The carbonate system in hypersaline solutions: dead sea brines

Eytan Sass, Sam Ben-Yaakov

Research output: Contribution to journalArticlepeer-review

79 Scopus citations


Various investigators reported a decrease in pH as seawater is concentrated. A similar phenomenon was reported for Dead Sea waters which are about ten times more saline than seawater. The reasons for the low pH values of Dead Sea waters (pH 5.9-6.5), which precipitate CaCO3, were investigated by determining the apparent dissociation constants of carbonic acid in these brines. A new method, based on alkalinity titration and least-squares fitting, was used to estimate the proton activity coefficient (γH+) and the first and second dissociation constants of carbonic acid (K1′, K2′) in natural and artificial Dead Sea waters. It was found that as the salt content increases, pK′1 and pK′2 values progressively decrease whereas γH+ sharply increase. At the highest salinity investigated (TDS = 330 gl-1) γH+ pK′1 and pK′2 values are 24.5, 5.09 and 6.23, respectively, as compared to about 0.8, 5.9, 9.1 respectively for normal seawater (19‰ chlorinity) at the same temperature (30°C). The implication of the results of this study regarding solubility of CaCO3 and the general behavior of the carbonate system in hypersaline solutions is discussed.

Original languageEnglish
Pages (from-to)183-199
Number of pages17
JournalMarine Chemistry
Issue number2
StatePublished - 1 Jan 1977

ASJC Scopus subject areas

  • Oceanography
  • General Chemistry
  • Environmental Chemistry
  • Water Science and Technology


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