© 1985 IUPAC The physical chemistry of natural waters

Abstract- Ionic interactions have been shown to affect the thermodynamic and transport properties of natural waters as well as bio- and geo-chemical processes taking place in these waters. The ionic interaction models used to account for these interactions have been examined. Simple additivity models are used to estimate the density and sound speed of the mixtures of sea salts and seawater. The estimated values are shown to be in good agreement with the measured values. The ion pairing and specific interaction models are used to estimate the activity coefficients of ions in seawater and brines. The results are shown to be in good agreement with measured values. The estimated activity coefficients are shown to yield reliable values of the pK for the ionization of acids. INTRODUCT ION A knowledge of ionic interactions is necessary to understand the chemical processes that occur in natural waters such as rivers, lakes, estuaries, seas and ocean waters. Short range ion-water and ion-ion interactions have been shown to affect equilibria processe