Assumptions in the seawater 'total' pH scale, and implications for carbonate dissociation constants

Title: Assumptions underlying the seawater 'total' pH scale, and implications for measured carbonate dissociation constants
Recorded for the Ocean Sciences Meeting, 2022
MarChemSpec fundamentals, and marine applications
This talk describes how MarChemSpec has been used to quantify the assumptions inherent in the total pH scale used by chemical oceanographers, relative to conventional thermodynamic total H+ concentration. We also explain the meaning of the extrapolation of Tris buffer pH to hypothetical zero buffer molality in the artificial seawater medium. The effect of these assumptions on measured carbonate dissociation constants (K1, K2, and K1.K2) is described, and shown to be small relative to uncertainties in the data. We compare model-calculated carbonate dissociation constants with measured values, which yields insights into the consistency of the different datasets and suggests that model-calculated K2 below salinities of about 5 are likely to be more accurate that measured values.
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