Experiments

We have now mostly completed a laboratory intercomparison exercise in which the electromotive forces of a series of test solutions are being measured using Harned Cells at the national metrology laboratories of Germany, France, and Japan; the National Institute of Standards and Technology; and the laboratory of WG 145 member Andrew Dickson at Scripps Institution of Oceanography (SIO) . The intercomparison involves two test solutions, one of very low ionic strength (0.1 mol kg^-1) and one of high ionic strength (5.0 mol kg^-1). Samples of both solutions were prepared at SIO and then distributed to all participants for measuring. Also, each laboratory prepares and measures their own samples.

Most of these laboratories are also making Harned cell measurements to contribute to the development of the speciation model. The purpose of the intercomparison is to quantify the consistency that can be expected of data from the different labs. Our first finding has been that the measurements on the very concentrated solution have highlighted differences in electrode preparation and treatment by the laboratories, which are important for our future work.

Other

Our draft manuscript describing the needs of oceangraphers for chemical speciation modelling tools, the results of surveys of the chemical oceanography community, and reviews of modelling tools by Working Group members, is now in the final stages of preparation. It has been commented on by Working Group members, and will be submitted to Best Practices in Ocean Observing.

This month Andrew Dickson will be advertising a postdoc position at his laboratory at Scripps. The researcher will be to carry out Harned cell measurements on salt solutions, and develop novel methods for the accurate measurement of heat capacities of solutions using a differential scanning calorimeter. If you are interested, please contact adickson@ucsd.edu.

Working Group member Martha Gledhill has been awarded a grant from the German Research Council DFG to characterise the chemistry of marine dissolved organic matter using the NICA-Donnan modelling approach. The results from this project will represent an important step in extending seawater speciation models to include dissolved organic matter. The project will start in January 2019.

Meetings

Simon Clegg, Andrew Dickson, and members of the national metrology laboratories of German and France will be attending the 17th ICPWS (the International Conference on the Properties of Water and Steam) in Prague at the beginning of September. There are sessions on the thermodynamic properties of seawater, and marine chemistry and seawater pH, which are very relevant to the activities of WG 145. We will be discussing our future work and its relationship to the concerns of the Joint Committe on Seawater, and particularly the development of marine pH and metrological traceability to SI units.

David Turner will be representing the Working Group at the Advanced Workshop on the Solution Chemistry of TCEs (technology-critical elements), to be held in January 2019 in Bialstock, Poland. The workshop includes consideration of  trace element speciation calculations, and the measurement of equilibrium constants and their incorporation into databases.