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Technical Reports of the Meteorological Research Institute

No. 57

Precise Spectrophotometric Measurement of Seawater pH_T with an Automated Apparatus using a Flow Cell in a Closed Circuit

Shu SAITO, Masao ISHII, Takashi MIDORIKAWA and Hisayuki Y. INOUE


December 2008
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	Preface
	Abstract
	Contents
1	Introduction
2	Methods and materials
2.1	Principles
2.2	Apparatus
2.3	Preparation of dye solution
2.4	Perturbation caused by addition of dye solution
2.5	Correction for temperature deviations
2.6	Seawater samples
2.7	Certified reference materials (CRMs) and working standards
3	Onboard measurements
4	Measurements of bottle samples taken at depth
4.1	Effects of bottling and headspace
4.2	Perturbation of pHT caused by addition of saturated HgCl2 solution
4.3	Storage of samples
4.4	Uncertainty in pHT measurements of bottle samples
5	Consistency of measured and calculated pHT values for CRMs and comparability of pHT data among several cruises
6	Procedure to measure pHT with high comparability and precision
7	Discussion
7.1	Standard deviation of pHT in reference materials
7.2	Origin of the pHT perturbation caused by the addition of HgCl2
7.3	Internal consistency of CO2 system parameters
8	Summary
	Acknowledgements
	References