R: Converts partial pressure of CO2 to mole fraction of CO2

p2xCO2 {seacarb} | R Documentation

## Converts partial pressure of CO2 to mole fraction of CO2

### Description

Converts pCO2 (partial pressure of CO2) into xCO2 (mole fraction of CO2)

### Usage

    p2xCO2(S=35, T=25, Patm=1, pCO2)

### Arguments

`S` | Salinity on the practical salinity scale, default is 35
`T` | Temperature in degrees Celsius, default is 25oC
`Patm` | Atmospheric pressure in atmospheres, default is 1.0 (this is not the hydrostatic pressure)
`pCO2` | Partial pressure of CO2 in μatm

### Details

The xCO2 (ppm) is computed from pCO2 (μatm) using the following equation: xCO2 = pCO2 / (Patm - pH2O), where pH20 is the vapor pressure of seawater computed following best practices (Dickson et al., 2007). That computed pH20 is identical, when rounded to the 4th decimal place, with that computed by the equation from Weiss and Price (1980).

### Value

`xCO2` | Mole fraction of CO2 in ppm.

### Note

Warning: pCO2 estimates below 100 m are subject to considerable uncertainty. See Weiss (1974) and Orr et al. (2015)

### Author(s)

James Orr james.orr@lsce.ipsl.fr

### References

Dickson A. G., Sabine C. L. and Christian J. R. (2007) Guide to best practices for ocean CO2 measurements. PICES Special Publication 3, 1-191.

Orr J. C., Epitalon J.-M. and Gattuso J.-P., 2015. Comparison of seven packages that compute ocean carbonate chemistry. Biogeosciences 12, 1483-1510.

Weiss, R. F. (1974) Carbon dioxide in water and seawater: the solubility of a non-ideal gas, Marine Chemistry, 2, 203-215.

Weiss, R. F. and Price, B. A. (1980) Nitrous oxide solubility in water and seawater, Marine Chemistry, 8, 347-359.

### See Also

`x2pCO2` and `vapress`

### Examples

    ## Convert atmospheric pressure from mbar to atm
       Patm_mbar = 1052                 # in millibar
       Patm      = Patm_mbar / 1013.25  # in atm
    ## Compute xCO2 from pCO2
       pCO2 = 380
       xCO2 = p2xCO2(T=25, S=35, Patm=Patm, pCO2=pCO2)
       print(xCO2)
    ## The result is 377.1546 ppm

[Package seacarb version 3.1.1 Index]