature decreases with altitude, so the demand for oxygen decreases. This, in turn, increases the oxygen saturation in the soil. Water has the most effect on oxygen saturation in soils as air and water cannot share the same pore spaces. Drier climatic conditions at higher altitude increase the soil̵7;s oxygen saturation.

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