The carbonate system in hypersaline solutions: dead sea brines |
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| Authors: | Eytan Sass Sam Ben-Yaakov |
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| Institution: | 1. Department of Geology, The Hebrew University, Jerusalem Israel;2. Department of Electrical Engineering, Ben-Gurion University of the Negev, Beer-Sheva Israel |
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| Abstract: | 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. |
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