Calculating atmospheric partial pressure of oxygen

In summary, the partial pressure of oxygen is influenced by altitude, temperature, and relative humidity.
  • #1
GhostLineage
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TL;DR Summary
How do I calculate atmospheric partial pressure of oxygen using factors like altitude, temperature, humidity, and latitude?
I study genotype-environment associations in alpine species. I frequently see altitude as the sole predictor of partial pressure of oxygen in the literature concerning hypoxia adaptations. However, I understand that partial pressure of oxygen is also influenced by temperature, humidity, and latitude. Does anyone know of a way to calculate partial pressure of oxygen for points across a landscape using altitude, temperature, and possibly other abiotic factors? Or are the effects of other factors fairly negligible compared to altitude? Thanks!
 
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  • #2
GhostLineage said:
negligible compared to altitude?
YMMV.
 
  • #3
Welcome to PF.

Air temperature, density, and pressure change with altitude.

To compute the partial pressure of oxygen, you need to know only two things, the pressure of the atmosphere and the fractional proportion that is oxygen. The partial pressure of oxygen is simply the product of those two parameters.

https://en.wikipedia.org/wiki/Partial_pressure
 
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  • #4
Baluncore said:
Welcome to PF.

Air temperature, density, and pressure change with altitude.

To compute the partial pressure of oxygen, you need to know only two things, the pressure of the atmosphere and the fractional proportion that is oxygen. The partial pressure of oxygen is simply the product of those two parameters.

https://en.wikipedia.org/wiki/Partial_pressure
Thanks for your reply. I should have been more specific that I'm looking to calculate an estimate of partial pressure of oxygen for points across a landscape without already knowing the atmospheric pressure. I have lat/long, altitude, and other variables accessible from WorldClim. I see papers like this:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3852963/
where partial pressure of oxygen is inferred using altitude, but no other environmental variables (see figure 1).

But then I see sources describing how temperature and latitude affect barometric pressure, and can increase hypoxia (on the first page):
https://eu-ireland-custom-media-pro...EAEU/eSample/9780323359429-sample-chapter.pdf
They talk about how if the summit of Mt. Everest were at the same latitude as Denali, Everest would be impossible to climb without supplemental oxygen.

I'm hoping to find a nice equation out there like the one that Zhao et al. 2013 (posted above) used, but includes temperature, and maybe other factors like latitude and humidity.
 
  • #5
You might try following/looking-at the references in the article you linked to.

There are 3 references just in the brief section "THE ENVIRONMENT OF HIGH ALTITUDE" on page 2.

Cheers,
Tom
 
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  • #6
GhostLineage said:
I should have been more specific that I'm looking to calculate an estimate of partial pressure of oxygen for points across a landscape without already knowing the atmospheric pressure. I have lat/long, altitude, and other variables accessible from WorldClim.
This is the process you will need to follow.

1. Identify the atmospheric pressure at sea level, site altitude, temperature, and relative humidity, RH%.

2. Compute the site air pressure at that altitude from the standard model.
Pa = Po * ( 1 - ( Hft * 6.87535*10-6 ) )^5.2561; where Hft is the height in feet above sea level, Po and Pa are air pressure at sea level and at altitude respectively. ^5.2561 means raised to the power of 5.2561.

3. Convert the RH% to pp-H2O at the site temperature and computed air pressure. That is more of a challenge since it is based on temperature and pressure, and the units are very important.

4. Subtract the pp-H2O from the air pressure to get the dry air pressure.

5. Multiply the dry air pressure by the 0.20946 to get the pp-O2.

Now you must identify what information is available, and the units that are used.
 
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  • #7
You also need to specify how precise your determination of pp-O2 needs to be.
 
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  • #8
Tom.G said:
You might try following/looking-at the references in the article you linked to.

There are 3 references just in the brief section "THE ENVIRONMENT OF HIGH ALTITUDE" on page 2.

Cheers,
Tom
I tried West 1984 and it wasn't what I was looking for. Not sure about those other two, thanks for suggesting.
 
  • #9
Baluncore said:
This is the process you will need to follow.

1. Identify the atmospheric pressure at sea level, site altitude, temperature, and relative humidity, RH%.

2. Compute the site air pressure at that altitude from the standard model.
Pa = Po * ( 1 - ( Hft * 6.87535*10-6 ) )^5.2561; where Hft is the height in feet above sea level, Po and Pa are air pressure at sea level and at altitude respectively. ^5.2561 means raised to the power of 5.2561.

3. Convert the RH% to pp-H2O at the site temperature and computed air pressure. That is more of a challenge since it is based on temperature and pressure, and the units are very important.

4. Subtract the pp-H2O from the air pressure to get the dry air pressure.

5. Multiply the dry air pressure by the 0.20946 to get the pp-O2.

Now you must identify what information is available, and the units that are used.
This is great, thanks! Do you have a source or name I can refer to in citing this equation? Since originally posting I also came across the hypsometric formula, but it doesn't include humidity (at least in the sources I saw).

I have everything needed here - temp in C, altitude in meters, and relative humidity.
 
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  • #10
hutchphd said:
You also need to specify how precise your determination of pp-O2 needs to be.
I'm really just looking for an index for downstream statistics, it doesn't need to be incredibly precise.
 
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  • #11
GhostLineage said:
This is great, thanks! Do you have a source or name I can refer to in citing this equation? Since originally posting I also came across the hysometric formula, but it doesn't include humidity (at least in the sources I saw).
http://www.scymed.com/en/smnxpr/prdpb394.htm

The formula presented here follows the “Equation of State” and the 1956 U.S. standard assumption. On August 23, 1945 in document AN-T-81, the Army-Navy published the equation that relates air pressure to altitude. That equation follows:
Pa = Po ( 1 - 6.87535*10-6Hc )5.2561

where Pa is the air pressure at altitude Hc at a given sea level pressure Po. Sea level pressure assumed to be 29.92 inches of mercury (760mmHg)
 
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  • #12
hutchphd said:
http://www.scymed.com/en/smnxpr/prdpb394.htm

The formula presented here follows the “Equation of State” and the 1956 U.S. standard assumption. On August 23, 1945 in document AN-T-81, the Army-Navy published the equation that relates air pressure to altitude. That equation follows:
Pa = Po ( 1 - 6.87535*10-6Hc )5.2561

where Pa is the air pressure at altitude Hc at a given sea level pressure Po. Sea level pressure assumed to be 29.92 inches of mercury (760mmHg)
Great, thanks so much!
 
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1. What is the formula for calculating atmospheric partial pressure of oxygen?

The formula for calculating atmospheric partial pressure of oxygen is: PO2 = (Patm - PH2O) x FO2, where PO2 is the partial pressure of oxygen, Patm is the total atmospheric pressure, PH2O is the partial pressure of water vapor, and FO2 is the fraction of oxygen in the atmosphere.

2. How do you determine the partial pressure of water vapor in the atmosphere?

The partial pressure of water vapor in the atmosphere can be determined using the Clausius-Clapeyron equation, which takes into account temperature and relative humidity. Alternatively, it can be looked up in a table or calculated using a weather station's measurements.

3. What is the standard atmospheric pressure used in the calculation?

The standard atmospheric pressure used in the calculation is 1 atmosphere (atm), which is equivalent to 101.325 kilopascals (kPa) or 760 millimeters of mercury (mmHg).

4. Why is it important to calculate atmospheric partial pressure of oxygen?

It is important to calculate atmospheric partial pressure of oxygen because it is a key factor in determining the availability of oxygen for respiration and other biological processes. It is also used in various fields such as aviation, scuba diving, and medical treatments.

5. How does altitude affect the calculation of atmospheric partial pressure of oxygen?

As altitude increases, the total atmospheric pressure decreases, which in turn affects the partial pressure of oxygen. This is because the fraction of oxygen in the atmosphere remains constant at approximately 21%, but the total atmospheric pressure decreases. Therefore, the higher the altitude, the lower the partial pressure of oxygen will be.

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