Abstract
Short-range ion-water and ion-ion interactions have been shown to affect equilibrium processes (acid-base, solubility, oxidation-reductions) as well as the physical-chemical properties of natural waters. As ionic interactions affect the state of metal ions, it has been suggested by many workers that biological toxicity and availability are affected by ionic interactions. Recent work has also shown that ionic interactions can affect the rates of chemical processes in natural waters. In the present paper I will review the recent marine solution chemistry studies using models to understand processes occurring in natural waters. The two most popular models for ionic interactions are the ion pairing speciation model and the Pitzer specific interaction model. Both have their utility and a combination of the two will be the best model for the future. In our recent studies we have examined how ionic interactions affect the rates of oxidation of metals and nonmetals in seawater. The effects of the major cations and anions of seawater have been shown to increase or decrease the oxidation rates. The interactions of Cu(I) with Cl
− cause the rates to decrease, whereas the interactions of Fe(II) with OH
− cause the rates to increase. An increase in pH can increase the oxidation rates of H
2S and decrease the oxidation of SO
2. These increases and decreases in reaction rates are related to changes in the rates for various forms of the reactants in solution. By using ionic interaction models one can account for the changes in the rates caused by changes in the composition of natural waters.
