Abstract
We have developed new systems capable of profiling to >1000 m for measuring in situ pH and fugacity of CO2 (fCO2) in the ocean using spectrophotometric analysis (pH and CO2 profilers). The in situ pH is determined by detecting the color change of the pH indicator (m-cresol purple). It can withstand ambient pressure to 1000 m depth. The CO2 profiler analyzed in situ fCO2 by detecting the change of pH in an inner solution, equilibrated with the seawater through a gas permeable membrane. It can be operated to 2500 m depth. We used an amorphous fluoropolymer tubing form of AF-2400 for the gas permeable membrane due to its high gas permeability coefficients. The inner solution was a mixture of 2 μM bromocresol purple (BCP) and 5 μM sodium hydroxide. This system gave us a response time of 1 minute, which is twice as fast as previous systems. The precisions of pH and CO2 profilers were within 0.002 and 2.5% respectively. We have used these profilers to study the North Pacific, obtaining good agreement with the difference between the data from profilers and a discrete bottle of 0.002 ± 0.005 pH (SE, n = 25) and −0.4 ± 3 μatm (SE, n = 31).
Similar content being viewed by others
References
Bates, N. R., L. Samuels and L. Merlivat (2001): Biogeochemical and physical factors influencing seawater fCO2 and air-sea CO2 exchange on the Bermuda coral reef. Limnol. Oceanogr., 46, 833–846.
Bris, L. N., P. M. Sarradin and S. Pennec (2001): A new deep-sea probe for in situ pH measurement in the environment of hydrothermal vent biological communities. Deep-Sea Res. I, 48, 1941–1951.
Byrne, R. H. and J. A. Breland (1989): High precision multiwavelength pH determinations in seawater using cresol red. Deep-Sea Res., 36, 803–810.
Byrne, R. H., X. Liu, E. A. Kaltenbacher and K. Sell (2002): Spectrophotometric measurement of total inorganic carbon in aqueous solutions using a liquid core waveguide. Anal. Chim. Acta, 451, 221–229.
Cai, W. and C. E. Reimers (1993): The development of pH and pCO2 microelectrodes for studying the carbonate chemistry of pore waters near the sediment-water interface. Limnol. Oceanogr., 38, 1762–1773.
Clayton, T. D. and R. H. Byrne (1993): Spectrophotometric seawater pH measurements: total hydrogen ion concentration scale calibration of m-cresol purple and at-sea results. Deep-Sea Res. I, 40, 2115–2129.
Culberson, C., R. M. Pytkowitcz and J. E. Hawley (1970): Seawater alkalinity determination by the pH method. J. Mar. Res., 28, 15–21.
DeGrandpre, M. D., T. R. Hammar, S. P. Smith and F. L. Sayles (1995): In situ measurements of seawater pCO2. Limnol. Oceanogr., 40, 1152–1159.
DeGrandpre, M. D., M. B. Matthew and T. R. Hammar (1999): Calibration-free optical chemical sensors. Anal. Chem., 71, 1152–1159.
DelValls, T. A. and A. G. Dickson (1998): The pH of buffers based on 2-amino-2-hydroxymethyl-1,3-propanediol (’tris’) in synthetic seawater. Deep-Sea Res. I, 45, 1541–1554.
Dickson, A. G. (1993): The measurement of sea water pH. Mar. Chem., 44, 131–142.
Dickson, A. G. and F. J. Millero (1987): A comparison of the equilibrium constants for the dissociation of carbonic acid in seawater media. Deep-Sea Res., 34, 1733–1743.
DOE edited by Dickson, A. G. and C. Goyet (1994): DOE: Handbook of Methods for the Analysis of the Various Parameters of the Carbon Dioxide System in Sea Water, Ver. 2, ORNL/CDIAC-74.
IPCC, 2001. Climate Change (2001): The scientific basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change, http://www.ipcc.ch/
IRI/LDEO, Climate Data Library (2000): GEOSECS: Geochemical Ocean Sections Study, a global survey of the three-dimensional distribution of chemical, isotopic, and radiochemical tracers in the ocean, http://ingrid.ldgo.columbia.edu/SOURCES/.GEOSECS/
Lewis, E. and D. W. R. Wallace (1998): Program developed for CO2 system calculations. ORNL/CDIAC-105, Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, US Department of Energy, Oak Ridge, TN.
Maberly, S. C. (1996): Diel, episodic and seasonal changes in pH and concentrations of inorganic carbon in a productive lake. Freshwater Biol., 35, 579–598.
Martz, T. R., J. J. Carr, C. R. French and M. D. DeGrandpre (2003): A submersible autonomous sensor for spectrophotometric pH measurements of natural waters. Anal. Chem., 75, 1844–1850.
Merlivat, L. and P. Brault (1995): CARIOCA buoy: carbon dioxide monitor. Sea Technol., 10, 23–30.
Millero, F. J. (1995): Thermodynamics of the carbon dioxide system in the oceans. Geochim. Cosmochim. Acta, 59, 661–677.
Mook, W. G. and B. K. S. Koene (1975): Chemistry of dissolved inorganic carbon in estuarine and coastal brackish waters. Estuar. Coast. Mar. Sci., 3, 325–336.
Ono, T., S. Watanabe, K. Okuda and M. Fukasawa (1998): Distribution of total carbonate and related properties in the North Pacific along 30°N. J. Geophys. Res., 103, 30873–30883.
Ono, T., Y. W. Watanabe and S. Watanabe (2000): Recent increase of DIC in the western North Pacific. Mar. Chem., 72, 317–328.
Tabacco, M. B., M. Uttamlal, M. McAllister and D. R. Walt (1999): An autonomous sensor and telemetry system for low-level pCO2 measurements in seawater. Anal. Chem., 71, 154–161.
Tsunogai, S., T. Ono and S. Watanabe (1993): Increase in the total carbonate in the western North Pacific water and a hypothesis on the missing sink of anthropogenic carbon. J. Oceanogr., 49, 305–315.
Tsurushima, N., Y. Nojiri, K. Imai and S. Watanabe (2002): Seasonal variations of carbon dioxide system and nutrients in the surface mixed layer at station KNOT (44°N, 155°E) in the subarctic western North Pacific. Deep-Sea Res. II, 49, 5377–5394.
Wakita, M., S. Watanabe, Y. W. Watanabe, T. Ono, N. Tsurushima and S. Tsunogai (2005): Temporal change of dissolved inorganic carbon in the subsurface water at station KNOT (44°N, 155°E) in the western North Pacific subpolar region. J. Oceanogr., 61, 129–139.
Wang, Z. A., W.-J. Caia, Y. Wanga and B. L. Upchurch (2003): A long pathlength liquid-core waveguide sensor for real-time pCO2 measurements at sea. Mar. Chem., 84, 73–84.
Watanabe, Y. W., T. Ono and A. Shimamoto (2000): Increase in the uptake rate of oceanic anthropogenic carbon in the North Pacific determined by CFC ages. Mar. Chem., 72, 297–315.
Weiss, R. F. (1974): Carbon dioxide in water and seawater: The solubility of a non-ideal gas. Mar. Chem., 2, 203–215.
Winn, C. D., Y.-H. Li, F. Mackenzie and D. M. Karl (1998): Rising surface ocean dissolved inorganic carbon at the Hawaii Ocean Time-series site. Mar. Chem., 60, 33–47.
WOCE Hydrographic Program Office (WHPO) (2002): WHPO one-time survey. http://whpo.ucsd.edu/onetime.htm
Yao, W. and R. H. Byrne (2001): Spectrophotometric determination of freshwater pH using bromocresol purple and phenol red. Environ. Sci. Technol., 35, 1197–1201.
Zhang, H. and R. H. Byrne (1996): Spectrophotometric pH measurements of surface seawater at in-situ conditions: absorbance and protonation behavior of thymol blue. Mar. Chem., 52, 17–25.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Nakano, Y., Kimoto, H., Watanabe, S. et al. Simultaneous vertical measurements of in situ pH and CO2 in the sea using spectrophotometric profilers. J Oceanogr 62, 71–81 (2006). https://doi.org/10.1007/s10872-006-0033-y
Received:
Revised:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/s10872-006-0033-y