Calculate dissolved carbon dioxide saturation

Calculates the dissolved carbon dioxide concentration in equilibrium with the atmosphere from water temperature, barometric pressure, and salinity, using the Weiss and Price (1980) solubility function for carbon dioxide as a non-ideal atmospheric trace gas.

Usage

calc_CO2sat(
  temp_water,
  atmo_press,
  units = "atm",
  salinity = 0,
  xCO2_ppm = 420,
  out_units = "umol/L"
)

Arguments

temp_water: Numeric vector. Water temperature in degrees Celsius.
atmo_press: Numeric vector. Barometric pressure at the site.
units: Character string. Units of atmo_press. See convert_pressure() for accepted pressure units. Defaults to "atm".
salinity: Numeric vector. Salinity in parts per thousand. Defaults to freshwater (0).
xCO2_ppm: Numeric vector. Dry-air mole fraction of CO2 in parts per million. Defaults to 420, an approximate present-day value; override it with a measured atmospheric value where available.
out_units: Character string. Output concentration units, either "umol/L" (the default) or "mg/L".

Value

Numeric vector of dissolved CO2 saturation in the requested units.

Details

The equilibrium concentration is \(C^* = x' F\), where \(x'\) is the dry-air mole fraction and \(F\) is the moist-air solubility function of Weiss and Price (1980), evaluated with their volumetric coefficients (Table VI). A vapor-pressure correction scales the 1 atm result to the supplied barometric pressure. To convert a measured CO2 mole fraction (rather than the atmospheric value) to a dissolved concentration, see calc_CO2_molKg().

References

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

Examples

calc_CO2sat(temp_water = 20, atmo_press = 1, salinity = 0)
#> [1] 15.99144

calc_CO2sat(
  temp_water = c(5, 15, 25),
  atmo_press = 101.325,
  units = "kPa",
  xCO2_ppm = 420,
  out_units = "mg/L"
)
#> [1] 1.1690779 0.8243273 0.6064212