A decade of spectrophotometric carbonate ion measurements in seawater dealing with inconsistencies

• Main Authors: Fernández-Guallart, E., Fajar, Noelia, Castaño, Mónica, Santiago, Rocío, El Rahman Hassoun, Abed, Pérez, Fiz F., Easley, Regina, Álvarez, Marta
• Format: Conference Object
• Language: English
• Published: 2021
• Subjects: Ocean acidification
• Online Access: http://hdl.handle.net/10261/260131

ASLO 2021 Aquatic Sciences Meeting, 22–27 June, Virtual The spectrophotometric methodology to determine carbonate ion concentration in seawater was first published in 2008 and has been continuously evolving in terms of reagents and formulations. Although being fast, relatively simple and affordable, it is not widely used in the ocean acidification community neither in time-series observations nor for experimentation. This study uses a merged dataset, from 2009 to 2020, with overdetermined CO2 measurements to assess the evolution of the methodology for carbonate ion determination through CO2 system internal consistency analysis and discussion of uncertainty sources. Overall results show that the inconsistencies observed compromise the consistency of datasets between regions and throughout time, pointing to the need for a validated standard operational procedure similar to those proposed for the other CO2 parameters No