Study of Ionic Interactions in Seawater

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Work is underway to examine how ionic interactions affect the rates of oxidation and reduction of metals and nonmetals in seawater. Measurements of the rates are being made in seawater as a function of pH, salinity, temperature and composition to elucidate the effect of the ionic components of seawater. Studies of the products and intermediates of the reactions will be made (when possible) in an attempt to elucidate the mechanisms of the reactions. Measurements are continuing on the oxidation of H2S with the oxides of Fe(III) and Mn(IV) in seawater as a function of pH, temperature, and salinity. The disappearance of H2S and the appearance of Mn(II) and Fe(II) are being measured. The effect of pH, temperature and salinity on S, HSn, SO32, and S2O32 is being studied The research includes completion of studies on the reduction of Cr(VI) with H2S and the reduction of Cu(II) with H2O2 in natural waters. Measurements of the stability constants of metals with HS will be continued using a square wave polarographic technique developed by Luther (Univ. of Delaware) that senses free HS at nM levels. New thermodynamic modelling will be carried out on the speciation of divalent and trivalent metals, the carbonate system and the state of Fe(II) and Fe(III) in seawater. These studies will hopefully lead to a consistent set of stability constants and Pitzer interaction parameters that can be used to characterize these systems in natural waters.