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AN UPDATED PROCEDURE FOR SPECTROPHOTOMETRIC DETERMINATION OF CARBONATE ION CONCENTRATION IN SEAWATER AND A THERMODYNAMIC EXAMINATION OF TEMPERATURE EFFECTS (E)

The marine CO2 system has historically been examined through determination of at least two of four measurable parameters—pH, AT, CT, and pCO2—and subsequent calculation of additional parameters. Recently, direct spectrophotometric determination of carbonate ion concentration has added a fifth measurable parameter. Carbonate ion concentration is significant in marine systems as it plays a role in biological calcification and dissolution processes. At typical seawater pH, the major lead species present are PbCO3 and Pb(II) chloride complexes. These species show distinct absorbance spectra in the ultraviolet. Consequently, with knowledge of chloride concentration (from salinity) and an appropriate model, carbonate ion concentrations can be determined from absorbance ratios in the ultraviolet spectrum. Beginning in 2013, field observations have been utilized to refine the model used to calculate carbonate from Pb(II) absorbance ratios in seawater. However, prior iterations of the model have suggested the potential for regional variations that would affect their global applicability. This work remedies previous problems by fitting the model to a much larger and more diverse dataset. We utilize high-quality data from NOAA’s recent WCOA Cruise, along with NOAA’s 2012 GOMMECC-2 Cruise. An algorithm is also being developed to allow saturation state predictions for in situ temperature, salinity, and pressure conditions. These results will enhance our capacity to measure carbonate ion concentration in seawater and to make accurate predictions of aragonite and calcite saturation states.

Authors

Sharp, J. D., University of South Florida College of Marine Science, USA, jdsharp@mail.usf.edu

Byrne, R. H., University of South Florida College of Marine Science, USA, rhbyrne@usf.edu

Liu, X., University of South Florida College of Marine Science, USA, xwliu@mail.usf.edu

Feely, R. A., NOAA Pacific Marine Environmental Laboratory, USA, richard.a.feely@noaa.gov

Details

Poster presentation

Session #:056
Date: 03/01/2017
Time: 11:00 - 12:00
Location: Poster/Exhibit Hall

Presentation is given by student: Yes

PosterID: 467