K1: First dissociation constant of carbonic acid (mol/kg)

Description Usage Arguments Details Value Author(s) References See Also Examples


First dissociation constant of carbonic acid (mol/kg)


K1(S=35, T=25, P=0, k1k2="x", pHscale="T", kSWS2scale="x", ktotal2SWS_P0="x", warn="y")



Salinity, default is 35


Temperature in degrees Celsius, default is 25oC


Hydrostatic pressure in bar (surface = 0), default is 0


"l" for using K1 and K2 from Lueker et al. (2000), "m02" from Millero et al. (2002), "m06" from Millero et al. (2006), "m10" from Millero (2010), "mp2" from Mojica Prieto et al. (2002), "p18" from Papadimitriou et al. (2018), "r" from Roy et al. (1993), "sb21" from Shockman & Byrne (2021), "s20" from Sulpis et al. (2020), and "w14" from Waters et al. (2014). "x" is the default flag; the default value is then "l", except if T is outside the range 2 to 35oC and/or S is outside the range 19 to 43. In these cases, the default value is "w14".


choice of pH scale: "T" for using the total scale, "F" for using the free scale and "SWS" for using the seawater scale, default is total scale


Conversion factor from the seawater scale (SWS) to the pH scale selected at the hydrostatic pressure value indicated. It is not required for all formulations of K1 and K2, nor when the hydrostatic pressure is 0. It is advised to use default value "x", in which case it is computed when required.


Conversion factor from the total scale to the SWS at an hydrostatic pressure of 0. It is not required for all formulations of K1 and K2. It is advised to use default value "x", in which case it is computed when required.


"y" to show warnings when T or S go beyond the valid range for K1; "n" to supress warnings. The default is "y".


The Lueker et al. (2000) constant is recommended by Guide to Best Practices for Ocean CO2 Measurements (2007). It is, however, critical to consider that each formulation is only valid for specific ranges of temperature and salinity:

The arguments can be given as a unique number or as vectors. If the lengths of the vectors are different, the longer vector is retained and only the first value of the other vectors is used. It can therefore be critical to use vectors of the same length.

The pressure correction was applied on the seawater scale. Hence, if needed, values were first transformed from the total scale to the seawater scale, the pressure correction applied as described by Millero (1995), and the value was transformed back to the required scale (T, F or SWS).



First dissociation constant of carbonic acid (mol/kg)


Jean-Marie Epitalon and Jean-Pierre Gattuso gattuso@obs-vlfr.fr


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.

DOE 1994 Handbook of methods for the analysis of the various parameters of the carbon dioxide system in sea water. ORNL/CDIAC-74. Oak Ridge,Tenn.: Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory.

Lueker T. J., Dickson A. G., and Keeling C. D., 2000 Ocean pCO2 calculated from dissolved inorganic carbon, alkalinity, and equations for K1 and K2: validation based on laboratory measurements of CO2 in gas and seawater at equilibrium. Marine Chemistry 70 105-119.

Millero F. J., 1995 Thermodynamics of the carbon dioxide system in the oceans. Geochimica Cosmochimica Acta 59: 661-677.

Millero F. J., Pierrot D., Lee K., Wanninkhof R., Feely R., Sabine C. L., Key R. M. and Takahashi T., 2002. Dissociation constants for carbonic acid determined from field measurements. Deep Sea Research Part I: Oceanographic Research Papers 49:1705-1723.

Millero F. J., Graham T. B., Huang F., Bustos-Serrano H., and Pierrot D., 2006 Dissociation constants of carbonic acid in seawater as a function of salinity and temperature. Marine Chemistry 100, 80-84.

Millero F. J., 2010 Carbonate constant for estuarine waters. Marine and Freshwater Research 61: 139-142.

Mojica Prieto F. J. and Millero F. J., 2002. The values of pK1 + pK2 for the dissociation of carbonic acid in seawater. Geochimica et Cosmochimica Acta 66, 2529-2540.

Papadimitriou S., Loucaides S., Rérolle V. M. C., Kennedy P., Achterberg E. P., Dickson A. G., Mowlem M. and Kennedy H., 2018. The stoichiometric dissociation constants of carbonic acid in seawater brines from 298 to 267 K. Geochimica et Cosmochimica Acta 220, 55-70.

Roy R. N., Roy L. N., Vogel K. M., Porter-Moore C., Pearson T., Good C. E., Millero F. J. and Campbell D. M., 1993. The dissociation constants of carbonic acid in seawater at salinities 5 to 45 and temperatures 0 to 45oC. Marine Chemistry 44, 249-267.

Schockman, K.M., Byrne, R.H., 2021. Spectrophotometric determination of the bicarbonate dissociation constant in seawater, Geochimica et Cosmochimica Acta..

Sulpis O., Lauvset S. K. and Hagens M., 2020. Current estimates of K1* and K2* appear inconsistent with measured CO2 system parameters in cold oceanic regions. Ocean Science 16, 847-862.

Waters, J., Millero, F. J., and Woosley, R. J., 2014. Corrigendum to “The free proton concentration scale for seawater pH”, [MARCHE: 149 (2013) 8-22], Marine Chemistry 165, 66-67.

See Also




Example output

Loading required package: oce
Loading required package: testthat
Loading required package: gsw
[1] 1.421828e-06
[1] "mol/kg-soln"
attr(,"pH scale")
[1] "total scale"
[1] "Luecker et al. (2000)"

seacarb documentation built on Feb. 22, 2021, 5:06 p.m.