Improvements in potentiometric determinations of the CO2 oceanic system using seawater sub-standards and CO2 reference materials

• Published in: Ciencias Marinas
• Main Authors: AF Ríos, FF Pérez
• Format: Article in Journal/Newspaper
• Language: English; Spanish
• Published: Universidad Autónoma de Baja California 1999
• Subjects: pH; alkalinity; potentiometry; seawater; carbon dioxide; Biology (General); QH301-705.5; North Atlantic Deep Water; North Atlantic
• Online Access: https://doi.org/10.7773/cm.v25i1.656; https://doaj.org/article/386be38fd5994a7cbb821e8bc6c8358a

During the Cither 3 cruise along WOCE section A14, where 107 full-water column stations were surveyed, pH and alkalinity were measured potentiometrically. Corrections carried out on the raw data set have allowed us to improve the data quality. The correction procedure was focused on monitoring: (i) calibrations, (ii) liquid junction potential and (iii) seawater sub-standards; CO2 reference material (CRM) has been used to check this procedure. Accuracy of pH15 measurements (NBS scale) and alkalinity was 0.004 and 1.4 µmol.kg–1, respectively. Certified total inorganic carbon on CRM, batch 24, is 1987.55 µmol.kg–1. A value of 1987.8 ± 2.2 µmol.kg–1 was obtained following the correction procedure. This improvement was independently verified by means of the covariances between nitrate and pH, and between silicate and normalized alkalinity in North Atlantic Deep Water.