The third of our papers on chemical speciation modelling is now at the pre-proof stage of publication. It describes our model of acid-base equilibria in natural waters containing the solutes present in standard seawater: the major ions (Na⁺, Mg²⁺, Ca²⁺, K⁺, Sr²⁺, Cl^–, and SO₄^2-) plus H⁺, OH^–, HSO₄^–, and the components of dissolved carbonate (CO₂*, HCO₃^–, CO₃^2-), borate (B(OH)₄^– and B(OH)₃), and fluoride (F^– and HF):

• S. L. Clegg, J. F. Waters, D. R. Turner, and A. G. Dickson (2023) Chemical speciation models based upon the Pitzer activity coefficient equations, including the propagation of uncertainties. III. Seawater from the freezing point to 45 °C, including acid-base equilibria. Mar. Chem. (pre-proof), art. no. 104196, https://doi.org/10.1016/j.marchem.2022.104196

The paper, and its extensive supporting information, includes detailed comparisons of model calculations with the measured carbonate system constants K₁, K₂, and K_B and also the dissociation product of water (K_W) and saturation of seawaters with respect to calcite. Please get in touch with Simon Clegg (s.clegg@uea.ac.uk) or David Turner (david.turner@marine.gu.se) if you would like to know more.

SCOR Working Group 145 has now transitioned to the Chemical Speciation Task Group of the Joint Committee on the Properties of Seawater which is a permanent committee sponsored by the International Association for the Properties of Water and Steam (IAPWS), SCOR, and by the International Association for the Physical Sciences of the Oceans (IAPSO). Our work will continue under this new affiliation, focusing on the development and application of the models, free software to run the models, and the extension and basis in SI of the total pH scale (in collaboration with national metrology institutes of the USA, Germany, and Japan).

This website will be revised over the following months to reflect these changes, including to become a source for software downloads and online calculations.