Equations describing the CO2 system in seawater

The equations given here include the contributions of only bicarbonate, carbonate, borate and hydroxide to the total alkalinity. As pointed out in Section 8.4.1, the contributions from other bases present in seawater are usually small. The system is now defined by three mass balance equations (8-33) to (8-35) and five stability constants (Eqs. (8-36) to (8-40))  

If all the stability constants, together with the total borate concentration B-r (Uppstrdm, 1974), are known, then these eight equations have ten unknowns Aj-, Cx, /(CO2), H 1 (= ICTP ) and the concentrations of dissolved C02/carbonic acid [H2CO3 ], hydrogen carbonate, carbonate, boric acid, borate and hydroxide. It follows, therefore, that only two unknowns i.e., two of the measurable parameters Aj, C, /(CO2) and pH) need be determined in order to be able to calculate all the others. The values assigned to the stability constants are discussed in Section 8.6.2, and the total boron concentration can be calculated as fix = 0-00042 S/35 mol/(kg-seawater) Whitfield and Turner, 1981). 

Over the last 25 years, several groups have made reliable determinations of the stability constants defined in Eqs. (8-36) to (8-40). Unfortunately, these constants are not always directly comparable with one another since different groups have used different concentration scales and pH scales. The discussion will be restricted to the options recommended here for measurement and for reporting of results, Le., the mol/(kg-seawater) concentration scale and the total hydrogen ion concentration pH scale pH(T). 

Tible 8-1. Recommended stability constants on the mol/(kg-seawater) and pH(T) scales. 

Standard deviation about fitting equation given by Millero (1979), Eq. (8-45). 

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