Development of Methods for Direct Determinations of Carbonate Ion Concentrations in Seawater

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This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Rising atmospheric carbon dioxide concentrations over the past two centuries have led to increasing carbon dioxide uptake by the oceans. This process, which is decreasing the pH of the upper ocean, is reducing oceanic carbonate ion concentrations and thus the level of saturation of calcium carbonate. If the trend continues, it will have a seriously negative impact on key marine organisms such as corals and some plankton. In view of the importance of carbonate ion concentrations to the oceans' rapidly evolving carbonate system, it is then highly desirable to move from the rank of derived carbon dioxide system variables to the list of primary measured variables. As such, a scientist from the University of South Florida will develop a new method to directly determine the carbonate ion concentrations in the laboratory, shipboard, or in-situ. The method would obtain carbonate ion concentrations with ultraviolet spectroscopic observations of Pb(II) absorbance spectra as the relative concentrations of lead carbonate and an ensemble of lead chloride complexes change in response to varying concentrations of dissolved carbonate. In addition, the scientist plans to refine and improve the accuracy of spectrophotometric carbonate ion measurements via shipboard analyses wherein carbonate ion concentrations are calculated using UV absorbance spectroscopy in addition to conventional state of the art measurements of total dissolved inorganic carbon, carbon dioxide fugacity, and pH.As regards broader impacts, the method will provide the ocean science community with another, perhaps easier and more accurate means of determining seawater saturation states (which influence both calcification rates and carbonate dissolution rates). One postdoc and one graduate student would be supported and trained as part of this project.