Table 7. The effect of constants on the calculation of the fugacity of CO2 (fCO2) at 20�Ca



Source of constants
Input Input Input Input Output Output Output
DIC Si(OH)4 PO4 fCO2@4�C TAlk fCO2@20�C ΔfCO2@20�C/ΔDIC

Roy et al. (1993) 2260 135 2.3 531.8 2371.3 1080 7.1
Goyet and Poisson (1989) 2260 135 2.3 531.8 2371.3 1076.4 7.1
Hansson (1973a,b) refit by Dickson and Millero (1987) 2260 135 2.3 531.8 2377.4 1018.8 6.7
Mehrbach et al. (1973) refit by Dickson and Millero (1987) 2260 135 2.3 531.8 2368.4 1033.0 7
Dickson and Millero (1987) refit of Hansson/Mehrbach 2260 135 2.3 531.8 2372.5 1042.7 6.9
GEOSECS (Takahashi et al. 1982) 2260 135 2.3 531.8 2367.2 1016.8 6.9
Peng et al. (1987) 2260 135 2.3 531.8 2378.1 1013.3 6.7

aAll values were calculated using theQUICKBASIC computer program of Lewis and Wallace (1998) with the default values for the secondary constants;the correction from 4�C to 20�C can cause the resulting pCO2 to differ by 65 µatm depending on the constants used. The ΔfCO2@20�C/ΔDIC values in µatm/(µmol/kg) show that in Pacific deep water a precision of 1.5 µmol/kg in DIC corresponds to approximately 10 µatm in fCO2.
Last modified: 2021-03-17T18:30:28Z