p2xCO2 {seacarb}

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 \muatm

Details

The xCO2 (ppm) is computed from pCO2 (\muatm) 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 [e-mail]

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