Calculate dissolved methane saturation

Calculates the dissolved methane concentration in equilibrium with the atmosphere from water temperature, barometric pressure, and salinity, using the atmospheric-equilibrium solubility equation of Wiesenburg and Guinasso (1979).

Usage

calc_CH4sat(
  temp_water,
  atmo_press,
  units = "atm",
  salinity = 0,
  xCH4_ppm = 1.9,
  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).

xCH4_ppm

Numeric vector. Dry-air mole fraction of CH4 in parts per million. Defaults to 1.9, 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 CH4 saturation in the requested units.

Details

The equilibrium concentration follows Wiesenburg and Guinasso (1979) eq 7 with their volumetric (nmol/L) coefficients (Table VI), in which the dry-air mole fraction enters the solubility equation directly. A vapor-pressure correction scales the 1 atm result to the supplied barometric pressure.

References

Wiesenburg, D.A., and Guinasso, N.L. (1979). Equilibrium solubilities of methane, carbon monoxide, and hydrogen in water and sea water. Journal of Chemical and Engineering Data, 24(4), 356-360.

See also

calc_O2sat(), calc_CO2sat(), calc_N2Osat(), calc_N2sat(), calc_Arsat()

Examples

calc_CH4sat(temp_water = 20, atmo_press = 1, salinity = 0)
#> [1] 0.002873362

calc_CH4sat(
  temp_water = c(5, 15, 25),
  atmo_press = 101.325,
  units = "kPa",
  xCH4_ppm = 1.9,
  out_units = "mg/L"
)
#> [1] 6.673778e-05 5.155430e-05 4.155221e-05