Carbonate constants for estuarine waters

Frank J. Millero

Research output: Contribution to journalArticlepeer-review

177 Scopus citations


Intensive studies have been made on the carbonate system in seawater. The thermodynamic constants needed to examine the components of the carbonate system have been developed by several authors. The thermodynamic constants for the dissociation of carbonic acid in seawater have been determined on different pH scales. The two most popular pH scales are the total scale: [H+] T ≤ [H+]F{1 + [SO4 2]T/KHSO4}) and the seawater scale: [H +]SWS ≤ [H+]F {1 + HSO4[SO42]T/KHSO4 + HF[F-]T/KHF}, where the brackets denote concentrations and the subscripts F and T are for free and total concentrations. The values of KHSO4 and KHF are the dissociation constants for HSO4- and HF: As long as the same pH scale and constants for seawater are used, one can evaluate the components of the carbonate system in seawater. Unfortunately, not all the measured and fitted constants have been made for dilute seawater, and thus cannot be used in estuarine waters. In this paper, the measured constants from S ≤ 1 to 50 and t ≤ 0 to 50C have been determined on the total, seawater and free scale (pHF ≤ log[H+]F). These stoichiometric constants can now be used to examine the carbonate system in most estuarine waters.

Original languageEnglish (US)
Pages (from-to)139-142
Number of pages4
JournalMarine and Freshwater Research
Issue number2
StatePublished - 2010


  • PH
  • Scales
  • Seawater

ASJC Scopus subject areas

  • Oceanography
  • Ecology, Evolution, Behavior and Systematics
  • Aquatic Science
  • Ecology


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